A 617627
A
MANUAL
OF
PHOTOGRAPHY
A. BROTHERS
F.R.A.S.
TR
145
1387
C.GRIFFIN CO
"|

}
ARTES
1817
SCIENTIA
VERITAS
LIBRARY
OF THE
UNIVERSITY OF MICHIGAN
TUEBOR
(QUÆRIS PENINSULAM AMⱭNAM.
CIRCUMSPICE
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PHOTOGRAPHY
TR
14.5
.387

جا ا ا ن
OF
M
CH.
J. Gale, Photo.
Village News.
Dawsons Pb So.
(By kind permission of J. Gale. Esq;

Sus
PHOTOGRAPHY:
ITS HISTORY, PROCESSES, APPARATUS,
AND MATERIALS.
COMPRISING
WORKING DETAILS OF ALL THE MORE IMPORTANT
METHODS.
bied
BY
A. BROTHERS, F.R.A.S.
WITH PLATES BY MANY OF THE PROCESSES DESCRIBED,
AND ILLUSTRATIONS IN THE TEXT.
LONDON:
CHARLES GRIFFIN AND COMPANY, LIMITED,
EXETER STREET, STRAND.
[All rights reserved.]
1892.
ΤΟ
HENRY WILDE, Esq., F.R.S.,
AS
A SLIGHT MARK OF THE ESTEEM IN WHICH HE IS HELD
BY
THE AUTHOR.
Re. ej
भ
6044
Lowe
9-12-44
50660
PREFACE.
IN the preparation of the following work, my aim has been to
produce a Handbook for the use of Students of Photography,
which should both give the results of practical experience,
and include—as far as possible within a moderate compass-
information gathered from many sources, and not readily
accessible.
The newer methods have been dealt with in sufficient
detail, but I have also throughout given special attention to
the processes in use prior to the introduction of the gelatino-
bromide method. Some of these processes are in danger of
being neglected through the facilities which the newer methods
have introduced. But, as I have shown, the new processes do
not give results equal to the old, and are totally unsuitable
for some purposes-such as for making negatives for photo-
lithography, and in various other ways.
To these older processes, therefore, I have given such pro-
minence as their practical usefulness demands.
Where practicable, the plates illustrate the processes de-
scribed, and these plates make the work distinctly more
serviceable to students.
To those who have rendered aid in
this respect, the Publishers, with myself, desire to offer the
fullest acknowledgment.
Our thanks are particularly due to
vii
viii
PREFACE.
Messrs. Billing, Son, & Co., Mr. Brennan, Messrs. Boussod,
Valadon, & Co., Mr. Chapman, Messrs. A. & C. Dawson, Mr.
J. H. T. Ellerbeck, Mr. Gale, Mr. G. J. Johnson, the Meisen-
bach Company, Messrs. Norbury & Sons, Mr. H. P. Robinson,
Miss E. G. Thomson, Messrs. Thornton & Pickard, Messrs.
Waterlow & Sons, Mr. Wolfe—and to these I would add the
name of my son, Mr. H. E. Brothers, B.Sc. (Lond.), who revised
Chapters II. and III. in Part I.
裝
​MANCHESTER, April 1892.
A. BROTHERS.
GENERAL CONTENTS.
HISTORICAL SKETCH
Niépce
Daguerre
•
PART I.-INTRODUCTORY.
CHAPTER I.
PAGE
I Talbot
2
•
CHEMISTRY OF PHOTOGRAPHY
Physical action
Chemical action.
•
CHAPTER II.
Oxidation by light
Reduction by light
Theory of sensitisers
Orthochromatic photography
OPTICS OF PHOTOGRAPHY
Light.
Lenses
Focus.
•
•
PAGE
·
I-17
7
17–36
18 Solarisation
25
18
Developing.
27
19
Restrainers and accelerators
30
20
Intensifying
31
22
Printing
33
24
Use of iron salts.
34
CHAPTER III.
36-55
36
39
Defects in lenses
Objectives.
44
49
4I
CHAPTER IV.
LIGHT IN PHOTOGRAPHY
55-66
Electric light
55
Compressed gas
62
Oxyhydrogen light
61
Ethoxo-limelight
63
Continuing action of light.
62
Magnesium light
63
Alabastrine process
Albumen process
Albumen substratum
Amphitype.
PART II.—PRocesses.
67
68
Aniline process
Aristotype
71
•
71
69 Autotype
•
72
70
Beechey's emulsion process.
•
75
ix
X
GENERAL CONTENTS
PAGE
Bitumen process
Black lines.
76
77
Bromide printing process
78
Calotype
Canvas, printing on
80
81
Carbon printing .
83
Celerotype
·
84
Ceramic photographs
86
Chloro-bromide process
87
Magic photographs
Meisenbach process
Micro-photography
Mounting and mountants
Obernetter's etching process
Opal glass.
Orthochromatic photography
Panoramic photography
Paper negatives .
PAGE
128
128
•
•
129
•
•
129
131
131
•
132
•
138
•
139
Chromatype
87
Pedestal portraits
•
139
Cleaning glass
87
Clearing and reducing solutions
Coffee process
Collodio-albumen process
Collodio-bromide process
888888
89
90
Collodio-chloride of silver pro-
cess
90
Collodion pellicle
*
90
Collodion process
91
Collotype
•
Colouring lantern-slides
98
•
104
Contretype negative
104
Photochrome-lithography
Photo-engraving-photogravure.
Photo-filigrane
Photochromo-typography
Photogenic drawing
Photographing on wood
Photography and colour
Photo-lithography
Photo-micrography
Phototint
Photo-typography
Pinhole photography
139
140
·
•
144
144
•
144
•
145
·
146
·
152
•
159
162
•
·
162
•
162
Crystal cubes
104
Platinotype process
163
Cyanotype.
105
Plumbago process
172
Daguerreotype process
106
Primuline or diazotype process
•
173
Drying gelatine plates
108
Printing and toning
•
175
Dry-plate making
109
Printing on ivory
183
Dry processes
109
Reproduced negatives.
183
Dusting-on process
IIO
Reversal of the image.
·
184
Fixing
Eburneum process
Electro-phototypy
Enamelling paper prints
Enlarging and copying
Ferrotype
Ferrotypes.
Film photography
Fluorotype.
IIO
•
III
Reversed negatives
Retouching.
185
187
III
Ruby medium
·
189
•
I 12
Screen-plates
189
115
114
Stains.
I
115
•
115
116
Tannin process
Gelatino-bromide process
116
Heliography
Gelatino-chloride paper
Gold-printing process.
Green photographs
Gum-gallic process
Indian-ink outlines
Iridescent photographs
Kallitype
Kennett's pellicle
Lantern-slide making.
Leimtype
•
Litho-heliogravure
119
Tea process
120
121
•
121
I2I
I2I
122
I22
Silvering glass
Stannotype
Steel-facing copper-plates
Taupenot process
Telescopic photography
Transferotype process
Typogravure
Uranium printing
Vignetting.
Waxed-paper process
Woodbury-type
189
•
190
•
191
192
•
193
193
194
194
•
197
197
198
199
200
•
200
•
•
►
125
Woodbury gravure
201
•
125
Writing titles
202
·
127
Yellow negatives
202
•
127
Zinc-etching
'202
GENERAL CONTENTS.
xi
•
•
PART III.-APPARATUS.
PAGE
Actinometers and exposure tables 205
Balance
Baths and dippers
Bellows
Buckle's brush
•
Burnishers and rolling machines
Cameras
Lamps for dark rooms
Level-indicator
Optical or magic lantern
PAGE
237
208
•
237
208
•
238
209
209
Oscillating tables or rockers
Pantascopic camera
•
242
•
242
210
Photometers
243
210
Plate-boxes
•
243
Camera-stands and tripods
226
Plate-racks
•
243
Condenser .
227
Pneumatic plate-holder
•
243
Dark room .
227
Printing-frames
•
244
•
Diaphragms and stops
227
Retouching desk
245
Dishes and trays
229
Roller-slide
•
245
Dropping bottles
229
Sky-shade
•
245
Focussing and focimeter
·
229
Solar camera
245
Focussing cloth
·
230
Squeegee
246
Focussing glass
231
Stoppers
•
246
Focussing screen
231
Tents.
•
247
Head-rests.
232
Thermometers
247
Hydrometer
232
Instantaneous shutters
232
Trimming prints
View-finder
•
248
248
Iris diaphragm
•
236
Washing apparatus
•
248
PART IV.-MATERIALS USED IN PHOTOGRAPHY.
Acetic acid.
251 Celloidin
•
Acids.
Albumen
•
251
Cellulose
•
258
258
251
Chloride of lime
•
258
Alcohol
Albumenised paper
Alpha paper
252
Chloroform.
•
•
253
Chlorophyll
258
258
254
Chromate of silver
•
258
Aluminium
Amber
Ammonia
Ammonium compounds
Anglol
Aniline
254
Chromium-potassium sulphate
•
259
•
254
Citric acid.
259
254
Collodion
•
259
255
Copper
260
■
256
Copper sulphate.
260
·
·
256
Dextrin
260
•
Animal charcoal.
256
Eau de Javelle
260
•
Aqua regia.
256
Ebonite
261
•
Aurin or corallin
257
Eikonogen
261
•
•
Barium compounds
257
Emery
262
·
Benzene
257
Encaustic paste
262
Benzolene
257
Eosin.
262
Bitumen
Borax.
Bromine
Cadmium compounds
Calcium chloride
Canada balsam
·
257
Erythrosin
262
•
•
257
Ether.
262
257
Ferric compounds
262
•
•
257
Ferrous oxalate
262
•
•
257
Fluoresceïn
263
•
•
258
Formic acid
263
xii
GENERAL CONTENTS.
Gallic acid.
Gelatine
Glass.
Glucose
Glycerine
Gold, chloride
Ground glass
Gum arabic
Gum dammar
Gutta-percha
Hydrochloric acid
Hydrofluoric acid
Hydrogen dioxide
Hydroquinone
Hydroxylamine
Hypo" eliminators
India-rubber
Iodine
Iron
•
Isinglass
•
PAGE
•
263
263
264
Methylated spirit
Mounts
Paraphenylene-diamine
Potassium compounds
Pyrocatechin
Pyrogallol.
•
Nitric acid.
264
ན
Oxalic acid.
·
264
Ox-gall
265
Palladium
265
Paper.
266
•
266
Platinum
266
Poisons
·
266
266
•
267
•
267
Pyroxylin
269
Ready sensitised paper
269
Rodinal
·
270
Sandarac
270
Shellac
271
Silver and silver compounds
271
Sodium compounds
•
Jena glass
271
Starch
Kaolin
271
Strontium chloride
Lavender oil
271
Sulphuric acid
►
Lead.
272
Tannic acid
Lead nitrate
272
Turpentine.
►
Lithium chloride
•
272
Uranium
Litmus
Magnesium
Mastic
Mercuric chloride
Mercury
Meta-gelatine
•
272
Uranium nitrate.
272
Varnish
•
272
Water
•
272
Wax
•
•
273
Zinc
·
273
PAGE
273
•
274
274
274
275
•
275
275
276
•
276
R
276
277
278
279
279
281
282
*
282
282
283
284
•
•
290
•
290
•
290
•
290
291
291
291
291
•
292
293
293
APPLICATIONS OF PHOTOGRAPHY
Architectural photography.
Astronomical photography.
Cameo
Carte de visite
Clouds
Composite portraits
Composition
Distance
Interiors
糖
​PART V.
CHAPTER I.
294-321
•
294
Impressionism in photography
•
302
•
294
Landscape photography
303
298
Muybridge's photographs
•
305
299
Photo-meteorology
•
305
299
Portraiture.
•
305
300
Rembrandt portraits
•
•
309
•
300
Spectroscope in photography
309
•
300
Stereoscope.
310
301
GENERAL CONTENTS.
xiii
CHAPTER II.
PRACTICAL HINTS
Accelerator
PAGE
321-354
PAGE
321
Frilling
•
334
Alkaline development
321
Halation
334
Anhydrous.
·
321
Argentometer
•
321
Backing plates
322
High lights.
Hygiene in photography
Intensifying
•
· 335
•
Bichromate and cyanide poisoning 322
Mealiness
Broken negatives
322
Negatives
·
· 335
335
338
338
Combination printing.
323
Over-exposure
338
Copyright
•
324
Pinholes
339
Cracks
324
Positive
•
340
Density
•
325
Reduction of density
•
340
Detail.
·
325
Reflected light .
341
Developing and developers.
·
325
Residues
341
Dialysis
331
Saturated solution
343
Diffused light
331
Sizes of drops
·
345
Dust
•
331
Specific gravities
345
Expansion of paper
•
332
Studios
346
Fog
332
Symbols
•
347
Freezing mixtures
་
333
Weights and measures
348
INDEX
355
LIST OF PLATES.
I.
Village News
PAGE
Frontispiece
2. Collotype by Waterlow & Sons
3. Chromo-collotype by Waterlow & Sons.
4. Indian-ink outlines-" Manchester Royal Exchange "
5. Meisenbach process-"Landscape "
6. Chromo-lithograph by Norbury & Sons.
. facing 98
104
122
128
between 138 and 139
>>
""
139
138
• facing 140
7. Photochromo-lithograph copy, reduced by photography
8. Photogravure-"En Penitence"-by Boussod, Valadon, & Co.
9. Pretsch process-" Clewer Churchyard"-by A. & C. Dawson
10. Photochromo-typography illustration by Boussod, Valadon, & Co.
II. Photo-lithograph-"Irish Lace "--by West, Newman, & Co.
12. Photo-lithograph-" Lace Curtain"-by A. Brothers & Co..
13. Photo-lithograph, original design by Miss E. G. Thomson
14. Microscopic object-"Diatoms and Caterpillar of Moth "-repro-
duced in collotype by M. Billing, Son, & Co.
15. Microscopic object-" Section of Optic Nerve "-showing healthy
and diseased parts, reproduced in collotype by L. Danielsson
16. Zinc-etching-"The Oldest House in Pennsylvania,"
1681 at Berwyn. Plate by Wolfe
17. Typogravure, illustration by Boussod, Valadon, & Co. .
18. Woodbury-type, from negative by F. C. Brennan
19. Photo-relief printing-block-"Hogarth's House'
20. Copying and enlarging camera
21. Instantaneous photograph-"Lord of the Isles
143
144
.
>>
152
27
156
""
158
160
•
162
Built in
189
198
201
""
202
""
224
233
298
305
55
324
22. Woodbury-gravure-Rutherfurd's "Photograph of the Moon
23. Landscape photography-Ellerbeck's "View in Norway"
24. Composition photograph-Robinson's picture, "A Strange Fish'
}
!
MANUAL OF PHOTOGRAPHY.
PART I.
INTRODUCTORY.
CHAPTER I.
HISTORICAL SKETCH.
EARLY in the present century, the idea that light could be made to
impress images produced by itself on paper and other material made
sensitive by chemical means, appears first to have been thought of,
and to have been put to practical test. All that was known until
1834 has comparatively little interest, if we except what was done
by Niépce. The fact that the substance called horn silver turned
black when exposed to daylight was known to some of the alchemists;
but it was the chemist Scheele who, in 1777, first investigated the
action of light on compounds of silver. Next, we have the fact that
Wedgwood and Davy, in the first years of this century, made prints
on paper and white leather by means of silver salts. The importance
of these early experiments does not appear to have occurred to those
who made them, probably from the fact that the pictures so produced
could only be examined in feeble light, as they were not fixed or
made permanent; and, at that time only such objects as were capable
of being printed by their own shadows, or could be placed directly
on the paper or leather could be photographed, the parts darkened by
the sun giving a negative impression of their forms.
In the experiments of M. Niépce of Chalons (1814) we have
another substance introduced, bitumen of Judea; and although he
did not use salts of silver, he may be said to have experimented in
the direction which led to most valuable discoveries, as, in the pre-
sent day bitumen is utilised in various ways. Niépce seems to have
used the camera obscura, the invention of Baptista Porta, who was
A
2
MANUAL OF PHOTOGRAPHY.
born at Naples in 1538. The bitumen, as employed by Niépce, was
spread on metal plates, and exposed in the camera much in the same
way as we now expose our more sensitive plates. It is the singular
property of bitumen that the parts which have been acted on by
daylight when exposed in the camera, or when placed under an object
in contact with it, become hardened, so that the solvents employed
to develop the picture will only affect those parts which have been
protected from the light, and this makes it valuable in photography.
The action of light on bitumen is, however, so very slow, that an
exposure of many hours is required to produce any result in the
camera.
By a
The wonderful beauty of the pictures formed by the camera lucida
and camera obscura appears to have suggested both to Daguerre and
Talbot the possibility, or at least the desirability, of discovering
some means by which the picture could be permanently fixed on
paper. Daguerre, as a painter of scenery for the diorama which he
opened in Paris in 1822, used the camera for sketching, and his
desire to utilise the picture as produced by light led to his introduc-
tion to Niépce. A partnership was the result (in 1829). After
trying the methods of Wedgwood, Davy, and Niépce, Daguerre used
plates of silver made sensitive to the action of light by the vapour of
iodine, but the picture was latent, or invisible to the eye.
fortunate accident, one of the plates which had been exposed to light
in the camera was placed in a cupboard to be cleaned off and used
again, the exposure not having been sufficient for Daguerre's purpose;
but he was surprised to find, some hours afterwards, that a perfect
picture had developed, and on a careful investigation it was found
that the result was caused by the vapour of mercury. Here, then,
was a most valuable discovery, the result of an accident," and the
process was at once of commercial as well as scientific importance.
The difficulty of "fixing" the picture remained. Sodium chloride
(common salt) was used for the purpose, but the discovery by Sir
John Herschel of the action of hyposulphite of soda on the salts of
silver enabled Daguerre's discovery to be made more complete. The
results of Herschel's experiments are referred to under the title
Sodium Thiosulphate.
Daguerre attempted to form a company to carry out his discovery;
but that failed. He, however, showed his pictures to M. Arago, who
brought the matter before the Academy of Sciences in Paris in 1839,
and with the immediate result that the French Government granted
Daguerre 6000 francs as a pension for life, and to Isidore Niépce.
(successor in the partnership to his father) a pension of 4000 francs,
on condition that the process should be published and not patented
a present to the whole civilised world. The process, however, was
HISTORICAL SKETCH.
3
patented in England, and large sums were paid for the right to use
it; as much as 1000 was paid for the exclusive rights in some large
towns.
Since the foregoing was written a manual or pamphlet by Daguerre
has come into the writer's hands. It was translated by Dr. Memes,
and published in 1839 by Messrs. Smith, Elder, & Co., of London.
The title is, "History and Practice of Photogenic Drawing on the
True Principles of the Daguerreotype, &c.," by L. J. M. Daguerre. Of
this little manual, consisting of about ninety pages, and six plates of
drawings of the apparatus used in the process, the translator says:
"In presenting this little work to the British public, the translator
may perhaps be permitted to observe of his original, that, in all the
circumstances, it is one of the most interesting works ever given to
the world. It is the first manual of a new science."
In this manual is given, first a series of plates with details of all
the apparatus necessary for producing the pictures on silver plates.
Next is given the "Bill for rewarding the authors" (Daguerre and
Niépce). This is followed by the speech by M. Duchâtel to the
Chamber of Deputies, describing the nature of the discovery, and
proposing the amount of the pensions. After this follows a most
interesting address to the Chamber by M. Arago, who gives a concise
history of the subject, beginning with the invention of the camera by
Porta. Amongst other matters in the eloquent address by M. Arago,
remarks occur on the cost of the material, which for the plates was
about three or four francs; if this amount appeared much, it is observed
that the same plate "is capable of receiving in succession a hundred
different designs ;" and following this is a remark by the translator
to the effect that a set of apparatus cost about £20-a sum which at
the present day seems little, when it is remembered that a small
camera alone might cost one-half the sum named. Arago's address
was delivered before one of the largest meetings of the Assembly ever
held, so great was the interest felt in the announcement of Daguerre's
discovery. The address is too long to be given in full here, but a few
extracts will convey a tolerable idea of its purport. The following
passages occur :—
"The daguerreotype, then, does not demand a single manipulation
which is not perfectly easy to every person. It requires no know-
ledge of drawing, and does not depend upon any manual dexterity.
By observing a few very simple directions, any one may succeed with
the same certainty and perform as well as the author of the inven-
tion. The promptitude of the method is perhaps that which has
most astonished the public. In reality, ten or twelve minutes in the
dull weather of winter are amply sufficient for taking a view of a
monument, a section of a town, or a landscape. In summer this time
4
MANUAL OF PHOTOGRAPHY.
may be reduced one-half. Under the skies of the South not more
than two or three minutes will be necessary.
"But it is of importance to remark that these ten or twelve minutes
in winter, these five or six minutes in summer, these two or three
minutes in southern regions, express merely the time during which
the plate of metal is exposed to the lenticular image. To this space
must be added the time of unpacking and adjusting the camera, the
time spent in preparing the plate, and the few minutes necessary for
the final operation of rendering the picture thus obtained insensible
to the future action of light. Added together, all these different
stages of the process may extend the whole period employed to thirty
minutes or three-quarters of an hour. Those persons are deceived,
then, who suppose that during a journey they may avail themselves
of brief intervals while the carriage slowly mounts a hill to take
views of a country."
This last paragraph has peculiar interest with reference to the faci-
lities now offered to the tourist, who can carry in his pockets all he
requires for taking half-a-dozen pictures, each of which would not
occupy more than a few moments!
Of the greatest interest is the following paragraph:-"Let us not
hesitate, then, to announce the fact the re-agents discovered by M.
Daguerre will speed onwards the progress of those sciences which
confer the highest honour on the human mind. By their aid the
philosopher will be enabled henceforth to proceed on the principle of
absolute intensities; he will compare lights by their effects. If he
find it useful, the same tablet will present him with the impression
of the dazzling beams of the sun, and with the pencillings of rays
three hundred thousand times fainter than those of the moon-the
rays of the stars."
At the end of his important address (the object of which, it
should be stated, was to recommend the Chamber of Deputies to
adopt unanimously the Bill for granting the annuities) Arago says:
"The importance of this latter engagement" (to make known all
future improvements) "will certainly not appear doubtful to any
person when we inform you, that a very slight advance beyond his
present progress will enable M. Daguerre to apply his processes to
executing portraits from life." So that at this date, 3rd July 1839,
the process was not adapted for portraiture; and although Arago
speaks of the "eagerness of foreign nations to lay hold of an erro-
neous date, of a doubtful fact, of the slightest pretext, in order to stir
up questions of priority for the purpose of adding to their own crown
of discovery the beautiful ornaments which the photographic inven-
tions will ever form" (of course alluding to Talbot's claim), it was
reserved for an Englishman to complete Daguerre's discovery, and
HISTORICAL SKETCH.
5
the name of John Frederick Goddard should ever be remembered in
connection with the daguerreotype process.
The commission of which Arago was the mouthpiece was composed
of MM. Arago, Etienne, Carl, Vatout, de Beaumont, Tournouër-
Delessort (François), Combarel de Leyval, and Vitet, all names dis-
tinguished in science.
The matter of the pensions was brought before the Chamber of
Peers on the 31st July 1839 by M. Gay-Lussac, who was one of the
commission, composed of the following peers:-Barons Athalin,
Besson, Gay-Lussac, the Marquis de Laplace, Vicomte Siméon, Baron
Thénard, and the Comte de Noé.
In his address, Gay-Lussac goes over very much the same ground
as that traversed by Arago, while urging Daguerre's claim for the
pension, and says: "The principal advantage of Daguerre's process.
consists in obtaining quickly, and yet with the utmost exactness, re-
presentations of objects, whether to preserve this identical image, or
to reproduce it by engraving or lithography. Hence it is conceived
that, limited to the possession of a single individual, an art like this
could not find sufficient exercise.
"On the contrary, given to the public, this process will receive in
the hands of the painter, architect, traveller, naturalist, innumerable
applications, all more or less useful to mankind. Lastly, as the secret
of an individual, the invention itself would long remain stationary,
and perhaps might retrograde; rendered public, it will be extended
and improved by a general emulation."
Viewed in the light of all that has passed connected with the art
of photography since the addresses by two of the most eminent
scientific men who ever lived were delivered, the words of Arago
and Gay-Lussac have the highest interest; and as the originals are
not generally available, the writer regrets that space prevents the
reproduction, entire, of the speeches from which these short extracts
have been made.
In the second chapter of his little pamphlet, Daguerre gives de-
scriptions of the discoveries of Niépce; in the third there is a
practical description of the daguerreotype; and in the concluding
chapter is described the method of dioramic painting.
To the enthusiast in photographic matters, this, the first of the
very large number of manuals devoted to the art, is of the greatest
possible interest, and it is scarcely equalled by the description which
Talbot has recorded of his own experiments.
The early daguerreotype pictures required very long exposures in
the camera, and for that reason portraiture was scarcely practicable.
Portraits, however, were taken, fifteen or twenty minutes in the
strongest light being necessary to obtain a picture. After the dis-
6
MANUAL OF PHOTOGRAPHY.
covery of the action of iodine on the silver plate and the effect of the
vapour of mercury in causing the image to develop, it only required
the great improvement introduced by the late Mr. J. F. Goddard in
1840 of the exposure of the iodised plate to the vapour of bromine,
to make Daguerre's discovery perfect. The effect of this discovery
was to reduce the time of exposure from twenty minutes to twenty
seconds, and a little later pictures could be taken in a small fraction
of a second. The image on the silvered plate is of a very delicate
character, and liable to injury by the tarnishing of the silver on
exposure to the air. This defect was lessened by "gilding" the
picture, as it was termed, by means of sel d'or. This process, how-
ever, although it added to the permanence of the picture, did not
entirely remove the defect, as the photographic image was easily
destroyed by the slightest friction, and the silver still in the course of
time became tarnished, unless carefully protected from the air. The
daguerreotype possesses one advantage over all other kinds of photo-
graph-the surface of the silvered plate, no matter how badly it may
be discoloured, the picture remains perfect beneath the tarnished film;
and on carefully removing the tarnish by chemical means, the picture
is restored to all its original beauty. Fine daguerreotypes are indeed
things of beauty," and since after fifty years many of those wonder-
ful pictures are as perfect as the day they were finished, we may
perhaps hope that some will remain "joys for ever." It is not too
much to say that no photograph can exceed in beauty a good
daguerreotype.
(C
Beautiful as is the daguerreotype, however, it has the disadvantage
of showing the picture reversed when taken direct in the camera, and
although this defect can be removed by the use of a reversing prism
or mirror, it was not always convenient to use the camera in that
way. There was yet another disadvantage, viz., the picture was a
positive, and could not be multiplied on paper. Great as these draw-
backs were, the process was very popular for many years, large prices,
from one to five or six guineas, being commonly charged for portraits ;
and when the work was of the best kind, the results were worth the
money paid, as it is very unlikely that the process will ever be re-
vived, and every year the old pictures become more valuable.
Concurrently with what has been said about Daguerre's process, it
is felt that Talbot's method should have been described; but there
1 In 1864 Mr. Talbot claimed that he first used potassium bromide in photo-
graphy; but as Hunt in his "Manual," 5th edition, 1857, states that Mr.
Goddard first used the vapour of bromine as early as 1839, and from other
evidence, it is clear that the only practical use of bromine in photography was
that referred to above, and that Mr. Goddard must at least be considered an
independent discoverer, as there is no doubt whatever that the daguerreotype
process owed its success to the application named.
HISTORICAL SKETCH.
7
cannot be much doubt that Niépce and Daguerre are entitled to the
claim of priority as discoverers. Daguerre was the inventor of an
excellent process; but Talbot's method, that is, the negative process,
and the consequent means of reproduction, has become of far greater
use, as it is practically Talbot's paper, prepared with silver chloride,
which is used so largely at the present time.
It has already been noticed that Daguerre used the camera obscura
-that is, a dark box in which the image is produced by the lens
placed at one end. The landscape or other object is seen on the
ground glass opposite the lens with all the colour of nature, and it
might occur to any one-how desirable a thing it would be to be able
to preserve the pictures depicted by the instrument.
This was
Daguerre's idea, which he realised by his method in all respects
excepting the colour. Such also was Talbot's thoughts as early as
1833, but he was using the camera lucida—both instruments give
similar results, but the cameras are used in different ways. In the
one case, the image is viewed in the box or on the surface placed to
receive it; but in the other, the image is viewed on a white or other
surface placed horizontally and without a dark box, and by careful
manipulation an outline of the picture viewed may be made with
considerable accuracy. Such was Talbot's method of sketching from
Nature.
The account of Talbot's discovery, as related by himself, is impor-
tant. It will be found in "The Pencil of Nature," published in
1844, and as the facts stated are valuable in the history of photo-
graphy, it may be appropriately introduced here. The experiments
referred to undoubtedly led to the first practicable method of photo-
graphy in this country.
Talbot says:
"One of the first days of the month of October 1833,
I was amusing myself on the lovely shores of the Lake of Como, in
Italy, taking sketches with Wollaston's camera lucida, or rather I
should say, attempting to take them; but with the smallest possible
amount of success. For when the eye was removed from the prism—
in which all looked beautiful-I found that the faithless pencil had
only left traces on the paper melancholy to behold.
"After various fruitless attempts, I laid aside the instrument, and
came to the conclusion, that its use required a previous knowledge of
drawing, which unfortunately I did not possess.
"I then thought of trying again a method which I had tried many
years before. This method was, to take a camera obscura, and to throw
the image of the objects on a piece of transparent tracing paper laid
on a pane of glass in the focus of the instrument. On this paper the
objects are distinctly seen, and can be traced on it with a pencil with
some degree of accuracy, though not without much time and trouble.
8
MANUAL OF PHOTOGRAPHY.
"I had tried this simple method during former visits to Italy in
1823 and 1824, but found it in practice somewhat difficult to manage,
because the pressure of the hand and pencil upon the paper tends to
shake and displace the instrument (insecurely fixed, in all probability,
while taking a hasty sketch by a roadside, or out of an inn-window);
and if the instrument is once deranged, it is most difficult to get it
back again, so as to point truly in its former direction.
"Besides which, there is another objection, namely, that it baffles
the skill and patience of the amateur to trace all the minute details
visible on the paper; so that, in fact, he carries away with him little
beyond a mere souvenir of the scene-which, however, certainly has
its value when looked back to in long after-years.
"Such, then, was the method which I proposed to try again, and
to endeavour, as before, to trace with my pencil the outlines of the
scenery depicted on the paper. And this led me to reflect on the
inimitable beauty of the pictures of Nature's painting which the glass
lens of the camera throws upon the paper in its focus-fairy pictures,
creations of a moment, and destined as rapidly to fade away.
"It was during these thoughts that the idea occurred to me
how charming it would be if it were possible to cause these natural
images to imprint themselves durably, and remain fixed upon the
paper !
"And why should it not be possible? I asked myself.
"The picture, divested of the ideas which accompany it, and con-
sidered only in its ultimate nature, is but a succession or variety of
stronger lights thrown upon one part of the paper, and of deeper
shadows on another. Now light, where it exists, can exert an action,
and, in certain circumstances, does exert one sufficient to cause changes
in material bodies. Suppose, then, such an action could be exerted
on the paper; and suppose the paper could be visibly changed by it.
In that case surely some effect must result having a general resem-
blance to the cause which produced it so that the variegated scene
of light and shade might leave its image or impression behind, stronger
or weaker on different parts of the paper according to the strength or
weakness of the light which had acted there.
"Such was the idea that came into my mind. Whether it had
ever occurred to me before amid floating philosophic visions, I know
not, though I rather think it must have done, because on this occasion
it struck me so forcibly. I was then a wanderer in classic Italy, and,
of course, unable to commence an inquiry of so much difficulty: but,
lest the thought should again escape me, between that time and my
return to England, I made a careful note of it in writing, and also of
such experiments as I thought would be most likely to realise it, if it
were possible.
HISTORICAL SKETCH.
9
'And since, according to chemical writers, the nitrate of silver is a
substance peculiarly sensitive to the action of light, I resolved to make
a trial of it, in the first instance, whenever occasion permitted on my
return to England.
But although I knew the fact from chemical books, that nitrate
of silver was changed or decomposed by light, still I had never seen
the experiment tried, and therefore I had no idea whether the action
was a rapid or a slow one; a point, however, of the utmost importance,
since, if it were a slow one, my theory might prove but a philosophic
dream.
Such were, as nearly as I can now remember, the reflections
which led me to the invention of this theory, and which first im-
pelled me to explore a path so deeply hidden among Nature's secrets.
And the numerous researches which were afterwards made-what-
ever success may be thought to have attended them-cannot, I
think, admit of a comparison with the value of the first and original
idea.
"In January 1834, I returned to England from my Continental
tour, and soon afterwards I determined to put my theories and specu-
lations to the test of experiment, and see whether they had any real
foundation.
CC
Accordingly I began by procuring a solution of nitrate of silver,
and with a brush spread some of it upon a sheet of paper, which was
afterwards dried. When this paper was exposed to the sunshine, I
was disappointed to find that the effect was very slowly produced in
comparison with what I had anticipated.
"I then tried the chloride of silver, freshly precipitated and spread
upon paper while moist. This was found no better than the other,
turning slowly to a darkish violet colour when exposed to the sun.
“Instead of taking the chloride already formed, and spreading it
upon paper, I then proceeded in the following way. The paper was
first washed with a strong solution of salt, and when this was dry, it
was washed again with nitrate of silver. Of course, chloride of silver
was thus formed in the paper, but the result of this experiment was
almost the same as before, the chloride not being apparently rendered
more sensitive by being formed in this way.
"Similar experiments were repeated at various times, in hopes of
a better result, frequently changing the proportions employed, and
sometimes using the nitrate of silver before the salt, &c. &c.
'In the course of these experiments, which were often rapidly
performed, it sometimes happened that the brush did not pass over
the whole of the paper, and of course this produced irregularity in
the results. On some occasions certain portions of the paper were
observed to blacken in the sunshine more rapidly than the rest.
ΙΟ
MANUAL OF PHOTOGRAPHY.
These more sensitive portions were generally situated near the edges
or confines of the part that had been washed over with the brush.
"After much consideration as to the cause of this appearance, I
conjectured that these bordering portions might have absorbed a
lesser quantity of salt, and that, for some reason or other, this had
made them more sensitive to the light. This idea was easily put
to the test of experiment. A sheet of paper was moistened with
a much weaker solution of salt than usual, and when dry, it was
washed with nitrate of silver. This paper, when exposed to the sun-
shine, immediately manifested a far greater degree of sensitiveness
than I had witnessed before, the whole of its surface turning black
uniformly and rapidly establishing at once and beyond all question
the important fact, that a lesser quantity of salt produced a greater
effect. And, as this circumstance was unexpected, it afforded a
simple explanation of the cause why previous inquirers had missed
this important result, in their experiments on chloride of silver,
namely, because they had always operated with wrong proportions
of salt and silver, using plenty of salt in order to produce a perfect
chloride, whereas what was required (it was now manifest) was, to
have a deficiency of salt, in order to produce an imperfect chloride
(or perhaps it should be called), a subchloride of silver.
"So far was a free use or abundance of salt from promoting the
action of light on the paper, that on the contrary it greatly weakened
and almost destroyed it: so much so, that a bath of salt water was
used subsequently as a fixing process to prevent the further action of
light upon sensitive paper.
"This process, of the formation of a subchloride by the use of
a very weak solution of salt, having been discovered in the spring
of 1834, no difficulty was found in obtaining distinct and very pleas-
ing images of such things as leaves, lace, and other flat objects of
complicated forms and outlines, by exposing them to the light of
the sun.
"The paper being well dried, the leaves, &c., were spread upon it,
and covered with a glass pressed down tightly, and then placed in
the sunshine; and when the paper grew dark, the whole was carried
into the shade, and the objects being removed from off the paper, were
found to have left their images very perfectly and beautifully im-
pressed or delineated upon it.
But when the sensitive paper was placed in the focus of a camera
obscura and directed to any object, as a building, for instance, during
a moderate space of time, as an hour or two, the effect produced upon
the paper was not strong enough to exhibit such a satisfactory picture
of the building as had been hoped for. The outline of the roof and
of the chimneys, &c., against the sky was marked enough; but the
HISTORICAL SKETCH.
I I
details of the architecture were feeble, and the parts in shade were
left either blank or nearly so. The sensitiveness of the paper to
light, considerable as it seemed in some respects, was therefore, as
yet, evidently insufficient for the purpose of obtaining pictures with
the camera obscura; and the course of experiments had to be again
renewed, in hopes of attaining to some more important result.
"The next interval of sufficient leisure which I found for the
prosecution of this inquiry was during a residence at Geneva in
the autumn of 1834. The experiments of the previous spring were
then repeated and varied in many ways; and having been struck
with a remark of Sir H. Davy's which I had casually met with, that
the iodide of silver was more sensitive to light than the chloride,
I resolved to make trial of the iodide. Great was my surprise on
making the experiment to find just the contrary of the fact alleged,
and to see that the iodide was not only less sensitive than the
chloride, but that it was absolutely insensible to the strongest sun-
shine; retaining its original tint (a pale straw colour) for any length
of time unaltered in the sun. This fact showed me how little de-
pendence was to be placed on the statements of chemical writers
in regard to this particular subject, and how necessary it was to trust
to nothing but actual experiment; for although there could be no
doubt that Davy had observed what he described under certain cir-
cumstances, yet it was clear also, that what he had observed was
some exception to the rule, and not the rule itself. In fact, further
inquiry showed me that Davy must have observed a sort of subiodide
in which the iodine was deficient as compared with the silver: for,
as in the case of the chloride and subchloride the former is much less
sensitive, so between the iodide and the subiodide there is a similar
contrast, but it is a much more marked and complete one.
CC
However, the fact now discovered proved of immediate utility;
for the iodide of silver being found to be insensible to light, and the
chloride being easily converted into the iodide by immersion in iodide
of potassium, it followed that a picture made with the chloride could
be fixed by dipping it into a bath of the alkaline iodide.
"This process of fixation was a simple one, and it was sometimes
very successful. The disadvantages to which it was liable did not
manifest themselves until a later period, and arose from a new and
unexpected cause, namely, that when a picture is so treated, although
it is permanently secured against the darkening effect of the solar
rays, yet it is exposed to a contrary or whitening effect from them;
so that after the lapse of some days the dark parts of the picture begin
to fade, and gradually the whole picture becomes obliterated, and is
reduced to the appearance of a uniform pale yellow sheet of paper.
A good many pictures, no doubt, escape this fate, but as they all seem
12
MANUAL OF PHOTOGRAPHY.
liable to it, the fixing process by iodine must be considered as not
sufficiently certain to be retained in use as a photographic process,
except when employed with several careful precautions which it
would be too long to speak of in this place.
"During the brilliant summer of 1835 in England, I made new
attempts to obtain pictures of buildings with the camera obscura;
and having devised a process which gave additional sensibility to the
paper, viz., by giving it repeated alternate washes of salt and silver,
and using it in a moist state, I succeeded in reducing the time neces-
sary for obtaining an image with the camera obscura on a bright day
to ten minutes. But these pictures, though very pretty, were very
small, being quite miniatures. Some were obtained of a larger size,
but they required much patience, nor did they seem so perfect as the
smaller ones, for it was difficult to keep the instrument steady for a
great length of time pointing at the same object, and the paper being
used moist was often acted on irregularly.
'During the three following years not much was added to previous
knowledge. Want of sufficient leisure for experiments was a great
obstacle and hindrance, and I almost resolved to publish some account
of the art in the imperfect state in which it then was.
"However curious the results which I had met with, yet I felt
convinced that much more important things must remain behind, and
that the clue was still wanting to this labyrinth of facts.
But as
there seemed no immediate prospect of further success, I thought of
drawing up a short account of what had been done, and presenting it
to the Royal Society.
(C
However, at the close of the year 1838, I discovered a remarkable
fact of quite a new kind. Having spread a piece of silver leaf on a
pane of glass, and thrown a particle of iodine upon it, I observed that
coloured rings formed themselves around the central particle, especially
if the glass was slightly warmed. The coloured rings I had no diffi-
culty in attributing to the formation of infinitely thin layers or strata
of iodide of silver; but a most unexpected phenomenon occurred when
the silver plate was brought into the light by placing it near the
window. For then the coloured rings shortly began to change their
colours, and assumed other and quite unusual tints, such as are never
seen in the 'colours of thin plates.' For instance, the part of the
silver plate which at first shone with a pale yellow colour, was changed
to a dark olive-green when brought into the daylight. This change.
was not very rapid: it was much less rapid than the changes of some
of the sensitive papers which I had been in the habit of employing,
and therefore, after having admired the beauty of this new pheno-
menon, I laid the specimens by, for a time, to see whether they would
preserve the same appearance, or would undergo any further alteration.
HISTORICAL SKETCH.
13
"Such was the progress which I had made in this inquiry at the
close of the year 1838, when an event occurred in the scientific world,
which in some degree frustrated the hope with which I had pursued,
during nearly five years, this long and complicated, but interesting
series of experiments-the hope, namely, of being the first to announce
to the world the existence of the new art-which has been since
named Photography.
"I allude, of course, to the publication in the month of January
1839, of the great discovery of M. Daguerre, of the photographic pro-
cess which he has called the Daguerreotype. I need not speak of the
sensation created in all parts of the world by the first announcement
of this splendid discovery, or rather, of the fact of its having been
made (for the actual method made use of was kept secret for many
months longer). This great and sudden celebrity was due to two
causes: first, to the beauty of the discovery itself; secondly, to the
zeal and enthusiasm of Arago, whose eloquence, animated by private
friendship, delighted in extolling the inventor of this new art, some-
times to the assembled science of the French Academy, at other times
to the less scientific judgment, but not less eager patriotism of the
Chamber of Deputies.
"Some time previously to the period of which I have now been
speaking, I met with an account of some researches on the action of
light, by Wedgwood and Sir H. Davy, which, until then, I had never
heard of. Their short memoir on this subject was published in 1802
in the first volume of the Journal of the Royal Institution. It is
curious and interesting, and certainly establishes their claim as the
first inventors of the photographic art, though the actual progress they
made in it was small. They succeeded, indeed, in obtaining impres-
sions from solar light of flat objects laid upon a sheet of prepared
paper, but they say that they found it impossible to fix or preserve
those pictures; all their numerous attempts to do so having failed.
"And with respect to the principal branch of the art, viz., the
taking pictures of distant objects with a camera obscura, they attempted
to do so, but obtained no result at all, however long the experiment
lasted. While, therefore, due praise should be awarded to them for
making the attempt, they have no claim to the actual discovery of any
process by which such a picture can really be obtained.
CC
It is remarkable that the failure in this respect appeared so com-
plete, that the subject was soon after abandoned both by themselves
and others, and, as far as we can find, it was never resumed again.
The thing fell into entire oblivion for more than thirty years: and
therefore, though the daguerreotype was not so entirely new a con-
ception as M. Daguerre and the French Institute imagined, and
though my own labours had been still more directly anticipated by
14
MANUAL OF PHOTOGRAPHY.
Wedgwood, yet the improvements were so great in all respects, that
I think the year 1839 may fairly be considered as the real date of the
birth of the photographic art, that is to say, its first public disclosure
to the world.”
In one of the parts of "The Pencil of Nature" the following
"Notice to the Reader" was given:-"The plates of the present
work are impressed by the agency of light alone, without any aid
whatever from the artist's pencil. They are the sun-pictures them-
selves, and not, as some persons have imagined, engravings in imita-
tion." Many of the plates in this "Pencil of Nature" in the writer's
possession are apparently in the same state as when issued, others are
much faded. One of Abbotsford, with the words in Talbot's own
autograph, "From Nature, 1844, H. F. T.," is pale but still distinct.
Fox Talbot's wish for a process to reproduce the camera-image thus
appears to have been realised as early as 1835, when views of his resi-
dence, Lacock Abbey, were taken, but it was not until January 1839
that he made his discovery known, through Professor Faraday, at a
meeting of the Royal Institution, London, and a few days later the
full details of the process were given at a meeting of the Royal Society
under the name of Photogenic Drawing. Various improvements were
made, and ultimately it was found that by treating the paper in a
certain way the exposure necessary could be very much reduced. The
photographic image which was found to be latent and invisible could
be developed by the application of gallic acid. It has been said that
the discovery of the latent image and the possibility of its development
in this case, as in that of the daguerreotype, was the result of “acci-
dent." One of Talbot's prints on paper came in contact with a solution
of nut-galls, which developed the picture, and in consequence of this
gallic acid became a most valuable substance in the hands of the
photographer. The fact that gallic acid could be used to develop the
photographic image was independently discovered by the Rev. J. B.
Reade, who claimed that in 1837 he succeeded in making negatives by
using that acid, but he admits that the discovery of "the master fact,
that the latent image which had been developed was the basis of
photographic manipulation," was due to Talbot and to him only.
That Reade missed this important discovery is very remarkable.
Talbot's process was patented, but after a few years he gave up his
patent rights, and his most valuable discoveries were henceforward
public property.
The pictures produced by Talbot were negatives, and from them
positives could be made in quantities, so that his success in this
respect possessed a distinct advantage over the daguerreotype, but
the texture of the paper was a drawback which was difficult to over-
come. Waxing the paper gave better results.
Glass was, of course,
I
HISTORICAL SKETCH.
15
thought of and tried, but the difficulties to be overcome were great.
Herschel, Le Gray, and others tried albumen and gelatine in which
to form the silver compounds on the glass, but with very little
success. Collodion had also been suggested, but it remained for
Mr. F. Scott-Archer to introduce a process in which collodion on
glass took the place of paper, and which in a very few years came
into almost universal use.
The process is unlike the others already named, inasmuch as it
is capable of producing both positives and negatives. The process
was not patented, but presented to the world-a free gift, and it is
impossible to exaggerate its importance. The details were published
in 1851, and the method has remained to the present time unrivalled,
as in certain respects the processes which have to a large extent
superseded it do not give results equal to collodion.
There are
disadvantages attending every process as yet introduced, especially
when they are to be worked away from home, and attempts were very
soon made to displace the wet process by others which dispensed
with the silver bath. The most successful rival to collodion for many
years was the collodio-albumen process, and there were many others,
all having the same end in view, that of getting rid of the silver
bath, and at the present time gelatine for all outdoor work has
entirely taken the place of collodion. The camera, as now con-
structed, is so reduced in weight as to leave very little to be desired,
but the weight of the glass still remains, although even that difficulty
appears in a fair way to be removed by the introduction of films or
sheets of celluloid coated with gelatine emulsion, used from roller
slides attached within the camera.
A method was introduced by Talbot whereby the silver plate was
etched in such a manner that it could be printed from in the copper-
plate press. Within the last few years many methods have been
invented, and in some cases patented, having for their object the
production of blocks or plates which could be used as illustrations
for books.
The uncertainty of the stability of prints in silver led to the
invention of two methods of much importance: first, the Autotype—
a process by which pictures are made in carbon, or any other pigment,
and as to the permanence of which there can be no doubt. Then,
following this, Mr. Walter Woodbury invented the process called
by his name. It would, however, be almost impossible to enumerate
even the names of all the processes which have been introduced
within the last thirty years, not to go farther back. The most
important, which may be named here, are Photo-lithography, Collo-
type (under various names), Zinc-etching, and Photogravure.
The wonderful results already attained naturally make us hesitate
16
MANUAL OF PHOTOGRAPHY.
possibility of producing photo-
The colours of the spectrum have
in forming an opinion as to the
graphs in the colours of nature.
been produced and fixed, but no means have as yet been found by
which the mixed colours found in natural objects can be reproduced
in a permanent form.
In the following pages will be fully described the most useful pro-
cesses and the apparatus necessary to work them; the less important
will be referred to more briefly.
The progress made within the last thirty years has been chiefly in the
direction of rapidity, and for general working the advantage obtained
is very great. Even with the daguerreotype, a picture of a wheel
in rapid motion was possible, and by one of the slowest processes,
the calotype, pictures of objects in motion have been photographed,
the development being very prolonged. By the collodion process,
again, subjects requiring great rapidity, such as breaking waves, have
been taken. There can, however, be no doubt that the introduction
of the gelatino-bromide process has made the practice of photography
extremely simple, and has very greatly increased the usefulness of
the art. Gelatine has for many purposes superseded collodion; but
the latter process has advantages which will be sufficient to prevent
its going out of use, as so many others have done.
Looking back upon the last fifty years, we can trace the influence
which photography has exerted on the sister arts of drawing and
painting, and there can be no doubt that the influence has been help-
ful. In Portraiture, artists are undoubtedly indebted to photography
for more natural effects, and the photograph can often be used in the
absence of the sitter, thus saving time, and probably securing a more
truthful rendering. The influence of photography in art can, more-
over, be seen in other ways. The prejudice of artists against photo-
graphy is wearing away; there should be no rivalry between the two
arts, for they can be of mutual assistance, and there are probably few
artists now who do not themselves use the camera and find great
advantage from it.
The various applications of photography in other directions are too.
numerous to be referred to here in detail; to the Scholar, in the faith-
ful reproduction of precious MSS. and the treasures of antiquity, it
is simply invaluable; the Physiologist registers by its means the
secrets of Nature, whilst the Pathologist chronicles in the same way
departures from Nature's laws, and so gains a clue to the detection of
disease; the Astronomer, the Meteorologist alike press it into their
service, and thus obtain results which could be gained in no other
way. In the Army, the Navy, photography is a faithful agent; to the
Traveller bent upon scientific research it is indispensable; to the Tourist
abroad for pleasure the camera is the most delightful of comrades. In
CHEMISTRY OF PHOTOGRAPHY.
17
short, it would be hard to say where the line is to be drawn, what
science or what art does not make some use of photography, for its
applications are extending daily. The object of this brief introduc-
tion is to show how, step by step, the early attempts to fix the light-
pictures have been improved until they may now be said to be almost
perfected. It is, at least, difficult to imagine in what direction,
except in regard to the fixing of natural colours, further discoveries
may be looked for.
CHAPTER II.
CHEMISTRY OF PHOTOGRAPHY.
Of the many branches of Chemical Technology, it would be difficult
to point to one which offered a wider field for new work than the
chemistry of photography. It is only a few years since a commence-
ment was really made in unravelling the mysteries of the processes
involved in the production of a finished photograph; but already-
thanks to the researches of Hunt, Abney, Carey Lea, Vogel, and
others—considerable progress has been made in this branch; and
their work will form a safe starting-point for further investigation
into the many operations remaining unexplained. At first, the beauty
of the results obtained by photography caused the workers in the art
to turn their attention mainly towards the discovery of new processes
with the object of facilitating the mere mechanical routine, in order
to gain greater perfection, or to extend its many applications and uses;
and this success was so great as, perhaps, to have delayed advance in
the discovery of the principles concerned.
The object of this chapter is to explain, as far as space will allow,
the chemistry of those changes necessary to the building up of a
photographic picture. No doubt there are numbers, probably the
majority, of persons successfully practising photography who have
only a technical knowledge of the subject; to such, however, any
irregularities in results present almost insuperable difficulties, which
might easily, or, at least, more certainly and readily, be overcome by
a knowledge of what is taking place or might take place among the
chemicals in use. In fact, the possession of a knowledge of chemistry,
and especially of the chemistry of photography, makes all the differ
ence between a mere operator, the slave of formulæ, and one who can
make the processes the slaves of his wishes.
As the name implies, the chief factor in photography is Light
The result of its action may be physical only, or it may produce
chemical changes in the substances upon which it falls.
B
18
MANUAL OF PHOTOGRAPHY.
Physical Action.-Although the purely physical action of light is
of but little importance in photography, there are several well-known
instances in which it produces some physical alteration, as in the case
of phosphorescence, change of crystalline form, the setting up of
electric currents, and the change by which water-vapour will deposit
on a plate after exposure to light so as to reveal, in a film of con-
densed moisture, the otherwise invisible picture.
Bordering upon each mode of action—that is, action both of
physical and of chemical nature-is the formation of molecular com-
pounds and addition-products. As an example of this, the explanation
given by Keyser of the action of light upon asphalt, which he regards
as due to polymerisation, may be cited. He adduces in support of
this view the fact that the formation of the insoluble substance is
not accompanied by a gain in weight, and that fusion is sufficient to
again render it soluble. In such cases there is no close chemical
union; the change is a physical alteration in the state of molecular
aggregation; but it may also be looked upon, in certain cases, as a
feeble union, due to residual chemical affinity. A further illustration
of the relation between physical and chemical changes is the influence
of pressure on chemical change (Spring), and the production of an
image capable of development by shearing stress (that is, pressure
applied to the prepared film), although the amount of chemical.
change was found by Abney not to be in proportion to the pressure.
Chemical Action.-The cause of the chemical action may be found,
in many cases, in the physical explanation of the nature of light or
radiant energy, the undulations, of which it is supposed to consist,
exerting their energy in bringing about chemical union, or decom-
position. This undulatory theory will be here assumed, together
with the chemical theory that bodies are composed of molecules which
are not only themselves in a continual state of oscillatory movement,
but whose constituent atoms are also subject to an intra-molecular
motion of a similar kind. Now, on the principle of the superposition
of small impulses, such impulses, repeated at regular and suitable.
intervals, may produce a considerable effect, as in the gradual raising
of the extent of motion in a swing. In a similar way, it can easily
be conceived that if either the wave-length, or the amplitude of
vibration of the light-rays, bore any simple relation to the molecular
or atomic movements in a substance, the energy contained in the
former might be imparted to the molecules or atoms, and cause
chemical change. In fact, whenever light is absorbed by a body,
whether wholly or partially, it must have done work of some kind;
in general, perhaps, a rise in temperature results, but in special cases
the effect upon the atoms or molecules may suffice to cause them to
enter into fresh combinations.
CHEMISTRY OF PHOTOGRAPHY.
19
It will be seen in Chapter iii. (Optics of Photography) that ordi-
nary white light is made up of rays whose wave-lengths vary widely
and regularly, and this difference is utilised in separating the rays
from each other into a spectrum. Then, while chemical change may
be produced by a ray of a certain wave-length or amplitude, one is
prepared to find that a ray of another oscillation-period, or of lesser
intensity, will have no such power. The former will be an actinic
ray for the body under consideration, which will undergo chemical.
change only, or to a greater extent, in that portion of a spectrum
than in another. This difference may be well illustrated by means
of a box about 4 inches square and 8 inches high, having red glass
on one side, yellow on another, and blue or plain glass on a third
side; this last also having a sliding opaque shutter. If a glass bulb
containing a mixture of hydrogen and chlorine gases be placed in the
middle of the box, and then a flash of magnesium powder be used in
front of the red or yellow glass, no result will follow; but when the
shutter is withdrawn and the magnesium light is burnt in front of
the blue or plain glass, the bulb is at once shattered by the two gases
uniting to form hydrogen chloride; thus showing that the actinic
light in this case is not contained among those rays whose wave-
lengths produce a red or yellow effect.
But if in any way the energy of a ray of light becomes converted
into another form of energy, the ray, as a ray, must cease to exist; it
will have been absorbed, while those which produce no alteration (in
other words, have themselves undergone no alteration) will be trans-
mitted, so that on examining the spectrum after passing through any
substance affected by light, certain rays will be wanting-it will give
an "absorption spectrum." Draper has enunciated the statement
that there is a relationship between absorption and photo-chemical
effect; and the same investigator has also shown the amount of
chemical change to be proportional to the light-intensity. Absorption
spectra, however, are no measure of chemical action; for Bunsen and
Roscoe have demonstrated that but a small portion of the absorbed
light falling on a sensitive substance is employed for chemical
purposes.
The chemical action of light may be that of oxidation or reduction ;
or it may produce mere decomposition or photo-dissociation, as in the
case of the dissociation of hydrogen iodide, and of the oxides of the
heavy metals (mercury, gold, &c.), under the influence of light.
Oxidation by Light.-This action was one of the first employed in
devising photographic processes; Niépce having in 1824 utilised the
oxidation of asphalt in his invention of the bitumen process; for, as
in this method air is an essential, it appears to be a case of oxidation.
The actual action is as yet unexplained. Indeed, it has already been
20
MANUAL OF PHOTOGRAPHY.
mentioned (p. 18) that other authorities regard the change as one of
polymerisation, while a recent experiment seems to show that the
addition of sulphur increases the sensitiveness of asphalt. It has
been discovered, however, that one of the constituents of ordinary
asphalt will dissolve in alcohol, and is insensitive to light; that
another dissolves in ether; and that a third is insoluble in either.
The third portion is the one which undergoes change most readily;
so that a more sensitive material is prepared by dissolving out the
less sensitive ingredients.
Reduction by Light. This may be utilised in two ways—we may
either have an easily reducible substance from which a picture is
formed by light, by its reduction in the presence of oxidisable
matter; or it may be the oxidisable substance which builds up the
picture on exposure to light in the presence of an oxidising agent.
The second substance, the presence of which enables the light to
exert its photo-chemical action upon the first, is called a
"Sensi-
tiser." Examples of the first mode of action are the processes in
which salts of the heavy metals are employed. Take iron as an
example ferric chloride in presence of oxidisable organic matter is
reduced to ferrous chloride, or a salt of iron with an oxidisable
organic acid may be employed, such as the oxalate or citrate-
Fe¸Cl¿ + C₂H₂O4 = 2FeCl2 + 2HCl + 2CO2.
The amount of reduction will depend, by Draper's second law, upon
the intensity of the light. A picture will be formed on a piece of
paper coated with the chloride (for paper alone acts as a sensitiser)
after exposure to light; but as the ferrous chloride differs little in
colour from the ferric salt, the picture is as yet hardly visible, and
on washing the paper with a solution of K.FeCy12, the ferrous
chloride will give a precipitate of Turnbull's blue of a density de
pending upon the amount of reduction undergone, and, therefore,
proportional to the intensity of light, that is, to the brightness of the
objects depicted—
6FeCl2 + 2K¿Fе,Cy12 = 2 Fe,(Fe,Cу12) + 12KCl.
Thus the picture is "developed " by converting an invisible compound
into a visible one, and may be fixed by washing away all unaltered
ferric chloride, since this will prevent any further chemical action
when the picture is brought into the light. Uranium compounds
have been used in a similar way.
Of the second mode of action, the oxidation of gelatine by chromic
acid is the best example. Upon this reaction depends the well-known
"Autotype" process. The CrO, is reduced to Cr,O,, and the oxygen
thus lost oxidises the gelatine and gives rise to the formation of various
3
CHEMISTRY OF PHOTOGRAPHY.
21
products, such as formic acid, &c. It may be interesting to note that
with an exposed paper, which is not developed at once, the oxida-
tion is continued, and after a time the image cannot be developed.
Advantage may be taken of this peculiarity to underprint the subject,
and allow the after-action to complete the process. But with silver
bromide, or other emulsion plate, there appears to be no further
action, and a good picture may be developed years after the exposure
was made.
But the haloid salts of silver are those upon which the action
of light is of the most importance. It is not yet determined whether
this action is one of reduction or of oxidation, or, indeed, what it is.
Remembering the similar situation of silver and copper in the
periodic arrangement of the elements, and their consequent similarity
in chemical properties, it has been argued that the evidence is in
favour of the existence of a sub-chloride. But the AgCl is itself
the chloride analogous to cuprous chloride, which is the lowest
chloride of this metal known; while no one has yet succeeded in
isolating the AgCl generally assumed to exist in the product
darkened by exposure to light. The only well-established fact so far
is, that this darkened chloride is poorer in chlorine, and that there
is always a largely preponderating amount of chloride remaining un-
altered a fact which has suggested the existence of a physical com-
bination between the silver chloride and the reduction product; but
this hardly seems probable, since the ratio of the two would be about
twenty to one. That it does not contain metallic silver, seems evi-
dent from the fact that the darkening takes place under nitric acid.
Hodgkinson has endeavoured to prove the formation of an oxygenated
body, AgOCl, comparable to the oxychloride of copper; and in
favour of this view is the sensitising action of the presence of water;
but the necessity of oxygen or water is denied by other experi-
menters, since the dry chloride darkens under dry benzene, and even
in a vacuum, so that perhaps at present it is as well to adopt the
suggestion of Meldola, that the constitution of the coloured pro-
duct may vary in the different cases. Bearing upon this question
of the composition of the chloride darkened by light, are (1) the photo-
salts and coloured bodies obtained by Carey Lea, and others, and
prepared in a way to lead one to expect the formation of a sub-salt
could such exist; and (2) the experiments of Güntz upon the action of
gaseous hydrogen chloride upon silver fluoride; but the uncertainty
surrounding the whole subject shows how much remains to be done
in photo-chemistry, and how difficult a matter it is for investigation.
The process of Ripening and theory of sensitisers also belongs
to this division of the subject. The former-ripening-refers to the
molecular change undergone by the silver haloid by which it is
22
MANUAL OF PHOTOGRAPHY.
rendered more sensitive to light. Thus in the gelatino-bromide emul-
sion, when the silver bromide is first precipitated, it is in a very finely
divided state, the particles being estimated by Eder to have only a
diameter of 0.0008 to 0.0015 mm. ; but after standing a few days,
or by heating to 60° C. (140° F.) for a few hours, the sensitiveness is
increased, and there is a gradual accretionary change in the state
of molecular aggregation, the particles having the maximum sensitive-
ness being 0.0034 mm. in diameter (Eder). The physical change is
noticeable in the alteration of the absorption spectrum, the ripened
bromide transmitting much less of the red. The chemical change
is probably a molecular union between the gelatine and bromide.
forming a gelatino-bromide,¹ the formation of which causes increased
sensitiveness, as it is more easily reduced than the haloid salt
alone. But if the heating be continued too long, further chemical
action sets in, the silver bromide is reduced, and the plate will on
development appear fogged. The accretionary process is probably
owing to hot gelatine solution, in presence of potassium bromide,
having a slight solvent action on silver bromide, and this dissolved
silver salt on being redeposited attaches itself to the particles of the salt
already existing. This property of gelatine and potassium bromide
together is a reason for the necessity of an excess of the latter salt
in the preparation of the emulsion. The action of ammonia as a
ripening agent depends on precisely similar principles, its solvent
action on silver bromide being well known.
Theory of Sensitisers.—A sensitiser, as has been pointed out, is a
body whose presence is essential, or accessory, to the photo-decompo-
sition of a second body. In many cases the action is one of mass,
on the principle that when any body undergoes separation into two
or more substances there is a limit beyond which the action will not
advance, since the products of decomposition then tend to reunite
to form the original body. A state of equilibrium is reached where
we have a quantity of the products of decomposition in presence of
some of the undecomposed body. Probably molecules continue to be
split up, but beyond a certain point the number of recombinations of
the liberated bodies exactly counterbalances the number of molecules.
split up; if, then, there is present a second body which combines
with one or other of the decomposition products, thereby removing
it from the sphere of action, equilibrium is destroyed, and a further
number of molecules can be decomposed until equilibrium is again
restored. The second body whose presence acts in this manner is
the sensitiser. The activity depends upon the affinity the sensitiser
has for the liberated body, and upon the relative affinities of the
constituents of the bodies concerned.
1 Meldola, Cantor Lectures, 1891.
CHEMISTRY OF PHOTOGRAPHY.
23
Taking the silver haloids, there is in the collodion process a film of
collodion which is salted with an iodide or bromide, or both. When
the plate coated with the salted film is immersed in the silver nitrate-
bath, the silver haloid is formed—
CdI₂+ 2AgNO3= 2AgI + Cd(NO3)2-
and the plate being exposed wet, with a thin layer of solution of
silver nitrate remaining upon it, it is this excess of the nitrate which
acts as the "sensitiser" by appropriating to itself any halogen
liberated, and thus preventing the inverse action by which the pro-
ducts of photo-decomposition might be reconverted into the original
body. In dry-plate photography an excess of AgNO, cannot be
allowed to remain, as it would dry into small crystals and render the
film useless; and, further, according to Vogel, it forms with the silver
haloid an insoluble white crystalline body, 2AgNO3 + AgI, which is
insensitive to light. The AgNO, is, therefore, all removed by wash-
ing, and the sensitiveness of the plate restored by other sensitisers, or,
as they are sometimes called, preservatives. Organic bodies are found
to be the most suitable for this purpose, such as tannin, albumen,
gelatine, morphine, and some others.
Reviewing the chemical changes likely to occur in the formation of
the latent image, an idea can usually be got as to what body is play-
ing the part of sensitiser. In the daguerreotype, with its film of
AgI on a layer of metallic silver, it is probably the latter which, by
absorbing any liberated iodine, acts as sensitiser, though the AgI
itself may play the same part if it is able to combine with more
iodine, as is the case with some iodides.
Silver nitrate is the sensitiser in the wet collodion process; the re-
action is usually written thus:-
61 +5AgNO3 + 3H20=5AgI + AgIO¸ + 6HNO¸ ;
and there is in fact a considerable amount of nitric acid liberated.
In dry-plate photography the preservative, and in the emulsion pro-
cesses the gelatine itself, or other vehicle holding the photo-sensitive
salt, acts as sensitiser. In one or two cases the sensitising medium
has only an indirect action; for example, in Obernetter's process the
sensitised paper contains both cupric chloride and ferric chloride; the
latter on exposure is reduced to ferrous chloride, the paper acting as
a halogen absorber, and the cupric chloride is then at once reduced
by the iron salt-
2 FeCl2 + 2 CuCl₁₂ = Cu₂Cl₂ + 2FeCl3 ;
-2
and it is the cuprous chloride thus indirectly produced which yields
the brown print by treatment with thio-cyanate and ferricyanide.
24
MANUAL OF PHOTOGRAPHY.
In the platinotype process there is a paper-reducing surface
containing ferric oxalate and potassium chloro-platinite. The iron
salt on exposure is reduced to ferrous oxalate, and the platinum
compound is unchanged; but on dissolving the reduced oxalate in
hot potassium oxalate it at once reduces the platinite to metallic
platinum.
As regards the silver-positive process, or silver printing, the paper
again is the sensitiser; but it must be remembered that albumen is
able to form salts, and that silver albuminate, which is present in
albumenised paper, is itself coloured by light, and plays an important
part in the formation of the printed image.
Orthochromatic Photography. Besides these means of increasing
the sensitiveness of a film is the use of colouring matters. Draper's
law of absorption says it is only rays which are absorbed that can pro-
duce any chemical effect. One can tell from its absorption-spectra to
what rays a body may be photo-sensitive. Thus silver bromide mainly
absorbs violet or blue rays, and it is light of this colour by which it is
mostly affected, while the yellow rays which it transmits produce no
effect. To this is due the defect in photography that objects are not
reproduced in the relative brightness as seen by the eye; a bright
yellow object is depicted but dimly, while a dark blue one may come
out comparatively light. Vogel, however, has shown that it is not
only the rays absorbed by the sensitive body which can produce
photo-chemical effect upon it, but that the rays absorbed by a second
body with which it is mixed may also decompose it; and his explana-
tion, as modified by Eder, of the effect of dyes is that their action is
physical-hence the name optical sensitisers. The colours are supposed
to form "lakes" with the silver salt, thus causing a more intimate
contact whereby the energy absorbed by the colours is to some extent
transmuted into chemical energy, which effects the indirect photo-
decomposition of the silver haloid. Abney's experiments, and Vogel's
observation that the less stable the colour the more readily it acted
as sensitiser, on the other hand, go far to prove that the dyes, like the
other sensitisers, act chemically; for this requires the bodies to be
unstable, since Abney maintains that it is the decomposition products
of the colour set free by the action of light that exert a direct
reducing action upon the silver bromide; and although it is generally
considered to be an act of oxidation when a colour fades, it has
already been mentioned in the case of gelatine that the products
of oxidation of complicated organic bodies are frequently active re-
ducing agents, e.g., formic acid.
Whatever the cause, it is now possible, by using certain colouring
matters, which must be of the complementary colour to that it is
desired to absorb, to render the film sensitive to any particular rays,
CHEMISTRY OF PHOTOGRAPHY.
25
and to obtain photographs true to the aspects of Nature as regards.
relative brightness of tints.
Silver bromide is much more readily influenced by the absorptive
powers of colours than is silver chloride, and the latter more than the
iodide. It is usually necessary, as one would suppose, to have an
ordinary sensitiser present.
Solarisation. To return to the influence of mass; the sensitiser
itself may have absorbed so much of the liberated halogen that here
also the influence of mass upon a reaction sets in, and the compound
formed with the sensitiser begins to decompose as fast as it is formed.
This is what takes place in solarisation or reversal of the image; but
it is not so simple as here roughly indicated; for, although Abney
obtained reversal on exposing a gelatino-bromide plate under benzene,
his experiments otherwise tend to show that oxygen plays a part in
the phenomenon. The nature of the changes cannot be fully explained
as long as the composition of the photo-salts remains undetermined;
but an idea of it may be gained by first looking at the case of the
fading of the invisible image spontaneously in the dark. Oxidising
agents, e.g., the halogens, will destroy the latent image, and probably
the unstable halogenised sensitiser and reduced silver haloid when
removed from the influence of light begin to react, re-forming the more
stable normal salt. In the daguerreotype, if AgI is the sensitiser by
formation of AgI, the image will probably fade from this AgI, part-
ing with its excess of iodine to the reduced silver image. In the
wet collodion process, where AgNO, is the sensitiser, the action of the
liberated iodine has been supposed to be-
61 +6AgNO3 + 3H,O= 5AgI + AgIO3 + 6HNO3.
There is thus free HNO3; and the image is more permanent if this is
washed away, or its formation prevented; so that it is probably the
oxidising action of this free nitric acid which causes the destruction
of the image.
In dry plates, most likely, the sensitiser again gives up the absorbed
halogen owing to the action of oxygen upon it. What thus takes
place in time without other aid may be more rapidly brought about
by reversing agents in the light, that is, by bodies which readily part
with the halogens in air and light. Potassium iodide is an example-
4KI + 2H₂O + O₂ = 4KOH + 2I2.
2
The iodine would destroy any reduced haloid with which it came in
contact; and on this fact has been based a positive-printing process,
in which a sheet of sensitive paper coloured by a preliminary expo-
sure was afterwards coated with a solution of potassium iodide, and
then used for printing engravings and other line subjects, since all
26
MANUAL OF PHOTOGRAPHY.
parts on which the light acted would, by reason of the photo-decom-
position of the potassium iodide, bleach the coloured silver paper, and
reproduce dark lines as dark lines.
Solarisation is destruction of the image by over-exposure followed
by reversal, the reversed image again being destroyed and brought
back to the original state; this cycle is repeated so long as exposure
continues.
Pseudo-solarisation, or reversal by exposure to light towards the end
of development, is, of course, purely optical. The light cannot readily
penetrate the dark silver deposited on development, and therefore
reacts upon the unaltered silver haloid in the film to a greater extent
in those parts where but little silver has been formed. If, then, this
second illumination be stronger than the first, the latter will, on com-
pleting the development, give the less dense deposit of silver and a
positive result.
That solarisation is accelerated by oxidising agents, and that potas-
sium iodide in presence of air loses iodine, explains the necessity of
removing all excess of the iodide from a film, and why emulsion
prepared with excess of the haloid instead of excess of silver nitrate
is the less sensitive of the two; for, in precipitation by double decom-
position the precipitate very generally tends to carry down traces of
the precipitant which is in excess either mechanically or in some
undetermined molecular combination; therefore, in preparing silver
iodide with an excess of potassium iodide, traces of the latter will be
carried down and remain in the film, tending to neutralise the action
of the sensitiser and thus facilitating reversal. By using an excess of
AgNO, it is traces of this salt which get carried down, and, acting as
a sensitiser, render plates prepared in this way much more sensitive.
The assumption that solarisation is largely caused by the saturation
of the halogen absorber, e.y., gelatine, explains the fact that the more
sensitive the plate-that is, the more rapidly the halogen is set free by
light—the more readily does reversal set in; and it explains also why
a preliminary exposure hastens solarisation, for the sensitiser by this
exposure is already partly halogenised, and is to that extent nearer
saturation or the first stage of equilibrium. Oxidation now probably
plays an important part, for the intervals between the stages of the
cycle lengthen rapidly, and the action too is retarded by the applica-
tion of reducing agents to the film.
The strength of developer may also affect the result obtained from
an over-exposed plate, for the sensitive film on oxidation, or after
absorption of halogen, is less pervious to solutions, so that a strong
developer will act more readily on the unreversed portions and pro-
duce a positive; while a weak developer, having more time to work
in, and finding but little reduced haloid to act upon in the weak.
CHEMISTRY OF PHOTOGRAPHY.
27
lights, produces a normal negative with greatest density of silver
deposit in the portions most strongly illuminated.
An interesting case of reversal has been recently investigated by
Colonel Waterhouse, that of reversal by the addition of thiocarbamide
to the eikonogen developer. His experiments have an important
bearing upon the growing opinion as to the part which electro-
lytical actions play in development; for the reversal was found to
be accompanied by reversal of the current, in other words, the
shadows became the negative pole, thus attracting the positive ele-
ment, silver, and causing its deposition upon the portions of the
negative which should have remained clear. This action of the thio-
carbamide Colonel Waterhouse suggests to be due to the formation
of silver sulphide on the unexposed parts, and this body acting as
negative element towards silver, the metal is deposited upon the
shadows while the halogen goes to the silver, converting it into
haloid, which is then dissolved away. Photographic reversal is, as
thus explained, a case of electro-chemical reversal. (See Reversal of
the Image.)
Developing. Only in exceptional cases does the photo-chemical
effect of light produce on the sensitive film any visible alteration, the
image "photographed" upon the sensitive plate is invisible or latent;
the light, then, having done its work, means have to be found by
which the change in the photo-sensitive salt may be made visible.
The agents so used are called "developers." The action of developers
is in the main chemical, and as their chemical nature, and the reaction
they bring about, changes as the kind of film is changed, the rationale
of development in the various processes will be dealt with separately;
but in all cases the result of development, the production of a
negative or of a positive, must depend upon whether the agent em-
ployed exerts its action upon that portion of the sensitive substance
which has or has not been affected by exposure; as in the case of
the photo-reduction of ferric chloride, from which either a positive
or negative may be obtained according to the manner of treatment
in developing.
In the Daguerreotype Process the vapour of mercury is the developer;
but nothing definite can be said as to the way it acts. It is known
that the mercury vapour attaches itself to the body altered by light,
but whether from a physical or chemical cause is uncertain, for the
vapour of water alone is sufficient to produce a visible picture, which
vanishes as the condensed particles are dissipated again. At any rate,
the amount of metal deposited is proportional to the quantity of sensi-
tive compound which has undergone photo-decomposition, and in this
respect the process is typical of the action of all developers.
The Wet Collodion process depends upon the reducibility of silver
28
MANUAL OF PHOTOGRAPHY.
nitrate by readily oxidisable substances. Ferrous sulphate is such a
body, being oxidised to ferric sulphate and nitrate-
6FeSO4 + 6AgNO3 = 2Fе, (SO4)3 + Fe₂ (NO3)6 + 6Ag.
It is usually mixed with acetic acid and alcohol, the latter to ensure
the even flow of the solution, and the former to prevent immediate
reduction of the silver nitrate, and consequent deposition of silver
over the whole plate with production of fog, instead of being formed
only upon the altered sensitive salt by the setting up of an electrolytic
couple; for a current of electricity is produced when silver is placed
n a solution of silver nitrate, the metal in which deposits itself upon
the silver, thus an image can be built up by reduced silver continuing
to deposit upon that already formed; but whether the initial step of
development is the deposition of silver or reduction of altered haloid
to silver is undetermined. The use of acetic acid and the mode of
formation of the image by deposit of silver from above upon that
already existing has given this class the name of acid developers and
accretional or physical developers. The necessity for having the solu-
tion acid is probably because on adding ferrous sulphate to an alkaline
solution of silver nitrate, metallic silver is not precipitated, but a
black compound of silver and iron oxides. This, too, explains the
difficulty of working with alkaline waters such as those containing.
much calcium carbonate.
In Dry-plate Photography, on the other hand, the developer is alka-
line, and there is no silver salt upon the plate itself or in the developer
from which to obtain the silver necessary to form the image. The
action is most likely electrolytical here, as with wet plates; but the
distinguishing feature is that the film supplies the requisite silver by
reduction of the haloid salt which it holds; this class is therefore
sometimes called the reductional or chemical, but usually the alkaline
developers, from the necessity of using an alkaline reducing agent.
A great number of readily oxidisable organic bodies have been sug-
gested and employed as developers, such as glucosides, sugars, ethereal
oils, &c. The oxy-derivatives of benzene and naphthalene are the
most useful. Ferrous sulphate is here of no use, as it cannot reduce
the silver haloids, and only acts upon silver nitrate in an acid solution ;
whereas pyrogallol, as an example of the alkaline or chemical de-
velopers, is an active reducing agent towards the silver haloids in the
It has been mentioned that in consequence of
presence of an alkali.
the silver which goes to form the picture in a wet collodion plate
being supplied by the silver nitrate upon it, the image grows by
physical accretion above, or that it must exist in relief; and that this
is so is shown by the possibility of entirely dissolving it away and
CHEMISTRY OF PHOTOGRAPHY.
29
leaving the clean film beneath unaltered. But in alkaline development
the image grows by continued reduction of the silver haloid down-
wards, as may be seen by the image only becoming visible at the back
towards the end of the development; consequently when this silver is
removed by acid, a sunken cast of the image is left in gelatine. But
as alkaline solutions of pyrogallol and similar bodies are able to reduce
the silver haloids, the difficulty arises that, were they allowed to act
alone, the whole plate would be fogged. The action must be restrained
so as to allow their greater reducing action upon the photo-altered
compound to set in before any action can take place upon the unal-
tered haloids. The first action, then, in developing a dry plate is the
reduction of the photo-salt to metallic silver, and as the light cannot
have produced any effect throughout the whole thickness of the film,
it has to be accounted for why reduction in development should
continue downwards in the way it has been proved to do. It is
here the electrolytical action commences between this first deposit of
silver and the silver bromide beneath it in the film. Taking pyro-
gallic acid as typical of all the organic developers, its action upon
silver bromide may be thus represented :-
C&HoO3 + 4AgBr + 12KOH= 4Ag + 4KBг + 6H₂O + K¸CH₂O,
8
99
the K&CHO, representing the product of oxidation of the developing
agent employed; but by adding a restrainer the reducing action can
only exert itself upon the more susceptible body forming the invisible
image.
Many organic iron salts can be used as alkaline developers, as the
double oxalate of iron and potassium, K,Fe(C₂O4)2, which acts very
powerfully, and has to be restrained by means of potassium bromide
from acting directly upon the unaltered haloid, and the silver thus set
free enables the action to be continued upon the unaltered bromide
beneath, either by a chemical action between it and the nascent silver, or
electrolytically as above indicated. The latter view seems the more
probable, since particles of silver merely pressed into a gelatine-bromide
film can be developed so as to produce an impression of themselves in
metallic silver out of the haloid within the film. This is accounted
for by supposing an electrolytic action to be set up between the silver
particles and the silver bromide, causing the reduction of the latter,
and the liberated bromine oxidises the developer or solution, which,
with the two elements referred to, constitutes the electrolytic cell;
and in further support of this is an experiment made by Colonel
Waterhouse, who actually measured the strength of currents generated
in using ferrous oxalate as developer, and found an E. M. F. of 0.09
volt.
30
MANUAL OF PHOTOGRAPHY.
As it is possible by means of restrainers to differentiate between the
relative reducibilities of altered and unaltered silver bromide, it is
not surprising to find that any portion of the bromide the reduction
of which has been commenced, or the stability of which has been
lessened, can be detected by applying a developer. Thus, it is not
only possible to develop a photographically produced image, but one
chemically or even mechanically formed. By applying a solution of
some body which has a reducing action upon silver bromide, the
portions so treated will be developed in silver on applying a suitable
developer, and marks made on a plate by pressure can be similarly
developed, due probably, as the experiments of Spring and others
show, to some slight alteration or incipient decomposition in the
silver salt. It is facts such as these which give greater probability
to the invisible image differing chemically from the unaltered haloid,
than to its being a mere physical modification of lesser stability.
Restrainers and Accelerators.-Mention has been made of the
addition of certain bodies to a developer to retard or hasten its
reducing action. Of the former class, potassium bromide is mostly
used with dry plates, while acetic acid plays the same part in acid
developers by lessening the reducing power of ferrous sulphate upon
silver nitrate. The use of potassium bromide as restrainer probably
rests upon the formation of a double salt between it and silver
bromide, this double salt being less reducible than the silver haloid
alone.
Accelerators produce the contrary effect, but not exactly in an
analogous manner; for, whereas most restrainers act by increasing
the stability of the reducible body in presence of the developer, an
accelerator generally acts by increasing the activity of the reducing
agent; for example, sodium thiosulphate is an accelerator towards
the ferrous oxalate developer, since it reduces the ferric salt resulting
from the oxidising action of the bromine, the two reactions being
probably as follows:-
3Bг½ + 6FeC2O4 + зK2C2O4 = 3Fе¿(C2O4)3 + 6KBr;
2
and this in presence of the accelerator is followed by-
Fe¿(C₂O4)3 + 2Na2S2O3 = 2FeC2O4 + Na2C2O4 + Na,S406
thus maintaining the strength of the developer. The salt has no
accelerating action towards such developers as hydroquinone, pyro-
gallol, &c. Many other reducing agents have been employed or sug-
gested, such as sodium sulphide, formaldehyde, &c.
Fixing.—The developed negative still contains unaltered sensitive
salt, and the whole of this has to be removed to prevent any further
action on bringing it into the light. This operation is termed fixing.
CHEMISTRY OF PHOTOGRAPHY.
31
The negative is usually treated with a solution of some chemical
which will dissolve out and so remove the remaining silver haloid.
Sodium thiosulphate is most generally used. On treating a plate
with a strong solution of this body, a double salt of silver and sodium
is formed which dissolves readily in water, thus enabling it to be
washed away—
AgBr + Na,S,O= AgNaS,O, + NaBr.
3
Though it appears very simple as thus stated, there are precautions
necessary, for with a weak fixing solution an insoluble double salt
may be formed, Ag,Na (S,O). The solution must therefore not only
be used sufficiently concentrated, but also, in fixing prints, it should
not be used a second time, as the thiosulphate can only take up
a certain proportion of silver before the insoluble body begins to
separate out.
The use of potassium cyanide for fixing purposes also depends upon
the formation of a soluble double salt-
AgCl + 2KCy = AgKCy₂ + KCl.
There is no danger of an insoluble body being precipitated, but this
reagent has the disadvantage of being a powerful poison; moreover,
it cannot be used for fixing gelatino-bromide plates owing to its
solvent action on the gelatine.
Intensifying. A negative which, when fixed, is found to be weak,
that is, wanting in density, due to insufficient deposit of silver, caused
by under-exposure or under-development, has to be intensified or
strengthened. With wet plates this can be done by merely repeating
the development process, that is, by continuing the deposition of
silver upon that already existing. For dry plates, mercuric chloride
is most favoured as an intensifier. On covering the negative with
a solution of mercuric chloride, the silver deposit is bleached with for
mation of silver chloride, and reduction of the mercury salt to white
insoluble mercurous chloride-
2Ag+ 2HgCl₂ = 2AgCl + Hg,Cl₂.
According to Chapman Jones, although the above equation is true, it
is more probable that the chlorides unite to form a double chloride
of silver and mercury-
2Ag + 2HgCl₂ = 2AgHgCl₂.
After washing off the excess of intensifier, treatment with dilute
ammonia gives black mercurous ammonium chloride—
Hg₂Cl₂ + 2NH¸ = Hg₂NH₂Cl + NH₁CI,
adding greatly to the density of the negative.
32
MANUAL OF PHOTOGRAPHY.
Other substances will convert the chloride into a dark compound.
Ammonium sulphide will give an image in silver and mercury
sulphides, or the chlorides may be reduced by ferrous oxalate to
metallic silver and mercury, the addition of mercury to the original
deposit of silver naturally causing an increase in strength, while the
silver may again be utilised to obtain increased density by merely
repeating the treatment. A mixture of lead nitrate and potassium
ferricyanide finds favour as an intensifier. Either lead ferricyanide.
is formed and acts directly upon the metallic silver, producing a
mixture of lead and silver ferrocyanides-
4Ag + 2Pb Fе,Cy₁₂ = Ag₁FeCу6 + 3Pb₂FeCy。 ;
12
or the production of the lead and silver ferrocyanides may be indirect—
2K FeCy12+4Ag=3K,FeCy₁₂+ Ag, FeCy
6
6'
3K₁FeCу + 6Pь(NO3)2=12KNO¸ + 3Pb₂FeCy。 ;
4
subsequent treatment with ammonium sulphide converting them into
the black sulphides. Among the many other ways of utilising (for
intensifying) the ferrocyanide thus formed is treatment with potas-
sium chromate or permanganate.
Another plan of increasing the strength of the negative is to replace
the silver by a metal of greater density, an operation analogous to
toning prints. Gold or platinum would act as follows:
6Ag + 2AuCl3 = 2Au + 6AgCl,
4Ag + PtCl₁ = Pt + 4AgCl.
On the other hand, it is sometimes advantageous to be able to lessen
the density of a negative; this may be done by superficially convert-
ing the silver into a salt, which can be readily removed. Eder takes
a solution of ferric oxalate to which sodium thiosulphate has been
added. The iron-and-silver salt is reduced to silver and ferrous
oxalates-
Ag¿Fe„(C2O4)3 = Ag2C2O4 + 2FeC2O4 ;
the former being at once dissolved out by the thiosulphate in a
manner similar to the fixing of a negative-
Ag2C2O4 + 2Nа¿S₂O3 = 2AgNaS2O3 + Na2C2O4
The ferric oxalate may be replaced by potassium ferricyanide, the
action of which is quite similar, being a reduction of the ferricyanide,
formation of silver ferrocyanide, and solution of this in the thio-
sulphate.
Other methods of reducing intensity are the use of potassium
cyanide, and of a mixture of cupric bromide and sodium chloride,
CHEMISTRY OF PHOTOGRAPHY.
33
which dissolve the silver of the image. Duchoichois recommends
that the negative be soaked in water and then immersed in very
dilute aqua regia, or in a mixture of nitric and hydrobromic acids.
The silver haloid is formed and the plate is then dried and exposed
to diffused light. If the transformation of metallic silver has been
carried too far, the negative can be redeveloped or intensified.
Printing. There are numbers of ways of obtaining a print or
positive image from a finished negative, but the most generally
known is that of silver printing on albumenised paper, in which,
instead of obtaining an invisible image to be afterwards developed,
the action of the light is continued till the alteration in the sensitive
compound is visible, and it only remains to fix the visible picture.
thus obtained, which must, therefore, be formed of the darkened
silver photo-salt, the composition of which is still undetermined.
"Bromide" printing, on the contrary, resembles the making a nega-
tive; a short exposure is given, and the invisible image is developed,
washed, and fixed as in the case of a negative. The reddish colour
of the silver print necessitates toning, the object of which is to give
the print a more pleasing tint. This is usually effected by depositing
finely divided gold upon it by immersion in a bath of gold trichloride.
Gold being a more electro-negative element than silver, the latter
replaces it from solution-
AuCl₂+3Ag=3AgCl + Au ;
but the bulk of the deposited gold results from the readily oxidisable
products of photo-decomposition (which constitute the coloured positive
image) exerting their reducing action upon the gold chloride.
The change of colour varies according as the bath is acid, neutral,
or alkaline. A solution of auric chloride which has been made alkaline
by the addition of borax or other alkaline salt will after a time give
rise to the formation of aurous chloride-
AuCl₂+ 2NaOH = AuCl + NaCl + NaOCl + H₂O,
3
causing the bath to be useless; but its toning power may be restored
by the addition of hydrochloric acid, as this decomposes the hypo-
chlorite, and the chlorine then set free re-oxidises the aurous chloride-
AuCl + NaOCl + 2HCl = AuCl₂ + H₂O + NaCl.
The salt from which toning baths are prepared is the sodium salt of
chloro-auric acid, NaAuCl4 + 2H2O; or it may be regarded as merely
the double chloride of gold and sodium.
That the toning solution must not be acid arises from the neces-
sity of having the gold precipitated as rapidly as possible to ensure its
C
34
MANUAL OF PHOTOGRAPHY.
being deposited in the blue form (that from an acid solution being
reddish), so as to neutralise the objectionable red tint of the altered
silver albuminate; for the colour of the gold, as has been said, varies
with the reaction of the solution, that is, with the rapidity with which
the gold is deposited; and as hydrochloric acid acts as a restrainer, it
is removed as fast as it is formed by adding chalk, borax, &c., as already
mentioned. But it is wrong to suppose that the tone of a print may
be varied at will by the method adopted in toning, for it is impossible
to obtain a print with good contrasts of light and dark from a nega-
tive of inferior quality.
In fixing the toned print by means of sodium thiosulphate, the
action of course is the same as in fixing a negative; but here the for-
mation of the insoluble double thiosulphate must be more carefully
guarded against, as well as the washing away all the soluble salt, for
either will bring about fading, due to decomposition of the thiosul-
phate, if left in the print. Using a sufficiently strong solution of the
fixing agent, followed by thorough washing, is the best way of ensur-
ing permanency, but any traces of thiosulphate which may possibly
remain can be destroyed by treatment with a weak solution of iodine
in potassium iodide-
2 Na2S2O3 + 21 = Na₂SO¸ + 2NaI.
6
The chemical principles of a few of the other many printing pro-
cesses will now be shortly referred to.
Use of Iron Salts. The behaviour of ferrous and ferric chlorides
towards potassium ferri- and ferro-cyanides has been mentioned as
affording means of obtaining a positive or negative according to the
developer employed. When light falls upon paper coated with ferric
chloride, it reduces the salt to ferrous chloride to an extent varying
with the intensity of the light; so that on immersing the paper in a
bath of potassium ferricyanide a blue positive is obtained, since the
ferricyanide and ferrous chloride together form Turnbull's blue-
3FeCl2 + K¿Fе¿Cу12 = Fe₂(Fe₂Cy12) + 6KCl.
But if the bath be made up with potassium ferrocyanide instead, a
deposit of Prussian blue results from the action of the ferric chloride
upon the ferrocyanide,
2FeCl + 3K_FeCy.=Fe (FeCyo)3+I2KC1;
thus the portions unaffected by light are developed as a blue image,
and a negative is the result.
Of the several other ways of obtaining prints by the reduction of
ferric salts by light, may be mentioned Herschel's Chrysotype, where
CHEMISTRY OF PHOTOGRAPHY.
35
the ferrous chloride produces a brown deposit of gold on treatment
with a solution of gold chloride----
3
2AuCl¸ + 6FeCl¿½ = 2Au + 3 Fe₂C¹6·
2
A solution of potassium chromate gives a brown print by reduction
of the CrO, to an insoluble lower oxide, and in Phypson's process
ferrous oxalate formed by photo-reduction of ferric oxalate reduces a
solution of potassium permanganate with production of a brown oxide
of manganese.
The Platinotype process of Willis is the most interesting of those
involving the photo-reduction of iron salts, and it is also very simple.
The paper contains ferric oxalate and potassium chloro-platinite. On
exposure ferrous oxalate is formed--
Fe2(C₂O4)3 = 2 FeC2O4 + 2CO¸
The ferrous oxalate is dissolved by immersion in a bath of potassium
oxalate, the insoluble ferrous oxalate being then converted into a
soluble double oxalate of iron and potassium, which at the moment
of solution reduces the chloroplatinite to metallic platinum-
6FeC₂O4 + 3K₂PtCl₁ = 2Fe2(C2O4)3 + Fe¿Cl¿ + 6KCl + 3Pt.
4
6
Obernetter's process, like the platinotype, obtains its results indirectly,
for the cupric chloride is present in the exposed paper, just as the
potassium chloro-platinite is, but any photo-chemical action they may
undergo is either too slow or unadaptable to obtaining prints. The
paper contains cupric and ferric chlorides; the latter on exposure is
reduced to ferrous chloride, and this in turn reduces the copper salt--
2 CuCl2 + 2FeCl2 = Cu₂Cl₂ + FeCl6.
2
The paper is then immersed in a solution of potassium thiocyanate,
which produces thiocyanate of copper; and this is followed by
treatment with potassium ferricyanide, yielding cupric ferricyanide,
of which the picture is formed. The exposed paper, if left unde-
veloped, is found to lose its latent image by oxidation from the
atmosphere, and the same paper may then be used again upon which
to take a fresh picture.
There are many other printing processes, and bearing in mind the
vast, and continually increasing, number of chemical bodies, so many
of which are readily susceptible to change, it is not surprising that
new processes continue to be devised. For example, the Feer-type,
where the diazo bodies are employed; the Primuline process, and so
on, in all of which the chemistry involved may be surmised with
considerable certainty, as in the case of the older methods; indeed,
it is not in the printing where the difficulties of the subject are met
36
MANUAL OF PHOTOGRAPHY.
with, but in the earlier stages of the production of a photograph,
where authorities begin to differ so widely as to the exact nature of
the reactions, and where the difficulties surrounding their investiga-
tions have still left such a wide field for future experimenters.
In this chapter the writer makes no claim to originality in the
opinions expressed. All he has attempted is to give a general idea
of what are supposed to be the reactions which take place in the
formation of the photographic picture. The writings of the workers
on this subject, Hunt, Abney, Carey Lea, Vogel, Bothamley, Meldola,
and others, have been carefully considered, and, so far as space has
permitted, the conclusions here recorded may be taken as representing
the present state of what is known on the subject. The student is
referred to the works of Meldola, who has perhaps given the subject
more careful consideration than any other living authority, and whose
"Chemistry of Photography" should be specially mentioned as being
the most complete, as well as the recognised, work of reference on the
subject.
CHAPTER III.
OPTICS OF PHOTOGRAPHY.
CC
I. Light.-Light is one of the forms of radiant energy, being
transmitted from place to place by means of transverse vibrations of
the medium ether, which fills the whole of space. This mode of
transmission is known as wave motion," the nature of which is well
illustrated by the progression in water of the disturbance due to an
impulse given to it at any point-e.g., by dropping in a stone-the
disturbance travels onward as an undulation, as a succession of waves,
while the water particles oscillate about their point of rest, but do
not undergo any motion of permanent translation. The distance
from crest to crest of two succeeding waves is the wave-length, differ-
ences in which do not cause any change in velocity of propagation of
a wave of light through the ether.
Although the length of the waves which constitute radiation is
extremely small, being measured in millionths of a millimetre, the
various effects produced by this radiant energy, viz., those of heating,
illumination, and chemical change, are due solely to differences in
wave-length; in other words, heat, light, and actinic rays are not
different things, but a ray of radiant energy possesses the property
of producing thermal, luminous, and actinic effects to an extent
depending upon its wave-length. But, whereas all rays are thermic
to some degree, provided they fall on a suitable surface, it is not all
}

OPTICS OF PHOTOGRAPHY.
37
rays which are capable of producing a luminous or actinic effect.
With sunlight, we find that a length of 600 to Soo millionths of a
millimetre produces the greatest thermal effect; with lengths of 400
to 600 millionths of a millimetre, we get a luminous effect; while a
powerful photographic effect is produced by those rays having wave-
lengths between 200 and 400 millionths of a millimetre. In speak-
ing, therefore, of light rays, it must be understood that what follows
does not refer only to those rays which, by the constitution of the
eye, happen to produce a luminous effect.
But besides differences in wave-length, or distance from crest to
LALANTE
FIG. I.
crest of two succeeding waves, the extent of vibration of the ether
particles-their amplitude-may vary; just as we can imagine the size
or height of sea-waves to vary without altering the distance from one
wave to the next, the hollows and crests being only more marked.
Now, since this is caused by the particles moving to a greater distance
from their position of rest, they must possess greater energy or be
capable of doing more work; in other words, increase in amplitude
causes increase in intensity, and many photographic and other pheno-
mena are dependent upon, and can be explained by, differences in the
intensity of the vibrations.
38
MANUAL OF PHOTOGRAPHY.
Rays of light travel in straight lines. To this fact is due the pro-
duction of a shadow identical in form with any object placed in the
path of light. The pin-hole camera is also dependent upon the prin-
ciple of the rectilinear propagation of light; for, taking any small hole
in a shutter, then, since each point of a luminous object causes light
rays to travel in every direction from it in straight lines, each point
can only send a ray to a corresponding point upon a screen placed
behind the hole, all rays from other points being cut off by the shutter.
This is shown in Fig. 1, where a single ray from each point of the
luminous object is seen to produce an image which must necessarily
correspond in colour and intensity to that of the object from which it
came, and of which the whole, therefore, forms a reproduction.
Only a few bodies are self-luminous, the majority being visible.
because they reflect light received from other sources; part of this
they absorb, part is scattered; with transparent bodies part is trans-
mitted, the remaining portion being reflected and producing the im-
pression of the object from which they come. The extent to which
light is reflected depends on the regularity or polish of the reflecting.
surface, on its colour, and on the angle of incidence. Instruments
with a highly polished surface are employed as mirrors, and their use
in photography is mainly to reflect the sun's rays (see Solar Camera),
and for reversing an image (see Reversing).
But when light has to travel through space occupied by substances.
besides ether, the properties of the ether are modified within the sub-
stance; in transparent bodies it has suffered but little modification,
while opaque bodies are those in which its properties have been so
modified that it is no longer able to transmit the undulations which
form light rays.
The most important effect produced by transparent substances is
that of retardation, the extent of which change also depends upon the
wave-length of the ray; consequently, a ray falling upon a transparent
substance at an angle has its direction changed within the substance
(or, in other words, is refracted) to an extent depending upon the
velocity of the ray within the body and upon the substance itself, e.g.,
its density, as illustrated in Fig. 2, where
the ray a a has its direction changed on
entering the layers, b, c, d, of substances
differing in density. The ratio of the
velocity of light in free space to its velo-
city within the substance is the index of
refraction of the substance. But since
velocity depends upon wave-length, we
have a means of separating rays of light
differing in wave-length. A pencil of rays (a beam of white light)

FIG. 2.
C
d
OPTICS OF PHOTOGRAPHY.
39
falling upon one side of a prism of glass will be bent from its direct
route (see Fig. 3), and we get an elongated band of coloured light, a
spectrum, each point in the band corresponding to a ray of a certain
wave-length, determined by the amount of deviation, that is, its re-
frangibility.
The amount of separation or difference in deviation between two
given points in the coloured band measures the dispersion of a prism,

Violet.
Indigo.
Blue.
Green.
Yellow.
Orange.
Red.
FIG. 3.
but its dispersive power is the ratio of this dispersion to the deviation
of some particular ray selected for reference.
As already stated, light rays may produce three distinct effects; one
of which, that of heating, is, however, common to all. The following
interesting experiment enables us by the use of the spectrum to show
that it is only those rays having actinic properties which produce any
photographic effect. If by means of a prism and a strong light, such
as the electric or lime-light, or better still the light from the sun (but
the experiment has succeeded perfectly with the limelight, and may
be most conveniently repeated by this means), a beam of light be
spread out as a spectrum of all the colours, it will be found that if a
negative in contact with a gelatine plate be exposed in the blue rays
a picture may be printed, but if exposed in the red rays no result will
be produced. The experiment may be shown on one plate by first
exposing one half in the blue and the other half in the red rays. On
developing the plate, one half will be found blank, while the other
will show half of the image.
II. Lenses.-A lens is a piece of transparent substance, usually
glass, bounded by two surfaces which are generally portions of spheres.
The relative direction of curvature of the two surfaces divides lenses
into two classes: (1) converging, (2) diverging lenses. In each class
one of the surfaces may become plane, and we then get a plano-con-
vex (No. 1) or plano-concave lens (No. 4). The six forms are repre-
sented in Fig. 4. No. 2 is biconvex, No. 5 biconcave, while Nos. 3
and 4 are called a converging and a diverging meniscus respectively.
The line joining the centres of curvature of the lens surfaces, or
40
MANUAL OF PHOTOGRAPHY.
drawn through the centre of curvature perpendicular to the plane
surface, is the principal axis of the lens, and a point distant from the
two surfaces in the ratio of their radii of curvature is the optical
centre, all rays passing through which emerge parallel to their original
direction, i.e., undergo no deviation. In a meniscus this point will
3
4
5
FIG. 4.
lie outside the lens, and with plano-convex or plano-concave lenses it
must be on the curved surface. The principal axis necessarily passes
through the optical centre, and any other line passing through this
point is a secondary axis.
Neglecting for the
FIG. 5.
present the influence which differences in
wave-length has upon refrangibility, it has
already been stated that light in passing
through a prism is deviated to an extent
depending upon the angle of incidence.
Lenses produce the same effect; indeed, a
lens may be looked upon as a series of
prisms; a convergent lens being two prisms
united at the base (see Fig. 5), and a divergent
one two prisms united at their summits.
The Working Aperture of a lens used
without either diaphragm or stop is, of course,
its full diameter; when otherwise employed,
its working aperture depends upon the aper-
ture of the diaphragm or stop in use, being identical with the diameter
of a stop, but by no means the same as that of a diaphragm. This
distinction between working aperture of a lens and diameter of
diaphragm is shown in Fig. 6; which also illustrates the way in

Ja
D
FIG. 6.
ture of the lens is measured by a' b'.
which the former is deter-
mined. F is the principal.
focus of the lens L, D is a
F diaphragm placed behind (as
with the front lens of a
doublet); then, while a b
measures the diameter of this
diaphragm, the working aper-

The Angular Aperture of a lens is the relation between its focal
OPTICS OF PHOTOGRAPHY.
4I
length and working aperture; the former being a constant, it follows
that angular aperture is diminished by the use of a smaller diaphragm.
Angle of View is the relation between the focal length of a lens
and the width of plate upon which it can produce an image, so that
of two lenses that with the shorter focal length has (other things
being equal) the greater angle of view. Increased width of angle of
view is secured by the use of a smaller stop, but this is accompanied
by loss of rapidity. It is not advisable for general work to use a
lens which includes an angle greater than the angle of view of the
eye, which may be taken to be within 50°.
The angle of view may be ascertained in the following way :
Upon a sheet of paper draw a line equal to the length of the plate;
that is, ten inches for a 10 × 8 plate. Find the centre of this line
from it draw a perpendicular equal to the length of focus of the lens
to be tested. By joining the three points forming the extremities of
these two lines an isosceles triangle is formed having the length of the
plate as base. The vertical angle of this triangle is the angle of view
required, and may be measured by applying a protractor.
Rapidity is a term which refers to the greater or less time of
exposure which the use of the lens requires in order to allow the
transmitted light to produce a sufficient photographic effect upon the
sensitive plate. Rapidity will, therefore, vary with the intensity of
illumination, which depends upon the working aperture of the lens.
The rapidity of a lens, in fact, is the relation between its working
aperture and focal length; in other words, it depends upon the
angular aperture, which explains the necessity for using a large
angular aperture in instantaneous work. It is evident, then, that
what is gained in rapidity is lost in depth of focus and fineness of
definition. The rapidity of all objectives is taken to be the same when
used with diaphragms the sizes of which are the same proportion of
the respective focal lengths, but in reality this is only true when
comparing single lenses.
III. Focus.-(a.) Definitions and Formula.-Rays parallel to the
principal axis of a convergent lens are deviated in such a manner as
to all meet at a point on this axis on the other side of the lens; this
is the principal focus. Rays which are not parallel, but diverge from
a point on any axis, will, after passing through the lens, converge
to a second point on that axis; the two points related in this way
are conjugate foci. With a concave lens which causes light rays to
increase their divergence the rays necessarily do not meet at a point,
but they appear to diverge now from a new position, where they form
a virtual image. The equivalent focus of a lens-combination is the
focal length of the simple lens which will produce an image of a
distant object of the same size as that produced by the combination
42
MANUAL OF PHOTOGRAPHY.
the image must be small and central to ensure absence of distortion.
As the point from which the focal length is measured is the optical
centre, and this centre is situated somewhere between the lenses of
the combination, it is customary, and near enough, to take this point
at the diaphragm. A rough estimate of focal length can thus be
formed by measuring the distance between the diaphragm and ground
glass when some object over 200 yards away is focussed upon the
glass, for the rays from the object will be practically parallel, and
consequently form their image at the principal focus.
The distance of the principal focus of a lens from its optical centre
is its focal length. A convex lens has a negative focal length, since
the image it forms is on the opposite side of the lens to the object.
The focal length of a concave lens is, on the contrary, positive, since
object and image (virtual) are on the same side of the lens. If we
measure the distances of object and image from the lens and call
them p and p', the focal length ƒ is given by the formula
I 1
||
I
ƒ p' P;
distances on the opposite side of the lens to the object being negative,
the focal length of a concave lens cannot be measured directly in this
way since it forms no real image from which to measure.
(b.) Determination of Focal Length. Evidently from the above
formula, knowing the value of ƒ for a lens or combination of lenses,
and the distance, p, of the object from the lens, we can calculate the
distance p' at which the image will be formed on the ground glass.
Or, by measuring p and p', we can find by its means the focal length
of a lens. An easier method of doing this (which requires no cal-
culation) is to arrange any suitable object (such as a foot-rule) and
obtain the image of a small portion centrally on the ground glass and of
exactly the same size as the object; the object and image will now be
distant from one another exactly four times the focal length of the
lens, which is, therefore, found by measuring this distance and
<dividing by 4. As has already been said, in finding the focal
length of a combination, it is necessary to measure from a point
situated between the lenses. This point will be in the middle or
nearer the front or back lens, according to their relative strength. In
a portrait combination, for example, the optical centre is rather nearer
to the front than to the back lens.
But the method generally recommended for finding focal length is
that devised by Grubb, which is simple and accurate. Draw two
vertical pencil lines upon the ground glass of the camera at equal
distances from the margin at each side and about 4 inches apart;
OPTICS OF PHOTOGRAPHY.
43
place the camera upon a sheet of white paper on a table fronting a
window; then focus some distant object, say 200 yards away, to coin-
cide with one of the vertical pencil lines; draw a line upon the paper
along the side of the camera; then turn the camera so that the object
shall coincide with the other line on the ground glass, and draw a
second line on the paper along the side of the camera. Suppose in
Fig. 7, AB and CD are the two lines thus drawn on the paper; pro-
long them with a ruler till they meet; let E be the point where they
meet. Across these lines draw the line GH equal in length to the
distance between the
pencil lines on the
ground glass, and in
such a direction as
to make the triangle

isosceles, i.e., making
EG = EH (as near as
A
K
B
E
C
H
D
FIG. 7.
practicable). Bisect GH in K and join EK; then the length of EK
is equal to the focal length (the equivalent focus) of the camera-
objective.
1
(c.) Size of Image. The size of the image is to that of the object
in the ratio of their distances from the lens, i.e., as p' is to p: thus,
with the object 20 feet away and focussed on the ground glass I fout
behind the objective, the image will be th the size of the object.
As we often require to reduce or enlarge a picture a certain number
of times with a lens of which we know the focal length, it is impor-
tant to be able to find, at least approximately, where the picture and
focussing screen should be placed in order to obtain the required
reduction or enlargement. This is effected by means of the table given
on another page with an explanation as to method of using; but it might
be added that this table has been deduced by means of the formulæ
U = (n + i) f
(n
f
V = ƒ +
N
where ƒ is the focal length of the lens, n is the number of times the
picture is to be reduced or enlarged, and U and V the required dis-
tances at which picture and ground glass are to be placed from the
lens. It must of course be remembered that U and V give the dis-
tance of object and image to produce a reduced picture and vice versâ
for an enlargement.
(d.) Depth of Focus is the power of a lens to give clear images of
44
MANUAL OF PHOTOGRAPHY.
objects in planes at different distances from the lens, thus enabling
α
KI
the ground glass to be moved to a limited
extent without impairing the sharpness.
The depth of focus varies inversely as
its aperture, and is greater for objects at
greater distances from the lens. This
effect of aperture and relative distance
is explained by the figures. In Fig. 8 a
very slight movement of the ground glass, a b, would put the point c
out of focus and produce a broad circle; whereas, in Fig. 9, the angle

FIG. 8.
H
b
FIG. 9.
being so much less,
moving a b would not
produce so great a
change in definition ;
and at a' b' it could be
still more moved to
or from the lens, and
yet a sharp image be
maintained.

This effect is not a contradiction of the law of conjugate foci, for
the focussing at the same point of objects in different planes depends
upon their being sufficiently distant, so that their image is formed
near the principal focus.
Among simple lenses depth of focus is greatest for a convergent
meniscus with its concave face towards the object, and for a small
angle a practically flat field is obtained. With combinations the
orthoscopic has the greatest, and the double combination the least
depth of focus; this difference being due to the second lens in the
former causing the rays emergent from the lens facing the object
to be less convergent, while the back lens of the latter renders them
more convergent.
IV. Defects in Lenses.-The statements as to foci are not
rigorously true in practice, as lenses are subject to the defects
called Aberrations.
(a.) Spherical Aberration is so named from being due to the

R.
V
V
R-
a
FIG. 10.
spherical shape of the lens surfaces, which causes the rays r, r,
passing through the margin of a lens to converge to a point different
OPTICS OF PHOTOGRAPHY.
45
to that at which rays meet when refracted through the central por-
tion, as illustrated in Fig. 10, while a is the circle of least aberration, as
is the smallest area which includes all the refracted rays. This
effect increases as the curvature of the surfaces increases, and is there-
fore less for a given focal length with a lens of greater refractive index.
The spherical aberration of a single lens can be nearly overcome
by the use of a diaphragm placed at such a distance in front of the
lens as to cause the image to be formed at the centre by rays passing
through the centre only, and the outer portions of the image by rays
passing through the margin of the lens obliquely through the dia-
phragm, as in Fig. 11, all those rays
which (as the previous figure shows)
would render the image indistinct
being now cut off. A meniscus lens
used in this way gives the flattest
field; but a plano-convex permits
of the use of a larger aperture, and

FIG. II.
is thus preferable where the angle of view is limited and rapidity
is required.
The other method of destroying spherical aberration is by the use
of a second lens to produce a contrary effect. A divergent lens is
associated with a convergent, and vice versâ, in such a way that the
associated lens brings the marginal rays to the same point as the
central rays. In thus correcting spherical aberration, the second de-
fect in lenses, chromatic aberration, is also corrected; therefore, the
two associated lenses must be of glass of different kinds; further,
chromatic aberration being the more important, spherical aberration
is often over-corrected, and the combination has negative spherical
aberration, the marginal rays focussing to a point farther away than
the central rays, or it may be insufficiently corrected and have positive
spherical aberration, the marginal rays having the nearer focus.
Objectives corrected for spherical aberration, so that they may be
employed with their entire aperture, are aplanatic. A non-aplanatic
lens produces only confused images if used with its full aperture.
(b.) Chromatic Aberration is a necessary consequence of the
refrangibility varying with wave-length, for the red and violet rays.
will be brought to a focus at different points; thus the image of a
point is not sharp, but surrounded by rings of colour. Besides,
as some rays exceed others in luminous effect, and others, again,
have greater actinic power, the focus for the visual rays (i.e., the
focus as judged by the eye) will not be true for the actinic or
chemical focus (ie., for the rays which produce the photographic
effect).
A diaphragm is here of no practical use, and chromatic aberration
46
MANUAL OF PHOTOGRAPHY.
must be corrected by combining suitable lenses, made of material
with different dispersive powers. The convergent lens is usually
crown glass, and the divergent lens flint glass, the two being cemented
together face to face. Still, a lens achromatic for two central rays
of a certain wave-length (i.e., a lens which brings them to a focus at
the same point) will not be achromatic for marginal or oblique rays, nor
for those having refrangibility different from the two selected rays;
combinations are, therefore, made so as to bring the most luminous
and most chemically active rays to the same focus, thus ensuring that
the photographically produced image will equal in sharpness that as
judged by the eye. But though the visual and chemical foci may
be coincident at the centre of the ground glass, they will not be so
at the margin, where there will be what is called a chemical focus;
and though the image will appear sharp all over, the photographic
reproduction will not be sharp at the margin.
Chromatic aberration may be over- or under-corrected, as is the
case with spherical aberration. When over-corrected, the chemical
focus is farther from the lens than the visual focus, and vice verså
when under-corrected; experiment will soon show the difference
between the two foci, and the ground glass can then, after focussing,
be pulled out or pushed in to this extent to place it at the chemical
focus. (See Focimeter.)
(c.) Aberration of Form of Image, called also Curvature of Field,
means that the image formed by a lens does not lie upon a plane, but
on a curved surface; thus any number of points A, B, C (Fig. 12),
all in one plane and so far away as to be practically equidistant

A
C
D
α
a
A
α'
a
B
Co
A
B
FIG. 12.
α
D'V
OPTICS OF PHOTOGRAPHY.
47
from the lens, will form images a D D' at a distance from the optical
centre nearly equal to the focal length; the images will therefore lie
on a curved field as shown in the figure; and the photographic plate
being a plane surface, cannot receive a sharp image over its whole
area at the same time.
(d.) Flatness of Field.—It is evident that a portrait lens constructed
to give good definition for a sitting figure would not be equally well
adapted for taking a standing figure. Before the introduction of
quick plates lenses of large aperture were necessary, and the requisite
flatness of field and depth of focus could not be obtained with the
same lens without the use of diaphragms; therefore the curves of
the lens had to be adapted for the purpose, and "flatness of field"
was one of the requirements when good definition of a figure in a
standing position was desired. As lenses of the rectilinear type are
now often used in place of those specially constructed for portraits,
and as the quickness of the processes now employed permits the use
of diaphragms, the defects of the older forms of lenses may be
avoided.
Referring to Fig. 9, we see that a stop will, to a certain extent,
overcome curvature of field,

since it increases the depth
of focus; thus in Fig. 13 the
ground glass could be moved
to somewhere behind f, g, and
in front of e without sensibly
impairing the definition of e,
19
FIG. 13.
but at the same time bringing a greater number of points of the
curved image upon the ground glass. The effect, however, is small
compared with the amount
of curvature, so that a com-
bination of lenses must be
used together with a dia-
phragm.

Take the case of a simple
convergent meniscus, used
with a diaphragm; direct
and oblique parallel rays.
focus on a curved surface,
since the marginal rays
have a smaller focal length
than central rays; but
FIG. 14.
with a divergent lens the marginal rays will have the greater focal
length and the curvature of field is reversed; therefore, by a com-
bination of a positive with a negative lens the two effects can be
48
MANUAL OF PHOTOGRAPHY.
neutralised; and, since the same association is used to produce achro-
matism, it is possible to so select the two lenses and the position of
the diaphragm as to obtain flatness of field as well as securing achro-
matism; but, as with spherical and chromatic aberration, there may
be under- or over-correction, so we can have negative aberration of
form with a convergent and positive with a divergent combination
(Fig. 14). Although a comparatively flat field can be obtained with
single achromatic combinations, the greatest flatness has been secured
by associating a convergent with a divergent achromatic lens at a suit-
able distance apart.

1
FIG. 15.
The orthoscopic and triplet lenses are thus arranged, as will be ex-
plained in the description of these objectives.
(e.) Distortion.-Any departure from the rules of perspective of
an image formed by a lens is called distortion. As the lens varies in
thickness, being thickest at the margins or at the centre in divergent
and convergent lenses respectively, the refraction of a ray will be
greater or less according as it falls nearer to or farther from the mar-
gin, or vice versa; so that the distortion which this produces has been
called Aberration of Thickness.
The effect consists either in the curvature of the images of straight
lines produced by marginal rays causing barrel-shaped or "pincushion
distortion" (Figs. 16a and 166), or in the exaggeration of certain objects
with respect to others. As these defects are most apparent in the
reproduction of buildings and similar rectilinear objects, a single achro-
matic lens is sometimes known as a landscape lens, from the work for
which it is most suited.
With the simple objective the direction of distortion is altered
according as the diaphragm is before or behind the lens (as is shown
in the figures above); so that by placing the diaphragm between two
similar simple lenses their distortion neutralises each other; and we
get straight lines as images of straight lines, e.g., globe-lens, periscopic ;
a single simple lens will also give an image free from distortion pro-
vided it is merely a reproduction of the same size as the object.
OPTICS OF PHOTOGRAPHY.
49
The distance of the diaphragm from the lens must also influence
the amount of distortion, since the nearer it is to the lens the nearer
do the rays pass through the centre, and, therefore, the less is the
aberration due to differences in its thickness, until, when used as a
stop, there is no distortion.
Distortion can also be remedied by using a third and divergent lens,
as negative and positive lenses produce opposite effects (e.g., Sutton's
triplet, Dallmeyer's triplet and rectilinear, &c.).
(f.) Astigmation is a defect most general in portrait lenses, and
refers to the impossibility of focussing at the same time vertical and
horizontal lines, the rays from which pass obliquely through the lens
this is because a lens has two focal lengths in perpendicular planes
for rays passing obliquely through it; e.g., a point cannot be focussed
as a point when, viewed through the margin of the lens, we get in one
;

FIG. 16α.

FIG. 166.
position a line, the primary focal line, and by moving the ground
glass a line is obtained, the secondary focal line, which is perpendicular
to the primary.
Astigmation cannot be entirely removed; so it has to be reduced to
a minimum by the use of the diaphragm, which acts in the usual
manner by dividing the lens into as many separate lenses as there are
radiating points of different incidence.
V. Objectives.-The irregularities of refraction, extent of depth
of definition, and other optical peculiarities to which lenses are subject,
necessitate the use of particular combinations for special purposes;
for this reason a lens is frequently known by a name signifying the
photographic uses to which it is adapted. We thus have landscape
lenses, portrait and copying lenses.
(a.) Landscape Lenses.-The special requirements of a lens for
landscape uses depends upon whether the view to be reproduced
D
50
MANUAL OF PHOTOGRAPHY.
contains living figures or not; whether it is of animate or inani-
mate nature; and also upon the relative size and nearness of any
buildings which may be included within the picture; besides these,
there is the consideration as to the size of plate the lens will cover,
i.e., its angle of view.
The Single Achromatic Objective is a meniscus composed of two
lenses, a flint-glass lens cemented to one of crown-glass, in which,
with the exception of the Ross view lens (Fig. 17, 2), the convex
side of the meniscus is turned towards the ground glass (Fig. 17, 2).
The flatter the lenses the greater the rapidity obtained, as a dia-
phragm with larger aperture may be used; with the deeper forms the
diaphragm can be placed farther back, thus including a wider angle,
producing less distortion, and yielding a picture covering a wider
area, but the definition is impaired owing to the field being less flat.
Dallmeyer's single landscape lens (fig. 17, 3)
has the flint meniscus placed between two
crown-glass lenses, the whole forming a slight
meniscus, turned, as usual, with its concave
surface towards the object. It includes a large
angle; but, as with all non-aplanatic combina-
tions, it requires a very small diaphragm; hence it is most suited for
landscapes without figures. One advantage of this lens is the absence.
of the luminous spot or flare upon the focussing screen, caused it
may be by the lens surfaces acting as reflectors where the light is not
transmitted nearly normal to the refracting surfaces, or by reflection
from the bright edges of the lenses or diaphragm.
Steinheil's Periscopic Lens consists of two meniscus crown-glass
FIG. 17.
FIG. 18.
3
lenses (Fig. 18) having the convex surfaces outwards
and a diaphragm midway between them. It is
symmetrical, non-achromatic, and non-aplanatic.
The correction for the chemical focus is made by
advancing the plate, before exposure, byth of the
focal length of the lens. It requires very small
diaphragms, and is but little used.
The Globe Lens is another non-aplanatic sym-
metrical objective. It is free from distortion, has
no chemical focus, and includes a very large angle.
Its name is taken from its globular shape, the two
deep meniscus lenses being achromatised by concavo-convex flint-
glass lenses forming portions of the same sphere (Fig. 19). Its great
spherical aberration requires the use of a very small diaphragm, so
that it is only available for inanimate landscapes, architectural repro-
ductions, &c.; but, as regards the first, the long exposure produces
solarising, and there is always an absence of cloud effects.

OPTICS OF PHOTOGRAPHY.
51
Sutton's Panoramic Lens, like the above, has a globular outline, and
is formed of two concavo-convex spherically curved lenses with water
in the hollow between them (Fig. 20). It is symmetrical, non-aplanatic,
but achromatic. The fact that the picture is entirely formed by axial
rays, which fall normally upon the plate, causes it to produce a pano-
ramic picture, each portion of which is correctly seen only when
brought directly opposite the eye. But as it requires the use of
curved plates, it can never be of general utility.


O
FIG. 19.
FIG. 20.
The Orthoscopic Lens.-Unlike the four combinations just de-
scribed, this is aplanatic. Its composition is a front achromatic.
meniscus lens with the convex side towards the object, and formed,
like the portrait combination, of a biconvex crown-glass lens cemented
to a biconcave lens of flint-glass (Fig. 21).
The back lens, which is smaller and placed
very near the front, contains a biconcave
crown-glass and a flint-glass meniscus, with
its concavity towards the crown-glass lens;
thus the two cannot be cemented together.
The back combination lengthens the focus
considerably, and enables it to cover a much
larger plate. The orthoscopic lens can be used
with a large aperture, and very great sharpness
can be obtained. Lack of freedom from distortion prevents its use
for architectural reproductions, engravings, &c. ; but its rapidity and
intensity of definition makes it suitable for outdoor groups, while
portraits may be taken with it in a very good light. It does not
include a wide angle, and when such a view is required the single
landscape lens is to be preferred.

f
FIG. 21.
Steinheil's Aplanatic Lens consists of two cemented achromatic
meniscus lenses all composed of flint-glass (Fig. 22). Its aperture is
; and it is, therefore, very rapid and useful for outdoor
portraits, groups, &c. It is symmetrical. There is also a wide angle
aplanatic.
as much as
7
52
MANUAL OF PHOTOGRAPHY.
Doublets.-A doublet consists of two combinations, which mutually
neutralise distortion, and with a diaphragm
placed between them. Some of the lenses
already described are doublets. When the
two lenses of the doublet are similar, they
form a symmetrical combination; when dis-
similar, an unsymmetrical.

FIG. 22.
1
Goddard's lenses have a deep meniscus.
In his combination landscape lens it is behind
a biconcave crown-glass, forming the back lens.
His double periscopic has the meniscus touching a front combination of
a biconvex crown-glass lens, cemented to one of bi-concave flint-glass.
Ross's Wide-Angle Doublet (Fig. 23) is non-aplanatic. It in-
cludes as wide a field of view as any, with equal freedom from
distortion and flare, and with equal definition. Each lens is an achro-
matic meniscus, and the two are of nearly equal focal length. It
includes an angle of at least 80°, and has less spherical aberration
than the globe lens. Its great utility is as a view-lens and for photo-
graphing buildings at short distances, owing
to its freedom from distortion.
rected for astigmation; but as the large
field of view covered requires a diaphragm
of small aperture, it cannot be used for
anything but inanimate nature.
H

FIG. 23.
It is cor-
Ross's Instantaneous Doublet is also non-
aplanatic. It includes a very much smaller
angle, allowing a correspondingly larger aper-
ture to be employed, and thus acts with
great rapidity. The lenses are farther apart than in the wide-
angle lens, as it is intended to define sharply with a larger aperture.
As smaller diaphragms can be employed, so as to include an average
and sufficient angle of view, this lens is the more generally useful
of the two. It is also an excellent lens for copying purposes.
Dallmeyer's Wide-Angle Rectilinear (Fig. 24) includes almost as
much as 100°. The front lens has a longer
focus than the back, and also a greater
diameter, distortion being corrected by plac-
ing the diaphragm nearer the back lens. It
must not be forgotten, however, that in any
lens including a very wide angle consider-
able skill and judgment is necessary to pro-
duce anything of artistic value.
()

FIG. 24.
Dallmeyer's Rapid Rectilinear (Fig. 25),
like the former "Rectilinear," and unlike
the other doublets, has both its flint-glasses on the outside. The
OPTICS OF PHOTOGRAPHY.
53
crown-glass meniscus is cemented to the flint-glass lens by its convex
surface. This lens is aplanatic, and, giving
sharp definition without a diaphragm, works
with great rapidity. It can be used to include
a sufficiently large angle by taking a smaller
diaphragm, and is also very useful as a copying
lens. With gelatino-bromide plates and in a
good light this form of lens may be used for
portraits.

FIG. 25.
Triplets are composed of three combinations of lenses, and include
those of Sutton, Goddard, Ross, and Dallmeyer. Sutton's Symmetrical
Triplet was the first view-lens constructed free from distortion. The
use of a triplet is not so general as formerly, as many of its advantages
are now included in the more simple, and therefore less expensive,
doublets; but its power of use with a large aperture still makes it of
value for photographing animate nature, groups, &c., being in this
respect much superior to the orthoscopic.
Dallmeyer's Triple Achromatic Lens (Fig. 26) has an achromatic
convergent meniscus at both back and front, formed of a biconcave
flint-glass lens cemented to a biconvex
crown-glass lens; the back combination
has the greater diameter and longer focus,
and the concave face of each is directed
towards the centre of the combination.
Between these two lenses is the third; it
is nearer the front lens and has its con-
vex surface towards it. It is also an achro-
matic meniscus, but divergent, and is com-
posed of a biconvex flint-glass lens cemented
to a biconcave crown-glass lens. The dia-
phragm is introduced just in front of the centre lens. It is aplanatic,
and free from both flare and distortion. With full aperture it can be
used for groups and instantaneous pictures; and, when time is unim-
portant, greater depth of focus will of course be secured by the use
of smaller diaphragms. The triplet is an excellent copying lens,
and for enlargements is reversed, so as to place its largest lens
facing the object to be enlarged. But it does not surpass the doublets
and rectilinears for this purpose. The triplet of Ross has plano-
convex and plano-concave lenses in place of the weak meniscus in the
objective.

FIG. 26.
(b.) Portrait-Lenses, from the use made of them, require to be
rapid; and must, therefore, be used with a large diaphragm; they
only include a small angle of view. Though the axis of the objective
may be capable of being slightly inclined, any departure from a truly
54
MANUAL OF PHOTOGRAPHY.
horizontal position should only be resorted to under exceptional cir-
cumstances, as it will not cause so great a deformation when the
objective has a long focus. In general the axis of the objective.
should be kept horizontal. Portrait-lenses of the present day are
almost all made on the pattern of the original objective devised by
M. Petzval.
The Double Portrait-Lens (Fig. 27) consists of an achromatic
meniscus or nearly plano-convex cemented front combination with a
biconvex back combination com-
posed of a divergent meniscus of
flint-glass at a short distance from
a biconvex crown glass lens.

FIG. 27.
The diaphragm is placed be-
tween the two combinations, the
front one of which is usually
slightly the smaller. Dallmeyer
constructs a portrait-lens (Fig. 28)
which has a meniscus for the
back lens composed of a flint-
glass diverging meniscus next the ground glass and a crown-glass
meniscus slightly separated from it, and an arrangement by which the
two lenses of the back combination may
be further separated allows any desired
degree of want of sharpness to be obtained
by the introduction of spherical aberration.

1
FIG. 28.
The use of these lenses in portraiture
depends upon their comparative rapidity
f
with a diaphragm of at least aperture.
8
distortion, pro-
By the use of
They have but little astigmation, and are free from
vided the diaphragm is placed between the lenses.
smaller diaphragms the same lenses may be used for groups, say with
or for landscapes, with to
ƒ
f
20 30
aperture
f
16;
The use of the triplet, orthoscopic, and rectilinear for taking por-
traits has already been referred to in the description of these lenses.
It now only remains to be said, that as regards the camera in which
the photographic objectives are used, its axis may, in landscape-work,
be inclined up or down, the absence of uniform straight lines causing
any deformation of image to be imperceptible. On the other hand,
when buildings are present, or when a building is to be reproduced
photographically, the camera must be kept strictly horizontal, any
departure from which will produce an effect which can only be
LIGHT IN PHOTOGRAPHY.
55
Also the dis-
corrected by using a camera with a Swing-back.
tortion given by the orthoscopic and single objectives makes them
unsuited to this kind of work. Lastly, in copying engravings,
maps, &c., the camera must not only be kept horizontal, but the
object to be copied must also be vertical and the image symmetrically
placed upon the ground glass. The lens most suitable for copying is
the rectilinear.
CHAPTER IV.
LIGHT IN PHOTOGRAPHY.
UNDER the heading Developing and Developers will be found an
account of experiments by M. Moser and others on the peculiarities
of the action of light. The question which a photographer generally
has to consider is—whether the light is good or bad, as upon the one
or the other will depend the result of his work. He does not, as a
rule, concern himself as to the qualities which light possesses, or
whether the true theory is the corpuscular or the undulatory. He
knows that if he is using a collodion plate, a certain amount of yellow
light in the room he is working in will not injure his picture; but, on
the other hand, if he is using gelatine plates, he is aware that if the
light is not of a certain quality, his work will be "fogged;" and
further, that, with very sensitive plates, he must use still greater care
to exclude the actinic rays.
This is not, however, the place for a treatise on light, and the reader
is referred to works specially devoted to the subject, such as Hunt's
"Researches on Light." It is well to remember that light acts in
"inverse proportion to the square of the distance from its source.”
This is correct as to light generally, but it will be more readily
noticed when working with artificial light. (See also Optics of
Photography.)
Electric Light.-Various methods may be adopted for producing
the electric light for photographic purposes. The voltaic battery,
necessitating the use of acids, zinc, and cells, is not only troublesome,
but costly. Next we may use storage batteries. This also is costly,
as many batteries would be required for a large light; and to this
must be added the cost of charging. When required as a substitute
for daylight in dull weather, a complete installation for the production
of the electric light is desirable, and in the dynamo, driven by a gas-
engine, we have the most convenient method. In situations where a
steam-engine could be used, that method of producing the power
should, perhaps, be preferred. But a gas-engine can be erected in
56
MANUAL OF PHOTOGRAPHY.
situations where a steam-engine could not be, and it has the advan
tage that the power can be brought into use in the course of a few
minutes. The dynamo may produce the current in the alternating or
direct way.
When it is desirable to keep the light quite central, the
alternating machine is preferable, as, for instance, when optical
B
M
FIG. 29.
appliances are used in
enlarging; but for most
purposes in photography
the direct-current ma-
chine is most suitable.
In this machine the
point of light is con-
stantly falling as the
carbons are consumed,
the top carbon burning
twice as fast as the
bottom one, but this is
of very little conse-
quence. There are many
kinds of dynamo in use
-one of several forms
invented by Mr. Henry
Wilde, F.R.S., is shown
in Fig. 29. Mr. Wilde

was not only the inven-
tor of the dynamo, but
was the discoverer of the principle by which quantities of electricity
and magnetism indefinitely large were induced from quantities inde-
finitely small, and it is this principle which makes the electric light.
practicable for illuminating purposes. Some of the earliest experi-
ments with the light for photographic use were made by Mr. Wilde.
It is perhaps needless to say that with any kind of dynamo of suffi-
cient power a light suitable for photography may be obtained; but the
writer, in what follows, speaks from experience with a machine made
by Messrs. Crompton & Co. of Chelmsford. The light is used for
copying and sometimes for printing. The engine for producing the
power is of the "Otto" form, vertical, of 2 horse-power nominal,
or about 3 or 3 actual. It runs at about 170 revolutions per minute,
and this from the fly-wheel of 4 feet diameter on the 6-inch pulley
of the dynamo gives a speed of about 1350 revolutions per minute,
and this power is said to give from the lamp burning carbons of
13 mm. a light of 2000 candles; but whether the light be 1000
or 2000 candle-power, the effect produced is adequate to enable
copies to be made with sufficient rapidity. To specify the number
LIGHT IN PHOTOGRAPHY.
57
of minutes required for exposures would be useless, as the time
varies from many causes, such as the lens and stop used and the
distance of the object from the light; it may, however, be said that
the electric light is many times quicker than ordinary daylight in the
winter-time.
The light must of course be used naked-that is, without the opal
or other glass globe; but as pieces of hot carbon are apt to fly off,
some kind of protection should be adopted. This may be made of
tin or zinc, and may be suspended from the lamp; the bottom of the
shield will collect much of the dust from the burning carbons; the
back acts as a protection to the eyes; and the inside may be white-
washed so as to form a reflector. The carbons should be adjusted
so that the crater burns as shown in Fig. 30. This has the effect of
throwing the light in the direction required.

16
As much of
FIG. 30.
the effectiveness of the light depends on this adjustment,
some care should be taken to have it right. As to the
distance apart of the carbons, the most effective light is
obtained when the distance is about 3ths of an inch. When
the current is too strong, an arc of inch or more may be formed,
and at the same time a less effective light. By lowering the
speed of the engine the proper arc may be maintained; but
when the lamp is once adjusted it should not be altered; the
slight variation in the speed of the dynamo is not of much
consequence. It is chiefly in examining the light to see that this
adjustment is correct that it will be necessary to look at the arc, and
this should seldom be done without the protection of a piece of
smoked glass. Looking at the naked light too frequently may cause
very unpleasant effects from inflammation; "dust in the eyes" is the
sensation experienced. A saturated solution of boracic acid may be
used to bathe the eyes when this occurs, but it will seldom happen if
the precaution named be adopted.
The power of the electric light is inversely proportional to the square
of the distance from the object to be copied, or of the frames in
printing; therefore, whether it can be utilised in printing must de-
pend on the possibility of arranging the frames in such a way that
the time required will not be excessive. The frames must not be
too close to the light, or the heat will probably crack the thick glass,
or it may injure the varnish on the negative. To use the light
exclusively for printing would not be economical, as to be effective
the frames must be within two or three feet of the light, and at that
distance, with the light here referred to, a print could not be obtained
from a negative of ordinary density in less than thirty minutes.
When the electric light is used for portraiture the arrangement
must be quite different from what is required in copying or printing,
58
MANUAL OF PHOTOGRAPHY,
and a much more powerful light will be required owing to the neces-
sity for diffusion. If used direct, the light would cause intense
shadows, and therefore the interposition of some semi-transparent
material between the light and the sitter is essential.
The engine-power should be somewhat in excess of what would
theoretically be sufficient for the dynamo and lamp, as resistance some-
times occurs; and when the driving-power is too evenly balanced
with the dynamo, the light is affected; but this would not occur if
there were power to spare in the engine.
The following information may be useful:-For a lamp to give
2000 candle-power the driving-power should be 2 horse-power and
the dynamo capable of yielding 8 ampères = 50 volts. For 5000
candle-power the horse-power of the engine should be 3, and the
dynamo 15 ampères 50 volts; and for 20,000 candle-power the en-
gine should be 6 horse-power and the dynamo So ampères 50 volts.
On the management of a small installation very little need be said.
The engine should be carefully and regularly cleaned and all the parts
should be well oiled. The cups supplying the bearings of the arma-
ture of the dynamo with oil should be kept well supplied, and the
brushes should be carefully adjusted and kept quite clean. When
"sparking" occurs, the cause should be discovered at once and re-
medied, as, if neglected, the commutator will be damaged. The
dynamo referred to above, and used by the writer during five seasons
(that is, from November to March in each year), is now in perfect con-
dition. This is partly due to the excellence of the machine, and it
may be chiefly to the care taken in the adjustment of the brushes.
It can only be in exceptional cases when the electric light may be
advantageously used for portraiture; but for copying and printing
purposes it is often of much importance to be independent of daylight.
The Electric Arc Lamp.-Much of the pleasure of using the elec-
tric light for photographic purposes depends on the kind of lamp
selected. There are many kinds of lamps in use, and probably one
kind may be quite as useful as another; but as the writer has had
very little experience with any other than the one supplied by Messrs.
Crompton, and as that has fulfilled its purpose in a very satisfactory
way, the following description is given by their permission.
lamp illustrated is a double one, that is, it contains two pairs of car-
bons and the necessary regulating apparatus, but both pairs do not
come into use at the same time. The lamp used by the writer is a
single one, but the description is equally correct for either.
The
The lamp referred to is known as the D.D. (double differential)
form, and is the joint invention of Messrs. Crompton and Crabb, and
is an improvement on the older forms in point of simplicity of con-
struction, and also in regulation. This latter is effected by a brake-
LIGHT IN PHOTOGRAPHY.
59
wheel driven by the rack-rod attached to the upper carbons.
In

L
T
L
X
H
A
LÅ
FIG. 31.
FIG. 32.
the D.D. lamp also the intermediate gearing between the brake-wheel
and the pinion driven by the rack-rod is dispensed with.* Referring
* Since the description of this lamp was written Messrs. Crompton have intro-
duced some changes in the construction, as will be seen by reference to the second
figure.
60
MANUAL OF PHOTOGRAPHY.
to Fig. 31, B and B¹ are rack-rods carrying the positive carbons.
Sliding on each of these is a light gun-metal sleeve, S S¹, carrying
spindles to which are attached the two large brake-wheels E E¹, and
between them the pinion which gears into the racks. These brake-
wheels rest upon a pair of levers, the outer ends of which are pivoted
to the framework of the lamp, their inner ends being connected by
links to the core of the solenoid, which is placed in a central position
vertically above the two inner ends of the levers. This solenoid is
differential, G being the shunt and M the main coil, and the core is
partially supported by a spring, whose tension can be regulated by
means of the screw T. This is the only adjustment required in the
lamp for the regulation of the arc. The proper length of the latter
is from three thirty-seconds of an inch to three-sixteenths of an inch.
The screw T is turned to the right to increase its length, and to the
left to decrease it. Projecting vertically downwards from each sleeve
to a distance from the centre of the spindle about equal to the radius
of the brake-wheels is a stout pin or finger, F F1, the action of which
is as follows:-
Suppose the rack-rod to be drawn up, then, if the lever be pulled
by the solenoid above the horizontal position, the whole weight of
the rod and carbon is supported on the edges of the two brake-
wheels, and the friction of them on the surface of the levers is suffi-
cient to prevent their revolution; hence this rack-rod cannot run
down. But if the levers be below the horizontal, then the weight is
carried by the finger projecting from the sleeve, as shown at F, the
wheels are free to turn, the rack runs down, and continues to do so
until the positive and negative carbon points come in contact. Now,
let the current be switched on by its passage through the main wire
of the solenoid; the levers are raised, striking the arc, and at the
same time applying the brake to the wheels. The combined action
of the shunt and main currents on the solenoid core automatically
adjust the length of the arc. If this becomes too great, the increased
current through the shunt draws down the core and levers, the brake-
wheels are left free to revolve, and the arc shortens. On the other
hand, if the carbon points be too close, the levers are raised, bringing
with them the rack-rod and upper carbons. The fact of making the
finger projecting from one sleeve longer than that from the other
determines which pair of carbons shall begin to burn first, because on
switching on, that pair which has the longer pin will be the last to
break contact, and will therefore originate an arc in so doing.
When fitted with the full length of 19½ in. of carbon 13 mm. in
diameter, the lamps will burn from 12 to 18 hours, according to the
current passing, which may vary from 20 to 8 ampères, the light
varying from 4000 to 1000 candles, the candle-power being measured
LIGHT IN PHOTOGRAPHY.
61
at an angle of 30° below the horizontal line, cutting the arc itself.
The electromotive force required is 45 to 50 volts. This description
refers to the lamp carrying two carbons. The single lamp with
carbons of the same length will, of course, only burn half the time
named.
Oxyhydrogen Light. -For convenience and quality there is per-
haps no light to surpass that obtained by means of a jet of oxygen
gas projected through a flame of hydrogen which is made to impinge
on a disc or cylinder of lime, when the lime becomes incandescent
and a very brilliant light is produced. This light was originally
used for signalling purposes in Ireland by Lieut. (afterwards Captain)
Drummond-hence the name, the "Drummond light"—and was
found to be much superior to the Argand lamp, then in use in the
Trigonometrical Survey for fixing the positions of distant signal-stations.
The date of Captain Drummond's adaptation of the light is about
1830. One of the earliest applications of the limelight was for the
exhibition of microscopic objects by projection on to a disc or screen,
and when used in the "magic" or optical lantern became a valuable
means of illustrating lectures. The introduction of photography
added greatly to the popularity of the lantern; and, with the im-
proved optical appliances, the limelight is now generally used where
formerly rough diagrams formed the means of illustrating lectures.
The wonderful perfection of photographic views and pictures of all
classes of subjects, whether shown by the single or the dissolving
lantern, has tended to make limelight illustrations so deservedly
popular.
The preparation of oxygen is a simple matter, but requires care.
Take of powdered potassium chlorate 16 ounces, and 4 ounces of
black oxide of manganese; these should be mixed together and placed
in a retort, which may be heated over a clear fire or Bunsen burner.
The gas which is evolved should be passed through a "wash-bottle,"
then into the india-rubber bag, all atmospheric air being first forced
out. The principal caution to be observed in making oxygen is to
see that the manganese dioxide is pure, and this is roughly ascer-
tained by heating a small quantity with three times its weight of
potassium chlorate in a test-tube. The mixture should not show any
combustion or sparking within itself, for this indicates the presence
of impurities such as soot. Hydrogen is troublesome to make, and
as common coal-gas forms a good substitute, it is generally used in
producing the limelight. When the pressure from the gas-main is
not sufficient, the gas can be stored in a bag and pressure applied in
the usual way.
Oxygen gas is now supplied in steel cylinders, and this form is in
every way more convenient than making it at home, as it renders
62
MANUAL OF PHOTOGRAPHY.
gas-bags and weights unnecessary. The condensed gas is safe to use
when the supply is carefully regulated.
An excellent light is produced when the oxygen is blown through
a flame of spirits of wine, and it is then called the oxycalcium light.
The vapour of ether when mixed with oxygen gives a good light, but
although the apparatus has been improved, it cannot be said that
there is no danger in its use. (See Ethoxo-Limelight.)
It is difficult to estimate the intensity of very bright lights; the
eye alone cannot do it; and therefore a comparison with a standard
light becomes necessary; that from a spermaceti candle burning two
grains per minute is generally adopted. With this light the flame
of an Argand burner can be adjusted, and against this the more
intense limelight can be tested. Determinations made in this manner
give from 250 to 800 candles as the value of the light from incan-
descent lime. The great difference arises from the kind of burner
used, the size of the aperture through which the oxygen is passed,
and the degree of pressure. The kind and form of the lime used also
affects the quality of the light. Great care must be taken to avoid
pitting an effect caused by the jet of gas burning away the lime in
the form of a hollow or pit, which not only reduces the light, but
endangers the condenser in the lantern by causing the jet to project
the heat on to the glass. The remedy for this fault is to cause the
lime to revolve, either by clockwork or by hand.
Continuing Action of Light. The fact is well established that
the light has a continuing action on a gelatine film which has been
made sensitive to light with potassium bichromate, that is, paper
prepared for carbon-printing, after exposure to light for less time
than would be necessary if the picture were to be developed at once
will, after a few hours, become fully printed; thus proving that the
change set up by exposure to light continues when the picture has
been removed into the dark.
It has been stated that gelatine negatives have been known to
possess this quality of continuing the action of light after exposure;
but on this point the writer has some doubt, as quite recently in his
own experience a negative was developed on a gelatine plate six years
after the exposure had been made; and the result showed that there
had been no continuing action of light, as also that a good negative
may be developed six years after exposure. It may happen that
gelatine negatives become more dense in the printing frame or when
left exposed to light; but the cause of this is quite different from the
case under consideration.
Compressed Gas.-The ordinary method of using bags to contain
oxygen and hydrogen gases is now being superseded by cylinders in
which the gas is compressed. The cylinders are made of iron or
LIGHT IN PHOTOGRAPHY.
63
steel; the latter, being the lighter and stronger, is more generally
used; and are made to hold 15 or 30 cubic feet of the compressed
gas. As the compression may amount to over 100 atmospheres it is
too great for use with the optical lantern, and the control of the
admission of the gas to the lantern is obtained by the use of a pressure
gauge. As the cylinders are lighter and less cumbersome than the
pressure boards, bags, and the weight necessary to produce the pres-
sure, the convenience of the cylinder is very great.
Ethoxo-Limelight.-Now that oxygen and hydrogen gases can be
obtained compressed in cylinders of convenient size, it is scarcely ad-
visable to use any substitute for the hydrogen. Ether can be used,
and various plans have been proposed by which danger is minimised;
but in the hands of inexperienced persons there is danger, and as the
gas cylinders may be considered safe, the use of ether is not recom-
mended.
Magnesium Light. The extensive use now made of the metal
magnesium renders it desirable that some facts relating to it should be
stated here. About the year 1808 Sir Humphry Davy, at the Royal
Institution, London, by means of large electric batteries, succeeded in
decomposing earths and alkalies and demonstrated their metallic bases.
A new field of research was thus opened, and one result was the dis-
covery of the metal magnesium. Although the metal was known, it
remained for about half a century little more than a scientific curiosity.
When combined with oxygen, in the form of magnesia, the substance
was used as a medicine; the smoke or fumes which are seen when
the metal is burning, and which remains for some time suspended in
the atmosphere, is this magnesia. Sir H. Davy did very little more
than prove the existence of the metal, and for about twenty years
after nothing appears to have been done to carry the experiments
further, until in 1827 it was shown by Wöhler that by the decompo-
sition of the chloride of aluminium by potassium the metal aluminium
was formed, and it occurred to M. Alexandre Bussy, a Parisian chemist,
that it would be possible to separate magnesium in the same way from
its chloride. By fusing that chloride with potassium he succeeded in ob-
taining globules of the metal magnesium. Bunsen and other chemists
succeeded in obtaining the metal by electrolysis, and in 1856 the chlo-
ride of magnesium was reduced by sodium, the fluoride of calcium
being used as a flux. By this method the metal was obtained in larger
quantities. While effecting this, Deville and Caron at the same time
showed that the metal was very volatile, and this property was later
on utilised in its purification. Magnesium was still little more than a
laboratory curiosity. In 1859 Bunsen of Heidelberg and Dr. (now
Sir) H. E. Roscoe of Manchester pointed out the value of magnesium.
as a source of light for photographic purposes. About this time the
64
MANUAL OF PHOTOGRAPHY.
Memoir of Bunsen and Roscoe was seen by M. Edward Sonstadt,
and it occurred to him that the metal could be made on a commercial
scale. In 1862 he had so far succeeded that he took out his first
patent for "Improvements in the manufacture of the metal magne-
sium," at the same time he was enabled to show specimens of the
metal varying in size from a pin's head to that of a hen's egg. By a
further series of experiments Sonstadt succeeded in purifying the
metal by distillation, and in 1863 one of the first lumps of the puri-
fied metal was presented to Professor Faraday at the Royal Institu-
tion, London, the place where the metal was first discovered.
"This
is indeed a triumph," was the remark made by Faraday when he first
handled the mass of metal; and a year later, when he saw a still
larger mass, he is reported to have said, "I wonder it does not take
fire spontaneously," so great is the affinity of the metal for oxygen.
There are
The manufacture of magnesium was commenced in Manchester in
1863, a company having been formed for the purpose.
three stages in the manufacture of the metal :—I. The preparation of
the anhydrous magnesium chloride; II. the release of the magnesium
from the chlorine; and III. the purification of the metal by distilla-
tion. I. In the first stage, lumps of rock-magnesia (magnesium carbo-
nate) are placed in jars and saturated with hydrochloric acid. The
metal magnesium is contained in the rock combined with carbon
and oxygen; the magnesium combines with the chlorine of the acid,
and chloride of magnesium is formed in solution. The solution is
next evaporated, and when sufficiently dried the salt is heated in a
crucible to drive off the whole of the water, and the chloride is then
stored in air-tight vessels. II. The metal sodium is next required to
reduce the magnesium from the dried salt. Sodium itself is a very
curious metal, having great affinity for oxygen and decomposing water
in a way similar to potassium. Five parts of the dry magnesium
chloride with one part of sodium are placed in a crucible, which is
covered and heated to redness, when the chlorine leaves the magnesium
and goes over to the sodium. On cooling, the new metal is found in
nuggets of various sizes, and in this state is called crude magnesium.
III. In the third stage the distillation is effected; the metal is vapo-
rised; the vapour is condensed in a finely divided state, and in the
solid subsequently melted and cast into any form desired. As at this
time no other use for the metal was known than that of a means for
producing a brilliant light, it became a question as to how to utilise
it. The wire form was found to be the most convenient. As the
metal is not ductile, the wire was made by pressure, and this is
effected in a very ingenious way. The nuggets are put into an iron
vessel which is heated to redness by gas, one end being open to
receive the ram of the hydraulic press, and the other having a hole
LIGHT IN PHOTOGRAPHY.
65
the size of the wire required, and through which the wire is forced.
In this form the metal could be used as a source of light. The first
notice of experiments with it may be found in one of the Manchester
papers about the end of 1863 or early in 1864. “Interesting photo-
chemical discoveries.-At a recent meeting of the Manchester Lite-
rary and Philosophical Society, Professor Roscoe exhibited the light
emitted by burning a portion of a fine specimen of pure magnesium
wire 1 mm. in diameter and 10 feet long, which had been manu-
factured by M. Sonstadt." After the meeting a small lump of the
metal was presented to the writer, which was hammered into a thin
sheet, and with strips cut from it experiments were made which are
alluded to in the paragraph referred to above, as follows: "The result
of an experiment I have just made is that in fifty seconds with the
magnesium light I have obtained a good negative copy of an engrav-
ing, the copy being made in a darkened room.” At this time the wire
was sold at two shillings and sixpence per foot! It is now one
shilling and sixpence per ounce.
But although the metal was still only produced in small quantities,
sufficient was placed at the disposal of the writer, who at once showed
the value of the new source of light for photographic purposes by pro-
ducing portraits which required about twenty grains of the metal burnt
in strands of ribbon lightly held together with wire of the same metal.
In the form of wire the combustion was somewhat uncertain, and it
was found by the writer that by passing the wire between rollers, or
when it was flattened into a thin narrow ribbon, the combustion was
much more regular and rapid, and in this form the metal is now
generally used. Early in 1864 a stereoscopic picture of the Blue
John Mine in Derbyshire was made by the writer, assisted by Mr.
Mather and Mr. Mellor, and in May of the same year the portrait of
Dr. Faraday was taken at the Royal Institution in London. In 1865
Professor Piazzi Smyth obtained some good photographs of the chamber
in the interior of the Great Pyramid, and since then the metal has
become useful to science in many ways. To the lecturer, when a
brilliant light is required for a short time only, the metal is invalu-
able, and now that we have quick plates, magnesium in the form of
fine powder, and the price sufficiently low to make its use not extra-
vagant, it is much employed for flash-light experiments and in other
ways.
To obtain the flash, the magnesium powder may be used alone by
simply causing its quick combustion in a spirit or other flame, but
the most simple and, if carefully managed, successful way of using
the flash-light is by burning a mixture of 15 parts of magnesium
powder, 30 parts of potassium chlorate, and 15 parts of crushed white
sugar. These should be quite dry and then intimately mixed to-
E
66
MANUAL OF PHOTOGRAPHY.
gether with the fingers-not ground in a mortar-and sprinkled over
a tuft of gun-cotton. This mixture can then be placed on a plate or
sheet of metal in the position where the light is required, and ignited.
In some cases two flashes may be made simultaneously, one being
larger than the other-the smaller one being used to give some relief
to the heavy shadows liable to be produced by the light being on one
side only. This defect may also be remedied by the use of reflectors
of white calico or paper. As the ordinary light in a room at night is
not sufficiently bright to enable objects to be seen for focussing by,
the light of a taper or candle may be used if held near the principal
object. The place for the flash should be as near as convenient to
the objects to be photographed, but not so that the light can enter
the lens. This may be avoided by holding a screen to protect the
lens. The cap of the lens should not be removed until just before
the flash is made, and all the ordinary lights in the room should be
left burning-they will have only one result on the picture, and that
is keeping the eyes of the sitter (if a portrait is to be taken) in a
natural state.
As photographic portraits are usually taken in a light more or less
diffused, the shadows are less marked than they would be if taken in
a light such as that in which an artist works; but heavy shadows of
the kind referred to, although perhaps artistic, are not generally ap-
proved of; and, therefore, if two lights are not used, the flash may be
diffused by using tissue paper placed between the sitter and the light.
So-called lamps have been introduced for igniting the magnesium,
but the method named answers every purpose and requires no
apparatus.
PART II.
PROCESSES.
DURING the fifty years which have elapsed since the discovery of
photography, a very large number of processes and modifications have
been introduced, and, of course, amongst them many of very little
importance. The science of chemistry may, perhaps, be said to pre-
sent a parallel with photography in the rapid development which it
has undergone within the period named. The beautiful daguerreotype
was in a very few years superseded by the almost equally beautiful
collodion process, and this, in its turn, has to a very large extent been
displaced by gelatine. The range of usefulness of the daguerreotype
was limited. The convenience of the paper process of Talbot did
not prevent its entire supersession by the collodion negative. The
gelatine dry plates for outdoor work displaced collodion, and in the
near future films of various kinds will take the place of glass. Already
it may be said that, for negatives of moderate size, films are available.
It would involve much, and possibly useless, labour to give here a
full account of all the processes which have been employed in pho-
tography. It will be sufficient for the purpose to point out what has
been done. In many cases very little more than the names of the
processes will be given; but the more important will be treated with
as much detail as space will permit.
Alabastrine Process.-The term alabastrine is applied to positive
pictures made by the collodion process which have been treated with
mercuric chloride. The positive should be of good quality, and have
clear glass in the shadows. After being thoroughly fixed and washed,
and while wet, the bleaching is effected by pouring on the plate a
solution composed of
Hydrochloric acid
Nitric acid
Water
I drachm
I
2 ounces
to which must be added sufficient mercuric chloride to saturate the
solution; the excess will remain in crystals; one drachm of alcohol
must then be added. This solution will first darken the picture, but
67
68
MANUAL OF PHOTOGRAPHY.
1
in the course of a few minutes it will be entirely whitened; it should
be allowed to remain on the levelling stand until this occurs. The
picture must now be thoroughly washed and dried. Powder colours.
may be applied, if required; and, as the effect of the whitened pic-
ture is much the same on either side of the glass, the colour effect
may be made to penetrate by applying a suitable varnish, which should
be used while the plate is warm.
A varnish composed of
Turpentine
Mastic varnish
will be found to answer.
ounce
1 ounces
These bleached positives, if not varnished, must be well protected
from the atmosphere, and, if so protected, are very permanent. The
bleaching effect produced by the mercuric chloride was one of the
discoveries of Mr. Scott-Archer.
Albumen Process.-It was M. Niépce de Saint-Victor who, in
1848, first used albumen on glass for the purpose of making negatives.
Albumen was also used by M. Blanquart Everard; and the process
was successfully practised by M. Le Gray, who prepared his plates in
the following way :-Five fluid ounces of the white of fresh eggs
were mixed with 100 grains of iodide and 20 grains of potassium
bromide and 10 grains of common salt. After beating this into a
thick white froth it was allowed to stand all night; on the following
day the clear fluid was poured or syphoned off, and was then ready
for use in preparing the glass plates. To coat a plate with albumen
is a matter of some difficulty. Le Gray used a straight-edge of glass
to distribute the albumen on the glass surface. The plate must be
perfectly level, and when prepared with the albumen it must be
allowed to dry so as to preserve an even coating. When dry, the
plates were held before a bright fire and heated to about 180° Fah.,
by which means the albumen became insoluble and was then ready to
be made sensitive to light by immersion in a solution of aceto-nitrate
of silver. Plates thus prepared could be used while the albumen was
wet, but great care was necessary in immersing them in the solution
of silver to avoid markings. If the albumenised plates were to be
used dry, they were dipped in a bath of gallic acid after they were
taken out of the silver solution; they were then well washed in
distilled water and dried. The plates were developed in a saturated
solution of gallic acid and fixed with sodium thiosulphate. Negatives
thus prepared had the great advantage of transparency in the shadows;
would yield positive prints on paper with much greater facility than
paper negatives, and were free from the defects inherent in the paper
process.
Le Gray's method was modified in many ways, and in this case (as
PROCESSES.
69
in most other photographic processes) the variations in the manipula-
tion led to results differing very little from each other.
Albumen Substratum.-Clean glass is absolutely necessary in all
photographic processes in which glass is used. No matter how care-
ful the manipulation has been, the surface often retains sufficient dirt
to cause a collodion film to leave its support in the process of drying,
if not before. This is always a source of annoyance and loss. The
act of polishing a glass surface induces an electric state which causes
particles of fluff and dust to collect, and these, if not removed, would
make defects in the developed picture. A clean glass surface also
readily attracts moisture. A very effectual remedy is found in a
substratum of albumen. It may be said that the introduction of
albumen into the negative bath is objectionable, but unless it has
been allowed to run over the back of the glass it does not affect the
bath, as the collodion covers it. The experience of many years has
proved that no harm whatever results to the silver bath, and the
almost perfect certainty that the effect of dirt or grease, if present to
a slight extent, will not be seen when a plate has been properly
coated with the substratum of albumen makes its use desirable. If
the glass has not been previously used, it should be placed in water
with sufficient nitric acid (1 oz. of acid to 20 oz. of water), and
allowed to remain an hour or two. The glass is then thoroughly
rubbed under a stream of water with a pad of calico or flannel. The
surface water is then drained off and the dilute albumen is poured
To prepare the albumen, take the white of one egg and whisk
it into a froth; add 20 ounces of water and a few drops of ammonia.
When required for use, run some of the solution through a filter of
lint (this is an excellent material for filtering some solutions, using
the lint side upwards), and then cover the wet plate, allowing the
albumen to run off to waste; then coat again with albumen, return-
ing the surplus to the cup or glass measure; place in a rack to dry,
and the plate is ready for use. Plates which have been used may be
left in the acidulated water for a few hours, when the film will readily
leave the glass, and the process of cleaning is the same as with new
glass. The acid may be repeatedly used, and strengthened when
necessary; it should be occasionally filtered through a coarse cloth to
remove the films, which may be dried and placed with the silver
residues, as they contain much silver. The acid also contains silver,
which may be recovered by the addition of common salt or hydro-
chloric acid. When treated with the substratum, sheets of glass may
be used repeatedly, or until they become scratched and unfit for
further use.
over.
Varnished glass must be dealt with in a different manner, by the
method described under the heading Cleaning Glass.
70
MANUAL OF PHOTOGRAPHY.
Amphitype. Many curious and interesting processes resulted from
the experiments of Sir John Herschel; one of the most remarkable
he called Amphitype; and at a meeting of the British Association
held at York he thus described the process :-
(C
'Paper proper for producing an amphitype picture may be pre-
pared either with the ferro-tartrate or the ferro-citrate of the protoxide
or the peroxide of mercury, or of the protoxide of lead, by using
creams of these salts, or by successive application of the nitrates of
the respective oxides, singly or in mixture, to the paper, alternating
with solutions of the ammonio-tartrate or ammonio-citrate of iron, the
latter solution being last applied, and in more or less excess.
Paper so prepared and dried takes a negative picture in time varying
from half an hour to five or six hours, according to the intensity of
the light; and the impression produced varies in apparent force from
a faint and hardly perceptible picture to one of the highest conceiv-
able fulness and richness both of tint and detail, the colour in this
case being a superb velvety brown. This extreme richness of effect
is not produced except lead be present either in the ingredients
used or in the paper itself. It is not, as I originally supposed, due to
the presence of free tartaric acid. The pictures in this state are
not permanent. They fade in the dark, though with very different
degrees of rapidity, some (especially if free tartaric or citric acid be
present) in a few days; while others remain for weeks unimpaired,
and require whole years for their total obliteration. But, though
entirely faded out in appearance, the picture is only rendered dormant,
and may be restored, changing its character from negative to positive,
and its colour from brown to black (in the shadow), by the follow-
ing process:—A bath being prepared by pouring a small quantity of
solution of pernitrate of mercury into a large quantity of water,
and letting the subnitrated precipitate subside, the picture must be
immersed in it (carefully and repeatedly clearing off the air-bubbles),
and allowed to remain till the picture (if anywhere visible) is entirely
destroyed, or, if faded, till it is judged sufficient from previous
experience; a term which is often marked by the appearance of a
feeble positive picture of a bright yellow hue on the pale yellow
ground of the paper. A long time (several weeks) is often required
for this, but heat accelerates the action, and it is often complete in a
few hours. In this state the picture is to be very thoroughly rinsed
and soaked in pure warm water, and then dried. It is then to be
well ironed with a smooth iron, heated so as barely not to injure the
paper, placing it, for better security against scorching, between smooth
clean papers. If, then, the process has been successful, a perfectly
black positive picture is at once developed. At first it most com-
monly happens that the whole picture is sooty or dingy to such a
PROCESSES.
71
degree that it is condemned as spoiled, but on keeping it between the
leaves of a book, especially in a moist atmosphere, by extremely slow
degrees this dinginess disappears, and the picture disengages itself
with continually increasing sharpness and clearness, and acquires the
exact effect of a copperplate engraving on a paper more or less tinted
with pale yellow."
Aniline Process.-This process was the subject of a patent by Mr.
Willis, of Birmingham. Paper is prepared with
Potassium (or ammonium) bichromate.
Phosphoric acid (dilute)
Water
30 grains.
I drachm.
I ounce.
The paper may be floated on or brushed over with the solution.
When dry, a print is obtained by exposure under a transparency. It
is developed by exposing it to the fumes of aniline dissolved in
benzole, sprinkled on blotting-paper, and placed in a shallow box;
the print to be developed being pinned to the lid. When fully
developed the print is washed, and afterwards placed in water con-
taining a few drops of sulphuric acid, and then again washed. This
is one of the processes which are of very little value; it is interest-
ing, as are many others which will be referred to, but is now seldom
or never used.
A process by Herr Endemann for producing prints in black lines
with aniline may be mentioned as an instance of the kind.
Aristotype. Dr. Liesegang, of Dusseldorf, introduced paper pre-
pared with gelatine and chloride of silver to print out in the same
way as albumenised paper. The prints can be toned and fixed at one
operation. When a print with very highly glazed surface is preferred,
this paper gives perfect results.
Water
Sodium thiosulphate
Alum
Solution A.
12 ounces.
2
39
2 drachms.
Ammonium sulphocyanide
Common salt.
I drachm.
4 drachms.
This solution must be mixed and allowed to stand eight days, and
then filtered.
Water
Gold chloride
Solution B.
3 ounces.
15 grains.
Take of solution A. 60 parts, solution B. 7 parts, and add 40 parts
of combined toning and fixing bath which has previously been used.
In ten minutes the prints become red, in fifteen minutes brown, and
7?
MANUAL OF PHOTOGRAPHY.
in twenty minutes brownish violet. The prints may be taken out of
the toning bath after five minutes and laid flat. They continue to
tone, and when the desired colour is reached they may be washed
in water.
Instead of gold, the prints may be toned with platinum, as sug-
gested by Stieglitz.
I.
Solution A.
Potassium oxalate
Potassium phosphate
3 ounces.
12
Water
I quart.
Solution B.
Potassium chloro-platinite
Water
•
To tone, mix 6 parts of A. with 1 part of B.
15 grains.
6 drachms.
II.
Potassium chloro-platinite
Water
Nitric acid
•
15 grains.
I quart.
25 minims.
The prints before toning are washed, put into the toning solution.
for ten minutes, and then thoroughly washed. If an alum bath is
necessary, it should be used after toning. The prints may be toned
to any tint between light brown and black. If a matt surface be
preferred, the prints should be dried on ground glass.
See Gelatine Chloride Paper (Ilford).
Artotype (see Collotype).
Autoglyphic Process (see Half-tone Engraving).
Autotype (also called the Carbon Process).-In 1871 the late Mr.
J. R. Johnson wrote, "Silver printing, like the daguerreotype, will
soon be a thing of the past, and at no distant period there will be no
distinction, in a chemical and physical sense, between the palette of
the photographer and that of the artist in oil or water colours." The
meaning of this is that prints in silver being often unstable, the pro-
cess would go out of use, and pigments of any colour combined with
gelatine would alone be used in the production of photographs. Nearly
twenty years have elapsed since Mr. Johnson wrote the words quoted,
yet silver printing is still used very largely. The beautiful process of
carbon printing, advocated by Mr. Johnson, has come extensively into
use, and the undoubted permanence of the prints produced by it give
the process an importance which it is impossible to exaggerate.
The action of light upon organic matter when combined with the
bichromates of ammonia or potash is the basis of all the processes
which come under the term carbon printing. This effect of the action
PROCESSES.
73
of light on paper which had been immersed in the bichromates was
first observed by Mungo Ponton. Becquerel showed that sized paper
acted much more rapidly, and for that reason gelatine or gum is em-
ployed in combination with the bichromates. The addition of coloured
pigments to the gelatine was first proposed by Poitevin, who found
that when paper was so prepared and exposed under a suitable nega-
tive, those parts on which the light had acted became insoluble, while
the parts not acted on could be washed away, thus leaving the picture
with black or coloured lines on a white ground. In this manner the
first permanent photograph in pigments was produced. This result was
not quite what was desired, owing to the absence of half-tone; and it
was the Abbé de Laborde in France, and Burnet and Blair in England,
who pointed out the cause of Poitevin's failure. They showed that the
pigmented gelatine was entirely insoluble on the surface which had
been next to the negative, being covered with a kind of skin which
prevented the action of the warm water used to wash away the un-
altered gelatine; and it was shown that the picture must be washed
from the other side of the film. In order to effect this, Fargier coated
a sheet of glass with the sensitised gelatine, which, when dry, was
exposed under a negative; the plate was then coated with collodion,
and, when dry, was placed in warm water, which caused the gelatine
to leave the glass; and, as the collodion was not affected by the warm
water, the picture was caught with the collodion side downwards on
a sheet of paper. The picture could then be washed from the back,
and in this way the first photograph in pigmented gelatine with half-
tone was produced. The process was much too difficult and trouble-
some to be of practical use.
Mr. J. W. Swan, of Newcastle-on-Tyne, took out a patent in 1862
for pigmented tissues and their use. Instead of coating the gelatine
with collodion, Mr. Swan first coated the glass with collodion, and
upon this spread his gelatine film, which, when dry, was stripped from
the glass and placed with the gelatine side next to the negative to be
printed; therefore, in developing the picture, it could be attacked
from the back, while the soluble gelatine was removed with warm
water. While this was being done the picture was supported on
paper which had been coated with a solution of india-rubber, and as
the tissue holding the picture was also coated in the same way, they
were passed through a copper-plate press, and were thus made to
adhere firmly together. Pictures so prepared were in slight relief,
and gave a true impression of the negative in half-tone.
The next great improvement effected by Mr. Swan was in doing
away with collodion and glass. The gelatine was spread at once on
the paper and printed. India-rubber solution was next applied and
was pressed into contact with another piece of paper coated in the
74
MANUAL OF PHOTOGRAPHY.
same way. Soaking in warm water now softened the gelatine, and
the picture could be pulled off from the first paper, and could then be
washed to free it from the unaltered gelatine; but the picture thus
produced was reversed. To bring it into its correct position a paper
coated with gelatine made partially insoluble with alum was placed in
warm water; the softened gelatine surface was brought into contact
with the print, and the two surfaces pressed together. When dry,
benzene was applied to the back of the picture, and passing through
the paper, softened the india-rubber; when the paper was removed, the
picture appeared in its natural position. Very beautiful results were
obtained in this manner.
In
The next improvement was effected by Mr. J. R. Johnson (in
1868), who found that no cement was necessary to fix a print on its
support, if that support were made impervious to air and water.
1874 Mr. J. R. Sawyer patented a "flexible temporary support."
This temporary support is a hard tough paper coated with gelatine
which is insoluble when dry; this is coated with an alkaline solution
of lac, and then rolled between polished plates; the surface is next
treated with a waxing compound, which enables the picture to leave.
the support when the transfer to paper is applied. The advantages
of this support are that the picture can be seen while being developed.
The pieces of support can be used repeatedly, and the finished pic-
tures have a pleasing surface.
In 1874 M. Lambert introduced some improvements. He showed
that glass coated with collodion could be used, but the surface must
be made greasy before the collodion was applied.
Sufficient time has now elapsed to show that photographs printed
in pigmented gelatine are permanent. Gelatine is known to be a
permanent body, and provided the colour used be also permanent,
there seems to be no reason why absolute permanence should not be
attained by the use of such bodies in combination. Experience has
shown the kind of colour to use, and in the preparation of the tissues
only such colours as are known to be permanent are now employed.
The Autotype process possesses advantages which can be claimed
for no other. Drawings of all description can be copied in exact
fac-simile as to colour, and, if necessary, the copy may be in the same
pigment as the original. Photographs on albumenised paper may be
so exactly imitated in autotype that the difference is very difficult of
detection.
In printing on carbon tissue two methods are adopted-double and
single transfer. When prints are required from negatives taken in the
ordinary way, they must be transferred twice, otherwise the copies
would be inverted, that is, the left side would appear as the right-
hand side, and vice versâ; so that, unless the negatives are taken with
PROCESSES.
75
the image inverted, the single transfer method cannot be used, except
when the inversion may be disregarded. The double transfer may
be avoided by using a reversing mirror, or by taking the negative
through the glass, which would have the effect of reversing the sub-
ject. By stripping the film from its glass support, it may be used so
that the second transfer is avoided. The trouble, however, of using
the temporary support in the double transfer is not very great.
As the preparation of the carbon tissue is a somewhat difficult and
troublesome process, and as it can be purchased ready prepared, and
also, when desired, ready sensitised, very few will care to prepare their
own paper. Generally, it may be said that the tissue is merely paper
coated with gelatine with which carbon or colouring matter of some
kind has been mixed. This is prepared in rolls, and when dry will
keep for any length of time. As the paper will not keep many days
after it is made sensitive to light with the bichromate, it is usually
ordered only in such quantities as can be used at once. Where there
is convenience for drying the tissue after sensitising, there is some
advantage in purchasing the plain tissue in rolls. The importance of
the process requires that minute details should be given for its success-
ful manipulation, but space here is too limited. The fullest instruc-
tion may be found in the "A. B. C." guide issued by the Autotype
Company. There are no difficulties in the working details which
cannot be overcome with very little practice.
It may be mentioned that most of the patents connected with the
carbon process have now lapsed.
Beechey's Emulsion Process (Collodion).-In 1876 the Rev. Canon
Beechey introduced a modification of the collodio-bromide process, and
in 1879 he gave further particulars in the British Journal Almanack.
As the use of collodion emulsion is very limited, it will be sufficient
to say here that when such plates are required they may be prepared
as under. Take
A. Cadmium bromide (anhydrous)
Alcohol, absolute
When clear, decant and add
Strong hydrochloric acid .
400 grains.
IO ounces.
So minims.
Then prepare in yellow light the day before it is required for use
Ether.
Gun-cotton
Solution A.
10 or 12 grains.
9 drachms.
ounce.
To make this sensitive, dissolve 40 grains of fused silver nitrate,
powdered, in 1 ounce of alcohol. The quantity given above will
76
MANUAL OF PHOTOGRAPHY.
prepare two dozen half plates. The emulsion must be kept in the
dark and shaken a few times. The plates must have a substratum of
gelatine, 5 grains soaked in 1 ounce of water, for an hour, and then
dissolved in 3 ounces of boiling water, filtered while hot.
As the plates are coated with the emulsion they are placed in a
dish containing filtered rain-water, and then in another dish contain-
ing 30 ounces of table-beer with 30 grains of pyrogallic acid, used as
a preservative. About six plates may be prepared one after the
other, passed through the water and preservative, and rinsed in suc-
cession. The plates are developed with
A. Pyrogallic acid
Alcohol, methylated
B. Potassium bromide
Water (distilled) .
C. Ammonium carbonate
Hot water
•
96 grains.
I ounce.
12 grains.
I ounce.
60 grains.
I ounce.
Mix of A. 30 drops, B. 30 to 60 drops, C. 2 drachms. First rinse the
plates under a tap to remove greasiness, and then pour on the develop-
ing solution. The plates may be intensified, if necessary, with "pyro"
and silver. Fix with weak cyanide or with sodium thiosulphate as
usual.
The exposure necessary in a good light will vary from thirty seconds
to three minutes for a landscape. For lantern slides or transparencies
a few seconds' exposure to gas-light will be sufficient.
Bitumen Process.-Bitumen or asphaltum varies very much in its
properties; some kinds are soft, others hard, and some are fluid, as
naphtha and petroleum. The kinds used in photography are found
in Syria, the Island of Trinidad, and some other places.
The discovery by Niépce that the resinous substance bitumen or
"Jew's pitch" was made insoluble by exposure to light has proved
of great value in some of the recent applications of photography.
Niépce's first experiments were made by spreading a film of bitumen
on a lithographic stone; by means of acid the picture was then "bitten
in" and could be printed from in the usual way. This in his
hands never became of any value, owing to the want of sensitiveness,
an exposure of many hours being necessary to obtain an image; but
he also tried glass and metal plates in his later experiments, when
iodine was introduced, eventually leading to the discovery by
Daguerre of the process known by his name. A thin film of bitumen
is now made use of in most of the processes for printing on zinc, and
the best results are obtained by this means. Bichromated gelatine
can be used; but the results for the finer kinds of work are not equal
to those obtained with the bitumen.
The best Syrian bitumen should be used, and this should be puri-
PROCESSES.
77
fied. The powdered bitumen must be dissolved in twice its weight
of essence of turpentine and well shaken up until it forms a thick
syrup. Some of this thick syrup must now be mixed with sulphuric
ether, well shaken together, and then allowed to settle. The fluid
portion is now to be poured off, and more ether added two or three
times, until very little of the bitumen is taken up. The bitumen left
as a thick sediment may now be spread over plates until it becomes
nearly dry, which will require a few days. This must be done at a
sufficient distance from any artificial light to prevent any chance of
igniting the vapour of the ether, and it may be done in daylight.
The bitumen thus purified may be dissolved in benzene or chloroform,
and must be just sufficiently fluid to become a film of a golden
brown colour when spread over and dried on a zinc plate, and a
zinc or copper plate having been well polished, may now be coated
with the bitumen (which must be filtered) by holding the plate with
the left hand (not by one corner as when coating a plate with col-
lodion, but poised on the fingers and thumb), and then allowing the
fluid to completely cover the metal-pouring the superfluous fluid
back into the bottle; a whirler" can be used if preferred. As the
film is not very sensitive, this coating may be done in diffused
daylight. When quite dry, the plate is placed in perfect contact
with the negative in a printing frame and exposed to light. The
time necessary to make the print varies very much, and can only be
ascertained by experiment. It may require from a few minutes to
two or three hours, and in dull weather very much longer. When
printed, the development is effected by holding the plate in the hand
in the same way as when coating it; then it must be flooded quickly
with turpentine, which will at once dissolve the bitumen; and, as
soon as the subject is seen to be fully developed, a gentle stream of
water from a tap is allowed to flow over it to wash off the tur-
pentine. If the printing has been correctly timed, we have now a
very delicate and perfect picture in bitumen on the metal, which,
when dry, can be etched with acid in the usual way.
Black Lines (see Cyanotype). Tracings for reproduction with
black lines on a white ground should be prepared with good black
Indian-ink, and the paper should be as transparent as possible.
The print is fully exposed when the sensitised paper has changed
from yellow to white. The developing solution is composed of—
Gallic acid.
Citric acid
Alum.
•
C
I ounce.
I
8 ounces.
Of this take 1 ounces to I gallon of water.
This should be mixed and used the same day. The print should be
78
MANUAL OF PHOTOGRAPHY.
immersed until the lines are black. The developing solution may
be repeatedly used. The prints must be thoroughly washed in cold
water.
Bromide-Printing Process.-When opal glass and paper are coated
with silver bromide emulsion in gelatine, they may be used for
contact-printing or for enlargements, either by artificial or by day
light; but for contact-printing artificial light is to be preferred. Paper
is prepared in two degrees of sensitiveness, the slow kinds being more
suitable for printing by artificial light and for enlarging by daylight,
while the rapid paper may be used for enlarging by artificial light.
With suitable negatives (the kind called "plucky" gives the best
results) very beautiful prints may be obtained, and enlargements,
when very carefully worked upon by a skilful artist, have qualities
which are possessed by no other kind of prints, with the exception
of carbon; and there is this difference in favour of the bromide print,
that an enlarged negative has not to be made. On the other hand,
it cannot be said that the bromide print has the same permanent
quality which the carbon print is known to possess, although great
permanence is claimed for the bromide. Chemical tests have shown
that the bromide prints will withstand a damp atmosphere impreg-
nated with sulphuretted hydrogen, which proved destructive to prints.
by most other processes. The effects of exposure to atmospheric influ-
ence can only be tested by time, and the introduction of this process
is of too recent a date for this test to have been effectual.
Bromide papers are prepared by the manufacturers of many kinds
of plates, and all possess qualities which may require special treat-
ment by the methods for which directions are given with each packet
of paper.
The following are the directions given for treatment of prints on
the "Ilford" bromide paper :—
No. 1. Solution potassium oxalate (neutral)
Warm water
Ammonium bromide
No. 2. Iron protosulphate
16 ounces
64
filter.
""
Warm water
Citric acid
Add 1 ounce of No. 2 to 5 ounces of
reverse order a precipitate would be formed.
20 grains
16 ounces
48
No. 1.
filter.
11
ounce
If added in the
The prints, as developed,
and without washing, are placed in the following clearing solution
for a few minutes :-
Alum
Citric acid
Warm water
"
6 ounces.
I ounce.
So ounces.
PROCESSES.
79
This solution may be used for a few prints, and then thrown away.
After rinsing in three or four changes of water, the prints are fixed
in a fresh solution of sodium thiosulphate (4 ounces to 20 ounces of
water). After washing in several changes of water for about two
hours, the prints may be passed through an alum bath; but this may
be omitted in cold weather.
Absolute cleanliness must be observed in every part of the process,
and the dish used for developing must be used for no other purpose;
stains will certainly result if the prints are touched with fingers that
are not perfectly clean. Blisters may be avoided by passing the
prints through a solution of common salt after fixing and before
washing.
All solutions must be used cold.
The directions given by the Eastman Company for developing
their bromide papers are as under:
No. 1. Potassium oxalate
Acetic acid
Hot water
•
No. 2. Iron protosulphate
Acetic acid drachm, or citric acid
Hot water
No. 3. Potassium bromide
Water
•
16 ounces.
3 drachms.
48 ounces.
16 ounces.
ounce.
32 ounces.
I ounce.
I quart.
To develop, take, in a suitable tray, of No. 1, six ounces; No. 2,
one ounce; and No. 3, half a drachm. Mix in the order given and
use cold. After exposure soak the paper in water until limp, then
immerse in the developing solution. The image should appear slowly,
and should develop up strong, clear, and brilliant. When the shadows
are sufficiently black, pour off the developer and flood the print with
the clearing solution :-
Acetic acid
Water
I drachm.
32 ounces.
Do not wash the print after pouring off the developer and before
applying the clearing solution. Use a sufficient quantity to flow over
the print; say, two ounces for a 10 x 8 print. Allow it to act for
one minute, and then pour it off and apply a fresh portion; repeat
the operation a third time, and then rinse in water, and immerse for
ten minutes in the fixing bath :-
Sodium thiosulphate
Water
3 ounces.
6
Wash thoroughly for two hours, and then hang the prints up to dry.
SQ
MANUAL OF PHOTOGRAPHY.
With a tray having a glass bottom, seven ounces of the developer are
sufficient for a print 30 × 25 in. The tray used for developing should
be kept exclusively for that purpose.
In contact-printing, very thin negatives should be printed by weak
yellow light, like that obtained from a kerosene lamp turned down
a little below the normal intensity. Strong, intense negatives are best
printed by daylight.
For enlarging by artificial light the negative should be thin and
clear; but if the enlargement is made by daylight the negative may
be of ordinary density.
Bromide paper may be utilised for making proofs from negatives
as soon as developed, without waiting to dry them, in the following
manner-Wet a piece of the A. paper, and squeegee it face down on
to the negative as soon as the latter is fixed and washed; wipe the
water off from the back of the plate and expose it to light for a few
seconds; lift the paper from the negative, and develop the print
with the oxalate developer.
If prints are squeegeed face down on to a polished sheet of hard
rubber and allowed to dry, they will have a glacé surface when removed
from the support.
Prints on bromide paper should be mounted dry—that is, they
should be allowed to dry before pasting; they should not be treated
like albumenised prints, but should be hung over a line, or laid back
down upon glass or clean paper. When dry they may be brushed on
the back with thin starch-paste, and rubbed into contact with the
mount with a soft cloth. When the prints are to be burnished, they
must be quite dry, and if a lubricator is to be used, it should be made
with Castile soap. Prints on smooth paper may be enamelled in the
usual way.
To avoid yellow prints four things are necessary:-The developer
must be acid; the clearing solution must be used; fresh "hypo" is
required for fixing each batch of prints; the washing must be
thorough.
((
Mealy" prints are caused by over-exposure. An over-exposed
bromide print may be reduced as follows:-Make a saturated solution
of chloride of lime and filter it. Take of this one part, and of water
four to eight parts, and immerse the print in the mixture, the print
having been already washed and fixed.
By masking the negative, prints with white margins may be printed
suitable for book illustrations. For this purpose paper of medium
thickness should be used.
Calotype (called also Talbotype).-All the early experiments of
Talbot were made with silver nitrate. It was necessary to print
out the pictures, whether produced by contact, with the microscope,
PROCESSES.
81
or with the camera. The next great step was the discovery that the
latent or invisible image produced on paper could be developed by
the application of a solution of gallic acid. The process is described
with full working details in the specification of the patent which was
granted to Mr. Talbot in 1841, of which the following is a summary :—
Fine writing paper was washed over with a solution of silver
nitrate, 100 grains to six ounces of water. When dry the paper was
dipped in a solution of potassium iodide, 500 grains to one pint of
water, for two or three minutes, and then rinsed in water and dried.
In this state the paper was called iodised paper, and may be stored
in a portfolio for use as required. For use take 100 grains of silver
nitrate dissolved in two ounces of water, to which add one-sixth of its
volume of strong acetic acid. This solution was called A. Solution
B. was a saturated solution of crystallised gallic acid. Equal parts of
the two solutions were mixed as required, and the solution was called
gallo-nitrate of silver. The solution was brushed over the paper or
floated on it for half a minute, then rinsed in water and blotted off.
It
may
be used wet or dried, care being taken to exclude white light,
as the paper is extremely sensitive to light. The picture was de-
veloped by being washed over with gallo-nitrate of silver, and was
fixed by first washing in plain water and afterwards in a solution of
potassium bromide (100 grains in 8 to 10 ounces of water), allowed
to remain in the solution for a minute or two, and then again washed
and dried.
This process was much altered and greatly improved by Mr. Cundell
and others. Hyposulphite of soda,¹ as it was then called, was intro-
duced for fixing the negative, and to make the paper more transparent
waxing was resorted to. The process was very popular for some years,
but was superseded by the collodion process.
In the Year-Book of Photography for 1890 will be found a list
of photographs done by Talbot and exhibited by Mr. F. H. Talbot at
a meeting of the Bath Photographic Society, and there is an account
also of early pictures made by the late Mr. R. Hunt.
Canvas, Printing on.-The canvas used in oil painting has not a
surface on which a photograph can be printed without some kind
of preparation. The surface is more or less greasy, and resists all
preparations containing water only. If coated thinly with gelatine,
1 Next in importance to the discoveries of Talbot and Daguerre of the processes
bearing their names was the means by which their pictures could be permanently
fixed. For this we are indebted to Sir John Herschel, who, in 1840, published
the fact that sodium hyposulphite would fix the photographic image more per-
fectly than by the means until then adopted. Under the heading Sodium Thio-
sulphate will be found a letter giving full particulars on this interesting matter.
As no substance has yet been found to supersede this salt as a fixing agent, the
importance of the discovery will at once be seen.
F
82
MANUAL OF PHOTOGRAPHY.
the canvas may be prepared and printed on in the ordinary way, or the
carbon process may be employed; but it has been found that any pre-
paration which prevents the oil colours coming into direct contact
with the original surface of the canvas (that is, the surface pre-
pared for painting upon) is liable to cause cracking, and in some
cases the peeling off of the picture. Many processes have been pub-
lished, but none, as far as the writer is aware, so completely meets the
difficulties of the case as one he has used for about twenty-five years,
and now publishes for the first time.
The canvas should first be freed from the surface dust of whitening
by wiping with a cloth. When the canvas is large and a portrait is
to be printed on it, the head only need be printed, or so much of the
subject as will cover a 16 × 14 plate; the rest of the picture can
readily be sketched in. In some cases a convenient method is to
place a small negative or transparency of the subject in a sciopticon
or other lantern, project the picture on to the canvas of the size
required, and then to go over the outline with pencil or red chalk.
This will give exactly the size required for the head, and from this
the proportion for the enlarged negative can be taken. When dry, the
negative may be placed on the canvas and fitted accurately to the out-
line already made. With a pencil now mark the outline of the glass
negative to serve as a guide for placing the plate when the canvas is
prepared, and to allow for ready adjustment afterwards.
To prepare the canvas take—
Calcium chloride
Spirits of wine (methylated)
I drachm.
5 ounces.
As soon as the calcium chloride has dissolved, pour a small quantity
on to the part of the canvas which is to be sensitised; take a tuft of
cotton-wool or lint and rub the surface until the salting solution is
well incorporated with the canvas preparation. The canvas will be
nearly dry when the spirit has evaporated, but it may be held for a
few minutes before a fire. Then sensitise with-
Silver nitrate.
Water
•
80 grains.
I ounce.
Go over the surface with this in the same way as with the salting solu-
tion. Dry by the fire.
As the canvas will, probably, be too large for any printing frame,
take a flat board rather larger than the negative and place it where the
canvas is to be printed; then, in a dull light, place the negative in
position, and expose to sunlight, keeping the whole covered until
placed on the board. The board is for the purpose of permitting good
contact between the canvas and negative, as the stretcher of the
ג
PROCESSES.
83
canvas prevents any other method being adopted. A thick glass out
of a printing frame may be used as a weight when placed on the top
of the negative.
In a good light the printing will be very rapid as compared with
paper. The colour of the part not covered by the negative may be
watched, and when the printing appears to be sufficient, the canvas
may be taken into a feeble light and examined, or by shading the
print the negative may be lifted by one edge and the effect judged
without taking the canvas into a darkened room. No difficulty will
be experienced in again fitting the negative in position if the printing
has not been sufficient. In case the canvas has not been evenly sensi-
tised the salting and silver solutions may be applied again and the
printing repeated. When the printing is finished the canvas should be
washed by allowing a stream of water to flow over it, and then fixed
with
Ammonia
Water
I ounce
5 ounces
or in the same proportion for as much as will be required. A thorough
washing under a stream of water for a minute or two completes the pro-
cess. As soon as dry the canvas is ready for the artist to paint upon; and
as there is nothing between his colours and the original preparation of
the canvas, he may feel perfectly sure that his work will not crack or
peel off.
As to cracking of the paint, it may be remarked that this
defect is not altogether unknown to artists quite apart from photo-
graphic preparations. Should it occur where a photograph has been
used, it cannot in any way be attributed to the photographic prepara-
tion. It will be noticed that the novelty of this process is in the use
of a salt dissolved in spirit and the use of ammonia as a fixing agent.
An aqueous solution of salt would not combine with the canvas sur-
face, and consequently the silver solution would leave the canvas
unequally sensitised. The use of ammonia is quite as effective as a
fixing agent as sodium thiosulphate, and it has the advantage that a
very slight washing removes the fixing agent.
In case of over-printing, or failure with the printing in any other
way, the print can be removed by brushing over it a weak solution of
potassium cyanide, and, after well washing under a tap, the process
of printing can be repeated; but care must be taken not to remove
too much of the surface preparation of the canvas.
Carbon Printing (Pouncey's Process).-One of the earliest processes.
for producing photographs without silver was introduced by Mr.
Pouncey of Dorchester, and was published by him in Photographic
Notes on January 1, 1859. The following is the method of preparing
the paper and the materials required :—
:84
MANUAL OF PHOTOGRAPHY.
1. Saturated solution of potassium bicarbonate.
2. Gum arabic of the consistency of varnish.
3. Vegetable carbon ground fine with a muller on a slab of stone
mixed with water.
Take equal parts of 1 and 2 (half an ounce of each to an ounce of
water) and then add one drachm of 3.
When well stirred together, the solution must be strained through
the finest muslin.
The paper must be laid on a slab of glass and levelled. The solu-
tion is spread freely by means of a camel's-hair brush and then
allowed to stand for two minutes. The superfluous fluid is then
removed with a four-inch hog's-hair "softener" and worked over the
paper in both directions until the whole is evenly spread and partly
dry. The drying may then be completed by fire heat. This opera-
tion must not be conducted in daylight.
The paper is exposed to light under a negative in the usual way.
When printed, the picture is placed face downwards in a dish of water,
carefully excluding air bubbles. After about five hours' immersion, if
the print has been over-exposed, the picture will be developed. The
final washing is done under a gentle stream of water from a tap,
assisted, if necessary, by passing a camel's-hair pencil over the paper.
The process was modified in various ways, and the system of print-
ing through the paper was introduced. A subsequent improvement
was made by using bitumen and mixing lithographic ink with the
pigment. The picture was developed with turpentine. By using
ceramic pigments the picture could be transferred to porcelain ware
and burnt in. Mr. Pouncey was awarded a silver medal and a prize
of four hundred francs by the French Photographic Society.
Catalysotype.-A process called by this name was invented by Dr.
Wood; but, as it was more curious than useful, further detail is un-
necessary here.
Celerotype. The following are the instructions for using paper
prepared by the Blackfriars Photographic and Sensitising Company,
and called Celerotype. It is a gelatino-chloride paper, and is used for
"printing out":
The paper, ready sensitised, is cut to size and placed in the printing
frame in the ordinary manner. The surface must be handled as
little as possible. Printing should be carried on until the print is
slightly darker than required for the finished picture; the deepest
shadows should have a bronzed appearance.
The prints are washed in two or three changes of water, and are
ready for toning. Almost any toning bath may be used.
The following will be found a very serviceable bath, giving rich
purple tones:-
PROCESSES.
85
'1
Sodium tungstate
Gold chloride
•
Water
No. 1. Sodium acetate (recrystallised)
Gold chloride
Water
No. 2. Ammonium sulpho-cyanide
•
•
ounce.
4 grains.
20 ounces.
ounce.
4 grains.
20 ounces.
Water.
Gold chloride
100 grains.
8 ounces.
2 grains.
Keep Nos. 1 and 2 separate. For toning take in the proportion of
20 oz. No. 1 to 6 oz. No. 2, and mix twelve hours before using.
After toning, the prints are washed in two or three changes of
water and placed in the fixing bath, containing-
Sodium thiosulphate
Water
From fifteen to twenty minutes suffice to fix.
2 ounces.
20
A combined toning and fixing bath may be used, composed of-
Water
Sodium thiosulphate
Ammonium sulpho-cyanide
Sodium acetate
Alum (saturated solution)
24 ounces.
6
I
"?
I
11
IO
Fill the bottle containing this solution with scraps of sensitised
paper, bad prints, &c., which have not been fixed. Filter, and allow
to stand for one day; then add-
Water
Gold chloride
Ammonium chloride
6 ounces.
15 grains.
30
With this bath the prints require no preliminary washing. The
prints are plunged direct into the solution, and allowed to remain until
the desired tone is arrived at.
The prints, on removal from the fixing bath, are well washed in
water, changed frequently. If the water be repeatedly changed, one
hour will suffice. The prints should then be laid in a saturated solu-
tion of alum for a few minutes, and again well washed.
When thoroughly washed, the prints are removed and laid face
downwards upon a sheet of crown or plate glass, well cleaned and
rubbed over with a little French chalk. With a squeegee they are
then pressed well into contact with the glass. When dry, they can
easily be removed by placing a sharp knife under one of the corners.
To obtain a matt or dull surface, use fine ground glass instead of
polished.
86
MANUAL OF PHOTOGRAPHY.
To retain the perfect gloss of the print the mountant should be laid
on round the edges of the print in a rim not more than a sixteenth
of an inch wide.
Ceramic Photographs.-Vitrified or burnt-in photographs may
be made in various ways. When the processes have been carefully
performed, the results are very beautiful, and, of course, absolutely
permanent. Probably owing to the difficulties in manipulation,
vitrified photographs are not commonly met with. To the skill of
the photographer must be added that of the enameller; and when
colour is attempted, that also of the miniature painter. The following
is an outline of the process as described by Mr. N. K. Chevrill :—A
perfectly clean sheet of glass is coated three times with collodion, and,
before this has completely set, the plate is put into the silver bath ;
after it has drained for several minutes, the plate is exposed in the
usual way in the copying camera to produce a transparency. The
picture is developed with pyrogallic acid. Great care must be taken
at this stage, and after being thoroughly washed the picture is fixed
with potassium cyanide. The film at one corner of the plate must
now be broken and a stream of water allowed to flow so as to com-
pletely loosen the film. The whole of the film not required is now
removed, and the picture is slipped off the glass into a dish of water.
The picture has now to be caught on a piece of glass of suitable size and
toned with iridium chloride and gold chloride. The next process is
to fix the film on the tablet where it is to remain. The tablets are
made of copper covered with white enamel and are curved; so that to
get the film evenly on the tablet a long camel's-hair brush must be
used. The plate or tablet is now ready for burning-in, and the greatest
care is necessary to secure the best results. The burning-in is effected
in a muffle-furnace, in the most convenient form of which gas-heat is
used. At this stage the effect has chiefly been to burn away the
collodion supporting the picture, and to fix the metals which form it
on the enamelled surface of the tablet. In this part of the process
all the beauty of the picture seems to be lost. To restore the pic-
ture the surface must be glazed. The enamel glaze is mixed with
specially prepared collodion diluted with alcohol. When quite cold
the tablet is covered with the glaze and burnt in.
The process is
repeated several times until the full beauty of the picture is brought
out.
Another method by which excellent results may be obtained re
quires a totally different treatment. Take the following:
Potassium bichromate, saturated solution
Albumen
Honey
Water
6 parts.
3
3
10
"
""
""
PROCESSES.
87
Mix together and keep in a dark place. After filtering the solution
the opal glass or copper tablet may be coated, dried by heat and
exposed under a transparency. The printed plate is then left for a
few minutes in a room in which there is no fire, to enable the surface
to become slightly damp. The enamel colour in a fine powder is
then dusted on and the picture is developed. The tablet or glass is
then put into water containing six drops of sulphuric acid to each
ounce of water, and allowed to remain half an hour to remove all trace
of the bichromate. Remove the plate to another dish of water and
allow it to remain an hour. When dry, the picture is ready for the
burning-in, which must be conducted as already described; as also the
glazing.
Chloro-Bromide Process.-This modification of the collodio-bromide
process was suggested by Mr. M. Carey Lea. By the addition of
copper chloride to the collodion increased sensitiveness was obtained,
and also perfect clearness in the negative.
Chromatype. Many photographic processes are curious and in-
teresting from a scientific point of view. The late Mr. Robert Hunt
originated several of this kind The Chromatype is a good example.
Mr. Hunt says:
"This process is a pleasing one in its results; it is
exceedingly simple in its manipulatory details, and produces very
charming positive pictures by the first application." The chromatype
is founded on a process by Mr. Mungo Ponton, and is described in
Hunt's " Manual," 5th edit., p. 143.
Chromo-Collotype.-A method of printing from collotype plates in
a way similar to chromo-lithography has lately been introduced by
Messrs. Waterlow & Sons. (See Collotype.)
Chromo-Photographs.-Photographs attached to curved glass, made
transparent, and then coloured on the back in oil colour, have been
introduced under many different names. Crystoleum is a name ap-
plied to this kind of coloured picture.
Chromotype. This is another name for the autotype process,
modified somewhat in the details of working.
Chrysotype. This process was one of the results of the researches
of Sir John Herschel. It is analogous to the cyanotype, but gold
chloride is one of the agents used.
Cleaning Glass.—In addition to what has already been said on
pages 91 and 92, the following methods of cleaning glass have been
recommended. The films on plates which have not been varnished
may be removed by soaking for an hour or two in water acidulated
with nitric acid; the films can be rubbed off with a strip of wood if
they have not completely left the glass. Then each plate must be
rubbed while water is allowed to flow over it, albumenised, and allowed
to dry; or a final rub with Tripoli powder or fullers' earth may be
SS
MANUAL OF PHOTOGRAPHY.
given and the plates dried with cloths or leather in the usual way.
The following method is sometimes used :—
Citric acid.
Hydrochloric acid
Water
pound.
I pint.
I gallon.
When the plates have been varnished it is necessary to use strong
common washing-soda or caustic potash, used in boiling water and
left till cold. In the latter case the plates should be touched by the
fingers as little as possible.
Plates of small size which have been coated with gelatine are
scarcely worth the trouble of cleaning. The most effectual method
for removing such films is by the use of weak hydrofluoric acid, about
1 ounce of acid to 50 of water. The acid should be used in a gutta-
percha dish, and great care be taken not to handle the plates more
than can be helped.
The old films may be filtered out, dried, and put with the silver
residues. An old felt hat serves as a good filter for this purpose.
Clearing and Reducing Solutions.-In developing gelatine dry
plates with pyrogallic acid, it often occurs that there is a want of
clearness in the shadows, or there may be too great density. After
fixing, the negative should be well rinsed in water, and the following
solution poured on and off till the desired effect is attained :-
Alum
I ounce.
Sulphuric or nitric acid
Iron protosulphate
Water
3 ounces.
20
"}
The solution may be used repeatedly, as it does not deteriorate by
keeping.
Amongst other clearing solutions which have been employed are
the following:-
Or
Alum
Iron protosulphate
Perchloride of iron
•
•
Water
Iron protosulphate
Citric acid
Ferric oxalate
Water
·
•
I ounce.
2 ounces.
4 drachms
20 ounces.
3 ounces.
I
3 drachms.
20 ounces.
Many other solutions are used, but the first one named will usually
be found to be sufficient.
Coffee Process.—As a preservative of collodion, so that it could be
PROCESSES.
89
used in a dry state, an infusion of coffee was used by Colonel Baratti.
As it proved to be one of the best, this process was popular for
a time.
Collodio-Albumen Process.-The Taupenot process led the way
in the preparation of plates to be used in the dry state, and, under
the name of the Collodio-Albumen Process, became very popular.
Fothergill, Acland, Russell, England, and many others, introduced
modifications of great value. Some of the most beautiful photographs
ever produced were made by this method. The time of exposure
was long-ten or twenty times longer than with collodion; but
over-exposure was of little consequence, as this could be corrected
in the development. Under-exposure was not so easily corrected.
Every one who practised this process had his own modification, and
each, in his own way, could produce satisfactory results. The following
is one of the simplified processes :-The collodion should be old and
porous, and the plate, after coating with the collodion, should be
washed until all greasiness disappears, and then drained for a short
time on blotting-paper. The plate must now be coated with iodised
albumen prepared as follows:¹-"Into 12 ounces of white of egg pour
2 drachms of water, to which 40 minims of glacial acetic acid have
been added, stirring the whole with a glass rod so as to mix only, not
to convert into a froth; after this has stood six or eight hours, filter
through sponge, add 1 drachm of strong ammonia, and iodise with
Potassium iodide
Ammonium bromide
Water (distilled)
The sensitising bath is made as follows:-
Silver nitrate.
Glacial acetic acid
Water (distilled)
•
70 grains.
15
I ounce.
50 grains.
45 minims.
I ounce.
This bath should be iodised by adding a crystal or two of ammonium
iodide to each pint of solution, and then filtered. The plates, which
should be quite dry, must not be allowed to remain in the bath
longer than a minute in winter, or for more than forty seconds in
summer. After removal from the bath they are to be immersed
in a dish of distilled water until they cease to appear greasy, and
then well washed under a tap to remove the last trace of silver
nitrate; they should then be flooded with a one-grain solution of
gallic acid, and allowed to dry spontaneously. They will keep good
for years; and may also be successfully developed many years after
the exposure has been made. The plate should be coated twice with
1 British Journal Almanack, 1876, p. 164.
90
MANUAL OF PHOTOGRAPHY.
the iodising solution. The solution first poured on to the wet col-
lodionised plate should be thrown away, but the surplus from the
second coating may be used for the first application to the next plate.
The object of this is to carry away the excess of water from the
washing of the collodion film.
The plates are developed by steeping in water at 100° Fahr., and then
in a solution of pyrogallic acid, 3 grains to the ounce (used also at
100°). When all the details in the picture can be well seen the
negative must be intensified with a solution of pyrogallic acid,
3 grains, and 2 grains of citric acid to the ounce of water. After
this has been poured two or three times over the plate it should
be returned to the developing cup, and two or three drops of solu-
tion of silver nitrate (20 grains to the ounce) should be added, and the
redevelopment proceeded with until the proper density is reached. If
stains appear on the plate at any stage, they may be removed by
rubbing with a tuft of cotton-wool or lint. The negatives are fixed
with sodium thiosulphate in the usual way.
Collodio-Bromide Process.-On the 9th September 1864, Messrs.
Sayce and Bolton, of Liverpool, published the details of a process by
which the bath of nitrate of silver was dispensed with. The collodion
was prepared with the bromide of silver, and the preparation of the
plate was effected by merely pouring on the collodion. Mr. Sayce
gives a full description for the preparation of the plates in the
Year Book of Photography, 1866, p. 85.
In this process we have the first step towards a method by which all
the troublesome manipulations necessary in the dry processes are got
rid of. Pictures produced by the authors of the process possessed
great excellence, and in the hands of others who modified and improved
the process equally good results were obtained. The exposure in the
camera was about twice that necessary for wet collodion.
Collodio-Chloride of Silver Process.-This process was invented
by the late Mr. G. Wharton Simpson in 1864, and met with con-
siderable success. The process consists in the use of silver chloride
in collodion. The chloride is not soluble in ether or alcohol, but
remains in suspension; and, if properly prepared, does not precipitate.
A full description of the process was published by Mr. Simpson in
the Year Book of Photography for 1866, p. 35.
Collodion Emulsion (see Collodio-Bromide Process).
Collodion Pellicle. In 1876 Mr. W. B. Bolton advertised a
collodion pellicle for the preparation of sensitive plates which could
be used either in the dry or wet state. A pellicle called by Mr.
M. Carey Lea chloriodo-bromide pellicle was also advertised by Mr.
Bolton. The process was described in the British Journal of Photo-
graphy in 1876. Collodion emulsions and pellicles are now very little
PROCESSES.
91
used; they are slow, and have very little advantage beyond that of
quick preparation of the plates.
Collodion Process (Wet).-Of all the photographic processes, no
results (if we except the daguerreotype) have ever surpassed those
produced on plates prepared by the wet collodion method; and
although the introduction of dry plates prepared with a collodion or
gelatine emulsion and in various other ways may be said to have taken
the place of the older process for certain purposes, the wet collodion
has not been superseded, and probably it may never be entirely. For
portraiture and landscape collodion is now seldom or never used, but
for some kinds of work gelatine plates are not so suitable as collodion,
and the cost of collodion, when large plates are used, is greatly in its
favour. For this reason, as well as for the very superior results which
may be obtained, a full description of the wet collodion process is con-
sidered to be desirable here. Probably not 1 per cent. of the large
army of amateurs and operators who have taken to the practice of the
art within the last ten years have ever prepared a wet plate, and, it
may be, have never seen one prepared. The modern photographer,
who, with his "instantaneous shutter" and "sixty times" dry gelatine
plates, succeeds in showing a train, moving at the rate of forty miles
an hour, as if it were standing still, has done no more than was
effected in the very early days of the art, when a wheel in very
rapid motion was shown by the light of the electric spark (than
which nothing more "instantaneous" can be used) on the prepared
paper as if at rest, and feats equally remarkable have been done on
wet collodion plates. There are great advantages in the use of gela-
tine plates, but collodion also has advantages of its own Extreme
rapidity is of very little importance in cases where collodion is now
employed.
The preparation of collodion is described in the section under its
own title.
The glass used, excepting for any special purpose, need not be
patent plate; that, of course, is better than any other, and, excepting
for its price, would always be preferred. The best flatted crown or
sheet glass, not too thin, answers every purpose. The glass must be
perfectly clean. Rouge, whitening, or fine Tripoli powder, mixed
with spirits of wine to the consistence of thick cream, may be dabbed
on the glass after it has first been well rubbed over with a pad of
flannel and rinsed under a tap; the Tripoli is then well rubbed over
the plate and rinsed off under running water. The cloths used for
drying the glass should be washed without soap, and the final polish
should be given with wash-leather or silk; in the latter case the plate
should not be used at once, as its possible electrical condition may
cause it to attract dust. When breathed upon, the glass will show at
92
MANUAL OF PHOTOGRAPHY.
once if the surface be clean; and, if not clean, the picture will pro-
bably show stains of some kind, or the film may leave the plate
while under development, or in the course of drying. There are
some advantages in using albumen as a substratum, as has already been
explained on page 69.
While coating with collodion, small plates may be held between
the finger and thumb of the left hand, but for large plates it is
better to use a pneumatic holder. The collodion should, by preference,
be poured from a "collodion pourer," which is a tall narrow bottle
having a wide mouth and a glass cover. The advantage of a bottle
of this kind is that the sediment settles at the bottom and is not
readily disturbed; the bottle should be replenished when about two-
thirds of the collodion have been used, and occasionally the sediment
should be poured into another receptacle, and used up with other
stock. If preferred, the collodion may be poured off the plate into
another bottle, but long experience has shown this to be scarcely
necessary. After the plate has been fixed on the pneumatic holder, it
should be examined for particles of dust, which should be brushed
off with a broad camel's-hair brush; the dust should not be blown off,
as not unfrequently spots of saliva may be carried with the breath,
and cause defects when the picture is developed.
The next process is to coat the plate with collodion. Whether held
with or without the plate-holder, the glass must be as level as possible;
then pour on as much collodion as may appear rather more than sufficient
to cover the plate; let the collodion flow first to the right-hand corner
farthest from you, then to the left, next, to the left corner nearest the
hand; then tilt the plate so that the superfluous fluid may flow into
the collodion bottle.
A little practice will soon give confidence and enable the operation
to be conducted without any of the collodion being spilled. There is
no necessity for haste, but there should be no time lost. If the coat-
ing is not effected in daylight, no flame of any kind should be near,
owing to the highly inflammable nature of the solution. While the
collodion is running back into the bottle, the plate should be gently
moved from side to side, with a kind of rocking motion, to prevent
the film setting irregularly. When the collodion has almost ceased
to drip, the cover may be put on the bottle and attention given entirely
to the plate to ascertain when it is ready to be put into the bath. To
ascertain this, touch the corner from which the collodion was poured,
and the finger will at once show if it is too wet; after a few seconds
(the plate meanwhile being constantly rocked) touch the plate again,
and if the collodion will not adhere to the finger it is then ready to
be sensitised.
PROCESSES.
93
The solution forming the bath should contain-
Silver nitrate
Water
This must be made slightly acid with pure nitric acid.
35 grains.
I ounce.
If good dis-
tilled water can be obtained, it should be used in making the silver
bath, unless the ordinary water available is known to be approxi-
mately pure, as is the case in Manchester and Glasgow. Rain-water
may be used; but this often contains organic matter, which may be
got rid of by exposing the solution in sunlight for a few hours. If
used fresh as thus prepared, the bath will not be found to work well,
owing to its readiness to attack the iodide contained in the collodion;
therefore, it is better to coat a plate with collodion and leave it for a
few hours in the silver solution; a small quantity of collodion poured
into it will answer the same purpose, or a crystal of potassium iodide
may be dissolved and added to the bath. Care must be taken not to
over-iodise the solution, as the presence of too much iodide causes
pinholes in the film.
66
It is better not to use the bath at once, but to allow it to stand for
a day or two, when it should be filtered. The vessel to contain the
bath solution may be of glass, porcelain, or vulcanite, preferably the
first; and for most purposes it is better to use a dipping bath." A
porcelain or glass dish may be used, but for large plates a "well
bath" made of wood thoroughly coated with black varnish is efficient.
The flat bath has the advantage of not requiring so much solution of
silver. The bath being ready and the plate coated as described, it
must be placed on the dipper with the thin end of the collodion film
foremost. This is the end opposite to that from which the collodion
was poured off, the film being thinner here because during drying the
lower end, in pouring off, retains more collodion. The plate must be
lowered with a continuous motion, since, if any hesitation occurs, a
mark will be formed across it and it will be spoilt. When a flat
dish is used, care must be taken to tilt the dish so that all the fluid
is at one end; the plate is then placed in the dish, which is at the
same time lowered, and the silver solution at once flows over the
film. The collodionised plate will be seen at once to change; a tinge
of milkiness appears, which continues to increase until it becomes of
a creamy whiteness, or, when seen in daylight, of a delicate yellow
tint. What occurs is that the iodide and bromide held in the col-
lodion are colourless; so also is the silver solution; but the iodide and
bromide of silver, which are formed when the plate is placed in the
solution, are not colourless. When the decomposition is complete,
the coated plate has acquired the quality of extreme sensibility to
light. That it is ready for exposure in the camera may be known
94
MANUAL OF PHOTOGRAPHY.
from the streaky greasiness which it at first assumes having disappeared.
No definite time can be fixed for allowing the plate to remain in the
bath, as temperature affects the result. Cold has a retarding effect; so
that in cold weather, if practicable, the dark room should be warmed.
The operation of making the plate sensitive to light must be con-
ducted in the "dark room;" that is, in the room into which only
yellow light is admitted. When removed from the silver bath, the
plate must be allowed to drain; it is then transferred to a sheet of
blotting-paper, and while resting, the back is wiped with blotting-
paper. This not only saves the silver, but also prevents injury to the
dark slide. Next, place the plate in the dark slide of the camera.
It is better to put slips of blotting-paper in the lower corners of the
slide to keep the film from touching the wood, as well as to collect
silver from the plate. Everything having been arranged before the
plate was prepared, the exposure in the camera is the next operation.
The time necessary to impress the image depends on many circum-
stances; the quality of the light, the kind of lens, the size of the
((
stop" or diaphragm, and the character of the object to be copied.
No rule can be laid down for the time to expose the plate; a few
failures will soon teach what is proper in every case, and experience
will make the practice of the process one of great certainty. The
exposure being complete, the picture has now to be developed. Pyro-
gallic acid may be used, but the following is to be preferred :-
Iron protosulphate
Alcohol (methylated)
•
Acetic acid (commercial).
Water
4 ounces.
4
""
3
65
""
وو
The commercial acetic acid is cheaper than the glacial, and answers
the same purpose. The quantity of iron may be varied to suit cir-
cumstances.
If the exposure has been perfectly timed, the picture will appear
very soon after the developing solution has been flowed over the
plate. Take more than sufficient of the iron solution than will cover
the plate, in a glass measure, and pour it gently along the plate at the
bottom, beginning near the thumb, and allow it to run towards the
top with a regular flow; if possible, do not allow any of the developer
to run off, as the silver on the plate would otherwise be washed away,
whereas it is desirable to keep it on the glass, as it is wanted to assist
in producing the image. The picture will be seen to gradually in-
crease in vigour, and when fully developed the developer may be
thrown off and a stream of water allowed to flood the plate until all
greasiness disappears. The picture thus developed may be perfect so
far as detail is concerned, but it may also happen that the image is
PROCESSES.
95
not dense enough for printing purposes. This density may be increased
by redeveloping with pyrogallic acid 10 grains, citric acid 25 grains; to
this must be added a few drops of a solution of silver nitrate, 20 grains,
water 2 ounces. The effect can be watched, and the development
stopped at once by allowing water to flow over the plate. Between
each operation the plate must be thoroughly washed. The effect of
the developing solution in producing the picture has been to reduce
the iodide of silver contained in the collodion to the metallic state
wherever the light has acted; but where there has been no change
caused by the light, the iodide is not reduced, and can be removed.
This is effected by immersing the plate in a solution of potassium
cyanide or sodium thiosulphate (hypo), either of which will quickly
dissolve the iodide, leaving the picture perfect on the plate.
When quite dry the plate may be printed from at once. If only one
or two copies are required, it need not be varnished; but the film is
very easily injured, and must be protected by varnishing if many
copies are wanted. Varnish for this purpose may be purchased ready
for use.
The negative must be warmed, but must not be made too hot ;
this can be ascertained by touching the soft part of the back of the
hand with the back of the plate. The varnish is then poured over in
the same way as the collodion, and the surplus returned to the bottle.
When drained, the plate is held before a bright fire until dry. When
quite cold, it is ready to be printed from.
The positive collodion process was for many years very popular.
Very beautiful results may be obtained, almost equal in quality to
daguerreotype, and without the disadvantage of the silver reflecting
surface. The difference between the positive and negative images is
that the positive requires to be viewed by reflected light (it is also
negative when looked at through the film, but too weak to be used as
a negative); the negative image can only be judged by inspecting it
by transmitted light; the increased density of the film takes away the
positive effect. There are some differences in the manipulation. The
collodion may be thinner, having less pyroxylin; the silver bath may
be the same as for negatives, but the developing solution can be
varied in many ways. Protosulphate of iron 10 grains, nitric acid
2 drops, and water 1 ounce will give good results.
The exposure
must be carefully timed, and the development must not be pushed so
far as for negatives. Supposing a portrait to have been taken, as
soon as the outline of the drapery can be well seen the development
has proceeded far enough. The resulting picture should have a silvery
whiteness as contrasted with the pale brown of the negative. A posi-
tive may be viewed as such from either side of the glass, but when
seen through the glass the effect is not quite so clear as when seen on
the surface, but in the latter case the picture is reversed.
96
MANUAL OF PHOTOGRAPHY.
In the practice of the wet collodion process the operator will often
meet with defects, the causes of which are not easily discovered. In
most cases the cause will be that the bath is "out of order;" but in
what way? and what is the remedy? These are questions which
the most experienced worker may not be able to answer; but usually,
after experience, the causes of most defects will be seen. When the
bath is newly made, there should be no difficulty of any kind; but
after a time it will become charged with ether and spirit from the
collodion, and will probably cause the plates to look streaky. By
leaving the plates rather longer in the bath, these defects will dis-
appear, but after long use it will be better to pour the solution into
an evaporating dish, drive off the spirit, and then add water to bring
the bath to its proper strength. The bath by constant use will become
weakened, and fresh silver must be added. Roughly the strength of
the bath may be ascertained by means of an argentometer, and for all
practical purposes this is sufficient. The best advice is, Do not tamper
with the bath; simply add fresh silver as required, occasionally giving
it a few days' rest, and it will be found to work well. If pin-holes
appear on the developed plate the cause probably is an excess of
iodide; the addition of silver remedies this. Water may be added
and the solution filtered; this will remove some of the iodide; fresh
silver must of course be added in proportion to the water used.
After very long use it may be necessary to remove organic matter
from the bath solution. In this case add sufficient carbonate of soda
to neutralise the acid, and then place the bottle in sunlight for a few
days; acidify with nitric acid-see that there is sufficient silver in
the solution-and filter; the bath should then be in good working
condition. The addition of anything to the bath beyond what is
required to make it is not recommended; the more simple its com-
position the better.
In warm weather, and when the plate has been longer than usual
in the dark slide, a deposit of silver sometimes occurs, forming what
are called "oyster-shell" markings. The use of blotting-paper in
the corner of the dark slide is often a remedy. Contact with the
wood of the frame is almost certain to cause the markings in warm
weather. (See Oyster-shell Markings.)
There are two kinds of fog which are sometimes troublesome. Fog
may be caused either by too much light in the dark room, or by the
plate not being clean. This may be detected by its being entirely on
the surface of the plate, and with care can be removed by gently
rubbing with a pad of lint under running water. The remedy for
this is the addition of a drop or two of pure nitric acid to the bath.
Dust on the plate or particles in the collodion will cause "comets"
and other defects.

PROCESSES.
97
In filtering the bath solution, only the best filter-paper should be
used; with care the same paper may be used many times. After
use, of course, the paper should be dried, put with the waste to be
burnt and the silver recovered.
If from any cause the nitrate bath should become unusable, the
silver should be thrown down in the form of chloride and a new bath
prepared. With care a bath will remain in good condition for a very
long time, no matter how much it has been used, provided, of course,
that silver has been added when necessary.
"Oyster-shell" Markings.--Few workers with dry plates have ever
seen "oyster-shell" markings, as they never occur on gelatine plates.
FIG. 33.
The defect is sometimes very troublesome when wet collodion is used,
as it is often difficult to discover its cause. One plate may be marked
near where it has rested on the silver-wire corners of the carrier,
although they may have been protected with chemically pure filtering
paper; another plate may have a mark on its centre or at the top
of the plate; but wherever they occur, they are always of the same
G
98
MANUAL OF PHOTOGRAPHY.
character. The deposit is metallic, showing that the silver may have.
been in contact with organic matter of some kind; but, it may be
asked, how has the organic matter got on to the centre of the plate?
These troublesome markings occur most frequently in warm weather
and when the plate has been longer than usual in the slide. Partial
drying of the film is to some extent the cause; and dirt on the plate,
which would have no effect when the plate was used quickly, might
set up the deposit in warm weather during a long exposure.
better to take every care in keeping the carrier well varnished and
to use bibulous paper at each corner. The paper itself is not likely
to be the cause of the markings, as they occur even when every
precaution is taken. The accompanying figure shows a very reduced
copy of this defect-the most remarkable example ever seen by the
writer, as it covered the greater part of a 12 × 10 plate.
Collographic Printing (see Collotype).
It is
Collotype. Of all the photo-mechanical processes, the collotype
is perhaps one of the most useful. It has a variety of names, such
as Lichtdruck, Phototype, Photophane, Phototint, Albert-type, Arto-
type, and many others.
The principle involved in the production of prints by any of the
allied processes is the same. A surface of gelatine is supported on
a plate of glass of sufficient thickness to bear the pressure in printing.
In some respects the process is similar to lithography. Printer's ink
is used, and is applied by means of a roller worked in a press, which
may be similar to the lithographic press; or it may have a downward
pressure, similar to a hand-press used in letterpress printing. If the
plates are sufficiently true in surface, impressions can be taken in a
letter-copying press. The printing may also be done on a machine.
The glass used must be patent plate about three-eighths or quarter
inch thick, and quite level; this is important, as the glass is some-
times slightly thicker at one end than the other. If not true, fracture
is likely to occur when passing through the press. The plates must
be ground to a fine surface with emery powder by rubbing two plates
together, or a piece of fine stone may be used. The condition of the
surface must be ascertained by washing off the emery, when the
glass, if found to be evenly ground and the grain very fine, must be
thoroughly washed and allowed to dry.
The plate may be prepared in very many different ways; the chief
point to be aimed at is the character of the grain in the gelatine,
which depends on the kind of gelatine used and the temperature at
which it is dried.
A collotype picture presents to the unaided eye the effect of an
ordinary photograph, the chief differences being in the colour. There
is the same gradation of light and shade; the same beauty of half-

Collotype, Waterlow & Sons Ltd.
"COOKHAM LOCK."
PROCESSES.
99
tone; and, when printed in ink to imitate the print on albumenised
paper and varnished, the resemblance is almost perfect. A difference
can, however, be detected if a lens of low power be used, when it
will be seen that the image is entirely produced by minute dots,
which are distributed over the whole surface of the plate. This
granulation is the result of the combination of the potassium bichro-
mate and gelatine, and of the drying at the proper temperature; the
size of the grain being determined by the degree of heat applied and
the quantity of gelatine left on the plate. The extreme beauty of
the resulting picture in collotype depends on the granulation of the
gelatine surface, as the ink is taken up in exact proportion to the
action of light on the sensitive surface. In working, the gelatine
surface requires to be damp, as the moisture prevents the ink adhering
on those parts; the hardened gelatine takes the ink just as the greasy
lines on a lithographic stone take up ink, while the wet surface of
the stone resists it; the resemblance between the two processes being
perfect in this respect.
The successful working of the collotype process depends very much
on the temperature at which the plates are dried. To effect this, a
drying-box or oven is necessary. Its dimensions will be determined
by the size of the plates in use, and whether one or more should be
dried at the same time. For plates 15 × 12, two of which are to
be dried at the same time, the box may be of the following dimen-
sions: The length should be 30 inches, width 18 inches, and depth
18 inches; four legs support the box 18 inches from the floor. The
bottom is a sheet of thin iron, and around the sides of the box sheet
iron 6 inches wide is nailed, the purpose of which is to confine the
heat from the gas jets placed below the oven. At the bottom of the
box, on one side, an aperture an inch wide is left to admit air, and
the iron bottom is covered about an inch deep with clean river or
silver sand to equalise the heat. Strips of wood are nailed at each
end of the box about 8 inches from the top, and upon these rest two
iron bars the length of the box, and 2 inches wide by about gths of
an inch thick. Through these bars screws are passed, on which to
rest the plates for the purpose of levelling; three screws in each bar
are so placed that the plates will rest on three of the pointed ends,
the bottom ends of the screws being made so that they can be con-
veniently turned. To get at the screws, the front of the box is hinged
about half way down. The top of the box is framed together, so that
flannel may be tacked on as a cover, while the centre rib serves to
hold a stem thermometer passed through a cork for testing the tem-
perature. Heat is applied by means of gas jets from burners of the
ordinary kind fixed in iron gas-piping, thus
each arm of
100
MANUAL OF PHOTOGRAPHY.
the pipe having four or five burners regulated by a tap. The connec-
tion may be made with india-rubber tubing. Much of the success in
this process depends on the drying oven, which should be carefully
constructed.
The preparation of the plate may now be proceeded with.
In order to ensure the perfect adhesion of the gelatine film to the
ground surface of the glass plate, it must be coated with a substra-
tum of-
Soluble glass (sodium silicate)
Albumen
Water
3 parts
7
""
IO "
or stale beer or ale may be substituted for the albumen and water.
The sodium silicate must not contain caustic potash. The mixture
must be well shaken or beaten into a froth, and then allowed to settle.
Filter the solution, coat the plate, and allow the excess to run off into
another bottle. It must not be used for another plate until it has
been filtered. Next place the plate in the drying oven, where the
temperature may range from 130° to 150° F., and when dry allow it
to cool. It must now be rinsed under a tap, and then allowed to dry
without artificial heat. While drying it should stand on one corner on
blotting-paper.
When dry, the plate is ready for the coating of sensitised gelatine.
The kind of gelatine to be used is of the greatest importance. It
must be neither too hard nor too soft, but of the quality called
"middle hard."
The plate may now be coated with sensitised gelatine :-
Gelatine
Potassium (or ammonium) bichromate
Water
180 grains.
20
•
4 ounces.
Soak the gelatine in three ounces of the water, then melt and keep at
150° F. for fifteen minutes. Grind the bichromate in an ounce of
water, add to the gelatine, stir well, and boil; then filter through fine
muslin, if necessary using two thicknesses, and then allow the mixture
to set. This will keep a few days. One and a half ounces will coat a
15 × 12 plate.
}
The gelatine must be melted in a porcelain vessel, which may be
placed in a saucepan over the fire, carefully protecting the surface from
dust. Many other formulæ have been published, but with care the
above will give satisfactory results. Each operator will in time find
out modifications to suit his own way of working.
In coating the plate, filter into a pouring glass more than sufficient
PROCESSES.
ΙΟΥ
of the fluid gelatine than will be required, and cover the top with
muslin tied over so that the fluid will pass through it on to the plate.
The plate must be warmed in the oven to about 150° F., and when
carefully levelled the solution of gelatine (at about the same tempera-
ture) is now poured on to the plate, which may be held level on the
points of the fingers and thumb of the left hand, the excess being
allowed to run off at the corners. When it is judged that sufficient
is retained on the plate, it is at once placed in the drying oven, and
the temperature maintained at about 120° F. until dry. The proper
temperature is important, as already explained. When dry, the plates
may be stored in a dry dark box or cupboard until required; they will
keep for a few days. It is, however, better to use them soon after
they are dried. The temperature will be ascertained by frequently
examining the thermometer, which is placed in the lid of the drying-
box as soon as the plates are ready for drying.
If used at the proper temperature, the gelatine will flow readily
over the plate, but should any difficulty be found, a bent glass rod
may be used to guide the flow of the fluid.
The negative should be prepared by masking. Place narrow strips
of thin tinfoil (which may be obtained from Messrs. Winstone, 100
Shoe Lane, London) up to the edge of the part of the negative to be
printed; the outside not covered with the foil may be covered with
thin opaque paper. Remove the back-board of an ordinary printing
frame and also the screws; place the negative in the frame, and upon
it the prepared plate; and then, instead of screws, apply pressure by
means of wedges. When the image can be seen distinctly by exa-
mining the back of the plate, it may be removed and placed in water
until all the bichromate is washed out; this will take an hour or two.
After a final rinsing under a tap, the plate may stand on one corner
on blotting-paper until dry. The image should now be faintly visible,
and the film when viewed by transmitted light should have a granu-
lation suitable to the subject; this, as already stated, is determined
by the temperature at which the plate has been dried.
It may be stated here that if, by accident, the heat of the drying-
box should become excessive, the gelatine will contract and leave the
glass; at the same time probably the surface of the glass itself will
be pulled off in patches. If, however, the temperature be regulated
automatically, this accident cannot happen.
An entirely different series of operations come into use in the next
process, that of printing from the plate.
The pressure in an ordinary lithographic printing press is applied
by means of a scraper. Impressions from the collotype plate may be
taken on a press of this kind, but it is found that a roller is pre-
ferable to the scraper.
In some large establishments machines driven
102
MANUAL OF PHOTOGRAPHY.
by steam-power are used; such machines are very costly, and are not
necessary, unless very large quantities of prints are required.
The plate holding the collotype print may be fixed on the bed of
the press, if the bed is quite level. Two or three sheets of blotting-
paper may be placed on the press, wetted, and the glass plate laid on
it; the adhesion will be sufficiently firm to hold the glass in its place.
while passing under the roller. It is somewhat safer to bed the glass
on a lithographic stone with plaster of Paris. The back of the glass
plate must be examined, and any roughness caused by gelatine which
may have run over the plate must be carefully removed, as the least
irregularity in the plate may cause it to break under pressure while
printing.
As soon as the plate is adjusted in the press the surface must be
etched, as the process of damping is called. There is really no etching
produced on the plate, and the process is merely necessary to bring
the surface into working condition. The solution for this purpose
consists of glycerine and water in about equal parts. In some cases
a few grains of common salt are added. Sufficient of the etching
fluid may be poured on and spread over the plate with the finger, so
as to cover it completely, and then left for a time; in some cases a
few minutes will be sufficient, or it may require an hour or two.
With a sponge now remove the fluid, and return it to the stock bottle,
to be used again. With a soft damp cloth dab the plate so as to leave
it just moist. The picture is now ready for inking. This part of the
process is so completely technical, and difficult to describe clearly, that
much time and trouble would be saved by obtaining a little instruc-
tion from a lithographic printer. Ink is sold specially for collotype
printing. The kind used for printing chalk drawings on stone is
very suitable. A portion of ink is removed with a palette-knife to a
clean smooth lithographic stone or slate. This is mixed with suffi-
cient middle varnish, and, if necessary, a very little turpentine; the
whole is mixed on the stone with the palette-knife, and then scraped
together and placed at one corner of the stone. The roller for distri-
buting the ink may be of leather of the best kind. It must be kept
for the purpose and regularly scraped before use, and, if necessary,
cleansed with turpentine. With the palette-knife a little of the ink
is now dabbed on different parts of the roller and distributed over the
stone until it is quite even; very little ink is required on the roller.
The plate may now be inked by passing the roller several times over
the gelatine surface in all directions. When it is seen that the inking
up is sufficient, paper may be placed in position and the impression
pulled. The first rough print will serve to show the position on the
plate, and from it a mask may be cut, so that if a clean margin of white
paper is to be shown around the print, a mask must be used and
PROCESSES,
103
placed in position while each impression is taken. It will soon be
found that according to the pressure applied while "rolling up" will
be the quantity of ink deposited on the picture. If the pressure is
heavy and the motion slow, more ink will be left on the plate; with
light pressure and quick motion, ink is taken off; so that if too much
ink has been put on, careful rolling will remove it. The first few
impressions may not be satisfactory, but by careful damping and roll-
ing the effect will improve. A plate which at first looked very un-
promising may ultimately prove to be very good, and with care will
yield some hundreds of impressions. If only a few impressions are
required, they may be printed as soon as the condition of the plate
will allow; but after the proving (that is, ascertaining that the plate
will give good prints), it is better to stand it aside for a few days,
as it will permit more impressions to be taken from it if not used
at once.
In some cases better effects in the inking are obtained by having
two rollers. After distributing the ink with the leather roller, a glue
composition roller may be used to modify the quantity of ink already
on the plate. For some purposes two kinds of ink may be used; the
first applied is thick, while with the glue roller a much thinner ink is
required; but by the use of the two rollers the inking may be modi-
fied to a large extent and excellent work obtained.
When a mask is used while taking the impression, it must be
placed in position after each inking; the paper on which the print is
to be taken is then adjusted to marks on the top and left-hand side,
so that each impression may be properly placed on the paper. Any
kind of smooth paper may be used; the surface should be even, and,
when the paper is not enamelled, it should be used damp. Damping
is effected by passing three or four sheets of the paper through clean
water, and then the same number of dry pieces are placed alternately;
a weight may then be placed on the whole and left for a few hours.
Enamelled paper is very suitable for collotype prints, but if it is new
the surface sometimes comes off. A kind called dull enamel gives
excellent results. When the surface of the paper comes off on to the
plate, it may be removed with a wet cloth. Sometimes many impres-
sions may be taken after each damping; other plates require to be
damped for each impression. No rule can be laid down as to damp-
ing, but the effect must be watched as the printing proceeds. After
each damping the surface is dabbed over with a soft cloth.
As often as necessary the surface of the gelatine picture may be
cleaned off with turpentine and then washed with water. It should
always be left clean after use. The inking slab and roller should also
be left clean.
Care must be taken that the leather roller is scraped always in
104
MANUAL OF PHOTOGRAPHY.
one direction, and one of the handles should, therefore, be marked as
a guide. A good scraper may be made out of an old table-knife.
The steel may be softened by being heated to redness; when cold, the
edge may be filed or ground away, so as to leave a hollow following
the curve of the roller. If again heated and plunged into cold water,
the temper will be restored. Resting the roller against any con-
venient support, the knife is held by its handle and tip, and then
dragged along in one direction until all the old ink is removed.
Glue rollers should be cleaned with turpentine only.
While handling the roller and working the press, the fingers become
soiled, and marks may show on the paper. To prevent this, the finger
and thumbs should be slightly touched with French chalk occasionally.
Collotypes may be printed without white margins and mounted in
the ordinary way. When this is done, the object is to imitate silver
prints. To effect this the collotype must first be sized by brushing
over the surface a thin solution of gelatine; about 1 ounce of gelatine to
Io of water. When dry, the prints are varnished with varnish com-
posed of 15 parts of white shellac in 100 parts of wood naphtha.
Negatives to be used for the purpose of collotypes must be reversed.
(See Reversal of Negatives.)
One of the most recent applications of the collotype process is for
printing in colour. Very promising specimens of this class of work
have been issued by Messrs. Waterlow & Sons after a method applied
by Mr. J. D. Geddes. This process is the application of a method
similar to colour-printing by lithography. The special mode of work-
ing cannot be described here, but by the kind permission of Messrs.
Waterlow a specimen of the work is given on the opposite page.
Colouring Lantern Slides.-The beauty of a good photograph as a
lantern slide can scarcely be enhanced by colour, however delicately
it may be applied. There is much difference in taste in this respect.
Those who wish to colour their transparencies may do so with trans-
parent oil-colours. The work requires knowledge as to working in
oil-colour; for, unless great care and judgment be used, a photograph
otherwise good may be rendered useless.
Contretype Negative. A gelatine plate, which has been made
sensitive to light with potassium bichromate, is exposed under a
negative, and then placed in water which is coloured with Indian-ink
or any other pigment. The parts not acted on by light absorb the
coloured fluid, and when the plate is fixed a negative is the result.
Crystal Cubes.-A process was patented by Mr. Swan of London
for making small pictures with stereoscopic effect by means of glass
prisms so arranged that two pictures taken in a stereoscopic camera
were made to appear in relief. The effect was produced by placing one
picture on one side of the combined prisms and the other at the back.

Chromotype. Waterlow & Sons Ltd.
"CONTEST."
Direct Reproduction of
a
Water Colour Painting.
From a
Painting by Rossi.
PROCESSES.
105
These little pictures had a very pretty effect, but they were costly and
difficult to produce.
Cyanotype. Between the years 1839 and 1851 one of the most
active workers in perfecting the art of photography was Sir John
Herschel, to whom is due the discovery of several important processes,
one of which he named Cyanotype. The process is also known under
the name of the Ferro-prussiate or Blue process. It is interesting to
notice that when the attention of scientific men was directed to the
subject, it was quickly found that many substances were affected by
the action of light, and this discovery by Herschel was one of much
importance. The manipulation of the process is very simple, and is
now very extensively used for the reproduction of plans. The formulæ
for the preparation of the paper have been varied in many ways; but,
as practised by Herschel, equally good results may be obtained. In
describing the process Hunt gives the following:-The paper is
washed over with-
Ammonio-citrate of iron
Water
•
40 grains.
I ounce.
When dry, the paper may be kept for some weeks. It is printed in
the ordinary way, and the time of exposure may vary from ten to
twenty minutes. The parts exposed to light are of a brown colour
owing to the decomposition of the iron salt, and the rest of the paper
remains yellow. Soaking in water will remove the yellow colour,
leaving the printed image unchanged. To change the colour of the
picture, it must be treated, before placing in water, with a strong solu-
tion of potassium ferro-cyanide, which changes all the unexposed parts
to a blue colour, and the colour may be strengthened by soaking in a
solution of sodium carbonate, which at the same time dissolves the
unchanged salt and fixes the image; a slight washing in water completes
the process. As already stated, the formulæ may be varied, and the
following are given as examples :-
No. I.
A. Ammonio-citrate of iron
Water
B. Potassium ferricyanide
Water
4 ounces.
14
21
15
Equal parts of A. and B. are mixed, filtered, applied to the paper
with a broad camel's-hair brush, and dried quickly.
A. Ammonio-citrate of iron
Water
B. Potassium ferricyanide
Water
No. 2.
·
64 grains.
I ounce.
48 grains.
I ounce
106
MANUAL OF PHOTOGRAPHY.
Equal parts of each are used. Paper for this process should be
well sized. If preferred, the paper may be prepared with solution A.
and afterwards placed in solution B. The colour forming the picture
is Prussian blue. And if desired, this colour may be changed in.
various ways, some of which are described by Herschel in his original
experiments.
In the process as thus described, the image appears white on a blue
ground, and in this way is very commonly used for copying plans.
The reverse of this method may be obtained, and a process by Pellet
was patented for producing blue lines on a white ground. The formula
as given by Pellet is cumbrous, and has been given in different terms
by others -
Iron perchloride
Oxalic acid
Water
616 grains.
308
14 ounces.
""
The paper is brushed over with this or floated on the solution,
dried, and printed in the usual way. The necessary exposure in sun-
light is very short, and the prints are developed by floating on a
saturated solution of potassium ferricyanide, washed in water for a
few minutes, and then placed for ten minutes in a 3 per cent. solution
of sulphuric acid.
Various other processes based on Herschel's¹ original discovery have
been described in the Photographic Journal; and in the British
Journal Photographic Almanack for 1889 Mr. J. Traill Taylor gives
a number of these methods and some results of his own experiments.
By a modification of the process black lines may be produced. (See
Black Lines.)
Daguerreotype Process.
This process, although it yielded some
of the most beautiful work ever done by the action of light on a
chemically-prepared plate, and was for ten or twelve years most exten-
sively used, is now entirely superseded. It is one of the processes
the pictures made by which are quite unalterable in their propor-
tions, so that for delicate detail requiring exact measurement (as in
astronomical work) the daguerreotype possesses advantages; and,
although the process may never be revived for practical use, a few
lines of description here are necessary.
The plates used were of silver plated on copper-that is, a plate of
copper on which one of silver was soldered, and then rolled to the
required thickness. The silver required to have a perfect polish (a
black polish, as it was called), and this was obtained by means of
1 Herschel's experiments are given in papers published by the Royal Society,
and are fully described also by Hunt in his "Manual of Photography," 5th edit.,
pp. 215-221.
PROCESSES.
107
very fine rouge powder or powdered pumice-stone mixed with oil on
buffs of velvet, and the fine burnish was often given by means of a
lathe, the buff being made to revolve while the plate was held against
it. In the absence of a lathe the more laborious plan of buffing by
hand was used. The plate was then placed face downwards on a
frame or box of a size suitable to the plate, and at the bottom of the
box was a vessel containing crystals of iodine. The ordinary tem-
perature of the room was sufficient to produce fumes of iodine, which
attacked the polished surface of the plate. It was next exposed over a
dish containing lime on which a few drops of bromine were sprinkled,
when the plate turned to a rose colour, after which it was again exposed
to the iodine vapour.
As soon as the plate appeared of a golden
yellow colour it was ready to be placed in the camera. Success greatly
depended on the correct exposure of the plate to the fumes of the
iodine. After exposure the next operation was to develop the picture.
This was effected by placing the plate in a box over a cup containing
mercury. A spirit-lamp under and outside the box caused the mercury
to vaporise, a temperature of 140° to 167° F. sufficing for this pur-
pose, while the effect could be carefully watched by artificial light
through an aperture in the side of the developing box. When the
proper temperature was reached the spirit-lamp was removed and the
temperature allowed to fall to 130° F. The hitherto invisible image
gradually appeared, and as soon as the development was seen to be
complete, the plate was removed to a grooved box and protected from
the light until it was convenient to complete the operation. The
iodine on the silver plate which has not been acted on by light has
next to be removed; in other words, the picture had to be fixed.
This was effected by plunging the plate in water to harden it. It
was then placed in a saturated solution of common salt, or, as was
soon found preferable, in a solution of sodium thiosulphate. The
effect of this was to remove the yellow colour from the plate, thus
making the picture unalterable by the action of light, and merely
requiring to be protected from the air to prevent tarnishing of the
silver surface.
Plates, as at first prepared, were very "slow," an exposure of
from three to thirty minutes being required to produce the picture.
In consequence of this slowness, the process was not adapted for
portraiture. The process was improved by exposing the plate to the
fumes of bromine, which acted as an accelerator. By this means
the time of exposure was reduced to seconds, and, consequently,
portraiture became practicable, owing to the reduced time of sitting.
Further improvements were introduced, such as gilding the picture,
which was the discovery of M. Fizeau. It was effected by covering
the plate with a solution of gold hyposulphite. On the application
108
MANUAL OF PHOTOGRAPHY.
of heat from a spirit-lamp the picture was seen to be strengthened,
and, consequently, was made more permanent. Such is a general
outline of the process.
Although, in a sense, absolutely permanent, a daguerreotype, if it
has not been properly protected from the air, is liable to become
tarnished, although the gilding is, to some extent, a protection. The
entire surface of the plate may become darkened, so that the picture
is scarcely visible; but when the tarnish is removed, the picture is
found to be as perfect as ever. If the edges only of the plate are
tarnished, it is not advisable to attempt the removal of the defect;
but if it is desired to copy the picture, then it is necessary to clean
the surface. Dust may be removed with a soft camel's-hair brush
used very lightly. On no account should the surface be touched
with the fingers or even the softest material, as this would injure the
delicate film forming the picture. To remove the tarnish, place a
small lump of potassium cyanide in a glass measure and upon it pour
about an ounce of water. Take the daguerreotype plate by the corner
with a pair of pliers and rinse it well under a stream of water; then
pour over it some of the cyanide solution, and return to the glass ;
repeat this several times until the discolouration is removed. At
first the solution of cyanide will be weak, and, in cases of slight
discolouration, will be sufficient to remove the tarnish; but, generally,
a strong solution will be necessary. As the water is gradually dis-
solving the cyanide the strength will increase, and in a short time
(never more than a few minutes) the surface of the picture will be
as clean as on the day it was taken. Wash well under a tap, and
then hold the plate over a spirit-lamp, applying the heat to the top
of the plate first, when the heat will drive off the water downwards;
the plate must not be held too long over the flame, or the silver film
may become separated from the copper. The picture must now be
replaced in its case, first carefully fastening it to the edges of the glass
with goldbeater's skin or thin gummed paper; this should be very
carefully done to exclude air.
When the picture is to be copied, it will be found better to turn
the plate on its side. Owing to the absence of granulation, a copy of
a good daguerreotype is generally more perfect than enlargements of
any other kind.
Drying Gelatine Plates.-As the direct application of heat to a wet
gelatine plate would result in the film melting, and as it may not be
convenient to wait for drying by simple exposure to the air, a quick
way of desiccating the film is desirable at times. If the plate, after it
is taken from the washing trough, be carefully pressed against blot-
ting-paper, much of the water will be removed; and the film will bear
some degree of heat without injury, while the drying will thereby be
PROCESSES.
109
hastened, but great care must be used not to make the film too warm.
The safer way is to immerse the plate in methylated spirit for a few
minutes, or the spirit may be poured on and off a few times, then
the plate may be placed in the rack in a current of air, where it
will become quite dry in a very short time. The spirit may be used
two or three times and then thrown away; or the water may be re-
moved from the spirit, but this is scarcely worth the trouble. If the
negatives are not required to be dried quickly, they may be left in the
drying rack; but they should not be too close together, or they will
dry unevenly, and possibly may become stained when the drying has
been arrested.
Dry-Plate Making. In the early days of dry-plate photography
the whole of the processes were often conducted by the photographer
himself. Hence many of the improvements in this branch of the art
are due to experimental work on the part of enthusiastic amateurs.
There can be no doubt that the greatest amount of pleasure may be
derived from conducting the whole of the process from the beginning.
The facilities now offered make the photographer less dependent on
himself; he can purchase the plates ready prepared; he may not even.
develop them himself, and his share in the production of pictures
may be no more than exposing the plates in the camera. As the
gelatine plates can now be purchased of great excellence and uniform
quality, there is some reason for not troubling to manufacture his own.
The process is not very difficult, but it involves much careful work,
and is better done in a commercial than in an amateur manner. In
all other branches the amateur should do the work himself. Formulæ
for the preparation of gelatine emulsion plates will be found treated
separately.
Dry Processes.Although the possibility of using collodion in the
form of emulsion with silver was suggested as early as 1853, it was not
until 1864 that the first practicable process was published. The credit
of this is due to Messrs. Sayce & Bolton of Liverpool. Various modi-
fications and improvements were made in subsequent years until 1871,
when Dr. Maddox published a notice of the preparation of a gelatine
emulsion and exhibited his results. A gelatine emulsion was first
offered for sale in 1873, and in the following year Kennett introduced
the first washed emulsion in the form of a pellicle. This was modified by
Wratten & Wainwright in 1878, since which date the modifications
and improvements have been too numerous to mention here.
A very
large part of what has been written on photographic matters during
the last few years has had reference to the preparation of gelatine
plates, and their proper development. The convenience of dry plates
is undoubted; but opinions differ as to the superiority, or otherwise, of
prints from such plates as compared with those done by the collodion
110
MANUAL OF PHOTOGRAPHY.
process. A good collodion negative cannot be surpassed, and one in
gelatine may, perhaps, equal the collodion; but the majority of gela-
tine work certainly is inferior to the collodion; the negatives do not
present the same qualities, they are generally weaker, and in many
cases too dense, and consequently prints from them are often deficient
in vigour.
Dusting-on Process. This process is referred to under the heading
Ceramic Photographs, but it has other applications, such as making
reversed negatives; transparencies on plain glass or opal, and back-
grounds may be added to negatives. In addition to the formula
already given the following may be used:-
Gum arabic.
Potassium bichromate
Grape-sugar
Water
•
•
6 parts.
21
"
4
72
The object is to obtain a picture having a tacky surface. As the
powder used may be black or coloured, much variety may be obtained
in the results. The picture when printed is dusted over with the
powder colour, when the powder will be found to adhere where the
light has acted.
Eburneum Process. Many processes have been practised for
utilising collodion transparencies. One of the best, introduced by
Mr. Burgess, is known by the name Eburneum. A good transparency
is necessary; the glass upon which it is taken should be previously
waxed to facilitate stripping, and it is important that the transparency
should be of the proper kind. Either of the following developing
solutions, as recommended by Mr. Burgess, may be used :—
Iron protosulphate
Citric acid
Glacial acetic acid
Water
5 grains.
5
10 minims.
•
I ounce.
Or-
Pyrogallic acid.
Citric acid
Glacial acetic acid
Water
3 to 6 grains.
3
""
20 minims.
I ounce.
Fix the picture with potassium cyanide, and, after well washing,
tone it with gold. When dry, strips of paper should be pasted round
the plate on the back, so as to allow them to be turned up to form a
kind of dish. When carefully levelled the plate is ready for the next
part of the process. Take of good gelatine 5 ounces, water 20 ounces,
glycerineounce, and zinc oxide 1 ounce. Soak the gelatine, then
dissolve and filter it. The zinc must now be rubbed up in a mortar
PROCESSES.
III
with the glycerine and 1 ounce of water, and then poured into the
gelatine. After a few hours the coarser parts of the zinc will have
settled, and then, if carefully heated, the solution may be poured off,
leaving the sediment; or the mass may be turned out when set and
the bottom part cut away. Sufficient of the gelatine emulsion (at
about 100° F.) may now be poured on to the levelled plate; 2
ounces will be sufficient for a 10 x 8 plate. When set, the plate
may be allowed to dry spontaneously or in a drying box, and when
dry the film may be detached in the usual way.
Electro-Phototypy.-A patent has been granted to Mr. H. Sutton
for "an improved process for converting a photographic image on a
gelatine surface into a relief or intaglio printing surface." The object
of this process is, to a certain extent, to supersede the half-tone
etching processes on zinc or copper. A negative is taken on a
gelatino-bromide plate through a screen of lines in the usual way,
and by heating up to 212° F. a relief is obtained, which is then
converted into a block by electrotyping. The process is capable of
yielding a printing surface in half-tone; but as there is no apparent.
means of modifying the surface, as can be done in the half-tone zinc
etching process, the usefulness of the new method must be limited
to such subjects as do not require the finer class of work.
Enamelling Paper Prints.-A very highly polished surface may
be given to photographs on albumenised paper by means of hot
rolling; but a glaze very much exceeding this is obtained by enamel-
ling, as it is termed. A plate of glass free from defects is thoroughly
cleaned and then rubbed over with French chalk, or a few drops of
a solution of white wax in ether may be rubbed over the plate with
a piece of lint, and then cleaned off with a dry soft cloth. A coating
of collodion (not iodised) is now applied to the plate; when quite
dry, this is covered with a solution of gelatine. Soak half an ounce of
gelatine in six ounces of water for an hour or two, then dissolve it by
placing the vessel containing it in hot water. If the gelatine is not
sufficiently clear, it may be clarified by boiling in it some albumen
which has been whisked in a small quantity of water. When filtered
through lint or two thicknesses of muslin, the plate may be coated
with the hot gelatine. When set, it can be put away till required.
When many prints are to be enamelled, sheets of glass large enough
to hold several prints may be used. There are several ways of apply-
ing the prints. They may be wetted and then placed on the gela-
tinised plate, care being taken to remove all air-bubbles. The prints
may be coated with the gelatine and applied as soon as the surface
has set. When the plates and prints are small, they may be placed
in contact in the gelatine solution and the surplus squeezed out. The
greatest care must be taken to exclude air-bubbles. When quite dry,
I 12
MANUAL OF PHOTOGRAPHY.
the prints will readily leave the glass if a penknife be passed under
one edge. Prints treated in this manner have a very beautiful appear-
ance, as details will be shown which otherwise would not be seen.
There can be no doubt that the collodion acts as a protection to the
print, which, if it has been carefully finished in other respects, may
thus be rendered more permanent. There is, however, one disad-
vantage; the surface is very liable to injury by rubbing against the
opposite prints if placed in an album. In mounting, the prints must
be attached by the edges only.
A silver print on albumenised paper may have its gloss increased
by being allowed to dry on a ferrotype plate, on to which it has been
squeegeed.
Enlarging and Copying.—When an object is to be enlarged, an
ordinary camera may be used, if it can be extended to a sufficient
length; but it is more convenient to use apparatus which has been
specially constructed for the purpose. A camera of this kind is
described and illustrated in Part III., and the solar camera is also
referred to.
If a special camera is not available, one of the ordinary kind may
be arranged on a board at one end, secured by a screw running in a
slot cut in the board; at the other end of the board is a stand sliding
between strips of wood attached to the sides of the board, which
stand is made to hold carriers for the different sizes of plates to be
copied. Laths of wood placed at the top of the camera and the nega-
tive carrier will serve to hold a cloth to exclude light between the
lens and the negative or positive which is to be enlarged or reduced.

FIG. 34.
Fig. 34 shows a method for using artificial light from a sciopticon
or other form of lantern; it also illustrates what is described in
the previous paragraph, substituting the ordinary camera for the
lantern. If attached to a board, as above described, it may be
PROCESSES.
113
used in the way indicated, or may be turned towards the sky. It
will be noticed that two cameras may be utilised in this manner;
in the arrangement described above it may be turned towards the sky,
and used without darkening the room.
way for making en-
largements or reduc-
tions, the lens being
placed in the central
division.
Another simple and
convenient way to pro-
duce enlargements is
Fig. 35 shows a convenient

FIG. 35.
to adapt a room so that a reflector (which may be a mirror, a sheet of
white cardboard, or opal glass) may be made to reflect light through
an opening in the window, through the negative or positive to be
enlarged, the lens being arranged on a table and the plate or paper
fixed to a movable easel, the various parts being capable of adjust-
ment to the sizes required. (See Camera.)
In countries where solar light may be used more constantly than in
England, the solar enlarging camera is very convenient when the
object is to print out; but, as the modern processes have simplified
the operation of enlarging, this form of instrument is not much used
on account of the necessity for constantly regulating the reflecting
mirror.
In using a camera, or any other enlarging apparatus, it is con-
venient to know at what distance the lens should be from the object
and the plate from the lens, in order to produce copies (larger or
smaller) of the required dimensions with as little trouble and loss of
time as possible. This can be done by referring to the table.
To use the table, suppose the copy is to be enlarged five diameters
and that the equivalent focus of the lens is 4 inches; the ground glass
of the camera must then be 24 inches from the lens centre, and the
object 4 inches distant. In a reduction, the positions are exactly
the reverse. For lenses of greater focal length than 9 inches the table
can be used by doubling the figures, which will represent the focus.
of the lens to be used.
The principle on which this table is constructed is as follows:-
The focal length of the lens must be multiplied by one more than the
number of times of the enlargement—that is, suppose the focus of
the lens to be 10 inches and the times to be enlarged 3; multiply the
Io by 4, and we have 40 inches as the distance of the lens from the
sensitive plate; and if we divide 40 by 3, we have 13 as the dis-
tance of the lens from the object.
H
114
MANUAL OF PHOTOGRAPHY.
Focus
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TABLE FOR ENLARGEMENTS.

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Ferrotype.—One of the many processes worked out by Hunt was
called by him Ferrotype (also Energiatype). The paper was prepared
by washing over with—
Succinic acid
Common salt
5 grains.
5
Gum arabic (mucilage)
Water
drachm.
I ounce.
When dry, the paper was drawn over the surface of a solution of
silver nitrate containing 60 grains in 1 ounce of water.
The paper
was dried in the dark, and when dry was ready for use. It would
retain its white surface if preserved in a portfolio. The paper could
be used in the camera for landscapes, when an exposure of half a
minute was sufficient, and about three minutes for a portrait. The
PROCESSES.
115
image remained invisible until developed in one drachm of a saturated
solution of iron protosulphate, and two or three drachms of mucilage
of gum arabic. When the picture was completely developed, which
was very rapid, the further action of the solution of iron was stopped
by sponging the surface of the print with water. The fixing was with
ammonia or sodium thiosulphate, after which the print was thoroughly
washed.
In this process Hunt showed the value of the salt of iron as a deve-
loping agent.
Ferrotypes.-Thin plates of iron covered with black varnish (to
protect the metal from the silver solution) are used in this process
instead of glass. There is no difference in the manipulation; the
same collodion, bath, and developing solution which will give good
positives on glass will yield good ferrotypes. Gelatine emulsion may
be used on ferrotype plates. The ferrotype process is now almost out
of date.
Film Photography.-The discovery of some means by which pho-
tographs could be taken without the use of glass or paper has been
the wish of all photographers who make landscape-work their study.
Many methods have been proposed. As early as 1871 the late Mr.
Walter Woodbury suggested a method of using films instead of glass
for negatives; and also, that the film should be used in bands in a
suitable carrier, so as to avoid the use of the ordinary dark slides. Mr.
Warneke in 1876 used collodion or bromide emulsion on paper so
prepared that the film could be separated from the paper after use, a
roller-slide being used in the camera instead of separate dark slides.
Pumphrey of Birmingham, Carbutt, and Vergara introduced films ;
but the Eastman Company appear to have made the nearest approach
to perfection in the substitution of glass by celluloid. The composi-
tion of this substance is allied to pyroxylin, being formed by the
action of sulphuric and nitric acids on paper (or cellulose in any
other form); it is then dissolved after complete washing, and mixed
with camphor. The celluloid film is coated in the same way as glass
with the sensitive gelatine, and the after-treatment is the same as for
glass. As the flexible and transparent film is composed of matter
nearly allied to gun-cotton, it is necessary that precautions be taken to
avoid decomposition and possible explosion, although it is said that
some kinds are not explosive. The films form a very perfect substi-
tute for glass.
Fixing. The term fixing as applied to the daguerreotype picture,
means boiling a solution of sel d'or upon the plate, and so fastening
the image that it could not be easily removed. In other processes
fixing signifies the removal from the film of the sensitive material
which forms no part of the image. Potassium cyanide, sodium thio-
116
MANUAL OF PHOTOGRAPHY.
sulphate, or ammonia are usually employed for this purpose. As the
sensitive haloid salts of silver are soluble in a solution of one or other
of these substances, the solvent to be used in each case is referred to
in the descriptions of the various processes.
Fluorotype. In 1844 Hunt published experiments with the fluo-
rides, showing that pictures could be taken on paper in the camera
by using solutions having the following formulæ :—
I. Potassium bromide
Water.
2. Sodium fluoride
Water.
20 grains.
I ounce.
5 grains.
I ounce.
Mix a small quantity of these solutions together when the papers
are to be prepared, and wash the papers once over with the mixture.
When dry, apply a solution of silver nitrate, sixty grains to the
ounce of water. These papers keep for some weeks without injury,
and become impressed with good images in half a minute in the
camera. The impression is not sufficiently strong when removed
from the camera for producing positive pictures, but may be rendered
so by a secondary process.
The photograph should first be soaked in water for a few minutes,
then placed upon a slab of porcelain, and a weak solution of iron
protosulphate brushed over it; the picture almost immediately ac-
quires an intense colour, which colouring action should then be
stopped by plunging it into water slightly acidulated with muriatic
acid, or the blackening will extend all over the paper. It may be fixed
by being soaked in water, and then dipped into a solution of sodium
thiosulphate, and again soaked in water as in the other processes.
Fothergill Process.-It was one of the earliest and best of the
dry-plate methods, but is now entirely superseded by the gelatino-
bromide process.
Gelatino-Bromide Process.-This process has in the last dozen
years made a complete revolution in the practice of photography. As
early as 1853 Gaudin had experimented with gelatine. Still earlier,
albumen had been extensively used; but for dry-plate work collodion
emulsion appears to have received almost exclusive attention until
1871, when Dr. Maddox published a process in which gelatine took
the place of collodion. Various modifications were suggested in the
preparation of the emulsion between 1871 and 1878, when, in the
latter year, Mr. Bennett published the fact that by digesting the
emulsion at 90° F. great sensitiveness was obtained. The importance
of gelatine emulsion for making dry plates may be dated from this
valuable discovery. Mr. Bennett's discovery was first published in
the British Journal of Photography in 1878.
PROCESSES.
117
In 1880 Mr. W. J. Wilson was awarded the
prize of £50 offered
In a very condensed
by Mr. Paget for the best emulsion process.
form the method is as follows, and this may be taken as representa-
tive of the process generally. The following is the formula em-
ployed:-
Hydrochloric acid (pure)
•
Distilled water
No. I.
No. 2.
I fluid drachm.
+
12 ounces.
Distilled water
Ammonium bromide
Nelson's No. I gelatine
Ι
3 ounces.
210 grains,
80
In
"Twenty minims of the No. I solution are introduced into the
whole of the No. 2 solution, and the gelatine left to swell.
another glass vessel 330 grains of silver nitrate are dissolved in three
ounces of distilled water. A small quantity, about two fluid drachms,
of the latter is poured into a test-tube, and diluted with an equal bulk
of distilled water. The solution of the bromised gelatine is then
rendered complete by immersing the bottle in hot water, and the
dilute silver nitrate is added all at once. The bottle is then shaken,
and the remainder of the strong silver solution added in quantities of
half-an-ounce at a time, shaking, as before, after each addition. The
emulsion is then boiled for fifty-five minutes, and, when cooled down
to 90° Fahr., one ounce of Nelson's No. 1 gelatine or the X opaque,
which has been previously swelled and dissolved in water, so as to
measure four ounces, is added. When set, the emulsion is squeezed
through canvas into a pan containing three ounces of a saturated
solution of potassium bichromate in three pints of cold water, and
allowed to remain in it for one hour. The emulsion is then squeezed
through canvas into clean cold water, and the operation repeated
immediately, the emulsion remaining in the last wash-water for half-
an-hour. The addition of two ounces of alcohol and sufficient water
to make up the solution to twenty ounces completes the process, and
the emulsion, when filtered, is ready for use." 1
It is of the greatest importance that the proper kind of light be used
while preparing any sensitive emulsion. Mr. Bennett gives promi-
nence to this, and recommends the use of a ruby-coloured hock bottle
to shield the light. The bottle is prepared by cutting off the neck
and bottom; a candle can then be inserted and held in position by a
suitable holder, which serves as a stand, while a cap of tin held in place
at the top allows of the escape of smoke from the candle, and also pre-
vents the escape of white light.
Another important point to be observed in the preparation of gela-
1 Year-Book of Photography, 1882, p. 130.
118
MANUAL OF PHOTOGRAPHY.
tine emulsion is that the most suitable gelatine be used. Some samples
are acid, and this kind should be employed when ammonia is not in
the formula. The gelatine should take up very little water and make
a hard jelly. If spots occur where the film is dry, the gelatine con-
tains fat, and this may be corrected by the addition of ammonia.
In his work on "Modern Dry Plates," Dr. Eder describes three
methods. The first refers to the preparation of the emulsion with
ammoniacal silver nitrate, which gives plates about six or seven times
the sensitiveness of wet collodion.
In the second method the emulsion is prepared by boiling and sub-
sequent digestion with ammonia. In this way plates of great sensi-
tiveness are obtained; but much care is required. The extreme
sensitiveness depends on the fact that the modification of silver bro-
mide forms very rapidly at temperatures between 60° C. (140° F.)
and 100° C. (212° F.), and that the sensitiveness of such emulsion,
in itself very great, can be still further increased by subsequent treat-
ment with ammonia at a low temperature.
The third method is for the preparation of an emulsion at low tem-
perature.
When a small quantity of emulsion is examined on a piece of glass
by transmitted light it appears red. As the boiling proceeds this
colour changes to blue; and the completion of the process is deter-
mined in this manner.
One of the most important parts of the process of making gelatine
plates is the drying, and special means must be adopted to effect this.
A drying cupboard is usually employed. This may be a box of suitable
size, having rods across it inside, on which the plates, when the films
have set, are placed. Air is admitted through a hole at the bottom,
protected so that no white light can enter; while another aperture at
the top of the box permits the exit of the air, which has been warmed
by means of a small gas jet in the bottom air-tube. Other ways for
drying the plates may be adopted. A suitable box or cupboard may
have a coil of piping, through which water flows that has been heated
in a cistern connected with a small gas-stove. Apertures are left in
the bottom and top of the box to admit air and allow its escape.
Gelatine emulsion may be spread on paper, and can also be used for
lantern slides or for printing out.
If kept dry, gelatine plates will retain their sensitiveness for a long
time, and the development of exposed plates may be delayed, in the
writer's experience, at least six years. It is important that the sensi-
tive plates be kept excluded from the air as much as possible, other-
wise there may be deterioration, which is seen as a darkening of the
plates, starting from the edges.
The subject of the preparation of gelatino-bromide plates is alto-
PROCESSES.
119
gether too large to be treated in a few pages: the number of processes
and modifications is very great. In 1888 a list of the different kinds
of dry plates in the market contains over a hundred names; probably
all were prepared by formulæ differing more or less from each other, and
therefore it will be seen that to do more here than to indicate the method
of production is quite impossible. The special works on the subject,
such as those by Eder, Abney, Burton, and others, should be consulted.
Gelatino-Chloride Paper (Ilford).-Papers prepared with gelatine
in place of albumen have been introduced (see Aristotype), and
amongst others is one by the Ilford Company. The uncertain stabi-
lity of prints on albumenised paper has, from its first introduction,
made it desirable that some substitute for albumen should be found;
but although many processes, which gave results of great beauty,
and
in some cases equalling those on albumen, have been introduced,
albumenised paper is still used to a greater extent than any other.
The cause of the preference, probably, is that detail is not lost in the
shadows, as is the case in some other processes; and the gloss given
to the paper by the albumen is not so objectionable as that obtained
when prints by other methods have been dried on glass. The most
recent introduction is that by the Ilford Company. It is a gelatino-
chloride paper, to be printed-out in the same way as albumenised
paper. It may be dried either with a glazed or a matt surface. The
paper can be purchased ready for use; its price is about the same as
that of albumenised paper, and it has the advantage of not dete-
riorating by keeping.
The prints, which do not require to be deeply printed, as they lose
little in the after processes, must first be washed for ten minutes in
several changes of water. The toning bath is-
Ammonium sulphocyanide
Gold chloride
Water
•
30 grains.
2,
16 ounces.
This solution is recommended for the paper, but any of the older for-
mulæ may be used if desired. The prints must be constantly moved
to prevent their adhering together, which would cause the toning to
be irregular. The toning is complete in three or four minutes, and
the effect may be judged by looking through the prints, when, if the
ordinary purple tone is desired, the colours should appear warm in the
deepest shadows. The appearance of over-toning is lost in the fixing.
Careful washing is necessary after toning, or the action of the toning
solution will be continued. The fixing bath contains-
Sodium thiosulphate
Water
in which the prints must remain ten minutes.
3 ounces
20
11
120
MANUAL OF PHOTOGRAPHY.
If there should be any tendency in warm weather for the gelatine
to become soft, or if the prints are to be burnished, an alum bath
should be used before toning-4 ounces of alum to 20 ounces of
water.
There can be no doubt that prints on this paper have a very near
approach to those on albumenised paper, but time must determine if
they are permanent. There are now so many processes all capable of
yielding most excellent results that it is impossible to say that any one.
is the best, while tastes differ even more than the processes. The pro-
cess employed should be adapted to the picture; a matt surface will
suit some subjects, while others would be improved by adopting a
glazed surface.
Gold-Printing Process.-In 1852 some prints on plain paper were
shown by Mr. Hennah at the first Exhibition of the Photographic
Society in the room of the Society of Arts. Referring to these prints,
Mr. Spiller, in the Photographic Year Book, 1883, refers to their
exceptionally good quality; and, as the result of his own experience,
says as follows:-Instead of employing gold for the toning of his
silver prints by a subsequent operation, Mr. Hennah commenced by
adding gold to the salting solution, and then had only to fix with
plain sodium thiosulphate to get the neutral tones so much desired.
He prescribed-
•
Gold chloride
Ammonium chloride
Water
60 grains.
I 20
nces
20 ounces.
On this the plain paper (Towgood's or Turner's) was floated, and hung
up to drain and dry, then sensitised in a 60-grain bath of ammonio-
nitrate of silver made as usual. The paper quickly dried, and was
exposed to light under the negative until moderately over-printed.
Without washing, the prints were immersed in a fixing bath pre-
pared as follows:-
Sodium thiosulphate
Silver iodide
Water
(C
5 ounces
10 grains
I pint
to which was added 1 ounce of a 60-grain ammonio-nitrate of silver
solution; stress being laid upon the maintenance of alkaline con-
ditions by further addition, if necessary, of ammonia. The prints
were washed in several changes of boiling water, or in the ordinary
way with cold water, and being now very tender, were taken out and
dried upon glass rods; finally, laid face downwards on glazed bibulous
paper, and ironed on the back. The finished proof should have pure
whites and fine ivory-black shadows. The author, in his original paper,
vouches for ten years of permanence, and he told me in 1872 that he had
PROCESSES.
121
never known a case of fading wherever the process had been fairly
carried out. The somewhat increased consumption of gold was more
than compensated by the perfection of the result."
Green Photographs. If paper prepared with a solution of uranium
nitrate (60 grains to the ounce) be exposed for a few minutes under a
negative, very little visible effect is produced, but when washed in
water and then brushed over with a weak solution of potassium ferri-
cyanide, a red picture is the result. While still wet after washing, if
placed in a solution of sesquichloride of iron (10 grains to the ounce)
the colour of the print is changed to green.
Gum-Gallic Process.-In this process, introduced by Mr. R. Manners-
Gordon, the collodionised plates are well washed after being sensi-
tised. The following preservative is used:
I. Gallic acid
Water
2. Gum arabic (picked white)
3 grains.
ounce.
20 grains.
Sugar-candy.
Water
•
5
59
ounce.
The two solutions are mixed together and filtered shortly before use.
The preservative solution is flowed over the plate twice, and after the
first time the solution is returned to a separate cup, used once more,
and then thrown away. After the second application the plates are
allowed to dry spontaneously in the dark. Plates thus prepared were
said to keep well, and were about as quick as wet collodion.
Heliography.—The process in which he used bitumen of Judea was
named by Niépce Heliography. Bitumen possesses the property of
hardening when exposed to sunlight, so that any part of a surface
covered with a thin layer which had not been affected by light could
be washed away with any substance which would dissolve the bitu-
men; for this purpose Niépce used oil of lavender. In this process
the object was to form a picture on a lithographic stone, so that, after
treatment with acid to etch away the stone, the picture could be printed
in the usual way; but no satisfactory result was obtained, and after-
wards metal plates were substituted for the stone. As this was the
foundation of the process of zinc-etching as at present largely used,
the process will be described under its modern name of Zinc-etching.
Honey Process.-One of the methods of keeping collodion plates
moist was the use of honey, as suggested by Mr. Shadbolt.
Indian-ink Outlines (see Magic Photographs).-Make a print on
plain salted paper, not too darkly printed, and fix without toning.
The print may now be worked over in Indian-ink lines in the manner
of an etching or woodcut, and any degree of finish may be given to
the drawing. The Indian-ink should be of good quality, which may
122
MANUAL OF PHOTOGRAPHY.
be determined by making a few lines on paper and then allowing a
stream of water to flow over it after the ink is dry. If the ink does
not run, it will answer for coating the drawing. The print may now
be placed on a solution of mercury chloride, which will remove all
trace of the photograph, leaving the lines of the drawing. The print
must be thoroughly washed. If placed in a solution of copper
sulphate, to which has been added a pinch of sodium chloride, the
picture will bleach; but it must be very thoroughly washed after-
wards, or the photograph will reappear on exposure to the light.
When a photo-lithograph or line block is required from a half-tone
photograph, this method will be found very useful, as when the draw-
ing is skilfully done the effect is good. If any defects appear after
the print is bleached, they may be corrected with Indian-ink. The
plate giving a view of the Manchester Royal Exchange was made in
this way.
Iridescent Photographs.-The following process is said to give
pleasing results. It is described by Mr. Burbank, who states that
M. Geymet is the inventor.
the inventor. All parts of the process may be con-
ducted in full daylight. A glass plate is coated with the following
solution :-
Gum arabic
Glucose (sat. sol.).
Ammonium bichromate (sat. sol.).
Distilled water
75 grains.
I drachm.
3 drachms.
31 ounces.
This must be filtered three times and then exposed to light for some
hours. To facilitate the coating, the plate should be dipped in water
before pouring on the sensitive solution. The fluid is flowed over
two or three times; the first is thrown away, and the next returned
to a separate bottle to be used for the first of the next plate. Ex-
pose well under a strong negative. To develop the picture, bronze
powder is rubbed over the plate with a tuft of cotton-wool; if neces-
sary to make the image take the powder, the plate must be breathed
upon.
As soon as dry, the collodion is washed to remove the yellow
colour, and then dried. The iridescent effect is produced by coating.
the plate with collodion as under :-
Alcohol
Ether.
Gun-cotton.
·
7 drachms.
18
"}
5 grains.
After
The positive is again washed, and dried quickly without heat.
development the plate is coated with plain collodion. The plate may
then be coated on the back with black or coloured varnish.
Kallitype.—A process has been patented by Messrs. J. Lewis &

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PROCESSES.
123
Co. of Birmingham which they call Kallitype. The paper is prepared
with a strong solution of neutral ferric oxalate, and, when dry, is
printed until the detail in the densest part of the negative is faintly
indicated.
As this paper is said to be six times more sensitive than the ordi-
nary silver paper, it must be used, in filling the printing-frames, in
yellow or weak daylight. The following are the instructions given
by the patentees :-
Care must be taken that the paper is quite dry when put out to
print, or it will not be so easy to determine the proper exposure, and
the resulting print will not be so good a colour. It may be necessary
in damp weather to dry it carefully, but it must not be made too hot
in drying, or the paper will be fogged. Five to ten minutes in a good
light, or from two to three minutes in sunlight, is an average expo-
When the detail in the densest parts of the negative is faintly
indicated, the printing must be stopped, remembering that the whole
shows but faintly before development.
sure.
The prints must be quite dry before developing; they are floated
face downwards upon the developing solution (used cold) for ten to
twenty seconds, and are then placed face upwards upon a piece of
clean glass for a minute or two, to gain brilliancy and depth. They
are next immersed in washing solution No. 1, where they must
remain for at least twenty minutes. This washing solution may be
used repeatedly, as long as it serves its purpose of removing the
yellowness from the prints. When developing prints with plain
flat backgrounds, be careful to well shake the developing solution in
the dish before floating, otherwise markings will sometimes occur.
The prints are next washed consecutively in No. 2 and No. 3 wash-
ing solutions; they must remain in each of these baths for about
ten minutes, and after the last bath they are washed for a few
minutes in water and dried. The prints must be moved about
freely in the washing solutions, and as soon as No. 3 shows the
least tinge of yellow when viewed in bulk, it must take the place
of No. 2 and fresh solution poured out for No. 3, otherwise the prints
will be yellow.
Silver nitrate
Sodium citrate
Developing Solution.
50 grains.
I ounce.
Potassium bichromate
Water.
Ammonia, '880
I grain.
IO Ounces.
drachm.
Dissolve the silver nitrate in about an ounce of the water, and
the sodium citrate and potassium bichromate in the remainder, and
mix. Add the ammonia and filter.
124
MANUAL OF PHOTOGRAPHY.
Washing Solution No. 1.
Kallitype developer
Sodium citrate.
Water
ounce.
2 ounces.
20
""
To be returned to bottle for future use, as previously described.
Washing Solution for Bath Nos. 2 and 3.
Sodium citrate
Ammonia, 880
Water
I drachm.
2 drachms.
I quart.
If the print has been insufficiently exposed, it will develop very
slowly, and will require a longer floating upon the developing solution.
The developing solution may be used over and over again, and
with care will serve for a great quantity of prints. The developer
which has been used should be kept separate, and when the prints
show any lack of brilliancy, should be set aside to be restored. This
is effected by adding to every 10 ounces 20 grains of silver nitrate
dissolved in a small quantity of water. Prints not developed the
same day as printed must be carefully kept quite dry.
Washing solutions for baths No. 2 and No. 3 must always smell
distinctly of ammonia, or the prints will not be properly fixed.
When printing from very thin negatives, greater contrast may be
secured by the addition of more bichromate of potash to the developer.
A stock solution containing 8 grains to the ounce will be found use-
ful. One drop, or more if necessary, added to each 10 ounces of
developer, will give greater brilliancy and contrast.
This process
gives excellent results.
A process called Kallitype No. 2 has been introduced, in which the
prints are developed. Albumenised paper can be used, or prints with
a matt surface can be made. The same care in printing must be
observed as in the other process. To obtain black tones the prints
are immersed singly in the following solution :-
No. 1. Rochelle salt
Borax
Potassium bichromate, 10 to 12 minims of a
solution, 20 grains to the ounce.
I ounce.
Water
IO ounces.
For Purple Tones.
No. 2. Rochelle salt
I ounce.
Borax
Potassium bichromate solution
Water
For Sepia Tones.
No. 3. Rochelle salt
Potassium bichromate solution
2 drachms.
10 to 12 minims.
10 ounces.
ounce
6 minims.
PROCESSES.
125
Several prints may be developed at the same time, the usual care
being taken to avoid air-bubbles. The prints are fixed by immersion
for ten or fifteen minutes in-
Ammonia (strong)
Water
•
4 drachms.
I quart.
To ensure perfect fixing, a second bath of the ammonia solution is
recommended. A few changes of water during about fifteen minutes
is sufficient for washing the prints; after which they may be dried
and mounted.
2
The paper is prepared with ferric oxalate and ferric nitrate, silver
oxalate and silver nitrate. On exposure to light the ferric oxalate is
reduced to ferrous oxalate Fe(C₂O4)3 = Fe2(C2O4)2 + 2CO2; which by
contact with the Rochelle salt (NaKC,H4O6) in the developer reduces
silver salt in contact with it to the metallic state. At the same time
the Rochelle salt and the iron salt form ferric tartrate, Fe,(C₁H₂O6)3;
1406)3
the ammonia dissolves the silver salt, but does not precipitate the
ferric tartrate.
4
Kennett's Pellicle.-One of the earliest workers with gelatine
emulsion was Mr. R. Kennett, who patented a process for the
use of gelatine instead of collodion combined with salts of silver.
The compound of iodide or other salt of silver with gelatine was
cut into strips, washed to remove the free salts, and afterwards
dried. In the dried state the "pellicle" could be stored for use.
When required, it could be dissolved in water and plates coated with
it in the usual way. Plates thus prepared were much more rapid
than wet collodion. This appears to have been partly the cause of
the want of commercial success with the pellicle, as over-exposure
was generally the result in hands used to slow processes. Fog also
was complained of, but this was probably due to the presence of too
much light, as the yellow light suitable for wet collodion was not
suitable for the new pellicle. (See Collodion Pellicle.)
Lantern Slide-making.-A good transparency on glass is perhaps
one of the most beautiful kinds of photograph, and a good lantern-
slide exhibited by the oxy-hydrogen or electric light, enlarged as it
may be to 20 or 30 feet in diameter, forms one of the most valuable
aids to the lecturer, who thus has the means of affording his audience
pleasure and instruction in a way that no other kind of illustration
permits. There are many points to consider in making lantern-slides;
the original negative must be of good quality; the proportion should
be considered, and, although the proportion of a picture 7 × 5 more
nearly resembles the shape of landscape pictures as usually painted,
it does not follow that when that size is reduced to 31 × 31, the
size now considered to be the standard, the effect on the screen
126
MANUAL OF PHOTOGRAPHY.
will be satisfactory. To make a square picture out of 7 × 5 neces-
sitates some of the subject being cut away at the sides, or, if re-
duced in the same proportion, the picture on the screen will appear
long and narrow. Therefore, as the screen has a better appearance
when fully covered, it is necessary to bear in mind, while taking the
negative, what is ultimately to appear when used in the lantern. For
lecture purposes it matters very little what shape the pictures are
made; but for a lantern exhibition of photographs much of the effect
depends on uniformity of size. The shape may be square, circular, or
cushion-shaped, and, provided the sheet or screen is filled, the effect
will generally be good. The good effect also depends on the quality
of the pictures, as no system of exhibition shows defects more than
the lantern. It is, therefore, necessary, in preparing lantern-slides, to
keep constantly in view the purpose for which the picture is to be
used. Nothing looks worse than to have a thin and weak picture fol-
lowed by a dark one, or for one to appear as a snow scene when the
true effect should be that of a bright summer's day. A really good
transparency can only be obtained from a negative of the best quality.
It may, however, be possible in some cases to make a fairly good
transparency from a negative which will not give a good paper print ;
the defects may to some extent be modified by careful exposure, deve-
lopment, and intensification.
Good lantern-slides may be made by any of the photographic pro-
cesses capable of yielding pictures on glass. A process which may fail
altogether in some hands will yield excellent results in others. It
may, therefore, seem superfluous to give instructions, and it might
suffice to say: Use the process you know best how to work. Some of
the best lantern-slides were made by Ferrier of Paris. The process, so far
as known to the writer, is still a secret, but is believed to have been
the old albumen process. Good work was done on plates by methods.
now entirely out of use, and it is difficult to say which process now
practised will give the best pictures. Wet collodion will give pictures
of the very highest quality, and if amateurs would take the trouble to
acquire a knowledge of this process, they would probably give it the
preference over all others for making lantern-slides. Carbon tissue
prepared specially for transparencies, and the Woodbury process give
beautiful results. Gelatine plates in some hands are successful, and
now that special attention is given by makers of plates for lantern-
slides in the preparation of plates for this purpose, slides equal to the
wet process can be produced. Gelatino-chloride plates are generally
preferred. With care in developing, very beautiful pictures and
variety of tone may be obtained.
When negatives of the same size as the lantern-slide are available,
they can be printed by contact, and this is the best way; but when
PROCESSES.
127
the negatives are larger, the transparency must be made in the copying
camera. Makeshift appliances may be used, but the best work can
only be done with apparatus specially constructed. (See Copying
Camera.)
Two cameras may be utilised in making lantern-slides: one large
enough to hold the large negative to be reduced, and the other having
the lens and plate-holder; these cameras, when placed on a board,
may be used in the way which placing the two instruments together
will suggest.
Artificial light may be used for making lantern-slides. The source
of light may be one or two gas-flames or oil-lamps; but the light
must be diffused by means of ground glass.
As to the method for developing pictures for the lantern, if gelatine
plates are used, the best advice which can be given is to keep to the
formulæ sent with the plates. If wet collodion plates are used, the
development may be varied by diluting the solution of iron; and the
intensification should be made with pyrogallic acid in the usual way,
great care being taken to watch the intensity. Gold or platinum
toning may be used if desired.
Lantern-slides are sometimes coloured. Whether it is desirable
to attempt to colour a photograph which is to be enlarged many
diameters is entirely a question of taste. The colour should be
applied with skill, or the effect will not be artistic; while nothing
can be worse in a lantern exhibition than a crudely coloured slide.
As a rule, such slides are crude in the extreme. To attempt to
improve a good lantern-slide by the application of colour is, in the
writer's opinion, a mistake, and it should not be attempted except
by those who are skilled in painting.
Leimtype. This process was invented by Professor J. Husnik of
Prague, and is a variation of the photo-etching and collotype pro-
cesses. The printing surface is prepared with sheets of chrome-gelatine,
which are fastened to zinc plates with resin. After developing by
rubbing with a certain fluid, the plate is finished and ready to be
printed from in an ordinary type-press. The only difference between
a Leimtype and a zine block in line or half-tone is that the surface of
the glue or gelatine is used to print from. The process is said to be easy
to manipulate, skilled labour not being required, while 50,000 prints
can be taken from one plate, which, if necessary, can be reproduced
by the galvanic method. The process is patented. The appearance
of a Leimtype print is very much the same as a print from a Meisen-
bach block, and in printing from half-tone blocks the same care will
be required as in the Meisenbach method. A line block in Leimtype
is in every way equal to a zinc-etched block of the best quality.
Litho - Heliogravure. In this process a lithographic stone is
128
MANUAL OF PHOTOGRAPHY.
covered with a very thin coating of asphaltum, composed of 5 parts
of asphaltum, 6 parts of white wax, and 6 parts of stearic acid, to
which, while boiling, 2 parts of soda solution are added. This pre-
paration of asphaltum is dissolved in turpentine. After filtration,
a portion is poured on to the lithographic stone and distributed by
a litho-ink roller, so that a thin film is left on the stone. By means
of the ruling machine, the stone is then ruled with fine lines. It is
then etched with-
Nitric acid
Alcohol
Water
•
O. 10 part.
6 parts.
35
>>
The etching fluid is allowed to remain on the stone for thirty
seconds, and is then washed off. The stone is then dried, oiled, and
the asphaltum washed off with turpentine; after which it is rolled
up with ink and used for transfer of the lines. The lines having
been ruled in one direction, transfers may be made diagonally or in
any other way desired. The picture has next to be transferred. It
is prepared by making a diapositive on carbon tissue. The print is
then wetted with cold water and squeegeed on to the lined stone;
then the paper is moistened with water at about 110° F. and removed
in the usual way. After careful drying, which may occupy five or
six hours, the stone is ready for etching. Ferric chloride is used for
etching the stone, beginning with a strength of 40° Beaumé and
finishing with 30°. The stone may be printed from in one kind
of ink, or ink of various colours can be applied to the parts desired,
and the impression of all taken at the same time.
The process is
the invention of Herr C. Eckstein, and is described by Herr O.
Volkmer, who states that the results are very fine.
Magic Photographs (see Indian-ink Outlines).- When Sir John
Herschel suggested that a photograph could be bleached by saturating
it with mercury chloride, he did not anticipate that his discovery
could have any artistic or commercial value. Reference to the article
Indian-ink Outlines will show that the process has a great practical
application. As "magic photographs" a very pretty result may be
shown. After the photograph, prepared as described on p. 121, has
remained in the bleaching solution a few minutes (until the picture.
has entirely disappeared), it should be thoroughly washed and dried.
If the print is now placed in a solution of sodium thiosulphate, the
photograph will reappear. Blotting-paper may be saturated with the
thiosulphate and dried. If now the dried and bleached print be
placed with the blotting-paper in water, the "magic" picture will
appear.
Meisenbach Process.-Owing probably to the fact that the Meis-

Engraved from a Photograph
BY THE
MEISENBACH IMPROVED PROCESS OF PHOTO-ENGRAVING.
UNIC
OF
FICH
PROCESSES.
129
enbach Company patented a method of producing half-tone blocks
which could be printed with type, the name Meisenbach is often
used to designate any block which shows cross lines on the picture,
although such picture may be produced by means to some extent
different from the process as patented by Meisenbach. The special
method used by the Company is very similar to much of the same kind
of work produced in this country, on the Continent, and especially
in America. One of the earliest of the process blocks was produced
by Pretsch, and was printed in the Photographic Journal, No. 131,
1860. Most excellent work can be produced by breaking up the
half-tone by means of the line screens; but, no matter how perfect
the block may be, there is risk of spoiling by careless printing, as the
very fine lines soon fill up with ink. Unless the block be most
carefully "made ready" and judiciously printed, the effect produced may
be anything but artistic. On the other hand, a good half-tone block
carefully printed on good paper leaves nothing to be desired as to
artistic beauty, as the plates in this volume show very perfectly.
Micro-Photography.--Photographs which require a lens to make.
them visible are called Micro-Photographs. If these minute photo-
graphs are to be used under the microscope and magnified many
diameters, the image must be as free as possible from granulation
and crapiness in the film. Photographs of objects enlarged by means
of the microscope are sometimes called micro-photographs, but the
proper term for such pictures is photo-micrographs, the method of
producing which is described under that heading.
Mosstype. This is a variety of the method of making half-tone
blocks for printing with type.
But prints
Mounting and Mountants.-Too little attention has, from the first
discovery of photography, been given to the best way to mount
photographs. Talbot's method was to attach the prints by their
outer margins only. The importance of this is seen in the prints
made by himself which still exist, and which, in some cases, have
faded only at the parts touched by the mountant.
mounted partially in this way have not the same finished appearance
as those which are completely attached to their mounts. Hence the
importance of using a mountant which shall not have any chemical
effect on the print. The mountants usually employed are starch,
freshly made flour-paste, gelatine, india-rubber dissolved in benzole
or chloroform, and many others. In themselves some of these sub-
stances are quite harmless so long as the prints are kept quite dry;
but damp may set up decomposition, producing acidity and the pro-
bable destruction of the print; this applies to silver prints only,
as they are most liable to be injured by chemical decomposition.
Another difficulty arises in mounting prints with substances such as
I
130
MANUAL OF PHOTOGRAPHY.
starch and gelatine; these hold a large quantity of water, and the
consequent expansion of the paper when moistened by the mountants
produces a contraction on drying which causes the mount to cockle or
to be drawn out of shape; this result is certain to follow except the
mount be of unusual thickness. It is generally believed that pro-
fessional mounters use the best glue. With this material, and by
means of a press, prints may be mounted on paper or thin card-
board without cockling; but the amateur has not the appliances
to effect this. The india-rubber solution answers very well; but,
after a time, decomposition may occur, and the prints will peel off
the mounts. Gum arabic is not recommended, as it will not keep,
and it takes some hours to make. Starch that is not too stiff answers
extremely well; it is very clean; it does not set too quickly,
and is very easily made. The dry starch should be smoothly mixed
with cold water, and then boiling water poured on to it until the
required consistency is attained, stirring while mixing. When cool
it is ready for use, after taking off the skin which forms in cooling,
as this, if mixed with the starch, causes it to be lumpy. Some kinds
of starch require to be boiled. There is one disadvantage with
starch; it is difficult to remove a print from the mount without
injury. Gelatine is a good mounting material; it must be used
warm, and prints can be readily removed from their mounts when
placed in hot water. The gelatine should not be too strong. If it
sets in a thin jelly when cold, it has sufficient consistence for mount-
ing prints. No starch nor gelatine should be used which is at all
acid.
Bleached shellac dissolved in spirits of wine is recommended by
Professor Rood as a mountant. The shellac, which should be rather
thick, is applied to the dry prints, which are then rubbed down in the
usual way, care being taken that the mountant does not touch the face
of the prints. This would appear to be a desirable mountant, as the
prints do not cockle, and the shellac protects the prints from any
injurious matter which may be in the mounts.
When photographs are to be mounted in books or on thick paper,
every care should be taken to keep the paper from cockling; and, if
the prints are attached completely to the paper, india-rubber or the
shellac mountant should be used. With care, prints may be mounted
by using the best glue, touching only about a quarter of an inch of
the print all round, and using a piece of paper half an inch smaller
than the print to protect it while the glue is applied. The prints.
should be carefully trimmed, and, if not flat, they may be placed
on a soft cloth and a thin smooth-edge drawn across the back several
times. This will flatten the prints and make them easy to handle.
Prints should always be trimmed before they are toned, and, if left
PROCESSES.
131
face down while drying or between cloths or blotting-paper, they are
not so liable to curl when dry.
Very little experience will enable any one to place a print correctly
on its mount without any marks as guides. It is sufficient to place
the print while dry on the place where it is to be fixed, and make
pencil-marks at two corners where such marks are required.
Photographs mounted in optical contact with glass have a very
finished appearance. To mount prints in this manner is not difficult.
A solution of good gelatine, not quite so strong as would be necessary
for mounting on cardboard, should be used. Gelatine 60 grains,
water 3 ounces, filtered through muslin while warm, should be poured
into a flat dish. Into this immerse the print face downwards; place the
glass, which must be perfectly clean and free from defects, under the
print, and then carefully withdraw the glass with the print on it.
Squeeze all superfluous gelatine from the print and set aside to dry.
Prints which have been enamelled, or bromide or other prints which
have been dried on a glass surface, must be attached to their mounts
by their outer margins only.
A convenient way of trimming prints is to use a glass of the size the
print is to be, and a sheet of thick glass or zinc as a bed for cutting on.
Obernetter's Etching Process.-In this process a negative is first
converted into a chloride of silver positive, which is then placed in
contact with a copper plate connected with an electric current. The
chloride of silver is decomposed, and the copper is etched in pro-
portion to the quantity of chloride of silver in contact with the
plate. The picture can then be printed by the ordinary method of
copper-plate printing. It is claimed that by this process a printing
plate can be prepared much more expeditiously than by any other.
Opal Glass.-The term opal has been applied to glass which is
flashed on one side with a glass which is opaque white, or which is
composed altogether of the white substance. In the latter case it is
called pot-metal. Both kinds are made in two ways, one having a
polished surface and the other having a ground or matt surface. The
pot-metal kind is altogether to be preferred for photographic purposes,
as it presents a surface on which photographs have a very beautiful
appearance. There are various means by which the picture may be
made on this material. When the wet collodion process is used, a
negative may be copied in the camera, which on development becomes
a positive. The following formula is suitable for the purpose, and
gives a positive of a pearly grey colour :-
Iron protosulphate
Citric acid
Acetic acid
Water
•
30 grains.
90
2 drachms.
15 ounces.
132
MANUAL OF PHOTOGRAPHY.
Or
Iron protosulphate
Citric acid
2 drachms.
6
""
Acetic acid
Water
which will give a blacker tone.
""
3
20 ounces,
The collodio-chloride process may be used for printing on opal
glass, but the gelatino-bromide plates are better for the purpose.
Carbon pictures have an admirable effect when transferred to the
opal.
The pot-metal presents an excellent surface for artistic work, either
in monochrome or water-colour. When well finished, pictures on this
material are almost equal in effect to those on ivory.
Orthochromatic Photography.-The importance of the use of dyes
in rendering colour-values in photography is now generally recognised,
although there is much difference of opinion as to the best method
of using the colours and coloured (yellow) screens. The term ortho-
chromatic, a compound of two Greek words meaning "right colour,"
is considered better than isochromatic, meaning "equal colour," as in
the latter case it might be supposed that the word referred to actual
colour reproduced, which is not the case. The difficulty has always
existed that certain colours could not be represented in the photo-
graph as they appeared to the eye; yellows and reds always translate
darker than they should be, and blues and violets lighter.¹ That
something could be done to make the contrasts in copying oil-paint-
ings less defective than was usually the case was first suggested by
Mr. Crookes in 1858, who, in a leading article in the Photographic
News (Mr. Crookes was then its editor), pointed out that "the collodion
should not be iodised, but bromised with four grains of cadmium
1 Very soon after the discovery of the daguerreotype process, Dr. Draper of New
York found that the film of iodine on the silver plate assumed various colours,
and that these tints were variously acted on by light. The addition of turmeric
to give a yellow colour to collodion was found by Professor J. M. Sanders in 1860
to give additional detail, intensity, and extra-sensitiveness to negatives; but it
does not appear to have been noticed that the addition of colour assisted in the
more correct rendering of the objects copied. It was, however, pointed out by
Mr. Crookes about 1857 that collodion in which ammonium bromide had been
"The
used had advantages not possessed by collodion simply iodised. He says:
chief advantages it seems to possess over the ordinary iodised collodion, besides
its great sensitiveness, are the following:-In a landscape the required opacity of
the more strongly illuminated parts (the sky, for instance) is not lost by over-
exposure; vegetation is also more easily copied. Its superior sensitiveness to
light colour is, however, most strikingly shown when coloured glass or sulphate of
quinine (as suggested by Sir John Herschel) is employed to absorb the strongly
invisible rays.
rays. To prove
To prove this I arranged several flowers and plants with a view
to obtain great contrast of colour, light, and shade."
PROCESSES.
133
years.
bromide to an ounce of collodion; and the lens, which must have a
sheet of yellow glass close in front of it, should be a portrait combination.
working with full aperture, as the time of exposure to the feeble rays
which alone can filter through the yellow glass will be enormous, even
when a picture is illuminated as perfectly as possible." The difficulty
as to the "enormous" length of exposure no longer exists; but the
value of the suggestion is seen in the fact that the yellow screen is
now used in connection with plates which have been chemically
treated to make them sensitive to certain of the coloured rays of the
spectrum. Dr. H. W. Vogel of Berlin was the first to suggest the
use of dyes in 1873. In a communication to the writer, dated Berlin,
6th June 1890, Dr. Vogel says: "Colour-sensitive or orthochromatic
photography is already an old thing, invented seventeen years ago, but
only estimated by the photographic fraternity during the last seven
There are, however, a great many people interested in photo-
graphy who know nothing at all about orthochromatic photography, who
don't even believe in it; others have heard about it, but remain sceptical.
Only in Germany, where colour-sensitive photography was invented,
is it duly appreciated. In the establishments of Braun (Dornach),
Albert & Naunfstängl, Obernetter, Bruckmann (Munich), the Pho-
tographische Gesellschaft (Berlin), are many thousands of subjects
reproduced by colour-sensitive collodion, and in the British Museum
such plates have been used. Colour-sensitive gelatine plates are
already made in at least six manufactories in Germany, one in Eng-
land, and one in America. In using these plates, a yellow screen is
required to diminish the action of the blue rays; but there is one kind
of plate by which the right colour effect is produced without the
yellow screen in taking landscapes; this is the eoside of silver plate.
Who invented orthochromatic photography? One says Ives, another
says Waterhouse, another Tailfer, my name also is mentioned in the
second or fourth order. Dr. Eder says in the Report of the Vienna
Academy, vol. xciv., 1886, p. 380: By the discovery of the action
of colouring matters or sensitisers for the less refrangible rays by
Dr. H. W. Vogel, the means are obtained to make bromide of silver
sensitive for green, yellow, and red by suitable colouring matters.'
Further, Dr. Eder says in the Photographic Times, 1886, p. 483-
'Dr. H. W. Vogel discovered in 1873 the property of many colouring
matters to increase the colour-sensitiveness of the bromide of silver of
those rays of the spectrum which they absorb,' &c. I could cite here
also the astronomer Dr. Nasselberg of Pulkowa, and Dr. Becquerel
of Paris, who is mentioned now in French papers as the first in
order of the discoverers of colour-sensitive photography, but who has
mentioned myself as his predecessor in his publication (Comptes
Rendus, July 1874). In fact, I published my first observations on the
(
134
MANUAL OF PHOTOGRAPHY.
matter of making bromide of silver sensitive for the so-called non-
actinic rays in 1873. (Berichte der deutschen chemische Gesellschaft,
1873, p. 1305; Photographische Mittheilungen, 1873, vol. ix. p. 236).
I made my first experiments with the sun's spectrum, but I went a step
further in employing the newly discovered fact practically. I fastened
a dark-blue silk ribbon on a piece of yellow silk, and took a picture
from it with an ordinary wet collodion plate. The result was a white
ribbon on a dark piece of silk. It was obvious that I could not suc-
ceed much better with a corallin-dyed bromide of silver plate, because
the action of the yellow in the spectrum on it was much stronger than
that of the blue. Therefore I interposed a yellow screen between the
subject and the lens, depressing the intensity of the blue rays; and
now I got indeed a negative which was a true positive print, wherein
the dark blue ribbon was dark and the yellow silk was light. This
was published in the paper named in 1873. It is seen from this that
I succeeded in taking the first so-called isochromatic picture; and
therefore the claim that Mr. Ives was the first is incorrect, as his
results came four years after mine. I am not astonished at mistakes
of this kind, for we have an instance here in Germany where the
Senate of a University has elected a gentleman as 'honorary doctor'
for an invention which he had not made at all.
66
I called the dyes which absorb red or green or yellow rays of the
spectrum and make bromide of silver sensitive for those rays, optical
sensitisers. As such sensitisers I recognised corallin, aldehyde green,
magdala red, cyanin, and fuchsine. In 1876 Waterhouse recognised
eosine as a first-rate sensitiser. In 1875 Becquerel used chlorophyll.
In 1878 Ives tried the same with success. Ducos du Hauron's
brother continued to work with eosine in collodion. In 1883 Tailfer
used the same dye in gelatine plates. In 1884 I introduced azaline,
a combination of cyanin and chinolin red, as a good sensitiser for
gelatine plates. All these sensitisers require a yellow screen for
taking pictures in the right value (yellow bright, blue dark). In 1885
I observed with Obernetter that the chemical combination between
eosine and silver (eoside of silver gives the best results for yellow
and green) gave plates ten times more rapidly for the yellow of the
sun's spectrum than for the blue. With such plates it is possible to
take green landscapes without any yellow screen with far better effects
than with ordinary plates. For bringing out the clouds and misty
distance and foliage, the eoside of silver plate is really superior to the
ordinary kind."
In 1879 Mr. F. E. Ives suggested the use of chlorophyll of blue
myrtle or periwinkle leaves for making collodio-bromide plates colour-
sensitive. The chlorophyll is prepared by steeping the leaves when
cut into small pieces in pure alcohol and heating for a few minutes.
PROCESSES.
135
The solution of chlorophyll is in its best state when fresh, but will
keep for some weeks in a cool place, if not exposed to light. To
prepare the plates, flow with collodio-bromide emulsion, and when set
cover for a few seconds with the chlorophyll solution, after which
wash in distilled water until smooth. The plates must be used with
the yellow screen, which Mr. Ives prepares by making a tank with
plate-glass sides which is filled with a solution of potassium bichro-
mate; the strength of the yellow solution may be increased or dimi-
nished according to the subject to be copied. Excellent results have
been obtained by this method.
Many kinds, of colouring matter have been used for making plates
colour-sensitive, amongst them eosine, erythroșine, cyanine, fuchsine,
azaline, aurantia, rose Bengal, quinoline red, chlorophyll, xantho-
phyll, gallocyanin (a blue dye), chrysanaline, corallin, aldehyde
green. Most of these are derived from coal-tar distillation.
Since Dr. Vogel first suggested the use of dyes, many names occur
connected with the subject of orthochromatic photography in addition
to those already mentioned, amongst them Eder, Becquerel, Ducos du
Hauron, Abney, Bothamley, Drs. Mallmann and Scolic, Hyslop,
Wellington, Obernetter, Waterhouse, Carey Lea, and many others.
In 1883 a patent was granted to Messrs. Tailfer and Clayton for
the preparation of gelatine plates with eosine and ammonia, one of
the special points claimed being the use of ammonia.
From all the evidence available it does not appear that any one of
the substances hitherto used is, in itself, sufficient to render plates
colour-sensitive to all the rays, and that no single one is altogether
satisfactory for the red. Yellow is well under control, as plates may
colour, so that it may have the same value
be over-sensitive for that
in a copy as blue or violet.
As to the best method of preparing colour-sensitive plates, the fol-
lowing is Mr. B. J. Edwards' opinion :-" Since the publication of
Tailfer and Clayton's specification many formulæ have been published
for preparing isochromatic plates by bathing ordinary gelatine plates
with an ammoniacal solution of eosine or erythrosine. This method,
although it is described in the specification as an alternative process,
does not give the best results; also it is found that plates so prepared
will not keep, but commence to deteriorate from the moment of their
preparation. The only practical way of making perfect isochromatic
plates is to coat them with a prepared emulsion which is made iso-
chromatic or colour-sensitive in the first instance. Plates made in
this way are more perfectly colour-sensitive and will work without
the yellow screen; they will also keep without deterioration equally
as well as ordinary plates."
As to whether it is better to mix the dye with the emulsion at the
136
MANUAL OF PHOTOGRAPHY.
time of preparing the gelatine plate, or merely to bathe a plate (which
is already dry) and then allow it to dry again in the dark, there is a
very wide difference of opinion. As Mr. Ives, writing in 1888, said:
"By this method" (using erythrosine or cyanin) "some of the most
rapid ordinary plates in the market can be made as sensitive to the
orange red, orange yellow, and green of the prismatic spectrum as they
are originally to blue and violet. . . . The sensitisers are dissolved in
alcohol, a quarter grain to the ounce, and the plates are prepared by
simply flowing with the alcoholic solution, drying, and then waiting."
Mr. Ives recommends the use of the yellow screen, and he says that
plates prepared in this manner keep well, but that if they are to be
used dry, they should be coated with a thin film of gelatine. If it
be taken for granted, as Mr. Edwards says, that plates prepared with
the original emulsion keep well, and when only dipped do not keep
(although Mr. Ives finds that there is no difference), there can be
no doubt that there is some advantage in being able to make an
ordinary gelatine dry plate orthochromatic by merely pouring over it
an alcoholic solution of the dye.
On the keeping qualities of plates which have merely been steeped
in the colour-sensitising solution, Lieutenant-Colonel Waterhouse says
that he has developed plates which have been laid aside for two
months, and were quite free from defects.
In preparing orthochromatic dry plates, Dr. J. M. Eder recom-
mends the following method:-"Ordinary gelatino-bromide plates are
immersed in the following bath :—
Erythrosine solution, I part in 500
Ammonia
Water
•
I to 2 parts.
part.
100 parts.
When properly prepared orthochromatic plates are not available,
the use of a yellow screen alone will be found of some advantage in
copying objects or paintings in which yellow occurs; also, when there
is much blue in a picture, the yellow screen may be employed.
It has been found that clouds may be photographed with good
effect when orthochromatic plates are used.
The use of the yellow screen is generally advocated by those who
have investigated the advantages of orthochromatic plates, and many
different suggestions have been made as to the kind of screen re-
quired. All admit that glass ground so as to be optically true is better
than any other medium; but such glass is expensive and difficult to
obtain. The plan used by Mr. Ives has already been described. The
surfaces of ordinary patent plate-glass are not sufficiently true, but the
very thin glass used for covering microscopic objects may be coated
with a yellow dye and attached to the diaphragm to be used between
PROCESSES.
137
the lenses. Collodion may be stained with tincture of iodine and
dried on a sheet of glass which has been rubbed over with French
chalk so as to strip easily. To make the film sufficiently thick to
handle, the collodion may be applied as frequently as necessary.
When quite dry, the film may be removed from the glass and care-
fully placed over the aperture of the diaphragm. Gelatine may be
obtained and used in the diaphragm slot, or the back of the lens
nearest to the plate may be coated with the yellow dye; this, how-
ever, is a troublesome makeshift, and cannot be recommended. When
the glass screen is to be used, it may be placed either within the lens
mount in front or at the back of the combination. Shades of varying
density should be available, as a darker tint may be necessary in cer-
tain cases.
The time which has elapsed since the subject of orthochromatic
photography first received recognition is too short to permit any
definite theory to be formed as to whether the results are due to
physical or chemical causes. Experiments by Abney have shown.
that the gelatine film itself need not be dyed, but that if protected by
a varnish containing the colouring matter, the same results may be
obtained as when the gelatine emulsion itself is dyed. This would
seem to favour the physical theory. "There are other considerations
which tell in favour of the chemical hypothesis, such, for instance, as
the fact that the addition of ammonia increases the special sensitising
action of the dyes; but some of the experiments described by Abney
appear to me to prove most conclusively that it is in this direction
that we must look for the explanation of this phenomenon.” 1
Meldola says further, "Before taking leave of this part of the
subject, I am tempted to offer a suggestion which may be of use in
guiding future experiments. The chemical hypothesis of orthochro-
matic action rests upon the fact that the best special sensitisers are
the most fugitive dyes. Now there is reason for believing that the
bleaching of a colouring matter by the action of light is due to photo-
chemical oxidation. If this be the case, atmospheric oxygen may be
essential for the production of orthochromatic effect, and the formation
of a second maximum in the less refrangible part of the spectrum
might be prevented by immersing the dyed plate in a reducing solu-
tion, or in some inert liquid or gas which prevented access of air.
Experiments of this kind might easily be made, and if the action on
the green, yellow, or orange did not take place under these circum-
stances, the chemical hypothesis of orthochromatic photography would
be raised to the rank of a proved theory; while, on the other hand,
if the second maximum still appeared, this hypothesis would not
be disproved, because it is possible that the breaking down of the
1 Meldola, Chemistry of Photography, p. 317.
i
138
MANUAL OF PHOTOGRAPHY.
complex molecule of the colouring matter by the action of light
might take place in the absence of oxygen, and thus also give rise to
the formation of products of a reducing character.”1
Colour-sensitive plates may be developed by any of the ordinary
methods, but the following is recommended for the plates prepared
under the Tailfer patent by Mr. Edwards. The plates should be
carefully protected from all light, except that of a ruby colour; and
the exposure necessary in the camera is less than for plates of the
ordinary kind :—
Pyrogallic acid
No. 1 Solution.
I ounce.
Alcohol (methylated)
Glycerine
7 ounces.
ounce.
Mix the glycerine and spirit and add the pyrogallic acid. The
following is another formula :-
Pyrogallic acid
Citric acid
Water
I ounce.
40 grains.
7 ounces.
No. 2 Solution.
Potassium bromide.
•
Distilled water
60 grains.
7 ounces.
Ammonia, 880
I ounce.
If kept separate and well corked, these solutions will not deteriorate
for some weeks. To use, take one part of No. 1 to fifteen parts of
water, and the same proportion of No. 2. These dilute solutions
should be mixed in quantity as required; and as much as will cover
the plate to be developed may be poured from the bottles into a
measure and poured over the plate, taking care to avoid air-bubbles.
Fix with sodium thiosulphate as usual, and clear with-
Alum
Sulphuric acid
Iron protosulphate
Water
I ounce.
$
3 ounces.
20
There would seem to be very little reason why commercial plates
prepared for orthochromatic work should be more expensive than the
ordinary kinds, as no extra labour in their preparation is incurred.
When the time arrives that the distinction in price is removed, it will
probably be found that orthochromatic plates will be used for all
purposes, as the presence of the dye is no disadvantage; and, in very
many cases, the photographic result is much superior to that of work
which has been produced on an ordinary plate.
Panoramic Photography.-Views embracing an angle greater than
any ordinary lens can give may be taken by carefully levelling the
camera, and then, after taking the first plate, revolving the camera
1 Meldola, Chemistry of Photography, p. 320.

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(Copyright.)

PRINTED BY JAMES C. NORBURY & SONS,
MANCHESTER.
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In this way
The
so that the next view will slightly overlap the first one.
a series of pictures may be taken embracing the entire circle.
disadvantage of this method is that the exposures, and also the
development of the negatives, must be identical, in order that the
prints when joined may be alike; the printing, also, requires equal
care. A camera was invented by the late Mr. Sawyer by which the
picture was taken through a narrow slit, the proper motions being
given to the lens and plate by means of clockwork.
A very wide angle of view may be obtained by means of a specially
constructed lens, such as the panoramic lens patented by the late
Mr. Sutton. A sphere of flint-glass was filled with water, and in
the centre was fixed a small diaphragm. It was necessary to use
a curved glass plate when the collodion process was employed, the
manipulation of which was somewhat difficult.
A camera was invented by Mr. Ross of New York having a lens
of 3-inch focus, by which a plate of 8 inches by 3 was covered, the
angle of view included being 120 degrees. The instrument was
called the scioptic camera. A fuller description will be found in the
Liverpool and Manchester Photographic Journal for March 1857.
Paper Negatives. Now that celluloid films are available, it is
scarcely probable that paper will ever again be used for negatives,
unless some means can be found for entirely removing the granularity
of the paper. Although glass superseded paper in the early days of
the photographic art, very beautiful work was done on paper negatives,
and the existence at the present time of many of the earliest nega-
tives (which it will be remembered were developed with gallic acid
and aceto-nitrate of silver) proves that they were permanent.
Pedestal Portraits.-The effects of statuary busts may be simu-
lated by photographing a portrait, with the bust suitably draped,
against a black velvet or other very dark background, while powder
must be freely used on the hair and face to assist the effect.
By the
aid of double printing the pedestal can be introduced. When care-
fully arranged, the effect is excellent.
Photochromes.-Many methods have been proposed for treating
photographs with colour, so as to get rid of the monochrome effect,
and the name of M. Leon Vidal is associated with a process called
Photochrome. Under the heading Photography and Colour this
subject is treated in full.
Photochromo-Lithography. One of the most useful applications.
of photography is in making transfers for lithographs of designs which
have been printed in colours. Each colour is printed from a different
stone, and as reduced or enlarged copies are often required from such
work, the different sizes may be obtained by photographic means, thus
saving the cost of re-drawing. Impressions from each stone are taken
140
MANUAL OF PHOTOGRAPHY.
in black, and from these transfers can be made. The accompanying
plate shows the original design printed in eleven colours; the reduced
copy was made in the way indicated.
Photo-Engraving-Photogravure.-Under various names processes
have been invented, often patented, for the purpose of producing on
a copper, steel, or zinc plate a picture or photograph having half-tone.
Dating almost from the invention of photography, attempts were made
to enable impressions to be taken from the daguerreotype plate. Some
of this early work was almost equal in quality to the productions of
the present day. The failure of commercial success was probably due
to the soft character of the metal, as very few good impressions could
be taken, a defect which is remedied now by the process of steel-
facing, by which the engraved surface of the plate is protected by
a hard metal renewable at pleasure.
The discovery that an image can be produced by the effect of light in
the camera on bitumen is due to Nicéphore Niépce, who, in 1829, coated
plates of pewter and copper having a surface of silver with bitumen
(glass was also tried) dissolved in oil of lavender (which was also used
as a solvent to develop the picture); the parts acted on by light,
being insoluble, remained on the plate, thereby protecting the metal
from the acid used to etch the image. Specimens of Niépce's process
were exhibited by Mr. Malone at a lecture delivered by him at the
Royal Institution, London, in 1857; they were presented to a Mr.
Bauer, who resided at Kew at the time of the visit of Niépce to
England. If these pictures are still in existence, it seems desirable
that they should be available for inspection in some public institution.
The perfect work now practicable is done mainly by a process almost
identical with that invented by Niépce. Many names are connected
with the process for obtaining pictures on metal plates; amongst
them Talbot, Pretsch, Claudet, Poitevin, Fizeau, Grove (who used
the galvanic method), and many others. The next step was the
introduction in 1852 by Talbot of a process he named Photoglyphy.¹
In this, gelatine made sensitive to light by potassium bichromate
takes the place of bitumen. It has the advantage of printing quicker,
and for line-work is better than the older process, but for half-tone it
is inferior. In 1854 Herr Paul Pretsch of Vienna patented a process
which he called Photogalvanography. A jelly formed of one part of
gelatine to ten of water was mixed with a strong solution of potassium
bichromate.
A
To this was added gelatine containing silver nitrate.
third portion of gelatine containing a small quantity of potassium
iodide was added. After being well mixed and strained, glass plates
1 The full specification of Talbot's patented process of Photoglyphic Engraving
will be found in the Liverpool and Manchester Photographic Journal, vol. ii.
p. 269.

Estampe Miniature No27
En Penitence
Poussed Calaton & C Editours
Paint par Z. Perrault
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were coated with the emulsion and dried; when dry, the plates were
exposed under a negative. Up to this point the processes of Talbot
and Pretsch are very similar; but the after treatment is quite different.
The plates after exposure to light were not washed, but were placed
in water to allow the gelatine to swell in those parts not acted on by
light, the picture appearing in relief. At this point the gelatine could
be printed from if the surface would bear pressure; but as it would
crush, a mould was taken and the surface of this mould was electro-
typed. This electrotype was used as a matrix, and from it blocks.
for printing with type were made. By a variation in the method
plates for printing in the copper-plate press were produced. In order
to obtain a granular or stippled surface necessary to produce the effect
of half-tone, advantage was taken of the peculiarity which gelatine
combined with potassium bichromate has of drying with a grain.
This grain breaks up the shadows and gives the effect of half-tone.
The same effect is produced and taken advantage of in (and indeed
is the foundation of) the collotype process.
The plate facing page 143 is an example of Pretsch's process,
and will compare favourably with work recently done.
Plates exe-
cuted in any process producing half-tone effects are more or less
worked upon by the engraver. As an example of half-tone process
engraving, it is remarkably good. The illustration is by Messrs.
A. & C. Dawson.
Improvements in the preparation of plates for intaglio-printing
were slowly made; but there was no great advance upon Pretsch's
method until the late Mr. Walter B. Woodbury took the matter in hand.
In 1874 he wrote: 1 "Of all the photo-mechanical processes, perhaps
photo-engraving has made the least progress during the past few
years; simply owing, I imagine, to the fact that engraving, or rather
the printing from engraved plates, is, and must always be, a slow and
expensive process." Mr. Woodbury then says that excellent results
have been produced by M. Rousselon, of the firm of Goupil & Co.
of Paris, by the method suggested by Mr. Woodbury to them; and he
claims that the excellent work done by Rousselon is based on the
idea he suggested to Goupil & Co. As was the case with many other
ideas suggested by Mr. Woodbury, great results have followed, and we
see them in the extremely beautiful works executed by Goupil & Co.
and their successors, Boussod, Valadon, & Co., called photogravure.
The plates are made by the process of electro-deposition of copper; but
whether Woodbury's method is still followed, or any modification of
it, is not known to the writer. The plates, while being very perfect.
reproductions of the originals, in some cases owe much of their excel-
lence to the very skilful retouching by the engraver; and the printing.
1 British Journal Almanack, 1874, p. 106.
142
MANUAL OF PHOTOGRAPHY.
qualities of the plate are often due to the same cause. It should be
stated, however, that some of the best work in photogravure is quite
untouched. The preparation of the plate by this method—that is,
from an intaglio-requires from one to three months. The plates are
steel-faced, and the steel surface is renewed after each thousand
impressions have been printed.
One of the chief difficulties with plates in half-tone is that the etch-
ing cannot be carried very deep, thus involving very careful printing.
The term "photogravure" was first applied to this process by Goupil
& Co., and is sometimes called Goupilgravure. The plate facing
page 140 is an example of the excellent work done by the Company.
The process known as "Klic's process" produces effects almost
exactly similar to those done by what is called "Goupil's process."
Messrs. Annan of Glasgow at one time worked this process, and it is
now used by Messrs. Annan & Swan of London, who produce work very
closely resembling the Goupil productions, and certainly not inferior.
*
The working details of Klic's method are printed in the Photo-
graphic News for 28th January 1887. It varies from Talbot's process
merely in the use of powdered asphalt. The copper-plate must be
absolutely clean, the polish being effected with whitening in water.
The plate must now be covered with the asphalt, which is most simply
done by shaking the powder in a box. When the larger particles
have settled, the plate must be introduced at the bottom, an opening
being made at one side of the bottom so that the plate may be placed
without disturbing the dust floating in the upper part of the box.
The fineness of the grain depends on the time the plate remains in
the box, as the more dust collected the finer will be the grain. When
it is judged that the plate is sufficiently dusted, it is removed from
the box, and, by the heat from a Bunsen burner, the asphalt is par-
tially melted, until the dull surface is changed to a gloss, when the heat
must be at once removed. A reversed positive being now required, a
piece of carbon tissue is exposed under it, and squeegeed on to the
copper. When printed, the picture is developed in the usual way.
The etching is effected with iron perchloride, a strong solution being
first used, as its action is less energetic than a weak solution. The
plate is treated with the iron in three or four degrees of strength. A
strip of copper placed in the iron solution until the colour changes
causes the solution to act evenly. The etching takes place through
the gelatine, and the plate is protected by the asphalt. When the
etching is complete, the gelatine can be removed with caustic alkali
and the asphalt with turpentine. Experience alone will show when
the etching is complete, and its progress can be watched through the
film. The temperature of the iron etching fluids should be 70° Fahr.
Plates by this method may be prepared in a few days.

UN
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A Dawson, Delt
Clewer Churchyard
by the "Pretsch Process.
A&CDawson Ph.Sc
PROCESSES.
143
Many other processes or modifications have been introduced; the
names of Obernetter, Waterhouse, Zuccato, and Sawyer may be men-
tioned. Similar processes under various names are used in America.
The appearance of the finished work is very much the same, and all
are probably variations of the processes described here.
The Frontispiece is a very perfect illustration of the photogravure
method.
The perfect success in the production of process blocks depends on
technical details. None of the patented methods are published with
sufficient description to permit the working of any one of them satis-
factorily without the knowledge which is kept secret.
Half-Tone Zinc Etching.-Generally the half-tone block process
may be said to be practised as under:-A copper or steel plate is
ruled or engraved with lines, from 100 to 130 to the inch, running
in one direction diagonally across the plate or crossing at right
angles, also diagonally. The plate may be of any proportion;
but, as negatives of various sizes have to be made, the plate
should not be less than 16 inches square. From this plate a
perfect impression must be made on the best paper, mounted and
carefully preserved. Very perfect line-screens or plates may be pro-
duced by ruling a glass plate through an etching-ground of wax,
and acting on the glass with hydrofluoric acid. Printing-ink can
then be rubbed into the lines, producing a very perfect screen
with black lines on clear glass. A copy must now be made from
the lined sheet of the size required for the half-tone block, and
the negative must be placed in the dark slide of the camera in front
of the prepared plate, separated from the film, at a suitable distance
to produce the dotted effect required to break up the half-tone of
the subject. As the light passing from the object to be copied must
pass through the screen to the sensitive plate, the result is that the
negative is covered with the lines of the screen, and the half-tones
are so broken up that a block can be obtained, which, with careful
printing, gives a very satisfactory copy of the original. The line-
screen need not be in actual contact with the sensitive film, as the
light passes through in direct lines and a sharp copy is transmitted.
Much mystery has been made as to shifting the screen-negative; but,
beyond the necessity for reversing the negative when a sheet ruled in
one way only has been used, it is difficult to see how any other kind
of shifting can be necessary. Of course, when the negative with
lines in one direction only is used in front of the sensitive plate, while
the copy is being made some method must be adopted so as not to
disturb the plate while the line-screen is shifted.
When the line-negative is varnished (and the greatest care must
be taken in every step of the process, so as to produce a perfect
144
MANUAL OF PHOTOGRAPHY.
result, for there must be no spots or blemishes of any kind on the
negative), the printing on the zinc or copper may be proceeded with.
For very fine work it is preferable to use the bitumen method (see
Bitumen Process). The preparation of the metal plates with albumen
and the other processes required to complete the block are described
under Zinc-Etching.
In some cases the zinc blocks are worked up during the etching
process to improve the effect by stopping out parts requiring higher
light; but this has to be done with much care and skill, otherwise
the work will be patchy and unsatisfactory.
Photo-Filigrane.-One of the numerous applications of photography
due to the inventive genius of the late Mr. Woodbury was called by
him Photo-filigrane, and was made the subject of a patent. The
object of the process is to impress an image on paper, so that, when
viewed by transmitted light, some of the effects of light and shade
are produced. This is effected by attaching to a metal roller a gela-
tine relief, so that when sheets of paper are passed between the relief
and another roller, the impression is taken by the paper, producing an
effect similar to a water-mark, but with half-tone in place of mere lines.
Photo-Galvanography.-This name was given to the process in-
vented by M. Pretsch. It is referred to under the heading Photo-
Engraving.
Photochromo-Typography.-One of the most beautiful methods for
the application of colour to the half-tone zinc process is shown in the
illustration by Messrs. Boussod, Valadon, & Co., on the opposite page,
in which it will be seen that, after the original block for the black is
printed, by a process of printing from blocks for the colours a very
effective picture is produced.
The
Photogenic Drawing. In this process fine writing-paper or white
leather was brushed over with, or was steeped in, a solution of sodium
chloride (or common table-salt). This was allowed to dry, and was
then washed over with, or floated upon, a solution of silver nitrate.
When dry, the object to be photographed was placed on the paper
and then exposed to sunlight, perfect contact being made by pressure
under glass. Talbot found that when paper was prepared so that
there was an excess of silver nitrate, he obtained better results.
picture was of course negative—that is, if the object to be copied was
an engraving, the black lines would be white in the copy. The fixing
was a difficulty which Wedgwood and Davy could not overcome; but
Talbot found that by washing the prints, so as to free the paper from
the silver salt as much as possible, and then steeping the prints in a
solution of salt or potassium iodide, the prints were, to a certain
extent, fixed, and that the action of light on them was so far lessened
that the negatives could be used for producing copies having the

Chromotypogravure & Imprimerie Boussod, Valadon & Co. Paris.
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natural light and shade.
PROCESSES.
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Paper prepared in the manner described is
very sensitive to direct daylight, or when used with the solar micro-
scope; but, if used in the camera, a very long exposure was necessary;
yet Talbot succeeded, as already stated, as early as 1835, in producing
pictures in the camera by this process, which he named Photogenic
Drawing.
Photographing on Wood.-The blocks of boxwood used by wood-
engravers have to be carefully seasoned in order to prevent the possi-
bility of splitting after the surface has been engraved, hence the
difficulty of utilising photography; but it has been found that a well-
seasoned piece of wood, after it has been wetted, is soon in a fit state
to be engraved. Any kind of brittle film on the surface of the wood
FIG. 36.
is liable to chip under the graving tool; therefore, when a film is used,
it must be of the thinnest possible kind. A collodion positive
loosened from the glass with nitric acid, floated on water, and then
caught on the wood block in the reversed position, is found to answer.
The surface of the wood being blackened, the image is perfectly dis-
tinct and the film is too thin to cause chipping. Many other methods
have been proposed.
One of the earliest engraved blocks produced with the assistance
of photography was the work of Mr. Robert Langton of Manchester,
to whom the writer is indebted for the permission to use the block
(Fig. 36). The engraving was printed in the Art Journal of August
1854, and is an excellent example of this kind of work.
K
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MANUAL OF PHOTOGRAPHY.
Photography and Colour.-In these days of enlightened chemi-
cal research, the pursuit of the discovery of the philosopher's stone
(which, it is almost necessary to explain to the junior readers of these
pages, was the desire to find some means of converting the baser
metals into gold) is never heard of; but the pursuit of photography
in colour has almost taken the place of the older chimera;—it is a
kind of ignis fatuus-something which is visible, but which eludes
the grasp. To say that the object sought is unattainable would be
unwise, seeing that little more than fifty years ago the thing we have
now in such wonderful perfection was something dreamed of, was
sought for, and was found. But this image of the camera, the mar-
vellous beauty of which set the mind of Talbot reflecting on the
possibility of its being fixed on his drawing-paper, is a very different
thing, as it was first fixed by Talbot and Daguerre, to the matter
which they would have preferred, the picture with all its charm of
colour. This is the problem which has baffled the efforts of all who
have attempted to solve it. Let us inquire what has been done.
towards the fulfilment of the desire, so that we may possibly be in
a position to ask whether, judging from the little produced by over
fifty years of experiment, how much more may be anticipated in
another half century.
As early as the first year of the present century, Ritter, Berard,
Seebeck, Berthollet, Herschel, Sir H. Englefield, and others had inves-
tigated the calorific and colorific effects of the sun's rays; and about
the same time it was discovered that the chemical were different from
the actinic rays of light. Wedgwood and Davy used the chemical
rays to produce their images on paper and leather, but they do not
appear to have observed any effect of colour on the surfaces made
sensitive to light; they used coloured glasses, and noticed that when
light passed through red glass very little change was produced, but
through yellow and green the change increased, and when blue and
violet glasses were used more active changes occurred-that is, their
leather and paper darkened quicker. They speak of the changes of
colour, but it is evident that they mean only the difference in tint
caused by the light. One of the earliest investigators of the effects
of light in producing colour on silver chloride was Dr. Seebeck of
Jena, who, in 1810, found that when silver chloride was spread upon
paper and exposed while wet to the solar rays, received on a prism
through a narrow aperture in a shutter, changed colour; in the blue
it became blue, and in the red rays it changed to rose colour, and
there were other changes in the various tints. This appears to have
been an experiment to show the chemical change produced in sun-
light, not in the nature of a photograph; and it is chiefly interesting
as showing that nearly thirty years before Talbot's discovery it was
PROCESSES.
147
known that one of the properties of light was to produce a change
on silver chloride corresponding with the colour of the light which
had been caused to fall upon it.
A few months after Talbot's discovery, Sir J. Herschel published
some experiments which show that when a bright spectrum was
thrown on a piece of sensitive paper the change effected was not that
of darkening only, but colours were produced. Herschel's experi-
ments were continued; and, although he failed to discover any means
of fixing the colours, he found that when washed in water some
degree of permanence was given; he also found that the colours
deepened when the paper had been kept for some days in the dark
(one of the effects in the continuing action of light, which is noticed
in carbon printing and in prints on paper prepared with gelatine and
potassium bichromate). Herschel's experiments led him to think that
it might be possible to produce pictures by the aid of light in natural
colours.
About the same time (1840), Hunt published observations on the
effects of light passing through pieces of coloured glass on to paper
prepared with silver nitrate combined with salts of different kinds;
but no advance was made in the direction of the production of photo-
graphs in the colours of Nature.
It is unnecessary to follow the researches step by step, as each
experimenter seems to have advanced very little beyond what his
predecessors had done. The experiments were varied by Becquerel,
who, after confirming what had been done by Herschel and Hunt,
showed that a silvered plate which had been coated with silver
chloride, produced in various ways, was sensitive to the yellow as
well as to the other colours. He found also that after prolonged
exposure to the spectrum the first effects disappeared and the plate
became grey. Becquerel next prepared silver plates with chlorine
electrically produced. The preparation of the plates was a very
tedious and troublesome matter. To obtain the best effects, a
kind of annealing process had to be gone through, the ultimate
result being something like what had been previously done. From
the description of the appearance of these coloured impressions of
the spectrum, it is difficult to imagine what they were like or what
was the intensity of the colours produced. One is almost tempted to
ask whether some of the effects may not have been due to iridescence.
The name of Niépce de St. Victor is often mentioned in connection
with photography in natural colours; but he does not appear to have
made any original discoveries, nor to have done more than repeat
Becquerel's experiments. Many other names occur in connection with
this subject, but so far no advance has been made towards what is so
eagerly desired, and what has repeatedly been announced - photo-
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MANUAL OF PHOTOGRAPHY.
graphy in the colours of Nature. Coloured photographs have been
produced, but the colours have not been impressed on the paper by
the agency of light. Light and chemistry have produced the picture,
but the colours have been put in by hand in various ways; generally
by first making the picture transparent, and then, on the back, distri-
buting the colour roughly to produce the desired effect. Things of
this kind are of no artistic value, and cannot deceive the eye of the
skilled artist or photographer.
By accident curious effects are sometimes produced. In the Liver-
pool and Manchester Journal of 15th April 1857 it is reported that
at a meeting of the Manchester Photographic Society on the 8th April
the late Mr. Joseph Sidebotham made a communication on this sub-
ject. He said: "In the ordinary collodion positives on glass we
occasionally meet with examples of partial natural colouring, such,
for instance, as a green tinge on the foliage. I have had one where
the green and red in a photograph of some scarlet geraniums were
tolerably bright, and I have here on the table a landscape with trees
and a red brick house, taken in bright sunshine, and you will see the
green foliage and the red house are tolerably well marked in colour."
The picture showing these colours was taken in 1852. The writer saw
the picture at the time it was shown by Mr. Sidebotham, and again
in 1887, when it was lent for the historical collection in the photo-
graphic section of the Exhibition at Old Trafford, Manchester, in that
year. There had been no change that could be detected in the thirty-
five years since it was taken; and, although the appearance of colour in
this case was the result of accident, all attempts to reproduce them
having failed, the picture remains as evidence of the production of
colour under certain conditions of light and chemicals. The difference
between this curiosity, the result of Mr. Sidebotham's experiments in
1852, and all that has been done in producing colours by the aid of
light on chemically prepared plates, appears to be that in the one case
the colours which could not be reproduced remain permanent, while in
the other the colours which can be obtained under certain conditions
are fleeting and cannot be fixed.
Many names could be mentioned of those who have repeated the
early experiments for producing the colours of Nature in a photograph ;
amongst them Poitevin, Ducos du Hauron, Vidal, and Carey Lea. Re-
cently M. Verescz has produced some results which are claimed to
surpass everything previously done, especially as regards the fixing of
the colours. The writer is not aware that the method by which these
results have been obtained has been made public. Professor Vogel has
published his opinion to the effect that no advance has been made,
the results not being superior to those obtained by Becquerel. Pro-
fessor Vogel says in a communication to the Bulletin: "If I compare
PROCESSES.
149
The
the sample before me with the pictures I have seen in 1867 of Niépce
de St. Victor, Becquerel, and Dr. Zenker, I must confess that those
much older productions were richer in colour, although the tones
deviated likewise considerably from the natural ones. An essential
progress I can, therefore, not recognise in the present pictures."
most recent contribution on this subject is from the French corre-
spondent of the British Journal of Photography, who, in the number
for July 18, 1890, writes to following effect :-"At the late meeting
of our society, M. Vallot presented some prints in natural colour.
Since the experiments of M. Verescz the attention of a great number
has been drawn to this subject. M. Vallot has been repeating the
experiments of M. Poitevin, and I myself cannot see that progress
has been made. A few years ago (twelve years) I travelled 200
miles to pay a visit to the father of photo-mechanical printing. When
receiving his hospitality, he showed me his collection of experiments.
of printing in natural colours. His results were far superior to what
was shown last Friday, or to what had been obtained by M. Verescz
(fixing apart). In case any amateur should like to procure a few
proofs in natural colours or to have a start on the road to some wonder-
ful discovery, I will here give the modus operandi employed by M.
Vallot, which he himself gave us last Friday evening:-Float strong
photographic paper for three minutes on the following solution :--
1. Sodium chloride.
Water.
20 grammes = 5 drachms.
100 c.c.3 ounces.
Dry the paper as rapidly as possible, then float for five minutes in
the sensitising bath.
2. Silver nitrate
Water.
20 grammes=5 drachms.
100 c.c.3 ounces.
Allow to drain a few seconds, and then wash the paper for ten
minutes under a stream of water.
"3. Plunge the paper for five minutes into a 20 per cent. bath of
sodium chloride, and wash a few minutes in running water.
the following solution:-
Distilled water
Protochloride of tin
Sulphuric acid
100 c.c.31 ounces.
3 grammes=46 grains.
10 drops.
Prepare
Of the above solution take 20 grammes (5 drachms) and water 500
c.c. (17 ounces).
4. Plunge the paper into this bath, and then take the tray con-
taining the solution and the paper into the light, and expose the
paper until it becomes of a dark violet hue; wash five minutes and
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MANUAL OF PHOTOGRAPHY.
dry the paper. During the drying prepare the two following solu-
tions :—
A. Potassium bichromate
Water.
B. Saturated solution of copper sulphate.
5 grammes=77 grains.
100 C.C.3 ounces.
5. Mix equal quantities of the two solutions and plunge the dry
paper into the bath, and that for two minutes. When dry the paper
is ready to be exposed.
"The subject before you,' said M. Vallot (a transparent poly-
coloured design for a stained window), was exposed three-quarters
of an hour in full sun.'
"6. When the paper is taken out of the printing-frame the colours
are very faint; in order to revive them, the print is plunged into the
following bath :—
Sulphuric acid
Water
•
20 c.c. = 5 drachms.
100 C.C. 32 ounces.
=
Care must be taken not to allow the prints to remain too long a time
in this bath, or the acid, after having revived the colours, would soon
destroy them. The proofs are now well washed, dried, and albumin-
ised, which gives vigour to the tones. Naturally,' said M. Vallot,
'the image must be preserved from the light, as no means of fixing
has yet been discovered.'"
A few years since the writer was shown by Sir H. E. Roscoe a
photograph of the solar spectrum in colour, faint but yet distinct,
which had been produced by Captain Abney; this also had to be
viewed by artificial light, as no means of fixing the colours had been
attempted.
It should perhaps be mentioned that the late Mr. Woodbury intro-
duced an ingenious method of giving photographs the effect of natural
colours. By arranging colours in a kind of matrix following the forms.
in a photograph, the colour was made to set off on to the photograph,
and when carefully done a very pleasing effect was produced. A
similar effect may be obtained by using lithographic tints.
Mr. R. E. Ives in 1888 proposed a means of producing the effect
of colour. He says: “There is much yet to be done in perfecting
the print-making part of the process. For the present I am satisfied
to obtain perfect heliochromatic prints on glass, so that the results
may be shown with the optical lantern, and have adopted the follow-
ing procedure :-The blue print is made by the cyanotype process, on
a film of gelatine attached to glass. The red print is made by the
so-called carbon process, with eosine for the colouring matter,-a
reversed print being thereby produced upon another glass. The
PROCESSES.
151
yellow print is made by the collotype printing process, or a specially
prepared film of collodion and gelatine. Several of the red and
yellow prints are made, and such prints selected as are found to pro-
duce a neutral black in the shadows when superimposed with the
blue print over a white surface; the colours are then correct in every
shade of the picture. After placing the yellow film picture between
the blue and red picture on a glass, and therefore in contact with
them, they are moved until the images are exactly superimposed;
and then fastened together by binding to complete the lantern-slide
heliochrome.”
In a lecture delivered before the Franklin Institute in December
1890, Mr. Ives, after giving the history of the subject of producing
the colours of Nature by the aid of photography, refers at length to
his own experiments in this matter, and he describes the means he
adopted in taking negatives and making the copies to be used in the
optical lantern. The concluding paragraph of the lecture is as fol-
lows:-"Composite heliochromy must always remain a comparatively
costly process, when carried out in a manner calculated to yield the
finest results, and can most profitably be brought before the public
in the form of optical lantern-lecture illustrations, not with the triple
lantern, but with the transparent colour-print heliochromes mounted as
lantern-slides. If the colour-prints are made by the Woodburytype.
process, such heliochromic lantern-slides, infinitely superior to hand-
painted ones, can be made in quantity at a cost not exceeding one
dollar each." 1
In solving the difficulty of making pictures which can be used as
slides for the optical lantern showing the colours of Nature, Mr. A. W.
Scott of Weston-super-Mare has succeeded in a very remarkable way.
The photographs are obtained in the following manner:—A camera
arranged with four lenses is used, and the negatives are taken on
orthochromatic plates, the light passing through colour screens, green,
blue, red, and violet. As the exposure is different for each colour,
diaphragms of suitable sizes are used. Transparencies for the nega-
tives are made in the usual way. Although presenting to the eye
representations of the subject of the ordinary kind, each picture has
different gradations of intensity according to the colours through
which the negatives were made.
In projecting the pictures on to the screen, the same colour plate as
that through which the early picture was taken is used, and as the
four pictures can, by the mechanical arrangement of the lantern, be
made to overlap or superpose, the effect, when the pictures are care-
fully registered, is a very near approach to a picture of the object in
1 From more recent description Mr. Ives appears now to adopt a method
similar to that used by Mr. Scott.
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MANUAL OF PHOTOGRAPHY.
the colours of Nature. The apparatus is called by the inventor the
Verak. A large range of subjects have already been produced, such
as a scarlet geranium with its green leaves, which has a most natural
appearance; sunrise; a wall covered with bills in many colours;
and many others, which the writer has seen. It appears to him that
in this direction a great advance has been made in making pictures
which imitate the colours of Nature. It must be noted that to pro-
duce these effects four pictures are required, and that this in no way
solves the problem of the production of pictures in colours at one
operation.
In what has been said, the work of fifty years has been passed in
review; and if we omit the Verescz experiments, about which so little
appears to be known, we have arrived at about the same point as we
started from the experiments with silver chloride and the changes
produced in the light of the solar spectrum; in fact, we are no nearer
now to a solution of the problem of photography in natural colours
than we were in 1839. As already remarked, it would be unwise to
say that the object sought for never can be realised owing to the diffi-
cult character of the chemistry of the subject; but as so much has been
done within the last fifty years to advance ordinary photography and
chemistry, the next half century may witness the evolution of a pro-
cess by which the objects photographed may at the same time possess
their natural colours, although it must be confessed there seems to be
very little probability of success attending efforts in this direction.1
Photo-Lithography. One of the earliest applications of photo-
graphy was the attempt by Niépce to obtain pictures on litho
graphic stone by means of bitumen, which he dissolved in oil of
1 Since the above was written, a statement has appeared in the Daily News of
February 11, 1891, to the effect that at a recent meeting of the Academy of
Sciences at Paris, it was announced that M. Lippmann had succeeded in obtain-
ing photographs in the colours of Nature. The method was only partly described,
but the chief means employed was said to be a mirror or a trough of mercury
placed behind the sensitive gelatino-bromide plate. Writing a day or two later
to the Photographic News, M. Leon Vidal stated that he had seen one of the
plates; that the colours were very faint; and that he would not have suspected
it was a reproduction of the solar spectrum if he had not been told so. It appears
certain that some results have been obtained, and in a way different from all
former methods; but all that was claimed for the discovery in the first announce-
ment appears to be far short of what is necessary to realise the effect of natural
colours on the photographic plate. Probably the specimen exhibited was not a
good one, or, if seen by artificial light, the perfection of the colours may not have
been apparent. The writer has seen two specimens of M. Lippmann's work, and
both were good, showing very perfectly all the colours of the spectrum, not faintly,
but bright and distinct (in daylight) by reflected light. M. Lippmann does not
claim to have done more than to have obtained the picture of the spectrum; but
this is fixed and varnished on the glass plate, and is therefore permanent. The
colours are of the character called iridescent.

9999
060
IRISH
LACE
Photolithographed by Messrs West, Newman & Co.
Hatton Garden. London.
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The image
lavender and then spread as a thin film on the stone.
obtained after long exposure was developed by washing away the
bitumen which had not been affected by the light with oil of lavender
and petroleum. The picture or design left on the stone was etched
in the usual manner, and could then be printed from. The principle
involved in this process, although it led to no immediate result, has
been applied in a very practical way during the last few years, and is
referred to in these pages in connection with zinc-etching. Many
attempts were made to utilise the method of printing direct on to the
lithographic stone, but with only partial success; and it was not until
the system of transferring an image originally produced by photo-
graphs on paper prepared with gelatine and potassium bichromate,
and causing this image to take lithographic ink, that the 'process
became of commercial importance. It has for many years been exten-
sively used for the reproduction of all kinds of drawings in line and
stipple; and, by modifications, half-tone pictures are now practicable.
Closely allied to photo-lithography is a modification, Photo-Zinco-
graphy; the only difference being that in one case stone is used, and
in the other zinc. Amongst lithographers there appears to be a pre-
judice against zinc, but the process has been largely employed by the
Ordnance Survey Department at Southampton, where the beautiful
maps produced there are enlarged or reduced by means of photo-
graphy, and transferred to, and printed from, zinc plates.
As the success of a photo-lithograph depends on the character of
the negative, the greatest attention must be given to its production.
Many attempts have been made to utilise gelatine plates, but as the
lines in the negatives must be clear glass, the collodion process is
usually employed. The gelatine process is not yet capable of yield-
ing negatives of suitable character for all purposes.
Success also in this process depends very largely on the kind of
drawing to be copied. When plans or drawings are specially made
for reproduction, the ink should be black, not grey, as Indian-ink
very often appears in drawings otherwise perfect. This greyness
makes it almost impossible to obtain the requisite clearness in the
negative, and the result is rottenness in the lines of the print from
stone. Another defect in drawings is that the lines are too thin.
When closely examined, it will be found that the pen has not made
a continuous line. On some kinds of drawing-paper the ink may
only have touched the top surface, thus causing broken lines in the
transferred copy; hence the lithographer is often blamed for what is
really the fault of the original drawing. Another defect in drawings
is the gloss in the drawing where large masses of black
occur; but
this, although it gives trouble to the lithographer, can be corrected by
him on the stone. Prout's brown is an excellent colour for line draw-
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MANUAL OF PHOTOGRAPHY.
ings; but the artist must not be tempted to improve the effect in his
drawing by diluting his colour. The drawing should in all cases be
made on white paper. Tracing-paper gives the photographer much
trouble; it is often very dark coloured; the lines drawn on it are
often not black, and as it is almost impossible to make a large tracing
lie flat, the consequence is that the lines may be out of focus. When
the tracing is separated from the white paper against which it is
pinned, there is a further defect introduced, by the full effect of the
black line not being seen.
The collodion may be of the ordinary kind used for negatives, or
collodion specially prepared for photo-lithography may be used, the
only difference probably being that it may contain more pyroxyline.
The silver bath should be distinctly acid, so that there may be no
tendency to fog.
The plate should not be removed from the bath until all streakiness
has disappeared, and it should be developed with iron protosulphate
(see Collodion Process); the proportion of iron may be varied at
discretion to suit the work in hand or the season of the year. Less
iron may be used in warm weather, but the proportions given are
quite suitable for all purposes.
The exposure in the camera should be as accurately timed as pos-
sible, and should be slightly under- rather than over-exposed. If over-
exposed, the clearness of the lines may be endangered, but when
slightly under-exposed a good result may be obtained. If the subject
to be copied makes it difficult to obtain density, development with
the iron should be continued until it is seen that no more detail will
appear, care being taken not to push the development too far; and
then, after washing, the plate may be redeveloped with pyrogallic acid
and silver; but here again care must be taken to avoid filling up the
lines. After fixing, the negative must be intensified to blackness.
This may be done with mercury bichloride in the usual way, and after
thorough washing, a solution of ammonia or sodium thiosulphate will
blacken the image. The following, however, is found by the writer
to give negatives in every way more suitable for photo-lithographic
work. Take—
Potassium ferricyanide (red prussiate of potash, com-
mercial)
Lead nitrate (commercial)
Water
4 ounces.
3
65
Place the negative in this solution and watch the result. If the nega-
tive has been fully exposed and developed, the lead solution will cause
sufficient intensification in a very short time, but a few minutes' im-
mersion in the lead bath may be necessary; the density may be
PROCESSES.
155
judged by looking through the negative. The lead changes the grey
colour of the collodion film to a bright yellow, but prolonged washing
under running water changes the colour to white. It is not necessary
in all cases to continue the washing till the yellow colour entirely dis-
appears. Take next-
Ammonium sulphide
Water
4 ounces.
20
Pour sufficient of this solution on to the plate, and allow it to flow to
all parts, then throw it away. The film is instantly changed to a
dense black (by transmitted light), but if looked at in a strong light
by reflection, it is seen that the colour is a rich purple. To ascertain
if it is completely blackened, look at the back of the plate, when, if
any part appears white, allow the sulphide solution to remain on
longer, or add more. The plate must now be carefully examined: if
any part appears to be over-dense or the lines filled up, the negative
must be cleared with the following solution :—
Nitric acid (commercial)
Water
•
ounce.
20 ounces.
or stronger if required. The necessity for using the clearing acid
solution appears to arise from imperfect washing. The negative
should be thoroughly fixed, and very thoroughly washed to free it
from the least trace of cyanide, when that salt is used. Careful treat-
ment with the nitric acid will clear the lines, but if they still appear
filled up, another negative must be taken, as the best work cannot be
made from a negative which has not clear lines.
The best possible negative having been obtained (and it cannot be
too strongly urged that upon the quality of the negative the success of
the succeeding parts of the process very much depends), the prepara-
tion of the transfer-paper may next be considered.
It is usual to say that the best kind of paper is that called bank-
post; but any paper of good quality which is hard and well-sized
will answer perfectly, provided it is not too thin. Most paper is dif-
ferent on its two sides; it may be noticed, by looking obliquely at a
sheet of paper with the light fully on it, that one side looks coarser
than the other; it is the smooth side which should be used. Look
over all the paper to be coated, and mark the right side. When
many sheets are to be treated, it is necessary to have some means of
keeping the solution of gelatine warm. A vessel rather larger than
the paper should be made in the form of a dish, with a reservoir to
contain water; or the dish and vessel for the water may be separate,
the dish to contain the gelatine resting in the lower dish over the
water. Beneath the dish a Bunsen burner must be arranged to keep
156
MANUAL OF PHOTOGRAPHY.
the water warm and to prevent the gelatine becoming unusable by
thickening on cooling. Now take
Nelson's gelatine
Water
3 ounces.
50
Soak the gelatine in as much of the water as will cover it; when soft,
the remainder of the water may be boiled and the gelatine added.
Filter through two or three thicknesses of fine muslin, and pour into
the dish, taking care not to form air-bubbles; remove any such as
may have formed, and proceed to float the paper. As soon as the
sheet lies flat, raise it to see if any air-bubbles have formed; remove
them, and allow the paper to remain two or three minutes. Raise
carefully and slowly, and at once place the sheet on a flat table, then
proceed to float another sheet. As soon as a sheet or two have been
floated the first one will have set, and can be pinned or held by clips
to a line to dry.
Paper prepared in this manner will yield good results, but a second
coating is sometimes given of the same solution of gelatine; or albu-
men may be substituted, taking-
Albumen
Water
•
4 ounces.
16
and proceeding as with gelatine; but in this case heat is not
necessary.
If the paper is to be used as soon as dry, it may be sensitised while
coating it with gelatine; but if the gelatine paper is to be made
sensitive to light at the same time as it is coated, the potassium
bichromate must be added to the gelatine solution; 2 ounces of the
bichromate to 10 ounces of water. It must be remembered, however,
that paper so prepared will not keep, and should be used within
a day or two of its preparation. Before sensitising the paper will
keep indefinitely. The remarks in this paragraph apply also to paper
prepared with gelatine and albumen.
When the paper is made sensitive after the coating with gelatine
or gelatine and albumen, take-
Potassium bichromate
Water
30
2 ounces.
Float or immerse the paper, and hang up to dry, which is better done
in a drying cupboard where the temperature can be raised to 80° F.
Paper for transferring to zinc may be prepared with arrowroot.
The process, as used in the India Survey Department at Calcutta, is
as under:

LACE CURTAIN.
A. Brothers & Co. Photo-Litho.
UNIL
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Arrowroot
Potassium bichromate
Water
140 parts.
70
3500
Hot water is used for washing off the ink in this process.
The paper when quite dry should be rolled to produce as fine a
surface as possible. If not rolled, the sheets may be placed face
down on a clean lithographic stone, and pulled through with con-
siderable pressure.
Some other methods have been used for preparing paper for photo-
lithography. This paper may be purchased ready prepared, but not
sensitised.
The printing is the next matter to be considered.
As great pres-
sure is necessary to bring the paper and negative into close contact,
glass at least three-eighths of an inch thick should be used in the
printing-frame. The filling in-that is, placing the paper on the
negative-should be done in a darkened room by yellow or artificial
light. Exposure to daylight requires much care, and the time neces-
sary will depend on the density of the negative and the quality of
the light. With a good negative and bright sunlight two or three
minutes may be sufficient, but in a dull light an hour or two is some-
times necessary.
When fully exposed, the image may be seen on
the yellow paper in brown lines; if the thin lines are just visible,
the exposure has been sufficient. If the prints are large, great care
must be taken in examining them while in the printing-frame to
ascertain the depth of the printing, as, if the exposure has been long
and the weather damp, the paper may have expanded; so that when
the pressure on one side of the frame has been released, it will be found
that the image has shifted on again screwing up the frame (spring
frames should not be used). With practice, it is possible to judge of
the depth of the print by the exposed margin of the paper, or by cover-
ing up a small portion outside the frame, when the depth to which the
paper has changed colour can be seen without opening the frame.
The print must now be coated with ink. As most lithographic
printers have a preference for ink of a certain kind, and as the
operator is not likely to be his own printer, it is better to obtain
a supply of re-transfer ink from the printer who is to transfer the
work to stone. The same assistance may be useful in inking the
print, two or three methods of doing which are available. The ink,
when thinned with turpentine, may be rubbed on to the print with
a fine sponge or with a tuft of lint. Others prefer to use the litho-
graphic stone, and, as a very thin layer of ink is required, this is the
preferable way to proceed. The lithographer will reduce the ink
and spread it over a clean stone in the usual way; the print must
then be placed face down on the stone and pulled through the press
158
MANUAL OF PHOTOGRAPHY.
two or three times. The ink will adhere to the print, and, after
about ten minutes (to allow the turpentine to evaporate), it may be
placed in cold water. The effect of this is to soften the gelatine
where the light has not acted, and to which the ink will not adhere.
After a few minutes, a clean sponge or tuft of lint gently rubbed
over the surface will remove the ink and leave the picture perfect,
as the ink cannot be rubbed off from the parts which exposure to
light has hardened. The prints must now be returned to the water
for the bichromate to soak out, when a final rub with the sponge
will remove all trace of the superfluous ink. Blot off the water and
pin by the four corners to a board to dry. When dry they may be
handed to the lithographer to be treated in the usual way. It is
sometimes stated that the damp prints may be at once transferred to
the stone; but, in doing this, there is danger that the fine lines of
the transfer may be crushed and made thicker than necessary. The
prints should dry in air, as fire-heat would cause the gelatine to run.
When quite dry they may be placed in the damping-book, and treated
as ordinary transfers. Re-transfer ink does not readily dry; con-
sequently, a transfer will not spoil by keeping a few days. The state
of the print may be tested by touching any part where there may be
ink outside the work; if the ink will rub off, the print may be used.
But a good workman, by having his stone at the proper temperature,
may succeed in making a good transfer from a print which may be
apparently dry.
In writing of photo-lithography, as of most other processes, it is
difficult to lay down rules for any difficulty which may arise; a
little practice will soon show the cause of failures. But it may be
said that the most likely causes of failure will arise from the negative
being too thin, over-printing, or over-inking. The effect of the first
will be seen in the over-printing, as the light passing through makes
the gelatine insoluble, so that the ink will not leave the surface ;
over-inking will be seen on transferring to stone, as the lines will
thicken. The remedies are obvious.
In processes where hot water is used to remove the superfluous ink,
the gelatine not acted on by light leaves the paper; but when the
prints are washed in cold water the surface of gelatine is not removed.
The writer gives this method the preference.
The accompanying illustrations show how admirably the process of
photo-lithography is adapted for the reproduction of designs. The first
is from a piece of Irish lace. Another is from a lace curtain reduced
about thirteen diameters; and, although the reduction is so great,
every thread of the design is distinct. The third plate is from
designs drawn by Miss E. Gertrude Thomson for the Gentlewoman
(to the proprietors of which paper the writer is indebted for the loan

E.G. Thomson-
Thomson
ENGAGEMENTS

ن کار
A. Brothers & Co. Photo-Litho.
FROM ORIGINAL DESIGNS BY MISS E. C. THOMSON.
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PROCESSES.
159
of the original drawings). For fac-simile work, such as the copying
of old books, manuscripts, maps, drawings of architectural and other
subjects, no process is perhaps so economical as the one by which
these illustrations are made; and it is probably the one which is most
extensively used.
A process called Papyrotype was patented by Captain Abney.
Paper is coated twice with gelatine and made sensitive with chrome
alum. The print is passed through cold water and then squeegeed on
to a zinc plate. The water is blotted off, and with a gelatine roller
the print is rolled up with ink-chalk-ink four parts, softened with
one part of palm-oil. The gelatine surface is thus treated as a litho-
graphic stone; water has been taken up by the soft gelatine, and
these parts will not take ink; therefore the rolling has developed the
picture in lines. As the bichromate has not been washed out, the
paper is still sensitive to light; hence, when dry, the print is again
exposed to light to harden the entire surface.
Photo-Micrography. The possessor of a good microscope, and one
who is a photographer, has in his power the means of endless interest
for the practice of his two hobbies. The microscope enables us to
see objects and reveals details of structure which, without its aid,
would be invisible; and photography gives us the means of delineat-
ing such objects in a manner very much superior to any kind of hand-
drawing, although the eye may be assisted by the camera lucida.
There is, however, a very large class of objects which can be photo-
graphed without a microscope, and which, when reproduced as lantern-
slides, become something more than diagrams. A small rectilinear
or other good lens suitable for enlarging attached to an enlarging
camera becomes, for the time, a low-power microscope, with which
excellent work can be produced. All insects, which are usually
mounted whole, and such other objects as are used with the lowest
power of the microscope, are suitable for enlarging with a photo-
graphic lens. The only addition to the ordinary camera required is a
means of extending the body so as to give sufficient length for the
negative to be made a few diameters larger than the object. The
copy thus obtained can be, if necessary, still further magnified when
making the transparency for the lantern, and in this optical lantern
we have the power of still further enlargement.
There are many ways of arranging microscopical apparatus to be
used for photographic purposes. It may be extremely simple or very
complex, as the temporary apparatus which will permit a fair negative
to be made from an object suitable for a one-inch objective would be
altogether unsuitable for use with the higher powers of the microscope.
When the photographic lens is adapted for enlarging microscopic
objects, there is no difficulty as to the chemical and visual foci, as the
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MANUAL OF PHOTOGRAPHY.
correction is already made in the lens. When the image is sharply
defined on the ground glass, all difficulty as to definition in the
negative disappears. When the object-glasses of the microscope are
used, it rarely happens that they are corrected for the actinic rays;
therefore trial must be made to determine the correct place for the
prepared plate.
When the enlargement required necessitates the use of microscopic
objectives, the simplest method of procedure is as follows:-Place a
camera of any kind adapted to use with the size of plate required (say
half-plate, 634) on a table, as shown in Fig. 37, or, preferably, on
a board about 4 feet long, having ribs at the sides between which the
camera may slide. At the other end place a microscope, one which can
be turned horizontally, and at a suitable position place a lamp, as
also, if necessary, a condenser to illuminate the object to be copied.
Arrange the slide on the stage, remove the eye-piece of the microscope,

SWIFT&SONJUN
HEADINCTON_
FIG. 37.
the stand of which must be raised so as to be central with the centre of
the camera, and, after covering the space between the microscope and
the camera with a black cloth, proceed to find the object on the ground
glass, arrange the size and focus. Excepting when it is absolutely
necessary to use the fine adjustment for focussing the object, the screw
of the camera may be used for that purpose. The black cloth must
now be carefully arranged so as to exclude all light, when the object
may be photographed. If the negative is not so sharp as the image
appeared on the ground glass, the fault will be in the object-glass,
assuming that there has been no tremor in the apparatus. The lens
may now be slightly drawn back from the object, using the fine adjust-
ment and noticing how many turns have been made to assist in find-
ing the focus at another time. If the slide carrying the sensitive
plate is capable of being moved into more than one position, a second
trial may be made on one plate.
The writer is indebted to Mr. G. J. Johnson for a description of a
very ingenious camera for microscopic work; and also for the use of
the photographs reproduced in collotype by Messrs. Martin, Billing,
Son, & Co. of Birmingham.

DIATOMS, X 30.

CATERPILLAR OF MOTH, x 3.
PHOTOGRAPH BY MR. J. J. JOHNSON.
COLLOTYPE BY MESSRS. MARTIN BILLING, SON, AND Co.,
LIVERY STREET, BIRMINGHAM.

NIL
OF
MICH
PROCESSES.
161
Mr. Johnson says: "I use a long extension camera, fitted for the
purpose of taking both photo-micrographs and micro-photographs.
"The bellows is divided into two removable sections by the inser-
tion of a frame which supports the middle. The frame, being inter-
changeable with the end containing the lens, can be used for holding
negatives for enlargement, different-sized carriers being provided for
the several dimensions of plates.
"For photo-micrography, or the enlarged delineation of micro-
scopic objects, the microscope is provided with a short tube, in place
of the usual 10-inch body, to allow photographs to be taken without
the use of the eye-piece, thus giving a wider field. It is also provided
with a mechanical stage giving rectangular motions.
In front of the dark slide a small removable cardboard shutter,
about 2 inches deep and 4 inches wide, is worked perpendicularly by
a square wooden rod, sliding stiffly through a hole cut in the top of
the camera, about half an inch in front of the sensitised plate. By
means of this shutter various periods of exposure can be given to
successive bands on the same plate, the square rod being depressed at
stated intervals. This method of testing the strength of the illumi-
nant at the outset of a night's work is found to be a great saving in
time and plates, the correct exposure varying in character with every
change of lens, object, or length of camera employed. Transparent
objects, such as the wing of a gnat or a thin section of the stem of
the dog-rose, require much less exposure than, say, the proboscis of a
blow-fly or a vegetable section stained deep crimson.
"As correct focussing is of great importance in this class of work, a
one-inch focussing lens is mounted in a small tube, inserted in a stout
level lath about 12 inches long, in such a manner that when the
lath is pressed home to the back of the camera, the focus of the lens
coincides with the plane of the ground-glass screen. The screen can
then be removed, and, by moving the lath laterally or perpendicu-
larly, any portion of the field may be brought into view and adjusted
to focus by the use of this temporary eye-piece.
"The necessity of stops for some lenses may thus be proved by
actual visual inspection, a 2-inch objective sometimes requiring to be
stopped down to 4-inch or -inch of aperture, to ensure clear defi-
nition and depth of focus. Care, however, must be exercised to avoid
excess of reduction in aperture, which impairs definition.
16
"Micro-objectives are now sold as corrected for photography, but
many of the ordinary microscopic lenses of good make give better
results when once the difference between the visual and the actinic
focus is determined and allowed for."
The instrument is fitted with various mechanical adjustments, which
cannot very well be indicated without elaborate diagrams.
L
162
MANUAL OF PHOTOGRAPHY.
For illuminating the object the ordinary microscope paraffin oil-lamp
may be used, or, with some objects, daylight. For very opaque objects
sunlight may be preferable; but the light should be passed through a
medium, such as ground glass, to take away scintillations caused by
the direct light.
The illustration is a collotype from a negative by Mr. L. Atkinson,
from one reproduced by Mr. Danielsson. The subject at the top of
the plate represents a section from a portion of a healthy eye; it
shows the entrance of the optic nerve, its connection with the retina
and the Lamina cribrosa. The lower figure shows the same parts of
an eye affected with glaucoma. The section was made by Prof.
Delépine of the Owens College, and represents the subjects enlarged
20 diameters. These illustrations are admirable, as showing the per-
fection of the photographic delineation, and the value of the process.
of collotype for the purpose of book illustration.
Photophane.Collotype prints, varnished or unvarnished, are, by
the Company producing them, called Photophane.
Phototint.—This title was given by Mr. Cocking to a method of
double-printing; first, from an ordinary negative, portrait or land-
scape; and, secondly, from a negative prepared by hand in such
manner that effects were obtained to enhance the light and shade
and at the same time to tint portions of the original picture.
Collotype prints transferred to and printed from stone have been
called Phototints.
Photo-Typography.-Any drawing in line or stipple may, by the
aid of photography, be converted into a plate, which, when mounted on
wood, may be printed with type. The process is now very largely
used, and for many purposes is quite equal to wood engraving, and of
course is very much cheaper. The drawing should be made in clear
firm lines, and preferably somewhat larger than the etching is intended
to be.
When a line block is to be produced on zinc, and to be printed
direct on the metal, a reversed negative must be used; but when the
outline is transferred to the plate, an ordinary negative is necessary.
The illustration is an etching on zinc made from a drawing in line
and stipple on smooth paper. It is produced by the swelled gela-
tine process used in America, and in England by the Typo-Etching
Company. (See Zinc Etching).
Another method of producing a block from a drawing and photo-
graph is described in the article on Indian-Ink Outlines.
Pinhole Photography.-It has long been known that photographs
can be taken without a lens; that the light passing through a minute
hole punctured in a card will produce an image, and that if a sensitive
plate be placed to receive the image, a picture may be developed. The

Section of portion of healthy Optic Nerve.
Section of the same part, showing Glaucoma cup.
MAGNIFIED 20 DIAMETERS.
to-micrographs lent by Dr. Delepine.
UNIL
OF
Collotype by Danielsson & Co.
MICH
PROCESSES.
163
1
30
experiment is an interesting one, and may be tried by any one pos-
sessing a camera. The size of plate is of little consequence, but the
length should not be too great, owing to the increased exposure
necessary. Remove the lens, and in the diaphragm slot place a card
or thin strip of metal, such as a ferrotype plate, in the centre of which
an aperture has been punched of about th of an inch diameter. This
may be made by breaking a needle of the proper thickness and making.
the hole with the blunt end. Lay the thin plate on a piece of lead,
and then use the broken needle as a punch; holes of various sizes.
may be made, to be used as may be found desirable. The view
having been selected and the camera arranged (using the lens and
ground glass in the usual way), the plate may be inserted, the lens
removed, and the pinhole diaphragm put into its place and the ex-
posure made, care being taken to carefully cover the camera and lens
slot so as to exclude all light excepting that passing through the pin-
hole. The exposure will vary, according to the length of the camera,
the light, and the size of the aperature, from five to twenty minutes or
The image is visible no matter what the length of the camera
may be, but its sharpness will depend on the size of the pinhole. It
will be seen, of course, that an ordinary camera is not necessary.
box of suitable size, with some means of holding the plate perpen-
dicular at one end, and an aperture at the other (which may be
covered with the thin plate or card in which the hole is pierced) may
be made use of in this experiment. See page 37, where the principle
of the pinhole camera is shown.
more.
A
Platinotype Process.-The red colour of photographs on paper
when silver alone is used is not pleasing to the eye. This defect led
to the method of gold toning for the purpose of changing the colour.
At the same time it was supposed to add to the permanence of the
photograph by the chemical substitution of the more permanent gold
for the silver compound forming the picture. It was soon found, how-
ever, that, from some cause never quite satisfactorily explained, the
gold-toned silver print was very little more permanent than the un-
toned print. This led to the introduction of forms of printing about
which there could be no uncertainty, the basis being carbon, as in the
carbon process, collotype, and allied methods. One of the most beau-
tiful, and at the same time one which gives permanent results, is
the platinum process, which has been brought to great perfection by
Willis in England and by Pizzighelli of Benjaluka, Bosnia. That
the process will entirely supersede the old form of print on albumenised
paper may be doubtful, owing partly to the extra cost of the platinum
method, the necessity for purchasing the paper from one source, and the
precaution that has to be observed in keeping it; but the chief reason
is probably owing to the simplicity of the method of printing on albu-
164
MANUAL OF PHOTOGRAPHY.
menised paper, which is now in such universal use. There can be no
doubt also that the beautiful effect in a good print on albumenised
paper has much in its favour; but, at the same time, it must be con-
ceded that the artistic effect in a perfect platinum print is superior to
any other kind of photograph, although a good print on silver bromide
paper approaches the platinum effect very closely.
As early as 1832 the salts of platinum engaged the attention of Sir
John Herschel, and he found in 1840 that light reduced the ferric
salts to the ferrous state. Hunt also experimented with platinum. It
was, however, reserved for Mr. Willis to bring into use the platinum
salts in combination with ferrous oxalate in his process, by which the
most perfect kind of print may now be produced.
The Willis process is patented; the paper can only be obtained
from the Platinotype Company; and, until recently, a license was
necessary for its use. The paper may now be used without restric-
tion, if obtained direct from the Company. Owing to the care required
in the various manipulations, even if the patent restrictions did not
prevent the photographer making his own paper, it is unlikely, until
the process is still further simplified, that home-made paper will
be used. As in the case of the ready sensitised silver papers, the
operator will prefer to purchase the paper rather than have the trouble.
of making it.
Without going fully into detail as to the mode of preparing the
paper, it may be stated generally that platinotype printing has been
the subject of three patents by Mr. Willis. In the first, dated
July 1878, 1 part of potassium chloro-platinite was dissolved in 48
parts of water. The paper was coated with this solution, dried,
and then dipped in lead-nitrate I part, and water 48 parts. After
drying, the paper was brushed over with 1 part ferric-oxalate in
8 parts of water, to which oxalic acid was added. When dry, the
paper was ready for printing, and was afterwards floated on a hot
solution of potassium oxalate. The print was then washed in a solu-
tion of oxalic acid, again in "hypo," and finally in water. A modi-
fication was made by using, instead of the lead, I part of silver
nitrate in 60 parts of water; and after treating with the oxalic acid,
the prints were dipped in a strong solution of ammonium chloride,
and then washed. For a third modification, the film was dipped
in I part of platinic bromide in 40 parts of water, dried, and then
dipped in a strong solution of ferric tartrate; the after process being
the same as in the first method. The foregoing contains the instruc-
tions as given by Willis, but in a very condensed form. In 1878 the
process was further modified, and a second patent was taken out.
The formula for the preparation of the paper contains-
PROCESSES.
165
Potassium chloro-platinite
Ferric oxalate
Lead chloride
Water
•
•
I part.
4.5 parts.
0.13 part.
30 parts.
After drying and exposure under a negative, the picture was deve-
loped by dipping in or floating on-
Potassium chloro-platinite
Potassium oxalate
Water.
•
0.5 part.
8 parts.
30,
""
All further manipulations are the same as previously described, and
the specification claims that the salts of gold, iridium, and other
metals can be used, and that the lead chloride can be omitted;
various other alternatives are named, as is usual in patents. Instruc-
tions are usually given in general terms only; minute details necessary
to the full working of a process are often not given, particularly in
cases where the patentees keep the preparation of the article patented
in their own hands.
A third patent was taken out in 1880, the process being further im-
proved and simplified, the quantity of platinum in the sensitising.
solution being increased and the lead omitted; no platinum was used
in the developing solution. The latter solution is given as-
Potassium chloro-platinite
Ferric oxalate
Water
·
4.2 parts.
4.2
""
30
It will be seen in the full instructions that this formula is modified.
In the Photographic News, 1882, p. 157, the following is given by
the late Mr. H. B. Berkeley as the reaction which takes place in the
formation of the platinum image.
For the platinous chloride-
Ferrous
Platinous
Oxalate.
Chloride.
Ferric
Oxalate.
Ferric
Chloride. Platinum.
6FeCO + 3PtCl₂
=
2Fe(C2O4)3 + FeCl + 3Pt
For the platinic chloride:
Ferrous
Oxalate.
Platinic
Chloride.
Ferric
Oxalate.
12FeС₂O + 3PtCl₁
Ferric
Chloride. Platinum.
4Fe(C2O4)3 + FeCl + 3Pt.
6
The platinotype process may now be worked by two methods; in
one, the prints are developed with a hot solution of potassium oxalate;
and in the other, the solutions, the composition of which is not pub-
166
MANUAL OF PHOTOGRAPHY.
lished, are used cold. The following is a summary of the instructions
issued by the Company for using the hot-bath process :—
To secure the most brilliant results, the sensitised paper before, dur-
ing, and after its exposure to light must be kept as dry as possible. It
is necessary to place between the sensitised paper and the pads a sheet
of thin vulcanised india-rubber, as it is of the first importance that
the pads in contact with the paper be quite dry. The effect of damp
is seen in a want of vigour, a general muddiness of tone, and, where
the sensitised paper has been exposed to its influence for some days,
in the impaired purity of the whites.
The correct exposure (about one-third of that required with silver-
printing) is ascertained by inspection of the paper in a rather weak
white light in the usual manner. A little experience will enable the
exposure to be determined very accurately. As a general rule, all
parts of the picture except the highest lights should be visible when
the exposure is complete. When examining the prints in the print-
ing-frames, care should be taken not to expose them unduly to light,
for the degradation of the whites of the paper due to slight action of
light is not visible until after development. Remove prints to a calcium.
tube as soon as exposure is complete, unless they are to be at once
developed.
Development should be conducted in a feeble white light, similar to
that used when cutting up the paper, or by gas-light. The developer
is made by dissolving one pound of the potassium oxalate in 54 ounces
of water. Use hot water for making the solution, of which a large
quantity may be made up; it will keep indefinitely. It is well to
have at hand some unused solution, since, in the event of inferior
prints being made, a new bath may at once be tried. The solution is
conveniently contained in a flat-bottomed dish of enamelled iron,
heated by a small Bunsen burner.
L
The development is effected by floating the printed surface of the
paper for five or six seconds upon the developing solution. To avoid
air-bubbles, lay one edge of the print upon the solution near the
right-hand end of the dish; then, with a sliding motion towards the
left, lower the print, with an even movement, without stoppage, until
t is entirely in contact with the liquid, where it must remain until
complete action has taken place.
A temperature of about 140° Fahr. may be considered the standard
temperature for the developer, though higher and lower temperatures
may be used. A thermometer must be employed. The bottom of the
developing dish should be covered with the developing solution to the
depth of at least half an inch. After the prints have been developed,
put the solution, without filtering, into a bottle for future use; it
should not be exposed to a strong light. When next developing,
PROCESSES.
167
the solution will be found to be nearly clear, but, of course, tinted by
previous use. If this clear solution be not sufficient, add to it some
of the fresh solution of the potassic oxalate.
The following formula is very strongly recommended by the Com-
pany as a new developer. It gives more brilliant prints than the oxa-
late developer, with pure tones and transparent shadows. Dissolve
half a pound of "developing salts" (used in the cold-bath process) in
50 ounces of hot water.
The best temperature for developing is from 120° to 130° Fahr.
Below 120° the development is slow, and can be watched, which is
sometimes advantageous.
To clear the developed prints, they must be washed in a series of
baths (not less than three) of a weak solution of hydrochloric acid.
This solution is made by mixing one part of hydrochloric acid with
60 parts of water. The specific gravity of the acid should not be less
than 1.16; if lower, more acid should be used The acid should be
colourless. Or citric acid, in the proportion of 1 ounce to 20 ounces
of water, may be used. This softens the paper in less degree than
does the hydrochloric acid. A white opalescence of the bath shows the
necessity for more acid.
As soon as the print has been removed from the developing dish, it
must be immersed, face downwards, in the first bath of this acid, con-
tained in a porcelain dish, in which it should remain about five
minutes; meanwhile, other prints follow until all are developed.
The prints must then be removed to a second acid bath for about ten
minutes; afterwards to the third bath for about fifteen minutes. While
the prints remain in these acid baths they should be moved so that
the solution has free access to their surfaces, but care should be taken
not to abrade them by undue friction. It is impossible to affect the
image per se by leaving the prints for a long time in the acid baths ;
but such treatment, continued for an hour or more, tends to make the
paper soft and porous, and to damage the surface. The prints should
not communicate to the last acid bath the slightest tinge of colour.
If the bath, after the prints have been washed in it, does not remain
as colourless as water when a depth of fully two inches is viewed in
full daylight, the prints should be treated to yet another acid bath.
For each batch of prints fresh acid solution must be used. After the
prints have passed through the acid baths, they should be well washed
in three changes of water during about a quarter of an hour. It is
advisable to add a pinch of washing-soda to the second washing water,
to neutralise any acid remaining in the print. Use a mountant which
does not stain or show through the print. Gelatine alone is not suit-
able, except for thick paper. Thick cold starch (or, better, starch
and gelatine) is a good mountant. Paper to give sepia tones may be
168
MANUAL OF PHOTOGRAPHY.
used, but, with few exceptions, the method of carrying out the opera-
tions is the same as for the "black" kinds of platinotype paper.
The cold process for developing platinum prints must be conducted
as follows, and it will be observed that every care must be taken to
keep the paper dry when the hot process is used, but in the cold
process a certain degree of moisture is necessary :—
The following is a summary of the method of printing by the cold-
bath process:
The paper, sensitised with salts of iron, is exposed under the nega-
tive in the usual manner; it is then suitably moistened by floating,
or otherwise, upon a solution of the developing salt, to which has
been added a prescribed proportion of the platinum salt. Imme-
diately after this the print is washed in a weak solution of hydro-
chloric acid, and finally in water.
It is important to avoid the contact of metallic dust and metallic
surfaces with the sensitised surface of the paper. The following pre-
cautions should be taken :-The lower half of the calcium tube must
be lined inside with paper. The prepared paper is then placed in the
lined portion with its sensitive surface bent outwards or convex.
And in putting paper into the tube, and also in removing it, care
must be taken that its surface does not touch any of the unprotected
metallic surfaces of the tube.
Spots and streaks are also caused by the contact of platinum salt
with the surface during its exposure to light. It is, therefore, impor-
tant to avoid handling the paper with fingers which have just pre-
viously come in contact with paper containing platinum salt, such as
hot bath paper; and if the negatives have been used for printing on
such paper, they must be carefully dusted to free them from any
platinum salt which they may have derived during contact.
General treatment of the paper.-The presence of moisture in the
paper, either during its exposure to light, or afterwards and before
development, is important. Sufficient moisture will be present when
the paper has lost its crispness, but if allowed to become limp the
moisture will be excessive.
If it should be necessary to delay development for one or two days,
the prints must be dried before a fire soon after they are removed
from the frames, and then stored in a calcium tube until wanted for
development.
Exposure to light.-This is effected in a printing-frame in the usual
manner. When exposed to light behind a negative, the lemon colour
of the paper receives an image of a greyish tone. The exposure is
somewhat less than that required with the old process-perhaps about
one-third less. As a general rule, all details observable on the exposed
print are developable, and the converse of this is also generally true;
PROCESSES.
169
but here it should be observed that the action of light on skies is
not often clearly seen unless the rebate of the negative has been pre-
viously rendered opaque by painting with opaque varnish, so that the
tint of the sky may be compared with the original colour of the paper
which is preserved by the opacity of the "rebate."
It is important to remember that if paper be exposed in a damp
state, the visibility of the image is less than if exposed in a dry state.
On this account beginners will find it easier to expose dry, and damp
the prints afterwards.
Development.-Stock solutions.
Developing-salts (D.).-Half a pound to be dissolved in 50 ounces
warm water, and the solution labelled D.
Platinum salt (P.).—Sixty grains to be dissolved in 2 ounces of
water, and labelled P.
Solution D. must, for general use, be diluted in the following pro-
portion :-
D. solution .
Water.
3 parts. Label this solution
2 parts.
"Diluted D."
The standard developer is made by mixing I part of solution P.
with 5 parts of "Diluted D." solution.
All these solutions should be accurately made up and correctly pro-
portioned.
The mixed developer keeps in good condition for some hours after
mixing, but it afterwards slowly deteriorates; and in order to secure
due economy in the use of the developer, it is important to mix no
more at a time than is sufficient for the prints to be developed. In
developing a very large batch, perhaps the best way is to mix the
whole quantity necessary, but to put into the developing dish only
sufficient to render the floating of the prints an easy matter, and then
to add the remainder by degrees as may be found necessary.
In order to develop, pour sufficient of the developer into a porcelain
tray to well cover the bottom, and then float the print, with its
printed surface downwards, upon the solution; after the lapse of two
or three seconds it may be lifted from the solution and held in the
hand. A few seconds after the print has thus been removed from
the developer, it should be again similarly floated and raised; and
these operations may require to be repeated, but this will depend on
the strength of the print.
The object of refloating the print is thus explained. When a print
is first raised from the developer, the liquid adhering to its surface
contains only a small quantity of platinum salt (the developer being
weak in this ingredient), and the amount of salt so taken up is usually
insufficient to supply the necessary quantity of platinum pigment to
170
MANUAL OF PHOTOGRAPHY.
the shadows and darker parts of the print; by refloating, a fresh
supply of this pigment-forming liquid is supplied, and the number of
floatings required is determined by the strength of the print.
After the print has been twice floated it should be held in the hand,
face upwards, and the progress of development carefully watched.
When the half-tones have sufficiently appeared, and have become free
from the granulation usually visible in the first stages of development,
and the shadows also are sufficiently strong, the print should be at
once immersed in the acid-clearing bath.
The clearing and washing are the same as in the methods adopted
for these purposes with the earlier processes.
After the prints have passed through the acid bath, they should be
well washed in two or three changes of water during about a quarter
of an hour. They are then finished.
These prints being on plain paper, are better dried face upwards
across glass tubes, or, if large, suspended by clips or pins. The prints
also may be dried between clean blotting-paper. Any mountant which
is clean may be used.
Paper which has been kept some time, and which will not give
good results in the ordinary way, may be left in the printing frame
until fully printed, and then developed, or rather fixed, in a nearly cold
solution of ferric oxalate.
Pizzighelli's Process.-Captain Pizzighelli and Baron Hubl have
published two methods for producing photographs in platinum; one
is very similar to Willis's, but the other permits the full printing of the
picture as in other direct printing processes. In Anthony's Interna-
tional Annual for 1888, as also in the late Mr. Iselin's translation of
Pizzighelli's and Hubl's description of the processes, full directions will
be found for the preparation of both kinds of paper-one for develop-
ment and the other for direct printing. Of the latter the following
is a very condensed description. Any kind of paper with a hard
surface may be used, but to prevent the sensitising solution penetrat-
ing the paper too deeply, the surface is brushed over with paste
(formed of arrowroot 2 parts, water 100 parts) applied cold; it is
then hung up to dry and the process repeated; but in drying the
sheet the second time, it must be suspended by the opposite end of
the paper. To make the paper sensitive take
A. Potassium platinous chloride
Distilled water
B. Sodium ferric oxalate
Solution of sodium oxalate (3 100)
Glycerine (to be added in very dry weather)
I part.
6 parts.
40 parts.
100
3
""
In mixing the solution B. the soda oxalate solution is heated to (40°-
PROCESSES.
171
50° C.) about 120° F. and then soda ferric oxalate is dissolved in it,
followed by filtration when the solution has cooled. This solution
may be mixed in large quantity and kept in stock.
C. Iron solution B.
Potassium chlorate
D. Mercury chloride solution (5 : 100)
Sodium oxalate solution (3 100).
Glycerine
100 parts.
0.4 part.
20 parts.
40 ""
I.S
Different effects may be obtained by using the solution in varying
proportions. For black pictures, and where the negatives are of ordi-
nary density (it may be stated here that the results in platinum print-
ing depend very much on the quality of the negative, and that no
good results can be had from a weak one), take-
Platinum solution A.
Iron solution B.
Iron chlorate solution C..
5 cc. 85 minims.
6
102
2 34
"}
When the negatives are dense, reduce the quantity of solution C., and
for softer negatives increase the quantity.
For brown pictures use―
Platinum solution A.
Iron chlorate solution C.
Mercury chloride solution D.
•
5 cc. 85 minims.
4
68
4
68
For tones between the black and brown the proportions of solutions
C. and D. are varied. The solutions are applied, first, with a bristle
brush (without tin mounting), and then spread evenly with a camel's-
hair brush; the paper should then be dried quickly in a warm room.
When dry, the paper must be kept in calcium-chloride tubes.
Paper without the special preparation with arrowroot may be used
if 30 parts of powdered gum arabic (picked white) be added to solu-
tion B. The gum when heated to 120° F. is mixed with oxalate and
glycerine solution by stirring in a mortar. When mixed the solution
is strained through a cloth. The other solutions are used in the same
proportions for both kinds of paper.
"The printing is continued until the picture has the appearance it
is intended to have finally. If many pictures are done, they are
placed in-
Muriatic acid
Ordinary water
•
I vol.
8 vols.
Change this two or three times, until no more green colour is
visible, and then wash the pictures in two or three changes of water.
172
MANUAL OF PHOTOGRAPHY.
"If the prints are not to be finished, they can be finally developed
in the following solution :—
Sodium carbonate
Water.
5 parts.
•
100
"In damp, warm weather, it is sufficient to have them lay in the
dark, where they will complete themselves, the action of light intro-
duced causing decomposition even in the dark.”
In this process (the Pizzighelli) the paper while in the printing-
frame requires a certain amount of moisture, and this can be effected
by breathing on the paper in the printing-frame. Since Captain
Pizzighelli wrote the article from which the above is summarised, it
has been pointed out by a writer in the International Annual for
1890–91, that when damp platinum paper was left in contact with an
unvarnished gelatine negative for a week, a reduction of density had
taken place to the extent of 50 per cent. ; and it is also stated that
a single coat of varnish must not be relied on to prevent the mischief.
Another writer in the same Annual states that one great advantage
of the Pizzighelli paper is that it does not deteriorate rapidly if not
kept in calcium tubes.
The platinum process of printing has many advantages, as, omitting
the preparation of the paper, the various manipulations can be carried
through in much less time than is required for silver-printing. The
exposure to light is less by about one-third, and the subsequent
operations, including mounting the print, may be rapidly completed.
The prints are undoubtedly permanent, as the tests to which they
have been subjected show. The picture is formed of metallic plati-
num, which metal is one of the most stable known. None of the
chemical tests which have been applied have any effect in destroying
the image, excepting aqua regia (which is a mixture of nitric and
hydrochloric acids), to which, under ordinary conditions, no plati-
num picture is ever likely to be exposed. The process has become
very popular during the last three or four years; but the recent
increase in the price of the metal may check the demand for platinum
prints, owing to the extra cost. That platinum will supersede silver-
printing may be a matter of doubt. A good print on albumenised paper
has to some persons a specialty which the print on salted (silver)
paper or platinum does not possess; but the artistic quality of platinum
prints has advantages which the silver (albumenised) print has not.
The two kinds of photographs should not be seen side by side, as
their qualities are totally different.
Plumbago Process (see Dusting-on Process and Ceramic Photo-
graphy).—Formulæ have already been given, but the following may
be added:
PROCESSES.
173
1. Gum arabic
Glucose
Glycerine
•
Potassium bichromate
Water
2. Ammonium bichromate
Honey
Albumen
Water (distilled)
•
I drachm.
10 drops.
30
""
2 ounces.
5 drachms.
3
3
""
30
The process is useful in making duplicates and increasing density
in negatives. The solution should be kept in the dark.
Preference is given by Mr. W. K. Burton to the following formula,
given in two solutions, as, when separate, they do not deteriorate.
They must be filtered and used in the proportion of three parts of A.
to one part of B. :-
A. Gum arabic (best)
Loaf-sugar
Mercury bichloride
Methylated alcohol
Water
•
B. Ammonium bichromate
Water
•
1000 grains.
1000
5
""
19
IO Ounces.
40
>>
2
""
20
39
A sheet of suitable glass, preferably patent-plate, must be coated
with the solution in the same way as collodion, and well drained, so
that after it is dried by fire heat-about the temperature used in
varnishing, not hotter-the plate appears of a pale yellow colour.
While still warm, the plate is exposed to light under a negative.
Experience only will show the correct exposure. Plumbago powdered
very fine is used to develop the negative, and must be applied to the
plate, which has been again warmed, with a camel's-hair brush, and
great care is necessary to apply the powder evenly. Density may be
given to any part as desired, but success depends very much on
correct exposure and skill in applying the powder. When the
"dusting on" is finished, the plate is coated with plain collodion,
and washed till the water flows evenly; then it must be placed in a
strong solution of alum, where it must remain until the yellow colour
has been removed. The negative thus obtained will, of course, be
reversed, which is an advantage for some purposes; but if required
for ordinary printing, it may be stripped from the plate and floated on
again in the reversed position.
Primuline or Diazotype Process.-Processes for printing on textile
fabrics have hitherto been of little commercial value, owing probably
to the necessity of separate exposures to light, as in ordinary silver
and other printing methods; and it may be that the newest will not
possess more than scientific value. There is certainly novelty in the
fact that amongst the derivatives of coal-tar one should be found
174
MANUAL OF PHOTOGRAPHY.
which is sensitive to light, and possesses qualities unlike those of
other salts used in photographic processes; this new salt is primuline.
At the last meeting of the British Association held at Leeds a paper
by Messrs. Green, Cross, & Bevan was read, but at the time of writing,
that paper is not published. The following information is derived from
a leading article by the editor, Mr. J. T. Taylor, in the British
Journal of Photography for 17th October 1890.
The calico or other material to be used must be thoroughly washed
in hot water, or boiled to free it from impurities. It is then cut into
pieces of convenient size, placed in the solution of primuline, and kept
in constant motion as when toning prints. The dye is prepared by
boiling 150 grains of the commercial primuline in 10 ounces of water
in a flask on a sand-bath. The solution is poured off from the sedi-
ment into a porcelain dish, and the calico after ten minutes' immersion
will be found to be sufficiently stained. The quantity of solution
will be sufficient for sixteen pieces of cloth 8 x 6. The dyed cloth
or calico must now be rinsed in water and wrung out, and then
placed singly in the following solution :-
Sodium nitrite (commercial)
·
Hydrochloric acid (commercial)
Water
100 grains (dry).
fluid ounce.
30 ounces.
In this solution the cloth changes to a reddish brown tint, owing to
the primuline being converted into a diazo derivative. It is now
sensitive to light, which both destroys the azo-derivative and prevents
its reaction with certain developers. The resulting print is a positive
from a positive.
After the pieces of cloth have been turned over several times in
the nitrite bath, they must be rinsed in several changes of water to
remove the free hydrochloric acid; they may then be placed between
blotting-paper to dry.
To obtain the best effect in the prints, the object used in printing
should be somewhat denser than is necessary in other processes; natural
objects, such as ferns and leaves, being very suitable. The progress of
the print may be seen in the change of colour from reddish brown to a
dingy yellow. The density in the object to be printed is necessary,
as the printing should go through the material. When this cannot be
effected, the back of the cloth should be exposed to light for about a
fifth or sixth of the time required for the original printing.
The printed pieces of cloth are now steeped in water and wrung
out, to secure equal action of the developing solution, which for red
prints is prepared as under :-
Beta-naphthol
Caustic soda or potash
Water
40 grains.
60
IO Ounces.
PROCESSES.
175
4CC
Dissolve the alkali in a small quantity of water rubbed up with
naphthol, and then add the remainder of the water. Orange coloured
prints are obtained with
Resorcin.
Water
30 grains.
IO Ounces.
Dissolve, and then add 50 grains of caustic soda or potash. For
purple prints-
Naphthylamine
Hydrochloric acid (commercial)
Mix in a mortar and then add 10 ounces of water.
60 grains.
I fluid drachm.
Other developers have been indicated by Messrs. Green, Cross, &
Bevan, but they do not appear to have used any of the salts now
commonly employed in developing dry plates, such as eikonogen,
pyrogailol, or hydroquinone, which Mr. Taylor finds will give the black
tone desired by the discoverers of the process
Eikonogen
Water
60 grains.
IO Ounces.
The eikonogen (white crystals) should be ground in a mortar, the
water added, and the prints on cloth put into the solution, in which
they are moved till the development is complete. For brown tones—
Pyrogallol
Water
50 grains.
IO Ounces.
The prints, when
which is found to
The "fixing" is effected by washing in water.
wrung out, may be washed in soap and water,
improve the colour, and ironed between sheets of paper, but this
should be done before the prints are quite dry.
It may be stated that the process as introduced by Messrs. Green,
Cross, & Bevan is patented, but that the patent does not appear to
cover the modification adopted by Mr. Taylor.
One of the peculiarities of this process is that the image is formed
by the parts which have not been acted on by daylight.
By modifying the manipulation the process may be used for paper,
but it is not very clear to what useful purpose it may be applied;
and although the dye may be capable of withstanding chemical tests,
it has not yet been proved that the test of light may not be fatal to
the results, as is the case with other dyes derived from coal-tar.
Printing and Toning.-Until the last few years the majority of
photographs were printed on albumenised paper, which is perhaps,
even now, the most popular process. Bromide and platinum papers
176
MANUAL OF PHOTOGRAPHY.
are also largely used. Descriptions of those methods of printing will be
found elsewhere in these pages. Albumen has the effect of keeping
the picture which is printed on it upon the surface, and it thus retains
a more effective appearance than when printed on paper without the
albumen, called in that case "plain salted paper." Prints of the latter
class, when looked at by transmitted light, will appear to have the
picture more in the paper than on the surface; the brilliant appearance
of albumen prints is thus due to the albumen, the picture being on the
surface of the paper. Everything in these latter days is done for the con-
venience of the photographer, so that he need not prepare the albumen
nor float the paper upon it; he can, if he please, sensitise this paper
by floating it on silver nitrate solution, but paper so prepared must be
used at once, as it turns brown by keeping. Here the convenience of
the photographer is again studied, for he can purchase his paper ready
sensitised, which keeps its colour for some weeks, while the cost is
very little more than that of the paper and silver. There is this dif-
ference, however: much of the ready sensitised paper sold does not
give satisfactory prints. To sensitise albumenised paper, it should be
floated on a bath of silver containing from 50 to 60 grains of the nitrate
to each ounce of water, and be left in the solution about three minutes.
Whether large or small pieces of paper be used, the sheets should be
held by two opposite corners, so that the middle of the sheet shall just
touch the solution, and then be gradually lowered. When the paper
is in contact with the fluid, it should be raised to see that no air-
bubbles have formed. The sheet, after three minutes, may be slowly
raised to allow the silver to run off, and, after draining, may be sus-
pended from a line to dry, being held by wooden clips and a strip of
blotting-paper attached to the lowest corner. Sometimes the paper is
drawn over the edge of the dish or a glass rod to assist in the removal
of the surplus silver solution. As already stated, paper freshly prepared
should be used at once, as in a few hours it is liable to turn brown,
when it becomes useless if clean whites are to be preserved. The
manipulations in the subsequent processes are the same, whether the
paper is newly prepared or ready sensitised.
The method of printing needs very little description, as practice
will quickly show what is required. Whether the printing should
be deeper than the finished print is intended to be, depends very
much on the kind of toning bath to be used. The progress of the
printing should be carefully watched by lifting one side of the back
of the printing-frame, which is hinged for the purpose. In the case of
freshly-prepared paper, the toning and fixing must be done at once-
that is, the same day; but with the other kind, the toning may be
deferred. In either case, the prints must be placed in water to
remove the excess of silver chloride, and the toning is necessary to
PROCESSES.
177
alter the colour of the print, which would be of an unpleasing red
colour unless altered by the gold used in toning; this changes the red
to any tint of brown approaching purple and purple-black which may
be desired. The prints are first put into plain water; after a few
minutes' soaking, the water is poured into a jar kept for the purpose,
and the dish again filled with water. Or two dishes may be used, and
the prints changed from one to the other. The first washing water is
kept for the purpose of saving the silver, which, in case of paper freshly
prepared, soon accumulates when much paper is used. Ready sensi-
tised paper is not so rich in silver, but still the first washing water
should not be thrown away. (The chloride is thrown down by adding
hydrochloric acid or common salt, and the water can be poured off as
soon as it becomes clear.)
The toning solution is made as follows:-Take a tube containing
15 grains of gold chloride; break the glass, and put it with its con-
tents into a bottle containing 1 drachm of water for each grain of
gold. Put as much water as will be required in toning the prints.
into a dish, and add 1 drachm of the gold solution to each 8 ounces
of water (each whole sheet of paper will require about 1 grain of
gold to tone it). This solution must now be made alkaline by placing
in it a lump of common washing-soda (sodium carbonate), as also a
small piece of red litmus paper; move the soda about in the water
until the paper turns blue; the solution is then ready for toning. By
noticing the sensation between the thumb and fingers—a kind of soapy
feeling the proper state of the solution may in future be determined
without the use of test paper. Place the prints, a few at a time, in
the toning bath, keeping them in motion by turning them over, and
watch the effects of the gold. As soon as the colour desired is
reached, place the prints at once in a dish of water, and so proceed
until all are toned. There are two effects produced by toning,
one the change of colour, and the other the substitution of gold for
silver; or perhaps it is more correct to say that one is the effect of
the other. Much has been written on this subject, and it is perhaps
safe to say that what takes place in toning is not certainly known.
Instead of saying that gold is "substituted" for the silver, it would
be more correct to say that a kind of “ gilding" is effected. The
silver is not removed from the paper by the gold, but a change has
been effected. When thoroughly done, there is no doubt that the
print is more permanent when toned, and is certainly more pleasing
in colour. It has been stated that untoned prints are unstable; but
the very earliest prints were not toned, such as those made by Mr.
Talbot in 1844, some of which are apparently in the same state as
when first printed, but have, however, the red colour; this shows
that untoned prints do not necessarily fade.
M
178
MANUAL OF PHOTOGRAPHY,
Some authorities say that a toning bath should be neutral. This
is correct when chalk forms part of the formula, but the alkaline
method of toning is more generally practised; the results are about
equal in each case. The formula with sodium carbonate, already
described, gives very satisfactory results; and, although it is generally
stated that it will not keep, the writer finds that, with the addition
of gold as required, the solution need not be renewed until it has been
used several times. The old bath should not be thrown away, but
the solution should be poured into a vessel and sufficient iron proto-
sulphate added to precipitate the gold which it may contain.
The acetate toning bath is preferred by some printers, and is formed
as under:
Gold chloride
Sodium acetate
Water
I grain.
20 grains.
IO Ounces.
Make up much more of the solution than will be required for toning
a few prints. The soda must first be dissolved in the water and the
gold then poured in. The strength of the bath must be kept up by
the addition of one grain of gold—that is, one drachm of the normal
gold solution for each sheet of paper to be toned.
The following gives good results. The bath will keep and remain.
in good condition when replenished with gold as required :-
Gold chloride
Calcium chloride .
Chalk (powdered)
Water
a
2 grains.
2
""
I teaspoonful.
16 ounces.
The bath should be mixed some hours before it is to be used.
Platinum may be used for toning in the place of gold. Take-
Platinum perchloride
Water
•
I grain.
16 ounces.
Neutralise with potassium carbonate and then add half a drachm of
formic acid. This is recommended for toning plain paper prints.
Prints on this kind of paper and suitably toned have very much the
appearance of those made by the platinotype method.
A very large number of formulæ have been published for toning,
but for all ordinary purposes the selection given here will be found to
be sufficient.
In
Toning takes place slowly when the solutions are cold; therefore,
in the cold season of the year the solution should be warmed.
the summer this is not necessary.
Too many prints should not be placed in the toning solution at one.
PROCESSES.
179
time; and, as the toning is completed, each print should be placed in
a dish of water to stop the further action of the gold.
It is quite immaterial what formula be used if the prints are from
weak negatives. The vast majority of negatives now produced are too
thin, consequently weak prints are the result, which no system of
toning will make worth looking at. A good negative by the collodion
process has sufficient density to enable vigorous prints to be made.
When toned, more gold is taken up, so that there is altogether a
brighter character about such prints which none but the very best gela-
tine negatives will equal. If prints made from negatives by the collo-
dion and gelatine processes are made on the same kind of paper, and are
treated in every way the same, the prints from the gelatine negative
may appear to the ordinary observer to be equal to those from the
collodion negative; but any skilled person could detect the difference.
It is generally believed that the cause of the want of stability in
prints made during the last few years arises from the want of density
in the modern negatives; and, as the printing cannot be carried to
the same depth, the toning action of the gold is not so effective; hence
the fugitive character of the prints.
When the whole of the prints are toned, they may be placed at once
in the fixing solution, formed of—
Sodium thiosulphate ("hypo ").
Water
4 ounces.
20 55
If the thiosulphate solution should be at all acid, a small quantity of
liquor ammonia may be added. The prints must be kept in the
solution at least ten minutes, and should be kept in constant motion,
to ensure every part being acted on by the fixing agent. The prints
may be examined by transmitted light. If they are not completely
fixed, patches darker than the rest of the paper will be seen, and the
fixing must be continued until this disappears.
Some kinds of paper are liable to blister, the albumen rising some-
times in patches as large as a shilling, while at other times the paper
is covered all over with small blisters, which usually disappear in
drying; but the larger ones seldom dry flat and therefore spoil the
print. To prevent blistering, the addition of salt to the first washing
water is recommended, and ammonia in the fixing bath is also sup-
posed to remedy the evil. It cannot be said, however, that either is
wholly effectual, as the blisters sometimes appear although the sup-
posed remedies have been applied. Changing from warm to cold
solutions is also said to conduce to blistering.
After the prints have been passed through the salt and water they
must be placed in a clean dish with water, and changed frequently
during the first few minutes. They may then be left for a time, the
180
MANUAL OF PHOTOGRAPHY,
water being changed at intervals, and then left all night, and changed
again two or three times before they are taken out to be dried. It is
sometimes recommended that the last washing water should be warm,
to remove the least trace of the sodium thiosulphate.
It may be noticed here that every care should be taken to have the
dishes quite clean. The most effectual way to clean them is first to
wash them with water, and then to rub them thoroughly with common
salt, using it as if it were damp sand; when thoroughly rubbed in
this way, inside and out, the dish is made quite clean. This should
be done every time before use.
When large numbers of prints are dealt with, it becomes worth
while to preserve the fixing solution to recover the silver. When a
convenient vessel can be placed in the open air, the solution, after
each day's fixing, should be thrown into it, and potassium sulphide
(liver of sulphur) added in solution. As the vessel becomes filled a
tap placed 4 inches above the bottom can be opened to draw off all
the top part, and the vessel can then be filled again.
It should be stated that the fixing solution should never be used
a second time. Some writers recommend that two baths (that is, two
applications of the "hypo") be used to ensure perfect fixing of the
prints.
Blisters.-It frequently happens when prints on albumenised paper
are removed from the fixing solution into the dish or trough for
washing, that blisters appear, in some cases small and covering the
whole surface of the paper, or the blisters may be large and few in
number. Many opinions have been formed as to the cause of this
troublesome defect; the true explanation probably is that the albu-
men has not been perfectly coagulated. The suggested remedies are
numerous. To prevent the formation of the blisters the addition of
a strong solution of sodium chloride to the washing water may be
tried. The change from the fixing solution to the washing water
should be gradual, as the differing densities of the fluids appear to
influence the formation of the blisters. Steeping in methylated spirit
to coagulate the albumen before the prints are washed is one of the
remedies, and also the immersion in boiling water, as suggested by
Mr. A. W. Clarke in the St. Louis Photographer, to effect the same
purpose. The hot water, however, would probably take out the size,
thus rendering the paper very tender and difficult to handle. When
the blisters are small, they generally disappear on drying; but when
large, by puncturing the paper on the back of the blister the film may
dry flat, but it often occurs that large blisters entirely spoil the print.
Fading. One of the most serious defects in photographic printing
is that, however perfect and beautiful a print may be, there is no cer-
tainty that it will remain so for any length of time.
There are many
PROCESSES.
181
prints in existence which are in the same state as when first pro-
duced. As already stated, the writer has in his possession prints made
by Mr. Fox Talbot in 1844; some of these are evidently unchanged,
excepting at the edges where the prints have been mounted. At the
date named, toning with gold had not been brought into use, so that
the prints retain the reddish-brown colour common to all untoned pho-
tographs on plain salted paper. The use of albumen, because it has a
trace of ammonia in its composition, is said to be one cause of fading;
but prints on albumenised paper and toned with gold exist which
show no sign of deterioration, although thirty or forty years may have
elapsed since they were made. It would seem, therefore, that there
is no reason why silver prints should not be permanent; and, although
some of the causes of fading are not known, it is quite certain that no
reliance can be placed on silver prints unless certain precautions are
taken in their production. Chief amongst these precautions are the
importance of using fresh sodium thiosulphate solution for fixing, and
thorough washing.
One reason why early photographs are apparently more permanent
than those done recently is that the negatives in use were stronger,
consequently, the printing was deeper; and for such printing a larger
proportion of silver was used in preparing the paper.
The very old photographs by Talbot were mounted only by the
edges—that is, they were touched with the mountant (probably gum
arabic, not freshly made) around the margin for about a quarter of an
inch; and it is only this part which has failed. This is clear evidence
that when prints are made to adhere entirely there is greater chance
of fading, and it shows also that the mounting material should be of
a kind which could have no chemical effect on the print.
It is a fact which should be carefully noted, that paper negatives.
made nearly fifty years ago have not changed. Such negatives were
developed; and it is generally believed that developed prints are more
permanent than any others.
On the point of permanence of silver prints the following remarks
of Mr. M. Carey Lea should be remembered :—
"The conclusion to be drawn from all this is simple enough. Silver
prints can be made to be perfectly permanent, if the use of hypo-
sulphite be liberal and judicious, and by throwing away every bath
that has stood even for an hour or two after the prints were first
placed in it. It may be said without exaggeration that every penny
saved in hyposulphite costs the loss of dozens of prints by fading.
“Of course, nothing can take the place of good washing. By this
is to be understood, not exaggerated soaking in water, but lying for
some hours in water which is continually changing. No system of
washing can be considered effectual which does not alternately fill and
182
MANUAL OF PHOTOGRAPHY.
empty the washing vessel, so that the fresh supplies of water are not
contaminated by mixing with the previous portions."
Fuming Albumenised Paper.—It is claimed that albumenised paper,
if exposed to the fumes of ammonia, gives more brilliant prints, and
that the toning is more easily effected. When large quantities of
paper are to be manipulated, a suitable cupboard or box should be
used; but on a small scale, a less elaborate method may be adopted.
Take a box, such as drapers use, made of cardboard, eighteen inches
square, larger or smaller according to the size of paper to be dealt
with. Spread on the bottom a sheet or two of blotting-paper, and
over this some tissue-paper crumpled so as to rest lightly on the
blotting-paper; but, before putting in the tissue-paper, sprinkle a
drachm or two of liquor ammonia, which may be diluted with one half
water, on to the blotting-paper; the paper to be fumed may rest on
the tissue-paper for ten or fifteen minutes. If preferred, muslin may
be strained across the box, over, but not touching, the blotting-paper,
and the paper to be fumed may rest on the muslin. The printing
and toning are conducted in the usual way.
Plain or Salted Paper, Printing on.-The change of taste during
the last two or three years has brought again into notice the very
earliest kind of printing-that on the plain salted and unglazed
paper. There can be no doubt that the detail in a photograph is
made more apparent when it is kept on the surface by albumen or
other means than when the matt surface of the paper is used. This
perfection of detail is made more prominent when aristotype and
other kinds of paper are used, while enamelling has much the same
effect. A photograph treated in this way has an exquisite beauty of
its own, and it can be seen in no other way; but there can be no
doubt that, from an artistic point of view, a print without the very
high glaze is better; this kind of effect may be obtained by using
paper of fine quality, salted and sensitised in the usual way. The
best toning bath for this kind of paper is the one containing platinum.
Prints of this kind are very suitable for painting in water-colours,
and they should be kept light for this purpose. With care in hand-
ling, Whatman's drawing-paper may be salted and treated in the same
way as other papers; and, for the artist in water-colours, this is
perhaps better than any other kind, at least for large work. As the
paper when wet is heavy, great care must be taken in handling, as
it will scarcely bear its own weight. This kind cannot be purchased.
ready prepared, and must be salted and sensitised as required. Take-
Ammonium chloride
Water
Gelatine (if the paper is not well sized)
8 grains.
I ounce.
2 grains.
PROCESSES.
183
Pin the paper to a board, and with a piece of lint brush over the
paper in all directions until completely covered, and then allow to dry.
Then take-
Silver nitrate
Water
60 grains
I ounce.
and brush over the paper as in salting. See that this is thoroughly
done, or the printing will not be even. All the subsequent processes
are the same as in ordinary silver printing.
In 1855 Mr. Sutton introduced a process for producing prints on
plain paper in which the serum of milk was used instead of a salt, and
the prints were developed. The process was new, and at the time
attracted considerable attention. A print in the writer's possession,
prepared by this process, and issued from St. Brelade's Bay, Jersey,
where Mr. Sutton at that time resided, is in fair condition, and appa-
rently not much altered. It is some proof that the claim for the pro-
cess that the prints were permanent is to a large extent justified. At
the time referred to the toning and fixing were effected at one opera-
tion, and it was to remove the possible cause of fading due to this
method that Sutton's process was introduced. (See Aristotype; also
Gelatine Chloride Paper, Ilford).
Printing on Ivory.-As a surface for the artist to paint upon in
water-colours, ivory has always had the preference; but miniature.
painting was almost a lost art for many years, owing to the great
popularity of photography; the daguerreotype plate took the place
of the ivory miniature for brooches and lockets; then the glass posi-
tive, which was superseded by the portrait on paper, treated usually
in a very inartistic way, and by hands much less competent than the
old miniature painters. To print a photograph on ivory was difficult;
but a process was introduced by Mr. Beard, the patentee under
Daguerre of the daguerreotype process in England, which gave very
good results.
The ivory was salted with calcium chloride, the silver
nitrate was dissolved in alcohol, and the picture was fixed with
potassium sulpho-cyanide. The method is somewhat uncertain, but
time has proved that the prints do not fade. The true surface of the
ivory in this process is used, which is not the case when a film of
gelatine is made to cover it, as in the carbon process; but, as the
film is thin and transparent, in the hands of a skilled artist a good
carbon print on ivory has all the appearance of a real ivory miniature,
with the advantage of the correct drawing which the photographic
basis gives.
Reproduced Negatives.-It frequently occurs that more than one
negative is required of the same subject. When they cannot be ob-
tained direct from the object, recourse must be had to some method by
184
MANUAL OF PHOTOGRAPHY.
which the original negative may be reproduced. The simplest way of
course is to copy a print, but the effect in this case is far from perfect,
owing to the texture of the paper showing. A transparency may be
printed of the same size, and from this again a negative. In this case
care only is required, and excellent reproductions of the original may
be obtained.
Reversal of the Image.-There are several methods by which the
picture may be developed as a positive instead of a negative—that is,
a positive as seen by transmitted light. An ordinary gelatine dry plate,
if much over-exposed when developed, will yield a positive image. By
recent experiments by Mr. A. P. Okell and others, it has been shown that
when the exposure has been more than sufficient to produce a positive,
a negative result may be obtained, and that the change from positive
to negative recurs in successive order. These experiments were con-
ducted with much care, and the exposures varied from a few seconds to
many hours. For some purposes a process by which a positive picture
could be produced with the same certainty as a negative would be
useful, and from experiments recently conducted by Colonel Water-
house, some success in this direction appears to have been attained.
It is found that when a small quantity of phenyl-thio-carbamide or
allyl-thio-carbamide (substances which are produced by treating mus-
tard-oil or thio-carbamide with ammonia) is added to the eikonogen
developer, and used for developing gelatino-bromide plates, if the
exposure has been correctly timed the result will be a positive picture.
So far as experiments have yet shown, the best results are obtained with
eikonogen, and Colonel Waterhouse gives the following formula :-
A. Eikonogen
•
Sodium sulphite
Water
•
B. Sodium carbonate, crystals.
Water
C. Phenyl-thio-carbamide
Water
5 parts.
ΙΟ ""
100
4
""
??
•
100
""
I
2000
•
The developer is formed by taking one part of A., two parts of B.,
one part of C., to which is added half to one part of a 10 per cent.
solution of potassium bromide, and, if the contrasts are too strong, a
few drops of ammonia. Colonel Waterhouse states that satisfactory
results may be obtained when suitable plates are used, quite equal to
those made by the old method in the camera—that is, making a positive
from a negative. Other forms of carbamide, such as thio-sinamine,
thio-carbamide, or sulph-urea, have been used.
Colonel Waterhouse also states that although there are some diffi-
culties in working by this new method, it is probable that satisfactory
positives will be obtained; that is, this process of making positives will
PROCESSES.
185
be as certain as the making of negatives in the usual way, and will be of
much value in making copies for working the photo-mechanical pro-
The process is quite new, and opens a field for interesting
cesses.
research.1
The reversal of the photographic image is a matter which, from the
first discovery of the art, has occupied the attention of many minds,
and under the term Solarisation these effects are generally alluded to.
The result sometimes seen when photographing an interior, where
there is a window through which a landscape may be visible, the
interior being a negative, and the exterior by the reversing action of
the light becoming a positive, is an illustration of this effect.
A reversal of the image obtained direct in the camera may be made
by immersing the developed picture on collodion emulsion in nitric
acid, when the reduced silver will be dissolved, leaving an image in
silver bromide. This is exposed to light for a short time and the
plate is redeveloped; or animonium sulphide may be used, when the
result will be a positive picture. Another method by Mr. Brooks may
be given. A gelatine plate is developed until the image is seen on
the back. It is then placed in the following solution :-
Potassium iodide
Potassium bromide
Water
•
I to 2 parts.
ΙΟ
100 ""
The plate is washed and then redeveloped with pyrogallic acid or ferrous
oxalate, and fixed in the usual way. (See Reverse Action of Light.)
Reversed Negatives.-There are several methods by which the
negative picture may be reversed, and for certain of the photo-
mechanical processes it is necessary that the image be in the reversed
position either on glass or on a film. The methods may be treated
in the following order :-(1.) By a prism of solid glass ground true
and fitted to the hood of the lens, so that when the camera is placed
at right angles to the object to be copied, the image is reflected on to
the plate in a reversed position. (2.) As the solid prism is costly,
a prism of patent plate-glass may be formed thus-A.
Make a
drawing of the size of the prism required, and then cut pieces of
glass carefully selected and free from defects; take two pieces of thin
metal with the edges turned up, and made to fit the glass as a top
1 Since this was written a letter from Colonel Waterhouse has been published
in the British Journal of Photography of January 30, 1891, in which he states
that "the tetra-thio-carbamide ammonium bromide compound salt, prepared as
described in Professor Reynolds' paper, gives under favourable conditions exceed-
ingly good reversals, much better than the thio-carbamide does itself. I found
five drops of the saturated alcoholic solution to the ounce of eikonogen developer
answer well for line-work, but have yet to make further trial. I find that the
nitric acid treatment is beneficial with this salt also in the case of line-work."
186
MANUAL OF PHOTOGRAPHY.
and bottom. The glass must now be cemented with marine glue (or
in any other way), so as to be water-tight. Through an opening at
the top, water (or castor-oil) may be introduced. This prism, although
not so perfect as the one made of solid glass, will answer the same
purpose at a very trifling cost. It may be fitted in front of the lens.
(3.) A piece of glass silvered at the back in the usual way may be
used, but the reflection is not perfect. If silvered on the face, a
mirror of silvered glass ground quite true and polished answers very
well, although there is some loss of light, and great care must be
taken that the surface is not injured; it must never be exposed
excepting while in use, or the surface will become tarnished. For
the method of silvering see Silvering Glass, page 189. (4.) The nega-
tive may be reversed by placing the film so that the image is formed
through the glass. If made on a wet plate, the plain side of the
glass must be wiped dry; and if a dry plate be used, it must be
carefully cleaned. It must be noticed that reversing the plate.
makes it necessary either to reverse the ground-glass while focus-
sing, or to allow for the thickness of the plate. (5.) The film
may be reversed by stripping; if a wet collodion plate be used,
proceed as follows:-Paste strips of paper around the edges on
the back of the plate, so that when dry they may be turned up to
form a kind of dish. Then take gelatine 2 ounces, loaf-sugar 1
ounces (or a small quantity of glycerine instead of the sugar, either
being used to make the stripped film flexible), and water 2 ounces;
dissolve in the usual way, and filter through muslin. Place the
negative on a sheet of plate-glass on a levelling stand, and pour on
sufficient of the gelatine solution to completely cover it.
When set,
the negative may be stood on edge to dry; and when quite dry, by
running a knife around the edge the film may be stripped. The
glass should be rubbed over with French chalk before coating and
sensitising. (6.) Unvarnished gelatine negatives may be stripped as
follows:-Place the negative on a levelling stand and cover it with
transfer collodion. When this has set, the negative must be put into
a dish of water and washed till all greasiness disappears. Into an
ebonite tray pour a solution of hydrofluoric acid (one drachm of the
acid to two ounces of water) and then place the negative in it. The
film will soon show signs of leaving the glass; at this point remove
it from the acid and wash carefully, then put it face upwards on
blotting-paper, and on the film put a piece of smooth paper, wetted
and larger than the glass, pressing it in contact with a squeegee. On
turning the plate over, the film may now be removed with the paper.
Then place in water, when the negative will float off, and may be
caught in its proper position on a clean glass. It is then allowed to
dry, or it may be transferred to a plate prepared with gelatine in the
PROCESSES.
187
usual way. (7.) India-rubber dissolved in benzole may be poured on
to the dry collodion film (the negative being taken on a plate which
has been rubbed over with French chalk and then coated with trans-
fer collodion). When quite dry, the film may be stripped as before
described. With care, any one of the methods given above will be
found quite effectual.
""
Retouching. The "art" of retouching a photograph may be com-
pared with what is called "flattering" a portrait painted in oil or
water-colours, or it may be as monochrome—that is, endeavouring to
make the portrait different from, if not better than, Nature made the
subject. There was a time when a photograph was considered to be
something to "swear by "-that is, a truthful representation, and not
a thing which had been altered by hand to meet the idea of the
"retoucher as to what Nature ought to have made the subject. This
retouching, however, is now carried to such perfection (?) that it is
no longer safe to "swear by " the thing which the light, in the first
instance, had made almost the exact resemblance of the image it had
impressed on the sensitive plate, but which the lead-pencil in the
retoucher's hand has altered to such an extent that it no longer can
claim to be a true image of the original. Retouching-that is, working
upon the negative with lead-pencil to remove photograpic defects-
may be allowed. It is no fault of the sitter if Nature has endowed him.
with a skin covered with minute yellow spots or "freckles;" these
appear on the sensitive plate in such a manner that the result
when printed is to show them too prominently. They may be scarcely
visible to an ordinary observer on the face of the sitter, but they are
very noticeable in the photograph, and are very objectionable. To
remove these, but at the same time not to alter the likeness, is per-
fectly legitimate. The use of orthochromatic plates assists the photo-
grapher here, but is not altogether sufficient. It is not possible in
a page or two to say all that might be desirable on this subject.
Treatises devoted to the subject have been written in which minute
directions what to do in all cases are given, and to which the reader
is referred. The writer admits that retouching is necessary, but the
experience of many years confirms him in the opinion that, beyond
what has been said above, and the general smoothing away of defects,
retouching as now practised is not legitimate. Excessive retouching
is practised chiefly because people "will have it." But it is in the
power of the photographer to a large extent to guide the public.
taste. It is the abuse of the "art," and not the use which should be
condemned. That public taste may be led is manifested in the prefer-
ence which is beginning to be shown for prints without the glaze of albu-
menised paper, platinum and bromide printing largely taking its place.
What can be said in defence of remarks of this kind, which
188
MANUAL OF PHOTOGRAPHY.
appear in one of the most influential of the photographic journals?
"To the most casual of observers the nose will always appear a
leading, if not absolutely the most prominent feature of the face;
and, indeed, the success of the portrait will depend very materially
upon the degree of success with which we treat it. Many times the
retoucher will be called upon to give absolute form to the nose, and this,
it is needless to say, will often tax his ability to the fullest." Very full
instructions are given as to the treatment of this very important
feature in the face, showing how the bridge may be improved and
altered so as to make it what the retoucher considers it ought to be ;
other parts of the nose and other features of the face are directed to
be modified; the eye even does not escape attention. It is fair to say
that the author of these instructions concludes one of his papers with
these remarks :—“ Over-work, in the treatment of a negative, will only
produce a hard, wooden effect, and in nine cases out of every ten falsify
the natural expression and ruin the resemblance. Needless to say,
retouching carried out on the over-work principle can have no preten-
sions whatever to the artistic." This is perfectly true, and it is true
also that retouching carried to the extent recommended must result
in injury to the portrait. In many cases the face is covered with
retouching to such an extent that the result in a print is the appear-
ance of the sitter having recently recovered from small-pox.
It has been admitted that a certain amount of retouching in most
portraits is necessary, and, provided it is not carried so far as to
detract in any way from the picture as a portrait, the work may be
improved; but this is only necessary because prints on paper from
untouched negatives are not so perfect as portraits by other processes
were in former times. Bad negatives are allowed to pass because
the retoucher is supposed to make good the defects left by the
photographer.
For the purpose of retouching a portrait or other negative, hard lead-
pencils are used. Faber's HH, HHHH, and even six H are em-
ployed. The lead must be cut to a very fine point, and the point
kept by rubbing on a piece of fine emery paper. The negative must
be placed so that the light may be reflected through it-a retouching
desk is generally used. To obtain the best effect in the negative, the
head of the retoucher should be protected from the surrounding light
as much as possible. The negative is usually worked upon before it
is varnished; and, to make the pencil "bite," the gelatine film is
sometimes slightly roughened with fine pumice or cuttlefish powder.
In other cases the plate may be coated with varnish, which leaves
a "tooth." Suitable varnishes may be purchased. Success or other-
wise will depend upon the skill of the retoucher, and the " can
only be acquired by practice. From what has been said, it is clear that
art

OF
NIV
CH.
MIC²
M. WOLFE.
DAYTON, O., U. S. A.
ZINC ETCHING
MADE WITH
M. WOLFE'S FINE LINE SCREEN PLATES AND HALF-TONE PROCESS.
PROCESSES.
189
the writer would advise that as little as possible should be done with
the pencil. The aim of the photographer should be to make his
negative as perfect in light and shade as possible. Consequently, if
modelling and all other technical details have been carefully attended
to, very little need should arise for the so-called retoucher's "art."
The art should be in the photographer, and the less aid he requires
from the lead-pencil the better his work will be.
Ruby Medium.—When it is not possible to obtain ruby glass, it is
convenient to have the means of preparing a transparent sheet as a
substitute. Mr. W. K. Burton recommends the following :—
A. Gelatine
Water.
Potassium bichromate
B. Silver nitrate
Water.
·
100 grains.
4 ounces.
20 grains.
20
I ounce.
The gelatine must be softened in the usual way; then add the
bichromate, and apply heat until the whole is dissolved. Solution B.
must then be added. Coat the glass with the emulsion, and the result
will be a film of a deep ruby colour.
Screen Plates.--On page 143 will be found a description of one of
the methods for obtaining a lined screen to be used in making half-
tone zinc blocks. Since that description was written, the writer has
seen a screen made by Mr. M. Wolfe of Dayton, Ohio. The ruled
surface is sealed between two glass plates, and is therefore not liable
to injury from scratches, or by the silver solution coming in contact
with it. The accompanying illustration is the result of Mr. Wolfe's
skill in preparing the block, as also the ruled screen.
Silvering Glass.—The following solutions are necessary for silver-
ing glass by the Brashear method :—
Loaf-sugar
Distilled water (to dissolve the sugar)
Nitric acid
Alcohol
•
Distilled water to make
840 grains.
300
39
25 drachms.
26 ounces.
The glass, if to be used as a reversing mirror, must have a perfectly
true surface (ordinary patent plate is not sufficiently perfect), and
must be chemically clean. On the back must be cemented with
pitch a couple of corks, by which the glass may be held level and in
contact with the silver solution—
Silver nitrate .
dissolved in 2 ounces of distilled water.
50 grains
50 grains
Potassium oxide hydrate (caustic, pure by alcohol)
dissolved in 2 ounces of distilled water. Put a tenth part of the
silver solution into another bottle to be kept in reserve. Liquor
190
MANUAL OF PHOTOGRAPHY.
Add four
ammonia is added to the silver solution until the brown precipitate is
redissolved. The potassium solution is now to be added.
Add a
few more drops of ammonia, and leave the solution to precipitate.
The reserve solution of silver is now to be added carefully until the
solution becomes yellow-brown. Add sufficient distilled water to cover
the edge of the mirror when it is suspended in the fluid.
drachms of the reducing solution and stir well together. After the
mirror has been suspended in the solution about ten to thirty minutes,
according to the temperature of the room, the silverising will be com-
plete, and the mirror may be rested on blotting-paper to dry. When
perfectly dry, the surface may be polished with rouge in the usual
way. Success depends very much on the temperature of the room,
which should not be under 60° F., and the glass and solutions should
have been in that temperature at least twenty-four hours before the
silvering process was commenced.
Another method is recommended by Mr. Common. Three solutions
are used :-
A. Silver nitrate
Water (distilled)
B. Caustic potash (pure)
Water (distilled)
C. Glucose or grape-sugar
Water (distilled)
1 ounce.
IO ounces.
I ounce.
IO Ounces.
ounce.
10 ounces.
The quantities must be determined by the size of the glass to be
silvered. About 4 ounces would be sufficient for a mirror 10 × 8.
The silver is converted into ammonio-nitrate as previously de-
scribed, and the remaining operations are the same.
When not in use, the silvered mirror should be carefully wrapped
in chamois leather and enclosed in a box to exclude air as much as
possible, otherwise the surface will tarnish and necessitate repolish-
ing with rouge; but the frequent repetition of this will injure the
surface, and re-silvering will be necessary.
Stains. In the various manipulations, when the skin comes in
contact with silver and some other solutions, stains occur which are
unsightly and cause an unpleasant roughness. This kind of stain
may at once be removed by touching the parts with solution of
iodine, made by adding iodine to methylated alcohol, and then
rubbing with a piece of potassium cyanide; care, of course, being
taken that no part of the skin is cracked or cut. If the stains have
been caused merely in developing gelatine plates, a little of the
"clearing solution" will remove them to a large extent; or the parts
If
may be rubbed with pumice-stone when the hands are washed.
the stains are on linen (or the skin), the following has been recom-
mended :-
PROCESSES.
191
Iodine
Nitric acid
Hydrochloric acid
毋
​Alcohol (methylated)
I part.
I
I
20 parts.
Touch the stain with some of this solution, and afterwards with
"hypo" or potassium cyanide in solution, when the stain will dis-
appear. The linen or skin must then be well washed.
Potas-
Stains of any kind on negatives are difficult to remove.
sium cyanide solution may be rubbed on the part. Gelatine negatives
should never be printed from in damp weather, unless they have
been varnished, as they are otherwise very liable to be stained.
The best remedy for a stained paper print is to print another.
Stannotype.—Another of the clever inventions of the late Mr.
Woodbury was named by him Stannotype. The necessity for using
hydraulic pressure in making the printing-plates for the Woodbury
type process has always made that beautiful method less available
than it deserved to be. In the Stannotype process we are enabled to
prepare a plate by very simple means, which can be printed from in
the same manner as the Woodbury-type.
Stannotype (derived from the Latin stannum and Greek typeo)
is so called because tin is used in the form of tinfoil to receive the
impression. A carbon transparency is prepared, and this, when dry,
is used to obtain a negative intaglio image, which is then covered
with tinfoil as the printing-plate. For this intaglio plate a thick film
of gelatine must be used, which, when dry, is coated with tinfoil, or,
when large numbers are to be printed, with foil which has been
covered with a thin coat of steel. The intaglio negative, having been
developed on a sheet of plate-glass and dried, is now ready to be
coated with the foil, and this is done by rolling between two india-
rubber rollers. The plate is first put into position between the rollers,
and the pressure adjusted to the centre of the image on the plate,
and the rolling motion is given by moving the handle backwards and
forwards until the ends are reached. The plate between the rollers
will bear sufficient pressure to embed the foil in the gelatine negative.
The kind of press used for printing from the Stannotype mould or
plate is the same as for the Woodbury-type. The mould is placed on
the bed of the press upon a sheet of thick blotting-paper which has
been wetted. The top plate of the press has attached to its under
surface a sheet of glass perfectly flat, and this plate is movable when
the screws are loose. When the mould is in its place, the screws are
adjusted, so that when the arched bar is lifted the whole remains
rigid, and will always come into perfect contact with the mould when
taking the impression. All being ready, the surface of the mould is
oiled slightly with a mixture of equal parts of paraffin and olive oils.
192
MANUAL OF PHOTOGRAPHY.
The ink is composed of 4 ounces of gelatine to 24 to 30 ounces of
water, determined by the temperature, as the ink must be thicker in
warm weather. To the gelatine may be added Indian-ink or colour
of any kind. The ink is poured into a wine-bottle, which must stand
in a vessel holding water which can be maintained at a temperature of
125° to 130° F. In printing, a pool of the ink is poured from the bottle.
on to the mould, the paper placed in position on it, and the arch of the
press brought down and tightened by means of the handle. In a few
minutes the gelatine will have set, when the pressure can be released
and the paper lifted, on which will be found the picture. The sur-
plus ink pressed out at the sides of the mould can be scraped off and
re-melted for further use. In printing large numbers, it is usual to
have three presses in use; they are fixed to a revolving table, so that
as each press is used the table is turned; and when the third is filled,
the first print is ready to be removed.
Steel-Facing Copper-Plates.-As copper is usually employed for the
best half-tone blocks obtained by the aid of photography, it becomes
necessary to coat the surface with a hard metal, as the fine detail on
the copper is rapidly deteriorated by the cleaning process necessary in
printing. By the deposit of iron electrically the rapid wearing of the
plate is prevented; and as the iron will, if a large number of prints
are required, also wear, it is necessary to re-face the copper. The
colour of the surface will show when this becomes necessary.
"The copperplate to be re-faced first has all ink removed from its
surface by chloroform or turpentine, is then washed and carefully
dabbed over with a hog's-hair brush dipped in a potash lye or in a
5 per cent. solution of potassium cyanide, then washed again. The
plate is then laid into a flat bath, along the bottom of which a bare
copper wire is laid, which is to serve as the negative pole of the cur-
rent. The appropriate steel-depositing fluid is then added, so as to
avoid oxidation. A plate of pure steel serves as anode; it is placed
at the positive pole above the copper-plate when the current is opened.
A silvery-like film of steel is immediately deposited upon the copper-
plate. Air-bubbles are easily removed with a feather. The plate
should be completely steel-faced in about five minutes. The composi-
tion of the fluid used is as follows:-Dissolve in warm water 35 ounces-
Ammonium chloride
60 grammes - 2 ounces.
Crystallised ferric sulphate
Crystallised ammoniac ferrous sulphate
•
30
30 ""
= 1 ounce.
The solution should stand two days and be twice filtered, and
should be filtered again before each time of using. After the facing
is completed, the plate should be cleaned as before, and greased to
prevent it from rusting."1
1 British Journal Almanack, 1889, p. 606. ;
PROCESSES.
193
Stenochromy.—Under this name a method of applying colour to
photographs made by the Woodbury-type was introduced by Mr.
Ingerstein.
Tannin Process.-Amongst the variety of substances used for pre-
serving the sensitiveness of dry collodion plates, tannin was one of the
most popular, and was first successfully used by Colonel Russell. A
plate was coated with collodion and sensitised in the usual way, and
placed in a dish of distilled water for one minute, keeping the plate
in motion to remove greasiness; then it was well washed under a tap
for two minutes, giving it a final rinse with distilled water. A solu-
tion of tannin was now poured on to the plate, which must be on a
levelling stand, and the solution allowed to remain two or three
minutes. The plate was then allowed to stand on one corner in the
dark till dry. The plates required to be “backed" with some opaque
colour to prevent blurring, to which tannin plates were very liable.
A border of varnish was necessary to prevent the film loosening.
To develop, the plate was first covered with spirits of wine and
water in equal proportions, and then rinsed off with distilled water.
The developing solution was composed of-
1. Pyrogallic acid
Distilled water
2. Citric acid
Silver nitrate
•
Distilled water
3. Citric acid
•
Silver nitrate
Distilled water
2 grains.
I ounce.
IO grains.
IO
3?
I ounce.
40 grains.
ΙΟ
I ounce.
To sufficient of No. 1 to cover the plate was added one drop of No. 2
to each drachm of No. I. The plate was developed with this. If
the negative appeared quickly, it had been over-exposed, when the
developing solution was poured off, and the development continued
with distilled water in which a few drops of No. 3 were added. The
fixing was done in the usual way with "hypo." It was claimed for this
process that it was simpler, and that the results compared favourably
with other processes.
Taupenot Process (see Collodio-Albumen). One of the most
extensively used processes, prior to the advent of collodion and gela-
tine emulsions, was the Taupenot or Collodio-Albumen process. The
negatives produced by it were of the best quality, and the plates,
when carefully preserved, retained their sensitiveness for many years.
The plates, after very careful cleaning, were coated with weak albumen
solution. This substratum was for the purpose of keeping the col-
lodion from slipping, and preventing blisters in the subsequent parts
of the process. The albumenised plate, when dry, was coated with
N
194
MANUAL OF PHOTOGRAPHY.
collodion (old was preferred), sensitised in an acid silver solution,
and then thoroughly washed. The next coating consisted of iodised
albumen made as under :-
Albumen
Potassium iodide
Potassium bromide
Ammonia
Water
8 ounces.
50 grains.
ΙΟ
2 drachms.
2 ounces.
After these are well beaten together, and after the solution had
settled, the plates were coated twice, a great quantity of the solution
being used each time; the first may be thrown away, and the second
used for the first coating of the next plate. At this stage it was
dried. The plates were made sensitive by immersion in the following
bath :-
Silver nitrate
Glacial acetic acid
Distilled water.
About one minute in this bath was sufficient.
30 grains.
drachm.
I ounce,
A thorough washing
under a tap was now given, and a final rinse with distilled water.
The plates when dry were ready for use. The plates were usually
developed with pyrogallic acid, three grains to the ounce of water,
and when the details of the picture were well seen, the full printing
density was obtained by redeveloping with-
Pyrogallic acid
Citric acid
Water
·
2 grains
grain
I ounce
to which three or four drops of a thirty-grain solution of silver nitrate
were added. Any deposit which might be formed in developing was
removed with a tuft of cotton-wool. 'Hypo" of the usual strength
was used for fixing.
(C
The process was modified in many different ways. The prolonged
exposure necessary was the chief objection to the process.
Tea Process.—In this process an infusion of black tea (10 ounces
of boiling water to half an ounce of tea) was used as a preparation to
preserve collodion plates in the dry state when only required to be
kept a few days.
Telescopic Photography.-Any telescope may be arranged horizon
tally, so that the ground-glass of an ordinary camera may be made
to receive the image of the distant object through an eye-piece. The
writer used a Barlow's lens for this purpose about thirty years since, and
obtained photographs about twice the diameter of the image as seen
at the principal focus of the object-glass. An instrument called a
PROCESSES.
195
Photo-heliograph has for many years been used at Kew for photo-
graphing sun-spots. Practically this is a telescope to which an
enlarging lens has been added; such instruments were made by the
late Mr. J. H. Dallmeyer, having the chemical and visual foci coinci-
dent. It appears from a recent discussion of the subject that as early
as 1869 Dr. Hugo Schroeder constructed refracting telescopes with
an arrangement of lenses suitable for photographing distant terrestrial
objects. Mr. T. R. Dallmeyer has also constructed an instrument
with which an object may be enlarged about four diameters, as will
be seen by comparing Figs. 39A and 39B, the larger one having been
taken with a telescope. The value of such an instrument when used
for photographing the moon will at once be seen; and for some pur-
poses, when distant terrestrial objects cannot be photographed in the
ordinary way, the use of the new telescopic photographic lens will
be valuable.
In his recent work, "The Optics of Photography," Mr. J. Traill
Taylor states that in 1870 he showed how a telescopic view of a
distant object could be obtained, and he also says that he had long
since used one of the barrels of an ordinary opera-glass with the large
lens towards the object for obtaining enlarged views telescopically.
The following is an abridged description of a teleo-photographic
lens recently introduced by Mr. T. R. Dallmeyer. Mr. Dallmeyer
says:-
"Hitherto only two methods of producing large images had been
employed-first, the use of very long focus positive ordinary lenses;
and second, the production of a primary image by one positive lens,
and placing a secondary magnifier or second positive lens behind the
plane of the primary image, which enlarges it more or less, according
to its focal length, and its adjustment between the positions of the
planes of the primary image and that of the focussing screen, as in
the photo-heliograph, &c.
"The first of the older methods had been seldom employed except
in astronomical photography, on account of its unwieldy dimensions;
and the second method referred to is practically useless for ordinary
photographic work on account of the great loss of light involved,
rendering the length of time necessary for proper exposure so great as
to cause it to be almost prohibitive, except in the case of inanimate
objects."
The diagrams in Fig. 38 sufficiently explain the construction of the
new lens.
The introduction of an instrument of this kind will add very much
to the interest of the possessors of telescopes, who are at the same
time photographers, in the prosecution of their work. Photographing
celestial or terrestrial objects through small telescopes necessitated a
196
MANUAL OF PHOTOGRAPHY.

1
A
A¹
Fig. 1.
P
pr
Parallel ray
A
B
F
FA
A¹
A
Parallel ray to As
Parallel ray to A
Ray from new
EA
object
nee?
Ray from a
Go AI
object
-
Fig. II.
Fig. II.
B
P
divergent
F
N.
P
A
B
F
Imaginary position of A
FIG. 38.
FIG. I.-The upper back ray meets the lens, A, parallel to the axis, and by a proper adjustment between A and B, comes to
focus at F upon the plate PL. If PL be removed farther from the lens, B, to take the position P¹L¹, the lens A will have to be
moved slightly nearer to B, and take the position A¹.
FIG. II. On the upper side of the axis a parallel ray to A finds its focus as in the dark line on the plate at F. If, however,
some ray from a near object falls upon the lens, A, in the direction of the dotted line, after passing through the lens, B, is found
divergent, and no positive focus is obtainable.
FIG. III. represents a beam of rays passing through the two component elements, A and B, coming to focus upon the plate
PL. To estimate the rapidity, it is necessary to consider the full aperture placed at the principal focal plane passing through the
nodal point at N. A is thus made to take up an imaginary position. The position of the nodal changes for different positions of
the plate PL.


PROCESSES.
197
cumbrous addition to the instrument, while with the compact arrange-
ment now available the work will be both convenient and useful.
Transferotype Process.-Paper prepared on one side with soluble
gelatine, and then with sensitised gelatine emulsion, is supplied by
the Eastman Company. The paper is printed upon in the usual way
by artificial light, and is then developed with iron oxalate and fixed;

.S.H.
ام
FIG. 39A.
1

FIG. 39B.
FIG. 39A.-Shows view of a church about half a mile distant, taken with the
new lens.
Exact size of image on plate.
FIG. 39B.-The same object taken from the same point with a 10 by 8 R. R.
(13-inches equivalent focus). Exact size of image on plate.
and, after washing, is placed on the support where it is to remain,
and squeegeed. Water sufficiently hot to melt the gelatine next the
paper is then poured on, and the paper, when loosened, can be
removed.
Typogravure. The illustration facing page 198 is copied from an
oil-painting. The writer is not in possession of the details of the
special mode of preparation; but a careful inspection will show that
198
MANUAL OF PHOTOGRAPHY.
it is a combination of the half-tone zinc etching process and the
engraver's art. The plate is a very beautiful production, and shows
the invaluable aid of photography in the arts of mechanical reproduc-
tion of pictures. It is the work of Messrs. Goupil & Co.
Uranium Printing, &c.-In photography uranium is chiefly used
in the form of nitrate, which is obtained from pitch-blende dissolved in
nitric acid, dried, and again dissolved in water. Yellow crystals are
formed from the concentrated solution; these may be further purified
by solution in ether and recrystallisation. The crystals are very
deliquescent.
Many attempts have been made to utilise uranium for printing, but
the results have not been equal to platinum, and the prints will not
stand the same tests as the last-named metal. Paper is first floated
on a solution of—
Uranium nitrate
Water
I ounce.
5 ounces.
Expose in sunlight until a faint image is visible, and then develop by
floating on a solution of—
Silver nitrate
Water
I ounce.
20 ounces.
To which add a few drops of acetic acid. Fix with sodium thio-sul-
phate. The prints may also be developed with—
Potassium ferricyanide.
Water
50 grains.
I ounce.
The following process, recommended by Mr. Bedding, appears to be
one of the most practical for utilising uranium for printing purposes.
It will be noticed that the process is very similar to the platinotype.
The paper must first be coated with ferric oxalate in the proportion
of one grain to each superficial inch of paper. If preserved from
light and damp, the paper in this state will keep some weeks, but the
addition of one grain of mercuric chloride to each ounce of the ferric
oxalate solution assists in causing the paper to keep.
"When the dried iron-paper has been exposed in contact with the
negative, and the characteristic ferrous image obtained, it should be
floated upon a solution compounded in the following proportion :—
Uranium nitrate
Gold chloride
Water
•
15 grains.
I grain.
I ounce.
After the desired depth of definition has been obtained, the picture
should be passed through plain water, followed by immersion in dilute

Ridgway Knight Paris
Typogravure & Imprimerie Boussod, Valadon & Co. Paris.
UNIL
OF
M
PROCESSES.
199
:
hydrochloric acid (1 100), again treated with water, and finally
allowed to dry."
Uranium may be employed to tone silver prints on albumenised
paper. The salt of the metal was also used in the preparation of dry
plates by a method advocated by the late Colonel Stuart Wortley,
who described his process in 1872. It is an emulsion process in which
collodion is used, and is made as follows :—
Collodion (plain)
Cadmium bromide (anhydrous)
Uranium nitrate
Silver nitrate
30
13
I ounce.
7 grains.
""
The uranium and cadmium salts are dissolved in the collodion, and the
silver is then added. The plates, which have been prepared with a
substratum, are then coated with the emulsion in the usual way, and
washed until the greasiness disappears. A preservative must then be
poured over the plate. The developing solution is composed of :—
I. Ammonium carbonate
Water
2. Potassium bromide.
Water
3. Pyrogallic acid
Alcohol
•
64 grains.
I ounce.
•
4 grains.
I ounce.
96 grains.
I ounce,
used in the following proportions :-No. 1, 60 minims; No. 2, 60
minims; No. 3, 15 minims; water, 2 drachms; alcohol, drachm.
As the plates are liable to halation, aurin is used in the plain
collodion. The process was well spoken of in 1873, but has been
superseded by the more popular and useful gelatine methods.
Wothlytype.-Under this title a process was patented by Herr
Wothly of Aix-la-Chapelle in 1864, and a Company was formed in
England for working the process. The nitrates of uranium and
silver were combined with the collodion with which the paper was
prepared. Results were obtained which were certainly very effec-
tive, but the Company was not a success. A print in the possession
of the writer since about 1865 remains in the same condition as when
printed.
Vignetting.—A photograph is said to be vignetted when the outer
parts of the negative are protected from the light, thus causing the
picture to shade off into the white paper. The best way to effect this
is to cut a suitable opening in stout cardboard and serrate the edges,
and place tissue-paper over the opening. Thin sheet-lead may be
used for the same purpose, and has the advantage that by bending
the serrated edge the tissue-paper may be raised or lowered as required.
If printed in the shade, the tissue-paper may be dispensed with.
200
MANUAL OF PHOTOGRAPHY.
Waxed-Paper Process.-Now that films almost as perfect as glass
are available on which negatives may be made, it is very improbable
that waxed paper will ever again be brought into use, although, for
large work, much may be said in its favour. The name of Gustave le
Gray will be remembered in connection with the waxed-paper process,
and the fact that a translation of his pamphlet on the subject passed
through several editions shows that the method was popular about
thirty years ago.
Woodbury-type.-In 1865 the late Mr. Walter Woodbury pub-
lished a process which he named Photo-Relief Printing, but which is
now known universally by the name of the inventor. About the
same time Mr. Swan of Newcastle invented a similar process. The
Woodbury-type is altogether unlike any other process connected with
photography, as will be seen from the following description in Mr.
Woodbury's own words :—
"The production of pictures either on white paper, on opal glass, or
on transparent glass, or on porcelain, by this method of printing, is
based on the principle that layers of any semi-transparent material
seen against a light ground produce different degrees of light or shade
according to their thickness. Therefore, by having a mould in intaglio,
produced by the action of light on bichromatised gelatine, and filling.
the intaglio so produced with a semi-transparent material, we obtain
a mould in which the parts that are the thickest give a dark colour;
and the thinner the layer of material becomes, so it gradually merges
into white. By pouring a mixture of gelatine and colour on to the
intaglio mould, and placing a piece of paper on to the gelatine, and
squeezing the whole between two perfectly true planes, the super-
fluous colour is all squeezed out, and the gelatine, having set, adheres
to the paper, and on being separated from the mould leaves it perfectly
clean. This picture, being in relief when leaving the mould, has sug-
gested the name I have given to this process; but the contracting of
the gelatine on drying leaves hardly any perceptible relief on paper,
which might otherwise be considered an objection.
"I will now proceed to describe my method of operating.
"The Gelatine Relief.—Select several pieces of talc of the required
size, being perfectly uniform in thickness, and by wetting them affix
them to a large sheet of glass; squeeze out all the superfluous moisture,
and polish the whole of the pieces; next prepare the bichromatised
gelatine as follows:-Dissolve in water, 28 ounces, 4 ounces of Nelson's
opaque gelatine; clarify with white of egg, and filter. To 4 ounces of
this solution add 60 grains of bichromate of ammonia dissolved in a
half ounce of warm water and a small quantity of prussian blue (this
serves to give the finished relief a colour by which to judge of its
printing qualities, and does not interfere with the action of the light

UMIL
OF
CH.
CRABING
PAYKER
CAMER
CHARLES J. BRENAN, PHOTO.
Woodburytype.
CRAB INN, SHANKLIN, ISLE OF WIGHT.
PROCESSES.
201
in penetrating the gelatine). When well mixed, filter through muslin,
and pour over the talc-covered glass, place on a levelling-stand, and
allow to set. When set, cut with a sharp knife round the edges of
each talc, and strip from the glass; lay on a piece of blotting-paper
the same size, and clean the talc side; then place in contact with the
negative, and having placed a piece of glass behind, fasten all together
with india-rubber bands, and place in the light of a condenser of six
to nine inches diameter at a distance of about two feet; after expos-
ing from an hour to two hours, according to the density of the nega-
tive, to the sun's rays (a little over- or under-exposure is of no conse-
quence), lay in a dish, and pour some hot water over them until no
soluble gelatine is left; then allow to dry at a gentle heat. When
nearly dry, let the remainder of the drying be done spontaneously,
otherwise the gelatine would split from the talc. Having obtained
the relief supported by the tale, they can be kept in a book ready for
the next operation.
"The Metal Intaglio.-In my early experiments I used the electro-
type process to obtain an intaglio from the gelatine relief, but found
that for any practical purposes it was impossible to obtain uniform
results.
The result of my experiments has been the producing of the
moulds by hydraulic pressure, by placing a sheet of soft metal (a
mixture of lead and type metal) in contact with the gelatine relief,
and subjecting the same between two perfectly true plates of steel to
50 to 200 tons pressure, according to size, four tons to a square inch
being about the pressure necessary. The result is a perfectly sharp
intaglio, obtained in less than a minute's time; the same gelatine
relief will serve for several moulds where a large number of prints are
wanted."
The method of printing is the same as described in the Stannotype
Process, p. 191.
By this beautiful process prints may be made so perfectly to imitate
prints on albumenised paper that it is almost impossible to distin-
guish one kind from the other. The accompanying plate of the Crab
Inn, Shanklin, photographed by Mr. Charles F. Brennan with the
"British" camera, is a very perfect illustration of the process here
described.
Woodbury-gravure.-Until a few months since it was necessary
to mount Woodbury-type prints, but, by an improvement in the
manipulation, prints can now be made on paper which do not require
to be mounted. The method of obtaining this result is by printing
in the usual way; when dry the prints are trimmed and then
transferred on to the paper, on which they appear as if so printed
originally. The process is termed Woodbury-gravure. This improve-
202
MANUAL OF PHOTOGRAPHY.
ment removes what was a great disadvantage in the old process, and
for book illustrations, both as to cost and beauty of result, this method
holds its own with any of the other mechanical processes. The print
of the moon in the section Astronomical Photography is an excellent
example.
Writing Titles.-The following method of affixing titles to nega-
tives, so that the name will appear white on the print, is given by Mr.
Sylvester Parry :-Write the name in block letters, or in any other
way, in Indian-ink on thin strips of talc, which may be attached
when dry to the varnished negative, and if carefully done the outline
of the tale will not be visible.
Yellow Negatives (see Intensifying).-A wet collodion negative is
seldom dense enough for printing purposes when developed with iron
and redeveloped or strengthened with pyro and silver. The late Mr.
G. W. Simpson introduced a method by which the image is changed
to a yellow colour, which is effected in the following way :—The plate,
after fixing and washing, is placed in a dilute solution of potassium
permanganate of about ten grains to an ounce of water. As soon as
the change of colour is visible on the back of the picture, the process
is complete.
Zinc-Etching.-The method of producing zinc blocks in half-tone is
described under the heading Photo-Engraving. The process now to be
dealt with is for making blocks in line to be used in the type-printing
press. The negative should be of the same quality as described for
photo-lithography, having clear lines, and the whites must be repre-
sented in the negative by a perfectly opaque film; and the image, if
it is to be printed direct on to the zinc plate, must be reversed. By
using a print prepared as for photo-lithography, a transfer may be
made direct to the zinc (which must have a slight grain given to it
by means of nitric acid and alum); this must be rubbed up with ink
in the usual way before treatment with the etching acid. A second
method is by preparing the zinc with bichromated albumen :
Albumen
Potassium bichromate (saturated solution)
Water
I
I ounce.
99
7 ounces.
The albumen and water are placed in a bottle containing broken glass
and well shaken; the bichromate is then added. The albumen must
be filtered, and the zinc plate may then be coated. To obtain an
even film, the plate must be "whirled," or made to revolve quickly, so
as to throw off the superfluous fluid. The film must now be dried
over a spirit flame, and care must be taken to avoid dust or air-bubbles.
As the rigid surfaces of the glass and zinc have to be brought in close
contact in the printing-frame, the glass must be perfectly level, and

Dawsons Ph. Sc.
Alfred Dawson del!
Abim
WAY
Hogarth House. Chiswick: A
HOGARTH HOUSE, CHISWICK.
PROCESSES.
203
all the surfaces must be perfectly free from all grit, otherwise fracture
may occur.
As great pressure is necessary, the glass of the printing-frame
should be thicker than usual. The negative in contact with the
zinc may now be exposed to light, and by using an actinometer,
experience will quickly show when the right exposure has been
made. The plate must now be inked with the kind of ink used for
photo-lithographic purposes, but reduced with turpentine so that it
can readily be distributed with a roller on to the zinc plate. The
rolling is continued until the film of ink, by the evaporation of the
turpentine, is so thin that the printed image may be seen through it.
When the inking is complete, the plate is placed in a tray in cold
water, and with a piece of lint the surface is gently rubbed to remove
the superfluous ink, and the image, if proper care has been taken.
will be found perfect on the metal. As soon as the plate is dry it is
ready for the next stage of the process-that is, the etching. Heat
is now required. A metal plate should be placed on a stand so that
gas or other heat may be applied to keep the plate warm-that is, at
about the temperature used when drying a varnished plate. After
the plate has been warmed, it is allowed to cool. It is next covered
or sponged over with a solution of gum-arabic of about the consistence
of cream, and then allowed to dry without the application of heat,
When dry, the plate is sponged over with water to remove the gum,
after which it may be inked with a litho-ink reduced with middle
varnish. The zinc is now coated on the back, and all parts which
are to be protected from the acid, with bitumen varnish.
The plate, slightly warmed, may now be placed in the first etching
bath. The quantity of fluid must depend on the size of the zinc,
and the tray to contain it should be sufficiently deep to allow rocking.
At first a weak acid solution must be used, sufficient nitric acid being
added to the water to make it distinctly acid to the taste; and when
the zinc is in the tray it must be rocked constantly, to prevent the
formation of bubbles of gas on the surface. After about a minute,
the plate is removed from the acid, rinsed under a tap, and the
surface sponged. The plate is now warmed, gummed, and then
fanned until dry. It is then washed and sponged, and, while wet,
is inked as before, and again warmed on the metal plate until the
ink is caused to run down the sides of the etched lines. After cool-
ing, the plate is ready for the second etching, a few drops of acid
being added to the water, and the tray rocked as before. The plate
is left in the acid about three times longer than at first, and the
washing, sponging, and gumming are repeated. In the next part of the
process, the plate is dusted over with powdered resin and the surplus
removed with a soft camel's-hair brush. The ink is now covered
ફ્
204
MANUAL OF PHOTOGRAPHY.
with resin, and the etching process is repeated after the plate has
been heated so as to melt the resin. After each etching, the strength
of the acid solution is increased, and the various operations are
repeated until it is seen that the plate is etched sufficiently deep.
In some cases an after process, called "clean etching," is necessary,
to clear away irregularities left in the earlier state of the process; as
also when the parts which are to appear white when the block is
printed may require to be cleared away with the graver or with a
"router." The zinc may be cut to shape with a fret-saw, and then
mounted type-high in the usual way.
·
PART III.
APPARATUS.
Actinometers and Exposure Tables. To the beginner in the
practice of photography there is perhaps nothing so uncertain as
the exposure required to produce a picture, and until he has had
experience he must expect many failures. He may have read about
exposure tables, and may have tried to apply them, but he will
quickly find that some knowledge of the actinic value of the light is
necessary; he must know whether the plates he is using are quick or
slow (and for his purpose slow plates should be preferred, as being
more under control); and he must know something about the lens
and the value of the diaphragms he is about to use. The light has
very different power as the seasons change; the time of the day must
be considered, and the mere passing of a cloud will have to be allowed
for. All these matters have to be considered in using exposure tables
or other kinds of aid in exposing plates. When experience has been
gained, the appearance of the picture on the ground-glass will be a
sufficient guide; but, at the same time, exposure tables may afford
the means, when used intelligently, of greater uniformity in results.
Many methods have been devised for assisting the tyro in the
matter of exposure. One of the most simple is called the Bijou
Actinometer and Exposure Table, contrived by Mr. I. Watts of
Bowdon, Cheshire.
Among the many devices for ascertaining the chemical intensity of
the light by exposing a strip of sensitive paper to its action, this
actinometer is very convenient, owing to its portability. On the
inside of the lid of the small box which contains it the maker has
ingeniously inserted a set of tables of subjects and stop-ratios,
by the use of which (as explained in the instructions sent out with
the instrument) a very simple arithmetical operation gives the ex-
posure required in seconds. The basis or zero of the tables is an
open landscape subject, for stop the ratio ƒ8 (or an aperture equal to
one-eighth of the focal length of the lens employed), and for the light
a tenth of the time (in seconds) which the paper takes to assume the
205
206
MANUAL OF PHOTOGRAPHY.
depth of colour of the standard tint of the actinometer. These factors
multiplied together and divided by a number representing the sensi-
tiveness of the plate (which has to be found by experiment) gives
the exposure required. As a guide, especially for the novice, it may
be found useful; but it is necessary to remark that neither this nor
any other form of actinometer or exposure tables can be expected to
be more than this, and it must not be supposed to be a substitute for
the exercise of judgment on the part of the operator.
In the following example the number representing the rapidity of
the plate, developed with the normal developer, is 40, but each
operator must ascertain the plate number for himself by actual ex-
periment (decreasing it if the exposure proves too short, and increas-
ing it if too long), so as to adapt it to the plates used, and to the
exact method of development employed:-
Subject: An open landscape with strong foreground .
Actinometer 20 seconds; one-tenth of which is .
Stop ƒ64, equivalent stop number is
Thus :-
2
2
64
or 616 seconds.
40
2×2×64_256
40
or say 6 seconds, which is the exposure required. If a large stop
is used, say ƒ16, the equivalent stop number of which (or, as it is
sometimes called, intensity ratio) is 4, then the formula will stand
as follows:-
2X2X4_16
40
or say half a second.
40
With its aid and careful attention to the directions given, it will
lead to results as satisfactory as any kind of mechanical aid will
afford.
Careful observation and experiment in exposing and judgment in
developing will do more to assist in producing good results than any
amount of study with actinometers.
Mr. Watkin, of Hereford, has patented a very ingenious form of


12
Р
S D
E
FIG. 40.
FIG. 41.
actinometer, shown in Figs. 40 and 41. This handy little instrument
is only 2 inches long, and 13 inches in diameter, and is neatly finished
APPARATUS.
207
in brass; its one defect is the weight, which, for so small a thing,
seems excessive. It consists of an actinometer for testing the actinic
force of the light which falls upon the subject; a set of four circular
slide rules for calculating the exposure; and a time measurer in the
shape of a short chain pendulum, by means of which seconds may be
counted.
The instrument contains a strip of paper coated with a specially
prepared bromide of silver emulsion; this darkens rapidly in light,
and the number of seconds which a small disc of it (the only part
exposed to the light) takes to equal in depth of tint an equal-sized
disc of a standard tint expresses the value of the light.
The values of the other factors (plate, subject, and diaphragm) are
also expressed by numbers.
The calculating slide rules are manipulated in a very simple manner.
Each one carries a pointer, one for each factor, and when they are
adjusted in succession to the value of each factor, a fifth pointer
indicates the correct exposure in seconds or fraction of a second.
Another form of actinometer is the invention of Messrs. Hurter
and Driffield, of Appleton, near Widnes, who have recently published
an important paper on photo-chemical investigations. The laws which
the authors have found indicate that, beyond a control over the general
opacity of the negative, little or no control can be exercised by the
photographer during development. Careful experiments made by
themselves and by others fully bear this out, and show that neither
under- nor over-exposure can be really corrected by modifications of
the developer, but that truth in gradations depends almost entirely
upon a correct exposure, combined with a development which must
vary in duration according to the purpose for which the negative is
required.
They also found that when light acts upon sensitive plates, the
action at first is proportional to the light-intensity: it then becomes.
more and more nearly proportional to the logarithm of the light-
intensity. A point is next reached when an increase in the exposure
produces no further increase in the density, and the action is finally
reversed.
The law may be shortly stated thus: the amount of silver salt
affected at any moment of the exposure by the light is proportional
to the light-intensity, and to the amount of unaltered silver salt on
the plate at that moment.
Considering a correct exposure an absolute essential in the produc-
tion of a satisfactory negative, Messrs. Hurter and Driffield have
invented an instrument for estimating the exposure to be given under
various circumstances and with plates of various rapidities. This
instrument they call the "Actinograph."
208
MANUAL OF PHOTOGRAPHY.
The accompanying engraving (Fig. 42) represents the instrument.
It consists of four scales corresponding with the light, the lens, the
speed of the plate, and the exposure. The light-scale is wrapped
round a revolving roller, which also bears on its outside edges a
calendar. When it is desired to calculate an exposure, this roller
is turned till the date is level with the edge of the lens-scale. The
intersection of the edge of this scale with the curves on the roller
represents the intensity of the light at the various hours of that par-
ticular day. The lens-scale is marked with the various lenses and
diaphragms in common use. The next proceeding is to set the lens
and diaphragm to be used opposite this hour curve on the roller scale.
The "speed index," marked on a small slide, is now set to the speed

FCB
FIG. 42.
of the plate, when five points on this same small slide point to five
different times of exposure, and the photographer has only to select
the one appropriate to the state of the atmosphere.
Balance.-Used in an artistic sense, this term refers to the arrange-
ment of lines and other effects in the composition of a picture.
An instrument of the greatest value in the laboratory of the chemist
is called a balance. For ordinary photographic purposes the delicacy
attainable with this instrument is not necessary; the ordinary scales
and weights answer every purpose, as it can only be in very rare
cases that a difference of a grain or two can affect results; but with
ordinary scales considerable accuracy can be obtained.
Baths and Dippers.-The best material for a bath for silver nitrate
solution is glass. When, however, large plates are used, the quantity
of solution required is much greater than when a flat dish is used,
and involves much more trouble and waste in filtering; but for plates
of moderate size, 8 x 6 and less, the glass dipping bath is more con-
APPARATUS.
209
venient than any other. Porcelain answers for a time, but the glaze
cracks. Ebonite is very brittle, but is a good material for the pur-
pose, and it has the advantage of being light. For large plates a
well-bath is the best, and, when made of seasoned wood and well
varnished with black varnish, is very serviceable. A deep porcelain
dish may, with care, be used; and as very little more solution than will
cover the plate is necessary, the dish may be tilted without fear of
throwing the silver over the end of the dish.
Dippers of glass are useful for small plates, but they are scarcely
safe, as they are very liable to be broken. Well-varnished wood is a
good material. The piece on which the plate rests may be fastened
by rivets of silver wire. When varnished with shellac varnish, such
a dipper will last many years; but, in course of time, will become
saturated with silver. Dippers may be made of stout silver wire,
but for all practical purposes wood should be preferred.
The term bath is often applied to solutions employed for various
processes.


FAIR KIERKITYS
FIG. 43.
FIG. 44-
Fig. 43 shows a form of bath with water-tight top suitable for
travelling; and Fig. 44 shows the dipper and plate.
Bellows. In cameras which are made to fold, the calico or leather
portion uniting the front and back parts is called the "bellows." A
rectangular or cone-shaped box is first made of the required dimen-
sions. This is covered with calico, and upon this strips of thick
paper, properly cut so as to fold correctly at the angles, are glued, and
the whole is then covered by glueing on the calico or leather. When
dry, the pleats are carefully drawn together, and, with care, will
always keep their shape when folding.
Buckle's Brush.-In cases where solutions require to be spread with
a brush, and where the ordinary camel's-hair would be destroyed,
a convenient substitute may be formed by drawing (by means of a
210
MANUAL OF PHOTOGRAPHY.
bent wire) a tuft of cotton-wool partly within a glass tube. The pro-
jecting tuft of wool can be renewed as often as necessary.
Burnishers and Rolling Machines. Most photographs on paper
are improved by rolling. The necessity for passing the paper through
water changes the surface; the rolling restores the paper to its ori-
ginal condition, and gives the print a more finished appearance.
Prints with a matt surface are improved by simple rolling. When a
very high polish is required, heat is necessary. This is obtained with
the machine called a burnisher, one form of which is shown in
Fig. 45.
A bright steel bar is made very hot by means of gas or a

G
FIG. 45.
spirit-lamp. After the pressure is regulated for the thickness of the
card, the print is dragged by means of the roller, which is roughened,
over the steel bar, and the operation is repeated until the required
polish is obtained. It is usual to lubricate the print by rubbing it
over with Castile soap dissolved in methylated spirit (about five grains
of the soap to an ounce of spirit), which must be allowed to dry
before passing the print over the burnisher. With care, a very high
polish may be given to the print by this means; but there is always
the possibility of spoiling the work, and particularly is this the case
with vignettes. A safer method is to use a machine having two
rollers, one of which is hollow and heated by a row of small gas-jets.
One of the rollers is of burnished steel, and the pressure and heat
give the prints a very fine surface. If the rollers are kept bright, no
injury can result to the print.
Many varieties of rolling-machines and burnishers are in the market,
and with care a good surface may be given to prints by any of
them.
Cameras.-The more correct term for this important, and, to the
APPARATUS.
211
photographer, indispensable instrument is camera obscura, so named
by the inventor, Baptista Porta, three hundred years ago. The term
"camera" signifies merely a box or chamber; for the photographer's
use it is necessarily dark, excepting to the light which enters by the
lens. The camera is so well known that it may seem unnecessary to
describe it, but as it has been greatly altered and improved since
Daguerre's time, some detailed notice may be given.
The simplest form of camera is shown in Fig. 46, which may be
readily constructed out of a common cigar box, a. A spectacle lens of
suitable focus is placed at b, in a sliding tube made of cardboard; and
a piece of looking-glass at an angle of 45°, at c. A part of the lid

M
e
D
a
a
FIG. 46.
A
C
e
¿

D
C
L
H
B
་
FIG. 47.
having been removed and hinged, e, side-pieces are added for the pur-
pose of partly cutting off the side-light; and a piece of ground-glass
is then placed to receive the image at d. This is an interesting toy.
The engraving Fig. 47 shows the camera as used by Daguerre. The
improved instrument for photographic use is shown in Fig. 48. It is
made to fold.
The Fig. 49 shows another improvement, having a sliding front
and contrivance for using lenses of different foci; this form could be
used for portraits as well as landscapes. Another great improvement
was in the construction of cameras for use in outdoor photography;
the front and back of the instrument were connected by means of
what was then termed a flexible bag, now known as the bellows. The
212
MANUAL OF PHOTOGRAPHY.
base-board of the camera was made to fold, as shown in Fig. 50, and
the bellows to fit into the box part, forming a very handy instrument
when compared with Figs. 48 and 49.

FIG. 48.
For studio-work a camera should be square and strongly made, and
should have a bellows body. If desired, a sliding front may be added,

کہ کو گرا کے
FIG. 49.
but this is scarcely necessary, as the camera stand is usually sufficient
to give the various levels. The back of the camera may be arranged
to take a single as well as a sliding-back, so as to make one or more
APPARATUS.
213
exposures on the same plate. A swing-back will often be found
useful.
One of the earliest forms of the improved folding cameras was the
"Kinnear." For many years it held its place, and little improvement
was effected prior to the advent of gelatine dry plates; but when the
silver bath was superseded for outdoor-work, the demand arose for an
instrument of less weight and greater portability, which demand has
been met in a very abundant manner.
It is almost unnecessary to
say that with any camera which is light-tight perfect success may be
attained, and that expensive brass fittings are not at all necessary ;
neither are many of the small accessories which, in some instances,
have been patented; but it would almost appear, from the demand
which exists for work of the most expensive kind, that the purchasers
are under the belief that they will be unable to make respectable

is an efficient instrument.
FIG. 50.
pictures unless they are provided with everything the ingenious
cabinetmaker or the skilful brassfinisher can add to the dark box or
case we call the "camera.
camera." This is all a mistake. What is wanted
Some brasswork there must be, but all
that is used beyond what is required for strength is so much money
thrown away. Utility is often sacrificed for lightness. The names of
Hare and Meagher occur as makers of some of the first improved port-
able cameras, and their work is of a very high class. M'Kellen made
some improvements, which were patented, and some of these patented
improvements are now used by many makers of cameras. It was the
writer's intention to describe and illustrate Mr. M'Kellen's cameras,
but the necessary information has not been supplied. For work of a
very high class the name of Mr. Billcliff is well known.
Figs. 51,
52, and
show one form of his cameras.
53
It is made square; but as
plates are usually oblong, and as an upright picture is often required,
214
MANUAL OF PHOTOGRAPHY.
a ready means of reversing the plate is necessary.
Mr. Billcliff accom-
plishes this by using what he calls a "revolving adaptor." Fig. 52


FIG. 52.
FIG. 51.

FIG. 53.
shows how the plate can be used in either position without the neces-
sity for reversing the camera.
Another camera of excellent quality and workmanship is called
the "British," and is supplied by Mr. Chapman of Manchester.

THE
עון
MICH
FIG. 54.
Fig. 54 shows the camera on a tripod stand, and in the position
it is required for general work-that is, perfectly level.
APPARATUS.
215
Fig. 55 shows the use of the rising front. If the camera has not
been disturbed, and the subject is a building, the image will be quite
true to nature, or, in other words, the lines will be correct and not
distorted. Supposing, however, that after raising the lens as high as

A
THE
B
FIG. 55.
possible, as shown in Fig. 55, the upper part of the subject is not
included, we must then tilt the camera and bring it into the position
shown by Fig. 56, which indicates that the front part of the camera
is pointing upwards and the back vertical or plumb; or we may say

A-
THE
9RITISH
B
FIG. 56.
that the sensitive plate is made parallel with the sides of the object
being photographed. And here may be stated the one rule in photo-
graphy to which there is no exception, and that is, when a building
or any object has parallel, upright, and horizontal lines, and the lens
216
MANUAL OF PHOTOGRAPHY.
used is of the rectilinear type, the sensitive plate must be perfectly
plumb, or the resulting picture will not be true to nature. This is
one of the first principles to be thoroughly understood by the beginner
in photography.
Few persons can judge correctly when an article is set square by
merely looking at it, and as most modern cameras are built in such
a manner, that when opened out, the back and front parts require
setting square, it becomes necessary to use some mechanical means
for showing when the camera is level. The simplest of all methods
is no doubt the use of the spirit-level. Another plan is to use a
plummet-line in the way indicated in the woodcut, Fig. 57.

THE
9RITISH
B
น
FIG. 57.
This figure shows the back of the camera parallel with any upright
included in the view; but, as will be noticed, the front part of the
camera, upon which the lens is fixed, is not parallel with the back,
but leaning towards it. It may be considered by some that such a
position is not correct, and that there will be distortion. This is not
so; there is, however, a necessity for working with small stops with
the lens when used in such a manner, because the axis is thrown out.
of the horizontal line. If the lens is one that will cover much more
than the size of plate in the camera, then the lens can be brought to
the horizontal position by loosening the two front screws B B, push-
ing the lens board down, and bringing the top portion forward until
the front is parallel with the vertical back, as shown in Fig. 58.
This arrangement is useless if the lens will not cover a much larger
plate than the one in use, on account of the centre being so much
above the centre of the plate. This movement is, however, useful
when the worker wants to take two pictures on the same plate—that
APPARATUS.
217
is, one above the other-or two horizontal views. When this is
required, a piece of opaque material such as thin vulcanite, or a piece
of ferrotype plate, is placed in the reversing back of the camera, and
arranged so that by sliding it up or down we cut off that portion of

A..
..the
PRITISN
B
FIG. 58.
the plate we do not wish the light to act upon during the exposure of
its counterpart.
Fig. 59 shows the camera tilted, with back and front brought ver-
tical, and the lens-board, C, raised so as to include a very extreme
height. Such a position is seldom required, and is really of no use.

A..
TIC
||BRITISHI
REW
B
FIG. 59.
unless the lens used is one that will cover a very large area. The
position, however, shows one great advantage this camera has over
many others, viz., that no light is cut off by the bellows.
When it is necessary to use the lens pointing downwards, as, for
instance, in taking a view from a great elevation, the camera will have
to be placed in the reverse position to that shown in Fig. 59, ¿.e., the
218
MANUAL OF PHOTOGRAPHY.
screws A and B B will require removing to the lower holes shown
in the sketch; the back and front can then be made vertical. This
adjustment is so seldom required, that the fact of having the camera
perfectly square when opened out far outweighs any objection offered
against the trouble of shifting the screws.
This somewhat lengthy description is given, as the remarks apply
to many other cameras. This one particular camera is selected, not
for any peculiarities in itself, but because it is quite impossible to
describe many forms of the instrument, and all cameras of the better
kind are so made that a description of one good one may almost be
taken as sufficient for dozens of others. Each maker usually con-
trives to introduce some little alteration, which may or may not be
an improvement; but as such slight alteration or addition may not
be at all necessary for the production of good work, it need not
be described.
One of the great advantages of the modern portable camera is that


THORNTON
PICKAD
H
IME
SHUME
FIG. 60.
FIG. 61.
there are, in some cases, no loose parts. The instrument is complete
in itself, and only requires to be set upon its tripod or other stand and
opened. By adopting the turntable, the old triangular top of the stand
is dispensed with. By an ingenious arrangement Messrs. Thornton
and Pickard have so attached their shutter as to permit of its being
used at the back of the lens, and of falling within the turntable
opening when the camera is closed. Figs. 60 and 61 show this
recent adaptation.
In all the early forms of camera the focussing was effected by sliding
the back part by means of a long screw worked by a handle in front,
excepting in cases when the lens was supplied with an accessible rack-
and-pinion movement; the latter is the most convenient method.
The swing-back and swing-front movements are comparatively modern
APPARATUS.
219
improvements in cameras, and they have certain advantages. By swing-
ing the back, objects can be brought into focus which otherwise
would not be properly defined. The use of this will particularly be
seen in taking groups of figures and in defining the foreground of a
landscape subject. The use of the swing-front will be seen by referring
to Fig. 58. It is important that the camera should have a rising front
—that is, the part to which the lens is attached should be movable.
The advantage of having the front to move is that when objects do
not appear just as required on the plate the rising movement permits
the proper adjustment, and, in cases where the lens covers more than
the plate, this is often very important. With lenses which will do
very little more than cover the largest plate used with the camera,
raising the front may cause the corners of the picture to be cut off.
In some cameras the front has both vertical and horizontal motions.
It is often convenient to be able to use lenses of long and short
focus in the same camera. This is effected by what is called a double
extension. The methods by which this is carried out are very varied;
sometimes two sets of racks and pinions, and sometimes a rack and
pinion which can be used when the back and front are fully extended
on the base-board, are employed. However carried out, this is a very
important addition to a camera to be used for landscapes.
Cameras, in great variety, are made for special purposes. For
taking pictures for the stereoscope, any camera which will hold a
plate 63 by 31 inches (or the half-plate, if preferred) may be used,
if the lens be attached to a front capable of movement, so as to bring
the centre of the lens opposite to the centre of the place to be occupied
by each picture. Whether one or two lenses be used, the camera
must have a division, so as to separate the interior into two parts.
Fig. 62 shows a camera fitted with twin lenses for stereoscopic work,
as also with the Thornton-Pickard instantaneous shutter. When two
lenses have to be uncovered, much
care is required to prevent the
camera moving. Two caps may
be used, but must be so attached
as to be removable together. When
the twin lenses do not project
beyond the camera front, a cover
may be attached by the centre
between the lenses, and both lenses
uncovered and covered by one
motion, up and down; the cover
should move freely, and the camera

A
FIG. 62.
D
should be firmly fixed on the
stand. A simple way to make exposures with two lenses is to use
220
MANUAL OF PHOTOGRAPHY.
the focussing cloth or any other dark object. With care, very rapid
exposures may be made in this way.
>>
The great popularity of photography has called into use a variety
of instruments by which pictures of small size may be taken without
much trouble-cameras which may be used without a stand, and
called "detective or hand cameras. Some of these show much
ingenuity in their construction. They are generally made to contain
many plates, or are fitted with roller slides, so that films of sensitive
material may be used. The plates and films must be of the most
sensitive kind, and the method of making the exposure must be
rapid. All these requirements are met in cameras of this class when
of the best kind, and for tourists it would be difficult to suggest
anything more convenient when pictures of small size only are
wanted. At the same time it should be remarked that, unless
great care be taken in using these instruments, much disappointment
will be caused. Many cameras of this type are fitted so that a
miniature of the scene to be photographed can be viewed by reflec-
tion. Snap-shots" will as often fail as succeed if the camera is not
fitted with the reflecting mirror. Excepting as toys, the very cheap
detective and hand cameras cannot be recommended; although it
must be admitted that, under favourable conditions, fairly good photo-
graphs may be made with these cheap instruments.
(C
As an example of the better class, the "Kodak " has been selected
for description; not because it is better than many others, but as a
FIG. 63.
type of the whole. With
this camera the roller slide
and flexible sensitive film is
used. The illustrations ob-
viate the necessity of length-
ened description. Fig. 63
shows the camera, and the
way it is held when in use.
Fig. 64 shows the general ap-
pearance of the instrument,
which is made in five or six
different sizes. It has a very
neat appearance, being well
finished. It is packed in a
case, which can be carried
by means of a sling, or by

a strap in the usual way, as shown in Fig. 65. Of course the lens
is covered with a shutter for quick exposure.
The shutter is set by
pulling a cord; while the exposure is made by pressing a button in the
side of the camera, and may be very rapid or prolonged, as necessary,
APPARATUS.
221

—————
FIG. 64.

FIG. 65.

FINAN
FIG. 66.
I
222
MANUAL OF PHOTOGRAPHY.
according to the light or subject. Fig. 66 shows the "roll-holder."
The small as well as other sizes of the camera are made to carry
sufficient length of flexible film for a hundred pictures,

FIG. 67,
3
having dimensions varying from 2 to 5 inches. In
some of the other sizes the film is sufficient for sixty,
forty-eight, or thirty-two exposures. The illustration
shows the spools within the camera, and Fig. 67 shows
the spool itself. For use, the film is wound on a
wooden cylinder, and, as required, is drawn off on to
a second cylinder. The lengths are marked automatic-
ally during use, so that the exposed part may readily
be detached.
An ingenious form of hand-camera has recently been introduced by

FIG. 68.-Side View showing Interior.

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FIG. 68A.-Interior Cross Section.

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REMARKS
FIG. 68B.-Base Fittings.
Messrs. Marion & Co. (Dickenson's patent), which they call "The
Radial;" it is illustrated in Figs. 68, 68a, 68b.
B
APPARATUS.
223
This camera takes its name from the novel method of carrying the
plates in radiating grooves, which find their common axis in the
centre of the exposing position.
The exposing groove runs across the axis of a drum. The drum is
made to revolve in such manner that this groove can with great
exactness be brought to, and made to form a continuation of, any one
of the radiating grooves wherein the plates are stored. When the
plate is transferred from the one half of this now combined groove
into the other half, the drum is again turned to a defined position,

FIG. 69.

FIG. 70.
and the plate is then in its exposing position. It will be seen that to
transfer the plate into its original groove and to obtain another, it will
only be necessary to repeat the action already taken, until all the
twelve plates have been exposed. The size of plates used is 41 × 31.
In Figs. 69 and 70 a camera of a different class is shown. Miller's
Adelphi" hand-camera is certainly one of the simplest kind. It is
made to carry a dozen plates, 4× 31; each plate is protected by a
sheath, and when a plate has been exposed a simple movement allows
it to fall forward on to the inclined part shown in the figure, and
then by tilting the camera the plate falls into the receptacle below.
224
MANUAL OF PHOTOGRAPHY.
When enlargements of more than ordinary dimensions are required,
it becomes inconvenient to use dark slides, and for sizes beyond two
feet in diameter it is preferable to have a room specially fitted for
the purpose; the room then becomes the camera, the object to be
copied being outside, while the lens may be fixed in a suitable
aperture in a shutter, and the stand for holding the sensitive plate
may be on rails, so as to be always parallel and easily moved for
different sizes of work.
In Figs. 71, 72, and 73 is represented a camera which may be used
for all kinds of copying up to the limit of the size of the apparatus,
which in this case is 24 inches by 24 inches. This form of copying
camera, so far as it differs from all others, was suggested by the
writer, and was made for him by Mr. Billcliff of Manchester. The
woodwork is of well-seasoned mahogany throughout. The importance
of the wood being properly seasoned is tested by all the parts being
interchangeable with a duplicate instrument of the same size. The
base, a, Fig. 72, is framed very strongly, and is 6 feet long by 1 foot
9 inches wide. Two focussing screws run from end to end, and can
be worked from either end of the frame by means of the handle s',
which is loose, and is used for either screw. The camera, as in the
figure, is arranged for using plates 22 inches by 18 inches. The
piece, marked b, slides on to the base, and can then be attached.
to the focussing screw, while the bellows part, when extended,
slips into the back of c, in the groove which holds the dark slide
when this part is used without b. The piece c is not attached
to the focussing screws when b is in use, but slides in the groove
of the base. The part d is merely a frame to carry the bellows, g
and h. The front piece, e, which carries the lens, is attached to the
base by screws at i on either side, and is worked by the handle at s'.
Screws at hold the front of the conical bellows to e.
This part, e,
has the front carrying the lens made to slide vertically and horizon-
tally, for the purpose of centering the object to be copied. These
sliding parts are seen in Fig. 73. Lenses of various sizes can be used
by means of square boards to which the lens flanges are attached, and
these boards are made to fit, as shown in Fig. 73, in the place of the
reversing box. When the end-piece for plates 24 x 24 is to be used,
it takes the place of b. Blocks are placed under the screws at i to
raise the lens to the proper height, and by proper adjustment the
bellows at g and h do not interfere.
The parts n and o, Fig. 71, are used when transparencies, or en-
largements from negatives or transparencies, are to be made. The
part n is screwed on at i, and the piece o merely slides in the base.
This part, it will be seen, supports the carriers for holding the nega-
tive or transparency to be copied, as also a mirror when one is to be

W
H.
UNIL
OF
Fig. 71
Fig.72
ๆๆ
b
k
f
d
n
C
9
d
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h
m
k
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712
COPYING AND ENLARGING CAMERA.
S
Camera arranged to show
Reversing mirror box at S
Fig. 73
b


APPARATUS.
225
used;
but this is not always necessary, as the camera may be turned
towards the sky, or a sheet of white paper will serve as a reflector.
The frame, n, is fitted in front (not seen in the figure) with vertical
and horizontal movements, as previously described; and the lens is
also carried on this part. As n is attached to the piece at i, it is
controlled by the screw at f.
In Fig. 73 the position of the box holding the reversing mirror is
shown. At Ρ the head of the screw clamping the front to the focus-
sing screw is seen. The two screws at r are used for attaching a
small copying-board to this end of the camera, and it is sometimes
useful when working with lenses of short focus.
The camera is carried on a strong stand on 3-inch wheels which
run on rails attached to the floor. The stand is enclosed and forms a
cupboard, which is utilised to hold the various parts of the camera
not in use. When not in its usual place in the camera, the focussing
screen stands underneath, and is held in its place by the catch at m.
However fine the ground-glass may be, it is almost impossible
to focus accurately upon it. This difficulty is removed by fixing
small pieces of thin glass, such as are used for covering microscopic
objects, on various parts of the ground-glass, as described on page 231.
(See Focussing-Screens.)
With this camera plates of every size up to 24 × 24 may be used,
but the part c, which is 16 inches square, will be oftener required
than the two larger parts. Separate backs are provided, which slide
into the place of the one used for 16-inch plates, but these will only
take plates up to 12 inches by 1o in one case, and sizes from 41 × 31
up to 8 x 6 in the other. The advantage of using these backs for
different sizes of plates needs no description.
Double Dark Slides and Changing Boxes. -When using the camera
away from home, it is often necessary to have the means of carrying
more than one plate. The simplest way of effecting this is to have
the plate-holder made to carry two plates, so that, by reversing, each
plate may be exposed in succession. This is, without doubt, the best
method; but the weight and inconvenience of carrying many such
double dark slides has brought into use changing boxes, changing
bags, and other contrivances for lessening weight. One of the earliest
of these changing boxes was contrived by the late Mr. Dancer. It
consisted of a box upon which the camera was fixed. As each plate
was required it was brought into position for exposure by means of a
brass rod, which was screwed into the frame carrying the plate, and
returned to the box in the same way. Hare's changing box is good;
but all contrivances of this kind have the disadvantage that, unless
the plates are of one uniform size, there is the possibility that the
plate will not drop into its place when required.
P
226
MANUAL OF PHOTOGRAPHY.
As a dozen plates can be carried in six dark slides, and as the
difference in the weight of the woodwork in the slides and the box
to hold twelve plates is not very great, preference should be given
to the double backs. Amateurs too often think more of obtaining a
number of photographs than a few of good quality. Six well-selected
views will give much greater pleasure than a dozen which have been
taken without sufficient care having been bestowed on the selection
of subject; therefore it is better to be satisfied with three dark slides
(holding six plates) than double the number (and weight) if the plates
only yield subjects of no artistic value. For one good picture seen in
an amateur's collection there may be fifty very indifferent ones; but
this would not be the case were more care taken in the selection of


FIG. 74.
ענונו
FIG. 75.
subjects, which care would be induced if the number of plates carried
were limited to a few for each day's work.
What has just been said should always be remembered when using
the roller-slide. To some extent this method of carrying sensitive
films will supersede the dark slide and glass plates.
Camera Stands and Tripods. For indoor work the stand or table
for the camera should be solidly made. The form shown in Fig. 74 is
one of the best of its kind, and sufficient for cameras up to 12
or 14 inches. The stand shown in Fig. 74 would be useful for
copying, so far as the limit of the length of the bellows will allow;
but when used for that purpose, care must be taken that the back is
perfectly upright. The swing-back is quite useless in a camera em-
ployed for copying purposes.
For cameras of large size, used out of doors, a tripod of the old-
fashioned kind shown in Fig. 75, strong and firm, will perhaps be
more useful than the lighter and folding kind now generally made.
APPARATUS.
227
Folding tripod stands are now made in so many patterns that it is
difficult to select one for description. It should be said that the
points to be desired are lightness and rigidity, and that these are to be
found in all of the best kind. It is often useful to have the lower
joints made to slide, so that on uneven ground the difference in
level may be adjusted by means of the legs. Tripods are also made
in telescope form.
Condenser.—When artificial light is used for enlarging purposes,
many of the rays will not pass through the object-glass employed
for making the copy unless a condenser is used. The effect of the
condenser is to bring together the rays which would be lost-that
is, would pass outside the enlarging lens; but by interposing the con-
denser (which should be of a diameter equal to the negative or posi-
Two
tive to be enlarged) the full effect of the light is utilised.
plano-convex lenses are generally required, placed with the convex
sides towards each other, and in close contiguity. Other forms may
be used, but in no case is it necessary that they should be achromatic,
as the enlarging lens itself achromatises the light.
Dark Room. Upon the proper lighting and arrangement of the
dark room much of the pleasure of working photographic processes
depends. If possible, the position should be chosen so that the room
has a "borrowed" light, such as one facing the north. A safe light
for working the wet collodion process in such a room is yellow glass;
if this be found insufficient, another sheet of glass may be added, or
yellow paper, or a screen with yellow paper may be arranged so that
it can be drawn when required. For the more sensitive gelatine
plates the light must be tested and modified according to circum-
stances. If artificial light be used, a candle protected by a “hock
bottle" is useful. Numberless contrivances have been proposed, all
more or less effective, but the operator will soon discover what is
required in his own case. The fittings of a dark room need be very
simple, viz., a sink, over which to develop plates and to get rid of
water, and a supply of water by means of a tap, or in some other
way. Plates can, of course, be developed over a dish with water
poured from a jug, but something more is necessary if comfort is to
be considered.
It adds very much to the pleasure of working if everything after
use be put away clean. All dishes and glass measures should be
washed and put in their places.
Diaphragms and Stops.-These accessories of a lens are used to
limit its aperture, and are sets of metal slips with a central circular
hole.
When the slip is placed in contact with the lens, it is called a stop;
otherwise, it is a diaphragm. The use of a diaphragm to correct
228
MANUAL OF PHOTOGRAPHY.
spherical aberration is referred to in the article on the " Optics of
Photography." An oblique diaphragm has been suggested; when
inclined, a larger pencil of light is admitted to the lens from the fore-
ground than from the sky; in this way greater cloud detail can be
secured.
1
30
The diameter of diaphragm that can be used will be greater the
smaller the spherical aberration; if too small, the image, though flat,
is wanting in relief. The minimum useful size is th of the focal
length. On the other hand, by using a single lens with a diaphragm
having too large an aperture, the spherical aberration is not com-
pletely neutralised, so that a hazy or out-of-focus portrait can thus be
obtained. The use of the diaphragm in portrait combinations is to
increase the depth of focus; for, being capable of use with a large
aperture, these lenses lack depth of definition-i.e., they only bring
to a focus on the ground-glass objects in a single plane near the lens.
Hence the nose and ears of a sitter, or the several figures of a group,
cannot all be sharply focussed at one and the same time without the
use of a diaphragm.
The object should not be focussed with the stop intended to be
used (particularly if it is to be a small one), as in that case the posi-
tion of the ground-glass is not distinctly fixed; for, when focussing on
a distant object, it will be noticed that a slight change in the place of
the ground-glass produces no material difference in the sharpness of
the image; this is most noticeable in non-aplanatic lenses. With any
kind of lens it is better to focus, not the centre, but a point about
one-fourth from the side of the plate, using a diaphragm about twice.
the diameter of the one necessary prior to inserting the smaller one;
the smaller the diameter the greater will be the sharpness of the
image. A small stop has the tendency to lessen the vigour of the
picture; moreover, it must be remembered that the time of exposure
is increased in proportion as the diameter of the stop is diminished.
By the U.S., or uniform system, adopted by the Photographic Society
of Great Britain, a series of apertures is arranged, so that, starting
with £
as a unit, the diameter of No. 1 is always one-fourth of the
equivalent focus of the lens in use. The diaphragms are numbered
1, 2, 4, 8, 16, &c., and the numbers show at once what the exposure
should be; thus, if, the unit stop, required one second, the second
f
4
4
I
stop would require two seconds, the third four seconds, and the fourth
stop eight seconds, and so on. By adopting this system the exposure
with different lenses can be made uniform.
The diaphragms in use with most lenses are marked so as to show
their focal value. That is, if a lens has a focal length of 8 inches,
APPARATUS.
229
and the largest size stop be one inch aperture, it will be marked
f
; and so on to the end of the series.
8
An excellent rule to be remembered is that all lenses are equally
rapid if the ratio between the aperture of the stop and the focal
length of the lens be the same; that is, if, in comparing the two
f f
lenses to be used, the aperture of the stop be or or any other
8 16
definite ratio of the aperture of the lens, the exposure will be the
same in both cases.
Dishes and Trays.-There appear to be difficulties in the way of
making dishes of large sizes in glass, but there can be no question
that glass is much to be preferred to porcelain or any other material.
Dishes or trays may be made with glass bottoms, wood being used
for the sides, but the tendency to breakage makes them unsafe to use.
No kind of cement appears to be capable of making vessels of this
description perfectly watertight for any length of time when in use.
Porcelain is very satisfactory while the glaze remains perfect; but
after a while, when silver has been used, the silver seems to find its
way under the glaze, and cracks and other defects then appear in all
directions. For water and many solutions the porcelain trays answer
perfectly. Vulcanite, also, is very satisfactory for trays up to 16
inches; but the material is thin, and as brittle as glass. In the
Amateur Photographer, January 16, 1891, it is stated that ebonite
trays may be repaired with Proutt's elastic glue. The glue is applied
like sealing-wax. A hot wire may be used to spread the glue. If the
manufacturers of ebonite trays would make them of thicker material,
and if the elastic glue will make a fractured tray again serviceable,
vulcanite or ebonite trays would be used more extensively than at
present, as they are easily cleaned, are not affected by acids, and are
lighter than glass or porcelain. Dishes are also made in a material
called granatine, in celluloid and in enamelled metal.
Willesden paper answers for certain purposes. Dishes made of
zinc may be employed when the solutions do not affect the metal.
Dropping Bottles.-When solutions in small quantities are re-
quired, it is convenient to have a ready means of obtaining them
without the necessity of using both hands. Bottles are made with
stoppers adapted so as to enable this to be done.
Focussing and Focimeter.-When an object is distinctly visible
on the ground-glass of a camera, it is said to be in focus. With a
properly corrected lens the photographic image will be correctly
represented if the plate be placed in the same position on the ground-
glass. If, after careful experiments, the developed image is found
not to be sharp, the defect may arise from the face of the ground glass
230
MANUAL OF PHOTOGRAPHY.
not registering exactly the same as the sensitive plate. This can be
tested by removing the lens and then measuring accurately from the
opening in the camera to the ground-glass, and afterwards to a plate
placed in the dark slide; should there be any difference, it may be
corrected by altering the ground-glass. In cases where the chemical
and visual foci are not coincident, the instrument devised by Claudet,
and called a focimeter, may be used. When it has been determined
that the ground-glass is in its proper place, and that the focus is
not distinct when a plate has been tried, by using the focimeter,
the perfect coincidence of visual and chemical foci may be deter-
mined by the simple arrangement of the numbered cards placed at


6
3
N
ma
7
FIG. 76.
FIG. 77.
gradually increasing distances from the lens, as shown in Figs. 76 and
77. Focus accurately for the middle one, insert a sensitive plate,
expose, and develop. If the focussed card comes out as sharp in the
proof as its image on the ground-glass, the two foci are coincident.
If another of the cards appears the sharpest, the lens must have a
chemical focus longer or shorter than the visual, according as this
card was farther away or nearer than the one focussed for; and after
each focussing, were such an uncorrected lens being used, the camera
would have to be drawn out or pushed in sufficiently to allow for the
difference in focal strength.
It is very rare now to find a lens in which the chemical and visual
foci are not coincident.
Focussing Cloth.-There is a kind of twill-cloth sold which is
better for the purpose of excluding light while focussing than velvet
or any other material; but any description of cloth is suitable if
opaque. If to be used out of doors, some means of fastening the
cloth should be adopted, as the wind is sometimes very troublesome.
Attempts have been made to dispense with this useful but incon-
venient part of the apparatus by adopting a focussing tube attached
APPARATUS.
231
to the apex of a cone. This, when placed against the ground-glass,
enables part of the picture to be viewed and the focus to be obtained;
but there is the disadvantage that the whole of the subject cannot
Hence the cone is of little use, owing to the view being
be seen.
limited.
Focussing Glass or Magnifier.-A magnifier of some kind is a
useful aid in obtaining a sharp focus. It is formed of two plano-
convex lenses mounted with the convex surfaces inwards, and fixed
in sliding tubes to allow of adjustment of focus. The focus is found
by placing the end of the tube against the plain side of the focussing
screen and sliding the lenses until the ground surface of the glass
is seen perfectly sharp, when, by means of a screw-collar, the two
tubes are clamped together; thus, while the same camera is used, the
magnifier is always in focus.
By
Focussing Screen. -All cameras (except those in which lenses of
fixed focus are used) are supplied with a screen of ground-glass upon
which the image to be copied is focussed. The finer the texture
of the ground-glass the better will be the definition; but, however
finely the glass may be ground, the slight roughness will sometimes
interfere with good definition. This glass should be of patent-plate
ground to a fine surface with emery powder mixed with water.
rubbing two pieces of glass together the emery will soon remove the
polish, leaving a very fine ground surface; the finer this is the clearer
will be the image projected on it. As a temporary substitute for the
ground-glass, a piece of clear glass may be made dull by dabbing it
over with putty, or a plate may be coated with collodion, sensitised,
washed, and then dried. Matt varnish may also be used.
When it is seen that the subject to be photographed is in the
proper position on the ground-glass, a stop larger than the one to
be used should be inserted to obtain the focus. If photographing
a landscape, an object in the mid-distance should be selected as the
focussing point; the stop to be used should then replace the one with
which the focus was taken. If a flat object is to be copied, a part of
the subject midway between the centre and side should be focussed
(See Diaphragms.)
on.
If a focussing eye-piece could be held exactly in the place where
the plate should be, a ground-glass screen would not be necessary,
as the image in the air would be visible in the eye-piece. As, how-
ever, the eye-piece cannot conveniently be held in such a position, we
may attain the same result in another way. Take some pieces of glass,
square or circular (such as are used for covering microscopic objects);
carefully clean them, and touch each with a very small quantity of
Canada balsam. Then place them in contact with the ground surface
of the glass, and press gently so that the balsam shall spread just to
232
MANUAL OF PHOTOGRAPHY.
the edges of the glass. After a few hours the edges will have become
dry and the glass will be fixed. We have now a transparent patch of
clear glass through which a very distinct readily focussed image is
visible with the eye-piece. As it is useful to see various parts of the
picture, these little patches of glass may be fixed in different parts of
the screen without in any way interfering with the ground-glass.
Head-Rests. The process of taking a portrait now occupies so short
a time that there is very little necessity for using a head-rest; but
there are some persons who cannot keep their heads perfectly still,
even for five seconds; therefore, a support of some kind is required.
For studio purposes the rest made by Harrison of Leeds is one of
the best. There are various contrivances for attachment to the back of
a chair, but they are all inconvenient. If used at all, the rest should
be on a separate stand. In all cases the pose should be first arranged,
the rest brought into position, and the fork made to touch the head
very lightly; otherwise, the effect will be stiff and unnatural. In
many cases it is sufficient to place the rest against the shoulder.
Hydrometer. The form of this instrument is similar to that
described as the Argentometer. The graduation and use of the
hydrometer is varied by different makers; but the purpose of all
is the same, viz., that of determining the specific gravities of the
fluids in which they are floated.
Instantaneous Shutters. For most purposes dry plates of ordinary
rapidity will be found to work better than the more rapid kinds; and
when slow plates are used (as those working at about ten times the
rapidity of wet collodion would be called), there is no necessity for
any kind of shutter, as the exposure can be made by hand. The
slower plates are more reliable in every way; they are more under
control in the exposure and also in the development; but when
very quick plates are used, some mechanical means must be adopted
for making the exposure. One of the simplest is the drop shutter,
which consists of a frame attached to the front of
the lens, in which there is a movable part having
an aperture, and exposure occurs only while the
aperture passes in front of the lens.
This can
be controlled by sloping the shutter, so that the
drop is lessened by friction, and the fall of the
shutter may be quickened by the tension of an
elastic band.
Another shutter of a simple kind is shown in
Fig. 78. It combines the drop with the flap.
The flap acts as a sky-shade, and, when turned
to a certain point, can be held for time exposures,
while the drop may be accelerated by means of an elastic band.

FIG. 78.

ADAMSON & SON, PHOTOS.
A. BROTHERS
RS & CO., HALF-TONE ZINCO.
THE LORD OF THE ISLES.
INSTANTANEOUS PHOTOGRAPH.
TAKEN WITH
A THORNTON-PICKARD SHUTTER.
APPARATUS.
233
The'“Kershaw” shutter (shown in Fig. 79) is of a different class,
and can be used for time as well as quick exposures, the speed being

O
U
CITY.CO
FIG. 79.
This shutter is very simple in
regulated by means of a spring.
construction and use, and with it objects in rapid motion have been
photographed. One of the most impor-
tant advantages claimed for this shutter
is that it causes no vibration.
Fig. So shows the Thornton Pickard
shutter, adapted for a stereoscopic

camera.
TORNTON PICKARD.
FIG. So.
Out of so great a variety of shutters
it is impossible to say that any one is
the best; all have their good qualities,
and the purpose for which they are re-
quired must determine which should be selected. Those described
are for use outside the lens, but there are others which can be
adapted so as to act in the diaphragm slot. The illustration on the
opposite page is an example of instantaneous photography.
In selecting a shutter, care should be taken that it shall work with-
out causing motion in the camera. Any vibration in stopping the
motion of the shutter can do no harm, but there are other possible
causes of motion which should be looked for.
If it were practicable in all cases, the best place for a shutter would
be inside the camera, either at the back of the lens or in front of the
234
MANUAL OF PHOTOGRAPHY.
plate. For studio-work this can be done, but for landscapes a shutter
is generally used in front of the lens.
One of the earliest of the mechanical shutters was the invention of
the late Mr. Noton of Manchester. In this shutter there are two
metal slides, working in grooves and having diamond-shaped aper-
tures; one of these is in a sliding piece, which, when drawn to the
top, closes the fixed aperture. A spring at the top controls the
motion, which may be quick or slow; and as the top slide falls the
exposure is made. The shutter may be used between the lenses or
outside, as required.
A simple method for adapting shutters to lenses has been patented
by the Thornton-Pickard Company. The illustrations, marked No. 1
LLLLLLL
NT 2 3
4 5
FIG. 81.
PATENT
6 7
THORNTON PICKARDI
FIG. 82.
to 7, Fig. 81, show sections
of the india-rubber moulding,
which is supplied in strips;
these strips can be cut and
applied to the shutter, as
shown in the next illustration,
Fig. 82. The perfect adjust-
ment may be made by rubbing
down the moulding with sand-
paper, or, where the fitting is
too loose, the rim may be
packed with cardboard. This
useful invention removes the
difficulty of the shutter only
fitting one lens. The next
illustration (Fig. 83) shows a
fan which can be adapted to
the Thornton-Pickard shutter,
and which causes it to work


more smoothly and quietly. Another very neat contrivance is a new


FIG. 83.
90
02
FIG. 84.
70
oy
speed indicator (Fig. 84). It shows at what speed the shutter is set,
and it prevents the possibility of over-winding the spring.
APPARATUS.
235
The term "instantaneous" is perhaps convenient to use as applied to
shutters, but it is not correct. Quick or quick-acting would be a better
term. Perhaps the quickest motion used in a shutter is when photo-
graphing the sun, for which an extremely short exposure is requisite ;
the shutter is actuated by a spring which is held by a cord, and is
released when this is burnt through.
When exposures are made with a drop shutter, and the slide
containing the aperture falls by its own weight, the duration of the
exposure may be seen by the following figures :-
In 1st inch the fall is '072, or 4th of a second.
יי
2nd
3rd
" 4th
99
"}
ラン
​029, or th
*023, orrd
019, or nd
62
""
These figures are approximate only, and will be slightly affected by
the friction of the slide; as the height of the fall increases, the
shorter will be the exposure.
Measuring Rapidity of Shutters.-Without mechanical assistance
it is difficult to make exposures in less than half a second, and as
some watches are provided with long seconds-hand and dials marked
to fourths of a second, it is possible to time exposures within such
limits. When, however, shutters are used, it is often desirable to
know at what rate exposures can be made. Many ideas have
been suggested to effect this, and when approximate correctness is
sufficient, the speed of a shutter may be found by means of a swing-
ing pendulum. A clock-pendulum swinging seconds—that is, one
which is thirty-nine inches long from the point of suspension to end.
of weight, will serve the purpose. In the absence of a clock-pen-
dulum, a weight attached to the end of a string thirty-nine inches
long, suspended so that it will swing freely, and provided with a
pointer at the bottom to indicate the distance travelled over the scale
which is to be used in the experiment, will answer very well. The
pointer may be black or white, or, better still, something which will.
reflect the light as a bright point. If the pointer be black, the scale.
must be white (or, perhaps, black divisions on a white ground), and
in the other cases the ground must be black. The scale may be of
any length, following the line of a circle having a radius of thirty-
nine inches. As the pendulum will indicate seconds, whether the arc
be long or short, the scale may be two feet or one foot; in either case
it should be divided into a hundred parts. It is clear that if a photo-
graph be taken of the pendulum while in motion, the portion travelled
over while the plate is exposed will indicate the time of the expo-
sure in one-hundredths of a second. This is merely a rough method
of rating a shutter, but for most purposes it will be sufficient. Care
236
MANUAL OF PHOTOGRAPHY.
must, of course, be taken not to make the exposure until the swing of
the pendulum coincides with the markings of the scale. Allow the
pendulum to swing so that it passes beyond the scale and then
watch till the oscillations fall to the proper distance.
A more correct method is by means of a clock-dial, over which the
long hand is made to travel in one second. This may be effected by
removing the pendulum and increasing the rate of speed as the clock
runs down until the hand just makes one revolution in a second. If,
then, the circumference of the circle over which the hand travels be
marked in one hundred divisions, a photograph taken of the hand
while in motion will show the speed of the shutter.
As in the pen-
dulum method, the dial must be light or dark according to the way in
which it is to be used; on a white ground the point over the end of
the hand must be a dark object, or, if preferred, something to reflect
a bright point of light-a small thermometer bulb will answer the
purpose.
The method of using an instrument of this kind can scarcely need
description. The speed of some shutters is controlled by elastic bands,
others by springs, while others again are affected by gravity alone;
therefore each case must be treated as appears to be necessary.
Iris Diaphragm.-The origin of the iris diaphragm is somewhat
curious. It was originally used, not as a diaphragm, but as a cover
for bottles and preserve-jars. Two rings of metal, one moving within
the other, are attached to a ring of thin india-rubber in such a way
that when one of the metal rings is revolved it causes the india-rubber
to stretch and close the opening. The principle of this was adapted
in 1863 by the writer for the purpose of diminishing the aperture of
a telescope without leaving the seat at the eye-piece end of the instru-
ment. A rod was attached to a pinion and half-wheel at the object-
glass end of the telescope, so that when the handle was turned by the
observer, he could determine when the light of the star was cut off
by the diaphragm, and the size of the aperture could be read off by
means of the scale. This system of diminishing apertures was used
for observing variable stars. It answered perfectly while the india-
rubber remained in good condition, but the varying temperature of
the observatory in time caused the india-rubber to become less elastic,
and it required to be renewed. The principle of the iris as a dia-
phragm was next applied by Messrs. Smith & Beck to the micro-
scope. In this case thin plates of metal were moved by rack-work,
and formed a very neat diaphragm. This kind of iris diaphragm was
next adapted to the photographic lens, and is perhaps quite as con-
venient as the revolving disc of apertures, while it has the advantage.
that the full aperture of the lens may be used, as also all sizes of dia-
phragm down to a pin-hole. The apertures are practically circular.
APPARATUS.
237
Lamps for Dark Rooms.-The necessity for using non-actinic light
while developing plates, and for many other purposes in the practice
of photography, has brought into use many contrivances in which gas,
oil, or candles may be used. For temporary purposes a sheet of yellow
paper may be arranged round the light. In changing plates, it will
be quite safe to use such a light by taking care to be some distance
from it—just sufficient light to see by is all that is necessary.
Some-
times the white light reflected from a ceiling might cause fog; this is
a point to be remembered.
Fig. 85 is a lamp, three-sided, in which gas may be used; Fig. 86
is useful for throwing the light direct on to the plate; and Fig. 87
makes a convenient reading-lamp during lantern exhibitions.



FIG. 85.
FALLOWELELD.
FIG. 86.
FIG. 87.
Electricity may be used, if desired; but there appears to be very
little advantage over oil or candles for a purpose so simple as a lamp
required for occasional use only.
Magnesium wire or ribbon is a convenient source of light for
temporary purposes. A simple form of lamp was contrived by the
writer, and used in his early experiments. It is simple in construc-
tion, being made of tin, and painted white inside, or left bright.
Owing to irregularities in the burning of the wire or ribbon, any kind
of clockwork for regulating the supply of the metal is seldom effective.
It is better to take just so much of the metal as will give the light
required and use it at once.
Level Indicator.---In Fig. 57 (see Cameras) is seen a simple means
238
MANUAL OF PHOTOGRAPHY.
of finding when a camera is upright or "plumb" by using a string.
with weight. Fig. 88 shows a simple "plumb indicator,"
patented by Messrs. Thornton and Pickard.

PATENT
Optical or Magic Lantern. From being little more than
a toy, the "Magic," or, as it is now generally called, the
Optical Lantern, has become a very valuable scientific in-
strument. When oil was the illuminant employed, the
light was, of course, very feeble as compared with the incan-
descence of lime produced by the oxyhydrogen flame, and
hence the increased popularity of the instrument when the
more powerful light became available. With the improved
light came more perfect instruments, and, as now con-
structed, even the cheapest form of lantern is useful. The more
expensive kinds are marvels of construction, ranging from the single
lantern to the "three-decker." When required merely for display-
FIG. 88.

FIG. 89.
ing transparent photographs or simple diagrams, the single lantern
answers every purpose But for "dissolving views "-that is, for the
display of photographs in such a manner that, while one view is
fading away another is taking its place-a pair of lanterns is necessary;
or one lantern with two sets of lenses arranged side by side, one over
the other, or in any other way, so that the images when projected on
to the screen can be made to overlap or "register" correctly, as on
APPARATUS.
239
>>
this greatly depends the success of this method of showing pictures.
When "effects are to be shown, three lanterns are used; not neces-
sarily three distinct instruments, but three sets of the apparatus com-
bined and arranged one over the other in such a way that all three
lights may be used at the same time if desired. Dissolving effects
were first shown with a double lantern in the early part of the present
century, but it was not until photography made it possible to show
something superior to hand-painted slides that the lantern became
popular and valuable for educational and other purposes. The lime-
light was first adapted to the lantern by Mr. J. B. Dancer of Liverpool
(afterwards of Manchester), and the first popular application of the
lantern and dissolving views was made by him, and carried out in a
very successful manner by the Direc-
tors of the Manchester Mechanics'
Institution (now the Technical School).
Views of the monuments of ancient
Egypt, and other photographs, in-
cluding statuary, formed most attrac-
tive exhibitions during several seasons,
and, as displayed by Mr. Dancer's ap-
paratus, established the lantern, not
only as a means of popular recreation,
but as a scientific or philosophical
instrument.
Figs. 89 and 90 show the single form
of lantern.
In the Novelty Lantern, Fig. 92,
an entirely new plan of showing
slides is seen. By using a double slid-
ing stage the pictures are raised or
lowered quickly, and readily changed.
Much of the success in using the
optical lantern for the display of pho-
tographs, or for various lecturing pur-
poses, depends on the manipulation of
the apparatus. All lecturers have seen
the importance of this, and one of the
most successful "lanternists," Mr. H.
M. Whitefield, has superintended the
construction of a "single" lantern for
the Manchester Photographic Society,
in which some improvements of his
own have been carried out.

FIG. 90.
As to the jet, this is usually placed loose on a pillar, and requires
240
MANUAL OF PHOTOGRAPHY.
adjustment, being capable of motion in all directions. In addition to
the difficulty of fixing the jet when the pillar and set-screw have become
worn, there is always the liability of displacement by accidentally mov-
ing the india-rubber tubing during use. In this lantern the jet is fixed
on a sliding plate central with the optical system, and the only move-
ment possible is to and from the condenser parallel to its axis; this
is all that is necessary, whatever objective or size of disc is employed.
As to the stage, this is constructed quite open at the top, so that
a tank, or other piece of apparatus, can be inserted from the top as
well as pushed through, and also provided with a set-screw to clamp
a carrier in position. The stage is set off from the condenser to assist
evaporation of the moisture which sometimes forms on cold slides;
and by turning a button the whole of the stage can be removed to
allow of other apparatus being used, and to permit the withdrawal of
the condenser without disturbing the limelight.
As to focussing, to effect this conveniently the milled head of the
rack should be convenient to the hand; in this lantern this is brought
close under the stage, but the ordinary rack-work is retained on the
objective.
With respect to the objective, a fault in lanterns when long focus
lenses are necessary is that draw-tubes are used, and there is a
tendency for the weight to cause the front part to drop. In this
new lantern the lens-tube is carried by an independent support, and
thus the defect referred to is removed. This part can be entirely
removed to permit other apparatus to be used.
The aperture at the back for the insertion of the jet is so arranged
that the light is trapped without a curtain, and the lime-burner and
stopcocks are readily accessible. A flat top may be used over the
lantern, on which slides may be warmed when necessary.
As to the kind of screen to be preferred, while paper mounted
on a roller makes an excellent surface on which to exhibit photo-
graphs, the kind known as continuous cartridge is as good as any
other, and can be obtained 4 feet wide, so that when a small disc
will suffice no joining is necessary. For all large screens white
calico becomes necessary, and when strained will give a very satis-
factory surface.
The lantern is now often used for other purposes than for the
display of ordinary photographs. Microscopic objects, when very
minute, require a more powerful light than the incandescent lime will
give, and the display of experiments with the spectroscope also re-
quires a very strong light. For this purpose the electric light is now
available in a form which a few years since was not thought of. The
use of batteries is now seldom resorted to, and, excepting in colleges,
the direct production of the light by means of the dynamo is not prac-
APPARATUS.
241
ticable on account of the cost, but, as electricity can now be stored
in what are termed accumulators, the electric light becomes available
for lantern purposes.
When the electric light is used, the lamp
must be capable of adjustment so that the carbon points may be kept
central with the condenser.
It may be stated here that a very interesting experiment in pho-
tography may be shown with the limelight and lantern by projecting
the spectrum on to the screen and exposing one-half of a plate under
a negative in the red end of the spectrum and the other half in the
blue rays, when it will be found, on developing the plate, that there
has been no effect in the red light, while the blue has printed the
picture. The time of exposure must depend on the strength of the
light. This experiment is generally thought to be possible only with
the electric light; but the writer has tried it successfully with the
limelight, and as a lecture-experiment it is very effective.
Photographs on paper and other opaque objects may be exhibited

OPTIMUS
L
FIG. 91.
by the limelight when the lantern is adapted with an arrangement
for reflecting the light instead of transmitting it in the usual way.
When the limelight is too close to the condenser, the heat is
sometimes too great, and causes fracture of the glass. This may
happen, also, if the lime is allowed to pit, as the heat is then focussed
on one part of the condenser, and is almost certain to cause fracture.
This may, to some extent, be avoided by arranging a piece of thin
patent plate glass between the light and close to the back of the con-
lenser. This thin glass will break if the heat is too great, and the
aoise of the fracture will give warning of what is wrong.
It is quite unnecessary here to go into the question of condensers,
jets, dissolvers, back-pressure valves, gas bags and bottles, and all
the other details connected with the use of the optical lantern; but
in Figs. 91, 92, and 93 are shown some appliances which will be found
useful. Fig. 91 is an interchangeable jet. which, by a screw-collar
arrangement, can be converted from a jet of high pressure to one of
Q
242
MANUAL OF PHOTOGRAPHY.
the safety or blow-through pattern. Fig. 92 shows a triple dissolving
CH
OPTIMUB
PATENT
FIG. 92.
arrangement for use with the bi-unial or triple
lantern, and is so arranged that whereas for-
merly three taps had to be used with the triple
lantern, the work is done with one, which gives
the operator perfect control over the lantern.
The tap is fitted with bye-passes.
When the lantern is employed to display photographs in a room
of ordinary dimensions, a screen from four to nine or ten feet diameter
is quite sufficient. The kind of lantern to be used must be deter-
mined by the purpose for which it is required; generally, the single
form will be sufficient. The size of the condenser must be con-
sidered and the quality of the lens, as upon these and the light
depend the success of the projected pictures.
When it is not intended to use the oxyhydrogen light, the form of
lantern known as the Sciopticon is a very good substitute, and with
it (using an oil lamp) photographs may be shown with good effect
from six to ten feet in diameter.

OPTIMUS
FIG. 93.
In using oil, inconvenience sometimes arises from the wicks not
being properly trimmed. Fig. 93 shows a wick-
trimmer, by which a clean edge is given to the wick.
It will often be found preferable to rub off the charred
wick, but when it must be cut, the edge should be
perfectly regular, or the flame will be imperfect.
Oscillating Tables or Rockers.-The necessity for keeping the
developing solution in motion when dry plates are undergoing de-
velopment is a somewhat tedious operation when the motion has to
be given by hand. The oscillatory motion may be obtained by means
of a pendulum to which a heavy weight is attached; the other end
of the pendulum-rod must be fixed to a board in such a way that
when set in motion the rocking will be conveyed to the solution in
the developing tray resting on the board, so that the wave will be
carried over the plate as when the tray is held in the hand. At the
point of suspension there need be very little friction, and when the
"bob" or weight is tolerably heavy, the
rocking motion will be continued longer
than is required for one plate; while a
slight touch with the foot will keep up
the motion as long as necessary. Clock-
work has been used for the same purpose.
Lewis & Co. of Birmingham have a con-
trivance of this kind, which is shown in
Fig. 94.


FIG. 94.
Pantascopic Camera.-Under this name a camera was introduced
APPARATUS.
243
by its inventor, Mr. J. R. Johnson, for the purpose of taking pano-
ramic views. The pictures were taken on flat plates, and could be
made to embrace any angle of view. Specimens which the writer
has seen were very successful, and the definition as good as in views
taken in the ordinary way. Very little has been heard of this, or
any other kind of camera for taking pictures of the panoramic
kind during the last few years, probably because single pictures have
a more pleasing effect than those with a range of view which the eye
cannot embrace at once.
Photometers (see Actinometers and Exposure Tables). In addi-
tion to what has already been said on the subject of exposure tables
and actinometers, it may be mentioned that Mr. Woodbury invented
an instrument called a Photometer, differing only in name from an
actinometer, the principle being very similar in all such aids to
exposure. Captain Abney suggested that, in using silver bromide
plates, the paper used in the photometer should be thus prepared
with silver bromide :-"Take a sheet of plain photographic paper,
and soak it for ten minutes in a solution of potassium bromide
(40 grains to the ounce); hang it up to dry, and float it on a 50-grain
bath of silver nitrate. I should then wash and
I should then wash and pass the paper
through a bath of potassium bromide of 5 grains to the ounce. would
then wash thoroughly, and finally give a soak for five minutes in a
bath of tannin (1 grain to the ounce)." To use this paper in Wood-
bury's photometer the tints would have to be repainted.
Plate-Boxes. For storing and preserving negatives, boxes made
of pine wood with grooves are perhaps better than any others,
but they occupy much space. In the days of wet collodion the
convenient cardboard boxes were not available; but, with paper
between each negative, there is, perhaps, no better way of pre-
serving negatives than by keeping them in the boxes supplied with
the plates.
Plate-Rack.—A rack of some kind in which to put plates to drain
or dry is necessary, or rather is to be preferred to standing the plates
on blotting-paper, as there is less chance of injury from dust collect-
ing through capillary attraction. Pieces of grooved wood attached
to side-pieces, so as to form X-shaped legs and side supports at the
same time, can readily be made; and, if necessary, the sides may be
made to fold.
Pneumatic Plate-Holder.-For holding plates of any size over
8 x 6 it is convenient to use the pneumatic holder. It consists of
an india-rubber disc, attached to a vulcanised india-rubber ball, con-
tained within a wooden case. On pressing the ball with the thumb
while the plate rests on the india-rubber the plate becomes firmly
attached when the thumb is removed. Care must, of course, be
244
MANUAL OF PHOTOGRAPHY.
taken that the glass is secure when large plates are used. Pressure
on the ball at once releases the plate.
Printing Frames. For small work, frames without glass may be
used for printing. The negative is placed face uppermost, with the
prepared paper upon it in the frame, when, the back being put into
its place, the light pressure from the spring is sufficient to make per-
fect contact, and there is very little danger of breaking the negative;
but for larger work a stronger frame becomes necessary, with thick
glass upon which to place the negative, and stronger springs must be
used. For still larger work, screws must take the place of springs to
bring the paper into perfect contact, and in cases where very great
pressure is needed, the frames must have glass at least half an inch
thick. The pressure from the screws should be released as soon as
convenient, as prolonged strain on the glass may lead to fracture, par-

FIG. 95.
ticularly with a change of temperature. A frame should never be left
all night without the screws being loosened.
Frames for special purposes have been contrived. When printing
on opal glass from a glass negative it is necessary to examine the pro-
gress of the prints. This is effected by fixing the opal to one part of
the frame and the negative on the top, so that when the top is lifted
it can be replaced in exact position. Special frames are also made for
vignetting, but these are scarcely necessary, as will be seen by reference
to what is said under the heading Vignetting. Fig. 95 shows a simple
form of printing frame. Some annoyance by the breaking of the plate-
glass will be avoided by taking care that the glass has a good bed on
the rim of the frame, and in large frames india-rubber between the
glass and frame-bed is a good protection against unevenness. The
india-rubber may be purchased of about the size of stout picture-cord
and round in section, and may be glued to the frame.
APPARATUS.
245
Retouching Desk.—Some kind of desk is very useful for stopping
out skies and removing defects in negatives. Fig. 96 shows one of
the forms in general use. When placed in a good light, a sheet of
white paper is usually sufficient to reflect light. It may be necessary
to throw a dark cloth over the head and top of the desk when using it.
Roller-Slide. The substitution of sensitive paper and films for
glass made it possible to use either in a continuous sheet or roll, so
that, as required in the camera, after each exposure, another portion
of the film could be brought into use; and mechanical means were
devised in many ways for superseding the ordinary dark slide. The
roller-slide—that is, a roll within the camera-is charged with a length
of the paper or film sufficient for many exposures, and as used is
wound on to another roll until the entire length has been utilised.

FIG. 96.
The Eastman Roll-Holder is a device by which a transparent film
is used instead of glass.
Sky-Shade. The hood of a lens is seldom sufficient protection
from extraneous light; hence, when required out of doors, or in a room
having top light, some kind of shade should be used; and the hand
will often be sufficient. Care should be taken that no part of the
lens is covered.
Solar Camera.-In countries where the direct light of the sun is
available with more certainty than in England the solar camera is a
useful instrument in the hands of the photographer. As its name
implies, the direct solar rays are used for the purposes of printing and
enlarging. The instrument is of American origin, and was invented
by Mr. Woodward. It consists of a box which can be fixed so that
a reflecting mirror is outside, and the remainder of the apparatus.
inside a darkened room. The reflector has a rack motion, so that it
246
MANUAL OF PHOTOGRAPHY.
can be kept turned towards the sun in such manner that the rays are
made to pass through a condensing lens of large aperture. At a
point within the camera the negative is placed, with means of adjust-
ment. The sun's rays pass through the condenser and negative to the
enlarging lens, and thence to an easel arranged to hold the sensitised
paper or plate. This apparatus can be used for "printing out" as
well as for other enlarging purposes, but unless continued sun-
shine can be depended on, other methods of enlarging will have
the preference.
Squeegee. A strip of vulcanised india-rubber attached to strips of
wood to form a handle is a convenient means of causing intimate

FIG. 97.
contact between prints and glass, paper, or cardboard. The india-
rubber in the form of a roller may also be used.
Stoppers. From various causes glass stoppers in bottles occa-
sionally become fast. The best method for their removal depends
on the cause of their being fast. If the contents of the bottle are
adhesive, a solvent, warm water in most cases would be sufficient, and
may be applied. If the thumb of the left hand be placed against a
tight stopper, and then it is gently tapped with a piece of wood, the
glass will be released. If the bottle be held with the stopper between
a door partly open and the door jamb, a gentle turn will often loosen
the stopper. In some cases a drop or two of oil may effect the same
purpose, if left for a time.
APPARATUS.
247
Bottles con-
A reverse operation is to keep a stopper in a bottle.
taining ether or ammonia should be looked at occasionally. If rubbed.
with a little vaseline, there is less chance of the stopper being forced
out.
Tents.—In cases where it is necessary to develop plates away from
home, and no convenient place may be found fit for the purpose, the
portable tent supplied by Messrs. Houghton & Sons, and shown in

FIG. 98.
figs. 97, 98, and 99, would be found very suitable. The wood-
cuts are sufficiently explanatory. There are many forms of portable
tents to be obtained, but the principle is the same in all; they must
be as light and strong as possible, and compact.
For changing plates of small size a black bag large enough to hold
the plates, dark slide, and the hands answers every purpose, as the
touch enables the difference between the two surfaces of the plates to
be detected. In other cases the bag is contrived so that by means of

FIG. 99.
sleeves and apertures covered with non-actinic glass the operator can
see what he is doing. (See Dark Slides and Changing Boxes under
Camera.)
Thermometers.-For the purpose of ascertaining the changes of
temperature the instruments called thermometers are used. Metals
and gases expand on the application of heat, but the change in metal
is too small, and in gases too great. The liquids mercury and alcohol
248
MANUAL OF PHOTOGRAPHY.
are generally used. The range with mercury is very large, hence it
is usually employed; but as alcohol cannot be frozen, that fluid is
used when very low temperatures are to be measured. In England
and America the Fahrenheit scale, in France the Centigrade, and
in some other countries Reaumur's scale is employed. Fig. 100 shows
the different methods of marking :-
212_ 100_
80__Water boils.
32_
o Freezing.
F. C. R.
FIG. 100.
The various scales may be reduced as under
Centigrade to Fahrenheit :-Multiply by 9, divide by 5, and add
32; as, 100° C. × 9 ÷ 5 + 32
=
212° F.
Fahrenheit to Centigrade :-Subtract 32, multiply by 5, and divide
by 9; as, 212° F. – 32 × 5
5÷9 100° C.
Centigrade to Reaumur:-Multiply by 4 and divide by 5.
Reaumur to Centigrade :-Multiply by 5 and divide by 4.
Reaumur to Fahrenheit:- Multiply by 9, divide by 4, and add 32.
Fahrenheit to Reaumur :-Subtract 32, multiply by 4, and divide
by 9.
Trimming Prints.-A sharp knife is the best instrument to use
for trimming prints. A sheet of glass, cut to the size the print is
required to be, serves as a convenient guide for the knife, and en-
ables the proper position to be seen. A thick piece of plate-glass
serves as a bed on which to cut the prints, or a sheet of zine may be
used for the same purpose. Glass is preferable, as it is only after
very long use that the surface be-
comes scratched, whereas every cut
with the knife leaves a mark on the
metal plate. Prints of large size
must be carefully squared and then
cut, using a straight-edge to guide
the knife. The little tool shown in

R
AMERICAN BRAND C
LONDON.
FIG. IOI.
Fig. 101 may be used as a print-
trimmer, and is very useful for cutting paper while wet.
View-Finder. When photographing moving objects, it is neces-
sary to have some means of knowing where the object will appear on
the plate. The simplest method is to have two points, one on the
APPARATUS.
249
front of the camera and the other on the back, so that the two points
and the object to be photographed may be seen in line.
Many contrivances are in use for keeping objects in view and for
measuring the shape of the picture to be taken. Fig. 102 shows one
of these little instruments. It can be carried in the pocket and
attached or detached from the camera at will. It forms its image on a


FIG. 102.
T.T.& H
FIG. 103.
ground-glass screen, viewed from above, and is especially designed for
hand-cameras. Fig. 103 is another form.
If every landscape photographer could carry in his pocket what is
called a
"Claude Lorraine Mirror" he would have a view-meter of a
very perfect kind; but, in the absence of this, an oblong aperture cut
in a piece of cardboard and held at such a distance from the eye as
would about include the same angle of view as the lens to be used,
would give a good idea of the appearance of the finished picture.
The view-meter is useful as showing, without the trouble of erecting
the camera, what the "composition" of the picture would be.

FIG. 104.
Washing Apparatus.-Many contrivances have been used for
saving trouble in washing prints. This part of the photographer's
work may be the least interesting; but it is certainly one of the most
important, as upon its being properly done depends to a very large
250
MANUAL OF PHOTOGRAPHY.
extent the permanence of his work. Running water is usually
recommended for washing prints. This is not only wasteful, but
cannot be effectual unless the prints are constantly separated, as the
motion of the water is certain to cause the prints to become matted
together; consequently there can be very little circulation of the
water between the prints. One of the oldest and best methods of
washing prints is not to leave too many in one dish, to change the
water at least a dozen times in the course of ten hours, and to turn
each print over at each change of water. By this means it will be
seen that each print has been turned. As the toning and fixing are
usually not done till late in the day, the prints should have several
changes of water, and then be left in the dishes until the next morn-
ing, when they may be again washed several times. Finally, each
print should be laid on a sheet of glass, and sponged with warm
water. The experience of many years, and the possession of unfaded
prints which are at least thirty years old, the writer considers some
proof that, when the greatest care has been taken in washing and
mounting prints, they do not necessarily fade. Causes of fading,
difficult to discover, arise in other ways, and, unless every care be
taken in the proper washing of prints, there is much probability that
they will change colour, it may be in a few weeks, or it may be
months or years. Fig. 104 shows a simple form of washing-trough.
For washing gelatine plates grooved zinc boxes are generally used ;
and when the water is changed frequently, or by allowing a gentle
stream to pass through by means of a syphon, so that the bottom
water may be drawn off, this mode of washing answers every purpose.
Large plates may be washed in flat dishes, or by allowing water to
run over the surfaces of the negatives. If placed face down in a
vessel, which will allow plenty of water below, the fixing agent will
be washed out more effectually than by any other meaus, as the
denser fluid will fall to the bottom of the vessel.
PART IV.
MATERIALS USED IN PHOTOGRAPHY.
Acetic Acid (C2H4O₂, also called Pyroligneous Acid, Vinegar).–
This acid in a dilute form is commonly known as vinegar. It is
obtained by the oxidation of alcohol and by the dry distillation of
wood, in which case the crude product is called pyroligneous acid.
The pure acid is obtained by heating sodium acetate with strong
sulphuric acid, forming a colourless fuming liquid which boils at
118° C. (245° F.), becomes a white crystalline solid at 17° C.
(62.5° F.), and in this state is called glacial acetic acid. It mixes
with water in every proportion. The glacial acid is the form gene-
rally used in photography, but the commercial acid is sufficiently
pure for some purposes, and may be used in the developing solution
for the collodion process, in which it acts as a restrainer, and also
facilitates the flow of the solution over the surface of the collodion.
It is also used as a solvent for gelatine, one part of which dissolves
in five parts of the acid. A mixture of glacial acetic acid and alcohol
is also used for dissolving pyroxylin.
Acids. The acids used in photography are referred to in alpha-
betical order. Of acids generally it may be said that they are nearly
all soluble in water; that they have a pungent
"acid" taste; they
change the colour of blue litmus paper to red, and form with metallic
oxides a series of compounds termed "salts;" but these properties,
though characteristic, are possessed by the different acids in very
varying degree. Care must always be taken in the manipulation of
acids, as, although not in reality "poisons," their corrosive and
inflammatory action is, in most cases, such as to cause death when
introduced into the stomach. When clothes are marked by acids
falling upon them, the stain may best be removed by immediately
adding ammonia. When strong sulphuric acid gets spilt, it is better
to add a considerable quantity of cold water before attempting to
remove the mark by means of ammonia.
Albumen.-Albumen is an organic substance found in the blood
and muscle of animals, and also in vegetable matter.
For photo-
251
252
MANUAL OF PHOTOGRAPHY.
graphic purposes the white of eggs, in which it is found in a very
pure state combined with water, is generally used. Liebig's analysis
gives :-Carbon, 53.5; hydrogen, 7.0; nitrogen, 15.5; oxygen, 22.0;
sulphur, 1.6; phosphorus, 0.4 100. Phosphoric acid is an impurity,
and the analysis then is :-C. 53.6, H. 7.0, N. 15.6, O. 22.2; S.
1.6 =
= 100.
=
Albumen is soluble in water, but on heating the solution to
60°-70° C. (150° F.) the albumen becomes insoluble, and separates
out in large flocks of the coagulated substance. If the albumen has
been diluted, the heat necessary to coagulate it will be higher, accord-
ing to the state of dilution, the action being in all cases complete on
reaching the boiling temperature. Albumen may also be coagulated
by the addition of nitric acid, some metallic salts, and in other ways.
The action of metallic salts is usually accompanied by the forma-
tion of so-called albuminates. Silver albuminate is the most impor-
tant of these photographically, as it is formed when the albumen paper
is floated on the silver bath. On account of its solubility in water,
care must be taken in using albumenised paper that the silver bath is
not too dilute, for in this case the albumen coating will be dissolved
wholly or in part before it can be coagulated by formation of the
silver compound.
Albumen is utilised in many photographic processes, but chiefly in
the preparation of paper for printing, to which it gives a high gloss,
valuable for keeping the picture on the surface of the paper. Its uses
in various other ways are referred to in the processes described. It
quickly decomposes, but the addition of ammonia acts as a preservative.
Albumenised Paper. Until the introduction of the platinotype.
and other methods of printing photographs, paper prepared with a
surface of albumen was almost exclusively used in photographic
printing. If without preparation, or plain, as it is termed, the sur-
face is dull or matt, but with albumen the picture is prevented sinking
into the paper, and consequently has a bright appearance, and this
brightness depends on the quantity of albumen on its surface. The
paper may be used coated with albumen twice if a highly glazed
surface is required.
Very few photographers now sensitise their own paper, as it can be
purchased of excellent quality from the dealers ready sensitised; at
the same time it may be remarked that better prints can be made on
freshly prepared paper.
As effects can be obtained on the albumen surface which are some-
what different from any other, this kind of paper will probably always
be in demand. For experimental, if not for commercial, purposes it
is useful to know how the paper is prepared. The albumen of fresh
eggs should be used. The eggs are broken separately in a cup, and
MATERIALS USED IN PHOTOGRAPHY.
253
the yolks carefully removed. To each ounce of the albumen 5 or
10 grains of ammonium chloride are added. Other salts, such as
those of barium or sodium, may be substituted; but the ammonium
salt is to be preferred, as the silver solution used in sensitising is not
discoloured when this is employed. Add 1 drachms of alcohol, and
water to make up to two ounces.
The albumen must be thoroughly
beaten into a thick froth. The salt should be added some hours pre-
viously, and then allowed to settle. After filtering through cotton
wool or lint, the albumen should now be poured into a clean dish, the
paper floated upon it for two minutes, and then hung up to dry. The
paper is better when dried quickly; therefore the temperature of the
room should be sufficiently warm. To float the paper requires a little
skill, and the tyro will find it better to use half or quarter sheets,
taking the paper by opposite corners; the bent sheet is brought into
contact with the albumen and gradually lowered, then gently raised,
and any air bubbles removed. The surface is improved by rolling.
The paper should be stored in a dry place.
Paper with a very high glaze may be made by what is called
"double albumenising." The first coat of albumen must be coagu-
lated by steeping in, or floating on, a mixture of methylated spirit.
and water, four parts of spirit to one of water. The operation of
floating on the albumen may be repeated when the paper has been
dried.
It is said that paper with a very highly glazed surface may be
obtained by using albumen which has been fermented.
Alcohol (C,HO.)-This spirit is seldom used in photography
in its pure or anhydrous form. The commercial, so-called absolute,
alcohol, contains about 5 per cent. of water. The trade name of alcohol
depends upon its strength and purity, the former being determined
by the amount of water it contains. Proof spirit contains 49.2 per
cent. water to 50.8 per cent. alcohol, while methylated spirit is strong
alcohol, to which 10 per cent. of wood-spirit has been added.
*
Alcohol is obtained by the fermentation of solutions containing
saccharine matter. The fermented liquid is distilled, and the dilute
aqueous spirits of wine is concentrated by re-distillations which, how-
ever, cannot reduce the water contents below 10 per cent., the last
portions having to be removed by distillation over such bodies as
quick-lime or potassium carbonate, which combine with and retain
the water. A 95 per cent. strength suffices for the many purposes in
which alcohol is employed in photography. In the collodion process
it is one of the solvents for the pyroxylin in making collodion, and it
is used to cause the developing solution to flow evenly. The ether
* Since this was written, new excise regulations have come into force.
See Methylated Spirit.
254
MANUAL OF PHOTOGRAPHY.
in the silver bath causes the sensitised collodion to resist water, and
the alcohol becomes necessary to counteract this.
For many of the varnishes required in photography, alcohol is largely
employed as a solvent for the gums and resins used in making them.
A very useful property of alcohol is that it takes up water, and
mixes with it in all proportions; for, as gelatine plates dry very slowly
after they are developed, immersion in methylated spirit absorbs the
water, and the plate becomes dry in a few minutes.
Pure alcohol has a pleasant smell, and the presence of impurities,
that is, fusel oil, can be recognised by the disagreeable odour when
the spirit is volatilised. The purity of the alcohol for some photo-
graphic purposes is very essential; and that used for collodion, or in
the gelatine emulsion process, should remain clear when warmed with
a few drops of ammoniacal silver nitrate solution.
Methyl Alcohol (CH₂OH).-Wood spirit is prepared by the dry
distillation of wood. The pure alcohol is used as a solvent for certain
colours more readily soluble in it than in "ordinary" ethyl alcohol,
as in the preparation of strongly coloured sensitising solutions for
Alberts' colour.
Alpha Paper.-Paper coated with gelatine, which contains a
mixture of silver chloro-citrate and bromide, is known as Alpha
paper. The prints may be obtained by exposure to artificial light,
the exposure being about three times longer than is required for
bromide paper. Excellent results may be obtained by following the
formulæ given by the makers of this kind of paper.
Aluminium.—(Al. Atomic weight = 27.)--One of the lightest of
the metals. It was at one time thought that it might be used with
advantage where brass is now almost exclusively employed; but its
use for such purposes has hitherto been limited.
Amber. The only use for this
the form of varnish, which may be
dissolved in benzole or chloroform.
a very hard surface.
fossil resin in photography is in
applied cold. The resin may be
It has the advantage of forming
Ammonia (NH₂, Spirits of Hartshorn).—As employed for photo-
graphic purposes the volatile gas, ammonia, is dissolved in water, and
is usually called liquor ammonia fort., the specific gravity of which
should be .880, its richness in ammonia being greater the less its
specific gravity. Unless very carefully kept in stoppered bottles, the
gas at ordinary temperatures escapes, as may be detected by the
stopper flying out of the bottle. This may be prevented to some
extent by rubbing the stopper with vaseline. If diluted to half
strength, by the addition of water, the tendency to force out the
stopper is lessened; but it must be remembered when required for
use that the alkali has been diluted.
MATERIALS USED IN PHOTOGRAPHY.
255
Ammonia is now generally prepared from the ammoniacal liquor
formed in the manufacture of coal-gas.
The alkali is employed as an accelerator in developing gelatine
plates with pyrogallol. It may also be used as a fixing agent, as
described in the article on Printing on Canvas; and other uses to
which it is applied will be referred to in the descriptions of the vari-
ous processes. Ammonia is also used in fuming albuminised paper.
Ammonium Bichromate ((NH4) Cr₂O7).—This salt may be used
in some cases instead of the potassium bichromate. It is said to be
more sensitive to light when combined with gelatine.
Ammonium Bromide ((NH4) Br).—This salt is largely used as a
restrainer in the development of gelatine plates. It is also used in
the emulsions for dry plates, both collodion and gelatine, when,
acting on the silver nitrate combined in the film, silver bromide is
formed.
4
2
2
2
Ammonium Carbonate (Sesquicarbonate of Ammonia, Sal Vola-
tile, or Smelling Salts).-The common commercial sesquicarbonate
of ammonia may be considered as a compound of acid ammonium
carbonate, NH HCO3. with ammonium carbamate, NH₂CO₂NH4, and
may be written (CO2) (NH3)3 H₂O. It is made by heating a mixture
of ammonium chloride and chalk, when the ammonium carbonate
forms a white sublimate smelling of ammonia. This evolution of
ammonia permits of its use instead of ammonia for fuming albumen
paper, for which purpose the bicarbonate is valueless, as it does not
evolve ammonia in the air. It is sometimes used in developing
solutions for dry plates, but it is not found to be so suitable as
liquor ammoniæ.
Ammonium Chloride (NH4Cl, also called Muriate or Hydrochlo-
rate of Ammonia, Sal Ammoniac).-This chloride is largely used in
the preparation of albumenised paper. It has the advantage that the
solution of silver does not change colour, as is the case when some
other salts are used. Mercuric chloride is soluble in water; but
when ammonium chloride is added, much more of the mercury salt is
dissolved; and advantage is taken of this in making strong solutions
of the mercuric chloride when used for bleaching collodion plates (the
double chloride of mercury and ammonia is formed). Ammonium
chloride is also used in the preparation of chloride emulsion.
Ammonium Iodide (NHI).—The chief use of the iodide of am-
monium is in the preparation of collodion, in which it usually forms the
iodiser, as it is readily soluble in alcohol and ether.
Ammonium Nitrate (NH4NO3).—When collodion is iodised with
ammonium iodide, the nitrate of ammonium is gradually formed in
the silver bath, but its presence is usually disregarded. Care should
be observed in using the dry form of ammonium nitrate, since, when
256
MANUAL OF PHOTOGRAPHY.
silver is combined with it, the dangerous fulminate of silver, which
is one of the most violent explosives, may be formed.
When water is added to ammonium nitrate, cold is produced; and
advantage may be taken of this when it is difficult to develope dry
plates in hot climates. The dish containing the plate to be developed
is placed in the moistened salt, which is held in another dish; and,
by evaporating off the water, the ammonium salt is recovered, and
can be used again. The process can be repeated as often as required.
Ammonium Oxalate ((NH4)2C2O4).—Oxalic acid, when neutral-
ised with ammonia, forms ammonium oxalate. This salt is used in
some of the formulæ for platinotype printing.
Ammonium Sulphide ((NH4)2S; also called Sulphuret of Am-
monia).—The chief use of this form of ammonia is in blackening the
films of collodion which have been bleached in the lead solution de-
scribed under the heading Intensifying. It may also be used for the
same purpose when mercuric chloride has taken the place of lead
nitrate.
Ammonium Sulphocyanate (NHCNS; also called Sulphocy-
anide of Ammonia).-Used as a toning agent for prints on gelatine-
chloride paper when mixed with sodium thiosulphate and carbonate.
It may also be used as a fixing agent in place of sodium thiosulphate;
but there is no advantage gained. The salt is very deliquescent.
2
Anglol (C₁0H5NH₂OH₂SO3).—This substance was discovered by
Professor Meldola. Its use in photography has been superseded by
eikonogen, which is the sodium salt of anglol.
Aniline (CH, (NH₂), Amido-benzene, Phenylamine).—Aniline
is one of the most important bodies in the formation of various
colouring matters. It is a coal-tar derivative, and forms a very
poisonous liquid, which is usually coloured brown. Its use in pho-
tography is chiefly confined to the preparation of orthochromatic
plates in which cyanin is used, and in the manufacture of this aniline
is employed. (See Aniline Printing Process.)
Animal Charcoal-The charcoal formed when horn, bone, or
other animal matter is carbonised may be used to clear solutions of
silver nitrate which have become discoloured by contact with organic
impurities, as in sensitising albumenised paper. As this charcoal con-
tains phosphates and other salts, and as these tend to weaken the
silver solution, it is better to use kaolin, which effects the same
purpose as the charcoal.
Aqua Regia, or Nitro-Hydrochloric Acid.—When four parts of
hydrochloric acid and one part of nitric acid are mixed together, the
mixture is termed aqua regia from its power of dissolving the noble
metals, such as gold and platinum; this power is increased on using
the acid warm. The solvent power of the mixture depends on its
MATERIALS USED IN PHOTOGRAPHY.
257
1
containing free chlorine. Aqua regia is used to dissolve gold, when
it forms the trichloride of that metal.
14
Aurin, or Corallin (C9H1,O,, also called Rosolic Acid).-It is made
by heating phenol and anhydrous oxalic acid with sulphuric acid. The
only use for this substance to the photographer is as a dye for making
fabric suitable for excluding white light.
Barium Bromide (BaBr₂+ 2H,O).-The bromide and iodide of
barium are used in formulæ for the manufacture of collodion, and the
chloride is sometimes used instead of ammonium chloride in salting
albumenised paper.
Barium Chloride (BaCl2 + 2H,O).—This salt may be used in the
preparation of paper for photography in place of the other chlorides
more commonly employed.
Barium Nitrate (Ba(NO3),).-This substance may be used in the
developing solution for wet collodion combined with ferrous sulphate,
but is seldom employed. It prevents pin-holes.
Benzene (C.He, also called Benzol).-A colourless volatile liquid
with characteristic odour. It boils at 80.5° C. (177° F.) and is very
inflammable. It is used as a solvent for caoutchouc and asphalt, and
a solution of amber in benzene may be used as a cold varnish.
Benzolene. A mixture of benzene naphtha and benzene is known
as benzolene or petroleum spirit. It may be used as a solvent for
some of the gums, and for removing grease spots.
Bitumen (also called Asphaltum, Jew's Pitch, or Bitumen of Judæa).
-The various uses for this substance will be found under the head-
ings of the processes in which it is employed. In its crude state
bitumen is not suitable for photographic printing, and must be puri-
fied as described under the heading Bitumen Process.
I
Borax (Na, B, O,+ 10H,O. Sodium Biborate).-Occasionally used
in toning-formulæ for photographs on paper.
Bromine (Br. Combining weight, 79.75. Sp. gr. 3.18). The
various salts of bromine are used extensively in photographic pro-
cesses. This element resembles chlorine in its properties and com-
pounds. It is a reddish black heavy liquid, very volatile and
poisonous.
Cadmium Bromide (CdBr, + 4H,O).-A white crystalline efflores-
cent salt. One part of the bromide dissolves in three to four parts of
alcohol, and in sixteen parts of a mixture of alcohol and ether. It,
like the iodide, forms double salts, and is used in some formulæ for
the preparation of collodion.
Cadmium Iodide (CdI..)-Cadmium readily forms double salts,
and the double ammonium-cadmium iodide (CdI½ + 2NH¸I + 2H¸O)
has been used for iodising collodion.
Calcium Chloride (CaCl2 + 2H2O. Muriate of Lime).—The anhy-
R
258
MANUAL OF PHOTOGRAPHY.
drous chloride is a white porous substance. It is very deliquescent,
and on this account is chiefly used in photography for the purpose of
absorbing moisture. In its dry state it is kept in the tubes in which
platinotype paper is stored. After it has been in use for some time,
it becomes wet; this moisture may be driven off by applying a strong
heat. As the salt is cheap, it is better to use fresh than to attempt
to dry the old stock. The salt is used in the preparation of plates
for the collotype process and for other purposes.
Canada Balsam.—This substance has a limited use in photography.
It is a resin obtained from the Pinus balsamea, which grows in Canada
and North America. It hardens on exposure to the atmosphere ;
and, reduced with turpentine, is used in cementing lenses together,
and occasionally in varnish.
Celloidin.—This substance is pure gun cotton, and is prepared by
Schering for making collodion, in place of the ordinary pyroxylin.
The advantage of celloidin is that its composition is uniform, as
impurities, such as dextrin, xyloidin, &c., are removed.
Celluloid. (See Film Photography).
Cellulose ((CH1005)).—Pure cellulose is obtained by boiling linen
and cotton fibre (cotton-wool, paper, &c.) with dilute caustic potash,
and then extracting with alcohol and ether. A short immersion in
strong sulphuric acid converts cellulose into parchment paper, and
nitric acid oxidises it to oxalic acid; but a mixture of the two acids,
produces gun cotton, or pyroxylin, the latter of which forms collodion,
when dissolved in ether and alcohol.
2
6
Chloride of Lime, or Bleaching Powder.-The approximate formula
is CaCl2 + Ca(OCI)² + CaO + 3H¿O = Ca¸HC140. It is made by pass-
ing chlorine gas over dry slaked lime in a series of chambers. A pro-
duct containing at least 35 per cent. "available chlorine" should thus
be obtained. Bleaching powder may be used with gold chloride as a
toning bath for prints on paper prepared with silver nitrate.
Chloroform (CHCl. Sp. gr. 1.525).-A colourless, very volatile
liquid of sweet smell, which boils at 61° C. (142° F.). Its vapour
must not be inhaled, as it produces unconsciousness. The chief use
of chloroform is as a solvent for india-rubber, amber, and other gums,
and also in the preparation of the bitumen solution required in print-
ing on zinc.
Chlorophyll.—The green colouring matter of plants, extracted by
digesting for a short time in warm alcohol, is used in the preparation
of orthochromatic plates, which, by that means, are made sensitive to
the red of the spectrum.
Chromate of Silver. The use of this salt has been suggested by
Mr. W. K. Burton for the purpose of preventing halation. The
colour of the chromate is deep ruby, and it may be formed by
MATERIALS USED IN PHOTOGRAPHY.
259
mixing a solution of chromate of potassium with silver nitrate. An
emulsion with gelatine was made in the usual way, and was used as
a substratum in the preparation of gelatino-bromide plates. This
experiment proved that the chromate of silver emulsion was itself
sensitive to light, a fact which Hunt pointed out many years prior
to Mr. Burton's investigations. Hunt also suggested that this salt of
silver "has the most pleasing result of bringing within the range of
probabilities the production of photographic pictures in their natural
colours."
2
Chromium Potassium Sulphate, or Chrome Alum (K₂SOCг₂(SO4)3
+ 24H₂O).-When this salt is mixed with gelatine, the latter becomes
insoluble; and this property, as it will still absorb water, makes it
useful in some of the photo-mechanical processes of photography. It
is also used in the preparation of gelatino-bromide plates; a small
quantity added to the emulsion hastens its hardening, and lessens its
tendency to wash loose.
6
7
Citric Acid (C¿Н¸О, + H₂O) is derived from the juice of the lemon
and some other fruits, and forms colourless crystals, soluble in water
and alcohol. It often occurs as one of the components of developing
solutions, in which it acts as a retarding agent. It is used also in
some formulæ for toning prints on albumenised paper, and in the pre-
paration of ready sensitised paper.
Collodion.-Pyroxylin, dissolved in ether and alcohol, is called
collodion, which, on evaporation on glass, leaves a transparent film;
and it is this quality which has made it so valuable to the photo-
grapher. It has been claimed for M. Le Gray that he first suggested
its use in photography, but a letter received by the writer in 1887,
from Mr. C. T. Hervé, who was a friend of Mr. F. Scott-Archer, con-
tains this sentence, "Gun-cotton had just begun to be known, and
Mr. Archer said, 'I think I can dissolve gun-cotton in some spirit. . . .'
I was away from London a month; on my return I was shown a true
negative on talc. Archer had solved the question." It appears therefore
that, if the idea had occurred to M. Le Gray, it was equally original
with Mr. Archer; and to him is certainly due the discovery of one of the
greatest improvements ever introduced in the working of photography.
Full directions for making collodion will be found in the various
editions of Hardwich's "Photographic Chemistry." Particulars as to
the manufacture of pyroxylin will be found under that heading.
In the first instance, what is called plain collodion, so named to
distinguish it from the iodised form which is ready for photographic
use, is made as follows:-
Pyroxylin.
Alcohol .820
Ether .725.
55 grains.
4 ounces.
5
>>
260
MANUAL OF PHOTOGRAPHY.
This is considered more suitable for use in winter; but, by adding
half an ounce each of alcohol and ether, a modification occurs, making
the collodion more useful for work in warm weather. This is recom-
mended by Abney; but, in the writer's experience, no change is neces-
sary. The directions given by Hardwich should be strictly followed
in making collodion, and attention should be paid to the quality of
the pyroxylin, as upon this depends the character of the collodion.
The iodising solution is composed of :-
Ammonium iodide
Cadmium iodide .
Ammonium bromide
Plain collodion
+
3 grains.
grain.
I grains.
I ounce.
The iodides may be employed in various proportions, necessitating
longer keeping before the solutions are fit for use; but the above
answers for most purposes, and can be used three or four days after it
has been mixed.
If the photographer wished to study economy, he might make his
own collodion, as it would certainly be cheaper to do so, provided he
had no failures.
Copper (Cu). The chief use of metallic copper in connection with
photography is in making blocks for printing with type, when it takes
the place of zinc. In the preparation of plates by the photogravure
process, copper is used when the bitumen method is employed; and,
in the Goupil process, copper is electrically deposited in forming the
printing plate.
Copper Sulphate (CuSO4 + 5H,O, also called Cupric Sulphate,
Blue-Stone, Blue Vitriol, and Blue Copperas).-A solution of this
salt, to which a small portion of sodium chloride has been added
which will change the colour to green, due to the formation of cupric
chloride, may be used to bleach untoned photographs (or bromide
prints) which have been outlined in indian ink for the purpose of
reproduction in line.
Dextrin ((C6H1005). Also known as British Gum).-Dextrin is
formed when starch is boiled with a 3 per cent. solution of sulphuric
acid, or on heating it to 200° C. (390° F.). It is usually employed in
making paper adhesive, such as gummed labels, strips for mounting
lantern slides, and similar purposes.
Eau de Javelle.-As a reducing agent for negatives which are too
dense and for removing the last traces of sodium thiosulphate, the
following solution, which forms eau de javelle, may be used:-
Chloride of lime.
Potassium carbonate
Water.
4
·
40
2 ounces.
وو
MATERIALS USED IN PHOTOGRAPHY.
261
:
The lime must be mixed with thirty ounces of the water, and the
potassium carbonate in the rest; when boiled and filtered the solution
is ready for use.
Ebonite.-Indiarubber combined with sulphur is formed into a
substance called ebonite. It is used chiefly in photography in the
form of dishes and trays. It is very light, and almost as brittle as
glass. (See Dishes and Trays).
5
2
Eikonogen (C10H,NH₂ONaHSO3 + 2H,O).-This acid was first
described by Professor Meldola in 1881, but its first use in photo-
graphy appears to have been proposed by Dr. Andresen of Berlin in
1889. It is the sodium salt of amido-ß-naphthol-ß-sulphonic acid.
It occurs in large yellow crystals not readily soluble in cold water.
Its use as a developer is now well established; but so short a time
has elapsed since Dr. Andresen first suggested its use, that it must
be premature to say that eikonogen is equal or superior to pyrogallol,
to which, in its chemical relationship, it is closely allied. It cannot
even be said that the best formula for its use has yet been discovered;
but there can be very little doubt that the new substance will establish
its claim to be useful in photographic formulæ.
The following is selected from a large number of published
formulæ :
1. Eikonogen
Sodium Sulphite (pure)
Distilled water at 140° F.
2. Sodium carbonate
Potassium carbonate
Distilled water
S parts
5
500
25
19
25
500
Equal parts of 1 and 2 are to be mixed for use.
Dr. Andresen claims for it :-
1. That while eikonogen reduces the bromide of silver so far as it
has been subject to the action of light, the bromide in dry gelatine.
plates which has not been exposed to the light remains unaffected
by it.
2. That concentrated solutions of eikonogen (1: 20 to 1: 50) pro-
duce, even with instantaneously exposed plates, minutely detailed
negatives.
The minuteness of detail produced by eikonogen is supposed to
be due to the fine grain of the silver precipitate.
4. The tone of the negatives given by eikonogen is well adapted
for printing, and in this respect it excels pyrogallol.
5. The solutions of eikonogen containing sodium sulphite are
durable even after the addition of carbonate of soda, and the same
solution can be used for several pictures in succession.
262
MANUAL OF PHOTOGRAPHY.
6. Eikonogen is not poisonous, which cannot be said of pyrogallol
or hydroquinone.
Emery. This useful mineral, which is one of the forms of alumina,
is chiefly employed by photographers for grinding the surface of glass
for camera focussing screens and the glass plates used in the collotype
process.
Encaustic Paste. The following preparation was used by M.
Salomon of Paris to increase the brilliance of the surface of albume-
nised paper prints. White wax is mixed with gum elemi in oil of
lavender, in proportion to form a kind of pomade or paste. With
this the surface of the print is rubbed until the required polish is
obtained. White wax and Venice turpentine dissolved in spirits of
turpentine may be used for the same purpose.
6
2
Eosin.—The eosin of commerce is the potassium salt (C20H K₂
Br₁05) of tetrabromfluoresceïn. It is one of the substances derived
from coal-tar, is used as a dye, and also in making colour-sensitive
dry plates. Mineral acids decompose the eosin with liberation of
tetrabromfluoresceïn, which has a quite different absorption spectrum
from eosin.
6
Erythrosin (C20H&K₂IO).-Gelatine dry plates may be made ortho-
chromatic by steeping in a bath of erythrosin. (See Orthochromatic
Photography).
5/2
Ether ((C₂H)2O. Sp. gr. 0.736. Also called Diethyl Ether, Ethylic
Oxide).—In the manufacture of collodion, ether is used mixed with
alcohol as a solvent for the pyroxylin. Ether is also used in purify-
ing bitumen. As the vapour of ether is highly inflammable, and its
boiling point so low as 35° C. (95° F.), the greatest care should be
observed when using it where a light is burning. The fumes are
heavy, and therefore a light below the ether is more dangerous than
one above it.
6 5
Ferric Ammonium Citrate (Fe,(NH4)2(CH,07)3. Called also
Ammonio-citrate of Iron).—It is used in the preparation of paper for
the ferro-prussiate or "blue" process.
Ferric Ammonium Oxalate (Fe₂(NH4)2(C2O4)4, or Ammonio-oxalate
of Iron). In the platinotype process this salt is used to develop the
image, when the iron is converted to the ferrous state.
Ferric Oxalate (Fe2(C2O4)3, or Oxalate of Peroxide of Iron).—
Chiefly used in the platinotype process.
Ferrous Oxalate (FeC₂O4+2H,O, Oxalate of Iron).-Used in
alkaline developing solutions by mixing, as required, solutions of
ferrous sulphate and potassium oxalate.
Ferrous Sulphate (FeSO4 + 7H₂O, also called Sulphate of Iron,
Protosulphate of Iron, Copperas, or Green Vitriol). In the develop-
MATERIALS USED IN PHOTOGRAPHY.
263
ing solutions for the wet collodion process this salt of iron is very
largely used.
2
Fluorescein (C20H1205 + H₂O, Resorcin-phthaleïn).-Some of the
derivatives of this substance are used in the preparation of ortho-
chromatic plates.
Formic Acid (H₂CO₂).—A colourless liquid resembling acetic acid.
The strong acid blisters the skin. At one time it was used (instead
of acetic acid) in developing solutions for the collodion process.
was also used as a preservative of solutions of pyrogallol.
It
Gallic Acid (CHO).-Formed by the fermentation of tannic
acid. It dissolves in 100 parts of cold water, and gives a dark-blue
colouration with ferric salts. Gallic acid reduces silver solutions
much more quickly than tannin does, and in the early processes of
photography it was used as a developing agent for paper negatives.
It was with this acid that the discovery of the latent image was made
by Talbot.
Gelatine. This is one of the most valuable substances used in
photography. In addition to the place it takes in the preparation of
dry plates, some of its important properties are taken advantage of
in mounting and enamelling prints on paper, and in stripping films
from glass.
When bones, hoofs, and other parts of animals are boiled, a jelly
is formed on cooling, and in this state it is known as size; when
dried, as glue, both of which have a brown colour; and when puri-
fied, as gelatine, which should be colourless, and without taste or
smell. Isinglass is a form of gelatine obtained from the air-bladder
of the sturgeon.
The properties of gelatine are that it will swell in cold water, but
will not dissolve until heated. The melting-point of a gelatine solution
is several degrees higher than its solidifying point, and both points
are raised by increase in strength of solution, although they vary
with the quality of gelatine employed. Acids and alkalies both
lower the point of solidification. When gelatine has been heated
and cooled many times, or kept in a fluid state for any length of
time, it loses its power of setting. The presence of an acid assists
this peculiarity. In making emulsions, the bulk of the gelatine is
added after one portion has been boiled, owing to the fact referred to.
When potassium bichromate and some other salts are mixed with
gelatine it is rendered insoluble after exposure to light. Chrome
alum and some other substances render it insoluble without ex-
posure to light. It is these peculiarities which make gelatine one
of the most valuable materials used in the mechanical processes of
photography.
Dry gelatine is one of the hardest substances, and this is taken
264
MANUAL OF PHOTOGRAPHY.
!
advantage of in the Woodbury process, in which the gelatine trans-
parency relief is subjected to a pressure of many tons without injury.
In the manufacture of dry plates the kind of gelatine to be used is
of the greatest importance; and this is also the case in the collotype
process, it may be hard or soft, and the kind recommended should
always be used, if possible.
As a test of the quality of gelatine, the common kinds are very
brittle, while the better sorts are tough and difficult to break.
Inferior samples of gelatine may be purified by soaking in water,
which must be repeatedly changed, during many hours. It must
then be dissolved in about twenty times its weight of water. If not
already acid, acetic acid may be used to acidify the solution; the
whole is then mixed with egg-albumen in the proportions of about
one egg to twenty ounces of solution, and well beaten to a froth.
After boiling and then allowing to cool, the coagulated albumen will
be found to have removed the impurities, which remain in the top
portion of the mass. The further purification is effected by squeezing
the gelatine through canvas into water and well washing; then, by
steeping it in spirits of wine, the water is removed and the process is
finished by drying.
Glass. The varieties of glass used by photographers are patent
plate, flatted crown, and polished sheet. The slight greenish tint of
the latter kind is not objectionable in any way except when used for
covering objects when the purity of the colour is to be preserved.
In this case colourless glass may be employed; but, as salts of lead
are used in its manufacture, a change occurs in the course of time by
a decomposition of its surface, producing what is called sweating.
Glass of this kind is quite unsuitable for taking negatives on.
most purposes, flatted crown or sheet glass are suitable.
For
Glucose or Grape Sugar.-A sugar found in the juice of the grape.
and other fruit, and also in honey. At one time it was used as a
preservative for dry plates, or rather to keep plates moist. It is also
employed in the process of silvering glass.
3
Glycerine (C,H,O,; sp. gr. 1.260).-The principal use of glyce-
rine in photography is for preventing the too rapid drying of any
substance it may be mixed with; also for rendering gelatine more
flexible when stripped as a film from glass or other plates. The
quality possessed by gelatine of being very hygroscopic was made use
of in the Glycerine Process. A collodion plate was prepared in the
ordinary way and then dipped in a bath formed of glycerine 2 oz.,
honey 1 oz., silver-bath solution 1 oz., water 7 oz.; these were
mixed together and a quarter of an ounce of kaolin was added, the
whole being well-shaken together and then exposed to daylight for
two or three days. The clear solution was filtered, used as a preser-
MATERIALS USED IN PHOTOGRAPHY.
265
vative, then returned to the bottle with the kaolin, and was again
ready for use after filtration. Any kind of developing solution could
be used, and the time of exposure was somewhat longer than for wet
collodion.
Gold Chloride (AuCl).—This salt of gold, used chiefly for toning
photographs, is sold in glass tubes containing 15 grains. When it is
used in large quantities it is cheaper to make it, and to keep it in
solution, as in the crystalline form the salt is very deliquescent. To
make it proceed as follows:-Take a half-sovereign, preferably a coin.
but little worn; bend or break it in two and place it in a bottle. Mix
drachm nitric acid, 2½ drachms hydrochloric acid, and 3 drachms of
water, and pour the mixture into the bottle; place it on a stove so that
the fumes will pass up the chimney. Shake the bottle occasionally,
and in three or four hours add more of the acids (the two acids form
aqua regia) until all the gold is dissolved. Now add a few ounces
of water, and then neutralise the solution by adding sodium carbo-
nate until effervescence stops. The precipitate will contain copper
carbonate and some silver chloride, the presence of which may be
disregarded. The solution of gold chloride will be alkaline, and if
left in that state the gold will precipitate; therefore, as much hydro-
chloric acid must be added as will redden blue litmus paper. As
the coin weighs 61 grains, there will be 56 grains of pure gold, which
is equal to 86 grains of the chloride. Add more water to bring the
quantity to about 11 ounces, each drachm of which will contain 1 grain
of gold chloride.
There are other methods of preparing the gold chloride, but the
above is sufficient for all practical purposes.
Ammonia should not be used to neutralise the acids, as fulminating
gold (which is dangerous to handle when dry) would be formed.
The hyposulphite of gold (Sel d'or) is now seldom used in any pho-
tographic process.
Ground Glass.-By using diffused light in studios for portraiture
much better effects can be obtained than by allowing the light to pass
through clear glass. When it was necessary to admit all the light
possible owing to the slowness of the processes in use, the case was
different, and the direction of the light could be controlled by blinds;
but now it is possible to use obscured glass, blinds being still neces-
sary to control the direction of the light. The roof glass may be
obscured with white paint stippled, but ground glass, although more
costly, is much to be preferred. For this purpose, glass coarsely
ground will answer as well as the best. Another very important use
for ground glass is for the focussing screen in cameras; for this pur-
pose the finest grain should be used. Patent plate-glass is flatter
than crown or sheet, so that when two pieces are rubbed together with
266
MANUAL OF PHOTOGRAPHY.
finely-powdered emery and water the surfaces are more quickly and
evenly ground; any other kind of glass will show transparent places
when the remainder of the surface is finished. Care should be taken
that no coarse particles are in the emery, or scratches will be produced
which will be difficult to remove. To obtain the emery in the best
state, the powder should be shaken in a bottle with water and allowed
to stand for a very short time, when, the coarse particles having sunk
to the bottom, the remainder can be poured off and allowed to settle
for use.
The emery can be used without washing when the surface
of the glass is to be coarsely ground.
Gum Arabic or Gum Acacia.-Owing to its bad keeping qualities
this gum cannot be recommended for mounting photographs. It
readily becomes acid. Salicylic acid may be used as a preservative,
but other mountants should have preference. This gum has a
limited use in the preparation of paper for the photo-lithographic
process.
Gum Dammar dissolved in turpentine may be used as a medium for
retouching gelatine plates. The gum is also used in making varnish.
Gutta-percha. The hardened juice of Isonandra gutta is largely
used for photographic purposes in the form of dishes, bottles for
hydrofluoric acid, and in other ways.
Hydrochloric Acid (HCl, also called Muriatic Acid and Spirits of
Salt). The pure substance is a colourless gas of suffocating odour,
and is prepared by the action of sulphuric acid on common salt. It
forms a clear solution with water, in which form it is used in the
platinotype process. The yellow colour of some solutions of this acid
is due to impurities, such as iron and chlorine. This impure form
must be avoided for photographic work.
Hydrofluoric Acid (HF = 20).—The use of this acid requires great
care, owing to its corrosive properties. It should be kept in a gutta-
percha bottle. In photography its chief use is in stripping gelatine.
films from glass plates and for reversing gelatine negatives. Take
one part of the acid and twenty parts of water, and in this place the
plates to be stripped; in a short time the gelatine film will leave the
glass readily. For reversing a gelatine negative, take a clean glass
larger than the negative, rub it over with French chalk, and then
coat it with collodion. The negative to be stripped may now be
placed in the acid solution, and, when loosened, the film should be
removed to a dish of water. When the acid has been washed away,
the collodionised plate may be placed under the film in the dish, and
removed with the film carefully adjusted as required. A sheet of india-
rubber may be placed over it and the water squeegeed out. When
dry, the negative may be stripped in the usual way, or left in a
reversed position on the glass.
MATERIALS USED IN PHOTOGRAPHY.
267
Hydrogen Dioxide (H,O,, also called Peroxide of Hydrogen).-The
name of oxygenated water has been given to this substance, as in its
composition there is no other difference than the presence of one atom
more of oxygen, and as it readily decomposes into oxygen and water.
It is sold as a solution in water, and is known as "20 vol" or "10
vol" solution, according to the amount of oxygen which it will evolve.
One of its uses is as a bleaching agent, and it may be used to remove
stains from paper. By passing prints which have been fixed with
sodium thiosulphate through a solution of hydrogen peroxide the
action is supposed to be the elimination of the sulphur salt.
Hydroquinone (CH(OH),; the synonyms are Quinol and Di-
hydroxybenzene).-This substance has been known to chemists for
many years, but it is only recently that its use as a reducing agent
in photography has become general. It is sometimes referred to
under different names, but quinol is a correct term for it, and pro-
bably will be generally adopted. The opinions of those who have
tried quinol as a developing agent are very various; some give the
preference to "pyro;" but there can be no doubt that the qualities
of quinol are good, and that in some cases it gives superior results.
The literature of the subject is already very voluminous. It is, per-
haps, too early to pronounce an opinion on the qualities of this recently
introduced substance.
The following is the method for the preparation of hydroquinone.
A fuller description may be found in the Berliner Berichte, ii.
1103.
Aniline, the basis in the manufacture of so many colours used in
dyeing, is dissolved in sulphuric acid and water with potassium
bichromate, the proportions being-
Aniline
Sulphuric acid
•
Potassium bichromate in powder
Water
•
I part.
8 parts.
231/
30
A brown liquid is the result, to which potassium sulphite is added,
and is then extracted with ether by distillation, and the residue is
dissolved in hot water to which sulphurous acid and mineral charcoal
are added, and the solution is then boiled and filtered. The quinol
crystallises out in hexagonal rhombohedral prisms, which are soluble
in water, alcohol, and ether. By sublimation quinol takes a different
form on crystallisation, showing that it is dimorphous. Its solution
reduces silver nitrate, which property makes it useful in photography.
Solutions of hydroquinone become brown in the air, and quinone is
formed, but they are more permanent in presence of sulphurous acid.
"Permanent hydroquinone" occurs in commerce in yellow needle-
268
MANUAL OF PHOTOGRAPHY.
like crystals. On account of the mode of manufacture it contains
traces of sulphurous acid, which renders the material less liable to
oxidation than the ordinary quinol.
The following formulæ for developing solutions for gelatino-bromide
plates are selected from a large number. The first are the results of ex-
periments by Mr. Green, and are said to give a fine quality of image,
a good colour, and to develop in the same time as "pyro" and
ammonia :-
a. Quinol
Citric acid
Sodium sulphite (recrystallised)
Water
b. Caustic potash (fused)
•
Sodium sulphite (recrystallised)
Water
•
c. Potassium bromide
Water
d. Caustic potash (fused)
Water
80 grains.
IO
80
""
""
20 ounces.
160 grains.
160
20 ounces.
24 grains.
I ounce.
160 grains.
20 ounces.
For normal exposures use equal parts of a and b, adding 5 minims
of c for every ounce of solution. For over-exposed plates use d instead
used
of b, with an extra quantity of c, and for under-exposed plates omit c,
and in extreme cases add 6 to 8 grains more of sodium sulphite to
every ounce of developer. If the plates show a tendency to frill,
they must be immersed for one minute in a 5 per cent. solution of
alum before fixing. Sodium thiosulphate, in the proportion of 4
ounces to 20 ounces of water, should be used for fixing.
In the next formula the solutions are used in the proportion of
4 ounces of a and 30 drops of 1.
a. Quinol
Water
b. Ammonia
Water
•
25 grains.
20 ounces.
I drachm,
9 drachms.
In the following formula potassium bromide is used:-
No. 1. Quinol
•
Sodium sulphite
Sodium carbonate
Water
•
No. 2 a. Quinol
•
Potassium meta-bisulphite
Potassium bromide
Water
•
b. Potassium hydrate
Water.
I part.
2 parts.
10
67
4 grains.
4
I grain.
I ounce.
10 grains.
I ounce.
MATERIALS USED IN PHOTOGRAPHY.
269
Use equal parts of 2 a and 2 b with No. 1, and with some plates the
bromide may be omitted. In all cases distilled water should be used.
If, as is alleged, negatives having the qualities of wet plates can be
obtained with quinol, there will be much advantage in its use for some
purposes, particularly in cases where clear glass in the shadows is
necessary, as, for instance, for negatives for any of the mechanical
processes, such as photo-lithography and zinc etching. By the ordinary
method with "pyro" such negatives are scarcely to be obtained, and
the wet process must be used. Amongst amateurs the collodion
process has gone so completely out of use that, for them, to make
comparisons is little better than useless; but those who know what a
really good collodion negative is should keep such in view as a guide
in working with dry plates.
As an advantage in favour of quinol it is claimed that many plates
may be developed in the same solution; but it should be borne in mind
that the first plate will most certainly be better than the last. It is
also recommended to commence the development with old solution,
and finish with new.
Quinol may be used as a developer for bromide paper. (See
Developing and Developers.)
Hydroxylamine (NH₂O).—Although this substance has been known
for some years as a reducing agent, it has not come into general use.
The crystals are tabular and colourless. For developing gelatino-
bromide plates the following formula is recommended by Messrs.
Egli and Spiller:-
1. Alcohol
•
Hydroxylamine
2. Water
Caustic soda
15 parts.
I part.
8 parts.
I part,
For use, five parts of each are added to sixty parts of water.
The following gives good results with all kinds of dry plates :-
1. Alcohol
Hydroxylamine
2. Water
Caustic soda
3. Potassium bromide
Water
•
4 ounces.
2 drachms.
4 ounces.
4 drachms.
50 grains.
3 ounces.
For use, one drachm each of 1 and 2 are mixed with half a drachm
of 3
to each ounce of water. It is claimed that, although more costly
than "pyro," more plates can be developed with hydroxylamine; but
the same remark must apply as in the use of hydroquinone, viz., that
the first plates developed will be better than the last.
"Hypo" Eliminators.-The cause of the instability of silver prints
270
MANUAL OF PHOTOGRAPHY.
has occupied the attention of many chemists, with the result that
remedies have been suggested which cannot be said to have been so
successful in practice as was desirable. That "hypo" left in the
paper after fixing is primarily the cause of fading is generally acknow-
ledged, and to eliminate the last trace of this valuable, but here objec-
tionable, substance has been the object aimed at. Eau de Javelle
(potassium hypochlorite), Labarraques' solution (sodium hypochlorite),
Holmes' ozone bleach, Frandreau's eliminator (zine hypochlorite),
and some others have been used. These substances are all un-
stable, and the oxygen which they yield combines with the "hypo,”
which becomes sodium sulphate. There is more or less danger to the
prints from the use of any of these substances, the products of the
reactions being as detrimental as the trace of "hypo" they were in-
tended to remove. Danger from these supposed "eliminators" is
likely to arise from the possibility of less careful washing and relying
on the "eliminator" to make up for the defective washing. One of
the safest remedies was proposed by the late Dr. Angus Smith more
than twenty years ago. The prints, after fixing and washing, are to
be placed in water to which has been added a small quantity of per-
oxide of hydrogen. The effect of this is to convert the "hypo” into
sulphate, which, if left in the photograph, will do no harm; but it
should be removed by washing in a few changes of water. The
prints should not be left many minutes in the water containing the
peroxide of hydrogen, as its action is very energetic, and would soon
attack the print itself. There is another objection to this eliminator
—it is itself unstable; so that, if effectual in removing the "hypo"
while freshly made, it could not be relied on after it had been kept
some time, The best "eliminator" is water. (See Washing.)
Hyposulphite of Soda (see Sodium Thiosulphate).
India-rubber or Caoutchouc.-This is a compound of hydrogen and
carbon. It is the dried juice of certain tropical trees, such as the Ficus
elastica; when pure it is white. If some of the white part of the
substance is dissolved in one part of methylated ether and two parts
of benzolene, it may be used as a mountant for photographs. It has
the advantage of not cockling the mount, but it has the disadvantage
that in course of time the india-rubber may decompose, so as to cause
the print to leave the mount. When combined with sulphur in
various proportions we have vulcanite and other forms of india-rubber,
which serve many useful purposes in photography, as also in other
branches of science and art. In a very dilute form india-rubber is
sometimes used as a substratum.
Iodine (I. At. wt. 126.53; sp. gr. 4.95).- This element is
derived from kelp, which is the ash from certain kinds of seaweed
in which it is found as the iodides of magnesium and sodium. Iodides
MATERIALS USED IN PHOTOGRAPHY.
271
are now largely obtained from the Chili nitrate and from Stassfurt.
It is a dark-coloured crystalline solid, but slightly soluble in water,
and more readily in alcohol and potassium iodide. With alcohol it
forms tincture of iodine. It forms salts (iodides) with the metals,
many of which find an application in photography. Stains of silver
nitrate may be easily removed from the skin by first touching the
parts with the tincture and then with potassium cyanide. Care must
be taken that the skin is whole when these remedies are applied.
The vapour of iodine was one of the earliest substances used in
photography. (See Daguerreotype Process.)
(C
Iron (Fe.; At. wt. 55.9; sp. gr. 7.8).—Although one of the
most widely distributed and valuable of the metals, iron in its
metallic state is very little used in photography. In what are called
ferrotypes" thin plates of the metal are used to hold the collodion
pictures, the iron being coated with varnish to protect it from the
silver solution, or, in other words, to prevent the iron causing the
solution of silver to decompose.
Various salts of the metal form some of the most energetic and
valuable reducing agents, as will be seen by reference to the formulæ
given for developing solutions. Amongst the processes in which salts of
iron are used may be named the Blue process (Ferro-prussiate), the
Platinotype, and some others, which are described under their several
headings.
Iron, Ammonio-Citrate of (see Ferric Ammonium Citrate).
Isinglass.—The best isinglass is made from the swimming bladder
of the sturgeon. It is a pure form of gelatine, and takes the place
of that substance in some of the photo-mechanical processes.
Jena Glass.—Lenses are now being made by Zeiss and others with
a new kind of glass, manufactured under the direction of Professor
Abbe in Jena, Austria. A lens 9 inch focus is said to cover a plate
20 by 16, and one of 14 inch focus will cover 30 inches for landscape
work. Until the introduction of this new glass opticians were limited
to the use of about a dozen different kinds; the new kind is made in
ninety varieties, all possessing different qualities.
Kaolin (China or Porcelain Clay). The principal use of this
substance, which is formed by the disintegration of the felspar of
granite, is in decolorising silver solutions. When albumenised paper
has been floated on the silver solution it becomes discoloured, if certain
salts have been used, and the effect of shaking up the solution with a
small quantity of kaolin is to cause it to become clear, the colouring
matter settling with the kaolin. Animal charcoal produces the same
effect.
Lavender, Oil of.-This oil is prepared by distillation from the
plant Lavandula vera. Under the name of oil of spike a common
272
MANUAL OF PHOTOGRAPHY.
1
kind is sold. Bitumen is soluble in oil of lavender, and was thus
used in the earliest photographic experiments. The oil is still used
as a solvent, but turpentine answers the same purpose.
Lead (Pb.). For most purposes, when acids are not present,
leaden vessels may be used in photographic processes. In the etching.
methods, where nitric acid is used, care should be taken that the waste
acids are not thrown into places where the waste pipes are of lead or
other metal. Lead acetate has been used as a "hypo" eliminator.
Lead Nitrate (Pb(NO3)2).-The use of this salt of lead is referred
to under the heading Intensifying.
Lithium Chloride (LiCl). This chloride forms a white deli-
quescent mass, readily soluble in water and alcohol. It is occasionally
used in emulsions. The bromide and iodide are but seldom employed.
Litmus. For the purpose of testing the alkalinity or acidity of
solutions, strips of paper which have been stained with litmus are
used, and for all practical purposes in photography this test is
sufficient. In the delicate operations conducted by the practical
chemist this test is not always reliable, as the litmus is not affected
by some acids; substances such as methyl-orange, turmeric, phenol-
phthalein, and some others, are then used. Litmus is prepared from
some kinds of lichen which grow on rocks near the sea. The colour-
ing matter is extracted by a peculiar process in which potash is used,
and for commercial purposes is made up into cakes with chalk.
When required for making test-paper the colour is softened with hot
water, and the unsized paper is soaked in the blue solution. This
forms the blue test-paper required for ascertaining the presence of
acids. The paper is also supplied reddened. For this purpose the
blue paper is steeped in water acidified with sulphuric or hydrochloric
acid. An alkaline solution turns this red paper to a blue colour.
Test-paper should be kept in a bottle to exclude the air. If the
paper should by exposure become red, the colour may be restored by
being held over the mouth of a bottle containing ammonia.
Liver of Sulphur (see Potassium Sulphile).
Magnesium (Mg). For the use of this metal for photographic
purposes see Magnesium Light.
The bromide (MgBr, + 3H,O) and iodide (MgI) of this metal may
be used in collodion, and the chloride (MgCl₂) is used in gelatino-
chloride emulsion.
Mastic or Gum Mastic.-This gum may be dissolved in alcohol,
chloroform, and other solvents. It is used in the preparation of
varnish.
Mercuric Chloride (HgCl; also called Bichloride of Mercury and
Corrosive Sublimate).—A highly poisonous white compound, soluble
in 16 parts of water. It dissolves in 2 parts of alcohol or 3 parts of
MATERIALS USED IN PHOTOGRAPHY.
273
ether. It is used for intensifying negatives. When the plate has
been thoroughly washed after fixing, a solution of mercuric chloride,
if left for a time on the plate (which must be in a dish covered with
the solution or on a levelling stand), whitens or bleaches the film;
the mercuric chloride has reacted with the silver in the film, and
another substance, calomel (Hg₂Cl₂) has been formed. The white
image may be changed in various ways. A solution of ammonia
turns it black. Sodium thiosulphate answers the same purpose, but
ammonia is generally used.
Mercury or Quicksilver (Hg).—In its liquid state there is now no
use for this metal in photography, but in the daguerreotype process
the vapour produced by the application of heat was used to develop
the latent image.
Meta-Gelatine.-A solution of gelatine which has been boiled and
allowed to cool several times loses its power of forming a jelly on
cooling, and in this state is called meta-gelatine. It has been used
in the collodion process as a preservative. The preparation of the
substance was thus described by Mr. Maxwell Lyte :-Dissolve 1
ounces of white gelatine in 10 ounces of boiling water, and then add
60 minims of strong sulphuric acid, diluted with 2 ounces of water.
Boil for five minutes and allow to cool. Boil again for five minutes.
and again cool. The operation must be repeated if it should still
gelatinise. When it remains fluid, the acid is neutralised with
powdered chalk, and the sulphate of lime which is formed is removed
by squeezing the fluid through a cloth.
Methylated Spirit. When 10 parts of wood-naphtha are added to
90 parts of rectified spirit, what is called methylated spirit is formed.
This was allowed to be sold duty free. For most purposes in photo-
graphy this inferior spirit answers as well as the best. In the collodion
process it may be used in the developing solutions, and when it is
required to dry gelatine plates quickly; if they are immersed in this
spirit for a few minutes, most of the water is absorbed, and the plates
are quickly dried in a current of air. It is also the solvent in the
preparation of varnishes.
Another and inferior kind of methylated spirit is sold under the
name of finish. This contains three ounces of shellac or sandarac
to each gallon of spirit. If when water is added to methylated
spirit the solution turns milky, it shows that it is the inferior
kind.
As some change has recently been made by the Excise Department
of the Inland Revenue in the quantity of gum to be added to the
spirit before it may be sold duty free, what has been said as to its
use for photographic purposes may require to be modified. If, instead
of the methyl spirit now used to degrade the alcohol, any kind of
S
274
MANUAL OF PHOTOGRAPHY.
mineral spirit is substituted, such degraded spirit would no longer be
suitable for photographic purposes.¹
1
Mounts. The difference in appearance between a mounted and an
unmounted photograph is so marked that some consideration should
be given to the kind of mount to which the print should be attached.
There can be very little doubt that plate paper (that is, the kind of
paper on which large engravings are usually printed, having printed
on it a tint to imitate india-paper about an inch larger in every
way than the photograph) has the best appearance, especially
when the mounting has been done under pressure, so as to leave a
plate-mark on the mount. The professional mounters of photographs
have a method for effecting this kind of mounting which leaves
nothing to be desired. If cardboard mounts are used, they should be
thick, at least six-sheet, otherwise, when the prints are large, the
cockling of the board has a bad appearance. It is entirely a matter
of taste whether photographs should have border lines of any kind
when mounted on cardboard. When the india-tinted mounts are
used, border lines are altogether unsuitable and unnecessary.
Nitric Acid (HNO,; also called Aqua fortis).—This is generally
obtained of sp. gr. 1.42, but acid of sp. gr. 1.2 is used for most photo-
graphic purposes. The pure acid is employed for dissolving silver to
form silver nitrate. The strong acid is mixed with sulphuric acid in
the preparation of pyroxylin. For acidifying the silver bath the
pure acid must be employed Nitric acid of the "commercial"
quality is used as a solvent for the zinc in etching the plates for
making blocks for printing purposes. A weak solution of the acid is
used as a clearing solution after collodion plates have been strength-
ened with lead nitrate. The acid is employed in various other ways in
photographic manipulation; amongst others, the commercial kind is
useful, when diluted, for cleaning glass plates. Care should be observed
in handling nitric acid, as it produces stains on the skin, while the
fumes given off by the acid, especially on dissolving the metals in it,
are of a highly poisonous nature.
Oxalic Acid (H2C2O4 + 2H2O).—A crystalline white solid, some-
what easily soluble in water and alcohol. The free acid may be used in
the platinotype printing process to acidify the sensitising and develop-
ing solutions. Many of its salts are of importance in photography, as
the potassium, sodium, and iron oxalates. It is highly poisonous.
1 The duty-free spirit is now sold mixed with mineral naphtha or oil. In order
to obtain the spirit methylated so that it is fit for photographic use, application
must be made to the Board of Inland Revenue, who will grant a special authority
on satisfactory evidence being given that the spirit is to be used for the purpose
stated. Application must be made to an officer of the Inland Revenue, and when
the order is granted, the spirit may be obtained from a distiller.
MATERIALS USED IN PHOTOGRAPHY.
275
Ox-Gall. The gall of the ox, when purified and evaporated, is the
substance used by artists to cause water-colours to flow readily. The
surface of albumenised paper is repellent to aqueous solutions; and as
water-colour is often used on such paper, it will be found that a small
quantity of ox-gall mixed with the colour will entirely remove the
greasiness of the surface.
Palladium (Pd). This metal was discovered by Wollaston in
platinum ores. The salt used in photography for toning is the
palladious chloride, PdCl. The following is said to give good colour
to prints on plain salted paper :—
Palladious chloride
Sodium sulphite
Water
•
I grain.
60 grains.
IO ounces.
•
The result is very similar to platinum toning, but, as the metal is
much more costly (about 6d. per grain) than platinum, it is not likely
to take the place of the latter metal or gold.
Paper.—At the time when photographers had to prepare their own
paper, the proper kind to select was a matter of great importance;
they had very little choice, and Whatman's writing-paper was gene-
rally used, but after a time paper was manufactured specially for
photographic purposes. Amongst the makers the names of Canson,
Marion, Hollingworth, and Harrison occur; later, the papers known as
Saxe and Rive came generally into the market, and are now almost
exclusively used. The qualities of paper of different make are almost
as varied as their makers, although the materials used are in all
cases the same—that is, cotton and linen. The difference arises.
chiefly in the kind of size used. As, however, the photographer in
these latter days takes advantage of the convenience of using paper
which he can purchase ready prepared, so far as the plain or
albumenised papers are concerned, his choice lies between the Saxe
and Rive, which may be had of different thicknesses, and generally of
the size about 22 × 18 inches. When the paper is required ready
sensitised, the purchaser has many varieties to select from, and no
advice can be given, as one operator will succeed with a certain kind
when another will fail.
When a sheet of paper is examined by reflected light, it will be
found that the two surfaces are not alike; one side is slightly smoother
than the other. The smooth side should be selected and marked.
Whatman's drawing-paper may be used when a photograph is to be
finished in water-colours. When selecting the proper surface, it
should be examined for minute specks of metal, which sometimes.
causes serious defects in the print.
Cardboard.-When two or more sheets of paper are pasted together,
276
MANUAL OF PHOTOGRAPHY.
we have a substance on which it is convenient to mount photographs,
and care should be taken to select the best. The surface should be
perfectly even, as it not unfrequently happens that the paper forming
the middle of the sheet of cardboard is of inferior quality to the
exterior sheets; and, should there be any irregularities, the effect of
the mounted print will certainly be deteriorated. Another important
matter in selecting the best is that prints mounted on inferior board
frequently fade owing to impurities in the paper. Generally it may
be said that cardboard of the best quality will be free from the
defects referred to.
Paraphenylene-diamine (CH(NH2)2).—This is another of the sub-
stances allied to hydroquinone, which can be used to develop gelatino-
bromide plates, but there appears to be no advantage gained by its
use.
Platinum (Pt).—This valuable and rare metal, owing to its not
being soluble in acids, excepting in aqua regia, and to its great in-
fusibility, is used for many purposes in the chemical laboratory.
The salts of the metal are used in the platinotype process.
There are two series of the platinum salts, the platinous and platinic
compounds. The most important of these is Platinic chloride (PtCl),
a brown deliquescent solid, soluble in water, alcohol, and ether. It
is sensitive to light, and forms double salts with the chlorides of the
alkali metals, e.g., PtCl4 + 2 KCl. Platinous Chloride (PtCl₂) plays,
together with its double salt PtCl + 2KCl, an important part in the
platinotype process. Ferrous oxalate reduces it to platinum black.
Platinum salts can also take the place of gold compounds as toning
agents.
2
Poisons. Many of the substances used in photography are of a
most poisonous nature; but, as such substances should always be
kept in bottles of a blue colour, carefully labelled, and placed out of
the way of children, very little need be said excepting by way of
caution. It is difficult to conceive that fluids in use in the workroom
of a photographer, whether amateur or professional, would ever be
swallowed by accident, while the poison in the solid state could
scarcely be used for suicidal purposes. The precautions to be observed
when using potassium bichromate have already been alluded to in
treating of the carbon process, but should any be taken into the
stomach, an emetic, powdered chalk or magnesia, should be adminis-
tered. The antidote for potassium cyanide is a solution of iron proto-
sulphate as used for developing. There are others, but they would
take too long to prepare, and in cases of poisoning with cyanide the
antidote must be given at once. Mercury bichloride, another of the
most active poisons in common use, permits of no delay in administer-
ing an antidote. The white of an egg or a mixture of flour and water
MATERIALS USED IN PHOTOGRAPHY.
277
should be given at once. For silver nitrate a solution of common salt
is the best remedy. If acids have been taken, any alkali will be the
most effectual; chalk, or a lump of plaster knocked from a wall,
would be a good substitute if powdered and mixed with water.
Potassium Bromide (KBr).-A white crystalline solid, soluble in
10 parts of water, and but slightly soluble in alcohol or ether. It is
used in the gelatine emulsion, and acts as a restrainer in the developing
solutions for gelatine plates.
Potassium Carbonate (K,CO).-This salt is known under various
names, such as potashes, pearl-ash, salt of tartar, and subcarbonate of
potash. It is used in the development of gelatine plates. The crude
potashes should not be used in developing solution on account of
impurities which have a deleterious influence.
Potassium Chlorate (KCIO,; Chlorate of Potash).—It crystallises
in shining plates, not readily soluble in water. It easily parts with
oxygen, and is therefore a powerful oxidising agent. It is used in
the platinotype process as an ingredient of the sensitising solution.
Potassium Chloroplatinite (K,PtC1).In the platinotype process
this is called red salt, and its use is, that with ferrous oxalate, it
reduces the platinum to the metallic state.
Potassium Cyanide (KCN; commonly called Cyanide, or Cyanide
of Potassium).A most powerful poison. It is generally used in the
collodion process in preference to sodium thiosulphate to dissolve the
iodide of silver from the film, or, in other words, to fix the image. The
solution should be used only of such strength as will be sufficient to
dissolve the iodide, as the cyanide salt possesses the power of acting
on metallic silver, and thus would weaken the image. Potassium
cyanide cannot be used to fix gelatine plates, as it has a solvent action
on the gelatine.
Potassium Dichromate (K,Cr2O7; also called Bichromate of
Potash and Red Chromate of Potash).-In the presence of gelatine
this salt is acted on by light and the gelatine is made insoluble. It
is this quality which makes it valuable in all processes such as photo-
lithography and zinc-etching. The salt in the latter case is used with
albumen, in which the action is similar to that with gelatine.
Potassium Ferricyanide (K,FeCy; also called Ferridcyanide of
Potash and Red Prussiate of Potash).—When chlorine gas is passed
into a solution of potassium ferrocyanide the oxidising action of the
chlorine produces the ferricyanide. This substance is employed in
many of the formulæ described. The ferricyanide gives a dark blue
compound with ferrous salts, ferrous ferricyanide, Fe,Fe,Cy12, or
Turnbull's blue. It is used in the preparation of blue prints, and,
with sodium thiosulphate, as a reducing agent for negatives that are
too dense.
278
MANUAL OF PHOTOGRAPHY.
Potassium Ferrocyanide (K,FeCy+ 3H2O; also called Yellow
Prussiate of Potash).-In the cyanotype process, in which the image.
on the paper is white on a blue ground, this salt is employed, to-
gether with a ferric salt. The two compounds produce a blue insoluble
body, ferric ferrocyanide or Prussian blue (Fe2)2(FeCy6)3.
Potassium Iodide (KI).-This salt is used in the preparation of
gelatine emulsion. It is made by dissolving iodine in solution of
caustic potash; it is then evaporated, and the solid mass is ignited
to redness. It is soluble in 70 parts of alcohol and in 120 parts of
alcohol and ether.
Potassium Oxalate (C₂K₂O4 + H2O; Oxalate of Potash).—A colour-
less crystalline solid, readily soluble in water. Its solution must not
have an alkaline reaction. The water employed should be free from
calcium, otherwise it forms a white precipitate of calcium oxalate.
The principal use for this salt is in the platinotype process, in
which it is used as the developer; in the production of ferrous oxalate
the salt is also used for developing gelatino-bromide plates.
Potassium Permanganate (KMnO4; Permanganate of Potash).-
This salt forms dark metallic-looking crystals. It is freely soluble in
water, with which it gives a deep violet solution. It may be used
to intensify plates in the wet collodion process. In the form known
as Condy's fluid it is a disinfectant. Its action depends on its being
a powerful oxidising agent, for which reason it can also be used for
purifying the silver bath by oxidising the organic matter which has
become dissolved in it.
Potassium Sulphide (K,S,; commonly called Liver of Sulphur).—
It consists of a mixture of sulphides of potassium made by heating
sulphur and potassium carbonate in closed vessels, and is used to pre-
cipitate silver from solution of sodium thiosulphate.
Pyrocatechin (CH(OH)2; Ortho-dihydroxybenzene, Catechol,
Oxyphenic Acid, Brenzcatechin). This substance is one of the
derivatives of coal-tar, and is isomeric with hydroquinone (the paradi-
hydroxybenzene), and can be used as a developing agent in photo-
graphy. It was first employed by Toth and Eder in 1880, who
claim for it a more energetic action than hydroquinone. The
formula is:
A. Pyrocatechin.
Sodium sulphite
Water
B. Potash
•
•
•
Water
I part.
4 parts.
40
4
40
Mix one part of A. to two parts of B.
The high price at present prevents the general use of this sub-
stance, but (as has been the case with its relatives eikonogen,
MATERIALS USED IN PHOTOGRAPHY.
279
hydroquinone, and pyrogallol) if there were advantages in its use, the
discovery of cheaper modes of production would quickly cause a
reduction in price.
Pyrogallol (CH,(OH),; Pyrogallic Acid, Pyro, Trihydroxybenzene).
-Pyrogallol is a trihydroxybenzene derived from gallic acid by de-
structive distillation, carbon dioxide being driven off as one of the
products of decomposition, the reaction being :-
C6H2(HO)3COOH=CH₂(HO)3 + CO₂
Gallic acid.
Pyrogallol.
Gallic acid was one of the earliest reducing agents used in photo-
graphy, but, although the substance derived from it (pyrogallic acid)
was known as early as 1831, it was not until 1851 that it was first
suggested by Liebig and Regnault as a developing agent, and it still.
maintains its position, although the allied substances hydroquinone,
eikonogen, and some others, have recently become established as
rivals.
In the manufacture of pyrogallol, gallic acid is subjected to a
temperature of about 410° F., when the latter is decomposed and the
pyrogallol is condensed in lamellar shining-white crystals. The sub-
stance is soluble in water, alcohol, and ether, and quickly decomposes
on exposure to the air or in aqueous solution; so that the addition of
sodium sulphite, citric acid, or some other substance is necessary to
arrest the decomposition.
When the collodion process was first introduced, pyrogallic acid was
almost exclusively used as a developing agent; but it was superseded
by iron protosulphate, and is now used in the wet collodion pro-
cess, chiefly in redeveloping (or strengthening) the negative image.
When, however, dry processes were introduced, pyrogallol became of
the utmost value, as it was found by Colonel Russell that in presence
of ammonia its action was that of a powerful developing agent for
tannin plates; and it has the same properties and advantages with
gelatino-bromide plates. The affinity of an alkaline solution of
pyrogallol for oxygen makes it necessary to restrain its action, and
for this purpose potassium bromide is used.
Pyrogallol or pyrogallic acid can lay no claim to the title of an
acid; it is more correctly a triatomic phenol. It is a neutral com-
pound, which neither reddens litmus nor forms any well-defined salts.
Pyroxylin or Gun-Cotton.-That used in photography is essen-
tially a tetra-nitrate and penta-nitrate of cellulose, C₁₂H16(ONO2)406
and C₁₂H15(ONO2)505, which dissolve in alcohol and ether, forming
collodion. These compounds are formed by warming cotton for some.
time with 20 parts nitre and 30 parts concentrated sulphuric acid.
The peculiar properties of pyroxylin depend on the character of the
280
MANUAL OF PHOTOGRAPHY.
fibre from which it is made, the proportions of the acids used in its
manufacture, and the temperature at which the cotton is immersed.
As the preparation of pyroxylin is a somewhat troublesome opera-
tion, very few amateurs will make it for themselves; but, for those
who wish to attempt its preparation, two of the formula with the
necessary directions are given here. Hardwich is the authority
usually quoted, and the following is condensed from his "Photographic
Chemistry."
The Nitre Process.-Only the best nitrate of potash should be
used. It must be reduced to a powder, dried on a hot metal plate in
an oven, and again pulverised. Take of-
Oil of vitriol (sulphuric acid)
Dried nitre (potassium nitrate)
Water.
Best cotton-wool
6 ounces.
3/1/2
I ounce.
60 grains.
The acid and water must be mixed in a cup or other porcelain vessel,
the sulphuric acid being poured into the water (on no account must
the water be poured into the acid, as serious explosions and burns
through the scattered acid may result), and the powdered potassium
nitrate stirred in with a glass rod. The cotton must be pulled into
balls about the size of a walnut, and when a thermometer placed in
the acid remains at 60° C. (140° F.), the cotton balls must be put in
singly and pressed against the sides of the cup with a glass rod.
If the temperature of the acid falls below 140° F., the cup must
be floated on boiling water to raise the heat. The cotton must remain
in the acid ten minutes, the excess of acid must be poured off, the
pyroxylin pressed against the cup with the glass rod, and the whole.
then quickly placed in cold water and moved about until it is itself
quite cold.
-
The Process with Mixed Acids. — In this process larger quantities of
cotton may be treated, as the temperature has less chance of altera-
tion. Take of
Nitric acid, sp. gr. 1.45
Sulphuric acid, sp. gr. 1.84
Water.
Cotton
6 ounces.
18
44
400 grains.
Into a deep narrow porcelain vessel pour first the water, then the
nitric acid, and the sulphuric acid last, and stir well with a glass rod.
The temperature at first will indicate from 165° to 170° F. (70° to
80° C.), which will in about twenty minutes fall to 140° F. (60° C.),
the proper temperature for immersing the cotton. This is very im-
portant, and the acids must be stirred with the thermometer to ensure
accuracy. The 400 grains of cotton must be separated into two
MATERIALS USED IN PHOTOGRAPHY.
281
equal weights-one-half set aside to be dealt with afterwards, the
other divided into about twenty portions, all to be pulled out loosely,
and each portion put separately into the acids when the temperature
has reached the proper point. This must be quickly done, and the
cotton moved about and pressed against the side of the vessel to
ensure the acids being properly taken up. The vessel must now be
covered up and left for ten minutes. The cotton is then taken out
quickly, if possible in one mass, and pressed against the side of a
shallow vessel; then pour away the acid into the deep vessel, at once
put the cotton and the vessel containing it into a large quantity of
water, and immediately take hold of it with the hand, rapidly moving
it about until it is cool and separates in the water.
The second half of the cotton may now be treated, the acids being
warmed in a hot-air bath to 144° F., and 6 drachms of sulphuric acid
added; allow to cool to 140° F., and put in the 200 grains of cotton,
treating it like the first half.
The pyroxylin must now be washed. Pour off all the water, and
then allow running water to pass through the wool for forty-eight
hours. When thoroughly washed, squeeze out all the water, pull the
fibre out well, and expose it in the air to dry on blotting-paper. In
the summer, sun heat may be used to complete the drying; at other
times a drying dish containing sulphuric acid must be used.
The pyroxylin when thoroughly dry should be kept in stoppered
bottles.
Pyroxylin may also be made from linen, wood, calico, paper, and
other substances.
Quinol (see Hydroquinone).
Ready Sensitised Paper.-Directions for preparing paper with
silver nitrate will be found under the heading Printing and Toning.
When paper is required only in small quantities, it may be purchased
ready for use; and although the results after printing may not be
equal to the freshly prepared paper, the saving of time and trouble is
considerable. Many formulæ have been published for preserving
paper in a sensitive state, (the tendency of freshly prepared paper is
to turn yellow after a few days, and in some cases hours); amongst
them is the following, recommended by Mr. Ashman :—
White gum-arabic, picked
Tartaric acid
Hydrochloric acid
Citric acid
Water
3 parts.
2
2
•
2
.
100
""
The paper is sensitised in the usual way, and when dry it must be
floated on the back on the above solution for four or five minutes,
dried, and then stored under pressure.
282
MANUAL OF PHOTOGRAPHY.
Another method for preserving paper is given by Mr. Burton as
under :-
"For ordinary printing, where the highest degree of sensitiveness
is desired, the proportion of silver must be increased, and the paper
should be fumed with ammonia before being used:-
Nitrate of silver
Citric acid
Water
75 grains.
75
3 ounces.
"Take one-fourth of this quantity (oz.), and having formed a full
sheet of ordinary albumenised paper into a dish by turning up the
edges say one-fourth of an inch all round-pour upon it the sensi-
tising fluid, and spread it with a Buckle's or Blanchard's brush."
If it is only required to keep for a short time paper which has been
freshly sensitised, it may be placed between paper which has been
saturated with sodium bicarbonate. When the soda paper is quite
dry the sensitised sheets are placed face to face between the preserving
paper.
It must be borne in mind that ready-sensitised paper will not keep
indefinitely, also that there is much difference in the keeping qualities
of the various kinds in the market.
The best results on albumenised paper can only be obtained when
the paper is freshly prepared, and not subjected to any "preserving "
process; but the great convenience of having paper always ready, and
the trouble of preparing it avoided, has made ready-sensitised paper
almost an absolute necessity, and it is now probably used by every
amateur and most professional photographers.
Rodinal. This fluid, recently introduced for developing gelatino-
bromide plates, is a concentrated solution of Para-amidophenol. For
negatives which have received a normal exposure, the rodinal should
be diluted with 30 parts of water; but with 40 parts of water the
development would be more under control. When a plate has been
over-exposed potassium bromide should be added, or a portion of the
developing solution which has already been used. If under-exposed,
the negative should be developed with a weak solution of rodinal.
From 100 to 200 parts of water may be added to the developing
solution if used for gelatino-bromide paper. It will be noticed that
this is a one-solution developer, and it is well spoken of by many of
those who have tried it. This new developing solution is patented by
Dr. M. Andresen. It is supplied ready for use.
Sandarac or Juniper Resin.-This gum or resin is soluble in
turpentine and alcohol, and is sometimes used in making varnish.
Shellac or Gum Lac.-This is a brown gum, which may be bleached
till nearly white. It is used in making varnish, and for some other
MATERIALS USED IN PHOTOGRAPHY.
283
purposes, such as the preservation of wood from the action of fluids.
It is readily soluble in alcohol.
Silver (Ag. At. wt. = 108; sp. gr. 10.5).—In its metallic state
silver is used in the form of wire for dippers for the wet collodion
silver bath; the small quantity of nitric acid in the solution has very
little effect on the wire; the wire is also used as the corner supports
in the carrier frames. It was formerly used in the daguerreotype
process in thin sheets attached to a thicker plate of copper, and upon
the silver surface the picture was formed. When dissolved in nitric
acid, silver nitrate is formed. Sulphuric acid also acts as a solvent,
forming sulphate of silver.
This metal is found combined with various substances as a chloride
in horn silver, the term by which it was known to the alchemists; it
also occurs in lead and copper ores, and it is found combined with
sulphur, antimony, and bromine. The purity of the colour of the
metal is preserved unless exposed in the air to sulphuretted hydrogen,
which causes the surface to tarnish.
The various salts of silver enter very largely into most of the
photographic processes.
Silver Bromide (AgBr = 188).—-The precipitate formed when an
alkaline bromide is added to silver nitrate, is known as silver bromide,
and when used in the preparation of gelatine plates gives the extreme
sensitiveness to light which such plates possess. The reactions which
light causes in the haloid salts of silver are still matters of specula-
tion amongst chemists, and although the subject has caused much
experimental research, it cannot be said that satisfactory results have
yet been arrived at. It was with the vapour of bromine that the
daguerreotype plate was made extremely sensitive to light when used
with the vapour of iodine, and it is the presence of the bromide
with the silver in the gelatine film which gives the value to the
latest improvement in photography known as the gelatino-bromide
process.
Silver Chloride (AgCl = 143.5).—The earliest record we have of
the chemical change produced by light was the observation that in
its native state horn silver, which is the chloride of the metal, changed
colour when exposed to light in the presence of organic matter of any
kind, changing from all shades of grey to blackness. This quality of
changing colour renders this salt of silver of the greatest value to
photographers, as upon it depends the various processes of printing in
which it is used.
Silver Iodide (AgI = 235).—It is distinguished from the bromide
and chloride by its yellow colour. In the wet collodion process the
iodide contained in the collodion becomes converted into silver iodide
when acted on by the silver nitrate in the silver solution or bath, and
284
MANUAL OF PHOTOGRAPHY.
in this state is highly sensitive to light. The image produced on the
film is invisible, but on the application of suitable reducing salts the
picture is revealed, and we have either a negative or positive image,
according as the manipulation is modified. Silver iodide is also used
=
in the preparation of emulsions.
Silver Nitrate (AgNO 170; called also Lunar Caustic).
As generally employed for photographic purposes, this salt is either in
flat crystals, or, when fused, in cakes and sticks, when it is called
lunar caustic. The recrystallised salt should be used by preference.
Fused nitrate was at one time recommended, but it is possible that
silver nitrite may be formed in fusing the salt, and this, if em-
ployed in the wet collodion process, causes fog, when the solution
cannot be used for some days, during which a change occurs, and
the addition of a small quantity of nitric acid puts the bath in
working order again.
Silver Oxide (Ag₂O = 232).—The oxide of silver has very little
use in photography. It is occasionally used to neutralise solutions of
silver nitrate, as it is dissolved by any free acid with the formation
of the neutral nitrate.
Silver Sulphide (Ag,S).-This is the compound formed when liver
of sulphur is added to old sodium thiosulphate fixing solution. It
is converted into metallic silver by fusion or by mixing with an
alkaline carbonate, the latter being the simpler process.
2 2
Sodium Acetate (NaHC₂O₂+ 3H2O).—A crystalline solid which
melts without decomposition. It is used with gold chloride in certain
formulæ for toning prints.
Sodium Carbonate (NaCO3 + 10H₂O. It is known under various
names, such as Washing Soda, Sal Soda, Carbonate of Soda).—This
salt may be obtained in various degrees of purity, but the common
washing-soda is sufficiently pure for making the toning bath alkaline.
Soda-ash, a calcined form of the carbonate, free from water of crystal-
lisation, is used in the reduction of silver residues.
Sodium Chloride (NaCl).—One of the most widely distributed
salts, known as common salt, rock-salt, and by various other
names. It is generally used, together with silver nitrate, to render
paper sensitive to light. Amongst its other uses are its addition
to silver solutions to recover the silver, and it may be employed in
a moist state for cleaning porcelain or glass, the salt being well rubbed
over the dish with the hand.
Silver chloride is slightly soluble in a solution of sodium chloride,
a difficultly soluble double salt (NaCl + AgCl) being formed. It
was this property which enabled the salt to be used for fixing silver
prints before the use of sodium thiosulphate was discovered.
Sodium Nitrate (NaNO; also called Saltpetre).—A compound
MATERIALS USED IN PHOTOGRAPHY.
285
little used in photography, but it is occasionally added to the silver
bath used in the collodion process.
Silver nitrate has been adulte-
rated by mixture with it.
Sodium Oxalate (Na2C2O4).-A crystalline solid, very readily
soluble in water, and used in one of the platinotype processes.
Sodium Silicate or Water Glass.-The chief use for this salt is
in the preparation of the substratum on glass used in the collotype
process. It generally occurs in commerce as a syrupy liquid.
Sodium Sulphite (Na₂SO, +7H,O).—Sometimes used as a pre-
servative of "pyro" and its congeners, as its great affinity for oxygen
retards the oxidation of those substances. This ready oxidisability
necessitates its being kept in well-closed bottles, otherwise it is soon
converted into sodium sulphate. It may also be used for fixing
prints; but sodium thiosulphate is cheaper and answers the purpose
better.
3
Sodium Thiosulphate (NaS,O,+5H₂O; commonly known as
"Hypo" or Hyposulphite of Soda).-In the preparation of this salt a
current of sulphur dioxide is passed into a mixed solution of sodium
sulphide and caustic soda, and when purified by crystallisation the
sodium thiosulphate is obtained in large colourless crystals, soluble in
their own weight of water. It can now also be prepared from the
residue of the soda manufacture. As no substitute for the substance
so long known under the name hyposulphite of soda has yet been
discovered, and as its history is not generally known by those who
use this valuable fixing agent, no apology is perhaps necessary for
introducing here matter which the writer published in 1866. It
may be stated that the early photographs on paper were partially
fixed by washing with a solution of potassium iodide or bromide.
Ammonia had also been tried, but common salt was found to be better
for the purpose.
The following is quoted from the Proceedings of the Manchester
Literary and Philosophical Society of April 12, 1866, Photographic
section, "Note on the First Use of Hyposulphite of Soda in Photo-
graphy":-
"During an investigation into the early history of photography, I
met with the statement that Daguerre used hyposulphite of soda in
his process for fixing the pictures, and also that in Mr. Talbot's patent
the use of that substance was included. I was under the impression
that Sir John Herschel had pointed out that hyposulphite of soda
would fix the photographic image, but was unable to ascertain where
or when the discovery was first published. In order to determine
this point, I wrote to Sir John Herschel, requesting him to inform me
whether the discovery was his, and the date when it was published.
To these questions I received the following reply :—
286
MANUAL OF PHOTOGRAPHY.
COLLINGWOOD, October 29, 1864.
'SIR,—I think I may very fairly claim the discovery of the hypo-
sulphites as fixing agents, as I believe I was the first to call the
attention of chemists to that class of salts and their peculiar habi-
tudes, especially in relation to the insoluble salts of silver.
In my paper "On the Hyposulphurous Acid and its Compounds,"
which bears date January 8, 1819, and which appeared in Brewster
& Jamieson's Edinburgh Philosophical Journal, 1819, occur these
words:-
"One of the most singular characters of the hyposulphites is the
property their solutions possess of dissolving muriate of silver and re-
taining it in considerable quantities in permanent solution" (p. 11).
""Hyposulphite of Potash.-It dissolves muriate of silver, even
when very dilute, with great readiness" (p. 19.)
C CC
Hyposulphite of Soda.-... Muriate of silver newly precipitated
dissolves in this salt when in a somewhat concentrated solution in
large quantity, and almost as readily as sugar in water” (p. 19).
C. CC
Hyposulphite of Strontia.-... Like the rest of the hyposul-
phites, it readily dissolves muriate of silver, and alcohol precipitates it
as a sweet syrup" (p. 21).
""Hyposulphite of Silver.-Muriate of silver newly precipitated is
soluble in all liquid hyposulphites, and, as before observed, in that of
soda with great ease and in large quantities. This solution is not
accomplished without mutual decomposition, as its intense sweetness
proves—a sweetness surpassing that of honey, and diffusing itself
over the whole mouth and fauces, without any disagreeable or metallic
flavour" (p. 27).
'In a second paper on the same subject, which appeared in the
same journal, vol. i. p. 396 et seq., it is shown (inter alia) that the
affinity of this acid for silver is such that oxide of silver readily
decomposes hyposulphite of soda, and likewise the soda in a caustic
state, "the only instance, I believe, yet known of the direct displace-
ment of a fixed alkali við humidâ by a metallic oxide ” (p. 397).
Hyposulphite of Ammonia and Silver.-Its sweetness is unmixed
with any other flavour, and so intense as to cause pain in the throat.
... One grain communicates a perceptible sweetness to 30,000 grs. of
water" (p. 399).
6.66
'In a third communication, dated November 1819-"The habi-
tudes of this acid with the oxide of mercury are not less singular
than its relation to that of silver."—"The red oxide is readily dis-
solved by . . . hyposulphite of soda, while the alkali is set at liberty
in a caustic state,” &c. &c.
'The very remarkable facts above described I have reason to
MATERIALS USED IN PHOTOGRAPHY.
287
believe attracted a good deal of attention at the time, and thence-
forward the ready solubility of silver salts, usually regarded as in-
soluble, by the hyposulphites was familiar to every chemist. It
would not, therefore, be surprising if Daguerre tried to fix his plates
(i.e., to wash off the iodide coating); but I have been informed, though
I cannot cite a printed authority for it, that at first he fixed with
ammonia, or with a strong solution of common salt.
'For my own part, the use of the hyposulphites was to myself the
readiest and most obvious means of procedure, and presented itself
at once. My earliest experiments were made in January 1839, and
in my notebook I find :-
"Exp. 1012.-1839, Jan. 29.-Experiments tried within the last
few days, since hearing of Daguerre's secret, and also that Fox Talbot
has got something of the same kind." [Here follow some trials
of the relative sensitiveness of the nitrate, carbonate, acetate, and
muriate of silver. I should observe that at that time I did not even
know what kind of pictures Daguerre had produced. This process
was not revealed till August 1839.]
6.66
Exp. 1013.-Daguerre's process-attempt to imitate. Requisites
—1st, very susceptible paper; 2nd, very perfect camera; 3rd, means
of arresting further action. Tried hyposulphite of soda to arrest the
action of light by washing away all the chloride of silver or other
silver salt; succeeds perfectly. Papers half acted on, half guarded
from the light by covering with pasteboard, were withdrawn from
sunshine, sponged over with hyposulphite, then washed in pure water,
dried, and again exposed. The darkened half remained dark, the
white half white, after any exposure, as if they had been painted
with sepia."
“Jan. 30, 1839.-Formed image of telescope with the aplanatic
lens . . . and placed in focus paper with carbonate of silver. An
image was formed in white on a sepia-coloured ground . . . which
bore washing with hyposulphite of soda, and was then no longer
alterable by light. Thus Daguerre's problem is so far solved," &c., &c.
Exp. 1014.-Jan. 30.-Tried transfer of print and copper-plate
engraved letters," &c., &c.
C. CC
'The publication of Daguerre's process (according to Dr. Monck-
hoven, for I cannot refer at present to the original document) took
place on the 19th August 1839. My early experiments, printed in
the notices of the Proceedings of the Royal Society of March 14,
1839, in which occurs this passage in the abstract of a paper read to
the Society :-
"Confining his attention in the present notice to the employment
of chloride of silver, the author inquires into the method by which
the blackened traces can be preserved, which may be effected, he
288
MANUAL OF PHOTOGRAPHY.
observes, by the application of any liquid capable of dissolving and
washing off the unchanged chloride, but leaving the reduced oxide of
silver untouched. These conditions are best fulfilled by the liquid
hyposulphites."
"Twenty-three specimens of photographs made by Sir J. Herschel
accompany his paper-one a sketch of his telescope at Slough, fixed
from its image in a lens.'
'This is the image above mentioned as having been taken on
January 30, 1839, and was, I believe, the first picture ever fixed from
an optical image ever taken in this country-at least I have heard
of none earlier.
At the time of making these experiments, as already mentioned,
I had no knowledge of M. Daguerre's process further than the mention.
of the existence of a process (a secret one) in a note from Admiral
(then Captain) Beaufort some time about January 23, 1839. Of
course I used paper, not silver-and it was not a suggestion, but a
regular and uniform practice to use the hyposulphite-I never used
anything else.-I am, Sir, your obedient servant,
'J. F. W. HERSCHEL.'
"In reference to the subject of fixing the photographic image, I
find the following passage in a paper read before the Royal Society on
January 31, 1839, by Mr. Talbot. After referring to the improve-
ments of Wedgwood and Davy in 1802, and the difficulties they found
in making the paper sufficiently sensible to receive the impression in
a camera obscura, and their inability to fix the pictures, the author
states that 'his experiments were begun without his being aware of
this prior attempt; and that in the course of them he discovered
methods of overcoming the two difficulties above related. With
respect to the latter he says that he has found it possible by a subse-
quent process so to fix the images or shadows formed by the solar
rays that they become insensible to light . . . and states that he has
exposed some of his pictures to the sunshine for the space of an hour
without injury.'"
From this it is quite clear that "hypo" was first used for fixing
the photographic image by Sir J. Herschel early in 1839.
Until 1869 it was not suspected that the "hypo" was not the
substance its name implied. In July of that year M. H. Saint-Claire
Deville communicated a paper, by M. P. Schützenberger, to the
Academy of Sciences, Paris, entitled "Note on a New Sulphur Acid,"
in which he describes experiments which led to the isolation of a new
acid. This new acid he calls "hyposulphurous acid." Without
going into particulars, it will be sufficient to say that this discovery
showed that the name borne by a substance already known was really
MATERIALS USED IN PHOTOGRAPHY.
289
";
correct for the newly discovered substance. The old "hyposulphite
therefore required to be re-named; and as its composition showed
that it was sulphuric acid, in which one atom of oxygen was replaced
by sulphur, it was called Thiosulphate of Soda.
In chemical notation the hyposulphite of soda is NaHSO2, and
thiosulphate of soda is Na2S2O3. It is the last-named substance which
is so extensively used in photography.
In works dealing with photographic matters the term sodium
thiosulphate is occasionally met with, but as chemists now recognise
two substances, and call the one used in photography by its true
name, there seems to be no reason why photographers should not
be exact. Pyrogallic acid is another instance in which a change of
name has occurred, and Pyrogallol is now recognised as the more
correct term; but "pyro" is still used as the diminutive, and if the
name must be shortened, instead of "hypo" it would be just as con-
venient to say "thio," while there may be some inconvenience in
using a term which is not correct. If a photographer were to speak
of sodium hyposulphite to a chemist, he would at once think it some-
thing different from what was in the mind of the photographer. It
seems to the writer that this necessary alteration in the nomenclature
of a term now so generally used incorrectly rests very much with the
editors of the journals devoted to photography. By them other
changes have been introduced, and the change in question presents
no greater difficulties. If the term hypo must still be used, it would
be better to write it "hypo," and thus show that a quoted, and not
the correct term is intended.
The use of the sodium thiosulphate as a fixing agent depends upon
its power of forming soluble double salts with the haloid compounds
of silver, the portion unaltered by exposure being thus removed, and
the plate or paper rendered indifferent to light.
In using sodium thiosulphate for fixing photographs on paper, it
should always be remembered that the solution must be strong.
If a weak solution be used, instead of the very soluble double salt
Ag,Na₁(SO), there is formed an insoluble one having the formula
Ag₂Na,(S₂O3)2, which would remain in the film.
Solutions of sodium thiosulphate should never be used a second
time, as, after a certain quantity of silver salt has been dissolved,
another insoluble double salt begins to be formed, and is precipitated
upon the film. It is, therefore, better to use two solutions, each
containing not less than 4 ounces of the salt to 20 ounces of water.
As it is very difficult to get rid of the last trace of this salt when
it has been used for fixing prints on paper, many substances have been
suggested as eliminators, amongst them sodium hypochlorite, hydrogen
perchloride, and iodine, but they are seldom employed.
T
290
MANUAL OF PHOTOGRAPHY.
6
Starch (CH10O5)n.-This substance is prepared from wheat, rice,
potatoes, Indian-corn, and other substances. Its principal use to the
photographer is for the purpose of mounting photographs, for which
it is preferable, as it can be used cold, and if the skin which forms in
cooling be taken off, it works smoothly. To prepare starch-paste,
sufficient of the powder may be put into a cup, and worked into a
paste with cold water; boiling water may then be poured in, and the
whole stirred until it is seen that sufficient water has been added.
Another way to prepare the starch, after it has been mixed with cold
water, is to boil it. The paste does not keep long, and should not
be used when it is the least acid. It is difficult to remove prints
from the card or paper when starch has been the mountant. The
print must be covered with boiling water, and allowed to remain
some hours, if it does not come away at once, and in some cases the
cardboard may be peeled away from the back.
The purest form of starch is known as arrowroot. Unlike ordinary
starch, it gives an almost clear solution when boiled with water; this
form is, therefore, used in the preparation of some kinds of photo-
graphic paper.
Starch is sometimes used in sizing paper.
Strontium Chloride (SrCl₂+ 6H₂O).-Soluble in water, less readily
soluble in alcohol. It can take the place of the other chlorides in
photographic processes; but the salts of strontium are very little used.
Sulphuric Acid or Hydrogen Sulphate (H₂SO4; commonly called
Oil of Vitriol).-It is employed with nitric acid in the manufacture of
pyroxylin. It has been used in some developing solutions, but,
although one of the most important of the acids, its use in photo-
graphy alone is very limited. It is used largely in the preparation of
other acids. The acid generally obtained is a heavy, oily, nearly
colourless liquid, of sp. gr. 1.83. If exposed in an open vessel in a
confined space, such as the glass case containing a balance, this acid,
by its strong affinity for water, has the effect of drying the air; this
affinity for water necessitates great care in mixing the two substances
(as when the acid has to be diluted). The acid must always be
poured into the cold water with constant stirring, and never the water
into the acid, as explosions would then almost certainly result.
Tannic Acid or Tannin (C14H1009 + H₂O).—It occurs largely in
gall-nuts. The pure acid is a colourless mass, and very soluble in
water. It is precipitated from its aqueous solutions by many salts, and
forms an insoluble compound with gelatine. In the manufacture of
ink tannic acid is used with ferric salts. Glucose and gallic acid are
formed when tannin is exposed to the air, or when treated with dilute
acids. When heated to 215° F. the result is pyrogallic acid.
at one time used as a preservative for collodion plates.
It was
MATERIALS USED IN PHOTOGRAPHY.
291
Test-Paper (see Litmus).
Turpentine (C10H16; also called Terebine and Terebenthine).-
From various trees of the pine and fir tribe a fluid exudes from which
turpentine is prepared. From Pinus sylvestris, P. nigra, and P. abies
common turpentine is obtained, and from the larch the kind called
Venice turpentine. The oil of turpentine is made by distilling the
crude turpentine with water; the residue is resin. Turpentine is
chiefly used in photography as a solvent for resins used in the zinc-
etching process.
=
Uranium (U. At. wt. 239).—This metal is found in the
mineral pitchblende, and has recently been discovered in Cornwall.
Uranium Nitrate (UO2(NO3)2 or Uranyl Nitrate).—It is used
as described under Uranium Printing Process.
Varnish. All photographs on glass are liable to injury in various
ways if not protected by some kind of varnish. With care, albumen
and gelatine films may be used without varnish; but as paper pre-
pared with silver nitrate is to some extent hygroscopic, there is danger
in stains being caused, and consequent injury to the picture if the
negative is not protected.
Many substances are used in the manufacture of varnish, but to
the amateur, as well as the professional photographer, it is of little
consequence of what the varnish is composed, provided it will not
crack, and is sufficiently hard to protect the film; and as the manu-
facture is a somewhat "sticky" operation, and the cost of the ready-
made article is not excessive, it is advisable to purchase as required
rather than make it.
As it is not possible always to obtain a matt varnish from the
dealer, it may be made, as recommended by Mr. J. Wingrave, as
under :-
Gum sandarac (picked)
White lac
•
Alcohol (methylated)
ounce.
I
20 ounces.
Dissolve and filter. To four ounces of the above add two drachms of
tartaric acid, shake well, and set aside to clear, and then decant into
a clear dry bottle for use.
The negative to be varnished should be warmed, but not made too
hot, and, after the varnish has been drained off, it should be held
before a bright fire until the plate is hotter than the hand can bear,
when it may be set aside till quite cold before being used.
A varnish to be used cold may be made from—
Powdered amber
Chloroform
I ounce.
16 ounces.
292
MANUAL OF PHOTOGRAPHY.
Or, in place of the chloroform, the same quantity of benzole may be
used.
As a protection to the film of a wet collodion plate, when it may
be required only for a temporary purpose, it is often sufficient to cover
it with a solution of gum arabic, which must be applied while the
plate is wet. The solution of gum may also be used before varnishing
in the ordinary way when the collodion has a tendency to split from
the plate.
Varnish, Black.-To one ounce of asphaltum and 20 grains of
india-rubber add 20 ounces of benzole. For varnishing brass-work, to
produce a dead black, lamp-black should be added to thin shellac
varnish, and tested until, when dry, no gloss is shown. The varnish
may be applied with a camel's-hair brush. A good black for wood-
work may be made with turpentine 16 ounces, lamp-black 8 ounces,
and gold size 2 ounces. The lamp black is formed into a paste with
turpentine, and then the rest of the turpentine and gold size is added.
Water (H2O). For many purposes in photography the absolute
purity of water is of very little consequence; but when chemical
substances are to be used in certain cases, and distilled water
is specified in the formula, it is necessary that the water should
nearly approach the purity obtained by distillation; not condensed
water from steam-engines, but distilled for chemical use. The
question of the purity of water does not affect the photographer now
as it did when the process in general use was wet collodion, and the
proper mixture of the silver nitrate bath was of the utmost importance.
A few years since the writer was engaged in an experiment of much
scientific interest many miles from home, and he took with him silver
in solution which he knew was in good working order; but, as a
reserve, he also took a supply of the purest fused silver nitrate. He
required to use this, but no distilled water was to be had. A supply
of rain-water was obtained, and on sunning the solution, a dense
black deposit was soon formed. After filtration, the bath was found
to be in good order, and was successfully used. The solution was
left in the hands of a local photographer, who informed the writer
some months afterwards that he had used the bath in various parts of
Sicily, and he had “ never had anything like it before." Filtered
rain-water, then, may be used as a substitute when distilled cannot be
had, and for most purposes filtration is sufficient. It should be
stated, however, that if the water is collected from house-roofs, time
should be allowed for impurities to be washed away.
Melted snow
is said to be purer than rain-water, and may be safely used. River-
water is to be preferred to that taken from wells, if it is not con-
taminated with sewage matter. It would be a simple matter here to
give directions for testing water for lime, iron, carbonates, or chlorides,
MATERIALS USED IN PHOTOGRAPHY.
293
but for the small quantity of water the amateur may require when
away from home he would be very unlikely to test it himself, and he
may use rain-water as suggested above.
Manchester and district has a supply of water which contains very
little impurity, as the following analysis shows:-
Total solid matter in solution
4.7 grains per gallon.
Free ammonia
Albuminoid ammonia
.0024
""
.0033
19
absent
Nitrates and nitrites
Oxygen contained in permanganate of
potash to oxidise organic matter, &c.,
in solution:—
Acting for two minutes at 80° F..
Acting for four hours at 80° F.
Combined chlorine
Phosphates
Total hardness
Permanent hardness
Temporary hardness
.ΟΙΙ
""
.086
:
.061
""
absent
1.3
??
1.2
O. I
When heated to 100° F. in a bottle, no smell was produced, and
the appearance of the water when a column two feet in depth was exa-
mined was slightly turbid and was faintly yellow. For this analysis
the writer is indebted to Mr. W. Thomson, F.R.S.E., F.C.S., &c., of
Manchester.
The Manchester water, then, may be used for most purposes in
photography without distillation, and has been so used by the writer
for many years in preference to any distilled water which he could
purchase. Glasgow also has a supply of water of excellent quality.
Wax.-The use of wax in photography is very limited. It is
useful for making paper semi-transparent, and dissolved in turpentine
or benzole is made into encaustic paste.
Zinc (Zn. At. wt. 64.9).—The salts of this metal have very little
use in photography, but the metal is largely used in the processes for
obtaining printing blocks in half tone and line. The metal may also
be used for reducing metallic silver from the chloride.
PART V.
!
CHAPTER I.
APPLICATIONS OF PHOTOGRAPHY.
Architectural Photography.-No special process is necessary in
making photographs of architectural subjects; but there are certain
precautions to be taken which may be referred to here. The camera
must be kept quite horizontal, if practicable; this can be done approxi-
mately by the eye, but a small weight attached to a string and used
as a plumb-line, or a spirit-level, may be used to ensure perfect level-
ling. A lens of the rectilinear type should be employed. Tilting the
camera either up or down should be avoided. In photographing tall
buildings, the sliding front to raise or lower the lens and the swing
back, should be used to correct the distortion which would appear by
tilting the camera, which process is only necessary when the rising
front will not otherwise permit all the subject to be brought in. In
photographing interiors it is often difficult to keep the tripod legs
from slipping on smooth floors. This can be prevented by fixing corks
on the pointed iron tips of the legs.
Astronomical Photography.-Although attempts were made to pro-
duce photographs of celestial objects by the daguerreotype method,
very little success was attained, and it was not until De la Rue,
Rutherfurd, the writer, and some others produced pictures of the moon
that the value of photography in astronomical matters was fully appre-
ciated. Some important scientific facts connected with astronomy have
been established by the aid of photography. In all total eclipses of
the sun, certain phenomena appeared which were difficult to explain.
An aureola of light, the corona, was always visible, and certain coloured
objects close to the edge of the moon, known as "red prominences,"
were the cause of much speculation until the eclipse of 1860, when
an expedition was sent to Spain, where Mr. De la Rue and Father
Secchi made photographs, from which it appeared that, as the moon
passed over the sun, the red prominences were gradually covered and
294
APPLICATIONS OF PHOTOGRAPHY.
295
uncovered; and as the photographs taken at different and distant
stations showed the same effects, it was, of course, concluded that the
phenomenon was an appendage of the sun. To settle the matter
experiments were made in India in 1868 by Colonel Tennant, which
fully confirmed the results obtained by De la Rue and Secchi in Spain.
Total eclipses of the sun, visible at places within convenient dis-
tance of England, do not often occur. The cause of the corona being
still unknown, it was decided to send expeditions to Spain and Sicily
in December 1870, one object of which was to obtain photographs
of this phenomenon. It had been contended that the beautiful corona
of light, always seen during total eclipses, was an effect produced in
our atmosphere; and it was also maintained that the appendage really
belonged to the sun. This point was settled in a very satisfactory
way by a comparison of two photographs, one taken at Cadiz, in
Spain, by Mr. Willard, and the other taken at Syracuse, in Sicily, by
the writer. Mr. Willard's photograph was taken about two hours
before the one at Syracuse, and yet the two photographs showed
features in this aureola of light which were common to both. This
could not have been the case unless the corona was actually connected
with the sun. Rifts or V-shaped markings were shown at the same
places in the pictures, and these peculiarities which appeared at sta-
tions hundreds of miles apart must have been persistent during the
whole time of the eclipse, or they could not have been visible in both
photographs. This seemed to be sufficient proof that our atmosphere
was not the cause of the phenomenon.
The collodion process was used in these experiments; but as soon as
gelatino-bromide plates became available, the use of photography was
extended to the spectroscope, and in subsequent total eclipses pictures
of the spectrum of the corona were obtained, thus adding another
proof of its solar origin. When it was found that comets, the nebulæ,
and stars could be photographed, there seemed to be no limit to the
possibilities which might be effected by photographic aid; and a great
work has recently been commenced, that of photographing the entire
heavens, including stars, to the fourteenth magnitude, which will
require, it is said, 10,000 negatives, and will include 20,000,000
stars, an achievement the importance of which cannot be exaggerated.
Objects which the most powerful optical aid had failed to reveal have
been photographed. The explanation of this, no doubt, is that the
very long exposure required to impress the light of stars of very small.
magnitude and faint nebulæ had enabled the very delicate nebulous
light to show itself on the sensitive plate.
It may, perhaps, be permitted to the writer to point out that in
taking photographs of celestial phenomena prior to 1870, the ordinary
telescope had been employed, and it was used in Spain in that year;
296
MANUAL OF PHOTOGRAPHY.
but it occurred to him that in photographing the corona a picture was
wanted, and that the size given by the greater focal length of a
telescope was of very little consequence compared with the importance
of showing the extent and detail of the corona, which could only be
obtained by having a suitable lens and larger plates than could be
advantageously used in a telescope. This idea was proved to be cor-
rect, as although the only instrument available was one which gave
an image only about three-tenths of an inch in diameter, the corona
was displayed extending several diameters of the sun, and in a way
never before seen on a photographic plate.
In the second edition of his work on the "Sun," the late Mr. R.
A. Proctor gives a full description of the results of this experiment,
and he says that the explanation of the success is to be found in the
fact that a new method was adopted in photographing the eclipsed
sun.
Mr. Willard's photograph was taken with a telescope in the old
way; and, as it showed detail of the same character as in the
photograph taken with a different instrument at Syracuse, it estab-
lished the fact that the corona was a solar appendage. It also
showed that a telescope was not a proper instrument to use for the
purpose; and this was proved in the following year, when some very
beautiful photographs were made in India for the Earl of Crawford
(then Lord Lindsay) by Mr. Davis, and by other observers in different
places. The instruments were of the same kind as the one used in
Sicily, but were specially mounted, with the result that the pictures
were superior to anything hitherto done; and in all subsequent eclipses
suitable apparatus has been employed, showing that the method
adopted by the writer for the first time was the proper one.
It may
also be pointed out that in all the important work in astronomical
photography since 1870, the apparatus employed has been either
silvered mirrors or lenses constructed as for ordinary photographic
work, thus carrying out the idea that pictures of the objects photo-
graphed are required, as also larger plates than can be used with an
ordinary telescope.
The cameras and lenses in ordinary use by photographers cannot
with advantage be adapted for photographing such objects as the sun
or moon. The size of the image of the moon (or sun), given by a
lens of ten inches focus, will be only one-tenth of an inch, so that a
lens of fifty inches focus would be necessary to make the photograph
half an inch in diameter. Therefore, something more handy must be
found. The astronomical telescope, when mounted equatorially and
with clockwork, can be readily adapted. A photographic camera,
with suitable lens, may be attached to the telescope so as to be driven
with it to counteract the apparent motion of the stars or moon, really
APPLICATIONS OF PHOTOGRAPHY.
297
that of the earth. The moon's motion in her orbit may be disregarded
when quick plates are used; indeed, the moon may be photographed
when full while the telescope is at rest, the exposure necessary being
much less than one second.
Although not so suitable as a lens corrected for the chemical rays,
or as a reflecting telescope, the ordinary achromatic telescope may be

le
h
f
C
b
e
a
α.
FIG. 105.
C
k
१


h
b
e
С
FIG. 106.
FIG. 107.
α, draw-tube of telescope; b, dark frame; c, slide; d, brass tube sliding into
place of eye-piece; e, outer metal frame screwed to d; é, inner metal plate ;
ƒ, diaphragm ; h, clips to hold plate e; i, spring to hold frame in first position ;
k, groove in the plate e, in which the spring-pin j slides.
used for photographing the moon. The accompanying Figs., 105,
106, and 107, show the method of carrying the sensitive plate, which
will be found convenient when the picture is to be taken at the
principal focus.
In this case the telescope itself forms the camera, and the plate-
holder is very little more than the dark slide of a camera.
If any
298
MANUAL OF PHOTOGRAPHY.
kind of enlarging lens be used with the astronomical telescope, a
camera must be attached, as the image may be larger than can be
taken on the small plates used in the apparatus described.
The method for ascertaining the actinic focus is as follows:-With
the rack motion adjust the focus for distinct vision, and then mark
the tube d, and also the sliding part of the telescope, so that any
change of their position may be readily seen. Although it is very
unlikely to be of the slightest use, unless taken with a reflecting
telescope, a picture may now be made; it will at least give some idea
of the proper exposure.
If the chemical and visual foci are not
coincident, the image will have a blurred appearance. Before exposing
the next plate turn the adjusting screw so as to draw out the tube
about one-sixteenth of an inch, and so proceed until, by the greater
distinctness of the image, it is seen that the chemical focus is found.
At every change of position a slight mark should be made on the tube,
and when the true focus is satisfactorily determined, the marks should
be made distinctly visible, and in all future experiments with the
same instrument the focus will be always at or very near the same
place. Should it be found that the indistinctness increases, it will,
of course, be necessary to try in the other direction, that is, to shorten
the focus.
The appearances arising from atmospheric disturbances are very
much the same as when the object is out of focus; experience alone
will enable the operator to determine from which cause the defect
proceeds.
Some of the best photographs of the moon ever taken were made
by the collodion process, an example of which is seen in the plate on
the opposite page, which is from a negative by Mr. L. M. Rutherfurd
of New York; but the great convenience of dry plates, and the extra
rapidity, give the preference to gelatine plates; indeed, some of the
work now undertaken could only be accomplished on such plates.
The MM. Henry, of the Paris Observatory, have exposed plates
during three hours while making negatives of the stars, and Mr.
Common, of Ealing, in producing the exquisite pictures of the great
nebula in “Orion," gave very long exposures. Mr. Roberts also did
the same while making his pictures of nebulæ and stars.
The fascinating occupation of photographing celestial objects may
be undertaken by all who possess the necessary apparatus; and no
more than ordinary care and patience are required to ensure success.
A very full account of celestial photography by the writer will be
found in the Proceedings of the Manchester Literary and Philosophical
Society, 1865, British Journal of Photography, December 22, 1865,
and in Chambers' "Astronomy," second and third editions.
Cameo. This term was applied to photographs which, after they

Woodbury-Gravure.
THE MOON-FIRST QUARTER.
L. M. RUTHERFURD, Photo.
Printed by THE WOODBURY COMPANY (EYRE AND SPOTTISWOODE), 6, Great New Street, London, E. C.
UNIV
OF
MICH

APPLICATIONS OF PHOTOGRAPHY.
299
were mounted, were pressed so as to raise the surface to a convex
form, giving the portrait somewhat the shape of the ordinary cameo.
Carte de Visite.-When first introduced this name was given to a
very small kind of portrait which was intended to be used on the
cards called visiting cards, or cartes de visite. The original purpose
was soon abandoned, but the convenience of the small-sized portrait
was at once appreciated, and for many years was most popular, and is
still largely used. The title was a misnomer.
Album or card por-
trait better described the picture. Portraits of a larger size, with the
title Cabinet, have to a large extent taken the place in public favour
of the smaller photograph.
Clouds. It very rarely happens at the time when a landscape is
photographed that the clouds are the most suitable for the subject, or
such as we should like to see in our picture, though at all times it
must be borne in mind that the landscape is affected by the sky. The
effect in the foreground and distance will be quite different under
a blue sky, or when cumulus clouds are present; and, as we cannot
command the kind of effect we wish to produce in the picture, great
care must be taken if clouds are introduced which have perhaps been
taken under totally different conditions. It was at one time rare to see
a landscape photograph with clouds; the purest white paper appeared
to be the aim of the photographer; and, even at the present day,
sufficient attention is not given to this very important feature in a
picture. Assuming that the sky at the time a picture is taken is just
what is desired, it will of course be desirable to preserve the effect
on the plate exposed for the landscape, and in some cases, with care
in the development, this may be done. But in the majority of
cases the exposure necessary for the landscape will be too great for
the sky, and this may necessitate double printing to obtain the cloud
effect. The landscape photographer should always be on the qui
vive to obtain good cloud negatives; the negatives need not be taken
on large plates. If on plates 6 × 42, or less, they can be enlarged;
and one negative may be utilised to make two effects by reversing.
When the sky portion of a landscape negative is not sufficiently dense
to leave the paper white when the landscape is fully printed, it must
be either shielded or stopped out. If carefully done, shielding is pre-
ferable to stopping out. The sky will probably be sufficiently dense
to permit shielding, which is effected by placing a sheet of thick
paper or cardboard shaped to follow the outline of the picture roughly.
The shield should not be placed too close to the negative. If the
printing-frame has thick glass, probably the thickness of the glass will
be sufficient to prevent a hard line when the shield protects the sky,
the object being to shade off the unshielded part into the white paper.
Remove the print from the frame, and place it on a sheet of glass or
3
300
MANUAL OF PHOTOGRAPHY.
on a board which is quite flat; select a cloud-negative which is suitable
for the picture (taking care that the light and shade in the clouds
correspond with the effect in the landscape); place the negative care-
fully on the print, and then protect the photograph from the light
with a piece of cardboard, with the part nearest the sky turned up,

thus-
FIG. 108.
This will permit the clouds to print
and shade off the part near the landscape, so as to blend with the part
already printed. If carefully done, the effect will be almost as good
as if the clouds had been taken with the picture. The clouds will
print very quickly, and great care should be taken not to make them
too dark-the merest indication of clouds is often sufficient.
Special care must be taken that the clouds do not spoil a church
tower or spire, or tall trees forming prominent features in the picture.
This may be readily avoided by so placing the cloud-negative that a
dense part covers the projecting object.
When a sky is stopped out, the result is often a hard line which no
amount of care in printing-in the sky will remove.
Very good indications of clouds may sometimes be made by paint-
ing on the back of the negative; but this must be skilfully done, or
the effect will be anything but natural. The same may be said if
cotton-wool be used. In all cases preference should be given to
natural clouds.
Cloud effects to represent moonlight are easily produced by taking
the negative when the sun is behind the clouds, and then printing
darkly. If the moon is to be shown in the picture, it must be of the
proper size. Suppose a lens of 10-inches focus be used, the size of the
sun or moon will be one-tenth of an inch. It is always better to use
a negative which has been taken direct when the moon is to be shown
in a picture. To ensure the correct representation, the lens used for
the landscape should be employed in making the negative of the
moon.
The vignette form of picture is very effective in landscape. (See
Vignetting.)
Composite Portraits.-By printing several portraits over each
other, a composite effect is obtained; the result is supposed to give
the type of the whole.
Composition. The value of a photograph depends very much on
what is termed composition. It is not sufficient in taking a picture
to place the camera and allow chance to arrange how the lines
will compose to form the effect. Two persons may make totally
different effects from the same subject, taken at the same time, and
APPLICATIONS OF PHOTOGRAPHY.
301
the difference will be caused merely by the different positions of the
camera; a tree, a rock, or a figure, may be so arranged in composing
the picture as to be effective in one case and obtrusive in the other.
The possession of a camera does not make an artist of its owner; and
unless some study be given to what is required in making artistic.
pictures, photographs, good from an artistic point of view, will only
be the result of accident. Treatises on the qualities necessary to form
pictures have been written and should be studied. If the student
will carry out hints he may derive from what he reads, defects too
often met with in photographs will be avoided. The introduction of
figures in a landscape is in many cases desirable, but if they are badly
placed an otherwise good picture may be spoilt.
Distance.-Much of the beauty of a landscape depends on the
proper rendering of the distance. This becomes difficult owing to
the effect of the atmosphere, the pale blue and grey of the distance
having almost the same actinic power on the plate as the sky. When
the objects in the foreground are dark, the difficulty is increased, and
the greatest care must be taken that the distance does not become
lost while the foreground is developed.
Interiors. The photographer is sometimes required to photograph
places where very little light penetrates. In the days before gelatine
plates were available, the difficulties were almost insurmountable; but
there are very few places which cannot now be photographed, as
where daylight does not penetrate the magnesium flash-light is avail-
able. Probably the first attempt to photograph below the surface of
the earth was made by the writer in the "Blue John" mine in Derby-
shire. This was in 1865, and the photograph was made on a collo-
dion plate, while the mine was illuminated by means of burning
magnesium wire and ribbon. Soon after this Professor Piazzi Smyth
made photographs of the interior of the Great Pyramid. Owing to
the slowness of the plates, and the quantity of magnesium which had
to be burnt, the white fumes interfered very much with the results,
as the want of ventilation in such places made it necessary to wait
for the particles of magnesia forming the mist to settle before a
second plate could be exposed. The quick plates now in use make such
subjects comparatively easy, and one or two good flashes will generally
be sufficient-care being taken, of course, to protect the lens from
the light. When the external air is colder than the interior, the
condition of the lens as to condensed moisture should be noticed.
When daylight, however feeble, is available, it is only a question of
time as to obtaining a picture. A basement floor in which was a
quantity of machinery, and lighted only by one or two small windows,
has been photographed, the exposure lasting twenty-six hours; that
is, the camera was left in the place for that length of time so as to
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MANUAL OF PHOTOGRAPHY.
utilise all the daylight possible (the place was too extensive for arti-
ficial light to be used), and the result was an excellent negative, some
halation around the window being the only defect. Difficult interiors
must be dealt with according to the peculiarities of each case.
In pho-
tographing buildings, such as cathedrals and churches, lenses of long
focus may sometimes be used; but, usually, wide angle lenses are the
best for the purpose, owing to the difficulty of placing the camera
sufficiently far back so as to obtain as much of the interior as possible.
Where windows appear in the picture they should, if practicable, be
covered during the greater part of the exposure.
Impressionism in Photography.-During the past year or two there
has been much discussion as to whether it was legitimate to attempt
to produce by photographic means work in imitation of what is called
the "Impressionist" school of art, the effect in a photograph being
what is called out of focus. Much may be said on both sides of the
question. In art all styles are permitted, and each artist has, as a rule,
a style of his own which, in course of years, may change. The eminent
artist, Sir J. E. Millais, is an instance. In the early part of his career
he was one of the Pre-Raphaelite school, and a comparison of the
work he did at that time with what comes from his brush now will
show quite as great a difference as there is between a photograph con-
taining the most minute detail and one of the very opposite kind. If
we refer to some of the earliest works which have been preserved, the
wall paintings of Pompeii, for instance, we have hard lines and minute
detail. Coming down to a later date, a visit to the National Gallery
will show us work of the earliest period in oil colours, in which the
lines are still hard and the detail well defined. After that period the
style changed, a more naturalistic manner being introduced, and the
lines and tones becoming more blended. We have another contrast
between the work of Canaletti (whose pictures of Venice and street
scenes show hard lines and wonderful "photographic" detail) and that
of Turner (whose later work showed a total absence of detail). His
pictures are "impressions," and are supposed to give the artist's ideas
of the scenes depicted; they are as far removed from Canaletti's style
as the most out of focus photograph is from one giving the sharpest
possible detail. We may take another example in a different style
of art. Van Huysum painted flowers with the most exquisite finish;
and in the present day Fantin paints pictures of flowers equally beauti-
ful, but quite without detail. Some landscape painters give minute
detail in their pictures, representing the colours and form, so they
tell us, as they are shown in nature, while others leave out the detail
and give very little more than the form, and in some cases colour very
far removed from that of nature as seen by other eyes. Some artists
paint the forms just as they see them, while others consider that they
APPLICATIONS OF PHOTOGRAPHY.
303
improve nature by altering the forms. When so much latitude is
permitted in one branch of art, why should not there be equal variety
permitted in another style of art? The work of Rejlander had many
admirers, but in many cases he appeared to work for effect rather
than minute detail; and, in another case, we had in the work by
Mrs. Cameron portraits in the widest contrast to much that is done in
the present day, and yet the work of that artist had many admirers.
Much of the discussion of this subject has arisen through some of
the pictures shown at the Exhibition of the Photographic Society in
the autumn of 1890. The pictures referred to were very much out of
focus; they were printed on rough paper, and were totally unlike
most of the other landscape photographs in the room; and they were
pointed out to the writer with the remark that there "was a great
change in photographic matters when such things could have medals.
awarded to them." An examination of the things referred to showed
that there was something to admire, something quite different from
what had previously been done in photography, and there seemed to
the writer there was no reason why the style of Corot or Milet should
not be imitated in treating such subjects.
In portraiture (apart from photography) no kind of art is superior
to a well-executed ivory miniature; the same effect could not be
obtained on rough drawing-paper. And in photography there is
nothing to surpass a perfect daguerreotype portrait; a portrait on
paper, however smooth or highly glazed, is not equal to it; and an
album portrait may be very good when printed, as usual, on albu-
menised paper, but would not be equally perfect if printed on rough
paper.
Landscape Photography. Judging from the number of unsatis-
factory photographs of landscape subjects to be seen, there is much
room for advice as to how to proceed in the way of improvements.
To succeed fully, the amateur or professional should have some know-
ledge of the rules of art. To obtain a picture something more is
necessary than to place the camera before a scene and expose a plate
just because it looks pretty and "forms a picture." The result to an
artistic eye may be anything but pretty or artistic. The tyro with
his camera and slides, charged with six or a dozen plates perhaps,
naturally makes a stop at the first pretty bit he comes to and exposes
a plate; it may be that within the next hundred yards he finds
another view of the same subject which pleases his eye better, and
another picture is taken; and so on during the day or few hours
he gives to his subjects. The result may be that not one possesses
the true quality of a picture; he may have excellent negatives, but
all may be wanting in what is termed artistic quality or composition.
The scene presented to the eye of the photographer, although he may
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MANUAL OF PHOTOGRAPHY.
be standing in the middle of a road, may be very beautiful; but, if a
photograph be taken from the same point of view, the result would
not be equally pleasing the road straight in front, running away to
a point and opening out to the full width of the plate in the fore-
ground, would be far from artistic. A little consideration would
show that the same scene, taken from a point not far removed, would
have a very different effect. The greatest care, then, should be taken
to consider well what will appear on the plate before making an
exposure. For landscape views the lighting of the subject should be
carefully considered, as when there are great extremes in the lighting
of the distance and that of the foreground, the distance will be lost
in developing the detail in the foreground. Landscapes should
always have some object of principal interest, but this interest may
often be given to a subject by the proper introduction of figures such
as a group of cattle. Here again the greatest care is requisite.
Figures are not always necessary in a landscape; indeed, a figure
badly introduced will mar a picture which in other respects may be
good. Rustic figures may occasionally be introduced with satisfactory
results; but it must never appear that they have been placed for
the purpose.
This defect is seen in many pictures to which
medals have been awarded; but the artistic eye sees at once that
the figures do not belong to the surroundings. Figures are also
sometimes valuable to show the relative sizes of objects. It is
always desirable to study beforehand the landscape subjects to be
photographed. The middle of the day will seldom be the best time.
To get the best results the subject must be studied in just the same
way as an artist would study it for the purpose of painting a picture,
for in no other way can good photographs be expected excepting by
chance. It may be that the photographer cannot give the necessary
time for this process of selection. In this case his good pictures will
probably be few in number. Success in photography can only be
obtained by the same means as in any other art. Landscape photo-
graphy is one of the most fascinating pursuits, and as such deserves
all the study which can be given to it. Architecture affords scope
for interesting work, and to the architect the camera is an aid which
should be often used. Rustic "bits" make pictures of a most pleas-
ing character, and should always be looked for.
It very rarely happens that clouds can be secured on the same
plate with a landscape, but when it is possible to do so the general
effect will be better than when clouds are printed in. Plain paper to
represent sky never looks well, and the paper toned down in printing
looks very little better; therefore negatives of clouds should be
secured whenever practicable. They need not be of large size, nor
necessarily of the size of the plate generally used. Small negatives

MIL
OF
CH.
MICH
J. H. T. ELLERBECK, PHOTO.
A. BROTHERS & CO., HALF-TONE ZINCO.
SÖRFJORD, FROM TYSSEDAL.
APPLICATIONS OF PHOTOGRAPHY.
305
For
can be made into transparencies, and from the transparency two
negatives can be made, giving right- and left-handed effects.
instructions as to printing in skies, see Clouds.
The plate facing this page is from a negative by Mr. J. H. T.
Ellerbeck of Liverpool, and is a very perfect illustration of what a
good landscape photograph should be.
Muybridge's Photographs.-There is no novelty in using a num-
ber of cameras for the purpose of obtaining a series of views of sub-
jects in different positions; but, as applied by Mr. Muybridge, some
very curious and interesting effects have been obtained, showing that
the real motions of animals are very different from what artists have
generally depicted. The illustration on page 306 shows a sketch from
photographs of horses in positions in which no artist would draw them
from life. The horses only are from photographs, but the effect
would perhaps have been more natural if the figures also had been
from photographs instead of from the imagination of the artist. The
photographs were of course taken instantaneously, by means of a
machine carrying a number of lenses, the exposure being effected by
electric contacts as the figures passed. Many of the curious photo-
graphs taken by Mr. Muybridge, when arranged so as to revolve, show
the objects (as they pass in rapid succession before the eye) as if in
motion.
Photo-Meteorology.-Photography has had a very important appli-
cation as the means of recording automatically the readings of the
various instruments used in a meteorological observatory. The varia-
tions of the magnetic needle are made to record themselves by means
of a small mirror attached to the magnet, the light being reflected as
a point on to a sheet of sensitive paper which, on development, shows
the slightest changes throughout the day and night. The barometer
and thermometer also are made to record their own variations.
Portraiture. The best advice on this subject which can be given
to amateurs would, perhaps, be that it is better not to attempt
portraiture. Satisfactory pictures can only be made when the light
is entirely under control, that is, the room in which they are taken
should have blinds and other conveniences, which are not often avail-
able in the case of an amateur. There is no reason why a portrait by
an amateur should not be as good as one taken by a professional
photographer; but it is very rarely the case, owing to the want of
experience as well as of the appliances which give the advantage to
the professional. But although an amateur may find success in any
other branch of the art, there are times when he will certainly wish
to take portraits, and it then becomes a question how to obtain the
best results. If taken in the open air, a shady place should be
chosen so that the eyes need not be directly facing a strong light;
U
306
MANUAL OF PHOTOGRAPHY.

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W
FIG. 108,
APPLICATIONS OF PHOTOGRAPHY.
307
direct sunlight should always be avoided. If suitable preparation be
made, fairly good portraits may be taken in the open air; but some
kind of screen should be placed to prevent too much top light, and
light from one side should be stronger than that from the other. A
photograph taken full-face seldom has a satisfactory appearance unless
the light be so managed that one side has more light than the other.
Excellent effects may sometimes be obtained in a room now that
prolonged sittings are not necessary.
The sitter should be near a
good source of light, and a white reflection should be used to modify
the light. Good effects may often be arranged in a greenhouse or
conservatory. One of the chief things to be avoided is the appear-
ance of "sitting for a portrait." For single figures the head and bust
are to be preferred to full-length studies, and in groups the mistake
should not be made of allowing all the figures to look in one direction.
In many portraits the eyes have an unnatural appearance. This can often
be avoided by the sitter looking at a dark object, which is not too near.
As to the kind of lens to be employed, of course one made for the
purpose of portraiture should be preferred; but the amateur might
use any kind he happened to possess. With the rectilinear type
his results may be as good as if taken with a portrait combination.
Avoid making the head too large, as, no matter what kind of lens be
used, if a small one, there will be distortion if certain limits as to size
be exceeded. In focussing for a head, the eye should always be the
point selected. What has been said must be regarded more as hints
than as directions what to do. The subject of portraiture is too
wide to be dealt with in a few lines, and, no matter how full such
directions might be, the taste and skill of the amateur will determine
what success he may have.
Backgrounds.-The success of a portrait as a picture depends very
much on the background, and this may be said of all other kinds of
pictures where backgrounds are necessary. The portrait painter, if
not pleased with one effect, can repaint his work until a satisfactory
result is attained. Not so, however, in the case of a photograph, for
which only such backgrounds should be used as will not be obtrusive.
Painted backgrounds are seldom the work of skilled artists, and when
architectural effects are attempted, we have too often bad perspective,
and surroundings which are inharmonious; therefore, it is better to
use either plain or graduated shades, and as seldom as possible painted
windows, balustrades, and other imaginary effects.
For vignettes,
a light shade of tone graduated is to be preferred. Canvas is
generally used, but thick paper with care will be equally serviceable.
The painting may be done either in distemper, with sufficient size to
prevent chipping, or oil colour, flatted—that is, painted with colour
mixed with turpentine and oil.
308
MANUAL OF PHOTOGRAPHY.
Large Heads. When the difficulties of taking large heads direct
are considered, it is somewhat surprising that the attempt is ever
made. When the size is the same as life, the difficulties are great,
and only in some degree less when half life-size is the limit. Any
dimension between the half and full size of life is not considered
artistic, since it has the appearance of being "neither one thing nor
the other." A seven-inch head for a man looks as if intended for
life-size, and so with other sizes over four or five inches. If a portrait
is to hang at some height, a size rather over that of life may be
adopted, as the distance diminishes the apparent size. Heads taken
direct the size of life can seldom be made sufficiently perfect to
remain untouched; that is, they require to be "worked up" by an
artist. Mrs. Cameron's work was much praised for its artistic quality,
and this quality consisted in the out-of-focus effect always present in
the portraits. This evidently was the design of the artist, and her
effects were probably due to two causes, viz., the long time required
for the sitting, the wet collodion process being used, and the diffusion
of the focus of the lens. When viewed at a proper distance, Mrs.
Cameron's work had a very excellent appearance, but to most photo-
graphers the want of sharpness was looked upon as a defect. Her
method of working was never imitated to any extent, as it certainly
would have been if the public taste could have been educated in that
direction.
The introduction of gelatine plates has made the production of
large work more practicable. Full-length or half-length figures on
plates 22 × 18, or larger, are made very satisfactorily; but in conver-
sation with a photographer who had paid over one hundred pounds.
for a lens for this kind of work, the writer was informed that "it did
not pay." Seeing that such perfect work can be made by the methods
of enlarging now available, it seems very questionable whether better
results cannot be obtained by enlarging than by any other means. A
head of moderate or small size can be made much more perfect than
any taken direct over two inches; and as the large direct negative
must require much time in retouching, perhaps more time than the
artist would devote to the finishing of the enlarged print on paper,
the advantage would appear to be in favour of enlarging. It may be
said that the retouched negative would give perfect prints without
further artistic labour. That may be true, but the work of the artist
with the brush would excel that of the retoucher.
When negatives are sent
never be “make it life-size."
are not all of the same size.
about one inch longer from chin to hair than that of the adult female.
Therefore it is better always to give the size in inches, and, when
to be enlarged, the instruction should
This term is very misleading, as heads
The head of an adult male is usually
APPLICATIONS OF PHOTOGRAPHY.
309
$
practicable, the measurement should be from the chin to the hair. A
foot-rule should be held so that it just touches the face by the side of
the nose; one end of the rule should appear even with the line of
hair, and the inches read off the scale at the chin. As a check to
this measure, it is well to give also the length from the corner of the
mouth to the inner corner of the eye.
Rembrandt Portraits.-By placing the sitter with the light partly
behind and at the side, a strong effect of light and shade may be
obtained. When carefully done, this produces a pleasing result,
which is supposed to resemble that seen in the portraits painted by
Rembrandt.
The Spectroscope in Photography.-Investigations upon the band
of colours given when white light is separated into its component
elements, have proved of great service in building up the knowledge
of the relation between the constituent rays of white light and the
various sensitive salts in use, and have caused photography to be of
considerable assistance to astronomy and other sciences. In its former
aspect much valuable information has been obtained, both as to what
rays are of most photographic value and the relative sensitiveness of
the bodies employed as photo-sensitive agents, and as to the influence
upon this sensitiveness exerted by colours used in orthochromatic
plates. By its means it has been shown that the greater general
sensitiveness of silver bromide over the other silver salts is due to its
being influenced by a wider range of rays, and much other interest-
ing information has been obtained as to the effects of mixtures of the
haloids and the presence or absence of sensitisers; but in work on these
subjects it is important to take into account the effect of the prisms
and other transparent media through which the light has to pass, that
is, their absorption-spectra must be known and discounted.
In the second place, photo-spectroscopy has given an insight into
the chemical composition, physical state, and motion of celestial
objects. This application rests upon the fact that, while an incan-
descent gas emits rays of a certain refrangibility, it also has the
power of absorbing rays of identical wave-length; so that, when a
glowing solid which emits white light, and would ordinarily give a
continuous band of colour as its spectrum, is surrounded by any kind
of vapour, it will exert its characteristic selective absorption, and so
cause those particular rays to be replaced by thin black lines. By
making the solar or stellar spectrum to fall upon one half of the spectro-
scope slit and photographing it, and then, with the instrument in
precisely the same position, allowing the spectrum of the vapour of a
metal (heated to incandescence in an electric arc) to be photographed
upon the same plate through the other half of the spectroscope slit,
two spectra are obtained exactly under each other; the first is a
310
MANUAL OF PHOTOGRAPHY.
continuous band intersected by dark lines; the second, a series of
lines only, which are characteristic of the element; and, if the dark
lines are due to absorption by the same element as the bright-line
spectrum produced by the incandescent vapour, these lines will coin-
cide exactly. This coincidence is a proof of the presence of this
element in or about the sun or star which gave the dark band
spectrum. With stellar spectra, the stars being but points, they
would produce a mere line of but slight breadth in which cross-lines
would be hardly visible; but Huggins overcame this difficulty by
slightly altering the declination of the telescope. The star travelled
up or down the slit, and thus broadened its band. With nebulæ,
spectra of lines only are obtained, thus showing them to be masses of
glowing vapour similar to the incandescent gases around the electric
arc. The coincidence of the photographs of the lines given in the
two cases will, of course, prove that the nebulæ contain the elements
in question.
As regards the determination of motion in distant stars, this rests
upon the change in wave-length caused by motion towards or from
the observer; but refrangibility is determined by wave-length, so that
alteration in the latter must cause change in the former, and the lines
characteristic of a certain element will not occupy the same position
that they would were the star fixed and the wave-lengths normal.
By photographing the spectrum of a known element side by side with
that of the star, and noting the extent, if any, of variation of the
characteristic line from the true position, the data are obtained for
calculating the extent of motion required to produce the observed
lateral displacement; while the displacement to the right or to the
left of the normal position. indicates the direction in which the star
is moving.
Stereoscope, The. It is a curious fact that comparatively few
persons are aware until their attention is called to it, that their eyes
see two distinct pictures of every object to which they are directed.
A very simple experiment proves this. Hold up the hand at arm's
length and look at one finger held before a distant object, such as a
window bar. Now look at the finger and one image (opaque) will be
seen, but two window bars (transparent). Now look at the window bar,
and two fingers will be seen, both of which are apparently transparent.
Close the eyes alternately, still looking at the finger, and its position
with respect to the window bar will appear to change, shifting from
side to side, as seen by the right or left eye.
This experiment may
be varied in many ways. Take a solid body, and, keeping the head
in one position, make a sketch first with one eye and then with the
other, closing the eyes alternately. On comparing the drawings it
will be found that the two sketches do not agree, and that by "squint-
APPLICATIONS OF PHOTOGRAPHY.
311
ing," the two images (if about 2 inches apart) may be made to
coalesce and form apparently a solid, as seen by the two eyes. This
squinting to obtain the uniting of two dissimilar images is difficult


FIG. 109.

DOTPERBARO HABE DEE IqUPAP[!
FIG. 110.
with some persons without the aid of an instrument. Fig. 109 shows
the result of sketches made as seen by each eye separately. To show

α
b
FIG. III.
a

FIG. 112.
this curious optical effect many geometrical drawings in outline were
made before photographs were used for the purpose. To assist in
viewing these designs, Professor Wheatstone invented the reflecting
stereoscope, the form of which is shown in Fig. 110. It will be noticed
that two mirrors are fixed so that, when suitably dissimilar pictures
are placed at each end, their images are seen as a single picture having
the effect of solidity. The advantage of this form of stereoscope is
that pictures of larger size can be used. Sir David Brewster intro-
312
MANUAL OF PHOTOGRAPHY.
duced an instrument in which half-lenses were used; that is, a lens
was cut in two and the outer edges reversed, as shown in Figs. 111 and

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e
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d
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f
B
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b
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FIG. 113.
But, as the width of the eyes varies in different persons, it
was arranged that the lenses could be adjusted to different distances

M
FIG. 114.
apart. Fig. 113 shows a section of the instrument, and Fig. 114 the
appearance of this early form of the stereoscope. An improved form
is shown in Fig. 115.
Fig. 116 is an engraving from an early stereoscopic print, from which
APPLICATIONS OF PHOTOGRAPHY.
313
it will be seen that the two pictures have been taken at far too great
a distance apart, and the effect in the stereoscope is consequently
unnatural.
The construction of the instrument has been improved in various
ways, both for single slides and for arrangement of a number of
pictures to be viewed one after another; but this once popular optical
instrument is not much used now. This is much to be regretted, as,
when viewed in a suitable stereoscope, this form of picture gives the
representation precisely as the two eyes saw it in nature, but without
the colour. It is scarcely possible that the stereoscope will go entirely
out of use; indeed, at present there appears to be a revival of interest
in stereoscopic photography.
There is always something interesting in the facts concerning the

FIG. 115.
early history of an invention, and the stereoscope is not an exception.
In October 1856, Sir D. Brewster, under the signature "A," wrote
to the Times, pointing out that M. Faye, an astronomer and a member
of the Academy of Sciences, Paris, had communicated to that society,
on October 6th, an account of a new and simple stereoscope, and.
which the Abbé Moigno described in his Cosmos on the 12th of the
same month, as follows:-"M. Faye presented a new stereoscope, of
his invention, of extreme simplicity. It is indeed a simple piece of
cardboard or paper, in which are pierced two holes whose centres are
on the same horizontal line, and at the distance which separates the
two eyes of the person who uses it. In looking through these two
holes, about twelve millimètres wide (less than half an inch), at a
stereoscopic slide, we see but one image, and for that reason we see it
314
MANUAL OF PHOTOGRAPHY.
as much in relief as in the reflecting or refracting stereoscope. This
is certainly a happy idea. The paper or the cardboard of M. Faye
has the effect of making the optic axes rigorously parallel, as if they
were directed to a point situated at an infinite distance. It is for this
reason, and not, as Mr. Grove maintains, by crossing the optic axes
by a forced and voluntary squinting, that the two images are super-
imposed."
Sir David then shows that Mr. James Elliott, of Edinburgh, con-
trived the same thing as early as 1834. Professor Wheatstone,
referring to this, points out that his investigations respecting binocular
vision were published in 1833. Sir D. Brewster, in reply, acknow-
ledges the letter signed "A." to be his, and then cites the fact that
Elliott's and Faye's instruments were alike, and that Wheatstone's was
different; in fact, that they were independent inventors of an instru-
ment for uniting dissimilar pictures. He then quotes from an article
by Wheatstone, in which the name of the painter, Leonardo da Vinci
(who lived in the fifteenth century), occurs, and from which it appears
that, if his observations had taken a slightly different form, he would
have discovered binocular vision. Other names are introduced into
the discussion, which is altogether very interesting, but much too
long to be discussed further here, except to say that there can be no
doubt that Wheatstone produced an instrument for showing stereo-
scopic relief. It is also a fact that Wheatstone's instrument is not
suitable for stereoscopic views as now taken, and that Brewster's
stereoscope in various forms has, after many years, proved a most
valuable scientific instrument.
About thirty-five years ago it was with some authorities a matter of
doubt at what distance apart the two pictures should be taken to
produce the true stereoscopic effect. It was said that, to give great
effect of solidity, a distant view must be taken with the camera at
stations twelve feet apart, and in such cases all foreground objects
must be avoided. For nearer views the distance must be changed
from feet to inches. The late Mr. Dancer, of Manchester, was the
first to point out that the proper position for the station was the
distance between the two eyes, two and a half inches, and he con-
structed a camera with twin lenses, so that the two dissimilar views
could be taken at one operation. These pictures, when viewed in
the stereoscope, give perfect relief in all cases, excepting when only
very distant objects are shown. In such cases very little relief can
be seen; but, such as it is, the effect can be exaggerated by taking
views many feet apart. That Mr. Dancer's was the true method of
taking stereoscopic pictures was doubted, and an interesting discussion
occurred between him, Mr. Sutton, and others, in which details of
experiments were given proving that Mr. Dancer was correct. More-
APPLICATIONS OF PHOTOGRAPHY.
315
over, the fact that all stereoscopic pictures are now taken with lenses
about two and a half inches apart, is one proof of the scientific

accuracy of Mr. Dancer's method. It may be mentioned, however,
that Sir. D. Brewster admitted about the same time that, for taking
FIG. 116.

316
MANUAL OF PHOTOGRAPHY.
portraits, twin lenses should be used, and their distance apart only
that of the two eyes, two and a half inches. No doubt greater relief
can be obtained when views of buildings, landscapes, &c., are taken.
with cameras many feet apart, but the effect is more that of a model
than the real object photographed; and, when objects occur in the
foreground, it is impossible to see them in relief at the same time ast
the more distant parts of the picture are looked at. In taking views
it should always be carefully arranged that some object be well
placed in the foreground, not necessarily near the centre, but at the
sides of the picture. These parts, as they show greater parallax,
assist in the stereoscopic relief, and give reality to the scene.
3
Cameras for stereoscopic work are usually constructed for taking
the two views on one plate (the size of the plate being 62 × 31),
twin lenses being fixed on the camera; but a camera having only one
lens may be used, and the plates need not be larger than quarter-
plate, 4 × 31; or, by making the back of the camera to slide, the
two pictures may be taken on a half-plate, 6½ × 42. But any camera
will answer, provided the small size plate can be used; or, if the
pictures are for the reflecting stereoscope, plates of any other size may
be used. The camera must be placed on a stand with a level top, on
which a line may be drawn along the side of the camera to indicate
the position from which the first picture was taken. The negative
having been taken in this position, the second exposure is made, with
the camera shifted so that the centre of the lens is two and a half inches
from the first position. Then, after adjusting the position of the object
on the ground glass, another line may be drawn on the board at the
side of the camera to show the second position. The lines marked on
the board will show accurately the places for the camera for future
exposures. Portraits may be taken in this manner; but it is
absolutely necessary that there should be no variation in the
expression or in the position of the sitter. Negatives of subjects
for the stereoscope, when two views are taken on the same plate,
give pictures which are pseudoscopic; that is, instead of showing
objects in relief as in nature, they give the opposite effect, and the
prints have to be cut and reversed in mounting. The necessity for
this change may be avoided by suitably arranging the lens, the sliding
back and the front. When only one lens is used there must be a
division in the camera to prevent the pictures overlapping, and when
twin lenses are employed the camera must also have a division for
the same purpose.
When twin lenses are used (that is, when the camera is binocular),
it is necessary that the lenses be exactly of the same focal length.
Experience has shown that the advantage is on the side of the twin
lens system, as it ensures the pictures being identical. There is
APPLICATIONS OF PHOTOGRAPHY.
317
another advantage: each plate will hold two pictures 34 inches
square, the correct size for lantern pictures; and, therefore, dis-
similar views may be taken on the same plate, if the stereoscopic
picture is not required. In using twin lenses it is as well occasion-
ally to see that they are properly adjusted (that is, screwed home),
and that the lenses in their mounts are in their proper places; a very
slight change in the position of the lens will cause defects of focus.
It is a very simple matter to take pictures for the stereoscope when
a binocular camera is used, and there is no extra labour in the
printing; but the pictures are comparatively useless until they are
mounted; at this point there is some trouble, and much care is
required to do the work properly. Amongst amateurs this has pro-
bably had something to do with the unpopularity of stereoscopic work
during the last few years; but it ought not to deter any one from
producing stereoscopic pictures, for they certainly give a more pleasing
representation of a place than a single view, no matter how large it
may be. It must not be forgotten that, by contact-printing, positives
of the exact size for lantern work may be produced.
2, 2
As already stated, prints from negatives taken with a binocular
camera are not in their correct position for mounting. They must be
divided in the centre, and the left hand one placed on the right hand
side of the mount, and vice versû. When taken on plates 63 × 31,
the prints are very near the size required, and very little more than
trimming is necessary; but, whether trimmed before toning, or after,
each print should be marked on the back, so that in mounting each
will have its own pair. Therefore proceed to mark the prints in order,
I, I , 2, , 3, 3*, and so on; the meaning of the marks being that
I and I * are the prints to be mounted side by side, and that 1* is
the left-hand picture. If these marks be carefully made, mistakes in
mounting cannot occur. If they are carelessly done, the prints may
be pseudoscopic instead of stereoscopic. The illustration (Fig. 116)
will serve to show what to avoid, both in taking the negative and in
trimming the print before mounting. The illustration is from nega-
tives which are taken with the stations too far apart. No portion of
the colonnade seen in the right hand picture is shown in the left; it
also shows that the prints were mounted too close, the centres being
very little more than two inches apart. The distance may be 23
inches or 2 inches, but not more nor less. Many persons cannot
3
4
use the stereoscope. They say that they can see the picture better
when one eye is closed. This may arise from the eyes of the person
being closer together or wider apart than the average, and the
stereoscope may not admit of the necessary adjustment; or it may
be that the prints have been unsuitably mounted. Avoid the
mistake shown in Fig. 116, but always allow some portion of the
318
MANUAL OF PHOTOGRAPHY.
object at either side to be seen, not, however, exaggerated, as shown
in the engraving.
As it is necessary in making transparencies for the stereoscope that
the two pictures should be on one piece of glass, the negative must
be cut and transposed if the transparency is to be printed in contact;
but, if the transparency is to be made in the camera, the lenses used
in taking the negative may also be used in making the copies, and
the reversal of position will take place in the camera. The lenses
must be arranged so that adjustments may be made to give the
proper position of the two pictures on the ground glass. The beauti-
ful pictures produced many years ago by the late Mr. Breeze, were
made in a copying camera of the kind referred to.
With care, many
of the effects introduced by Mr. Breeze can be imitated, as, for
instance, in moonlight scenes the moon may be shown; but, as it
would be impossible to photograph any scene by aid of the light of
the moon, the effect must be obtained in another way. That is done
by taking an instantaneous picture of a landscape when the sun is
hidden by clouds, so quickly that, when viewed as a transparency, the
effect must appear as moonlight; that is, no part must be so dis-
tinctly visible as in a daylight picture. To introduce the moon, a
stereoscopic negative of that luminary must be taken with the camera
used in taking the landscape. This can readily be done at the time
of full moon, and the size of the moon will be exactly what is re-
quired for the picture. When the moon is introduced into pictures,
artists almost always exaggerate the size. The moon is a small object
as we see it in nature. This is shown by the fact that it can be seen
through a hole one-tenth of an inch in diameter, held at 10 inches
from the eye.
The size, then, as taken by the twin camera is what
is required for the transparency. We have now to fix the proper posi-
tion for the moon, which naturally must be near where the sun was
supposed to be when the clouds were photographed; therefore, a clear
place must be selected for it, and the print from the original negative
may be taken on the glass to be used for covering the picture, or, if
preferred, a separate glass. Mr. Breeze frequently used three very
thin glasses in his pictures. The glass can be obtained of such thin-
ness that three will be about equal to two pieces of the ordinary
kind.
To obtain stereoscopic pictures of the moon, a telescope (or a camera
with a lens of very long focus) is necessary. A telescope of 5 inches
aperture, and 6 feet focal length, will give a picture of the moon of
about seven-tenths of an inch in diameter at the principal focus. A
landscape or other photographic lens of 30 inches focus will give a
picture of the moon about three-tenths of an inch in diameter. There-
fore it will be seen that, as the image must be enlarged very much to
APPLICATIONS OF PHOTOGRAPHY.
319
make an effective picture for the stereoscope-say at least to 1
inches diameter, there will be much loss of detail if a very small
negative be used; hence the picture taken with the telescope should
have the preference. Owing to the very great distance of the moon
from the earth, it would produce very little stereoscopic effect if two
pictures were taken on the same night with cameras placed 3000
miles apart; but advantage may be taken of what is called the libra-
tion of the moon. It may be seen by close observation that the moon
shows at certain times a little more of her surface on either side,
that is, east and west or north and south. If photographs are taken
at such times, it will be found, on viewing enlarged copies in the
stereoscope, that the effect of rotundity is distinctly brought out,
and a reality of effect produced which can be gained in no other
way. If the views are selected from the times of extreme libra-
tion, the moon will appear as a kind of cylinder with a rounded
end. A good stereoscopic picture of the moon is a very desirable
thing to possess, and is worth much trouble to obtain. Accord-
ing to a statement made by Sir J. Herschel, libration causes an
apparent change of place, as seen from the earth, equal to 52,000
miles, the stereoscopic angle being 12°; that is, the cameras may be
supposed to have been placed that distance apart when the pictures
were taken.
As the distance of the sun is too great for any effect
of libration to be seen, Sir J. Herschel suggested that advantage might
be taken of the sun's rotation on his axis; and as a spot on the sun's
surface is made to shift by one day's motion about 13°, photographs
suitable for the stereoscope might be made. The writer has never
seen a stereoscopic picture of the sun, and he is not aware that
Sir J. Herschel's suggestion has ever been acted on. Photographs
taken at short intervals during a partial eclipse of the sun show
stereoscopic effect of the moon's passage across the sun's disc when
combined in the stereoscope.
By careful manipulation in taking the two pictures, either by the
single or binocular camera, and care in mounting the prints, chiefly by
seeing that their centres are not less than 2 inches or more than 23
inches apart, much pleasure may be derived from stereoscopic photo-
graphy. Robert Hunt wrote thus more than thirty years ago:-
"Even when fully accustomed to the phenomena of the stereoscope,
there is so indescribable a charm in the beautiful pictures that they
are gazed at again and again with increasing admiration."
As these words have additional force when the picture is viewed
as a transparency on glass, it will be convenient here to describe a
method of printing photographs in this form. At the period when
stereoscopic pictures were very popular, Messrs. Ferrier & Soulier
(now Messrs. Levy & Co.), of Paris, produced pictures of this kind
320
MANUAL OF PHOTOGRAPHY.
which were exceptionally beautiful. Their excellence was due in a
great measure to the process used in their manufacture, a process
worked out and really known only to the makers themselves, but
supposed to be a simplified collodio-albumen process.
3
4
To print stereoscopic transparencies, the plates should be 6 x 31.
Having then negatives, &c., of this size, and a printing-frame as
shown in Fig. 117, proceed as follows :—

FIG. 117.
First examine the negative carefully, and note if all the subject
you wish to reproduce is on both portions of it.
Now, in the dark room lay the negative, face upwards, in the
printing-frame; then, holding up the frame by the left hand, arrange
the selected portion of the negative over the aperture of frame by
sliding it either to the right or left by means of the right hand fingers.
Next lay the prepared transparency plate, face downwards, on to
the negative, as shown in Fig. 117, where the diagonal lines represent

FIG. 118.
the negative with the left end over the aperture of frame, and the
lines parallel with the frame represent the transparency plate with its
right end over the opening in the printing-frame.
Now place the back of the printing-frame, Fig. 118, in its position,
and expose to a gas flame for the necessary length of time. Go back

FIG. 119.
to the dark room, unclamp the back of the frame carefully, and take
out the sensitive plate; but, before disturbing the negative from its
position, hold the frame towards the dark room light, and notice
particularly some part of it which touches or rather is opposite one
PRACTICAL HINTS.
321
edge of the square opening of the frame. Now arrange the opposite
ends of the negative and transparency plate over the opening, so that
the counterpart of the former image may be printed, as shown in
Fig. 117; expose as before, and all that is now required is to take the
plate from the frame and develop it in the usual manner.
A little care is all that is necessary for securing perfect adjustment
between the negative and transparency.
The printing-frame, as described above, is made by Mr. Chapman,
of Manchester.
CHAPTER II.
PRACTICAL HINTS.
Accelerator. Any substance used to assist in the development of
the photographic image, e.g., the alkali added to the pyro-developer to
quicken its action, is called an accelerator. The term is generally
applied in working with gelatine plates. In the wet collodion process
the application of heat will accelerate the action of the developing
solution. When it is found that the exposure has not been sufficient,
slightly warming the plate while the developing solution is on it will
increase the density of the image.
Alkaline Development.--The use of an alkali to assist in the
development of the latent image was first introduced by Major Russell,
the author of the Tannin Process, in 1862. With the alkali it was
necessary to use a soluble bromide to act as a "restrainer." Without
the bromide the development was too energetic, and fog was caused.
Ammonia is the alkali generally preferred, but soda and potash are
recommended by some operators. The results are very much the
same whichever alkali is used.
The action of pyrogallic acid alone is very slow, and the addition of
the alkali is to cause a quicker development; the restrainer is used to
keep the action of the developing solution under control.
Anhydrous.—When a substance contains water of crystallisation or
has an affinity for water, as calcium chloride, acetic and sulphuric
acids have, the removal of the water renders the substance anhydrous.
In general, an anhydrous substance is one which does not contain any
water.
Argentometer.-When water contains nothing but silver nitrate,
the quantity of which is not known, the instrument called an argento-
meter will indicate accurately how much silver is present. When,
X
322
MANUAL OF PHOTOGRAPHY.
however, the silver solution has been used (as in the case of a
bath for collodion plates or in the preparation of paper), the solution
becomes contaminated with other matter, and the correct quantity of
silver can no longer be ascertained by means of the argentometer.
But for very rough purposes this convenient little instrument may be
used, since, although the bath may contain ether and alcohol, the
indication of strength in silver may be sufficient. A more accurate
method of testing the strength of a silver solution is to titrate as
chloride with a standard salt solution; but this is rarely necessary in
practice.
Backing Plates. The object of backing plates, as it is termed, is
described under the heading Halation. Any method may be adopted
by which the back of the plate will be prevented from reflecting the
light. Lamp-black mixed with alcohol or with water and rubbed on
the back of the plate may be used, or, if preferred, the following:-
a. Gum arabic
Water
b. Glycerine
Water
I ounce.
4
I
2 ""
Mix the two solutions, and incorporate with it any suitable pigment,
such as drop-black, which may be ground in water. With this paint
the backs of the plates, and allow to dry protected from the light.
Bichromate and Cyanide Poisoning. In working the carbon
printing and other processes in which potassium bichromate is used,
it is next to impossible to prevent contact of the bichromate solution
with the hands; hence, when the skin is cracked or sensitive, ulcers
or a very irritating "rash" may appear. So far as the rash is con-
cerned, the writer's experience has been that the remedy is to cease
putting the hands into the solution. When the rash is very trouble-
some, a dilute solution of carbolic acid in alcohol has been found
effectual; and carbolic soap should be used when washing the hands.
When practicable, india-rubber gloves should be worn, and the hands
should always be thoroughly washed after they have been in the
bichromate solution. With ordinary care this irritating disease may
be avoided altogether.
Potassium cyanide, applied to the skin after the hands have been
touched with tincture of iodine to remove silver stains, will do no
harm to health if the skin is not cracked; but sores may be caused,
and therefore the cyanide should be used with the greatest care.
Broken Negatives.-Negatives taken by the collodion method, if
not too badly broken, may be printed from if the parts are carefully
held together by the edges of the plate with gummed paper, and then
printed under tissue paper in the shade, or by suspending the frame
PRACTICAL HINTS.
323
so that it may be kept revolving while printing. If the negative
should be on a gelatine plate, the film may not be broken, in which
case it may be removed and remounted as described under the head-
ing Stripping Film.
Combination Printing. The most simple form of combination
printing has been referred to under the head of Clouds. To combine
several figures taken from separate negatives in one picture, so as to
give a natural effect, some skill and much patience on the part of the
photographer is necessary. The desire may be to produce a picture of
twenty figures in a room, which also is to be represented with its furni-
ture and decoration, and with the figures occupied so as to look natural.
First of all we must design the picture, and then carefully photograph
the figures, singly or in groups, to fit the design; and the lighting
must be the same as adopted in the sketch; also the figures must be
in their true relative sizes. The room also must be photographed,
and an enlarged negative made to be printed as a background for the
figures. If a photograph cannot be taken, a correct drawing must be
made. A print of each figure must now be arranged and mounted in
the position it is to occupy in the finished picture, and this is to be
used as a guide in printing the figures, which in a case of this kind
will require the aid of an artist to harmonise the whole. Each
negative must now be masked so that only such part as is required
for the picture will be printed and the portions cut out preserved.
To proceed with the printing: First draw a line at one side of the
guide print, and a line also at the bottom. Lines to correspond must
be drawn on the sheet of sensitised paper to be used as guides in
printing in the figures. A printing frame the full size of the paper
must be used. Place the prepared paper on the backboard of the
frame, and upon it arrange the first negative, measuring the distance.
carefully from the side and the bottom to a fixed point on the nega-
tive. If there should be room, two negatives may be arranged and
printed at the same time. The whole of the paper not under exposure
must be carefully protected from the light. The glass of the printing-
frame must now be placed in position, the frame put over, and the
whole then carefully turned over so that the negatives are not dis-
turbed. When the frame is a large one, this can be done with bolts
and the bars wedged down (wedges are preferable to screws) when the
frame is turned. The progress of the printing can be watched in the
usual way, and great care must be taken to have the prints of equal
depth. When all the negatives are printed, the portions of the prints.
cut out must be arranged over the printed parts, and the background
can then be printed in. The greatest care is necessary in every part
of the printing, otherwise dark and light lines will appear around the
figures. It is difficult to produce a work of this kind so perfect that
324
MANUAL OF PHOTOGRAPHY.
no touching-up or artistic finishing is required; but, when printed
on salted paper, such photographs can be finished in water-colour or
black and white, and, in the hands of a skilful artist, the result may
be highly satisfactory. If the work is to be finished in oil colours,
the photograph should be on albumenised paper.
Figures can be introduced into landscapes in such a way as to
appear as if part of the original picture, and, when skilfully done, the
effect is excellent. The difficulties to be overcome are many, the
chief, perhaps, being with the models, as it is not easy to make them
pose or to assume the expression desired. In most photographs of
the kind the figures look as if they had been posed for the occasion,
and there is a photographic appearance about the work which the
artist has failed to conceal. A few works of the kind have been
produced which possess much artistic excellence, thus proving that in
the hands of a skilled photographer a photograph may also be a work
of art. The illustration on the opposite page is from a picture by
Mr. H. P. Robinson, who has given much attention to the production
of pictures of this kind. Two negatives are used in this picture, and
the printing is so carefully effected that no retouching has been
necessary.
Copyright. By an Act of Parliament (25 and 26 Vict. c. 68, s. 1)
it is provided that when the photograph has been made or exe-
cuted for or on behalf of any other person for a good or valuable
consideration, the photographer shall not retain the copyright unless
it has been secured to him by a written agreement signed by the
person for whom it was made; the copyright in the photograph
belongs to the sitter. Therefore, if a portrait is required for publica-
tion or sale for the benefit of the photographer, consent in writing
must be obtained and a money payment of some kind made, the
amount being stated in the agreement. Registration at Stationers'
Hall is necessary to prevent infringements. This is the law of the
The custom amongst photographers as to portraits is, that the
negative is the property of the photographer, and can be destroyed by
him after his sitter has been supplied with copies; but if the negative
be retained, it is exclusively for the sitter's use. This rule applies
also to all kinds of copies.
case.
A photograph of a landscape or of any other kind is protected by
registration, so that that particular work may not be pirated; but this
does not prevent any other person making photographs of the same
objects.
Cracks (to fill up).-Old, and perhaps valuable, negatives taken
by the collodion process are sometimes found to be cracked,—that is,
the film becomes reticulated more or less after they have been stored
away. A little soot applied with the end of the finger will generally

H. P. ROBINSON, PHOTO.
SHIV
OF
MICH
CH.
A. BROTHERS & CO., HALF-TONE ZINCO.
A STRANGE FISH.
PRINTED FROM TWO NEGATIVES.
PRACTICAL HINTS.
325
fill up such cracks, and when re-varnished the negative will be as
serviceable as ever. Storage in a damp place is the probable cause
of cracks of this kind. Insufficient washing after fixing also may
have originated them.
Density. Upon the proper density of the image depends the print-
ing quality of the negative. By experience alone can this quality be
determined when the plate is under development. The necessary
density varies with the purpose for which the negative is required.
For landscapes or portraits absolute opacity may be necessary only in
certain parts, but for some purposes, such as photo-lithography, absolute
opacity in every part is essential, the transparent subject excepted.
Detail. A picture, when correctly exposed and developed, will be
full of detail—that is, each part is correctly seen in sufficient per-
fection; another picture of the same subject, through insufficient
exposure, is said to be wanting in detail, because the parts in shadow
are black, and contain no detail. Over-exposure may produce a similar
defect, but in a different way, as the excess of light may cause the
more delicate details in the picture to be lost.
Developing and Developers.-The action of light on a prepared
plate produces an effect which is invisible, or, as it is termed, latent.
Of the composition of this photographic effect or image we have not
certain knowledge; but we do know that by the application of reduc-
ing agents certain reactions occur, and a picture is formed; in other
words, the image is developed.
The development of the image on the daguerreotype plate presents
a case different from any other process-a vapour of iodine being
employed, in the first place, to make the silver surface sensitive to
light, and then to develop the image the vapour of mercury is used.
As this vapour consists of particles of mercury, it may be assumed
that they adhere to those portions of the plate on which light has
acted, and the unaltered iodide of silver rejects the mercury particles.
In illustration of this idea, Professor Meldola suggests that if a
design be drawn on a sheet of glass in gum-water, and then if a powder
or sand be dusted over the plate, the image would be developed. This
illustration of the production of a picture in molecules is complete, but
it affords no idea of the chemical nature of the compound formed by
the mercury on the silvered plate.
Since the days of Daguerre many substances have been prepared
and used as developers. Talbot made use of gallic acid. Hunt and
Herschel introduced iron. Pyrogallic acid (this substance is not really
an acid, its proper name being pyrogallol), although known since 1831,
was only first used in photography in 1851. Within the last few
years other substances, such as eikonogen and hydroquinone, have
been introduced.
326
MANUAL OF PHOTOGRAPHY.
The action of pyrogallic acid as a developing agent in the wet col-
lodion process is much slower than iron, at least three times, and it
is now seldom employed. For gelatine plates, however, pyrogallol is
largely used, and by some is preferred to eikonogen and other similar
substances.
One of the most energetic of the reducing agents is iron protosul-
phate, used now almost exclusively in the wet collodion process.
Ferrous oxalate produces excellent negatives when used to develop
gelatine plates.
The question as to how the various reducing agents act on the
invisible image is one which has occupied the pens of some of the
best authorities on photographic matters, and the literature of the
subject is very extensive.
The development of the image has been compared to the formation
of the "silver tree," which may be produced by suspending a slip of
zinc in a solution of silver nitrate. The action set up soon becomes
visible on the zinc by the deposition of particles of metallic silver, and
these continue to form and adhere to each other until the whole of
the silver contained in the solution is exhausted. The deposit of
silver from its salt solution may be shown in another way, and is an
interesting experiment when seen under the microscope. A few drops
of silver solution are placed in a cell on the stage of the instrument,
and on the addition of some fine copper filings the silver will be seen
at once to form and attach itself to the particles of copper, building
up a miniature "tree" or fern-like structure. In the case of the
photographic image the particles of silver are deposited in a very
finely divided state, and the density of the picture is caused by the
deposit being thicker on those parts of the plate which have received
the most light. In the case of the collodion picture the film contains
an iodide of silver formed by the combination of the iodine in the
collodion and the silver nitrate in which it is immersed. On exposure
in the camera a change is produced by the action of the light, and
this change is made visible on the application of the developing solu-
tion, which, in this case, is assumed to be iron protosulphate. If a
solution of a proto-salt of iron be added to a solution of silver, the
latter metal is at once thrown down; but when the iron solution is
used to develop the image, the silver contained in the silver nitrate
in the film is deposited in the metallic state only on those parts of
the plate where the light has caused some change in the molecular
condition of the film containing the silver, and it is usual to say that
the picture is built up by the atoms clustering together in proportion
as the light has affected the sensitive film. How the image has been
formed in the first instance by the light is difficult to explain; in fact,
very little is known about it, but that the picture is built up by
PRACTICAL HINTS.
327
atoms or particles of metallic silver can be seen under the microscope,
and the metallic silver can also be shown by gently rubbing the dry
film, which will at once exhibit its character.
A few facts not generally known to the present generation of photo-
graphers may be stated. They are of as great interest now as when
published in 1842, and are contained in a summary of a paper by M.
Ludwig Moser "On the Formation and Development of Invisible
Images." It will be found in Hardwich's "Manual of Photographic
Chemistry," 5th edit., p. 42. A portion only of the summary is
given here :—
"From Moser's experiments we learn that the surfaces of various
bodies are capable of being modified by contact with each other, or by
contact with a ray of light, in such a way as to impart an affinity for
a vapour; and further, that the salts of silver are in the list of sub-
stances admitting of such modification. But the same condition of
surface which causes a vapour to settle in a peculiar manner also
affects the behaviour of the silver salt when treated with a mixture of
nitrate of silver and a reducing agent. Thus, if a clean glass plate be
touched on certain spots by the warm finger, the impression soon
disappears, but is again seen on breathing upon the glass; and if this
same plate be coated with a very delicate layer of iodised collodion
and passed through the nitrate bath, the solution of pyrogallic acid
will often produce a well-defined outline of the figure even before the
plate has been exposed to the light. This experiment is an instruc-
tive one, and shows the necessity of cleaning the plates used in
photography with care. If there be any irregularity in the manner
in which the breath settles upon the glass when it is breathed on, a
condition of surface exists at that point which will probably so
modify the layer of iodide of silver that the action of the developing
fluid will be in some way interfered with.
"Glass plates with collodion pictures on them should be cleaned
very carefully before being used again, or the old impression will
reappear during development. Plates packed in sheets of newspaper
often show the letters in the same way when the pyrogallic acid is
applied. Traces of organic matter, in all probability, are present in
the superficial pores of the glass, and it is only by long soaking in
chemical solutions that these invisible images can be destroyed."
It will be convenient here to give a few hints as to the develop-
ment of gelatine dry plates. The operation is very simple, but until
experience has been gained many failures may occur. It is assumed
that the worker has made himself master of the way of using the
camera and focusing. The necessary exposure will depend on the
kind of lens in use, the size of the diaphragm, the state of the light,
and the make of plate, whether slow or quick. Experience alone is
328
MANUAL OF PHOTOGRAPHY.
required, but a few hints from a friend who has mastered the difficul-
ties would be useful. The plate having been exposed, the carrier
holding it must be opened in a darkened room.
We will suppose
that the plate is an "Ilford," 6 × 4, and that the formula for that
kind of plate is to be used. In a glass measure pour one ounce of
No. 3 solution, and add to it half an ounce of No. 2 solution. Put
the plate, film-side uppermost, into a dish of suitable size, that is,
somewhat larger than the plate, and then pour over it the mixed
developing solution. If it is found that the image shows itself very
slowly, more of No. 2 may be added. The picture should not develop
too quickly. If the exposure has been correct, the film will gradually
darken, and the density may be ascertained by examining it by hold-
ing the plate towards the light. The proper density can only be
determined by trial. The appearance of the plate at the back may
be some guide, as the image shows darker than the rest of the surface.
When it is known that the exposure has been correctly timed, the
full quantities of the two solutions, Nos. 2 and 3, may be used at
once. The object of taking only half the quantity of ammonia, or
even less than half, is to retain some control over the development.
In an over-exposed plate the image will start up at once, and it will
be found on fixing that the image is weak and probably useless. As
soon as it is seen that the exposure has been too great, the developing
solution may be poured back into the glass, and more of No. 3 added,
and with care a fairly good negative may result. In cases of under-
exposure, prolonged development and the use of more of No. 2 solu-
tion may permit a picture to be developed, but the result is too often
that the shadows are dark and the contrasts too great; therefore the
greatest care should be taken to make the exposures correct and to
develop to the proper density. No words can properly convey the
necessary instruction for this; a few plates may be spoiled, but the
information gained will compensate for the loss.
When the picture is fully developed the plate should be rinsed
with water, and then at once placed in the fixing solution, consisting
of sodium thiosulphate ("hypo") 4 ounces, and water 20 ounces.
As soon as all trace of the white film has disappeared, which may be
ascertained by examining the back of the plate, the fixing is complete.
After thorough rinsing, the picture must be "cleared" by flowing
over it sufficient of the solution named for that purpose (see Clearing
Solutions). The object of this part of the process is to remove a yel-
lowish veil, which, under certain conditions, appears after development.
It is sometimes recommended to place the plate when developed in
a saturated solution of alum; when there is any tendency for the
film to "frill" this is necessary, but not otherwise.
It now only remains to thoroughly wash the finished negative, and
PRACTICAL HINTS.
329
this may be done by allowing water to flow over it for an hour or two,
or the plate may be placed in a dish and the water changed frequently.
When many plates are to be dealt with, it is convenient to use a
grooved washing trough, through which the water is changed by
means of a syphon.
The negative should be allowed to dry in a rack, or by standing it
on end on blotting paper. Any attempt to dry it by fire-heat would
cause the film to melt. If, however, it is necessary to dry the plate
quickly, it may be placed in methylated spirit, and after a few
minutes, when all greasiness has disappeared, it may be removed (the
spirit can be used again), and reared up to dry.
The makers of gelatine-bromide plates always recommend that the
formulæ they give should be used. This is, perhaps, excellent advice
to the tyro; but good results on any kind of plate may be obtained
with pyrogallol and ammonia development, and perhaps with any
one of the various methods in use. Failures are more likely to arise
from changing from one kind of plate to another, and experimenting
with various formulæ. It is far preferable to select a plate known
to work well, to persevere with it until its peculiarities are known and
mastered, and to use the developing solution known to give good results
with the particular plate in use. When experience has been gained,
failure is unlikely to occur, no matter what kind of plate may be used.
Gelatine plates are made of various degrees of rapidity, and in
some cases plates of the quickest kinds may advantageously be used;
but for ordinary work the slowest (say, ten times the rapidity of wet
plates) will be found to give the best results. The exposure is more
under control and the development more certain. With the quickest
plates there is less control of the exposure and more depends on the
development. It has been asserted, as the outcome of careful experi-
ments, that no modification of development can correct an error in
the exposure outside certain limits depending on the character of the
plate. This opinion, if proved correct, will greatly emphasise the
necessity for care in the exposure.
In the description of the various processes will be found the
necessary formulæ for development. As already stated, in working
with gelatine dry plates, it is better to use the formulæ recommended
by the makers, but for convenient reference the following may be
useful:
Developing Solution for "Edwards' XL Plates."
No. 1. Pyrogallol
Alcohol (methylated)
Glycerine
No. 2. Potassium bromide.
Ammonia, .880
Water
•
•
I ounce.
7 ounces.
ounce.
120 grains.
I ounce.
7 ounces.
330
MANUAL OF PHOTOGRAPHY.
For use, take one part of No. 1 to fifteen parts of water, and, in a
separate bottle, mix one part of No. 1 with fifteen parts of water.
Equal parts of these two solutions are required when a plate is to be
developed. The dilute solutions will not keep, and should be mixed
just before they are required.
For the "Ilford" Plates.
No. 1. (Stock) Solution.
Pyrogallol
Ammonium bromide
Water
Nitric acid (pure)
No. 2. Liq. ammonia, 880
Water
No. 3. Solution No. 1.
Water
1 ounce.
600 grains.
6 ounces.
20 drops.
3 drachms.
20 ounces.
I ounce.
•
19 ounces.
Equal parts of No. 2 and No. 3 are to be mixed for use. If the
plate is found to be over-exposed, at once remove it from the dish,
and pour over the plate some of the No. 3 solution, which may be
allowed to mix with the solution in the dish. When the develop-
ment is slow, more of the No. 2 solution may be used, and in case
of doubt as to the exposure, take only half the quantity of No. 2, and
add more as required to produce the proper density.
For the Pall Mall plates the makers recommend the following:-
No. 1. Pyrogallol
Sodium sulphite
Citric acid
Water to make
No. 2. Potassium carbonate
Sodium sulphite
Water to make
•
I ounce.
4 ounces.
ounce.
20 ounces.
•
3
2
""
20
To an ounce of water add one drachm of each of the above solutions.
With ammonia the following is the formula for the same plates:
No. 1. Pyrogallol
Sodium sulphite
Citric acid
Water, boiled or distilled, to make
Of the above ten minims equal 91 grains of pyrogallol.
No. 2. Liquor ammonia .880
Water to make
Ten minims of this equal one minim of ammonia.
No. 3. Potassium bromide
Water to make
Ten minims of this equal 91 grains of bromide.
I ounce.
3 ounces.
ounce.
IO Ounces.
I ounce.
IO ounces.
I ounce.
•
IO ounces.
PRACTICAL HINTS.
331
To each ounce of water add ten minims of each of the three
solutions, and to increase density add ten minims of No. 2, if neces-
sary.
With hydroquinone the following formula may be used:-
No. 1. Hydroquinone
Sodium sulphite
Citric acid
Potassium bromide
Water to make
No. 2. Sodium hydrate
Water
160 grains.
2 ounces.
•
60 grains.
40 grains.
20 ounces.
•
160 grains.
20 ounces.
Equal parts of these solutions may be used in cold weather. In hot
weather the solution may be diluted.
With iron the following may be used :—
No. 1. Potassium oxalate (neutral)
Potassium bromide
Water to make
No. 2. Iron protosulphate
Sulphuric acid
Water to make
•
6 ounces.
20 grains.
20 ounces.
8
drachm.
20 ounces.
To three ounces of No. 1 add one ounce of No. 2 (see Hydroquinone).
Dialysis. —The process of dialysis is useful in photography when it
is desired to separate certain salts from colloidal substances, as in the
case of gelatine emulsion. Parchment paper is strained over a vessel
so as to form a kind of dish—the dialyser—in which the emulsion is
placed. When brought into contact with water, the crystallisable
salts pass through the parchment paper, while the colloidal substance
remains in the dialyser.
Diffused Light.-For many purposes in photography direct sunlight
is not desirable. When the processes used were very slow, as was
the case when Daguerre's method was first used, the strongest light
was necessary, but by the quicker processes now practised this is un-
necessary. For portraiture blinds are employed, and, in some cases,
the glass roof is stippled with colour to give the effect of ground glass.
By this means the light is diffused, and the contrasts of light and
shadow are given with the best effect.
Dust.-Whether in the wet or dry processes, one of the most
troublesome annoyances arises from dust particles. Pinholes, comets,
and various other defects are caused by dust; and as for some pur-
poses (such as a screen for the half-tone block process) an absolutely
perfect plate must be used, every care must be taken to avoid dust.
The plates must be carefully brushed, whatever the process may be,
and when gelatine plates are placed in a draught-box, the entrance for
332
MANUAL OF PHOTOGRAPHY.
the air should be protected with cotton-wool lightly placed over the
aperture.
Expansion of Paper.-Most kinds of paper when wetted expand.
This is very observable in paper on which portraits are printed. The
expansion is greater in one direction than the other, and it is there-
fore necessary to cut the sheets so that the defect will be least
observed. If the prints are allowed to dry, then brushed over witlı
the mountant, and again dried, they may be mounted by damping the
mount, when no distortion will be observable. The following diffe-
rences were found in a sheet of paper very accurately measured :-
A sheet of paper, already coated with gelatine and dry, measured
231 x 17 inches. It was then sensitised in the bichromate solu-
171
6
tion and dried at 80° F., when it was found to measure 23 × 1716
inches. The sheet was then printed, inked, and cleared from the ink,
and while wet measured 231 × 171 inches. When dry and finished,
the transfer measured 2215 × 17 inches, showing a loss in length
of one-eighth of an inch, and a loss in width of one-sixteenth of an
inch. The importance of this will be at once seen by those who
prepare transfers for photo-lithography, when several transfers are
required to form one subject and to fit accurately.
3
6
Fog.—The extreme sensitiveness of gelatine dry plates makes them
very liable to show the defect known as fog. As a consequence,
every care should be taken to prevent the access of light to the plate,
excepting through the lens at the time of exposure.
A very minute
hole in any part of the camera, dark slide, or in the diaphragm slot
may admit light, or the sliding parts of the dark slide may be in
fault. Therefore in a strong light the camera and slide should be
kept covered as much as possible. The plate may be fogged through
the light in the dark room not being of the proper quality. Light fog
may be produced by any of these causes. There is another defect,
which is chemical, and may arise in the process of manufacture of the
plates or in developing. A tinge of greenish colour around the sides
of the plates is called green fog, and often occurs when ammonia is
used in developing and under prolonged development. This defect
does not always interfere with the printing qualities of the negative.
An appearance around the sides is often seen in some plates after
development which is very like the defect referred to, but is evidently
caused by tarnish, owing probably to the age of the plate.
careful rubbing with the finger while the plate is wet the defect may
be removed. Red fog was at one time a defect in dry plates, but is
now seldom seen. Green fog may sometimes be removed by soaking
the film in a solution of potassium bichromate. Hydrogen peroxide.
may also be used.
By
Plates which have been exposed to light and thereby "fogged," so
PRACTICAL HINTS.
333
as to be useless for ordinary purposes, may, as stated in the British
Journal of Photography, be restored by treatment as under. Take-
Chromic acid
Potassium bromide
Water
30 grains.
60
IO ounces.
The plates are to be immersed in this solution for five minutes,
thoroughly washed, and then allowed to dry. Another solution is as
under, and is applied in the same manner :—
Potassium bichromate.
Hydrobromic acid (sp. gr. 1.4)
Water .
I ounce,
2 drachms.
IO ounces.
After treatment with either of these solutions the plates are much
less sensitive than before, but if, after thorough washing, they are
treated with one of the alkaline or the chromatising solutions, much of
the sensitiveness will be restored.
Plates which have been exposed in the camera may be restored for
use again if treated with either of the solutions named, but the
immersion must be more prolonged. Care must be taken while
drying the plates that no white light acts upon them.
In placing plates in the dark slide, care should be taken not to be
too near the light, and as little light as possible should be used in the
room. In developing, also, the plate should be kept away from the
light, and until the image begins to appear it is not safe to expose
the plate to the yellow light.
Freezing Mixtures.-The following mixtures will be found useful
when the temperature requires to be reduced. When snow is avail-
able, the addition of common salt (sodium chloride), two parts by
weight of the chloride to five of snow, will reduce the temperature
from 84° F. (20° C.) to 5° F. The vessel containing the fluid to be
reduced in temperature must stand in the freezing mixture.
The mixtures given below will also cause intense cold :—
(
Ammonium muriate
Potassium nitrate
Water.
reduces the temperature from + 50°F. to + 10° F.
Ammonium nitrate
Water.
5 parts
5
16
I part
I
reduces the temperature from + 50° F. to + 4° F.
Sodium sulphate
Nitric acid (dilute)
3 parts
2
"
334
MANUAL OF PHOTOGRAPHY.
reduces the temperature from + 50° F. to
snow still lower temperatures may be produced.
Snow .
Sodium chloride
Ammonium nitrate
will reduce the temperature to 25° F.
Snow .
Calcium chloride
30° F. With ice or
12 parts
5
5
"}
"
4 parts
5
""
-
reduces the temperature to 40° F. Other mixtures may also be
used.
Frilling. This defect is caused by the expansion of the gelatine
film, and as some plates are more liable to frill than others, some
peculiarity in the process of manufacturing the plates may be the
cause. If the sample of gelatine is too soft or is partly decomposed,
or if the film is too thick, frills may appear after the developing or
fixing solutions are used. If the developing solution is used too
warm, the film may begin to leave the edges of the plate. In a case
of this kind an edging of grease or india-rubber may be a remedy.
When there is a tendency to frill, the plates should be placed in a
bath of alum or chrome-alum before or after development, using a
5 per cent. solution of the alum. Steeping in spirits of wine is also
said to prevent frilling. A thorough washing should follow the use
of alum or chrome-alum before subjecting the plate to the action of
an alkaline solution. Gelatine plates rarely, if ever, frill with the
ferrous-oxalate developer.
Halation. This is a defect frequently seen when a dark object is
strongly lighted from behind-as dark foliage against a light sky;
the light encroaches on the dark edges and causes a fringe of light
around the object. The effects of halation are also seen in photo-
graphs of interiors where a bright light shines through a window,
but are still more noticeable when the interior is dark, as in some
churches, and the exposure is consequently prolonged. One of the
causes is reflection from the back of the plate. Many remedies have
been suggested; amongst others, backing the plates—that is, coating
them on the back with an opaque colour, which can be easily removed
before development. In plates thickly coated with emulsion the
defect is not so noticeable. When an interior is sufficiently lighted
by windows not shown in the picture, it may be practicable to cover
the window facing the camera for most of the time during an ex-
posure. Of course it is desirable that the picture should be taken
when the sun does not shine directly on such a window. One of the
best means to remove the defect is to carefully rub the over-exposed
PRACTICAL HINTS.
335
part with methylated spirits of wine, using a tuft of cotton-wool or
lint. In addition to backing the plate, it is said that staining the
film with erythrosine, I part to 500 of water, is an effectual remedy.
The following may be used as a reducing solution for halation-
Potassium ferricyanide
Water
•
20 grains.
2 ounces.
To about half an ounce of this solution add two drops of "hypo"
(4 ounces of "hypo" to 20 ounces of water) when required for use.
It may be applied locally with a camel's-hair brush. After soaking in
water, the plate must be well washed.
High Lights.—In a portrait, if well lighted, there should be parts
which are brighter than the rest of the face-on the forehead and
nose, for instance; they are called high lights. If they do not exist
in the negative, the "retoucher" generally marks such parts with the
pencil. In a landscape the high lights give brilliancy to the picture.
Hygiene in Photography.—Although in the present day there is
nothing in the practice of photography so prejudicial to health as
was the case when the fumes of mercury were always present during
the development of the daguerreotype plate, there is still the necessity
for care. Probably the small quantity of ether fumes breathed during
an ordinary day's work when collodion was in general use did very
little, if any, harm. Care should be taken, when large plates are
coated with collodion, that the room should be properly ventilated,
otherwise the ether fumes cause a very unpleasant effect on the eyes.
The writer has never heard of any permanent injury from breathing
ether fumes, nor has he experienced any injury himself after a long
use of collodion; the effect on the eyes is unpleasant, but soon passes
off. The fumes of ammonia in the small quantities used in develop-
ing dry plates can do very little harm; but when the strong ammonia
is used, care should be exercised in every possible way. The bottle
containing the fluid should never be unstopped when held near the
face, and the fumes should be breathed as little as possible.
As collodion is so little used by amateurs, it is scarcely necessary
to advise them to be cautious, while in large establishments every care
will be taken to avoid accidents by fire; the stoppers of bottles should
be looked to, and care as to naked lights observed.
Intensifying. For certain purposes a negative taken in the ordinary
way is not sufficiently intense—that is, the image is not completely
opaque. For general purposes the collodion negative, when redeveloped
or intensified with pyrogallic acid, is all that can be desired, but when
used in photo-lithography, or other mechanical processes, the image
must be black in order to obtain the best results. A collodion nega-
tive developed with iron may be intensified by steeping in a saturated
336
MANUAL OF PHOTOGRAPHY.
solution of mercury bichloride; but as water alone will only take up
a small quantity of the mercuric salt, it will be found that equal parts
of mercury and ammonium chloride (sal ammoniac) will be found
more energetic in its action. When the negative has changed to
white, the intensification is complete, and the plate must now be
thoroughly washed. If not completely washed stains will occur in
the next operation.
A dilute solution of ammonia poured over the
film will instantly change the colour to black, when the plate must
be again thoroughly washed. Incomplete washing causes the image
to fade in course of time, although the film may have been varnished.
Exposure to the atmosphere for a few hours will often be sufficient to
cause the image to bleach in parts, so that varnishing must be resorted
to as soon as the plate is dry. An unvarnished negative must not be
used on silver paper, nor on a bichromate preparation, since stains
may be thus produced.
Instead of ammonia chloride, hydrochloric acid may be used, one
ounce of acid to six ounces of water, to which the mercury bichloride
must be added: the undissolved portion may remain in the bottle.
Instead of ammonia for blackening, "hypo" will answer the same
purpose. Potassium cyanide, to which silver nitrate has been added,
may also be used after the plate has been bleached.
The following formula for collodion negatives developed with iron,
and, if necessary, redeveloped with pyrogallic acid, will be found
preferable to the bichloride solution :
Potassium ferricyanide
Lead nitrate
Water
4 ounces
3
65
which can be used repeatedly, and should be occasionally filtered.
This will change the colour to a light yellow, and when sufficiently
intense-which can be seen by transmitted light-the plate should
be well washed in running water. The washing will take out the
yellow colour, leaving the film white, but it is not always necessary
to reach this point. Then take-
Ammonium sulphide
Water
4 ounces
12
•
>>
and pour it over the plate until the film is completely blackened, that
is, until no patches of the bleached picture are visible on the back of
the plate. The ammonium solution should not be used twice. If
any part of the picture appears discoloured where clear glass should
be, a cleaning solution of—
Nitric acid
Water
I drachm
12 ounces
PRACTICAL HINTS.
337
may be poured over the plate. This must be used carefully, other-
wise the density of the image may be injured.
Other methods are in use for intensifying collodion negatives, but
the above are quite efficient.
Owing to the difficulty experienced in determining when a gelatine
dry plate is sufficiently developed, many negatives are found to be too
weak to give good prints. Unless the negative is very much under-
exposed, a good result for printing may be obtained by careful intensi-
fication. The negative must be very thoroughly washed to avoid the
risk of stains.
Intensification with silver nitrate is not always successful on gela-
tine plates, but the following is recommended by Mr. E. Howard
Farmer :-
No. 1. Silver nitrate
Distilled water
•
No. 2. Potassium bromide
Water
No. 3. Sodium thiosulphate ("hypo ")
Water
I ounce
12 ounces.
3 ounce.
2 ounces.
2
""
6
Add No. 2 to No. 1, and after washing the precipitated silver bromide
thoroughly by decantation, dissolve it with agitation in No. 3. The
muddy liquid thus obtained is filtered or placed aside for a day and
the clear solution decanted off; it is then made up to 16 ounces with
water, and kept for use.
To intensify a plate, wash after fixing, and flood with the following
mixture:
Sulpho-pyrogallol .
Water
The above silver solution
40 minims
2 ounces
60 minims
to which is added, immediately before use, about 30 minims of 10 per
cent. ammonia solution. If the silver shows no tendency to reduc-
tion, add more ammonia, or, if it be thrown down immediately, use
less. With a little experience, a peculiar browning of the liquid
shows when sufficient ammonia has been added. Rock the plate, and
apply fresh solution as the density increases. Finally, place the
negative for a short time in the fixing bath and wash.
Gelatine plates may be intensified with mercury bichloride. The
solution as recommended for wet collodion plates, diluted, will answer,
but it will be better to mix a solution specially, say-
Mercury bichloride
Ammonium chloride
Water
IO grains.
IO
I ounce.
Y
338
MANUAL OF PHOTOGRAPHY.
When sufficiently intensified, wash thoroughly and blacken with
Ammonia
Water
I ounce.
9 ounces.
If found to be too energetic, the solution of mercury may be reduced
with water; one-half water would in most cases be strong enough, as,
if fully bleached, the negative may become too dense.
The following method for intensifying a gelatine plate immediately
after fixing is recommeded by Mr. W. Brooks:-Wash the negative,
after fixing, for at least half an hour. Make a saturated solution of
alum, and add to it one ounce of citric acid. To one part of this
stock solution add three or four parts of water, in which soak the
plates for a few minutes. Take two drachms of the alum and citric
acid solution, and add six grains of pyrogallic acid and a few drops of
a 20-grain solution of silver nitrate. Use this to intensify the plates
in the ordinary way by holding the plate in the hand; watch the
result, and stop just before full intensity is gained, as it will be
denser when dry. Now wash the plate, replace it in the "hypo"
fixing solution for five minutes; and after thoroughly washing it
again, immerse it in the diluted alum and citric acid solution. If the
plate has been allowed to dry, intensification by this method may be
adopted, but it is better done while wet.
Mealiness. -Paper that has been floated in a bath containing too
little silver will appear, when printed, with an irregular surface and
deficient in brightness. This is frequently the case with some kinds
of ready-sensitised paper. If the paper itself is of good quality, and
sensitised a short time before it is used, the remedy is to add silver
to the bath. It occasionally happens that the albumen dissolves in
the bath, and this will cause mealiness.
Negatives. The illustrations, figs. 120 and 121, show one of the most
simple experiments in photography, and they also illustrate the differ-
ence between a negative and a positive. The figures show that a leaf
placed on a piece of sensitive paper will produce a negative if exposed
to light long enough to leave the impression on the paper, and that this
negative, if fixed and made semi-transparent with wax, will produce a
positive when exposed to light in the same way. The first photo-
graphs were produced in this manner. A sheet of paper sensitive to
light, or a plate of glass, as in the collodion, gelatine, or other
processes, and exposed in the camera, yields a negative when the
object copied is a landscape, portrait, or other subject; but by using
the camera as described in another section, a positive may be made
from the negative. The fact that in pictures taken as described the
lights are the reverse of nature constitutes them negatives.
Over-Exposure.-When a plate has received an excess of light

PRACTICAL HINTS.
339
through the lens, it is said to be over-exposed. In some cases there is
no remedy for this. In the wet collodion process an over-exposed
plate can seldom be made into a good negative; but in some cases,
when the exposure has not been very excessive, the picture may be
saved by careful redevelopment or intensifying. In the case of
gelatine plates, the effect of over-exposure may often be corrected by
varying the proportions in the developing solutions. The picture
will flash up too soon when the exposure has been over-long, and the
resulting negative will be weak unless most carefully manipulated
while under the action of the developer. It is, however, strongly
FIG. 120, Positive.
FIG. 121, Negative.
controverted whether over-exposure can be properly corrected by this
or any other means. The evil can, at best, be only somewhat miti-
gated, in the opinion of some writers on this subject.
Pinholes.-The small transparent spots often seen in all kinds of
negatives are called pinholes. The causes of these are various. In
wet collodion plates the defects are chiefly due to dust and excess of
silver iodide in the bath solution.
In gelatine plates the cause may arise from dust, or defects in the
preparation of the plates; they can scarcely arise during develop-
ment.
340
MANUAL OF PHOTOGRAPHY.
Positive. This term is applied to all photographs which, when
viewed by reflected light, appear with the lights and shadows as in
nature. A transparent positive is a picture on glass or other diaphan-
ous material which necessitates the view being seen by transmitted
light. The term was at one time chiefly used to indicate a picture
on glass specially developed to be seen by reflected light (the same
when seen by transmitted light became a weak negative). All lan-
tern slides are positives.
Reduction of Density. Since the introduction of gelatine dry
plates the possibility of getting too much density in the negatives has
been much more probable than with collodion negatives, when addi-
tional density is given by re-development and the requisite intensity
obtained without difficulty. With gelatine, the necessity for using
a weak light, and the veil which causes the film to have a greater
density than the finished negative will require, make the difficulty of
judging the proper depth much greater than in some other processes.
From these causes it happens too often that greater density is obtained
than is desirable, and this excess must be removed or the resulting
prints will not be satisfactory. So many methods are in use for
reducing the density of over-developed negatives that it is difficult to
select the best. In the writer's own practice the following is generally
found sufficient; it is also used as a clearing solution :-
Alum
Sulphuric acid
Iron protosulphate
Water
I ounce.
3 ounces.
20
As a clearing solution it is merely necessary to use sufficient to cover
the plate, and then return the solution to the bottle. To reduce
density the solution may be poured on and off till the required reduc-
tion is effected.
The following solution is also recommended as a means for reducing
very dense negatives:-
!
Potassium ferricyanide
Water
•
I ounce.
IO Ounces.
The negative should be placed in a dish with sufficient water to cover
it; then take one drachm of the ferricyanide solution and an equal
quantity of the "hypo" solution used for fixing; pour the water out
of the dish into the glass with this mixture, and then return to the
dish. More of the mixture may be added if the first quantity
does not cause sufficient reduction. The plate must be thoroughly
washed.
PRACTICAL HINTS.
341
The following is recommended by Mr. Spiller :-
a. Alum
•
Copper sulphate
Common salt
Water
·
b. Saturated solution of common salt.
4 ounces.
4
8
40
""
་་
Both solutions should be filtered and the negative immersed in equal
parts of a and b. Watch the effect of the reduction. When com-
plete, rinse in a fresh quantity of solution b., and then thoroughly
wash.
Prints on bromide paper may be reduced in the same manner as
negatives. By using a solution of copper sulphate, to which a little
salt has been added, bromide prints and untoned prints on salted
paper may be entirely bleached out, but the image will reappear if the
paper is exposed to strong light.
Reduction invariably interferes with the due gradation of density,
and should therefore be used with caution.
Reflected Light.-When a portrait is taken with the light coming
in one direction (as from the window of an ordinary room) the effect
of contrast is too great, and it becomes necessary to modify it by
means of reflected light. This is done by placing a white sheet or
white paper at a suitable distance from the sitter, care being taken
that there is not too much reflection, or the effect will be unpleasing.
A little reflected light, judiciously used, is generally advantageous in
a portrait. Reflected light is also useful in making copies as tending
to equalize the effect and, in some cases, to get rid of the roughness
of paper. Reflected light is often used in making transparencies in a
copying camera, a sheet of white paper being placed at a suitable
distance in front of the camera. A silvered mirror may be employed
for the same purpose. In the solar camera the light is reflected from
a mirror, but it is seldom that a mirror can be used in an ordinary
glass house, as the window bars interfere with perfect reflection.
Residues.—The prevention of waste of the precious metals is very
desirable. In the case of silver and gold the quantity used in the
processes of photography is very large, and the loss, which is usually
also very large, may be considerably lessened. In all large establish-
ments every care is taken to save solutions and paper cuttings where
silver or gold have been used; but the amateur, whose operations are
on a small scale, too often considers it not worth the trouble to col-
lect his waste. This is a mistake, as it occupies very little time to
put all spoilt prints and cuttings and papers which have been used
for filtering silver solutions into a bag. The "hypo" used for fixing.
and old toning solutions should not be thrown away, as in course of
342
MANUAL OF PHOTOGRAPHY.
time sufficient will accumulate to be worth sending to the refiners.
In a paper print only about 3 per cent. of the silver originally used
in its preparation is left in the picture; so that 97 per cent. of the
metal is lost if no care be taken to collect the waste. The waste in
other directions is also very great, but much of it may be easily pre-
vented. Paper prints should always be placed for some minutes in a
dish with plenty of water previous to toning; the water poured into
a jar; and a solution of common salt, or, preferably, hydrochloric acid,
added thereto. The milky solution thus formed is allowed to become
quite clear by settling. The water is then poured off, leaving the
silver chloride at the bottom. The water from the next washing may
then be added and treated in the same way until the chloride has
collected in quantity sufficient to be removed, washed, and dried.
The quantity of silver recovered from paper of the ready-sensitized
kind will be very small when compared with that specially prepared.
The sodium thiosulphate solution used for fixing should be poured
into a receptacle of wood or earthenware having a tap at a few inches
from the bottom, which will serve to draw off the upper part of the
solution after the silver sulphide has subsided. Potassium sulphide
(liver of sulphur) is added in solution and the silver precipitated. The
solution may be tested by taking a little in a test-tube; if on the
addition of a few drops of the sulphide no further precipitate is
formed, the solution may be drawn off and thrown away. As the
mixture of sulphide and "hypo" has an unpleasant odour, the vessel
containing it should be kept in the open air.
As the sodium thiosulphate solution used for fixing gelatine plates
dissolves all the silver not reduced in forming the negative and can
be used repeatedly, it becomes rich in silver, and should be thrown
into the tub to be reduced by potassium sulphide.
In establishments where the collodion process is still used and
when the plates in use are large there is considerable room for waste.
The sink over which the plates are developed should be large and
deep, preferably of earthenware; they may be obtained fitted with a
plug, which permits the washing water to be collected and, after the
sediment has subsided, to be drawn off into the waste-pipe. If the
plug is simply withdrawn much of the sediment will be carried down
the waste-pipe with the water. This is prevented by quickly substi-
tuting for this plug another which is made of lead pipe, and which
has a hole about half an inch in diameter an inch or so above the
level of the sink bottom. This permits the water to run off and
prevents the disturbance of the sediment. The iron used in develop-
ing the plates gives rise to a highly argentiferous deposit, which, after
drying, may be sent to the refiner. The developing solution remaining
on the plates may be thrown into a separate receptacle or into the
PRACTICAL HINTS.
343
sink, but the deposit of silver being richer than when mixed with
the water, it is better to keep it separate. The cyanide bath used for
fixing should also be kept and treated with potassium sulphide.
The films from spoilt collodion plates or old negatives should be
preserved and thrown into the bag with the paper cuttings.
Old toning solutions may be poured into a large bottle, and a
solution of iron protosulphate added to throw down the gold. When
sufficient has been collected the sediment may be filtered out.
The films of unvarnished plates, which have been removed by
steeping in weak nitric acid and water, should be kept and burnt
with other residues. The acid solution should also be kept, and the
silver recovered by adding a solution of common salt.
The various kinds of waste may be treated to recover the gold and
silver, but as the cost of reduction, if sent to a refiner, is so small, it
is not worth the trouble entailed in doing it at home.
There are other ways of treating the waste, but the above will answer
every purpose, and the silver recovered will amply repay the trouble.
It is estimated that at least 75 per cent. of the silver used may be
recovered.
It is a common practice to use sodium chloride (common salt) to
precipitate silver from solutions, but as that salt has the power of
dissolving silver chloride when there is a large excess of sodium
chloride, it is better to use commercial hydrochloric acid, which does
not dissolve the silver chloride.
Saturated Solution.-For many purposes in photographic manipu-
lations it is convenient to have solutions containing as much of certain
substances as can be held in solution. In such cases the solution is
said to be saturated. The quantity which can be retained in solution
by the fluid depends on the temperature. Water when cold will
usually retain less of the substance than when hot, and in some cases
the solution on cooling will part with the surplus in the form of
crystals, leaving the water saturated. Some salts dissolve readily,
while others require to be frequently agitated in the water. When
no more of the substance can be dissolved the solution will be "satu-
rated;" the surplus crystals may be left in the vessel and more
water added as required until all the substance is dissolved. If
merely poured on to the crystals the water immediately surrounding
them will be saturated, but all above will contain very little until the
whole is agitated; and in some cases this must be frequently done
to obtain saturation. The process is facilitated when the substance
to be dissolved is suspended in the fluid; then, as solution occurs,
the denser fluid will sink and the water will be self-saturated. In
all cases where saturated solutions are referred to the substances and
fluids require to have been treated as explained here.
344
MANUAL OF PHOTOGRAPHY.
The following Table of Solubility will be found useful, as by its
aid it may be seen at once how much of the substance will be taken
up at the temperature shown :—
DR. JANEWAY'S TABLE OF THE SOLUBILITY OF PHOTOGRAPHIC
CHEMICALS.
ABBREVIATIONS.—s., soluble; ins., insoluble; sp., sparingly; m., moderately;
v., very; dec., decomposed.
CHEMICALS.
WATER.
COLD
ALCOHOL.
59° F.
212° F.
One part of-
Parts.
Parts.
""
27
Acid, citric
gallic
oxalic
pyrogallic
•
is soluble in
•
0.75
.6
V.S.
IOO
•
11
3
m.s.
S
I
V.S.
19
33
3.5
V.S.
V.S.
tannic
6
V.S.
V.S.
•
>>
Alum
25
10.5
V.S.
ins.
chrome
ΙΟ
dec.
ins.
Ammonium, bromide
""
1.5
0.7
sp.s.
carbonate.
""
4
dec.
m.s.
chloride
""
3
V.S.
sp.s.
iodide
I
0.5
m.s.
nitrate
>>
0.5
V.S.
V.S.
Barium, nitrate
Cadmium, bromide
iodide.
8
3
...
•
V.S.
V.S.
m.s.
V.S.
V.S.
V.S.
""
Copper acetate
Gold chloride
"1
15
5
sp.s.
""
sulphate
Gold and sodium chloride
Iron iodide (ferrous)
perchloride
protosulphate
and ammonia sulphate.
2.6
0.5
ins.
V.S.
V.S.
V.S.
V.S.
V.S.
m.s.
V.S.
V.S.
sp.s.
""
V.S.
V.S.
V.S.
>>
1.8
0.3
ins.
3
0.8
ins.
Iodine.
Lead acetate
chloride
nitrate
7000
m.s.
""
1.8
0.5
m.s.
11
11
v.sp.
33
ins.
2
0.8
ins.
19
""
Lithium bromide.
iodide
Magnesium nitrate
Mercury bichloride
cyanide.
Potassium acetate
V.S.
V.S.
m.s.
V.S.
V.S.
m.s.
V.S.
V.S.
in.s.
11
16
2
V.S.
12.8
"
3
ins.
0.4
V.S.
V.S.
bicarbonate
3.2
dec.
ins.
,
bichromate
ΙΟ
99
1.5
ins.
bromide
1.6
I
sp.s.
carbonate
I
0.7
ins.
""
"2
cyanide
2
I
m.s.
;)
ferricyanide
ferrocyanide
iodide
""
3.8
2
ins.
11
4
2
ins.
O.S
0.5
m.s.
21
PRACTICAL HINTS.
345
DR. JANEWAY'S TABLE (continued).
WATER.
CHEMICALS.
59° F.
212° F.
One part of
COLD
ALCOHOL.
Parts.
Parts.
Potassium nitrate
4
0.4
ins.
oxalate
11
""
"1
sulphate
sulphite
3
V.S.
ins.
permanganate
20
•
3
ins.
"1
9
4
45
ins.
sp.s.
""
sulphuret
Silver, nitrate
oxide
Sodium, acetate
""
bromide.
bicarbonate
carbonate
2
I
sp.s.
""
0.8
0.4
m.s.
闻
​""
v.sp.s.
v.sp.s.
ins.
**
•
3
I
m.s.
I.2
0.5
in.s.
I 2
dec.
ins.
1.6
0.25
ins.
citrate
""
iodide
""
nitrate
""
phosphate
19
↑ "
sulphite .
V.S.
V.S.
sp.s.
•
0.6
""
0.3
m.s.
""
1.3
0.6
sp.s.
6
2
ins.
•
>>
sulphate.
thiosulphate ("hypo ")
tungstate
Uranium, nitrate
2.8
0.4
ins.
4
0.9
sp.s.
I
V.S.
ins.
4.0
2.0
ins.
V.S.
V.S
m.s.
""
A
Zinc, bromide
chloride
""
iodide.
""
V.S.
V.S.
m.s.
0.33
V.S.
m.s.
V.S.
V.S.
V.S.
""
Sizes of Drops.—It frequently occurs that the quantities of fluids
to be used are given in drops, and as the drops of different fluids vary
very much in size errors may be caused when more than a very few
drops are required. The following table, given by Dr. Eder, shows
the number of drops required to make a cubic centimètre:-
Water
20
Hydrochloric acid
20
•
Nitric acid
27
Sulphuric acid
28
Acetic ether
38
Castor oil
Olive oil.
•
Oil of turpentine
Alcohol
Ether
44
47
55
62
•
83
If 140 drops of sulphuric acid are required, divide that quantity by
28, which gives 5 as the number of cubic centimètres required, and
as I cubic centimètre equals 17 minims, it is easy to convert that
quantity into English measure.
Specific Gravity.-By using an instrument called a hydrometer the
specific gravity of a fluid may be determined with sufficient accuracy
for photographic purposes. A more accurate method is by using a
specific-gravity bottle, which is made to hold 1000 grains of distilled
water.
When used, the bottle is filled with the fluid to be tested,
346
MANUAL OF PHOTOGRAPHY.
placed in the balance, and weighed against a brass weight sold with
the bottle. Equilibrium is restored by adding the required weight
to the lighter side of the balance. If the addition is made to the
pan with the brass weight, it is added to the 1000; if to that with
the bottle, it is subtracted therefrom. The resulting figure is the
specific gravity required. The temperature of the fluid should be
about 60° Fahr.
Studios or Glass-rooms.-To the professional photographer questions
of the greatest importance are the aspect of his studio or glass-room
and the plan of its construction. To a very large extent these points
must be determined by the position in which the structure is to be
built. Probably every form in which such a place could be contrived
has been adopted, and good results obtained in each; as, when the
operator has determined the best way to overcome the difficulties of

FIG. 122.
the form of his room, he will do good work, and in another place
would have to unlearn his previous experience. Rooms with ridge
roofs and glass all round, roofs with high pitch, roofs with low pitch
and high or low side-lights, have been built. The last novelty which
the writer has seen is the room at the People's Palace, London, where
photographic work is done without a top-light, the glass being all on
one side of the room and very high, and the shade side of the subject
being illuminated by reflected light. Over another part of the room
there is a top-light, to show the difference in the two effects. Of the
results of the high side-light illumination the writer is unable to
speak, as he has seen none of the work done there. At the time
when the slow photographic processes were used it was of the utmost
importance to have as much light in the room as possible, but much
less light has been needed since the introduction of the quicker
methods; hence the glass is now often ground or made dull by thin
PRACTICAL HINTS.
347
By
paint on the inside. This, of course, gives a very soft effect.
means of blinds the light is entirely under control, so that the skill
of the artist is shown in the manner in which it is managed. Very
little can be said by way of instruction as to the construction of glass
rooms, as the circumstances of each case must be considered.
The amateur in attempting portraiture has many difficulties to
encounter, particularly when his roof is the clear sky. Outdoor por-
traits are of very little value when there is no means of controlling
the light, but this difficulty is to a large extent met by Houghton's
Lawn Studio, shown in Fig. 122, which seems in many ways to be
all that the amateur need have. The question of backgrounds and
accessories must be left to individual taste, but it may be remembered
that the less ornament there is about a portrait the better.
Very effective portrait studies may often be made in conservatories
or greenhouses.
Symbols. The following is a Table showing the symbols and
atomic weights of the elements-
Name.
Symbol. Atomic
Name.
Symbol.
Weight.
Atomic
Weight.
Aluminium
Antimony
ZE
Al
27
Nickel.
Ni
58.5
Sl
I 20
Niobium
Nb
94
•
Arsenic
AS
75
Nitrogen
N
14
Barium
Beryllium
Bismuth
Ba
137
Osmium
Os
199
Be
13.6
Oxygen
()
16
Bi
210
Palladium
Pd
106
Boron
B
I I
Bromine
Br
So
Phosphorus
Platinum
P
31
•
Pt
·
195
Cadmium
ca
I 12
Potassium
K
39
Caesium
Cs
133
Rhodium
Rh
104
Calcium
Ca
40
Rubidium
Rb
85.4
•
Carbon
C
12
Ruthenium
Ru
104
•
Cerium
Ce
141
Samarium
Sm
150
Chlorine
Cl
•
35.5
Scandium
Sc
44
Chromium
•
Cr 52.2
Selenium
Se
79
Cobalt
Co
59
Silicon.
Si
28
Copper
Cu
•
63.4 Silver
Ag
108
Didymium
Di
146
Sodium
Na
23
Erbium
Er
166
Strontium
Sr
87.5
Fluorine
F
19
Sulphur
S
32
Gallium
Ga
69.8
Tantalum
T'a
182
•
Germanium.
Ge
72.3 Tellurium
Te
128
Gold.
Au
197
Terbium
Tr
148
Hydrogen
H
I Thallium
TI
204
Indium
Iodine.
In
II3.4
Thorium
Th
232.5
I
127
Tin
Sn
118
Iridium
Ir
193
Titanium
Ti
48
Iron
Fe
56
Tungsten
W
184
Lanthanum
La
139
Uranium
U
240
•
Lead
Pb
207
Vanadium
51.3
•
Lithium
Li
7
Yttrium
Y
90
Magnesium.
Manganese.
Mercury
Molybdenum
Mg 24
Ytterbium
Yb
173
Mn
Hg 200
55
Zinc
Zn
65
Zirconium
Zr
Mo 96
348
MANUAL OF PHOTOGRAPHY.
In some cases the symbols are composed of letters taken from the
Latin names of the elements, as-Antimony, Stibium; Copper, Cup-
rum; Gold, Aurum; Iron, Ferrum: Lead, Plumbum; Mercury,
Hydrargyrum; Potassium, Kalium; Silver, Argentum; Sodium,
Natrum; Tin, Stannum.
Weights and Measures.-The photographer in his formulæ has
seldom to consider more than grains and ounces, or, in the metric
system, grammes and cubic centimetres; but as German and French
formulæ (the systems used in other countries need scarcely be con-
sidered in this matter) must in most cases be converted from one
system into the other before they can be used by English and
American photographers, it is a matter for serious consideration
which of the two systems should be preferred or whether a com-
promise should be adopted. A very large part of the scientific
literature comes from the continent of Europe, and as the metric
system is used throughout that literature, it becomes a matter of
necessity that the English-speaking men of science must be familiar
with the terms used. Also, a very large number of Englishmen re-
ceive part of their education in some foreign university, where they
are compelled to use the metric system, and, as a consequence, in the
scientific literature of England and America the metric system is used
to a much larger extent than was the case only a few years since.
The effect of this is to make a large part of what is written very
difficult to understand unless the trouble be taken to convert one
kind of measure or weight into the other. The great bulk of the
people of this country and America are no nearer now to the adoption
of the metric system than they were at the time the English Parlia-
ment made its use permissive. It has been suggested that a joint
commission of Englishmen and Americans should be appointed to
settle this question. If that course were taken there can be very
little doubt what the decision would be. "Scientific" men would
form that commission-men to whom the metric system is familiar and,
of course, by them considered the best. But suppose a commission of
"non-scientific" men, say business men, formed a similar commission, it
may be asked, Would they arrive at a similar decision? Meanwhile an
informal "commission" has sat and deliberated on this momentous
question, and the decision they have arrived at appears to meet the diffi-
culties so far as they concern photographers in all parts of the world.
+
At the meeting of the Photographic Convention held at Chester in
June 1890 a report on this subject was read, and the following
"Recommendations" were unanimously adopted :-
"A. Weights and Measures.—1. If the metric system be used,
weights will naturally be expressed in grammes, and measures in
cubic centimetres.
PRACTICAL HINTS.
349
(C
2. If the English units be used, the minim and the drachm
should not be employed at all. All weights should be expressed
either in grains or decimal parts of a grain, or in ounces or fractions
of an ounce; all measures in fluid grains, or in fluid ounces and
fractions of a fluid ounce.
"B. Formulce.-3. Formulæ should give the number of parts of
the constituents, by weight or measure, to be contained in some
definite number of parts, by measure, of the solution. The mixture
can then be made up with (a) grammes and cubic centimetres, or (b)
grains and fluid grains, or (c) ounces and fluid ounces, according to
the unit selected.
(C
4. The standard temperature for making up solutions should be
15° C. or 62° Fahr. No appreciable error will be introduced by the
fact that these two temperatures are not quite identical.
(C
5. Formulæ should give the quantities of the constituents to be
contained in a parts of the finished solution, and not the quantities
to be dissolved in a parts of the solvent. When a solid dissolves in
a liquid, or when two liquids are mixed, the volume of the solution
or mixture is, as a rule, not equal to the sum of the volumes of its
constituents. The expansion or contraction varies with the nature of
the solids and liquids and the proportions in which they are brought
together. In making up a solution, therefore, the constituents should
first be dissolved in a quantity of the solvent smaller than the required
volume of the finished mixture, and after solution is complete, the
liquid, cooled if necessary to the ordinary temperature, is made up to
the specified volume by addition of a further quantity of the solvent.
"6. It is very important to specify in the case of liquids whether
parts by weight or parts by measure are intended.
The equival-
ence between weight and measure only holds good in the case
of water and liquids of the same specific gravity: a fluid ounce of
ammonia solution or of ether weighs less than an ounce; a fluid
ounce of strong sulphuric acid weighs nearly two ounces.
"7. Whenever possible, formulæ should give the quantities of
the constituents required to make up 10, 100, or 1000 parts of the
solution.
"8. When a mixture (e.g., a developer) is to be prepared just
before use, from two or more separate solutions, it is desirable that
the proportions in which the separate solutions have to be mixed
should be as simple as possible—e.g., 1 to 1, 1 to 2, 1 to 3, 1 to 10.
I
"9. When metric units are employed the original French spelling,
gramme,' should be used in preference to the contracted spelling
'gram,' in order to avoid misreading and misprinting as 'grain.'
350
MANUAL OF PHOTOGRAPHY.
(C
Weighing and Measuring.
"A brief description of the correct methods of weighing and
measuring may be of service to photographers who have had no
laboratory training.
Measuring.—The correct reading is the horizontal tangent to the
meniscus; that is, the horizontal line which touches the lowest point
of the curved surface of the liquid in the case of water and all liquids
which wet glass, or the highest point of the curved surface in the
case of mercury and similar liquids. When the liquid is so opaque
that the meniscus cannot be seen, the reading must be taken at the
apparent horizontal surface of the liquid. The measuring vessel
should be exactly vertical, and the eye of the observer should be
exactly on a level with the surface of the liquid.
Weighing. To assume that the weights in the two pans are
equal when there is a distinct deflection of the index of the balance
towards one side is obviously incorrect. To take the weights as
equal when the beam is at rest, and there is no deflection at all, also
gives untrustworthy results. The balance should be made to vibrate,
and the weights in the two pans are equal when the index makes
equal excursions on either side of the position of rest, which is usually
the centre."
All who are interested in this subject will find a most valuable
article in Sir John Herschel's "Familiar Lectures,” p. 419.
The following tables of the English and metric systems will be
found convenient for converting the one into the other.
taken from the British Journal Almanack, 1890.
They are
THE METRIC SYSTEM.
In the French decimal system, Greek prefixes are used to denote the
multiples of the units, and Latin prefixes the fractional parts of the units.
The Greek prefix Deka means
19
IO units.
ΙΟΟ
1,000
10,000
""
""
Hecto
Kilo
Myria
""
The Latin prefix Deci
""
ro of a unit.
Centi
Milli
180
7000
""
""
To give an illustration of this in a measure of length (the metre)—
Myriamètre
Kilomètre
= 10,000 metres.
=
1,000
""
Hectomètre
Dekamètre =
100
ΙΟ
Mètre
Decimètre
Centimètre =
Millimètre
I metre.
of a metre.
100
""
1000
""
PRACTICAL HINTS.
351
And so on with other units-such as the gramme, with its various prefixes;
and the litre, with those by which it is qualified.
For general purposes it will be found to be sufficiently near to consider a
metre as 391 inches, and a decimetre as 31% inches.
In order to aid in the more ready introduction into practice of the decimal
means of calculating, the relative values in inches from the millimètre to the
mètre are given :—
Millimètre.
Mètre.
Inches.
Centimètre.
Mètre.
Inches.
I
6
8
9
Centimètre.
I
|| || || || || ||
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2.3622
2.7560
9
.09
3.1497
3.5434
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.19685
.006
.23622
Decimètre.
Mètre.
Inches.
.007
.27560
.008
.31497
.009
.35434
Mètre.
1 2
IO*
.02
3
.03
4
.04
5
.05
1.5748
1.9685
Inches.
.3937
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I
.I
3.937I
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7.8742
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15.7484
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19.6855
23.6226
27.5597
31.4968
9
.9
35.4339
I metre
39.3685
1
But what is the mètre itself? It is the standard of length, of which the
100
¯¯¯¯¯¯ of a quadrant of the earth's meridian is equivalent to 39'371
inches (De la Rue).
The standard of the weights by which chemicals are calculated is the
gramme, which is, roughly speaking, the equivalent of 15 grains.
The unit of fluid measurement is the cubit centimètre, based upon the
gramme, the weight of one gramme of water at maximum density being
termed one cubic centimètre.
The proportions of fluid measurements on this basis will be apparent by
the following table :—
Names.
Millier or tonneau
Weight of Water.
I cubic mètre
I hectolitre
Avoirdupois Weight.
2204.6 lbs.
Quintal
No. of Grammes.
1,000,000
100,000
220.46 lbs.
Myriagramme
I0,000
IO litres
22.046 lbs.
Kilogramme or kilo
1,000
I litre
2.2046 lbs.
Hectogramme
ΙΟΟ
I decilitre
3.5274 ozs.
Dekagramme
IO
IO C. centimètres
•3527 ozs.
Gramme
I
I c. centimètre
15.432 grs.
Decigramme
.I
1
10
1.5432 grs.
Centigramme
.ΟΙ 10 C. millimètres
.1543 grs.
Milligramme
.001
I C. millimètre
.0154 grs.
FRENCH FLUID MEASURES.
The cubic centimètre, usually represented by "c.c.," is the unit of the
French measurement for liquids. It contains nearly seventeen minims of
water; in reality, it contains 16.896 minims. The weight of this quantity of
water is one gramme. Hence it will be seen that the cubic centimètre and
the gramme bear to each other the same relation as our drachm for solids
352
MANUAL OF PHOTOGRAPHY.
and the drachm for fluids, or as the minim and the grain. The following
table will prove to be sufficiently accurate for photographic purposes :—
17 minims (as near as possible).
I cubic centimètre
2 cubic centimètres
34
""
3
""
4
6
51
68-
85
102
or I drachm
8 minims.
"
I
""
25
I
>>
""
42
119
I
>>
""
59
8
""
136
2 drachms 16
""
9
153
2
""
33
>>
ΙΟ
170
2
""
50
>>
20
340
,,
OOOON OUAW
510
40
680
""
""
5
I
I
ounce
40
o drachm 30 minims.
3 drachms 20
850
I
60
90
100
1020
= 1190
1360
1530
""
2 2 2 CO C
3
= 1700
>>
3
>>
ounces
I
T 36 H4
6
I
IO
O
50
وو
40
""
30
20
""
THE CONVERSION OF FRENCH INTO ENGLISH WEIGHT.
Although a gramme is equal to 15.4346 grains, the decimal is one which can
never be used by photographers; hence in the following table it is assumed
to be 15% grains, which is the nearest approach that can be made to practical
accuracy :-
I gramme
3
1 2 3 4+ 5O N∞ a
15 grains.
30층
​461
""
6135/55
19
or I drachm I grain.
པ
77
6
922/
HH
I
""
17 grains.
I
""
""
32 235
7
107
I
""
""
47
""
123 1/1/1
1389
"
>>
738
ciko+ponkocko
1893
""
,,
2 drachms 3
""
9
IO
II
12
13
14
12345678 9
15
16
17
18
19
20
?>
>>
154
169/
184
2001
2159/
""
3
231
246/
>>
""
261/
277층
​""
""
2929
""
""
308
30
462
>>
1 2 2 2 2 mm com ++++57
34
""
49/2/2
وو
4층
​20층
​دو
3
51
4
4
4
4
SI6
172∞
235
35 9/1
aho Thombo mko
,,
وو
62/2
21층
​37 1/1/0
52/
CTWO|HO|ACIJU
""
""
8
""
""
42
40
616
ΙΟ
16
""
وو
80
90
ICO
582888
50
770
I2
""
50
>>
60
924
,, 15
24
""
70
1078
""
,, 17
58
>>
وو
= 1232
1386
= 1540
20
>>
""
32
,, 23
16
,, 25
""
40
""
PRACTICAL HINTS.
353
ENGLISH WEIGHTS AND MEASURES.
APOTHECARIES' WEIGHT.
Solid Measure.
20 grains
3 scruples
= I scruple =
1 drachm
20 grains.
60
""
480
""
8 drachms = I ounce =
12 ounces = 1 pound = 5760
Fluid.
60 minims = I fluid drachm
8 drachms = I ounce
20 ounces = I pint
8 pints
= 1 gallon
Symbol.
f. 5
f.
0. 5
gall.
The above weights are those usually adopted in formulæ.
27
All chemicals are usually sold by
AVOIRDUPOIS WEIGHT.
grains = 1 drachm = 27 grains.
16 drachms = 1 ounce = 4373
16 ounces
= 1 pound = 7000
""
""
Precious metals are usually sold by
24 grains
12 ounces
TROY WEIGHT.
=
I pennyweight = 24 grains.
20 pennyweights = 1 ounce
= I pound
480
= 5760
>>
NOTE.—An ounce of metallic silver contains 480 grains, but an ounce of
nitrate of silver contains only 437 grains.
FRENCH WEIGHTS AND MEASURES,
AND THEIR EQUIVALENTS IN ENGLISH.
I cubic centimètre 17 minims nearly.
13 1/1/10
28.4
50
100
1000
""
19
""
""
or I litre, to
61 cubic inches
= I drachm.
I ounce.
I ounce 6 drachms 5 minims.
= 3 ounces 4 drachms 9 minims.
= 35 ounces I drachm 36 minims.
The unit of French liquid measures is a cubic centimètre.
A cubic centimètre of water measures nearly 17 minims (16.896); it weighs
15.4 grains, or I gramme. A cubic inch of water weighs 252.5 grains.
Z
354
MANUAL OF PHOTOGRAPHY.
The unit of French weights is the gramme to 15.4 grains; thus a drachm
(60 grains) is nearly 4 grammes (3.88). An easy way to convert grammes into
English weight is to divide the sum by 4, which gives the equivalent in
drachms very nearly thus :-
Grammes.
Drachms.
0%.
100 =
4
25 = 3
Drachm. Grains.
I +
43
INDEX.
ABERRATION, chromatic, 45
of form, 46
spherical, 44
of thickness, 48
Absorption, laws of, 19
--spectra, 19
Accelerators, chemistry of, 30
definition of term, 32i
Acid, acetic, as restrainer, 28, 30
manufacture and use of, 251
Acids, characteristics of, 251
Actinic rays, 19
Actinometers and exposure tables, 205
Hurter and Driffield's actino-
meters, 207, 208
Watkin's actinometer, 206
Watts' exposure tables, 205, 206
formula for using, 206
Alabastrine process, 67
Albert-type, 68
Album or carte" portraits, 299
Albumen, 251
process, 68
substratum, 69
Albumenised paper, 252
Alcohol, 253
methyl, 254
Alkaline development, 321
Alpha paper, 254
Aluminium, 254
Amber, 254
Amido-benzene, 256
Ammonia, 254
as fixing agent, 255
in intensifying, 31
sulphide intensifier, 32
Ammonio-citrate of iron, 262
Ammonium bichromate, 255
bromide, 255
carbonate, 255
chloride, 255
Ammonium iodide, 255
nitrate, 255
oxalate, 256
sulphide, 256
sulphocyanate, 256
Amphitype, 70
Angle of view, 41
Anglol, 256
Anhydrous, 321
Aniline, 256
process, 71
Animal charcoal, 256
Aperture, working, 40
angular, 40
Aplanatic lens, Steinheil's, 51
Aplanatism in lenses, 51
Application of photography, 294
Aqua fortis, 274
Aqua regia or hydrochloric acid, 256
Arago, address to Chamber of Depu-
ties, 3
Archer, collodion used by, in 1851,
15
Architectural photography, 294
Argentometer, 232, 321
Aristotype, 71
Artotype, 68, 72
Asphalt, solubility of, 20
Asphaltum, 257
Astigmatism, 49
Astronomical photography, 294
apparatus for, 297
eclipse photographs, 296
Rutherfurd's moon, 298
Aurin or corallin, 257
Autoglyphic process, 72
Autotype process, 15, 20, 72
BACKGROUNDS, 307
Backing plates, 322
Balance, 206
355
356
INDEX.
Barium bromide, 257
chloride, 257
nitrate, 257
Baths and dippers, 208
Bellows, 209
Benzene or benzol, 257
Benzolene, 257
Bichloride of mercury, 272
Bichromate of potash, 277
poisoning, 322
Bitumen of Judea, 1, 257
action of light on, 2
process, 76
Black lines, 77
varnish, 292
Bleaching-powder or chloride of lime,
258
Blue process (ferro-prussiate), 105
Boracic acid, 57
Borax, 257
in toning bath, 33
Brenzcatechin, 278
Broken negatives, 322
Bromide printing process, 78
of potassium, 292
Bromine, 257
Buckle's brush, 209
Burnishers and rolling machines, 210
lubrication of prints for, 210
CABINET portraits, 299
Cadmium bromide, 257
iodide, 257
chloride, 257
Camera, "Thornton-Pickard," 218
Camera lucida, 2
obscura, invention of, I
use of, by Daguerre, 7
use of, by Talbot, 7
Canada balsam, 258
Canvas, printing on, 81
Caoutchouc, 270
Carbon process (autotype), 15
Pouncey's, 83
Carbonate of potassium, 277
Cardboard, 275
Cartes de visite, 299
Catalysotype, 84
Catechol, 278
Celerotype, 84
Celloidin, 258
Celluloid, 258
Cellulose, 258
Ceramic photographs, 85, 110
Changing boxes, 225
Chemistry of photography, 17
China clay, 271
Chloride of lime, 258
of potash, 277
Chloro-bromide process, 87
Chloroform, 258
Chlorophyll, 258
Chromate of silver, 258
Chromatype, 87
Calotype, 80
Camera, 210
Billcliff's, 214
Chapman's "British," 214
copying and enlarging, 224
Daguerre's, 211
>>
"'detective or "hand," 220
double extension, 219
Kinnear's, 213
Kodak," 220, 221
roll-holder for, 222
M'Kellan's, 213
Miller's "Adelphi," 223
"pin-hole," 38
"radial," 222
simplest form of, 211
stands and tripods, 226
stereoscopic, 219
swing-back and swing-front, 55,
218, 219
Chromium - potassium sulphate
chrome alum, 259
Chromo-collotype, 87
photographs, 87
Chromotype, 87
Chrysotype, 87
chemistry of, 34
Citric acid, 259
Cleaning glass, 67, 87, 91
Clearing and reducing solutions, 88
Clouds, 259
how to print-in, 300
Coffee process, 88
Collodio-albumen process, 89
-bromide process, 90
-chloride of silver process, 90
Collodion, 259
emulsion, 90
pellicle, 90
process, 90
best kind of glass for, 91
defects in negative, 96
developing solution for, 94
fixing image, 95
or
INDEX.
357
Collodion process, fog of two kinds, 96
95
97
how to coat plates for, 92
how to re-develop negatives,
how to rectify silver bath, 96
how to varnish plates, 95
kind of bath for solution, 93
oyster shell marking, 96,
·
positives, 95
silver bath for, 93
to clean glass for, 91
water for, 93
Collographic printing, 98
Collotype, 98
104
best kind of paper for, 103
care of and cleaning ink rollers,
cleaning plate, 103
damping, 103
drying oven for plates, 99
etching plate, 102
ink for printing, 102
kind of gelatine for, 100
kind of glass for, 98
marking position for paper, 103
masking plate for printing, IOI
method of printing, 98
preparation of plate, 100
principle of, 98
printing from plate, 101
printing without margin, 104
rolling up or inking plate, 103
temperature in drying, 101
varnish for, 104
Colouring lantern slides, 104
Combination printing, 323
Robinson's picture, 324
Composite portraits, 300
Composition, 300
Compressed gas, 62
Condenser, 227
Contretype negative, 104
Copper, 260
salts, printing with, 35
sulphate, or blue vitriol, 260
Copyright, 324
Corallin (or aurin), 257
Corrosive sublimate, 272
Cracks, to fill up, 324
Crystal cubes, 104
Cyanide of potassium, 277
poisoning, 322
Cyanotype, 104
Cyanotype, discovered by Herschel, 105
formulæ for, 105
DAGUERREOTYPE process, 106
fixing by "hypo" of soda, 2
gilding by sel d'or, 6
how to copy a, 108
method of cleaning, 108
permanence of, 108
Daguerre's Manual or History of Pho-
tography, 3
Dark room, 227
Defects in lenses, 44
Density, 31, 325
Depth of focus, 43
Detail, 325
Developers, acid and alkaline, 28
influence of strength of, 26
Developing and developers, 325
E. M. F., in, 29
formulæ for, 329, 330, 331
illustration of, 326
instruction for, 328
Meldola's experiment, 326
Moser's images, 327
theory of, 20, 27
Dextrin or British gum, 260
Dialysis, 331
Diaphragms and stops,"282
ratio between apertures and focal
length, 229
"uniform system," 282
uses of, 40, 41, 45, 49
Diazotype or primuline process, 172
Diffused light, 321
Dihydroxybenzene, 267
Dippers and baths, 208
Dishes and trays, 229
Dispersion by lenses, 39
Distance, 301
Distortion, 48
Double dark slides and changing boxes,
225
Doublet lenses, 52
Dropping bottles, 229
Drying gelatine plates, 108
Dry plate making, 109
processes, 109
Dust, 321
Dusting-on process, 110
Dyes as sensitisers, 24
EAU de Javelle, 260
Ebonite, 261
358
INDEX.
Eburneum process, I10
Eikonogen, 261
Electric arc lamp, 58
light, 55
inflammation due to, 57
Wilde's discovery in, 56
Electro-chemical reversal, 27
Electro-motive force of development, 29
Electro-phototypy, III
Enamelling paper prints, III
Emery, 262
Encaustic paste, 262
Enlarging and copying, 112
artificial light for, 112
formula for, 43
simple methods for, 112, 113
table for, 114
Eosin, 262
Erythrosin, 262
Ether, 262
Ethoxo-lime light, 63
Expansion of paper, 332
Exposure tables and actinometers, 205
FADING of invisible image, 25
Ferric ammonium citrate, 262
ammonium oxalate, 262
oxalate, 262
Ferridcyanide of potash, 277
Ferro-prussiate or blue process, 105
Ferrous oxalate, 262
sulphate, copperas, or green vit-
riol, 262
Ferrotype or energiatype, 114
Ferrotypes, 115
Film photography, 115
Fixing, 115
negatives, chemistry of, 30
prints, chemistry of, 34
Flare in lenses, 50
Flatness of field, 47
Fluoresceïn, 263
Fluorotype, 116
Focal length, 42
Focus, 41
depth of, 43
equivalent, 41
visual and chemical, 45
Focussing and focimeter, 229
cloth, 230
glass or magnifier, 231
screen, 231
substitutes for ground glass, 231
Fog, 332
Fog, to restore fogged plates, 333
Formic acid, 263
Formula for enlarging, 43
for focal length, 42
Fothergill process, 116
Freezing mixtures, 333
Frilling, 334
Fuming albumenised paper, 182
GALLIC acid, 263
first used by Talbot, 14
Gay-Lussac, address to Chamber of
Peers, 5
Gelatine, 263
oxidation of, 20
test for quality, 264
to purify, 264
Gelatino-bromide process, 116
Bennett's improvements, 116
drying plates, 118
Eder's method, 118
emulsion on paper, 118
formula for, 117
keeping plates, 118
kind of gelatine to be used, 118
kind of light to be used in pre-
paring emulsion, 117
Paget prize awarded to Wilson,
117
use of gelatine by Maddox, 116
Gelatino-chloride paper (Ilford), 119
fixing, 119
stability of prints, 120
toning bath for, 119
Glass, 264
Glass-room and studios, 346
Globe lens, 50
Glucose or grape-sugar, 264
Glycerine, 262
Goddard, J. F., discovery of use of
bromine, 6
Gold, chloride, 265
hyposulphite, 265.
printing process, 120
toning with, 33
trichloride, printing with, 35
Green photographs, 121
Ground glass, 265
Gum-arabic or gum acacia, 265
dammar, 265
lac, 282
Gum-gallic process, 121
Gun-cotton, 279
Gutta-percha, 266
INDEX.
359
HALATION, 334
Head-rests, 232
Heliography, 121
High lights, 335
Historical sketch, I
Honey process, 121
Horn silver, I
Hydrochloric acid or spirits of salt, 266
Hydrofluoric acid, 266
Hydrogen dioxide, 267
sulphate, 290
Hydrometer, 232
Hydroquinone, 267
268
formula for developing solution,
method of preparing, 267
Hydroxylamine, 269
Hygiene in photography, 335
"Hypo" eliminators, 269, 289
Hyposulphite of soda, 270, 285
286
experiments with, by Herschel,
first use of, by Herschel, 285
necessity for using strong solu-
tions, 289
Schützenberger's note on new
acid, 288
ILFORD, gelatino-chloride paper, 119
Image, aberration of form of, 46
reversal of, 25
size of, 43
latent, 14, 325
virtual, 41
Impressionism in photography, 302
India-rubber, 270
Indian-ink outlines, 121
Instantaneous shutters, 232
adaptors for, 234
drop, 232
235
236
duration of exposure tables,
fan for, 234
Kershaw's, 233
measuring rapidity of, 235,
Noton's, 234
speed indicator, 234
Thornton-Pickard's, 233
Intensifying, 335
chemistry of, 31
formulæ for, 336, 337
Iodide of potassium, 278
Iodine, 270
Iodine, use of, in fixing prints, 34
Iridescent photographs, 122
Iris diaphragm, 236
Iron, 271
ammonio-citrate of, 271
salts, reduction by light, 20
use of, 34
Isinglass, 271
JENA glass, 271
Jew's pitch or asphaltum, 257
Juniper resin or sandarac, 282
KALLITYPE, 122
care in printing, 123
chemical reaction in, 125
formulæ, 123, 124
No. 2, 124
Kaolin or China clay, 271
Kennett's pellicle, 125
LAMPS for dark rooms, 237
Landscape lenses, 49
photography, 303
Lantern slides, artificial light for, 127
colouring, 127
making, 125
toning, 127
Lavender, oil of, 271
Lead, 272
nitrate, 272
salts in intensifying, 32
Leimtype, 127
Lenses, 39
aplanatic, 51
astigmation in, 49
axes of, 40
defects in, 44
focus of, 41
symmetry in, 52
Level indicator, 237
Lichtdruck, 98
Light, actinic rays of, 19
18
36
continuing action of, 21, 62
electric, 55
in photography, 55
oxidation and reduction by, 19, 20
oxy-hydrogen, 61
physical and chemical action of,
physical and chemical nature of,
refraction of, 38
Lithium chloride, 272
360
INDEX.
Litho-heliogravure, 127
Litmus, 272
Liver of sulphur, 272, 278
Luminous spot in lenses, 50
MAGIC (or optical) lantern, 238
photographs, 121, 128
Magnesium, 272
flash-light, 65
light, 63
first use of, 65
manufacture of, 64
Mass, action of, 22, 25
Mastic or gum mastic, 272
Mealiness, 338
Meisenbach process, 128
Mercuric chloride, 272
Mercury or quicksilver, 273
salts in intensifying, 31
Meta-gelatine, 273
new excise regulations, 273,
Methylated spirit, 253, 273
274
Micro-photography, 129
Mosstype, 129
Mounting and mountants, 129
in optical contact, 131
Mounts, 274
Muriate or hydrochlorate of ammonia,
255
of lime, 257
Muriatic acid, 266
Muybridge's photographs, 305
NEGATIVES, 338
illustrations of, 339
Nitric acid, 271
Nitro-hydrochloric acid, 256
OBERNETTER'S process, chemistry of,
23, 35
etching process, 131
Objectives, 49
Oil of lavender, 271
Optical or magic lantern, exhibition of
opaque objects with, 241
with, 241
experiments in exposures
first use of, by Dancer, 239
interchangeable jet for, 241
"Novelty" lantern, 239
Sciopticon, 242
screen for use with, 242
to avoid fracture of con-
denser, 241
239, 240
triple dissolver, 242
Whitefield's improvements,
wick trimmer, 242
Optics of photography, 36
Orthochromatic photography, 132
Abney's method, 137
chemistry of, 24
Ives, 134
136
135
chlorophyll, suggested by
clearing solution for, 138
dyes used for, 135
Eder's method of, 136
Edward's opinion on, 135
formula for developing, 138
Ive's method of preparing,
Meldola's hypothesis, 137
Tailfer & Clayton's patent,
theory of, 137
use of yellow screen, 136
Vogel's experiments in, 133
Ortho-dioxybenzene, 278
Orthoscopic lens, 51
Oscillating tables or rockers, 242
Over-exposure, 338
Oxalate of iron, 262
peroxide of iron, 262
potash, 278
Oxalic acid, 274
Ox-gall, 275
Oxy-calcium light, 62
of spike, 271
of vitriol, 290
Opal glass, 131
collodio-chloride on, 132
formula for positives on, 131,
132
Optical or magic lantern, 238
dissolving views with, 238
electric light for, 241
Oxy-hydrogen light, 61
Oxyphenic acid, 278
Oyster-shell markings, 97
PALLADIUM, 275
Panoramic lens, Sutton's, 51
photography, 138
Pantascopic camera, 242
Paper, 275
as sensitiser, 23
INDEX.
361
Papyrotype, 159
Paraphenylene-diamine, 276
Pencil of Nature, 7
Periscopic lens, Goddard's, 52
Steinheil's, 50
Permanganate of potash, 278
Peroxide of hydrogen, 257
Phenylamine, 256
Photochromo-typography, 144
Photo-engraving, 140
early discovery of, 140
half-tone zinc etching, 143
Pretsch's method, 140
screen plate for, 143
Photo-filigrane, 144
Photo-galvanography, 144
Photogenic drawing, 140
Photography and colour, 146
150
Abney's spectrum, 150
Becquerel's experiments, 147
early experiments in, 146
Ives' heliochromatic prints,
Lippmann's spectrum, 152
Scott's method, 151
Sidebotham's
Photo-lithography, washing transfers,
158
Photo-meteorology, 305
Delépene's illustration of, 262
micrography, 159
Johnson's camera for, 161
Johnson's illustration, 160
methods of procedure, 159
Photometers, 243
Photophane, 98, 162
Photo-tint, 98, 162
Photo-typography, 162
illustration by swelled gelatine
process, 162
Pin-hole camera, 38
photography, 162
Pinholes, 339
Plate-boxes, 243
rack, 243
Platinotype process, 163
acid baths for, 167
Berkeley's formulæ of reac-
tion in, 165
chemistry of, 35
clearing solutions for, 167
cold process, 168
correct exposure for paper,
development, 166
photograph,
148
Vallot's method and for-
166
mula, 149
Vogel's opinion on, 149
Woodbury's method, 150
its value to artists, 16
formulæ for, 165, 170, 171
Herschel's experiments with
Langton's moon, 145
on wood, 145
Photogravure, 140
Goupil's method, 141
Klic's process, 142
Photo-lithography, 152
154
157
advantages of, 159
albumen coating for paper, 156
clearing solution, 155
coating prints with ink, 157
formula for blacking negatives,
ink for, 157
kind of negatives for, 153
paper prepared with arrowroot,
photo-zincography, 153
printing transfers, 157
sensitising solution, 156
suitable drawings for, 153
transfer paper for, 155
transferring to stone, 158
platinum, 164
165
mountants for prints, 167
paper to be kept dry, 166
permanence of prints, 172
Pizzighelli's process, 170
two methods, hot and cold,
Willis's process, 164
Platinum, 276
Plumbago process, 172
formulæ for, 173
Pneumatic plate-holder, 243
Poisons, 272
Portrait lenses, 53
Portraiture, 305
backgrounds, 307
large heads, 308
Positive-printing process, 25
Positives, 340
Potassium bromide, 277
as restrainer, 30
carbonate, 277
chloride, 277
352
INDEX.
Potassium chloroplatinite, 277
cyanide, 277
cyanide in fixing, 31
dichromate, 277
ferricyanide, 277
ferrocyanide, 277
iodide, 278
in solarisation, 26
oxalate, 278
permanganate, 278
salts in developing, 20
in intensifying, 32
sulphide, 278
Pouncey's carbon process, 83
Practical hints, 321
Preservatives, 23
Primuline process, 35, 173
of, 175
J. T. Taylor's modification
Printing, chemistry of, 33
for opals, 244
frames, 244
on ivory, 183
and toning 175
blisters on paper, remedies
for, 179, 180
182
Carey Lea's remarks on, 181
fixing solution, 179
fuming albumenised paper,
method of printing, 176
necessity for using fresh
"hypo," 181
182
cess, 183
printing on drawing paper,
printing on plain paper, 182
quality of negative for, 179
stability of prints, 177, 180
Sutton's serum of milk pro-
to clean dishes for, 180.
to recover silver, 180
to sensitise paper, 176
toning solutions, 177, 178
Processes, 67
Proof spirit, 273
Proto-sulphate of iron, 262
Prussian blue in printing, 34
Pseudo-solarisation, 26
Pyrocatechin, 278
Pyrogallol or pyrogallic acid, 279
first use of, 279
manufacture of, 279
Pyroxylin or gun-cotton, 279
Pyroxylin, nitre process, 280
preparation of, 280
process with mixed acids, 280
QUICKSILVER or mercury, 273
Quinol, 267, 281
RAPIDITY of lenses, 41
of shutters, measuring, 235, 236
Reade, Rev. J. B., negatives on paper,
14
Ready sensitised paper, 281
Ashman's formula for, 281
Burton's, 282
Rectilinear lenses, 52
Red chromate of potash, 277
prussiate of potash, 277
Reducing and clearing solutions, 88
Reduction of density, 340
Reflected light, 341
Refraction, index of, 38
Rembrandt portraits, 309
Reproduced negatives, 183
Residues, 341
Restrainers, chemistry of, 29, 30
Retouching, 187
desk, 245
pencils, 188
Reversal of image, 25, 184
Brook's method, 185
experiments by Mr. A. P.
Okell, 184
experiments by Colonel
Waterhouse, 184
formulæ for, 184, 185
solarisation effects, 185
Reversed negatives, 185
by prism, 185
by silvered mirror, 186
by stripping, 186
through the glass, 186
Ripening of emulsion, 21
Rockers or oscillating tables, 242
Rodinal, 282
Roller slide, 245
Rolling machines, 210
Rosolic acid (or aurin), 257
Ruby medium, 189
SAL ammoniac, 255
volatile, 255
Sandarac, gum, 282
Saturated solution, 343
Sciopticon, 242
INDEX.
363
+
Screen-plates (Wolfe's), 189
Sel d'or or hyposulphite of gold, 265
Sensitisers, theory of, 20, 22
Sesquicarbonate of ammonia, 255
Shellac or gum lac, 282
Silver, 283
bromide, 283
ripening of, 22
chloride, 283
haloids, action of light on, 21
iodide, 283
as sensitiser, 23
nitrate, 284
oxide, 284
plates used by Daguerre, 2
action of iodine vapour and
mercury on, 2
salts, use of, by Davy and Wedg-
wood, I
<<
sulphide, 284
Silvering glass, 189
Mr. Common's method, 190
Single achromatic lens, 50
Size of drops, 345
Sky-shade, 245
Sodium acetate, 284
biborate or borax, 257
carbonate, 284
chloride, 284
nitrate, 284
oxalate, 285
silicate or water-glass, 285
sulphite, 285
thiosulphate, 285
accelerator, 30
in fixing, 31, 34
Solar camera, 245
Solarisation, 185
Stereoscope, cameras for, 316, 317
Chapman's printing - frames for
transparencies, 320
Dancer's method of taking pic-
tures, 314
discussion as to invention of, 314
diagrams for, 311
method of mounting prints, 317
size of plates, 316
Wheatstone's, 311
Stoppers, 246
Stops and diaphragms, 227
uses of, 41, 49
Stripping films from glass, 186
Strontium chloride, 290
Studios or glass rooms, 346
Houghton's lawn, 347
Sulphate of iron, 262
Sulphocyanide of ammonia, 256
Sulphuret of ammonia, 256
Sulphuric acid, 290
Swing-back camera, 55
Symbols, 347
Symmetrical lenses, 52
TABLE of solubility, 344
Talbot, H. Fox, account of his dis-
coveries, 7
discovery of latent image, 14
etched silver plates, 15
experiments with iodine on silver
leaf, 12
fixing with iodide of potassium, II
pencil of Nature, 7
produces images of lace, 10
use of silver chloride, 10
silver iodide, II
Talbotype, So
"hypo" used by Daguerre, 2
chemistry of, 25
Specific gravity, 345
Spectroscope, the, in photography, 309
Spectrum, the, 39
Spirits of hartshorn, 254
of wine, 253
Squeegee, 246
Stains, to remove, 190
Stannotype, 191
Starch, 290
Steel-facing copper plates, 192
Stenochromy, 193
Stereoscope, the, 310
Breeze's tranparencies, 318
Brewster's, 311, 312
Tannic acid, 290
Tannin process, 193
Taupenot process, 193
formulæ for, 194
Tea process, 194
Telescopic photography, 194
195
Dallmeyer's instrument for,
use of opera-glass by J. T.
Taylor, 195
Tents, 247
Test-paper, 291
Thermometers, 197
Toning and printing, 175
chemistry of, 33
Transferotype, 197
364
INDEX.
Trays and dishes, 229
Trihydroxybenzene, 279
Triplet lenses, 53
Tripods and camera stands, 226
Turnbull's blue in printing, 34
Turpentine, 291
Typogravure, 197
URANIUM, 291
nitrate, 291
printing, 198
toning with, 199
Wothlytype, 199
Uranyl nitrate, 291
VARNISH, 291
Waxed-paper process, 200
Weights and measures, 348
352
conversion of French into English,
English, 353
French, 353
French fluid measure, 351
metric system, 350
Woodbury-gravure, 201
Woodbury-type, 15, 200
Swan's process, 200
description of, by Woodbury, 200
Wothlytype, 199
Writing titles, 202
YELLOW negatives, 200
black, 292
View, angle of, 41
finders, 248
249
Claude Lorraine mirror,
lens, Ross, 50
Vignetting, 199
WASHING apparatus, 249
Water, 292
Water-glass or sodium silicate, 285
Wave-length of light rays, 36
Wax, 293
prussiate of potash, 277
ZINC, 293
"clean etching," 204
etching, 202
etching-bath for, 203
Zinc-etching, formula for sensitising
plate, 202
printing-frame for, 203
to develop plate, 203
to gum the plate, 203
to protect plate with varnish, 203
transfers for, 202
THE END.
BALLANTYNE PRESS
PRINTED BY BALLANTYNE, HANSON AND co.
EDINBURGH AND LONDON.
Griffin's Recent Introductions.

THE
"Garrick" Perfected Camera
Has every desirable Movement.
-plate size.
Weighs but 42 ounces.
Measures, when closed,
8 × 8 × 2 inches.
Of excellent Workmanship.
Altogether it is a Model Field
AIRPHINALA
Camera.
Camera, with 3 Double Slides
PRICE LIST.
6×4
74×5
8 × 61
X
10 x 8
£S S 0
£9 10 0 £10 10 0 £13 10 0
250
2 15 0
3 10 0
500
1 5 0
1 5 0
1 10 0
1 10 0
Rapid Rectilinear Lens, with Iris
Diaphragm
Tripod Stand, 3-Fold
£11 18 0 £13 10 0 £15 10 0 £20 0 0
The "Griffin" Magazine Hand Camera. Improved form, with Sunk
Identical View-Finder, Time and Instantaneous Shutter, and good R. R. Lens.
£5, 10s.
ADVANTAGES.
1. Can be recharged in broad daylight.
2. Plates of different rapidities can be used.
3. Any desired plate can be exposed.
4. No sheaths or backing.
5. Focussing adjustment.
6. Quite simple in working.
7. No complications.
8. Weight under 4 lbs.
Griffin's "Rex" Complete Set. An efficient Outfit at a moderate price.
Comprising -Plate Camera, Lens, Shutter, Dark Slide, and Stand. £6, 6s.
Griffin's "Climax" Dry Plates are the nearest approach to the vigour
and tone of the old Collodion Plate yet obtained. Write for Samples.
WRITE FOR PRICE LIST.
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PHOTO-SUPPLY (J
DEPARTMENT:
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DANIELSSON & CO.
52 BEAUMONT STREET,
PORTLAND PLACE,
LONDON, W.
DANIELSSON & CO. have made it their Specialité to
prepare all kinds of Illustrations for Scientific, par-
ticularly Medical, Works.
ORIGINAL DRAWINGS
Made from Life, Pathological Specimens, and from the
Microscope.
LANTERN SLIDES
Prepared from any kind of original.
SPECIMENS
Of MESSRS. DANIELSSON'S work will be found in the
"Transactions" of the Royal Medical and Chirurgical
Society, Pathological Society, Clinical Society, Ophthal-
mological Society, and in many other high-class Medical
Works.
** For collotype reproduction of microscopic
*
sections, see page 162 of this book.
DANIELSSON & CO.
52 BEAUMONT STREET,
PORTLAND PLACE,
LONDON, W.
THE
TYPOGRAPHIC ETCHING COMPANY.
ALFRED & CHARLES DAWSON
Beg to direct the attention of Artists, Authors, Publishers,
and Printers to their various and unique Processes for the pro-
duction of Surface-Printing Blocks and Intaglio Copperplates,
by special methods practised only by them, and yielding
results superior to any of the ordinary zinc processes.
Their No. 1, or TYPOGRAPHIC ETCHING PROCESS,
From the facilities it presents for employing type in an ingenious manner for lettering, is
unrivalled for the production of Maps, Plans, and Diagrams; while for Landscapes, Archi-
tecture, and general Illustrations, effects can be produced which vie with the most elaborate
and artistic wood engraving.
Their No. 2, or PHOTO-RELIEF PROCESS,
Is most specially suited for the reproduction on any scale, either enlarged or reduced, of Wood,
Copper, and Steel Engravings; Pen-and-Ink, and especially Pencil and Crayon, Drawings;
Impressions from Type, &c., for Letterpress Printing, in all of which results can be shown
which are not to be equalled by any other Photo-relief Process.
As specimens, please see the Engravings in "The Graphic," "The Illustrated Catalogue of the
Royal Society of Painters in Water Colours," English Illustrated Magazine," and all the highest
class Technical and Educational Publications.
Their No. 3, or PHOTO-GRAVURE PROCESS,
Is adapted for the reproduction of Copper Plates from all kinds of Line and Mezzotint Engrav-
ings, Drawings in Line or Washes, Oil Paintings, Nature or Objects, or, in fact, anything from
which a photographic negative can be obtained. See "The Portfolio," "The Late Duke of
Clarence's Indian Tour,' The Laureate's Country," &c.
"}
The T. E. CO. are the ONLY FIRM in this Country who work these Letter-
press and Copperplate Processes, which are applicable to high-class Book
Illustrations, and which are extensively used by the leading Publishers, and also
by the Trustees of the British Museum, and many of the Learned Societies.
Estimates and Specimens of any of the Processes will be sent on application to the Office,
stating information as to Requirements.
SPECIAL PHOTOGRAPHY AND ELECTROTYPING UNDERTAKEN AT MODERATE CHARGES.
THE
Typographic Etching Company,
AUTOMATIC, PHOTOGRAPHIC, AND GENERAL
ENGRAVERS,
3 LUDGATE CIRCUS BUILDINGS, LONDON, E.C.
Registered Telegraphic Address—“Engravers, London.”
Engraving Departments - Hogarth Works, Chiswick, Middlesex.

WEST, NEWMAN, & CO.
PHOTO-LITHOGRAPHERS,
CHROMO-LITHOGRAPHERS, ENGRAVERS,
LETTERPRESS PRINTERS,
54 HATTON GARDEN, LONDON.
WEST, NEWMAN, & CO. especially undertake the
printing of works on Science and the Plates which
illustrate them. Specimens of their work may be seen in
the "Transactions" of the Royal Society, the Zoological
Society, the Linnean Society, the New Sydenham Society,
the Obstetrical Society, the Pathological Society, and
many other Learned and Medical Societies, as well as
in Scientific Books, not only in this country, but in
India, South Africa, New Zealand, and various other
parts of the world.
WEST, NEWMAN, & CO. are at all times ready to
advise with Authors and Artists as to the best or
cheapest means of printing their work, and to give
estimates of cost. See specimen of their Photo-Litho-
graphic Illustration at page 152 of this book.
WEST, NEWMAN, & CO. K
54 HATTON GARDEN, LONDON.

Opticians to
the Queen.
HORNE, THORNTHWAITE, & WOOD,
MANUFACTURERS OF
PHOTOGRAPHIC APPARATUS, PLATES, AND CHEMICALS.
WOOD'S BEST QUALITY CAMERA.-Double Extension, Turntable,
4-fold Stand, and Three Double Backs.
1. -plate, £8, 8s.; 1-plate, £10, 10s.
WOOD'S ENGLISH LENSES for Landscapes, Portraits, or Architec-
ture. Carefully Corrected, Centred, and Mounted.
Rapid Rectilinear.
Wide Angle.
41 by 31
6 5/5/5
Focus.
5 in.
Water Diaphi.
Iris Diaph.
Focus.
£2 15
0
£3 5 0
3 in.
£3 0
0
7 in.
3 10 0
4
4
0
4 in.
4
0
*
7)
85/1 6
11 in.
5 5 0
6
6
0
5 in.
5
0
0 0
COMPLETE SETS OF APPARATUS, including Best Camera, English
Rapid Rectilinear Lens, 4-fold Stand, Leather Case, and Materials,
&c., all of the best quality.
-plate, £14, 10s.; -plate, £18, 10s.; 1-plate, £28, 10s.
WOOD'S "TRAFALGAR" PLATES.-The best Plate for Amateurs.
Three Rapidities. "Landscape." -plate, 1s.; -plate, 2s. 3d.
WOOD'S CELLULOID FILMS.-1-plate, 1s. 6d. ; -plate, 3s. 8d.;
1-plate, 6s. 6d.; 10 x 8, 10s.
WOOD'S LANTERN PLATES (Chloride).-Per dozen, 1s.
WOOD'S HYDROKINONE DEVELOPER.-The finest Developer for
Celluloid Films, Bromide Papers, Ordinary Plates, and Chloride
Plates. Eight ounces (concentrated) in two solutions, in Case, 2s.
ACKLAND'S EXPOSURE SCALE.-For use with Stanley's Actino-
meter. Indicates the correct exposure for a plate without calcula-
tion, 3s. 6d.
((
A PHOTOGRAPH, AND HOW TO TAKE IT,"
With CATALOGUE Gratis. Post Free, One Stamp.
416 STRAND, and 74 CHEAPSIDE, LONDON.
2 A
JOSIAH T. CHAPMAN,
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value to the Amateur or
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*
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AND USEFUL PAMPHLETS
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ROSS
CELEBRATED PORTRAIT AND VIEW
LENSES.
(Over Fifty Thousand of these Lenses have been Sold.)
MANY RECENT IMPORTANT IMPROVEMENTS, SEVERAL NEW SERIES.

ROSS' PATENT CONCENTRIC LENSES. F 22.
For Architecture, Copying, Landscapes, &c. The greatest advance ever
made in Photographic Lenses. Send for Press reports.
ROSS' PORTABLE SYMMETRICALS. F 16.
Very popular for Landscapes, Architecture, and Copying. The first ten
of the series screw into sanie flange.
ROSS' WIDE ANGLE SYMMETRICALS, F 16.
Embracing an angle of 90 degrees and upwards.
Interiors and Confined Situations.
ROSS' RAPID SYMMETRICALS (NEW). F 8,
Very suitable for
For Groups, Views, Copying, Enlarging, &c. The Most Useful all-round
Lens for Out-door Work.
ROSS' UNIVERSAL SYMMETRICALS. F 5,657.
A New Extra Rapid series for Portraits, Groups, and Instantaneous Work.
Highly recommended.
ROSS' SINGLE LANDSCAPE LENSES. F 16,
Introduced to meet the demand for a cheap series for purely Landscape
Work.
ROSS' PORTRAIT AND CABINET LENSES. F 4.
Used by Leading Professional Photographers everywhere. Great brilliancy
and exquisite defining power.
ROSS' HAND CAMERA LENSES. F 5,6. and F 8,
Bronzed Mounts, Iris or Waterhouse Diaphragms. Can be supplied in
pairs, when so required.
ROSS' DIVIDED HAND CAMERA.
Has met with great success, Thoroughly reliable. Highly recommended
by numerous purchasers.
ZEISS PATENT ANASTIGMATIC LENSES.
Manufactured by Ross & Co, in Three Series, for Portraits, Groups,
Architecture, Copying, &c.
ROSS STUDIO AND FIELD CAMERAS, &c. &c.
ROSS & CO.,
Manufacturing Opticians,
112 New Bond Street, LONDON, ENGLAND.
M. WOLFE'S
PERFECT LINED SCREEN PLATES
FOR
HALF-TONE ENGRAVING,
ADAPTED TO ALL
WASHOUT SWELLED GELATINE
AND
ZINC ETCHING PROCESSES.
RULED ABSOLUTELY PERFECT.
In these days of low prices and sharp competition, it is neces-
sary to cater for the Commercial trade, and by the turning out
of good work you will receive satisfactory results. Cuts of Views,
Machinery, &c., &c., for Book Illustrations, can be made by the
above Screens, to be surpassed by no others.
FULL INSTRUCTIONS IN HALF-TONE ETCHING, $40.
INVESTIGATE THIS:-
8 × 10 Plates, each
10 × 12
""
13 × 13
>>
14 × 14
""
وو
$20
30
50
•
70
My Plates are in use by the finest Etchers in the States. For
full particulars and samples of work send 6d. for postage to
M.
WOLFE,
106 SOUTH MAIN STREET,
DAYTON, O.
THE
WOODBURY PERMANENT PHOTOGRAPHIC
PRINTING COMPANY,
EYRE & SPOTTISWOODE, PROPRIETORS,
BEG
EG to call the attention of Publishers to the advantages of the
Woodbury-Gravure process for the purpose of High-
class Book Illustrations, it being a process which reproduces with
equal facility copies of wash or line drawings, portraits from life,
landscapes, photographs, paintings, engravings, and sketches of all
kinds. Woodbury-Gravure approaches nearest to photo-
engraving in results, but without the initial expense of preparing
the plate.
The WOODBURY COMPANY are also the original holders of the
patent for Woodbury type printing, and which they have most
successfully worked for many years, the results produced being far
superior to any other mechanical process for the reproduction for
either Book Illustrations, Trade Catalogues, &c., &c., where mount-
ing is not an objection.
Examples of both the above-mentioned processes will be
found in this Publication.
The WOODBURY COMPANY also undertake
Collotype Printing .
for Book Illustrations.
Carbon Printing
for Publication Purposes.
Silver Printing
of the Best Description.
·
Platinotype Printing. for all Requirements.
Carbon Enlargements on the Company's own special make of Tissue
Carbon Tissue
from Amateur or Professional negatives.
in Cut Pieces for small Consumers.
PRICE LISTS and all Information on application to
6 GREAT NEW STREET,
LONDON, E.C.
WORKS-CASTLE BAR, EALING, W.
The firm have sent us some magnificent specimens of their half-tone blocks. One we may
mention in particular, which appeared in the Illustrated London News, “Grouse upon the Moors,"
reproduced from a drawing in black and white, which is one of the most perfect photo-engraved
blocks that has ever been made in this country. Messrs. MEISENBACH have succeeded admirably
in their attempt to give these blocks all that brightness and delicacy that are so much admired
in the American and Continental work. It is, indeed, doubtful if any country whatever, in
spite of fine climatic influences, can surpass some of the work we have seen done at the Norwood
studio."—British and Colonial Printer and Stationer.
"Many improvements which have recently been introduced have brought their process to
the highest point of perfection."--Photographic News.
MEISENBACH
IMPROVED PROCESS
OF
PHOTO-ENGRAVING,
For the illustration of Fine Art and Scientific Publications, Books of Travel,
Pictorial Guides, Catalogues, Art Magazines, Newspapers, &c., the MEISEN-
BACH PROCESS is unequalled, and is the most perfect Photo-Engraving method in use.
These Illustrations can be reproduced from
OIL PAINTINGS, WATER COLOURS, PHOTOGRAPHS,
SKETCHES IN WASH, CHALK, CRAYON, LEAD PENCIL.
or, in fact, anything from which a negative can be made.
PRICES AND VARIETIES OF TINT OR GRAIN USED.
Open Grain Blocks, 1/3 per square inch; minimum, 15/- net.
Medium Square Blocks, 1/4
77
Fine Grain Blocks, 1/6
""
POSTAGE ADDITIONAL.
15/-
17
T
15/-
""
Terms-Cush, with Order, or London Reference and net Monthly Settlements.
Special Price for a series or for a large number of subjects, depending on nature of copy,
size, and number of blocks.
The Open Grain is especially suitable for Newspapers and other work printed at a high
speed with inferior ink and paper.
The Medium Grain is, as the name implies, an intermediate tint between the Fine and
Open Grain, and is generally used for the illustration of such Publications as are printed with
medium quality ink and paper.
The Fine Grain is recommended for high-class Art Reproductions, and best results are
obtained with well-rolled soft-sized dry paper, hard packing, and good ink.
N.B.-Points to Remember.-In sending instructions, special care should be taken to
state clearly the grain to be used, and the required size of block in inches one way; also state
whether the whole or only a portion of the picture has to be engraved. Unmounted photographs
should always be sent flat between cardboards or in roller, as creases and marks are difficult to
keep out of the reproduction.
Abridged Particulars and Specimens post free.
Art Specimens engraved from paintings and printed in tinted colour, sent free on
receipt of 41d. for postage.
The facilities of the MEISENBACH COMPANY for the production of engraved plates surpass any
establishment in Great Britain.
THE MEISENBACH COMPANY, Limited,
WOLFINGTON ROAD, WEST NORWOOD,
LONDON, S.E.
Chief Offices and Works-WEST NORWOOD.]
[City Office-188 FLEET STREET, E. C.
GOLD MEDAL, INTERNATIONAL INVENTIONS EXHIBITION.
SILVER AND BRONZE MEDals, Leeds EXHIBITION.

WATERLOW & SONS,
LIMITED,
Photographic Art Printers and Engravers,
FINSBURY WORKS, LONDON, E.C.
Photo-Zincography.
Photo-Lithography.
Photo-Mechanical Printing.
Collotype.—Hand and Machine Printing for Art Publications, Scientific and Anti-
quarian Periodicals, Machinery, Landscapes, Portraits, Pottery, Furniture
Designs, Trade Advertisements, &c. The superior results given by this pro-
cess, and the rapidity and cheapness by which the prints are produced,
together with the advantage of printing with or without margins, place it in
the first rank of processes for commercial purposes.
MESSRS. WATERLOW & SONS, LIMITED, have given
this branch of the Photo-Printing Department special facilities for the
production of good work, and have introduced the most perfect machinery
and plant obtainable.
Woodbury Prints.-High-class permanent copies, equal in appearance to the best
Silver Prints, of Portraits, Landscapes, Furniture, Pottery, &c.
Prints may
be obtained in almost any colour from Customers' own Negatives, or from the
original objects. These reproductions are specially suitable for Portrait work,
and are valuable for every description of Artistic or Commercial Illustrations.
Photo-Zinco Engraving.-Blocks for Surface Printing, from Line and Grained-
paper Drawings, Steel and Copper Plates, Wood Engravings, &c., &c. Letter-
press Blocks in "Half-tint" (stipple or dot) direct from Photographs from
Nature, without drawing.
Accurately registered Blocks for Chromographie Printing.
Engraving in Line and Half-tone on Copper and Zinc.
Intaglio
The greatest care and skill is employed in the production of these Blocks,
and the results are the finest which it is possible to obtain.
The new and extensive Photographic Works, being fitted with Modern
Appliances, Machinery, Electric Lighting, &c., rapid and accurate work is
always obtainable, irrespective of weather or season.
PRICE LISTS, ESTIMATES, and full particulars on application.
WATERLOW & SONS, Limited, Finsbury Works, E.C.
HINDU
EST!
1848
J.C.NORBURY & SONS
CHROMO LITHOGRAPHERS
DESIGNERS OF TRADE MARKS
108 PORTLAND ST MANCHESTER
in every description of CHROMO & EMBOSSED STYLES.
ickets SPECIALITE.-Indian, Chinese & Japanese Native
Stamps.
Subjects.
White & Grey Goods Stamps in the ordinary and by
the New "Norbrotype Process.
staff of Artists employed to originate subjects suitable for
every description of Tickets and Stamps.
CHINESES
The Manchester Trade Marks Association,
108 PORTLAND STREET, MANCHESTER.
TRADE MARKS Originated, Registered, Assigned, and Transferred.
PROTECTION OF TRADE MARKS. On specified Terms the Association
undertakes to maintain a Scrutiny on all New Marks advertised by the Comp-
troller, and inform Clients as to Infringements on their deposited Marks.

F. J. NORBURY, MANAGER.
PURE
CHEMICALS.
HINTON & CO
38 BEDFORD STREET
STRAND, W.C.

HMERENNETT
Pharmaceutical and Photographic Chemists.
CHEMICALS
FOR
APPARATUS.
SERVICEABLE
THE ARTS, SCIENCES, TRADES, AND MANUFACTURES,
WHOLESALE AND RETAIL.
Solutions, Papers, Plates, and Apparatus for Photography
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A
CATALOGUE
OF

STANDARD WORKS
PUBLISHED BY
CHARLES GRIFFIN & COMPANY.
PAGE
I.-Religious Works,
4
II.-Works on Medicine and the Allied Sciences,
9
III.-General Scientific and Technical Works,
21
IV. Educational Works,
49
V.-Works in General Literature,
58
LONDON:
12 EXETER STREET, STRAND.
INDEX TO AUTHORS.
AITKEN (Sir W., M.D.), Science and Practice
of Medicine,
Outlines,
·
ANDERSON (M'Call) on Skin Diseases,
ANGLIN (S.), Design of Structures,
BELL (R.), Golden Leaves,
BERINGER (J. J. and C.), Assaying,
PAGE
9
9
•
14
21
•
58
22
10
ΙΟ
•
PAGH
JAKSCH (v.) and CAGNEY, Clinical Diagnosis, 14
JAMES (W. P.), From Source to Sea,
53
JAMIESON (A.), Manual of the Steam Engine 32
Steam and the Steam Engine - Elementary, 32
Applied Mechanics,
Magnetism and Electricity,
JEVONS (F. B.), A History of Greek Literature, 54
Athenian Democracy,
KEBLE'S Christian Year,
33
33
54
•
4
22
·
23
23
23
23
LANDIS (Dr.), Management of Labour,.
LANDOIS and STIRLING'S Physiology,
LEWIS (W. B.), Mental Diseases,
LINN (Dr.), On the Teeth,
18
•
•
13
•
15
•
19
•
19
50
•
13
BLYTH (A. W.), Hygiene and Public Health,
Foods and Poisons,
•
BROTHERS (A), Photography,
BROUGH (B. H.), Mine-Surveying,
BROWNE (W. R.), Student's Mechanics,
Foundations of Mechanics,
Fuel and Water,
BUNYAN'S Pilgrim's Progress (Mason),
BRYCE (A. H.), Works of Virgil,
BURNET (Dr.), Foods and Dietaries,
4
ΙΙ
CAIRD and CATHCART, Surgical Handbook, 12
CHEEVER'S (Dr.), Religious Anecdotes,
COBBETT (Wm.), Advice to Young Men,
Cottage Economy,
English Grammar,
French do.,
•
Legacy to Labourers,
Do. Parsons,.
COBBIN'S Mangnall's Questions,
COLE (Prof.), Practical Geology,
COLERIDGE on Method,
CRAIK (G.), History of English Literature,
Manual of
do.,
CRIMP (W. S.), Sewage Disposal Works,
CROOM (Halliday), Gynecology,
•
LONGMORE (Prof.), Sanitary Contrasts,
MACALISTER (Prof.), Human Anatomy,
MACKEY (A. G.), Lexicon of Freemasonry, 61
MAYHEW (H.), London Labour,
M'BURNEY (Dr.), Ovid's Metamorphoses,
MEYER AND FERGUS' Ophthalmology,
MILLER (W. G.), Philosophy of Law,
M'MILLAN (W. G.), Electro-Metallurgy,
MUNRO (R. D.), Steam Boilers,
JAMIESON'S Electrical
NYSTROM'S Pocket-Book for Engineers,
•
•
бл
•
55
14
•
55
34
33
•
35
35
•
15
•
15
19
OBERSTEINER and HILL, Central Nervous
Organs,
4
58
58
50
50
MUNRO and
59
59
Pocket-Book,
50
•
24
•
50
•
5I
PAGE (H.W.), Railway Injuries,
•
51
•
25
16
6
52
52
•
50
CRUDEN'S CONCORDANCE, by Eadie,
CRUTTWELL'S History of Roman Literature,
Specimens of
do.,
Early Christian Literature,
CURRIE (J.), Works of Horace,
DAVIS (J. R. A.), An Introduction to Biology, 26
The Flowering Plant,
Zoological Pocket-Book,
DICK (Dr.), Celestial Scenery,
DOERING and GRÆME'S Hellas,
D'ORSEY (A. J.), Spelling by Dictation,
DUCKWORTH (Sir D., M.D.), Gout,
DUPRE & HAKE, Manual of Chemistry,
EADIE (Rev. Dr.), Biblical Cyclopædia,
Cruden's Concordance,
Classified Bible,
•
Ecclesiastical Cyclopedia,
Dictionary of the Bible,
•
PARKER (Prof.). Mammalian Descent,
•
пи
PHILLIPS and BAUERMAN, Metallurgy,. 38
POE (Edgar), Poetical Works of,
60
PORTER (Surg.-Maj.), Surgeon's Pocket-Book, 19
RAMSAY (Prof.), Roman Antiquities,
Do.
Latin Prosody,
Do. Elementary,
Elementary,
55
•
55
•
55
55
•
RANKINE'S ENGINEERING WORKS, 39, 40
REED (Sir E. J.), Stability of Ships,
Antiquities of the Aryan Peoples,
SCHWACKHÖFER and BROWNE, Fuel
•
45
36
26
•
4I
27
ROBERTS-AUSTEN (Prof.), Metallurgy
•
42
4
ROBINSON (Prof.), Hydraulics,
·
43
53
•
53
SANSOM (A. E.), Diseases of the Heart,
SCHRADER and JEVONS, The Prehistoric
16
14
•
56
27
6
and Water,
•
44
6
6
SEATON (A. E.), Marine Engineering,
SEELEY (Prof.), Physical Geology,
·
6
SENIOR (Prof.), Political Economy,
•
57
6
SEXTON (Prof.), Quantitative Analysis,
•
44
·
44
44
64
7
•
7
•
13
•
•
20
20
8
8
•
ELBORNE (W.), Pharmacy and Materia Medica, 12
EMERALD SERIES OF POETS,
ETHERIDGE (R.), Stratigraphical Geology,
EWART (Prof.), The Preservation of Fish,
FIDLER (T. Claxton), Bridge-Construction,
FLEMING (Prof.), Vocabulary of Philosophy,
FOSTER (Chas.), Story of the Bible,
FOSTER (C. Le N.), Ore and Stone Mining,
GARROD (Dr. A. É.), Rheumatism,
Qualitative Analysis,
SHELTON-BEY (W. V.), Mechanic's Guide,.
SOUTHGATE (H.), Many Thoughts of Many
Minds,
Suggestive Thoughts,
(Mrs.), Christian Life,
STIRLING (William), Human Physiology,
•
60
37
•
27
28
•
53
5
•
29
Outlines of Practical Physiology,
14
Outlines of Practical Histology,
GILMER (R.), Interest Tables,
59
TAIT (Rev. J.), Mind in Matter,
GRÆME (Elliott), Beethoven, .
59
Novel with Two Herces,
59
GRIFFIN'S ELECTRICAL PRICE-BOOK,
29
GRIFFIN (J. J.), Chemical Recreations,
29
GURDEN (R.), Traverse Tables,
29
GUTTMANN (O.), Rock Blasting,
29
HADDON (Prof), Embryology,
•
13
HORSLEY (Victor), The Nervous System,
18
·
HUGHES (H. W.), Coal-Mining,
•
29
HUMPHRY, Manual of Nursing,
18
•
THE MASSES: How shall we reach them?
THOMSON (Dr. Spencer), Domestic Medicine, 63
THOMSON'S Seasons,
•
57
•
15
46
THORBURN (Wm), Surgery of the Spine,
THORNTON (J. K.), Surgery of the Kidneys, 15
TRAILL (W.), Boilers, Land and Marine,
WHATELY (Archbishop), Logic, and Rhetoric, 57
WORDS AND WORKS OF OUR LORD,
WRIGHT (Alder), The Threshold of Science,. 47
YEAR-BOOK OF SCIENTIFIC SOCIETIES, 48
8
INDEX TO SUBJECTS.
PAGE
13
4
LITERATURE, English,
-Greek,
•
•
56
Roman,
54
LOGIC,
55
MACHINERY, Hydraulic,
56
--and Millwork,
22
MAGNETISM,
6
MAMMALIAN Descent,
•
6
MARINE Engineering,
6
MECHANICS, .
6
MEDICAL Series,
5
26
46
-Works,
MEDICINE, Science and Practice of,
-Domestic,
33
MENTAL, Diseases,
26
Science,
PAGE
• SI
•
54
52
57
•
43
•
39
32, 33
19
45
23, 33, 35, 39, 40, 44
13-16
9
9
63
15
55
38, 42
23
29
20
53
41
•
15
18
•
•
I5
21, 28
METALLURGY.
MINE-SURVEYING,
MINING, Coal,
MYTHOLOGY, Greek,
27
•
47
--Ore and Stone,
•
44
•
44
NAVAL Construction,
.
•
29
14
7,8
NERVOUS ORGANS, Central,
System,
NURSING, Medical and Surgical,
OBSTETRICS,
PALEONTOLOGY
PHILOSOPHY, Vocabulary of,
PHOTOGRAPHY,
•
PHYSICS, Experiments in,
PHYSIOLOGY, Human, .
6
PHARMACY,
63
53
64
7
II
49
•
29
32, 33, 35
33-4
13, 19
Practical,
POCKET-BOOK, Electrical,
Engineering,
-Surgical,
-Zoological,
POETS, Emerald Series of,
POISONS, Detection of,
POLITICAL ECONOMY,
POOR, Condition of the,
RAILWAY Injuries, .
RELIGIOUS Works,
39
45
35, 40
•
14
·
27
IO
RHETORIC,
II
RHEUMATISM,
61
•
•
ROCK-BLASTING,
44
ROOFS, Design of,
ANATOMY, Human,
ANECDOTES, Cyclopædia of,
ANTIQUITIES, Prehistoric,
-Greek,
Roman,
•
ARYAN PEOPLES,
ASSAYING,
BIBLE (The Holy), Classified,
-Concordance to,
-Cyclopædia of,
-Dictionary of,
-Story of,
BIOLOGY,
•
BOILERS, Marine and Land,
-Management of,
BOTANY,
BRAIN, The,
•
BRIDGE-CONSTRUCTION,
CHEMISTRY, Inorganic,
-Experiments in,
Qualitative Analysis,
Quantitative
-Recreations in,
CLINICAL Diagnosis,
DAILY Readings,
DICTIONARY of Anecdotes,
of the Holy Bible,
Ecclesiastical,
-of Medicine (Domestic),
-of Philosophical Terms,
-of Quotations,
-of
(Religious),
DIETARIES for the Sick,
EDUCATIONAL Works,
ELECTRICAL, Price-Book,
ELECTRICITY,
ELECTRO-METALLURGY,
EMBRYOLOGY,
ENGINEERING, Civil, .
-Marine,
-Useful Rules in,
EYE, Diseases of the,
FISH, Preservation of,
FOODS, Analysis of,
FOODS and Dietaries,
FREEMASONRY,
FUEL and Water,
GEOLOGY, Practical,
Physical
Stratigraphical,
GOUT,
GRAMMARS,
GYNECOLOGY,
HEART, Diseases of the,
HISTOLOGY,
HORACE, Works of,
HYDRAULIC Power,
HYGIENE and Public Health,
INTEREST Tables,
LABORATORY Handbooks-
Histology,
Pharmacy,
Physiology,
LATIN Prosody,
LAW, Philosophy of,
LITERATURE, General,
Early Christian,
•
•
18, 63
18
24, 36, 37
24, 3
12
53
•
•
22
•
47
13
20
35
•
35
12, 19
•
•
27
ба
ΤΟ
57
8, 61
24
36
•
37
14
SHIPS, Stability of,
•
50
16
SKIN, Diseases of the,
SCIENCE, Popular Introduction to,
SCIENTIFIC Societies, Papers read before,
SEWAGE Disposal Works,
•
Wave-forms, Propulsion, &c. (Rankine),
16
•
SPINAL Cord, .
20
STEAM-ENGINE,
50
STRUCTURES, Design of,
•
43
STUDENTS' Text-Books,
IO, 19
SURGERY, Civil,
•
15
4
•
57
·
14
29
•
21
47
48
25
4I
40
14
•
IS
32, 40
21
·
17, 31, 32, 49
12
•
19
59
20
--of Spinal Cord,
12
20
•
55
Military,
——of Kidneys,
SURVEYING,.
•
TEETH, Care of the,
THERMODYNAMICS, (Rankine),
55
TRAVERSE Tables,
•
58
VIRGIL, Works of,
4
ZOOLOGY,
•
15
15
23, 29
•
19
•
40
.
29
•
50
•
19, 27
CHARLES GRIFFIN & COMPANY'S
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FOODS AND DIETARIES:
A Manual of Clinical Dietetics.
BY
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In Dr. Burnet's "Foods and Dietaries," the rationale of the
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•
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The
HUMAN PHYSIOLOGY.
BY PROFESSOR LANDOIS OF GREIFSWALD
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CLINICAL DIAGNOSIS.
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•
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TRANSLATED BY ALEX. HILL, M.A., M.D.,
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፡፡
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15
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THE SURGERY OF THE KIDNEYS.
Being the Harveian Lectures, 1889.
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DISEASES OF THE HEART
(THE DIAGNOSIS OF).
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[Shortly.
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17
Griffin's Medical Students' Text-Books.
PAGE
Anatomy,
Biology,
Botany (Elementary),
Brain, The-
PROF. MACALISTER,
13
AINSWORTH DAVIS,
26
AINSWORTH DAVIS,
27
Central Nervous
Organs,
OBERSTEINER AND HILL,
15
Mental Diseases,
BEVAN LEWIS,
15
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Inorganic,
DUPRE AND HAKE,
27
Qualitative Analysis,
PROF. SEXTON,
44
Quantitative
PROF. SEXTON,
44
""
Electricity,.
PROF. JAMIESON,
33
Civil,
Military,
Zoology,
Embryology,
Eye, Diseases of the,
Foods, Analysis of,
Foods and Dietaries,
Gynecology,
Histology,
Medicine,
Nursing,
Obstetrics,
Pharmacy,
Physiology—
Human,
Practical,.
•
Poisons, Detection of,
Skin, Diseases of the,
Surgery-
HALLIDAY CROOM,
PROF. STIRLING,
SIR WM. AITKEN,
L. HUMPHRY,
WYNTER BLYTH,
PROF. Anderson,
CAIRD AND CATHCART,
PORTER-GODWIN,
SELENKA AND DAVIS,
PROF. HADDON,
13
MEYER AND FERGUS,
14
WYNTER BLYTH,
10
R. W. BURNET,
11
16
20
9
18
H. G. LANDIS,
18
•
W. ELBORNE,
12
LANDOIS AND STIRLING,
13
PROF. STIRLing,
20
10
14
•
12
19
27
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CHARLES GRIFFIN & CO.'S PUBLICATIONS.
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NURSING (A Manual of):
C
Medical and Surgical.
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*
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The volume proceeds from a MASTER in
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•
LONDON: EXETER STREET, STRAND.
:
SCIENTIFIC AND TECHNICAL WORKS.
21
GENERAL SCIENTIFIC WORKS
RELATING TO
CHEMISTRY (THEORETICAL AND APPLIED); ELECTRICAL
SCIENCE; ENGINEERING (CIVIL AND MECHANICAL);
GEOLOGY, &c.
THE DESIGN OF STRUCTURES:
A Practical Treatise on the Building of Bridges, Roofs, &c.
BY S. ANGLIN, C. E.,
Master of Engineering, Royal University of Ireland, late Whitworth Scholar, &c.
With very numerous Diagrams, Examples, and Tables.
Large Crown 8vo. Cloth, 16s.
The leading features in Mr. Anglin's carefully-planned "Design of Struc-
tures" may be briefly summarised as follows:-
1. It supplies the want, long felt among Students of Engineering and
Architecture, of a concise Text-book on Structures, requiring on the part of
the reader a knowledge of ELEMENTARY MATHEMATICS only.
2. The subject of GRAPHIC STATICS has only of recent years been generally
applied in this country to determine the Stresses on Framed Structures; and
in too many cases this is done without a knowledge of the principles upon
which the science is founded. In Mr. Anglin's work the system is explained
from FIRST PRINCIPLES and the Student will find in it a valuable aid in
determining the stresses on all irregularly-framed structures.
3. A large number of PRACTICAL EXAMPLES, such as occur in the every-day
experience of the Engineer, are given and carefully worked out, some being
solved both analytically and graphically, as a guide to the Student.
4. The chapters devoted to the practical side of the subject, the Strength of
Joints, Punching, Drilling, Rivetting, and other processes connected with the
manufacture of Bridges, Roofs, and Structural work generally, are the result
of MANY YEARS' EXPERIENCE in the bridge-yard; and the information given
on this branch of the subject will be found of great value to the practical
bridge-builder.
Students of Engineering will find this Text-Book INVALUABLE."-Architect.
"The author has certainly succeeded in producing a THOROUGHLY PRACTICAL Text-
Book."-Builder.
"We can unhesitatingly recommend this work not only to the Student, as the BEST
TEXT-BOOK on the subject, but also to the professional engineer as an EXCEEDINGLY
VALUABLE book of reference."-Mechanical World.
"This work can be CONFIDENTLY recommended to engineers. The author has wisely
chosen to use as little of the higher mathematics as possible, and has thus made his book of
After careful perusal, we have nothing but
praise for the work."-Nature.
REAL USE TO THE PRACTICAL ENGINEER.
LONDON: EXETER STREET, STRAND.
22
CHARLES GRIFFIN & CO.'S PUBLICATIONS.
With numerous Tables and Illustrations. Crown 8vo. Cloth, 10/6.
Second Edition; Revised.
ASSAYING (A Text-Book of):
For the use of Students, Mine Managers, Assayers, &c.
BY
C. BERINGER, F.I.C., F.C.S.,
Late Chief Assayer to the Rio Tinto Copper Company, London,
AND
J. J. BERINGER, F.I.C., F.C.S.,
Public Analyst for, and Lecturer to the Mining Association of, Cornwall.
General Contents.
PART I.-INTRODUCTORY; MANIPULATION: Sampling; Drying; Calculation of Re-
sults-Laboratory-books and Reports -- METHODS: Dry Gravimetric; Wet Gravimetric-
Volumetric Assays: Titrometric, Colorimetric, Gasometric-Weighing and Measuring—
Reagents-Formulæ, Equations, &c.-Specific Gravity.
PART II.-METALS: Detection and Assay of Silver, Gold, Platinum, Mercury, Copper,
Lead, Thallium, Bismuth, Antimony, Iron, Nickel, Cobalt, Zinc, Cadmium, Tin, Tungsten,
Titanium, Manganese, Chromium, &c.-Earths, Alkalies.
PART III.-NON-METALS: Oxygen and Oxides; The Halogens-Sulphur and Sul-
phates-Arsenic, Phosphorus, Nitrogen-Silicon, Carbon, Boron.
Appendix.—Various Tables useful to the Analyst.
"A REALLY MERITORIOUS WORK, that may be safely depended upon either for systematic
instruction or for reference."-Nature.
"Of the fitness of the authors for the task they have undertaken, there can be no ques-
tion.
Their book ADMIRABLY FULFILS ITS PURPOSE.
The results given of
an exhaustive series of experiments made by the authors, showing the effects of VARYING
CONDITIONS on the accuracy of the method employed, are of THE UTMOST IMPORTANCE.”—
Industries.
In Preparation. Large 8vo.
PHOTOGRAPHY (A Text-Book of):
Its History, Processes, Apparatus, and Materials. Comprising
Working Details of all the more important Methods.
By A. BROTHERS, F.R.A.S.
With Illustrations by many of the Processes described.
LONDON: EXETER STREET, STRAND.
SCIENTIFIC AND TECHNICAL WORKS.
MINE-SURVEYING (A Text-Book of):
For the use of Managers of Mines and Colleries, Students
at the Royal School of Mines, &c.
BY BENNETT H. BROUGH, F.G.S.,
Instructor of Mine-Surveying, Royal School of Mines.
23
With Diagrams.
THIRD EDITION.
Crown 8vo. Cloth, 7s. 6d.
GENERAL CONTENTS.
General Explanations-Measurement of Distances-Miner's Dial-Variation of
the Magnetic-Needle-Surveying with the Magnetic-Needle in presence of Iron-
Surveying with the Fixed Needle-German Dial-Theodolite-Traversing Under-
ground-Surface-Surveys with Theodolite-Plotting the Survey-Calculation of
Areas-Levelling-Connection of Underground- and Surface-Surveys-Measuring
Distances by Telescope-Setting-out-Mine-Surveying Problems-Mine Plans-
Applications of Magnetic-Needle in Mining-Appendices.
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or Mining Student will consider his technical library complete without it."—Nature.
Supplies a long-felt want."-Iron.
"A valuable accessory to Surveyors in every department of commercial enterprise."-
Colliery Guardian.
WORKS
BY WALTER R. BROWNE, M.A., M. INST. C.E.,
Late Fellow of Trinity College, Cambridge.
THE STUDENT'S MECHANICS:
An Introduction to the Study of Force and Motion.
With Diagrams. Crown 8vo. Cloth, 4s. 6d.
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FOUNDATIONS OF MECHANICS.
Papers reprinted from the Engineer. In Crown 8vo, Is.
FUEL AND WATER:
A Manual for Users of Steam and Water.
BY PROF. SCHWACKHÖFER AND W. R. BROWNE, M.A.
LONDON: EXETER STREET, STRAND.
(See p. 44).
24
CHARLES GRIFFIN & CO.'S PUBLICATIONS.
PRACTICAL
(AIDS
GEOLOGY
IN):
WITH A SECTION ON PALEONTOLOGY.
BY
GRENVILLE A. J. COLE,
COLE,
F. G. S.,
Professor of Geology in the Royal College of Science for Ireland.
With Numerous Illustrations and Tables.
Large Crown 8vo.
Cloth, ros. 6d.
THIS work is intended as a companion to any ordinary Text-book of Geology;
and will be of special service to those students who have made excursions into the
field, and who wish to determine their specimens for themselves.
A large section of the book has been devoted to rocks and to the ordinary
minerals of the earth's crust, since these will always present themselves to the
observer during any expedition or in any country.
The section on Blowpipe-work has been inserted as an aid to Travellers; while
the description of the hard parts of fossil invertebrates will probably assist those
readers who find it impossible to distinguish genera by means of mere names and
figures.
GENERAL CONTENTS.
PART I.-SAMPLING OF THE EARTH'S CRUST.
Observations in the field.
Collection and packing of specimens.
PART II.—EXAMINATION OF MINERALS.
Some physical characters of minerals.
Simple tests with wet reagents.
Examination of minerals with the blowpipe.
Simple and characteristic reactions.
Introductory.
Blowpipe-tests.
Quantitative flame reactions of the felspars
and their allies.
Examination of the optical properties of
minerals.
PART III.-EXAMINATION OF ROCKS.
Rock-structures easily distinguished.
Some physical characters of rocks.
Chemical examination of rocks.
Isolation of the constituents of rocks.
The petrological microscope and microscopic
preparations.
Introductory.
The more prominent characters to be ob-
served in minerals in rock-sections.
Characters of the chief rock-forming minerals
in the rock-mass and in thin sections.
Sedimentary rocks.
Igneous rocks.
Metamorphic rocks.
PART IV.-EXAMINATION OF FOSSILS.
Fossil generic types.-Rhizopoda; Spongiæ;
Hydrozoa; Actinozoa.
Polyzoa; Brachiopoda.
Lamellibranchiata.
Scaphopoda; Gastropoda; Pteropoda;
Cephalopoda.
Echinodermata; Vermes.
Anthropoda.
Suggested list of characteristic invertebrate
fossils.
"A more useful work for the practical geologist has not appeared in handy form.'
Scottish Geographical Magazine.
"This EXCELLENT MANUAL
will be A VERY GREAT HELP.
The section
•
FULL
on the Examination of Fossils is probably the BEST of its kind yet published.
of well-digested information from the newest sources and from personal research."-Annals
of Nat. History.
LONDON: EXETER STREET, STRAND.
SCIENTIFIC AND TECHNICAL WORKS.
sewage dISPOSAL WORKS:
A GUIDE TO THE CONSTRUCTION OF WORKS FOR
THE PREVENTION OF THE POLLUTION BY
SEWAGE OF RIVERS AND ESTUARIES.
BY
W. SANTO CRIMP, M.INST.C.E., F.G.S.,
Assistant-Engineer, London County Council.
With Tables, Illustrations in the Text, and 33 Lithographic Plates.
Medium 8vo. Handsome Cloth, 25s.
25
Introduction.
PART I.—INTRODUCTORY.
Details of River Pollutions and Recommenda-
tions of Various Commissions.
Hourly and Daily Flow of Sewage.
The Pail System as Affecting Sewage.
The Separation of Rain-water from the Sewage
Proper.
Settling Tanks.
Chemical Processes.
The Disposal of Sewage-sludge.
The Preparation of Land for Sewage Dis-
posal.
Table of Sewage Farm Management.
PART II. SEWAGE DISPOSAL WORKS IN OPERATION-THEIR
CONSTRUCTION, MAINTENANCE AND COST.
Illustrated by Plates showing the General Plan and Arrangement adopted
1. Doncaster Irrigation Farm.
in each District.
2. Beddington Irrigation Farm, Borough of
Croydon.
3. Bedford Sewage Farm Irrigation.
4. Dewsbury and Hitchin Intermittent Fil-
tration.
5. Merton, Croydon Rural Sanitary Autho-
rity.
6. Swanwick, Derbyshire.
7. The Ealing Sewage Works.
8. Chiswick.
9. Kingston-on-Thames, A. B. C. Process.
10. Salford Sewage Works.
II. Bradford, Precipitation.
12. New Malden, Chemical Treatment and
Small Filters.
13. Friern Barnet.
14. Acton, Ferozone and Polarite Process.
15. Ilford, Chadwell, and Dagenham Sewage
Disposal Works.
16. Coventry.
17. Wimbledon.
18. Birmingham.
19. Newhaven.
20. Portsmouth.
21. Sewage Precipitation Works, Dortmund
(Germany).
22. Treatment of Sewage by Electrolysis.
•
"All persons interested in Sanitary Science owe a debt of gratitude to Mr. Crimp.
His work will be especially useful to SANITARY AUTHORITIES and their advisers
gives plans and descriptions of MANY OF THE
with very valuable information as to
The carefully-prepared drawings per-
EMINENTLY PRACTICAL AND USEFUL
MOST IMPORTANT SEWAGE WORKS of England
the cost of construction and working of each.
mit of an easy comparison between the different systems."-Lancet.
·
•
·
"Probably the MOST COMPLETE AND BEST TREATISE on the subject which has appeared
in our language.
Will prove of the greatest use to all who have the problem of
Sewage Disposal to face.
The general construction, drawings, and type are all
excellent."-Edinburgh Medical Journal.
LONDON: EXETER STREET, STRAND.
26
CHARLES GRIFFIN & CO'S PUBLICATIONS.
WORKS
BY J. R. AINSWORTH DAVIS, B. A.,
PROFESSOR OF BIOLOGY, UNIVERSITY COLLEGE, ABERYSTWYTH
BIOLOGY (A Text-Book of):
Comprising Vegetable and Animal Morphology and Physiology.
Crown Svo, with 158 Illustrations. Cloth, 12s. 6d.
In Large
GENERAL CONTENTS.
PART I. VEGETABLE MORPHOLOGY AND PHYSIOLOGY.-Fungi-Algæ-The
Moss-The Fern-Gymnosperms-Angiosperms.
Comparative Vegetable Morphology and Physiology-Classification of Plants.
PART II. ANIMAL MORPHOLOGY AND PHYSIOLOGY.-Protozoa-Cœlenterata—
Vermes-Arthropoda-Mollusca-Amphibia-Aves-Mammalia.
Comparative Animal Morphology and Physiology-Classification of Animals.
With Bibliography, Exam.-Questions, complete Glossary, and 158 Illustrations.
As a general work of reference, Mr. Davis's manual will be HIGHLY SERVICEABLE to
medical men."-British Medical Journal.
"Furnishes a clear and comprehensive exposition of the subject in a systematic form."-
Saturday Review.
Literally PACKED with information."-Glasgow Medical Journal
THE FLOWERING PLANT,
AS ILLUSTRATING THE FIRST PRINCIPLES OF BOTANY.
Specially adapted for London Matriculation, S. Kensington, and University Loca?
Examinations in Botany. Large Crown 8vo, with numerous Illustrations.
*
•
3s. 6d.
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The SCIENTIFIC ACCURACY of statement,
and the concise exposition of FIRST PRINCIPLES make it valuable for educational purposes.
the chapter on the Physiology of Flowers, an admirable résumé is given, drawn from Darwin,
Hermann Müller, Kerner, and Lubbock, of what is known of the Fertilization of Flowers."--
Journal of the Linnean Society.
'We are much pleased with this volume
•
In
the author's style is MOST CLEAR, and
The Illustrations are very good,
his treatment that of a PRACTISED INSTRUCTOR.
suitable and helpful. The Appendix on Practical Work will be INVALUABLE to the private
student.
We heartily commend the work."-Schoolmaster.
* Recommended by the National Home-Reading Union; and also for use in the
University Correspondence Classes.
LONDON: EXETER STREET, STRAND.
SCIENTIFIC AND TECHNICAL WORKS.
PROF. DAVIS'S WORKS-Continued.
27
A ZOOLOGICAL POCKET-BOOK;
Or, Synopsis of Animal Classification.
Comprising Definitions of the Phyla, Classes, and Orders, with explanatory
Remarks and Tables.
BY DR. EMIL SELENKA,
Professor in the University of Erlangen.
Authorised English translation from the Third German Edition. In Small
Post 8vo, Interleaved for the use of Students. Limp Covers, 4s.
"Dr. Selenka's Manual will be found useful by all Students of Zoology. It is a COMPRE-
HENSIVE and SUCCESSFUL attempt to present us with a scheme of the natural arrangement of
the animal world."-Edin. Med. Journal.
"Will prove very serviceable to those who are attending Biology Lectures.
translation is accurate and clear."-Lancet.
The
INORGANIC CHEMISTRY (A Short Manual of).
BY A. DUPRÉ, Ph.D., F. R. S., AND WILSON HAKE,
Ph.D., F.I.C., F.C.S., of the Westminster Hospital Medical School.
With Coloured Plate of Spectra. Crown 8vo. Cloth, 7s. 6d.
"A well-written, clear and accurate Elementary Manual of Inorganic Chemistry.
We agree heartily in the system adopted by Drs. Dupré and Hake. WILL MAKE EXPERI-
MENTAL WORK TREBLY INTERESTING BECAUSE INTELLIGIBLE."-Saturday Review.
"There is no question that, given the PERFECT GROUNDING of the Student in his Science,
the remainder comes afterwards to him in a manner much more simple and easily acquired.
The work IS AN EXAMPLE OF THE ADVANTAGES OF THE SYSTEMATIC TREATMENT of a
Science over the fragmentary style so generally followed. BY A LONG WAY THE BEST of the
small Manuals for Students."—Analyst.
HINTS ON THE PRESERVATION OF FISH,
IN REFERENCE TO FOOD SUPPLY.
BY J. COSSAR EWART, M. D., F. R. S. E.,
Regius Professor of Natural History, University of Edinburgh.
In Crown 8vo. Wrapper, 6d.
LONDON: EXETER STREET, STRAND.
28
CHARLES GRIFFIN & CO.'S PUBLICATIONS.
Royal 8vo.
With numerous Illustrations and 17 Lithographic Plates.
Handsome Cloth. Price 30s.
BRIDGE-CONSTRUCTION
(A PRACTICAL TREATISE ON):
Being a Text-Book on the Construction of Bridges in
Iron and Steel.
FOR THE USE OF STUDENTS, DRAUGHTSMEN, AND ENGINEERS.
BY
T. CLAXTON FIDLER, M. INST. C.E.,
Prof. of Engineering, University College, Dundee.
"Of late years the American treatises on Practical and Applied Mechanics
have taken the lead . . . since the opening up of a vast continent has
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but we look to the PRESENT TREATISE ON BRIDGE-CONSTRUCTION, and
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CC
An admirable account of the theory and process of bridge-design, AT ONCE
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LONDON: EXETER STREET, STRAND.
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29
FOSTER (C. Le Neve, D.Sc., Professor of Mining,
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ORE AND STONE MINING (A Text-Book of). With numerous
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GRIFFIN'S
ELECTRICAL
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GRIFFIN (John Joseph, F.C.S.):
CHEMICAL RECREATIONS: A Popular Manual of Experimental
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4to. Cloth.
Part I.-Elementary Chemistry, 2/.
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GURDEN (Richard Lloyd, Authorised Surveyor
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TRAVERSE TABLES: computed to Four Places Decimals for every
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*
** Published with Concurrence of the Surveyors-General for New South
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enable the user to ascertain the sines and cosines for a distance of twelve miles to withia
half an inch, and this BY REFERENCE TO BUT ONE TABLE, in place of the usual Fifteen
minute computations required. This alone is evidence of the assistance which the Tables
ensure to every user, and as every Surveyor in active practice has felt the want of such
assistance, few knowing of their publication will remain without them."-Engineer.
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ROCK-BLASTING (A Text-Book of).
applied to the blasting of Rocks, &c.
Large Crown 8vo. Cloth.
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The use of Explosives as
With numerous Illustrations.
[At Press.
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Large Crown 8vo. Cloth.
LONDON: EXETER STREET, STRAND.
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30
CHARLES GRIFFIN & CO.'S PUBLICATIONS.
Griffin's Standard Publications
FOR
ENGINEERS, ELECTRICIANS, ARCHITECTS, BUILDERS,
NAVAL CONSTRUCTORS, AND SURVEYORS.
PAGE
Applied Mechanics,
PROF. RANKINE,
39
(Student's),
W. R. BROWNE,
23
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Prof. RankiNE,
39
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Design of Structures,
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28
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45
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33
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IRELAND" (page 48).
LONDON: EXETER STREET, STRAND.
SCHWACKHÖFER AND
44
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PROF. ROBINSON,
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DENNIS MARKS,
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STANDARD PUBLICATIONS.
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PAGE
Geology (Stratigraphical),
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PROF. SEELEY,
36
(Practical),
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24
Mine-Surveying,
B. H. BROUGH,
23
Coal Mining,
H. W. HUGHES,
29
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PROF. LE NEVE FOSTER, 29
O. GUTTMANN,
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(Introduction to),
PROF. ROBERTS-AUSTEN,
42
Assaying,
Electro-Metallurgy,
C. & J. J. Beringer,
W. M'MILLAN,
22
34
Griffin's Students' Text-Books.
Biology,.
Botany, .
Chemistry-
PAGE
Davis, 26 Magnetism and Electricity,
Davis, 26
Mechanics,
PAGE
Jamieson, 33
Rankine, 40
Wright, 47
Stirling, 20
Jamieson, 32
Inorganic, Dupré & Hake, 27 | Physics (Experiments),
Qual. Analysis, Sexton, 44
99
Quant.
Recreations,
""
44 Physiology,
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Experiments, Wright, 47 | Zoology,
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32
CHARLES GRIFFIN & CO.'S PUBLICATIONS.
WORKS
BY ANDREW JAMIESON, M.INST.C.E., F.R.S.E.,
Professor of Engineering, Glasgow and West of Scotland Technical College.
SIXTH EDITION, Revised and Enlarged. Crown 8vo, Cloth, 7s. 6d.
A TEXT-BOOK ON STEAM AND STEAM-ENGINES.
WITH OVER 200 ILLUSTRATIONS, FOUR FOLDING-PLATES, AND
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PROF. JAMIESON'S ELEMENTARY MANUALS FOR
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66
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•
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"Should be in the hands of EVERY engineering apprentice."-Practical Engineer.
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33
PROF. JAMIESON'S ELEMENTARY MANUALS-Continued.
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the production
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STEAM BOILERS:
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(C
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STABILITY OF SHIPS.
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4I
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A MANUAL
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COMPRISING
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//"

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