LIBRARY 
 
 UNIVERSITY OF CALIFORNIA. 
 Clots 
 
THE 
 
 INDUSTRIAL AND ARTISTIC 
 
 TECHNOLOGY 
 
 OF 
 
 PAINT AND VARNISH 
 
 BY 
 
 ALVAH HORTON SABIN, M.S., 
 
 CHEMIST FOR EDWARD SMITI! & Co., NEW YORK. 
 
 Member of the American Chemical Society, the American Society of Mechanical Engineers, 
 
 the American Society for Testing Materials, the Society of Arts (London); Associate 
 
 Member of the American Society of Civil Engineers; Lecturer in New 
 
 York University and the Massachusetts Institute of Technology; 
 
 lately Professor of Chemistry in the University of Vermont. 
 
 FIRST EDITION-. 
 FIRST THOUSAND. 
 
 NEW YORK: 
 
 JOHN WILEY & SONS. 
 LONDON: CHAPMAN & HALL, LIMITED. 
 1904. 
 
Copyright, 1904, 
 BY 
 
 'ALVAH HORTON SABIN. 
 
 Entered at Stationers'* Hall, London. 
 
 ROBERT DRUMMOND, PRINTER, NEW YORK. 
 
PREFACE. 
 
 THE wise Quintilian remarked, that "If we can say what is 
 right we shall be delighted, though it may not be of our own 
 invention." This observation may well serve as a text for any 
 one who speaks of a technical art, such arts being of slow growth, 
 so that an account of any of them concerns itself much with the 
 past, and the knowledge of the expert, as a bookmaker, is largely 
 valuable for separating the true and the significant from that 
 which is untrue, or if true is of no relevancy or use. To no art 
 does this apply more than to that which concerns the making 
 and using of protective and decorative coatings, which have 
 been used from remote times; sometimes, though perhaps empir- 
 ically, in ways analogous or closely similar to the most approved 
 modern practice, then wandering off into the use of inefficient, 
 irrational, and unsatisfactory methods and materials. 
 
 The aim of the writer is to give a correct general outline 
 of the subject of Paints and Varnishes, with a brief account 
 of their modern use and of the principles which are involved in 
 their fabrication and application. Many of the facts herein 
 noted, though old, are practically unknown, and some of them 
 exactly anticipate recently patented processes; their value to 
 the public in that way is sufficient excuse for their republication. 
 Scarcely any patents in this line are of any value or validity; 
 and the ''secret processes" which are continually vended are for 
 the most part neither secret nor new. The only trade secrets lie 
 in the incommunicable intimate knowledge of the expert, and 
 are made valuable only by his unceasing care, vigilance, and. 
 
v PREFACE. 
 
 conscientiousness. Theories may, however, be made known, 
 ,and the attention of the student may be intelligently directed to 
 their application. 
 
 The author foresees that one criticism of this work will be 
 on the importance assigned to the use of oleo-resinous varnishes. 
 He can only say in reply that if he had the courage of his con- 
 victions it would have been made a great deal more prominent 
 than it is, and that the daily study of new problems, as well as 
 systematic observation of the results of work done many years 
 ago, produces in his mind the belief that it is in this direction 
 we must look for future progress. 
 
 Apology is perhaps due the reader for the lack of a very co- 
 herent plan in this treatise. In part the contents of this book 
 .are those things which seem most interesting or important to 
 the writer; in part they are things which long practical experi- 
 ence has shown to interest many other people. Things which 
 many people will wish to know are left out, in many cases because 
 of the limitations of the author's knowledge, but often because 
 the book is already too large; and to all the writer commends 
 the amiable maxim of Erasmus, that "a reader should sit down 
 to a book as a polite diner does to a meal. The entertainer 
 tries to satisfy all his guests; but if it should happen that some- 
 thing does not suit this or that person's taste they politely conceal 
 their feelings and commend other dishes, that they may not dis- 
 tress their host." 
 
CONTENTS. 
 
 CHAPTER I. 
 
 PAGE 
 
 INTRODUCTORY i 
 
 CHAPTER II. 
 EARLY HISTORY 6 
 
 CHAPTER III. 
 VARNISH : ORIGIN OF THE NAME 27 
 
 CHAPTER IV. 
 LINSEED-OIL 31 
 
 CHAPTER V. 
 LINSEED-OIL. BY DR. PARKER C. MC!LHINEY 39 
 
 CHAPTER VI. 
 MANUFACTURE OF VARNISH 71 
 
 CHAPTER VII. 
 TUNG-OIL 85 
 
 CHAPTER VIII. 
 JAPANS AND DRIERS. 87 
 
 CHAPTER IX. 
 
 ROSIN 95 
 
 
 
 CHAPTER X. 
 
 SPIRIT VARNISHES 103. 
 
 v 
 
VI CONTENTS. 
 
 CHAPTER XI. 
 
 PAGE 
 
 PYROXYLIN VARNISHES 112 
 
 CHAPTER XII. 
 OIL-PAINTS AND PAINTS IN JAPAN 1 1 8 
 
 CHAPTER XIII. 
 VARNISH OR ENAMEL PAINTS 140 
 
 CHAPTER XIV. 
 CHINESE AND JAPANESE LACQUERS 146 
 
 CHAPTER XV. 
 PROTECTION OF METALS AGAINST CORROSION 180 
 
 CHAPTER XVI. 
 WATER-PIPE COATING 258 
 
 CHAPTER XVII. 
 SHIP'S-BOTTOM PAINTS 290 
 
 CHAPTER XVIII. 
 SHIP- AND BOAT-PAINTING 297 
 
 CHAPTER XIX. 
 CARRIAGE-PAINTING ... 301 
 
 CHAPTER XX. 
 HOUSE-PAINTING 311 
 
 CHAPTER XXI. 
 FURNITURE-VARNISHING 327 
 
 CHAPTER XXII. 
 
 CONCLUSION 340 
 
 INDEX 3 6 5 
 
TECHNOLOGY OF PAINT AND VARNISH 
 
 CHAPTER i. 
 
 INTRODUCTORY. 
 
 WHEN we devote our attention to the subject of paint and 
 painting, we seem to encounter matters on which the vast major- 
 ity of commonly well-educated people feel almost entire ignorance 
 and concerning which the opinion of any self-constituted expert 
 is allowed to carry a weight which is out of all proportion, in 
 most instances, to its real value. In reality, although there are 
 many special cases where expert opinion is needed, and not a few 
 where the most learned and practised must feel uncertain, the 
 general principles involved are not difficult to understand, and 
 should be known to any one who is interested in the practical 
 matters of every-day life. The lack of such knowledge is a 
 source of discomfort and unnecessary expense to not a few who 
 are the victims of the ignorance and cupidity of those whom they 
 employ. Very many people have a fair practical knowledge 
 of carpentry, for instance, so as to be able to detect poor work- 
 manship, although unable to do such work themselves; some 
 have such a knowledge of plumbing; but few feel qualified to 
 critically examine a job of painting and varnishing, yet almost 
 everything which we touch or use has been in some way or 
 some part treated with a protective or decorative coating. 
 
 The beginner, who will probably find this book more helpful 
 
2 TECHNOLOGY OF PAINT AND VARNISH. 
 
 and suggestive than any one else, since the author cannot hope 
 to instruct the expert, must begin at the beginning, that is to say, 
 with a brief description, correct so far as it goes, of the most 
 essential materials and processes employed in the art, which 
 having learned, discussion of more detailed matters may be un- 
 derstood and the consideration of the more complex or difficult 
 compounds or methods will be left to later chapters. Let us 
 consider, then, which first, paint or varnish? It is difficult to 
 decide; like the celebrated problem of the bird and the egg: 
 "When I consider the beauty of the complete bird," said the 
 owl, "I think that must have been first, as the cause is greater 
 than the effect; when I remember my own childhood, I incline 
 the other way." Painting is not complete without varnish. Var- 
 nish is an ingredient of most paint, but paint is often thought of 
 as the foundation and varnish as the finish. It does not matter 
 much ; let us tell first about varnish. 
 
 Varnish: Definition. As the term is commonly used, this 
 is a substance which is applied as a liquid, and on exposure to 
 the air hardens and forms a thin and usually somewhat trans- 
 parent film (but some varnishes are black and nearly opaque), 
 which improves or better displays the surface over which it is 
 spread and to a considerable degree protects it from dirt and 
 injury. Some varnishes harden by a chemical change, which in 
 almost all cases is the absorption of oxygen from the air, others 
 by the evaporation of the solvent. The former are the most im- 
 portant and are made from certain resins, known as varnish- 
 resins or varnish-gums (though not gums in the strict sense, but 
 commercially so called), and linseed-oil. They are thinned with 
 spirits of turpentine. The process of manufacture is briefly as 
 follows : 
 
 Varnish: How Made. The resin is .put in a copper kettle, 
 which is then put over a hot fire until the resin is thoroughly 
 melted. The linseed-oil is then added and the mixture is heated 
 until the ingredients are well combined. It is then partially 
 cooled and is thinned with enough spirits of turpentine to make 
 it thin enough for use when cold. When such a varnish is spread 
 
INTRODUCTORY. 3 
 
 over a surface with a brush or otherwise it forms a thin film, 
 not more than a few thousandths of an inch in thickness, and of 
 course exposes a great deal of surface to the air. What first 
 happens is that the turpentine evaporates, then the oil and resin 
 compound absorbs oxygen and is converted into a hard, glossy 
 film. This may take a few hours or a few days. 
 
 Upon a little reflection it will be obvious that the relative 
 amounts of oil and resin will be an important factor in deter- 
 mining the quality of the compound; also, since the oil and tur- 
 pentine are always of about the same quality, while the resins 
 vary considerably, that the kind of resin used will be of impor- 
 tance ; and that different sorts of varnishes may be made for 
 different uses. 
 
 Spirit Varnish. Varnishes of another kind are made by 
 dissolving the resin (or other substance, but resins are chiefly 
 used) in a volatile liquid such as alcohol. Such a varnish, when 
 spread over a surface, loses its solvent by evaporation, and the 
 resin is then found in a thin uniform film, the liquid having served 
 as a mechanical means of uniformly spreading the resin over the 
 surface to be coated. 
 
 Linoxyn. If we spread a film of lard-oil or cottonseed-oil 
 over a non-absorbent surface, such as a piece of glass, and expose 
 it to the air, it does not seem to change, at least not for a long 
 time. The surface is simply made greasy; but if we use linseed- 
 oil in the same way, after a short time, or at most within a few 
 days, we find that a remarkable change has taken place. The 
 film is no longer a greasy fluid, but is a tough, leathery, solid sub- 
 stance, not in the least like oil. This new material has been 
 formed by the absorption of oxygen by the oil and is known as 
 oxidized oil, or linoxyn. This capacity for change into a tough 
 and permanent solid substance by the action of the air is an 
 unusual and valuable quality, which causes linseed-oil to be 
 chosen for making paint or varnish. In fact, the film of dried 
 oil without any addition of resin is a sort of varnish, and in some 
 countries is commonly spoken of as oil varnish. Such a film is 
 pale yellow in color, nearly transparent, like most varnish-films, 
 
4 TECHNOLOGY OF PAINT AND VARNISH. 
 
 and if it is desired to apply a colored film it is, of course, necessary 
 to add some color to it. 
 
 Pigments. This is done by mixing with the oil or varnish, 
 while it is a liquid and before it has been spread over the surface 
 to be coated, a colored pigment which is a solid substance, such, 
 for example, as a piece of colored rock which has been ground 
 to a fine powder. This pigment does not dissolve in the oil but 
 only mixes with it, converting it into a muddy, opaque, colored 
 liquid, of course of a thicker consistence than the pure oil or 
 varnish. 
 
 Paint. When this mixture, which is called paint, is spread 
 out hi a thin film the oil or varnish hardens, as has been described, 
 and acts as a cementing material, or binder, to hold the particles 
 of pigment on the surface which has been coated. But oil and 
 varnish are not the only cements, and it is not absolutely neces- 
 sary to use them in making a paint. We may mix the colored 
 pigment with a dilute solution of glue, as is done in making kal- 
 somine, and such a mixture is used in making water-color or 
 distemper paintings. 
 
 Water-colors. There is no reason why painting done in dis- 
 temper (water-color) should not, after it gets quite dry, be var- 
 nished with any ordinary varnish, to enhance its beauty and make 
 it more permanent, and in fact this is often done and has been 
 from the earliest times. 
 
 Encaustic Painting. In former times there was still another 
 sort of painting, which has now gone out of practice, called en- 
 caustic painting. This was done with wax, colored by mixing it 
 with suitable pigments, applied in a melted condition, and some- 
 times covered with a varnish. Wax in solution is still employed 
 as a coating, especially for floors, but encaustic painting was done 
 with melted wax and the finished work commonly glazed by hold- 
 ing a hot iron or a torch in front of it. Such painting was very 
 durable when not exposed to heat nor to the weather, but could 
 not be handled. It was used for mural decorations. Instead of 
 a spirit, varnish, a powdered resin was sometimes employed, 
 which was sifted over the surface and fixed by being melted by 
 
INTRODUCTORY. 5 
 
 the application of a hot iron. Sandarac was the resin used, and 
 this was the old English pounce, sprinkled over the surface from 
 a pouncet-box or pounce-box like a pepper-box. There are many 
 other minor varieties of both paint and varnish, but if the reader 
 will remember what has just been told, especially the practice of 
 making oleo-resinous varnishes by first melting the resin and then 
 adding the oil, cooking the compound, and afterward thinning it, 
 he will be able to clearly understand the modifications and addi- 
 tions which are to be made in the later descriptions of a more 
 detailed character. 
 
CHAPTER II. 
 
 EARLY HISTORY. 
 
 KNOWLEDGE of the early history of any art is fragmentary 
 and apt to be to some extent conjectural, but none the less inter- 
 esting. It is, therefore, without apology that a few facts are here 
 given, not as a complete or definite history, but only in a tenta- 
 tive way, as a possible nucleus about which other students with 
 better opportunities may group a more systematic series of studies, 
 on a subject which appears to have received less attention than 
 its importance and intrinsic interest deserve. 
 
 The use of both decorative and protective coatings is of great 
 and unknown antiquity. Savages use both mineral and vege- 
 table colors to decorate their persons, their clothing, and their 
 abodes; anointing the body with oil as a protection against the 
 weather is a common practice. Oil is also used on dressed 
 skins of animals to make them pliable and water-proof, and tem- 
 porary and permanent dwellings, and boats, are made water- 
 proof by the use of fatty and resinous bodies. When Noah built 
 the ark and coated the seams with pitch he was doubtless follow- 
 ing the most approved system of use of protective coatings on 
 structural materials, which was then probably of remote antiquity 
 and traditional origin, and which he may have learned when he 
 was a boy, four or five hundred years before. 
 
 Grease-paints. It is only reasonable to suppose, and this is 
 borne out by the present practice of savage tribes, that the earliest 
 paints may have been pigments mixed with grease or fat. Such 
 a paint adheres to the human skin with considerable persistence, 
 yet it may be removed by thorough washing, and of this nature 
 
 are the grease-paints still used by actors. This may fairly claim 
 
 6 
 
EARLY HISTORY. 7 
 
 to be the oldest kind of paint. When such a paint is applied to 
 leather or wood it is practically impossible to remove it and 
 probably its protective action is considerable. The use of oil 
 alone as a preservative, e.g., to make the wood of bows and lances 
 water-proof, is perhaps a forerunner of varnish, being closely 
 allied to the use of varnish on violins and other musical instru- 
 ments. 
 
 Egyptian Varnish. So far as is yet known to the author, the 
 oldest varnish in existence is that on the wooden mummy-cases 
 brought from Egypt. This is probably twenty-five hundred years 
 old. The only chemical examination of this which has been pub- 
 lished was made by Professor J. F. John, of Berlin, about 1822. 
 Lieutenant- General H. Von Minutoli conducted an exploring ex- 
 pedition in Egypt, and published an account under the title "Reise 
 zum Tempel des Jupiter Ammon, etc., nach Ober-Aegypten in den 
 Jahren 1820-1821." In an appendix to this book (which may 
 be seen in the New York Public Library) is a short paper by 
 Dr. John describing this varnish, which he found to be insoluble 
 in water, soluble in alcohol, and thrown down as a gummy pre- 
 cipitate by diluting the alcoholic solution with water. He con- 
 cluded that it was a compound of resin with oil, but I infer that 
 he meant a solution of resin in an essential oil, like oil of cedar, 
 which is about the same as oil of turpentine, since some of the 
 varnishes of the middle ages were of this sort (in fact they were 
 the most common varnishes in Professor John's time), and he 
 knew that the Egyptians were able to make oil of cedar in early 
 times. 
 
 Turpentine. Herodotus, who visited Egypt about 460 B.C., 
 describes the use of oil of cedar for embalming. These more 
 common essential oils were prepared both by the Egyptians and 
 the Greeks before the invention of the still. One of the earlier 
 methods was to put the crude turpentine in* a pot and lay over 
 the top of the pot some sticks which supported a fleece of wool. 
 When the contents of the pot was heated, the essential oil con- 
 densed in the wool, from which it was squeezed out. A good 
 account of the early methods and references to the ancient liter- 
 
8 TECHNOLOGY OF PAINT AND VARNISH. 
 
 ature of the subject is to be found in Gildermeister and Hoffman's 
 Volatile Oils, of which an English translation has been made by 
 Dr. Kremers of the University of Wisconsin. 
 
 The varnish in question may be seen on mummy-cases hi the 
 Metropolitan Museum of Art in New York City. It is of a pale- 
 yellow color, surprisingly free from cracks, very hastily and 
 roughly applied, as though smeared on with a flat blade. This 
 suggests that it may have been a compound of a resin and a 
 fixed oil. We know that the ancients of all nations knew how 
 to prepare vegetable oils,, which were use<jj as food, and also that 
 they raised flax, 1a,nd it is n'ot unTTefy ttiaT linseed-oil may have 
 been used as a solvent for some of the African re'sins, which arc 
 to this day perhaps the most important varnish-resins. A var- 
 nish made with five or six parts of oil to one of resin without any 
 essential oil as a solvent would, when warm, be applied exactly 
 as the varnish on these mummy-cases was, would take, as that 
 apparently did, a partial set on cooling, having practically no 
 flowing quality, and would be extremely durable. No other var- 
 nish is known to the author which would behave in this way; 
 yet this is largely a matter of conjecture, no samples being avail- 
 able for analysis. This much, however, is clear, that the Egyp- 
 tians made a good durable varnish which has stood exposure to 
 the air twenty-five hundred years and still looks well. If the 
 varnish, as they made it, was a solution in oil of turpentine, there 
 is no reason why it should not have been properly thinned, as 
 it would then flow out under the brush, and it would also seem 
 that it might have been used as a vehicle for painting, while in 
 fact all their painting seems to have been done with pigments 
 mixed in a solution of glue. 
 
 Glue Size. This painting in size, or distemper, seems to be 
 the oldest which has come down to us. In a dry climate it is 
 very lasting; and the Egyptians were expert glue-makers, some 
 of their glued wood joints having lasted three thousand years. I 
 have been told by Mr. Hewitt (of the Cooper-Hewitt Company) 
 that there exist descriptions on early papyrus rolls of the Egyp- 
 tian methods of glue-making showing that they had the essential 
 
EARLY HISTORY. y 
 
 principles of the present methods, and made practically the same 
 product as some of the best glue made now. 
 
 Wax Paint for Ships. Much of the painting done by the 
 Romans, as, for example, at Pompeii, appears to have been with 
 size, or glue solution, as the vehicle, but they were also acquainted 
 with encaustic painting, where the colors are mixed with wax. 
 Pliny says that "when it became the fashion to paint ships of 
 war, a third method was introduced of melting the wax with fire 
 and using a brush. Paint applied to ships in this way cannot be 
 destroyed either by the action of the sun or of the brine or wind." 
 This sounds very much as though Pliny were copying from an 
 early advertisement. It is curious to note, as will be shown 
 later, that this method of applying a melted non-drying paint is 
 still in extensive use on the exterior of ships, and almost nowhere 
 else. Clarified beeswax was used in ancient times; with it were 
 mixed coloring matters, and in this way were made paints which 
 formed films of great thickness as compared with any ordinary 
 paint-film and, being practically impervious to water, were very 
 permanent when preserved at a uniform and not too high tem- 
 perature. 
 
 Vernix. In considering the history of this subject, it is first 
 of all to be remembered that prior to the seventeenth century the 
 word varnish (Latin, vernix or vernisium), was not primarily 
 used to mean a liquid composition, but a dry resin, which when 
 melted and boiled with linseed-oil formed a liquid called ver- 
 nice liquida by the early Italian writers, and corresponded to our 
 modern varnish. This use of the term is analogous to our use of 
 the word glue, by which we mean primarily a dry substance and 
 secondly the solution of the same ready for use. The resin has 
 always been regarded as the essential and distinguishing com- 
 ponent of varnish; even in the case of varnishes made from 
 boiled oil alone, it is common to speak of the oil as being con- 
 verted into resin. 
 
 Painters' Bills in the Thirteenth Century. The fact that var- 
 nish was a dry resin is shown in many ways. For example, in 
 the early English accounts of expenditures for the king, the 
 
10 TECHNOLOGY OF PAINT AND VARNISH. 
 
 quantity of varnish is always noted by weight, and of oil by meas- 
 ure. In the period of 1274 to 1277, m tne early part of the reign 
 of Edward L, an account, apparently relating to the Painted 
 Chamber, contains the following items: 
 
 To Reymund, for seventeen pounds of white lead Us. X d. 
 
 To ' ' " sixteen gallons of oil XVI s. 
 
 To " " twenty -four pounds of varnish .... XII s. 
 
 To Hugo le Vespunt, ' ' eighteen gallons of oil XXI s. 
 
 To Reymund, " one hundred leaves of gold Ill s. 
 
 To " " twenty-five pounds of varnish XI s. Id. 
 
 To William, the painter, and his helper, for the painting of 
 
 twelve mews XXXVI s. 
 
 To " ' ' * ' for seven score and twelve pounds of 
 
 green for the same LXXV s. IV d. 
 
 To Stephen Ferron, ' ' twenty pounds of white Us. 
 
 To " " ' one gallon of honey XII d. 
 
 Item, ' one gallon of white wine Ill d. 
 
 small brushes, and eggs Ill d. 
 
 yellow VI d. 
 
 size XII d. 
 
 These accounts clearly show that; dry substances were sold by the 
 pound and liquids by weight. The use of honey, eggs, and size 
 was for distemper painting, in all likelihood. So also in the 
 records of the church of St. Jacopo at Pistoja, Italy, in 1347, is 
 an expense for one pound of varnish, soldi VI. 
 
 These illustrations could be largely extended. The Italian 
 writers on painting constantly speak of varnish and of liquid 
 vsfrnish as entirely distinct. It appears to be the common opin- 
 ion of the early writers that the substance properly known as 
 varnish was amber, which was the resin now known by that 
 name, but was also applied apparently to some of the hard African 
 resins which reached Europe, either through Egypt or from India. 
 Formerly a considerable amount of Zanzibar resin reached India 
 and was marketed from that country. Salmasius, the greatest 
 classical scholar of the early part of the seventeenth century, says 
 the term "vernix" was misappropriated to mean u sandarac," 
 because of the resemblance of that resin to amber. Some of the 
 dictionaries of the middle ages say that vernix is sandarac, and 
 
EARLY HISTORY. 1 1 
 
 that it was a dry resin. They also define liquid varnish as the 
 resin dissolved in oil. My own belief is that there have always 
 been different kinds of varnishes, both the resins and the liquids, 
 and that the best varnish was amber, the inferior being sandarac. 
 The latter term included many resins which appear like it, and 
 grade down to common rosin, which was used as varnish in very 
 early times. 
 
 Incense. These inferior resins were commonly spoken of as 
 frankincense, or incense, which was also used as synonymous with 
 varnish. Thus we read of the application of incense, or frankin- 
 cense, to pictures as a finishing touch. Amber and similar resins 
 have always been costly and rare, and there has always been a 
 substitution for them of common and cheaper resins, either fraudu- 
 lently or, more generally, as a cheaper but sufficiently good 
 material. Certainly, from the present time back as far as we 
 have any definite history of varnish, there always have been two 
 well-defined grades, one made from hard resins, the other from 
 those which are both cheaper and more easily manipulated. It 
 is in fact interesting to notice how varnish recipes go in pairs, 
 one for amber and the other for sandarac, among nearly all 
 writers on the subject. It was an early practice, which has 
 probably not yet become entirely obsolete, to sprinkle powdered 
 resin over paper on which writings or drawings had been made. 
 This served to fix the writing and was sometimes made more 
 certain by the application of a heated iron. Sandarac, or some 
 similar resin, was used for this purpose, and the hard resins like 
 amber are not suited for such service. As this use of sandarac 
 is of considerable and probably great antiquity, it is an illustra- 
 tion of the proper use of these softer recent resins. Sandarac, 
 mastic, olibanum, and other similar resins come from northern 
 Africa and western Asia and have, therefore, been known from 
 most ancient times, and juniper resin, which is closely allied to 
 sandarac and has been used for it, is very widely distributed. 
 
 Treatise of Theophilus. The earliest important treatise of 
 the middle ages on technology is the Schedula Diversarum 
 Artium of Theophilus Presbyter, a German or Swiss monk. 
 
12 
 
 TECHNOLOGY OF PAINT AND VARNISH. 
 
 There exist several MS. copies of this work, from which trans- 
 lations have been made, the most recent of which was by Dr. 
 Albert Ilg of Vienna, 1874, by whom the various authorities and 
 commentators have been carefully studied. Ilg thinks Theophilus 
 wrote in the eleventh century. Lessing, who also studied The- 
 ophilus, regards him as belonging to the tenth century and to have 
 been identical with Tutilo, a monk of the monastery of St. Gall, 
 Switzerland. The name Tutilo, or Tuotilo, is said to be the same 
 as Theophilus. Many monasteries of the middle ages gained 
 celebrity by the skill of their artists, and that of St. Gall was 
 especially distinguished in this respect, Tutilo and Notker, monks 
 of this convent, being the most celebrated painters, sculptors, 
 and gold-workers of their time in Germany. Tutilo was con- 
 temporary with the Abbot Salorno of St. Gall, and made for 
 him a golden crucifix of wonderful workmanship. Ekkehard 
 speaks of Tutilo as "mirificus aurifex." He was also musician, 
 poet, orator, and statesman. The Emperor Charles the Thick 
 complained that such a man should be shut up in a convent. 
 However this may be, the treatise in question is not later than 
 the eleventh century and it does not claim to be original, but to 
 be a digest of standard and well-known methods and processes. 
 It quotes largely from an earlier work of the same kind by Erac- 
 lius, and some of the recipes are in the Lucca MS. of the eighth 
 century. Eraclius collected formulae as far back as Dioscorides, 
 early in the first century. 
 
 His Formula for Varnish. Theophilus gives a formula for 
 making varnish as follows: 
 
 Pone oleum in ollam novam 
 parvulam et adde gummi quod 
 vocatur fornis, minutissime tri- 
 tum, quod habet speciem luci- 
 dissimi thuris, sed cum frangitur 
 fulgorem clariorem reddit ; quod 
 cum super carbones posueris, 
 coque diligenter sic ut non bul- 
 
 Put some linseed-oil into a 
 small new jar, and add some of 
 the gum which is called fornis 
 (varnish), very finely powdered, 
 which has the appearance of the 
 most transparent frankincense, 
 but when it is broken it gives 
 back a more brilliant lustre; 
 
EARLY HISTORY. 
 
 liat, donee tertia pars consuma- 
 tur; et cave a flamina, quod 
 periculosum est nimis, et diffi- 
 cile extinguitur si accendatur. 
 Hoc glutine omnis pictura super 
 linita lucida fit et decora ac 
 omnino durabilis. Compone 
 quatuor vel tres lapides qui 
 possent ignem sustinere ita ut 
 resiliant et super ipsos pone 
 ollam rudem, et in earn mitte 
 supradictum gummi fornis, quod 
 Romana glassa vocatur, et su- 
 per os hujus ollae pone ollam 
 minorem, quae habeat in fundo 
 modicum foramen. Et circum- 
 lineas ei pastam, ita ut nihil 
 spiraminis inter ipsos ollas exeat. 
 Habebis etiam ferrum gracile 
 manubrio impositum, unde com- 
 movebis ipsum gummi, et cum 
 quo sentire possis ut omnino 
 liquidum fiat. Habebis quoque 
 ollam tertiam super carbones 
 positam, in qua sit oleum cali- 
 dum, et cum gummi penitus 
 liquidum fuerit, ita ut extreme 
 ferro quasi filum trahitur, in- 
 funde ei oleum calidum, et ferro 
 commove, et insimul coque ut 
 non bulliat, et interdum extrahe 
 ferrum et lini modice super lig- 
 num sive super lapidem, ut 
 probes diversitatem ejus; et 
 hoc caveas in pondere ut sint 
 duae partes olei et tertia gummi. 
 
 which, when you have placed 
 over the coals, cook carefully so 
 that it may not boil, until a third 
 part is evaporated; and guard 
 from the winds because it is dan- 
 gerous to a high degree and diffi- 
 cult to extinguish if it takes fire 
 from the top. Every picture 
 smeared over with this glaze be- 
 comes clear and beautiful and in 
 every way durable. Set up four 
 or three stones which are able to 
 stand the fire so that they lean 
 apart ; on these place a common 
 pipkin, and in this put the above- 
 mentioned portion of the gum 
 fornis, which is called Roman 
 glassa (amber), and over the 
 mouth of this pot set a smaller 
 pipkin which has in the bottom 
 a middling-sized hole. And 
 around these put luting so that 
 nothing may get out of the crev- 
 ice between these pots. You 
 should have, moreover, a slender 
 iron rod set in a handle with 
 which you may stir this mass of 
 gum, with which you may feel 
 that it is entirely liquid. You 
 must have also a third pot set 
 over the coals, in which is hot oil, 
 and when the interior of the gum 
 has become liquid, so that with 
 the end of the iron rod it may be 
 drawn out like a thread, pour 
 into it the hot oil and stir it with 
 
TECHNOLOGY OF PAINT AND VARNISH. 
 
 Cumque ad libitum tuum cox- 
 eris diligenter, ab igne removens 
 t discoperiens, refrigerari sine. 
 
 the iron rod, and at the same time 
 cook it so that it may not boil, 
 and from time to time draw out 
 the rod and smear it properly 
 over a piece of wood or stone, 
 that you may find out if there is 
 separation; and see to this that 
 in weight there be two parts of 
 oil and the third of gum. And 
 when, in your judgment, you 
 have cooked it thoroughly, re- 
 moving it from the fire and un- 
 covering it, cool it out of doors. 
 
 In regard to the resin mentioned in this by the name of " glassa" 
 it is proper to observe that Tacitus (De Moribus Germanorum, 
 c. xlv) and Pliny (1. xxxvii, c. ii) both say this was the ancient 
 German name for amber. It will be observed that nothing is 
 said in the foregoing about thinning the varnish with spirits of 
 turpentine. The "varnish would contain 28 gallons (U. S.) of oil 
 to 100 pounds of resin. It was to be warmed and smeared over 
 the picture, using the fingers rather than a brush for this purpose. 
 This practice was no doubt of great antiquity. It was the com- 
 mon practice in the time of Cennini, who said: "Place the picture 
 level and with your hand spread the varnish well over the surface. 
 If you do not choose to spread the varnish with your hand, dip a 
 piece of clean sponge into the varnish and spread it over the pic- 
 ture in the usual manner" (ch. 155). 
 
 Formula from Alcherius, 1350. Another old varnish for- 
 mula is from Alcherius, who gives, under date of 1398, the follow- 
 ing recipe, which was communicated to him by Anthonio de 
 Compendio, then an old man, as an old and well-known formula : 
 "To make a good liquid varnish for painters: Take aromatic 
 glassa, which is dark and dull outside and inside when broken is 
 clear and shining, like glass. Put some of it into a new jar, on 
 the mouth of which must stand another jar, which must be well 
 
EARLY HISTORY. 1 5 
 
 luted to it. The upper jar must be well covered so as to be smoke- 
 proof and its bottom must be pierced. Then light a fire beneath 
 it and leave it until the glassa is melted, when you must take two 
 parts of linseed- or hempseed- or nut-oil, and heat this oil slowly 
 over a fire, not making it too hot. You must then pour it on the 
 said glassa, make the fire hotter, and let it boil for an hour, taking 
 care that the flame does not touch it. Then take it off the fire and 
 put it into a clean vessel, and when you wish to varnish any dry 
 painting take some of this liquid and spread it over the painting 
 with your fingers, for if you were to do it with a pencil, it would 
 be too thick and would not dry. You will thus have good var- 
 nish." 
 
 Formulae from Jacobus de Tholeto, 1440. About the same 
 date are the following by Magister Jacobus de Tholeto, from the 
 Bolognese MS. from the convent of S. Salvatore in Bologna, 
 first half of the fifteenth century : 
 
 "S. 206. To make liquid varnish: Take of the gum of the 
 juniper (sandarac) two parts, and one part of linseed-oil. Boil 
 them together over a slow fire, and if the varnish appears too stiff, 
 add more of the oil and take care not to let it take fire, because 
 you would not be able to extinguish it, and even if you would 
 extinguish it the varnish would be dark and unsightly. Let it 
 boil half an hour and it will be done." 
 
 "S. 207. To make liquid varnish in another manner: Take 
 one pound of linseed-oil and put it into a new glazed jar, and then 
 take half a quarter of an ounce of roche alum in powder and an 
 equal quantity of minium or vermilion ground fine, and half 
 an ounce of incense, also ground fine. Mix all these ingredients 
 together and put them into the oil to boil, stirring it with a stick, 
 and when the oilis boiling, as it is likely to run over, have another 
 glazed jar ready and put it by that which contains the oil, so as 
 to catch the oil which runs over, in order that it may not run on 
 the ground ; and in this manner make it boil up three or four times, 
 and each time pour back what has run over on that which is boil- 
 ing in the jar. Having done this, set fire to the oil on the right- 
 hand side with a lighted straw and let the oil burn on the upper 
 
1 6 TECHNOLOGY OF PAINT AND VARNISH. 
 
 part; so that the jar may not burn on the inside, on account of 
 the too great heat, for otherwise the oil would smell unpleasant. 
 When you light the oil with the straw, remove the jar from the 
 fire, and let it burn while you can say three paternosters, then 
 extinguish the oil with a wooden cover, putting it upon the jar, 
 and when it is extinguished remove the cover in order to let the 
 vapor escape, then put it back over the fire. Do this three times 
 and it is done." 
 
 Formulae from the Marcian MS., 1520. A hundred years 
 later, in the first part of the sixteenth century, we find in a MS. 
 of the library of San Marco in Venice the following : 
 
 "S. 402. A most excellent, clear, and drying varnish proper 
 for colors, both in oil-painting and the other kinds of painting: 
 Take two ounces of clear and good nut-oil, one ounce of clear and 
 good Greek pitch (colophony), and half an ounce of clear and 
 good mastic. Grind the pitch and the mastic (separately) to a 
 very fine powder, and place the oil in a clean glazed pipkin over 
 a charcoal fire and let it boil gently until it is done sufficiently, 
 i.e., until one-third has evaporated. Then put in the powdered 
 pitch, a little at a time, mixing and incorporating it well. After- 
 ward throw in the mastic in the same manner, and when it is 
 dissolved take the varnish off the fire and strain it through a fine 
 and old linen cloth." 
 
 "S. 404. A most excellent varnish for varnishing arquebuses, 
 crossbows, and iron armor: Take of linseed-oil two pounds, san- 
 darac one pound, Greek pitch two ounces. Boil the oil, then dis- 
 solve in it the other ingredients and strain through a much- worn 
 linen cloth, and when you wish to use the varnish scrape and 
 polish the work and heat it in a hot oven, because that is the best 
 place to heat it, and when it is at a proper heat, i.e., when the var- 
 nish adheres to it firmly and does not blister from too great heat, 
 then lay it on thinly with an instrument of wood, so that you may 
 not burn your fingers, and it will make a beautiful changing color. 
 
 "And if you supplied the place of Greek pitch with naval pitch, 
 I think it would make the work black when you varnished it. 
 
 "When making the varnish, you must boil it well, even to such 
 
EARLY HISTORY. 17 
 
 a degree as to make it foam and bubble, if necessary, in order that 
 it may be clear and thick." 
 
 "S. 405. An excellent common varnish, good for varnishing 
 whatever you please : Take two ounces of clear and good linseed- 
 oil and one ounce of clear and good Greek pitch; but two ounces 
 of the latter will also make the varnish thicker and give it more 
 body. Boil the oil over a slow fire and then put in the pounded 
 pitch a little at a time, that it may incorporate well, and add a 
 little roche alum previously burnt and powdered, and when it is 
 incorporated and boiled sufficiently, i.e., when you try a little of 
 it in your fingers and find that it is done, strain it and keep it. 
 When it is used it will be beautiful and good, and if it is too tena- 
 cious you will dilute it with a little oil. And if you wish it com- 
 moner; so as to sell it at a larger profit, take ten ounces of oil to 
 one of pitch; and if you use black pitch, it will be good for pom- 
 mels of swords, spurs, and similar things." 
 
 The following is also from the MS. of San Marco: "Item a 
 varnish. Take one pound of linseed-oil, boiled in the usual way, 
 and anoint the vessel with it while hot, and four ounces of pow- 
 dered amber. Place it to dissolve with the bottle closed on the 
 coals, and when it is nearly dissolved pour in the hot oil and stop 
 it up. Afterward, at the proper time, when the whole is dissolved, 
 stir in three ounces of alum. Dilute the varnish with the neces- 
 sary quantity of naphtha, or linseed-oil, or spirit of wine, and use 
 it warm. . . . 
 
 "Take one ounce of sandarac, ground to a very fine powder, 
 and three ounces of clear nut-oil. Heat the oil in a glazed pipkin 
 over a slow fire in the same manner as linseed-oil is boiled. Then 
 add the powdered sandarac, a little at a time, until it is dissolved. 
 Add to it also at the same time as much clear incense finely pow- 
 dered as will impart a pleasant savor to the whole mixture, stirring 
 it well that it may dissolve ; and if you please, you may add also a 
 sufficient quantity of burnt and powdered alum to have a sensible 
 effect on the whole composition, and the addition of the alum will 
 improve the varnish, if you stir it until it is dissolved. It should 
 then be strained through a linen cloth and afterward exposed to 
 
1 8 TECHNOLOGY OF PAINT AND VARNISH. 
 
 the sun and dew until a sediment is formed, which should be 
 separated by pouring off the clear varnish, after which it will be 
 ready for use." 
 
 Formulae from Rossello, 1575. The following are from the 
 Secreti of Timotheo Rossello, Venice, 1575: "To make liquid 
 varnish: Take one pound of sandarac resin and four pounds of 
 linseed-oil. Place the oil on the fire to boil; take another vessel 
 for the resin, adding three ounces of oil, little by little; stir con- 
 tinually with a spatula and let the oil continue to boil till the 
 whole is transferred to the vessel containing the varnish. Keep 
 up a good fire for the said varnish and in order to know when the 
 mixture has been boiled enough, and if it remains thick and some- 
 what firm the varnish is made. Then remove it from the fire and 
 strain through a cloth. 
 
 "To make a superior liquid varnish: Take three pounds of 
 yellow amber and six ounces of pulverized brick. Make a fur- 
 nace with two orifices below, each orifice having bellows adapted 
 to it. The fire, which should be of charcoal, requires to be great. 
 Let there be an opening above; in this fit a glazed vessel which 
 is to be luted to the opening so that the fire may not penetrate, 
 for if it were to do so the ingredients would presently be in a 
 flame. Place your amber in the vessel with as much of the oil as 
 will cover it, then blow with a bellows and make a great fire till 
 the amber dissolves. As there is great danger of fire, have a 
 wooden trencher ready, wrapped round with a wet cloth, and if 
 the varnish should catch fire cover the vessel with the trencher. 
 Meanwhile boil in another vessel the remainder of the oil, mak- 
 ing a moderate fire with the charcoal, but still taking care that the 
 flame does not ascend. Let this oil continue to boil till it be re- 
 duced one-third. Then when the amber is dissolved in the small 
 quantity of oil first mixed with it, as above described, throw in the 
 remaining oil which you have heated to ebullition, and mix 
 together for the space of five minutes, so as to incorporate all 
 well. Then remove from the fire and throw in the pulverized 
 brick above mentioned. Stir again a little, then cover the vessel, 
 let the contents settle, and the varnish is made." 
 
EARLY HISTORY. *9 
 
 Mathioli, 1549. Mathioli in 1549 said: "The juniper pro- 
 duces a resin similar to mastic, called (though improperly) san- 
 darac. This, when fresh, is light in color and transparent, but 
 as it acquires age it becomes red. With this resin and linseed- 
 oil is prepared the liquid vernix which is used for giving lustre 
 to pictures and for varnishing iron." 
 
 Formula from Libravius, 1599. Libravius, in his Singularia, 
 in 1599-1601, says: "Take three pounds of linseed-oil; of burnt 
 alum, purified turpentine, and garlic, each half an ounce. Mix 
 these in the oil and boil till it ceases to froth. Then take one 
 pound of amber (succinum), place it in a vessel, the cover of 
 which has an opening about the size of the little finger. Pour in 
 a little oil. Melt the amber on a tripod and stir it with an iron 
 rod inserted through the opening in the cover, to assist the lique- 
 faction. When dissolved, mix with 'the oil before prepared and 
 boil to the consistence of a varnish." 
 
 Caneparius, 1619. The following is by Caneparius (Venice, 
 1619): 
 
 "The sandarac of the Arabs is called Dry Vernix. From 
 this and linseed-oil is made the dark liquid vernix so well 
 adapted for giving lustre to pictures and statues. It even adds 
 splendor to iron and preserves it from rust." 
 
 Formula from Albert!, 1750. Alberti (Magdeburg 1750), 
 writing on amber, says: "Dissolve one pound of pulverized 
 amber in an earthen vessel, on a charcoal fire. As soon as it 
 is melted pour it on an iron plate and again reduce it to powder. 
 Then place it in an earthen vessel, first adding linseed-oil already 
 boiled and prepared with litharge. The solution is completed 
 by the addition of spirits of turpentine." 
 
 The foregoing formulae, which are selected from a great 
 number known to the writer, give a fair idea of the knowledge 
 of the art of varnish-making in the middle ages. The con- 
 clusion I have reached from a careful study of the whole subject, 
 as far as the records are accessible to me, is that the best varnish 
 was made from amber, or rather from what was called amber, 
 
20 TECHNOLOGY OF PAINT AND VARNISH. 
 
 the term being made, as the 1 records show (but which are not 
 included here on account of lack of space), to include certain 
 hard varnish resins from the East. This varnish was made 
 originally without spirits of turpentine or any other thinner, 
 and in order to have it sufficiently liquid it was made with a 
 large amount of oil, from twenty-five to fifty gallons of oil to 
 the hundred pounds of resin (to put it in the terms of modern 
 varnishes), well cooked and slow-drying. The oil was carefully 
 refined, as will be described later, and probably was made dry- 
 ing with litharge and possibly with umber, but the painter 
 expected to allow a long time for his work to dry, in some cases 
 a year or more for the paint to dry before the final varnishing; 
 and if haste was necessary, the use of an oven or other source 
 of heat was the alternative. There was practically no progress 
 for eight hundred years, the varnish made by Theophilus being 
 quite equal to that made in the eighteenth century, and when 
 a really good varnish was desired recourse was had to this old 
 formula, which was handed down from one generation of artisans 
 to another. There were no varnish-makers in the modern 
 sense until the nineteenth century, i.e., no established business 
 of varnish-making, but every important manufacturing estab- 
 lishment had its own varnish-maker, who made up small quan- 
 tities, but the more important apothecaries in the large cities 
 sold, and in some cases made, varnish; sometimes "common 
 liquid varnish" only, which was made with sandarac or other 
 cheaper resin; sometimes this and also amber varnish. But 
 always small batches were made. Near the end of the eighteenth 
 century Tingry, the most noted varnish-maker of his time, warns 
 his followers that six ounces of amber is as large a melt as is 
 advisable. It will further be shown that varnish was known 
 before the Christian era, and there can be no reasonable doubt 
 that knowledge of the art was continuous from at least as early 
 as 500 B.C., when those varnishes were made which still exist 
 on the Egyptian mummy-cases already mentioned, down to 
 the present time, and it seems likely that the formula of Theophilus 
 may have been handed down from those early Egyptian work- 
 
EARLY HISTORY. 21 
 
 men. This latter conclusion may strike the reader as an unsup- 
 ported conjecture; and since the matter is one of interest to all 
 those who care to know about the origin of the art, it is worth 
 while to give some of the grounds which seem to support such 
 a proposition. 
 
 Varnish-making Probably Continuous from Egyptian Times. 
 In the first place, nothing is so conservative as tradition in 
 artisanship. We still wear the buttons on our coat-sleeves which 
 were used by our ancestors in the dark ages to fasten back their 
 sleeves when they went into battle, and those on the backs of 
 our coats with which they buttoned up their skirts to ride in 
 the saddle. Hundreds of such instances are known to the 
 student. Those who have not studied such things cannot 
 imagine how persistent habits and methods of workmanship 
 are. The fact that the process of Theophilus which he put 
 down as the old and approved one, continued for hundreds of 
 years after his time and is still almost exactly practised, only 
 with some additions and on a larger scale, a thousand years 
 after it was known to the men who communicated it to him, 
 is in reality a substantial reason for believing that it had then 
 existed a long time. This is also strongly supported by the 
 appearance of the Egyptian varnish. Too much stress cannot 
 be laid on the fact that here we are not dealing with tradition 
 or history, but with the real and actual thing. Here is the var- 
 nish, just as it was applied twenty-five hundred years ago. It 
 is just as real as the mummy itself, and is just as absolute a proof 
 that varnish was made in those days as the mummy is proof 
 that people lived in those days. Here, I say, is the actual and 
 real varnish. It was made with resin and oil. It was smeared 
 on, possibly with a spatula, but more likely with the fingers, 
 certainly not put on with a brush nor in a thinly fluid condition. 
 Such a varnish as Theophilus describes would look as that looks, 
 and in all probability would last as that has endured. 
 
 Materials Known to the Egyptians. To the question as to 
 whether the Egyptians knew of the materials we can say that 
 obviously they had suitable materials and that there is no reason 
 
22 TECHNOLOGY OF PAINT AND VARNISH. 
 
 why they may not have been the same. As to resins, we know 
 that for thousands of years the Egyptians had made warlike 
 incursions into tropical Africa, whence come our best varnish- 
 resins, and it is extremely probable that some commerce existed 
 between those regions and Egypt; also that no resins native to 
 northern Africa or Arabia are known to be as durable as these 
 varnishes have shown themselves to be. The Chinese have 
 from very ancient times imported varnish-resins from the East 
 Indies which shows that resins are naturally objects of commerce, 
 and the Egyptians were probably equally enterprising traders. 
 It is very curious that they did not dilute their varnish with 
 essential oil of turpentine, for this was really the substance known 
 to Herodotus and later writers as "oil of cedar," which they 
 used in considerable quantities for embalming purposes. It is 
 equally singular that this was not practised by Theophilus, nor 
 for three or four hundred years after his time, but such is the 
 undoubted fact, and it bears out the hypothesis that the formula, 
 perhaps of immeasurable antiquity, had been found to give 
 satisfactory results and no modification of it was allowed. We 
 do not know that the Egyptians used linseed-oil, or knew it, 
 but we do know that they used linen and cultivated the flax-plant 
 and therefore saved and stored linseed. We also know that 
 they knew and used olive-oil, which is of remote antiquity, and 
 hence must have had oil-presses. We also know that linseed- 
 oil was in early times extracted with an olive-oil press, for 
 Theophilus gives the following directions: 
 
 Formula from Theophilus for Making Linseed-oil. "Take 
 linseed and dry it in a pan, without water, on the fire. Put 
 it in a mortar and pound it to a fine powder. Then, replacing 
 it in a pan and pouring water on it, make it quite hot. After- 
 ward wrap it in a piece of new linen; place it in a press used 
 for extracting the oil of olives, or of walnuts, or of the poppy, 
 and express this in the same manner." 
 
 If the Egyptians had for thousands of years been familiar 
 with linseed and with the oil-press (as they were), it is not 
 unlikely that they had put the two together. Pliny, who wrote 
 
EARLY HISTORY. 23 
 
 about the beginning of the Christian era, says (1. xiv, c. 25): 
 "Resina omnis dissolvitur oleo" oil dissolves all resins. Dios- 
 corides, who was before Pliny, describes walnut- and poppy-oils. 
 Hippocrates, who lived in the fifth century B.C., recommends 
 linseed poultice. Galen, who lived in the second century A.D., 
 says that linseed is in its nature drying. Walnut- and poppy- 
 oils are also drying oils, and one of these may have been used, 
 but there is no reason to think that they were used before linseed, 
 except that they are better suited, especially walnut-oil, to be 
 used for food. Fresh walnut-oil is nearly as good as olive-oil, 
 but it is to be remembered that at the present day in Russia 
 linseed-oil is used as food. 
 
 Use of Varnish by Apelles. Apelles, who lived in the fourth 
 century B.C., was the court-painter of Alexander the Great. 
 Pliny (1. xxxv, c. 18) says of him: "No one was able to imitate 
 one thing, in that he spread the varnish over his completed work 
 so thin that it brought out the brilliancy of the colors by reflection 
 and protected it from dust and dirt." Also Cicero (ad Divers, 
 1. 9, 36) says: "Apelles finished the head of Venus with the 
 highest polish." The picture of Venus was one of his most 
 celebrated works. Praxiteles was a Greek sculptor who lived 
 in the fourth century B.C. and who employed Nicias, a painter, 
 to tint and varnish his statues. 
 
 By Nicias. In book xxxv, ch. 28, Pliny says: "It is Nicias 
 of whom Praxiteles, being asked which of his marble statues he 
 most valued, answered, those to which Nicias had put his hand; 
 so much care he had taken in rubbing them." The word here 
 translated "rubbing" (circumlitioni) has the peculiar meaning 
 of smearing on with a rubbing motion, and the passage indicates 
 that the varnish was applied with the hand and polished by 
 rubbing, in the way described 1400 years later by Theophilus. 
 Protogenes was another Grecian painter, whose picture of 
 Jalysus was his most celebrated work, and it appears from the 
 following passage from Cicero that, like Apelles, he polished 
 his paintings: "And as I believe Apelles and Protogenes saw 
 with grief, the one his Venus, the other his Jalysus, covered 
 
24 TECHNOLOGY OF PAINT AND VARNISH. 
 
 with dirt; so I cannot without extreme distress see so strangely 
 disfigured a man whom I have painted and polished with all 
 the colors of art." (Cic. ad. Att, lib. 2, Epist. 21.) This pas- 
 sage may have suggested the following to Lord Bacon: "The 
 fame of Cicero had not borne her age so well, if it had not been 
 joined with some vanity. Like unto varnish, which makes 
 ceilings not only shine, but last." 
 
 Poetical References to Varnish by Leonidas. In the early 
 part of the third century B.C. there was a Greek poet named 
 Leonidas, who is best known by dedicatory verses and inscrip- 
 tions on works of art. One of these short poems, on a picture 
 of Eros is here given: 
 
 rov "Epwra rls 
 x^S'duroO Z-rjvbs 
 ?ro5' f H0a/0"r<p /cetrcu <TK07r6s, bv Ka6op8.<r0ai 
 irvpl rv\f/6fJLevov. 
 Anthol. Grec., Epig. lib. I, cap. xxvi. 
 
 Translation: 
 
 "Who has polished with the resin of incense this Eros armed with arrows, who 
 
 does not respect Zeus himself? 
 
 At last behold him placed as a mark for Hephaistos, seen to be consumed by 
 fire." 
 
 Another somewhat similar passage, also an inscription on a 
 painting, shows in like manner that varnish was either the 
 medium or the characteristic surface of the picture: 
 
 MiJ /J.e rbv K \i^dyoiO \4j^ve, rov 
 Te/>7r6/ie'OJ' wxioi; rfidtuv odpois, 
 
 Bcuos y<j) vij'/Ji^'Yjs airb yeirovos a 
 "M.OVVOV eirorptivw e/rya 
 
 "EvOev dr' tvKdpirov pe <j>L\i)S eSe^av 
 
 A translation of the beginning of this is as follows and is addressed 
 to the painter: 
 
 " Friend, no more remind me with resin of incense (i.e., varnish) how a depraved 
 youth passed the time in riotous orgies," etc., 
 
EARLY HISTORY. 25 
 
 and goes on to tell how he has adopted good habits, etc. The 
 remainder of the poem indeed is like an order for another picture, 
 showing the youth in good company, laboring in his orchard, 
 interested in the changing seasons. 
 
 Still another Greek verse, on the picture of a maiden, with 
 the same reference to the use of varnish: 
 
 Xi/Sdpou, Xaotrwv 5e/xas, 
 , KO.I IIa0tT7$ virtp \ay6vuv. 
 
 Translation : 
 
 "Maiden, thou hast celebrity from the resin (varnish); to it them owest thy form 
 of the Graces, thy eloquence, and around thy waist the girdle of Venus." 
 
 In all the foregoing the same word (Xifiavov) is used, which has 
 been rendered resin, or resin of incense. It is the word from 
 which comes our word olibanum, which is the name of the resin 
 of frankincense, but was used to denote any or all of the incense- 
 resins, which were used for making the commoner kinds of 
 varnish. It appears to have sometimes been the custom to 
 apply these resins in the 'form of a powder which was then melted 
 by holding a hot iron or a torch near them, after which the sur- 
 face could be polished by rubbing. Eastlake, who appears 
 to have studied this subject carefully, thinks that the pigments 
 used were mixed with melted wax and applied with a brush. 
 When cold, the surface was remelted to produce an apparently 
 enamelled surface. This was enhanced by mixing resin with 
 the wax to harden it, or by adding resin to the surface, which 
 formed a varnish. This was in the case of encaustic painting; 
 distemper painting could be treated somewhat in the same 
 manner, or varnished in the ordinary way. It was evidently 
 possible to get in some such way an extremely high lustre on 
 encaustic (wax) paintings, as is illustrated by the following 
 verse from the Greek anthology: 
 
 "Apea Kal Ha^irjv 6 farypd^os s ptvov dlxov 
 
 'Ex ftvpldos dt /j.o\&v Qateuv, iro\virdfji(paos 
 ^poi>s ffKotrtuv. 
 rivos; 6u5' eVt /cr?pou 
 
26 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Translation : 
 
 "A painter represents Mars and Venus in the middle of a temple. The sun, 
 shining in through the doorway, scatters rays of the most dazzling brilliancy. The 
 painter stands in astonishment and, looking at the two, he wonders if the sun is 
 angry, or wishes to throw his wrath on the inanimate wax." 
 
 Vitruvius on Polishing Varnish. That varnish was polished 
 by rubbing is also indicated by the following from Vitruvius 
 (1. vii, c. 4): "In his vero supra podia, abaxi ex atramento sunt 
 subigendi et poliendi cuneis silaceis, seu miniaceis interpositis." 
 " Among these panels over the balcony the wainscoting is rubbed 
 and polished with varnish, with ochre or minium interposed." 
 
 The use of wax except as a floor-varnish has almost ceased, 
 but with that exception there is nothing in all these passages 
 which indicates any change of importance from the earliest 
 times down to what we may call the historic period of varnish; 
 and if the various practices of using varnishes have been the 
 same, and if all we can learn of the composition of them seems 
 without change, it would seem not unreasonable to suppose that 
 the processes of varnish-making have also been handed down, 
 without important variation, from at least the time when the 
 varnish on the mummy-cases' was made, i.e., about twenty-five 
 hundred years. The most likely criticism is that, as varnishes 
 made now do not last but a few years, it appears that we have 
 lost the art known to the ancients. I reply, we have not lost 
 the knowledge, but we have lost the patience necessary to the 
 use of the most permanent and durable preparations. This 
 will be clearly illustrated in a later chapter. 
 
CHAPTER III. 
 
 VARNISH: ORIGIN OF THE -NAME. 
 
 IN the middle of the third century B.C. Berenice, whose 
 grandfather was a half-brother of Alexander the Great, a very 
 beautiful golden-haired woman, one of whose descendants was 
 the famous Egyptian queen Cleopatra, was Queen of Cyrene 
 and wife of Ptolemy Euergetes, King of Egypt. Not long after 
 her marriage the king, her husband, engaged in a long and 
 highly successful campaign in Asia, during the time of which 
 the queen offered up prayers for his successful return, vowing 
 to sacrifice her beautiful hair on the altar of Venus if the king 
 should come back in safety. This she accordingly did; but 
 the shining and jewelled tresses disappeared during the night 
 from the altar, and it was found by the astronomer Conon that 
 the deities had carried them to heaven, where they form, in the 
 Milky Way, the constellation still known as the Coma Berenices, 
 or Berenice's Hair. The poet Callimachus celebrated them 
 in Greek verse as 
 
 "The consecrated spoils of Berenice's golden head"; 
 
 and Catullus, telling of the rivalry between Venus and Juno, 
 says that 
 
 "The winged messenger came down 
 At her desire, lest Ariadne's crown 
 Should still unrivalled glitter in the skies; 
 And that thy yellow hair, a richer prize, 
 The spoils devoted to the powers divine, 
 Might from the fields of light as brightly shine." 
 
 When to the Greeks was brought from the far-off shores of 
 the unknown Northern Sea the yellow translucent mineral we 
 
 27 
 
28 TECHNOLOGY OF PAINT AND VARNISH. 
 
 know as amber, they likened it to the sacred yellow locks of 
 the beautiful Grecian woman, the first queen in her own right 
 of the Macedonian race, and called it by her name, Berenice, 
 and by this name it was known both to the Greeks and Romans 
 for several centuries. "Amber" was an adjective not infre- 
 quently applied to the hair of fair women. The Emperor Nero, 
 who sometimes affected to be a poet, wrote verses to the amber 
 hair of his empress, Poppcea; in consequence of which, observes 
 Pliny (1. xxxvii, c. 12), amber-colored hair became fashionable 
 in Rome; and before this Ovid (Metamorphoses, 1. xv, 316) 
 said, "Electro similes faciunt auroque capillos " "Her hair 
 was like amber and gold." Because of its beauty, amber has 
 always been a poetic simile. An ancient Persian poet says: 
 
 " But clear as amber, fine as musk, 
 
 Is Love to those who, pilgrim-wise, 
 Walk hand in hand, from dawn to dusk, 
 Each morning nearer Paradise." 
 
 The word Berenice is equivalent to Pheronice, literally meaning 
 "bringing victory." Ph (<) is changed to B in some Greek 
 dialects, even in classic Greek, and B was in some dialects pro- 
 nounced like our V, as it now is by modern Greeks, and as it 
 was in the middle ages. Hence the word Berenice, meaning 
 amber, was often written Verenice in Latin, and when we get 
 down to the twelfth century we find in the Mappae Claviculi 
 the word spelled in the genitive verenicis and vernicis. This is 
 probably the earliest instance of the Latinized word nearly in 
 its modern form, the original nominative vernice being after- 
 ward changed to vernix, when comes our word varnish. The 
 German name for amber is Bernstein, or Berenice's stone, and 
 the Spanish word for varnish is Berniz, nearer to the Greek than 
 our own word, which comes through the later Latin. Veronice, 
 or Verenice, is the common name for amber in the MS. of the 
 middle ages. Eustathius, a twelfth-century editor of Homer, 
 says that the later Greeks called Electron (amber) by the name 
 of Beronice; and Salmasius writes it Berenice and Verenice. In 
 the Lucca MS. (eighth century) Veronica is often mentioned 
 
VARNISH: ORIGIN OF THE NAME. 29 
 
 as an ingredient of liquid varnish, and this latter word, Veronica, 
 is the modern equivalent of the name Berenice. Saint Veronica, 
 however, had nothing to do with Berenice, but perhaps she 
 might be adopted as a patron saint by the varnish-makers. Her 
 sanctity does not appear to be of the highest order, since the 
 observance of her festival is not obligatory. 
 
 Such is the origin of the word varnish. It was originally 
 equivalent to amber, and amber is a type of the highest class 
 of resins used in the art. The early Greek word for amber 
 was elektron, from the verb elko, meaning to draw, because 
 amber when rubbed becomes electrical and draws straws and 
 other light objects to itself, whence also the word electricity. 
 The Arabic and Persian term for amber is Karabe, from Kahruba, 
 meaning straw-stealing, and Buttman states that the word Raf 
 or Rav, meaning to seize, is the name for amber in the north 
 of Germany. 
 
 Salmasius says that the word vernix was misappropriated to 
 mean sandarac, because of the resemblance of that resin to 
 amber. After the sixteenth century the term vernix ceased to- 
 be applied exclusively to the dry resin, and was used, as it is 
 now, to mean the liquid compound. 
 
 Glassa. As has already been mentioned, both Tacitus and 
 Pliny say that the Germans of their time called amber by the 
 name of glessum or glassa, which is supposed to be the original 
 of our word glass. Tacitus believed amber to be the juice of a. 
 tree, because they find insects in it. Thus it is, he says, that in 
 the Orient there are trees from which trickle frankincense and 
 balsam, which made him suppose that there are in the west re- 
 gions and islands where the sun draws from certain trees a sap r 
 which, falling into the sea, is by it thrown up, hardened, on the 
 shore. 
 
 Copal. Another word which is of common use in this connec- 
 tion is copal. This is a comparatively modern word, and is from 
 the language of some of the aborigines of 'Spanish America, con*- 
 monly said to be Mexican, and is said to signify any kind of resin 
 exuding from trees. The earliest writer who mentions copal by 
 
30 TECHNOLOGY OF PAINT AND VARNISH. 
 
 this name as an ingredient of varnishes is probably Fra Fortunato, 
 of Rovigo, the recipes in whose "Secreti," date from 1659 to 
 1711. The next author is Calomino, who gives a recipe for 
 varnish composed of copal dissolved in spirits of turpentine (see 
 the Pharmaceutical Journal, Vol. IV, p. 4). As now used, copal 
 is a generic term, including about all the varnish resins which are 
 commonly combined with oil, and is not sufficiently definite to 
 be used by varnish-makers. Copal varnish is a trade name, 
 usually for a very inferior article made of common rosin, or colo- 
 phony, and containing no copal; somewhat as the word "cafe" 
 is used on the windows of grog-shops. In former times " amber" 
 seems to have been used somewhat in the same way as "copal" 
 now is, but was restricted to the hard' and valuable resins; besides 
 which there always was a specific substance known by that name, 
 being the same that we now call amber, a yellow or red resin from 
 the shores of the Baltic. Amber has almost passed out of use as 
 a varnish-resin. The larger pieces are used for mouthpieces for 
 pipes, and the smaller pieces are, it is said, cemented together to 
 make larger ones. It is said to be difficult to melt, but the writer 
 has not found this to be the case. It does, however, make a dark 
 varnish and appears to be too costly to be much used. The fact 
 that genuine amber, when polished, retains its surface longer than 
 any other resin may indicate that the varnish made from it is of 
 a high degree of permanence. It is commonly so with the other 
 resins. 
 
CHAPTER TV! 
 
 LINSEED-OIL. 
 
 VEGETABLE OILS have, from the earliest times, been extracted 
 from the oil-bearing substance by the aid of a press ; but while this 
 is the most economical and efficient way, as shown by the fact 
 that it is the modern method, it is not the only one. To get an 
 idea of the way processes and practice were handed down, and 
 how independent artists and artisans were of manufactured prod- 
 ucts, each producing for himself all that he needed, thereby being 
 sure of its quality, it may be well to see what was the manner of 
 apprenticeship prescribed by Cennini, who wrote the first treatise 
 on painting which has come down to us, and which describes his 
 own experience in the fourteenth century: 
 
 "Know that you cannot learn to paint in less time than that 
 which I shall name to you. In the first place, you must study 
 drawing for at least one year; then you must remain with a mas- 
 ter at the workshop for the space of six years at least, that you 
 may learn all the parts and members of the art to grind colors, 
 to boil down glues, to grind plaster, to acquire the practise of 
 laying grounds on pictures, to work in relief, and to scrape or 
 smooth the surface, and to gild; afterwards, to practise coloring, 
 to adorn with mordants, paint cloths of gold, and paint on walls, 
 for six years more drawing without intermission on holydays and 
 workdays. And by this means you will acquire great experience. 
 If you do otherwise, you will never attain perfection. There are 
 many who say that you may learn the art without the assistance 
 of a master. Do not believe them; let this book be an example 
 to you, studying it day and night. And if you do not study under 
 
 31 
 
3 2 TECHNOLOGY OF PAINT AND VARNISH. 
 
 some master, you will never be fit for anything, nor will you be 
 able to show your face among the masters." 
 
 Bearing in mind the foregoing, it is interesting to see how oil 
 was prepared in the laboratory of Leonardo da Vinci, the greatest 
 painter of his time, in the fifteenth and sixteenth centuries. The 
 recipe was found in his own handwriting and describes the process 
 of making oil of walnuts, which, on account of its pale color, has 
 always been a favorite with artists. 
 
 Oil-extraction in the Fifteenth Century. "The nuts are cov- 
 ered with a sort of husk or skin, which if you do not remove when 
 you make the oil, the coloring matter of the husk or skin will rise 
 to the surface of your painting and cause it to change. Select the 
 finest nuts, take off the shells, put them into a glass vessel of clean 
 water to soften until you can remove the skin, change the water, 
 and put the nuts into fresh water seven or eight times, until it 
 ceases to be turbid. After some time the nuts will dissolve and 
 become almost like milk. Put them then into a shallow open vessel 
 in the ah* and you will soon see the oil rise to the surface. To 
 remove it in a pure and clean state, take pieces of cotton, like v 
 those used for the wicks of lamps ; let one end rest in the oil and 
 the other drop into a vase or bottle, which is to be placed about 
 the width of two fingers below the dish containing the oil. By 
 degrees the oil will filter itself, and will drop quite clear and 
 limpid into the bottle, and the lees will remain behind. All oils 
 are of themselves quite limpid, but they change color from the 
 manner in which they are extracted." 
 
 The foregoing is a good illustration of the manner in which 
 oils are extracted by water without pressure. It is to be remem- 
 bered that in the most modern practice of oil-pressing it is cus- 
 tomary to moisten the ground seed with water or steam, showing 
 that water seems necessary to start the separation of the oil from 
 the solid part of the seed, probably by swelling and softening the 
 tissues so that the oil can escape. In the multitudinous recipes 
 of the middle ages there are many which show how universal was 
 the belief, or knowledge, that water was essential to the separation 
 or purification of oil. The most common method of purifying 
 
LINSEED-OIL. 33 
 
 linseed-oil consisted in mixing the oil in a large vessel (large in 
 proportion to the amount of oil used) with its own volume, or 
 more, of water. This was heated until the water boiled, which 
 of course helped to mix the oil and water, so that the latter might 
 dissolve out the soluble ingredients of the former. As the water 
 evaporated it was replaced from time to time, and after boiling 
 for one or two or more days the mixture was allowed to settle 
 and the oil poured off. This method was further complicated by 
 the addition of salts of various kinds to the water. 
 
 Separation from Water. When oil is treated in this way part 
 of it is likely to remain as a persistent emulsion with the water. 
 The common way of separating these emulsions is now to add 
 common salt, which makes a brine of the water, and this brine 
 separates easily from the oil; and cloudy oil is easily cleared by 
 filtering it through or shaking it with some soluble saline sub- 
 stance, previously made anhydrous by heating it, which takes out 
 the traces of water which produce the cloudiness. White vitrio 
 (sulphate of zinc) is well suited for this purpose, and all the older 
 recipes which recommend this salt say that it should first be cal- 
 cined. Green vitriol (sulphate of iron) has also been used, but 
 not so much. 
 
 Driers. When zinc sulphate or any such calcined salt is 
 used in this way to remove water, it is literally a drier. It makes 
 the oil dry, in the sense that it frees it from water, and I cannot 
 doubt that it was in this way that zinc sulphate came to be spoken 
 of as a drier. Of course, oil which has in this or any other way 
 been freed from water will oxidize, and in that sense also dry, 
 faster than that which contains water, and so white vitriol and 
 other hygroscopic salts came to be spoken of as driers and con- 
 fused with that other class of driers, of which litharge is a type, 
 which do not absorb water, but cause oil to dry or harden by 
 increasing its chemical activity, a function which the zinc salts 
 (and other similar substances) do not appear to possess in the 
 least degree. Even with the most improved methods a great 
 deal of the freshly pressed oil is turbid with water and wet matter, 
 and is purified by long settling in tanks, followed by filtration. 
 
34 TECHNOLOGY OF PAINT AND VARNISH. 
 
 It is easy to understand that in the laboratory of the painter, 
 where only a pint or two of oil was made at a time, it was easier 
 to clear it rapidly by treating it with a chemically inactive but 
 hygroscopic salt. From this it was but an easy step to regard 
 the saline substance as having a beneficial action on the oil itself. 
 The use of these things, such as the sulphates of iron, zinc, and 
 magnesia, and some other similar substances, has not yet become 
 entirely obsolete, although in the way they are used they are 
 probably absolutely useless. 
 
 " Breaking " of Oil. It has long been known that if freshly 
 made linseed-oil is heated, without the addition of any other 
 substance, to about 400 F., it is decomposed ; a considerable 
 part of the oil appears to be converted into a gelatinous substance. 
 This has been investigated by G. W. Thompson (Journal of the 
 American Chemical Society, 1903), who arrives at the following 
 conclusions : 
 
 Although the amount of gelatinous matter appears large, 
 really but a small proportion, less than a third of one per cent, of 
 the original oil is actually changed; but this is in bulky masses 
 or lumps, swollen by the absorption of a large amount of the 
 unchanged oil, which may be washed out of it by the use of 
 solvents. When this is done and the decomposed oil is analyzed 
 it is found to contain nearly half its weight of mineral matter, 
 consisting of pyrophosphates of lime and magnesia, and amount- 
 ing to practically all the mineral matter present in the original 
 oil. As it has been often claimed that mucilage is contained 
 in raw oil and is the cause of its "breaking," this was carefully 
 looked for in the separated portion, but none was found; neither 
 was there any nitrogenous matter. It seems certain that albu- 
 minous and mucilaginous matters are not contained in clear, 
 well-settled oil. 
 
 The fact that the "break" of linseed-oil is due to the phos- 
 phates it contains explains the well-known method of refining 
 oil for varnish-makers by treatment with a little acid, which 
 decomposes and removes these inorganic constituents. Treat- 
 ment with alkali will also do it ; and oil which has been moderately 
 
LINSEED-OIL. 35 
 
 heated and has had air blown through it will not break. This 
 latter method has been used by the English varnish-makers for 
 many years. 
 
 Linseed-oil is a yellow or sometimes greenish-yellow liquid. 
 It is not known whether it is colored by some foreign matter 
 contained in the seed or whether the pure oily matter has color 
 of its own. Nearly all books which treat of it give recipes for 
 bleaching it so that it shall be colorless, but it may be confidently 
 asserted that no one ever saw any water-white linseed-oil, not 
 so much as an ounce. 
 
 Bleached Oil. "Colorless" linseed-oil is simply that which 
 has been bleached to a pale-yellow color by some of the means 
 known to oil-refiners ; usually about half the color seems to be 
 removed. All colored vegetable oils are bleached when exposed, 
 especially in a thin film, to the sun. When linseed-oil which 
 has been bleached in this way is put in the shade its color comes 
 back, at least to a considerable degree. When it is heated to a 
 high temperature, especially if at the same time agitated with 
 air, so as to promote its oxidation, it is decomposed into a sticky, 
 gelatinous solid, somewhat translucent, dark yellow or brownish 
 yellow in color. This is soluble in caustic soda, making a soap, 
 but a soap very different in its qualities from ordinary linseed- 
 oil soap, showing that the composition of the oil has undergone 
 a radical change. When oil is exposed to the air at the ordinary 
 or at a moderate heat, and especially if in a thin film, or if air 
 is blown through it, it is changed into a tough substance, quite 
 elastic, somewhat like leather, though not nearly so tough. 
 
 Linoxyn. This oxidized oil, or linoxyn, is a very insoluble 
 substance. It resists ordinary solvents and weak acids, but 
 is easily attacked by strong acids and by alkalies in all degrees 
 of strength. When about half oxidized it is soluble in the usual 
 solvents for oil spirits of turpentine, benzine, ether, etc. 
 
 As to historical records, while, for reasons already given, the 
 writer has no doubt of the use of linseed-oil from early times, we 
 have no unmistakable mention of linseed-oil earlier than the 
 fifth century, when it is incidentally mentioned by Aetius, a 
 
36 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Greek medical writer. It is interesting to note that Aetius gives 
 directions for making walnut-oil, saying that it "is prepared 
 like that of almonds, either by pounding or pressing the nuts, 
 or by throwing them, after they had been bruised, into boiling 
 water. The medicinal uses are the same, but it has a use besides 
 these, being employed by gilders or encaustic painters, for it dries 
 and preserves gildings or encaustic paintings for a long time." 
 
 Walnut-oil was not by any means new in his time, however, 
 for it, as well as poppy-oil, is described by Dioscorides five 
 hundred years earlier. The fact that these common things are 
 not mentioned in such historical or literary writings as have 
 come down to us is, therefore, not to be taken as an indication 
 that they were unknown. Dioscorides describes a method of 
 bleaching oils which will bear comparison with anything we 
 do now. 
 
 Dioscorides on Bleaching Oil. "Oil is bleached in this 
 manner: Select it of a light color, and not more than a year 
 old; pour about five gallons into a new earthenware vessel of 
 an open form, place it in the sun, and daily at noon dip and 
 pour back the oil with a ladle, beating up its surface till by con- 
 stant agitation it is thoroughly mixed and made to foam. It is 
 thus to be treated for several days. If it be not sufficiently 
 Heached place it again in the sun, repeating the above operation 
 until it becomes colorless." 
 
 In the "Secreti" of Alessio, prior of the Gesuati of Florence, 
 the author of which was born in 1475, but which contains recipes 
 of earlier date than 1350, are directions for refining oil by washing 
 it with water. 
 
 The use of driers, especially of litharge, is probably of great 
 antiquity. Galen, in the second century, who speaks of the 
 drying character of linseed and hempseed, also says that litharge 
 and white lead are drying in their nature. Marcellus, in the 
 fourth century, gives directions to "put some oil in a new vessel 
 and put it over a moderate fire; then add well-ground litharge, 
 sprinkling it little by little with the hand. Stir it constantly till 
 the oil begins to thicken." 
 
LINSEED-OIL. 37 
 
 Eraclius, who was certainly earlier than Theophilus, since 
 much of his MS. was included by the latter in his writings, 
 speaks of white lead as a drier for linseed-oil and gives the follow- 
 ing directions: "Put a moderate quantity of lime into oil and 
 heat it, continually skimming it; add white lead to it, according 
 to the quantity of oil, and put it in the sun for a month or more, 
 stirring it frequently. And know that the longer it remains in 
 the sun the better it will be. Then strain it and distemper 
 the colors with it." 
 
 Earliest Use of Umber. In the De Mayerne MS. (which 
 will be spoken of later) there is a letter from Joseph Petitot of 
 Geneva, brother of the celebrated enameller, dated 1644, in which 
 it is said that the ordinary drier for drying oils was umber. As 
 the drying of umber is due to manganese, this is probably the 
 earliest mention of manganese as a drier. The De Mayerne MS. 
 also speaks of burning off oil to make it siccative, a practice 
 still followed, especially in making printers' ink. It may be 
 that this latter practice was known to the early varnish-makers, 
 for they constantly speak of boiling oil until it is reduced in 
 volume a third or a half, which might perhaps be done by burn- 
 ing off; while it is, if not impracticable, certainly never attempted 
 in any other way at present. There is good reason for thinking 
 that lead and manganese oxides, used as driers, act by absorbing 
 oxygen from the air, thus making peroxidized compounds, then 
 giving up a portion of this oxygen to the oil, then re-absorbing 
 more oxygen, and so on. Thus a small amount of lead and 
 manganese may serve to oxidize a large amount of oil. 
 
 Manganese Advised by Faraday. It is said on what appears 
 to be good authority that the use of manganese compounds for 
 this purpose was first recommended, and on purely theoretical 
 grounds, by Professor Michael Faraday, because manganese, 
 like lead, exists in two states of oxidation, and readily passes 
 from either of these to the other. 
 
 Cobalt and Nickel Driers; Vanadium. There are but two 
 other metals which possess this property, viz., cobalt and nickel, 
 and the writer of this has found it possible to make most excellent 
 
38 TECHNOLOGY OF PAINT AND VARNISH. 
 
 driers with both these metals; which did not, however, seem 
 to possess any advantages over those made with lead and man- 
 ganese, and as they were more costly they were not made on a 
 commercial scale. It is desired, however, to call especial atten- 
 tion to the fact that cobalt and nickel driers have been made, 
 and are efficient, because it is commonly said in books on the 
 subject that lead and manganese are the only metals which can 
 be used in this way. The writer also made a vanadium com- 
 pound which was a highly efficient drier, but of course its cost 
 prevented its use. The mistaken statement above referred to 
 is to be found even in so excellent a work as that on Drying Oils 
 by L. E. Andes (of Vienna), which can be highly recommended 
 to those seeking detailed information in regard to this class of 
 oils, including many not well known. 
 
 Acetate of lead and borate of manganese are often used, but 
 they are not efficient until they are decomposed by heat and 
 the acid driven off, so that it appears that the same results could 
 be obtained by using oxides or linoleates. These salts (the 
 acetate and borate) are white in color and for that reason appeal 
 to the prejudice of the oil- or varnish-maker, but their value is 
 greatly overestimated. Umber is often used as a drier and, 
 as has been pointed out, its use is of some antiquity; it contains 
 manganese, to which its activity is doubtless due. 
 
 Linseed-oil is frequently adulterated; with a view to the pre- 
 vention of this, the State of New York recently employed Dr. 
 Mcllhiney to investigate the subject, and by his courtesy I am 
 able to insert here a copy of his report. This is the most recent 
 and in my opinion the most valuable paper on linseed-oil, and I 
 feel that I cannot do better than to print it, especially as it has 
 not been heretofore very accessible to the general public. 
 
CHAPTER V. 
 
 LINSEED-OIL. 
 By Dr. PARKER C. MC!LHINEY. 
 
 LINSEED-OIL is the oil obtained from the seeds of the flax- 
 plant, Linum usitatissimum. Formerly the oil used in the United 
 States was obtained principally from Indian and other foreign 
 seed, but of late years the domestic seed has gradually replaced 
 the foreign, although considerable quantities of Calcutta seed 
 are still imported. The oil obtained from Calcutta seed usually 
 commands a higher price, as it is of a light color, and is by some 
 considered superior to that obtained from American seed. Any 
 real superiority of Calcutta oil is, however, difficult to define, 
 and it is likely that prejudice in favor of the imported article 
 has much to do with the preference. Calcutta oil is generally 
 sold raw and is largely consumed by varnish-makers. 
 
 Linseed is a crop which has a very exhausting effect upon 
 the soil, and it is for this reason grown in the United States mostly 
 on the frontier of the agricultural territory. The result of this 
 is that the principal sources of supply for domestic seed are 
 gradually moving farther west and northwest. It is estimated 
 that 13,000,000 to 14,000,000 bushels of flaxseed were grown 
 in the United States in 1898, and that the production in 1899 
 will reach 15,000,000 bushels. The usual yield of oil is in the 
 neighborhood of 2.3 gallons per bushel of seed. 
 
 The methods of extracting the oil are two, by extraction 
 with volatile solvents and by pressing. The extraction method 
 is not, to my knowledge, practised in New York State. To 
 extract the oil by pressing, the seed when it arrives at the mill 
 is first cleaned, then ground to meal in high-speed rolls, and 
 
 39 
 
40 TECHNOLOGY OF PAINT AND VARNISH. 
 
 heated by steam. In some mills the heating is done by steam 
 injected directly into the meal as it runs in a stream into a tub 
 used as a reservoir of hot meal. In other works the heating-tub 
 is steam- jacketed and no free steam is admitted to the meal. 
 From the heating-pan the meal is delivered to a machine which 
 fills it into canvas forms and presses these forms lightly to make 
 them keep their shape sufficiently to handle. They are then 
 placed in hydraulic presses and subjected to high pressure, caus- 
 ing the oil to run out. The oil at this stage contains various 
 foreign matters, called collectively " foots," which have been 
 pressed out with the oil. These are removed by settling, or by 
 filtration through cloth and paper in filter-presses, or by both. 
 The separation of "foots" on storage goes on for a long time, 
 and the oil improves by storage and settling, even after careful 
 filtration. 
 
 The operation of "boiling oil" is one about which great 
 secrecy is observed by the manufacturers. When linseed-oil is 
 heated to a temperature of 300 to 500 F., its drying properties 
 are increased. If salts of lead or of manganese are incorporated 
 into the oil a similar result is produced, and the simplest, and 
 in former times the universal method of increasing the drying 
 properties of linseed-oil, was to heat the oil to near the tempera- 
 ture at which it undergoes destructive distillation, 550 F., or 
 thereabouts, and stir in at the same time oxide of lead, or oxide 
 of manganese, or both. Heating the oil to such a high tempera- 
 ture darkens it very much, and as light-colored oil is often 
 demanded, so that the oil will not discolor pigments suspended 
 in it more than necessary, and as this high heat is wasteful of 
 oil, time, and fuel, it has become the practice to make a "drier" 
 of the metallic oxides by heating them with a small portion of 
 the oil until they are dissolved, and then adding this drier to 
 the main body of the oil maintained at a much lower tempera- 
 ture, usually not much above the boiling-point of water. The 
 result of this process is that there is not so great a loss of oil dur- 
 ing the boiling, and the oil obtained is lighter in color. The 
 use of this method of making boiled by adding to raw oil, at a 
 
LINSEED-OIL. 4r 
 
 comparatively low temperature, a drier made by a separate 
 operation, has induced the majority of makers of boiled oil ta 
 buy their driers from a varnish- manufacturer, who is better 
 equipped, from the nature of his business, to make driers than 
 the linseed-crusher is. The division of labor between the varnish- 
 maker and the linseed-oil manufacturer results in enabling the 
 linseed-crusher to dispense with all apparatus for heating oil 
 to very high temperaturers, and is on this account advantageous, 
 to him. This same division of labor has, however, had the 
 further effect of allowing the manufacturer of driers an oppor- 
 tunity to introduce into them, for his own profit, materials which, 
 the oil-manufacturer who is endeavoring to produce a pure 
 article would not wish to add to his oil. 
 
 It is claimed by the makers of the so-called "bunghole" oil 
 (a simple mixture of raw linseed-oil with drier), and also by the 
 manufacturers of driers to be used in this way, that the oil made 
 by this process is just as good as kettle-boiled oil, that no fraud is 
 intended by the manufacturers of such oil, and that, in fact, 
 it is simply a variety of boiled oil. 
 
 On the other hand it is claimed by the linseed-crushers and 
 others who make boiled oil from linseed-oil and metallic oxides 
 alone, that the only materials which it is necessary to add to a 
 linseed-oil in converting it into boiled oil are the oxides of lead 
 and manganese; that no one who can obtain the proper facilities 
 for making boiled oil, viz., a kettle in which it can be .heated 
 and agitated, finds it necessary to use a drier thinned with benzine 
 or turpentine, and that, in fact, these are in the finished oil simply 
 dilutents detracting from the value of the oil ; that it is not neces- 
 sary to use in the manufacture of drier for making boiled oil- 
 any shellac, kauri-dust, rosin, or rosin-oil, or, in fact, anything- 
 but linseed-oil, lead, and manganese; and finally that the sale 
 as "boiled oil" of oil which contains anything but linseed-oil, 
 lead, and manganese is a fraud and should not be permitted. 
 
 The character of boiled linseed-oil, as it is described in the 
 literature, even in the latest books, does not agree with that of 
 the oil now made in this State. It is described in the literature 
 
42 TECHNOLOGY OF PAINT AND VARNISH 
 
 as being made at a high temperature in the old-fashioned way, 
 whereas little, if any oil is now made in that way. There 
 is a strong prejudice in the minds of most of the users of boiled 
 oil in favor of the old-fashioned "kettle-boiled" oil. Conse- 
 quently the manufacturers are somewhat averse to admitting 
 that their oils are made after the modern fashion, although no 
 advantages can be claimed for the old way. This prejudice in 
 favor of strongly heated oil is so strong that the dark color of 
 the old oil is imitated by many manufacturers by using dark- 
 colored driers, although it is perfectly evident that for use with 
 all light-colored pigments the lighter an oil is in color, other 
 things being equal, the more desirable the oil is. This prejudice 
 seems to be stronger in the East than in the Western States. 
 
 Section i of chapter 412 of the law relating to linseed- or 
 flaxseed-oil prohibits the manufacture or sale as boiled linseed- 
 oil of oil which has not been heated to 225 F. The intention 
 of this provision is undoubtedly to prevent the manufacture of 
 " bunghole " oil, but it is difficult to understand why an oil should 
 be excluded if it is made from proper materials at a lower tem- 
 perature, and still more difficult for an analyst to ascertain the 
 temperature to which the oil has really been heated. No means 
 are known to me by which it is possible to find out whether a 
 sample of boiled linseed-oil has or has not been heated to 225 F. 
 
 The analytical investigation of linseed-oil and its adulterants 
 was carried on with the idea, first, of ascertaining the character 
 of pure linseed-oil sold in New York State by various manu- 
 facturers; secondly, to ascertain what the adulterants commonly 
 used in the State are; and, thirdly, how prevalent the practice 
 of adulteration is. With these ends in view, a series of samples 
 was obtained, in most cases directly from the manufacturers, 
 but partly also from large users of the oil, which are of undoubted 
 commercial purity. Another series of samples was obtained 
 by purchase from smaller dealers. Samples of oils likely to 
 be used as adulterants were obtained from manufacturers or 
 large dealers. 
 
LINSEED-OIL. 43 
 
 TESTS FOR PURITY OF OIL. 
 
 The tests which are valuable particularly in determining 
 the freedom from adulteration are: 
 
 1. Specific gravity. 
 
 2. The action of bromine or iodine on the oil. Hubl and 
 bromine figures. 
 
 3. The percentage of unsaponifiable organic matter. 
 
 4. The amount of alkali required to convert the oil into soap. 
 Kcettstorfer figure. 
 
 5. The amount of alkali required to neutralize the free acids in 
 the oil. Acid figure. 
 
 6. The percentage of insoluble bromine derivatives. 
 
 7. The amount of volatile oil (turpentine and benzine) con- 
 tained in the oil. 
 
 Other tests often applied to linseed-oil are the Maumene* 
 test, which is the measurement of the temperature caused by 
 mixing measured amounts of the oil and of sulphuric acid; the 
 amount of oxygen absorbed by the oil when exposed to the air 
 in thin films, called Livache's test; the index of refraction; and 
 the action on polarized light. 
 
 i. The Specific Gravity. Linseed-oil is heavier than most 
 other oils. Its specific gravity is expressed in terms of water 
 at 4 C. or 15. 5 C., or water may be taken as unity at whatever 
 temperature the determination of specific gravity is made. It 
 is advisable that some standard of temperatures should be set 
 and adhered to in future determinations, as exactness and sim- 
 plicity are above all else necessary in work that may be submitted 
 as evidence in a court of law. It is at all events advisable that 
 even if the actual determination is made at a temperature different 
 from the standard, it should be expressed in terms of water at 
 the standard temperature. Unfortunately many of the recorded 
 determinations do not state either the temperature at which 
 the determination was made, or the temperature at which water 
 is taken as unity. These determinations have consequently 
 
44 TECHNOLOGY OF PAINT AND VARNISH. 
 
 little legal value. I should recommend, as the conditions which 
 combine the greatest ease with the best accord with published 
 data, that the gravity should be determined at i55. C., water 
 at the same temperature being taken as unity. Almost all the 
 determinations of specific gravity given in this report were made 
 under these conditions. 
 
 The specific gravity of linseed-oil may be taken with the 
 greatest accuracy by means of a specific-gravity bottle, the weight 
 of which is determined empty, full of water at 15. 5 C., and 
 filled with the oil to be examined at the same temperature. 
 Another very convenient laboratory method having only slightly 
 inferior accuracy, and the method by which almost all the deter- 
 minations given in this report were obtained, is in application 
 of the principle of Mohr's hydrostatic balance, by using a plummet 
 with the ordinary analytical balance. For rougher work a deli- 
 cate hydrometer may be used. 
 
 The specific gravity of raw linseed-oil is given by Allen's 
 Comm. Org. Anal., 3d ed., vol. 2, part i, p. 147, as generally 
 about .935, but varying from .931 to .937. The temperature 
 is not stated, but it is presumably 15. 5 C. These limits are 
 the same as those set in Benedikt, Analyse der Fette und Wachs- 
 arten, 3. AufL, p. 429, and no oils of undoubted purity which I 
 have examined have fallen outside of these limits. It may, 
 therefore, be stated as an established fact that if an oil has a 
 specific gravity at i5.5 C., water at the same temperature being 
 unity, that is below .931 or above .937, it is not pure raw linseed- 
 oil. 
 
 The lower limit to the specific gravity of boiled linseed-oil 
 may be set at the same point, .931, because a linseed-oil can only 
 become heavier by heating with access of air and the addition of 
 metallic oxides. Oils made with driers containing benzine may 
 have lower specific gravities. The upper limit to the gravity it 
 is difficult and indeed impossible to set, because genuine linseed- 
 oil may be raised to .950 or higher by continued heating, though 
 it is not commonly above .940. 
 
 Expansion by Heat. The change in gravity, with change of 
 
LINSEED-OIL. 45 
 
 temperature, of linseed-oil, and of some other oils, has been de- 
 termined by Allen, Comm. Org. Anal., 3d ed., vol. 2, part i, 
 p. 33, and the following" are some of his results: 
 
 XT A e r\-t Correction for 
 
 Nature of Oil. f0 c 
 
 Linseed ................................ 000649 
 
 Menhaden ............................. 000654 
 
 Cottonseed ............................. 000629 
 
 Rape .................................. 000620 
 
 According to the results obtained by Saussure, the coefficient 
 of expansion of linseed-oil is not uniform between 12 C. and 94" 
 C. He records the following results (Benedikt, p. 428) : 
 
 Temperature. 
 
 12 C ..................................... 939 
 
 25 C ..................................... 930 
 
 50 C ..................................... 921 
 
 94 C ..................................... 881 
 
 Calculating from these results we obtain, as the variation for 
 i C., between 12 C. and 25 C., .000692; between 25 C. and 
 50 C., .000360; and between 50 C. and 94 C., .000909. It 
 will be seen from the table giving the results of determinations 
 of specific gravity at different temperatures that I do not find in 
 the oils examined a similar change in the rate of expansion. The 
 averages of the figures obtained with raw oils, Nos. 52 and 73, 
 and boiled oil, No. 7 2 > show that the change in specific gravity 
 for i C., between i5.5 C. and 28 C., was .000654; between 
 28 C. and 100 C., .000720; and between i5.5 C. and 100 C., 
 .000712. 
 
 A low specific gravity in an oil under examination might be 
 caused by the presence of (i) turpentine or benzine (indicated 
 also by odor); (2) heavier petroleum-oils; (3) corn- or cottonseed- 
 oils. 
 
 A high specific gravity would point to (i) rosin or other resin; 
 (2) rosin-oil; (3) excessive heating or unusual addition of me- 
 tallic oxides. 
 
46 TECHNOLOGY OF PAINT AND VARNISH. 
 
 2. The Action of Bromine or Iodine on the Oil. Linseed-oil 
 is largely composed of constituents which are unsaturated, and 
 which can, therefore, combine by direct addition with 2, 4, or 6 
 atoms of bromine or iodine. Of the adulterants of linseed-oil, 
 mineral and rosin oils and rosin itself possess this power only to 
 a slight degree, and none of the other adulterants except men- 
 haden-oil possess it in as high a degree as linseed-oil. Besides 
 the principal action of bromine or iodine upon linseed-oil, i.e., 
 direct addition of halogen, another action takes place by which 
 one half of the halogen which disappears enters into combination 
 with the oil, and the other half combines with hydrogen which 
 'the first half has replaced in the oil. 
 
 The substitution of bromine or iodine for hydrogen goes on to 
 only a slight extent with seed-oils and with glycerides in general, 
 but with .rosin, rosin-oil, and mineral oils, the case is very differ- 
 ent. It has been proved by the author that when bromine acts 
 upon rosin and upon rosin-oil, although a large amount of bromine 
 is changed from the free into the combined state, almost all of the 
 bromine is taken up by the rosin or oil by substitution, and not 
 by addition, and in the case of ordinary American mineral oils, 
 that taken up by substitution is a large proportion of the total 
 absorption. 
 
 The process in most common use for determining the percent- 
 age of halogen absorbed by oils is known as the Hiibl process; 
 and though, by its use, valuable indications as to the purity and 
 value of linseed-oil are obtained, it unfortunately does not dis- 
 tinguish between the power of the oil to absorb halogen by addi- 
 tion and the power it likewise possesses of absorbing halogen by 
 substitution. The Hiibl process, on this account, fails to dis- 
 criminate closely between rosin, which is one of the likeliest con- 
 stituents of a linseed-oil substitute, and linseed-oil itself, as the 
 Hiibl figures for the two substances are not very different. 
 
 A process described by the author (J. Amer. Chem. Soc., 16, 
 56), similar to one used previously by Allen for testing shale-oils, 
 distinguishes between addition and substitution, and by its use 
 the presence of any notable amount of rosin, rosin-oil, or mineral 
 
LIN SEED -OIL. 47 
 
 oil can be detected with a considerable degree of accuracy, and 
 a fair idea formed of the character of the adulterant. 
 
 Hiibl Process. The Hiibl process is one of the best-known 
 methods of fat analysis; the method by which the Hiibl figures 
 were obtained for this report was as follows : 
 
 A solution of 25 grams of iodine and 30 grams of mercuric 
 chloride in one liter of alcohol is allowed to stand, after making, 
 for twenty-four hours in the dark before using. Two hundred 
 milligrams or thereabout of the oil to be analyzed is weighed into 
 a glass-stoppered bottle, 10 cc. of chloroform added to dissolve 
 the oil, and 25 cc. of the iodine solution added. If the solution, 
 when shaken to mix the chloroform and alcoholic liquid, does not 
 become clear, 5 cc. more of chloroform is added. The bottle is 
 then allowed to remain in the dark eighteen hours, and at the end 
 of that time a solution of potassium iodide is added, and the free 
 iodine in the solution titrated with tenth-normal sodium thiosul- 
 phate. Twenty-five cubic centimeters of the same iodine solution 
 which has been placed in a similar bottle and allowed to stand 
 with the test is titrated at the same time with thiosulphate, and 
 the difference between the two titrations gives the amount of 
 iodine absorbed by the oil. Full discussions of the process are 
 given in Benedikt, Analyse der Fette und Wachsarten, and in 
 Allen, Commercial Organic Analysis, Lewkowitsch, Oils, Fats, 
 and Waxes, and Gill, Oil Analysis. 
 
 Mcllhiney's Method with Bromine. The bromine figures were 
 obtained by a modification of the author's original method. The 
 method actually used was as follows: 
 
 About 200 milligrams of the oil was placed in a dry glass- 
 stoppered bottle, 10 cc. of carbon tetrachloride added to dissolve 
 the oil, and then 20 cc. of third-normal bromine in carbon tetra- 
 chloride run in from a pipette. Another pipetteful is run into 
 another similar bottle. It is convenient, but not absolutely neces- 
 sary, that both bottles should now be cooled by immersing them 
 in cracked ice. This causes the formation of a partial vacuum in 
 the bottle. The bromine need not be allowed to react with the 
 oil for more than a few minutes, as the reaction between them is 
 
48 TECHNOLOGY OF PAINT AND VARNISH, 
 
 nearly instantaneous. Twenty-five cubic centimeters of a neutral 
 10 per cent, solution of potassium iodide is introduced into each 
 bottle by slipping a piece of rubber tubing of suitable size over 
 the lip of the bottle, pouring the iodine solution into the well thus 
 formed, and shifting the stopper slightly so as to allow the solution 
 to be sucked into the bottle, or, if the bottle has not been cooled, 
 to cause the air as it escapes from the interior to be washed by 
 bubbling through the potassium iodide solution. This method of 
 introducing the iodide solution effectually prevents the loss of any 
 bromine or hydrobromic acid. As soon as the iodide solution has 
 been introduced, the bottle is shaken, and preferably set into the 
 ice for a couple of minutes more, so that there may be no loss of 
 drops of the solution when the stopper is opened, caused by a 
 slight pressure inside the bottle. The reaction between the bro- 
 mine and the iodide solution causes some heat and consequent 
 pressure. The free iodine is now titrated with neutral tenth- 
 normal sodium thiosulphate, using as little starch as possible as 
 indicator. At the end of this titration 5 cc. of a neutral 2 per cent, 
 solution of potassium iodate and a little more starch solution are 
 added and the iodine liberated, on account of the hydrobromic 
 acid produced in the original reaction of bromine on the oil, 
 titrated with thiosulphate. From the figures so obtained the 
 total percentage of bromine which has disappeared is calculated, 
 and the percentage of bromine found as hydrobromic acid, called 
 the "Bromine Substitution Figure," is also calculated, while from 
 these two the " Bromine Addition Figure" is obtained by sub- 
 tracting twice the bromine substitution figure from the total 
 bromine absorption. A consideration of the figures submitted in 
 the table will show that if an oil contains rosin, rosin-oil, or min- 
 eral oil, the fact will be brought out by this process, and an indi- 
 cation given by the figures so obtained as to which one is present. 
 If the bromine substitution figure is normal, the absence of more 
 than a very small quantity of turpentine, benzine, rosin, or rosin- 
 oil is assured. The process can be carried out in the time neces- 
 sary for weighing and titrations, as the standard solution, unlike 
 the Hiibl solution, does not deteriorate on keeping, if tightly 
 
LINSEED-OIL. 49 
 
 closed, so that it is always ready for immediate 'use, and there is 
 no waiting for some hours for the reagents to act upon the oil, as 
 in the Hiibl process, for in this case the reaction takes place im- 
 mediately. 
 
 It will be seen from the table of results that the Bromine Addi- 
 tion Figure of linseed-oil lies ordinarily between 100 and no. 
 The low figures of No. i and No. 2 are to be accounted for by 
 the fact that the samples are several years old, and it is well 
 known that keeping lowers the halogen figures of linseed-oil. 
 
 A low Addition Figure may also be caused by the presence of 
 rosin, rosin-oil, benzine, or mineral oils, which have figures usually 
 below 15; by the presence of some other seed-oil, the commonest 
 of this class being corn- and cottonseed-oils, having figures in 
 the neighborhood of 73 and 63 respectively; or by the oil, in 
 case it is a boiled oil, having been boiled in the old-fashioned 
 way at a high temperature. 
 
 If the Addition Figure is very much higher than no, it will 
 be found that the oil contains turpentine, as all other foreign 
 materials added have lower figures than linseed-oil. 
 
 The Bromine Substitution Figure of genuine linseed-oil is 
 commonly about 3. A much higher figure would point to tur- 
 pentine, rosin, or rosin-oil, which give figures from 20 to 90 ; to 
 the presence of some petroleum product, as benzine, having a 
 figure in the neighborhood of 15, or a heavier petroleum-oil, 
 which may have as low a figure as linseed, or may be much higher; 
 or to the presence of mineral acid in the oil, which may be allowed 
 for by a separate determination of its amount, as described under 
 the determination of the Acid Figure. 
 
 The Hiibl figure of raw linseed-oil is given by Benedikt from 
 148.8 to 183.4. Boiled oil, according to the same author, may 
 give figures below 100. Allen gives the figures for raw oil between 
 170 and 181. Rowland Williams states that a very large number 
 of raw linseed-oils examined by him almost all gave figures 
 above 180. The figure is reduced by keeping. From the table 
 of results obtained upon the oils examined it will be seen that 
 the figure of pure oil is commonly in the neighborhood of 178. 
 
50 TECHNOLOGY OF PAINT AND VARNISH. 
 
 It is a noteworthy fact that both the Hubl and the Bromine 
 Addition Figures are practically the same for boiled oil as now 
 made as for raw oil, whereas boiled oil made by the old process at 
 a high temperature gave distinctly low T er figures on account of the 
 effects of the high heat upon the oil. 
 
 In order to facilitate comparison between the Hubl and the 
 bromine figures of the oils examined, the amount of bromine 
 equivalent to the iodine absorbed as expressed by the Hubl 
 figure has been calculated, and by dividing this result by the 
 Bromine Addition Figure a figure was obtained for each oil 
 which is intended to express, by the amount it exceeds i.ooo, 
 the amount of substitution of iodine which has gone on in the 
 Hubl iodine absorption. For example, if the figure obtained 
 for an oil by the calculation described is found to be 1.075, ^ 
 indicates that the Hubl figure is in that case 7.5 per cent, higher 
 than the true iodine figure which should express the iodine absorp- 
 tion by addition. 
 
 The Hubl figures of a number of the oils received last were 
 not determined, because it did not appear that the determina- 
 tions would add any information to that given more fully by the 
 bromine figures. 
 
 It is not believed that the Bromine Addition Figure is sensibly 
 affected by the length of time that the oil is allowed to remain 
 in contact with bromine, but the Bromine Substitution Figure 
 probably is. The effect of the difference between five minutes' 
 and thirty minutes' contact does not appear, however, to be 
 marked, unless the substitution figure is very high, as in the case 
 of pure resin or turpentine. The results, reported were obtained 
 by about fifteen minutes contact. 
 
 In carrying out either the Hubl or the bromine process upon 
 oils it is necessary that an excess of iodine or bromine should be 
 used amounting to as much as the oil absorbs. Many iodine 
 figures on record are too low because this precaution was not 
 attended to. 
 
 It is believed that more information is to be obtained as to the 
 character of a sample of linseed-oil by determining the bromine 
 
LINSEED-OIL, 51 
 
 figures than by any other single test. In the case of an oil of 
 unknown character it would in most cases be advisable to apply 
 this test first to it. 
 
 3. The Percentage of Unsaponifiable Organic Matter. Lin- 
 seed-oil, being composed almost entirely of fatty matter of the 
 ordinary type, compounds of fatty acids with glycerin, gives 
 only a small percentage of material which cannot be saponified. 
 The amount to be found in raw linseed-oil has been investigated 
 by Thompson and Ballantyne (J. Soc. Chem. Ind., 1891, 10, 336), 
 who find amounts varying from). 1.09 to 1.28 per cent, in oil from 
 various sources, and by Rowland Williams (J. Soc. Chem. Ind., 
 1898, 17, 305), who finds that it varies from 0.8 to 1.3 per cent. 
 Williams, loc. cit., has also determined the amount of unsaponi- 
 fiable matter in boiled oil, and finds that the amount is nearly 
 twice as great as in raw oil, his figures for boiled oil being 1.3 to 
 2.3 percent.; being usually about 2 per cent. Williams regards 
 any oil with a percentage of unsaponifiable matter higher than 2.5 
 as adulterated. His statements refer to oil which has been boiled 
 at a high temperature, and the boiled oils for sale in New York 
 State are apparently all made at too low a temperature to cause 
 any increase in the amount of unsaponifiable matter contained, 
 with the exception of the oil in the drier. In view of these facts, 
 2.5 per cent, would be a reasonable limit to the amount of 
 unsaponifiable matter in linseed-oil. This is so well established 
 that it was not thought advisable to make this determination 
 upon the pure oils examined. 
 
 It may be noted that in case an oil is found to contain 
 unsaponifiable matter in excessive amount, the evidence which 
 can be furnished the prosecution may be made of the most con- 
 clusive character, for the adulterant can be actually separated 
 from the genuine linseed-oil and exhibited, whereas, in the case 
 of some other adulterants, the evidence, though it may be con- 
 clusive, is of a character requiring more demonstration to one 
 unfamiliar with the scientific examination of oils. The adul- 
 terants whose presence can in this way be demonstrated by 
 actual separation are mineral oil and usually rosin-oil. Benzine 
 

 52 TECHNOLOGY OF PAINT AND VARNISH. 
 
 and turpentine, although unsaponifiable, are not found with the 
 unsaponifiable matter, as, from the nature of the methods of 
 analysis, only materials that are practically non-volatile are 
 counted as unsaponifiable. They are easily separated and 
 determined, however, as volatile oil. 
 
 There are several methods for determining the percentage of 
 unsaponifiable material, proposed by different experimenters. 
 Some treat the oil with alcoholic or aqueous solution of potash 
 or soda, evaporate off the alcohol or water, and treat the dried 
 soap with petroleum ether or chloroform to dissolve the unsapon- 
 ifiable portion. Other experimenters, after saponifying the 
 soap with alcoholic solution of potash and evaporating off the 
 alcohol, dissolve the resulting soap in water and agitate the solu- 
 tion with ether several times to remove from the soap solution 
 the unsapon fiable matter which it holds in suspension. 
 
 A method which can with safety be recommended for deter- 
 mining unsaponifiable matter in linseed-oil is substantially that 
 described in Allen, Comm. Org. Anal, 3d ed., vol. 2, part i, 
 p. 112. A quantity of oil varying from i to 10 grams, depending 
 upon the amount of unsaponifiable matter present, is boiled for 
 two hours, with frequent shaking, with excess of alcoholic solu- 
 tion of caustic potash, in a flask provided with a return condenser. 
 The alcohol is then distilled off until only a small quantity remains. 
 The soap is then dissolved in water, using 75 to 100 cc. for the 
 purpose, transferred to a tapped separator, and 50 cc. of ether 
 added. The liquids are then mixed by shaking and allowed to 
 settle. The aqueous liquid is then drawn off, the ethereal layer 
 washed with a few cubic centimeters of water to which a little 
 caustic potash has been added, and poured into a tared flask. 
 The soap solution is then returned to the separator and extracted 
 with another 50 cc. of ether in the same way. The combined 
 ethereal solutions are evaporated on the water-bath, and when 
 the ether has been completely removed the flask now containing 
 the unsaponifiable matter is weighed. If the percentage of 
 unsaponifiable matter found is large, it may be advisable to 
 repeat the process of saponification and extraction upon the 
 
LIN SEED -OIL. 53 
 
 unsaponifiable matter, in order to be quite certain that no 
 unsaponifiable oil has escaped the action of the alkali. 
 
 Determination of Mineral Oil. The mineral oil may be 
 separated from the rosin-oil in the unsaponifiable material found 
 in the saponificatiqn process by the method suggested by the 
 author in the Jour. Amer. Chem. Soc., 16, 385. 
 
 Fifty cubic centimeters of nitric acid of 1.2 sp. gr. are heated 
 to boiling in a flask of 700 cc. capacity. The source of heat is 
 removed, and 5 grams of the oil to be analyzed added. The 
 flask is then heated on the water-bath, with frequent shaking, 
 for fifteen to twenty minutes, and about 400 cc. of cold water 
 added. After the liquid has become entirely cold 50 cc. of 
 petroleum ether are added and the flask is agitated. The oil 
 which remains unacted upon dissolves in the ether, while the 
 rosin remains in suspension. The liquid is poured into a tapped 
 separator, leaving the lumps of solid rosin as far as possible 
 behind in the flask. After settling, the aqueous liquid is drawn 
 off and the ethereal layer poured into a tared flask. Another 
 portion of petroleum ether is added to the rosin remaining in the 
 flask, and allowed to act upon it for about ten minutes, when 
 it is added to that in the tared flask. After distilling off the 
 ether, the oil is weighed. Mineral oils lose about 10 per cent, 
 in this way, and hence the weight of oil found must be divided 
 by 0.9 in order to find the amount present in the sample analyzed. 
 
 Allen found mineral oils to lose 10 to 12 per cent, on treatment ' 
 with nitric acid. (Pharm. Jour., 3d series, n, 266.) 
 
 Rosin-oil, though principally composed of hydrocarbons, may 
 contain some unchanged rosin which is saponifiable, and conse- 
 quently, in case rosin-oil is present, the amount of unsaponifiable 
 matter which it furnishes is less than the total amount of rosin- 
 oil present. The proportion between that found and the amount 
 present will vary according to the way in which the oil was manu- 
 factured, and its consequent contents in unchanged rosin. Ordi- 
 narily the amount of saponifiable matter found due to rosin-oil 
 is likely to be about nine-tenths of that present. 
 
 The amount of unsaponifiable matter found in the other 
 
54 TECHNOLOGY OF PAINT AND VARNISH. 
 
 animal and vegetable oils used as linseed-oil adulterants is 
 approximately the same as that found in linseed-oil itself; hence 
 the process does not furnish any clue to corn-, cottonseed-, or 
 menhaden-oils, if they are present. 
 
 Petroleum-oils may be used in adulterating linseed-oil, which 
 are just on the border-line between volatile and practically non- 
 volatile oils. Such oil as, for example, kerosene would partly 
 distil off with the alcohol in removing it after saponification, 
 while the rest of it would remain to be extracted with ether from 
 the aqueous soap solution, and be weighed as unsaponifiable 
 matter. It might easily happen in such a case that the proportion 
 of the partly volatile oil which would be obtained. by distillation 
 with steam in the determination of volatile oil would be a dif- 
 ferent one from the proportion removed from the saponified 
 oil in distilling off the alcohol in the determination of unsaponi- 
 fiable matters, and that the sum of the "volatile oil" and of 
 the "unsaponifiable matter" would be more or less than the 
 true total amount of adulterant added. In such a case it would 
 be advisable to use for the determination of unsaponifiable matter 
 a portion of the residue from the determination of volatile oil. 
 V 4. The Amount of Alkali Required to Convert the Oil into 
 
 Soap. Koettstorfer Figure. This determination serves in the 
 analysis of linseed-oil as an indication of the presence or absence 
 of unsaponifiable matter, whether volatile or not. Its indications 
 " are not as valuable for this purpose as an actual determination 
 of the unsaponifiable matter itself, but they are more readily 
 obtained. The determination is made by the well-known 
 Koettstorfer process. About 2.5 grams of the oil is weighed 
 into a flask, 25 cc. of half-normal alcoholic solution of caustic 
 potash added and the liquid boiled on the water-bath with 
 a return condenser, with frequent shaking, for about two hours. 
 The liquid in the flask is then titrated with half-normal hydro- 
 chloric acid, using phenolphthalein as indicator. Twenty-five 
 cubic centimeters of the same alcoholic caustic potash is titrated 
 at the same time, and the difference between the two titrations 
 gives the alkali used in saponifying the oil, and when calculated 
 
LINSEED-OIL. 55 
 
 in milligrams of potassium hydroxide to a gram of oil it is called 
 the " Koettstorfer Figure." 
 
 The Koettstorfer Figure of raw linseed-oil is given by Benedikt 
 from 187.6 to 195.2, and by Allen from 187.4 to 195.2. Bene- 
 dikt's figures for boiled oil are from 180 to 190, and Allen's figure, 
 calculated from his " Saponification Equivalent," is 188. Bene- 
 dikt's figures are on the authority of Filsinger, Chem. Zeit., 1894, 
 1 8, 1867, and evidently apply to old-fashioned, strongly heated 
 boiled oil. Both the exposure to high heat and the introduction 
 of manganese and lead soaps of linseed-oil in the drier tend to 
 reduce the Koettstorfer figure. Of the two, exposure to high heat 
 for a long time, as in the old-fashioned boiling process, reduces it 
 far more than the introduction of the small percentage of lead 
 and manganese soaps as used in practice. The boiled oils now 
 for sale in this State have, as will be seen from the table, almost 
 as high figures as the raw oils. It may fairly be demanded of a 
 raw oil that its figure shall not be lower than 187, and of a boiled 
 oil not lower than 186. 
 
 A low figure indicates the presence of mineral oil, having a 
 figure below 10; of rosin-oil, having a figure below 20; or of ben- 
 zine or turpentine, of both of which the figures are practically o.o. 
 Pure hydrocarbons give a Koettstorfer figure of o.o, but mineral 
 oils usually contain traces either of mineral acid from the refining 
 process, or of organic acids from oxidation by the air, and rosin- 
 oils contain some unchanged rosin, which accounts for the Kcetts- 
 torfer figures. 
 
 5. The Amount of Alkali Required to Neutralize the Free 
 Acids in the Oil. Acid Figure. Perfectly pure linseed-oil con- 
 tains only a very small percentage of free acids, while rosin is com- 
 posed principally of free acids, and rosin-oil usually contains a 
 notable proportion of free rosin. Therefore, the free acids in an 
 oil which contains rosin will neutralize a larger proportion of alkali 
 than those in pure linseed-oil. On keeping, the amount of free 
 acid is likely to increase somewhat. The free acid found may be 
 partly due to mineral acid used in refining the oil. The amount 
 of mineral acid may be separately determined by boiling for some 
 
56 TECHNOLOGY OF PAINT AND VARNISH. 
 
 
 
 time a weighed portion of the oil with water, cooling the mixture, 
 adding neutral potassium iodide and iodate, and titrating the lib- 
 erated iodine in the aqueous solution with standard sodium thio- 
 sulphate. After deducting from the total percentage of potash 
 required to neutralize the total free acid the percentage required for 
 the mineral acid, the percentage required by the free organic acid 
 is found, which, in the case of linseed-oil, are almost certain to 
 be either the normal fatty acids from the linseed-oils or a com- 
 bination of these with rosin acids. 
 
 The method of determining free acids is to weigh 5 to 10 grams 
 of the oil in a flask, add about 50 cc. of alcohol, which is neutral 
 to phenolphthalein, heat on the water-bath till the alcohol boils, 
 shake well, and titrate with half -normal alkali. The results of 
 the titration are expressed in milligrams of potassium hydroxide 
 required per gram of oil, and the result is called the "Acid 
 Figure." 
 
 Benedikt gives as the limits observed by Nordlinger, in exam- 
 ining ten samples of linseed-oil, acidities from .41 to 4.19 percent, 
 of oleic acid, corresponding to acid figures from .9 to 8.3. Mills 
 allows a maximum figure of 10.0. As will be seen from the figures 
 contained in the table, raw linseed-oil will usually give an acid 
 figure in the neighborhood of 3.0. The figure of oil No. i, though 
 pure, is 7.1, due, no doubt, to the fact that it is several years old. 
 The figures of boiled oil are slightly higher, due probably to the 
 production of a small quantity of some acid body by the action 
 of heat on the oil. The figure of boiled oil will usually be below 
 5, but is more uncertain than that of raw oil. A figure higher 
 than 10.0 will almost certainly be found due to the presence of 
 rosin. The acid figure of rosin is variously given by Benedikt, 
 Williams, and Schmidt & Erban, from 145.5 to 179.2. Samples 
 examined by the author (Jour. Amer. Chem. Soc., 16, 275) gave 
 figures from 155.7 to 168.5. Fortunately rosin is also indicated 
 by a high Bromine Substitution Figure and a low Bromine Addi- 
 tion Figure, and if all three point to rosin, it is probably there, 
 but the safest course is the actual isolation of the rosin by Twit- 
 chell's or Cladding's process. 
 
LIN SEED -OIL. 57 
 
 6. The Percentage of Insoluble Bromine Derivatives. This 
 determination is proposed by Hehner and Mitchell (Analyst, Dec., 
 1898, vol. 23, p. 310). It depends upon the fact that linseed-oil 
 gives, when dissolved in ether and treated with bromine, com- 
 pounds of glycerides and bromine which are insoluble in the 
 ether, while oil containing glycerides of oleic acid only, and even 
 semi-drying oils like cottonseed- and corn-oils, give soluble com- 
 pounds. Hehner and Mitchell obtain the following percentages 
 of insoluble bromine compounds from different oils : 
 
 Q.J Per Cent, of Insoluble 
 
 Bromine Compounds. 
 
 Linseed-oil 23 . 86 to 25 . 8 
 
 Poppy-oil o.o 
 
 Corn-oil o.o 
 
 Cottonseed-oil o.o 
 
 Olive-oil o.o 
 
 Almond-oil o.o 
 
 Rapeseed-oil o.o 
 
 Whale-oil 25.0 
 
 Cod-oil 35 . 5 
 
 Cod-liver oil 42.9 
 
 Shark-oil 22.0 
 
 The process, which seems to be a valuable one in detecting 
 adulterations of linseed-oil with other seed-oils, was not pub- 
 lished until late in the progress of this investigation, and it was 
 impossible to carry on all the experiments with it that it deserves. 
 It has seemed inadvisable, therefore, to present in full the results 
 obtained. Two samples of raw linseed-, six samples of boiled 
 linseed-, two of corn-, and one of cottonseed-oil gave results 
 agreeing substantially with those of Hehner and Mitchell. Two 
 samples of mineral oil, one light and one heavy, one sample of 
 rosin-oil, and one sample of turpentine failed to give any precipi- 
 tate of insoluble bromine derivatives. 
 
 7. The Percentage of Volatile Oil. The presence of even a 
 small percentage of turpentine in linseed-oil is distinctly indicated 
 by the odor of the oil when placed in a vessel which it about half 
 
$8 TECHNOLOGY OF PAINT AND VARNISH. 
 
 fills, the vessel closed, and heated in boiling water for a few min- 
 utes. The smell of turpentine will then be noticed en opening 
 the vessel. Benzine is indicated, though not quite so distinctly, 
 in the same way. 
 
 To determine the amount present, a convenient quantity, say 
 300 grams, is heated by means of a paraffin- or air-bath to about 
 130 C., in a flask provided with an outlet-tube for vapors, an 
 inlet-tube reaching nearly to the bottom of the vessel, and a ther- 
 mometer inserted into the oil. When the oil has reached the 
 desired temperature a current of dry steam is passed through the 
 oil and the vapors condensed in a Liebig condenser. The distil- 
 late will separate into a lower layer of water and an upper layer 
 of volatile oil, which is separated and measured or weighed. The 
 aqueous part of the distillate will inevitably carry with it a small 
 quantity of volatile oil, but the quantity is very small. The 
 amount of turpentine either dissolved or permanently held in 
 suspension by water was found in one experiment made by the 
 author (Jour. Amer. Chem. Soc., 16, 273) to amount to 0.300 gram 
 in 90 cc. of water. 
 
 A separation of the benzine and turpentine in the volatile oil 
 found is best effected by the method of Burton (Amer. Chem. J., 
 12, 102), which depends upon the difference between the action of 
 fuming nitric acid upon benzine and upon turpentine, the former 
 remaining practically unattacked, while the latter is strongly acted 
 upon and converted into bodies soluble in hot water. The method 
 may be described as follows: A measured quantity of the mixture 
 to be separated is allowed to drop slowly into 300 c.c of fuming 
 nitric acid contained in a flask of 750 cc. capacity, provided with 
 a return condenser and immersed in cold water. A violent reac- 
 tion takes place as each drop of oil strikes the acid, and the flask 
 should be shaken occasionally. When all the oil has been added 
 the flask is allowed to stand till all action is over. The contents 
 of the flask are then poured into a separat ing-funnel and treated 
 with successive portions of hot water; the products of the action 
 of the acid on the turpentine are in this way removed, leaving the 
 petroleum oil to be separated and measured. 
 
LINSEED-OIL. 59 
 
 The Maumene Test. When oils are mixed with concentrated 
 sulphuric acid the mixture becomes hot, and the rise of tem- 
 perature varies with the nature of the oil. The chemistry of the 
 process is but slightly understood. Non-drying oils do not give 
 as great a rise as drying oils, and consequently linseed-oil gives 
 a greater rise than any of its adulterants, except, unfortunately, 
 menhaden-oil. The behavior with sulphuric acid is similar to the 
 behavior with bromine and iodine, so that no more information 
 is gained from the rise in temperature than is obtained by deter- 
 mining the percentage of halogen absorbed, except in the case of 
 adulteration with menhaden-oil. 
 
 The test which is known as Maumene^s test and which is fully 
 described in Benedikt, Analyse der Fette, and in Allen, Comm. 
 Org. Anal., vol. 2, is carried out by mixing 50 cc. of the oil to 
 be examined with 10 cc. of strong sulphuric acid. The reaction 
 with linseed-oil and with some other oils is so violent that the oil 
 must be diluted with some more inert oil, or the mixture will froth 
 over. The rise in temperature is observed by a thermometer used 
 to stir the mixture, and the vessel in which the experiment is car- 
 ried on is protected from rapid cooling by setting it inside another 
 larger vessel, usually with cotton wool between. The amount of 
 heat abstracted by the vessel itself depends upon its mass and 
 material, and the amount of loss by radiation is dependent upon 
 a variety of circumstances. Consequently the results obtained by 
 different observers with different apparatus have varied with the 
 same oil, and each apparatus must be standardized by the observer 
 by testing with a number of oils of known purity, or else by adopt- 
 ing the suggestion of Thomson and Ballantyne (J. Soc. Chem. Ind., 
 1891, 10, 233), and expressing the results in terms of rise of tem- 
 perature produced by substituting an equal volume of water for 
 oil, the results obtained with water being taken as 100. As stated 
 above, the Maumene figure is usually higher the higher the halogen 
 absorption. In the case of menhaden-oil, however, and perhaps 
 other fish-oils, the Maumene figure is higher than would corre- 
 spond with its iodine or bromine absorption. A sample having a 
 bromine addition figure of 95, as against linseed-oil, which would 
 
60 TECHNOLOGY OF PAINT AND VARNISH. 
 
 have a figure usually about 102, would give a Maumene figure 
 higher than that of the linseed-oil. Thomson and Ballantyne find 
 that the specific rise of temperature of four samples of linseed-oil 
 which they examined varied from 270 to 349, while the corre- 
 sponding figure for a sample of menhaden-oil was 306. Allen 
 found the rise of temperature with sulphuric acid to be 104 to in 
 in the case of linseed-oil, and 126 in the case of menhaden-oil. 
 
 It will be seen from these facts that if an oil is found to give 
 a distinctly lower bromine addition figure, and at the same time a 
 Maumene figure distinctly higher than specimens of pure linseed- 
 oil tested in the same apparatus, very strong evidence of the pres- 
 ence of fish-oil is at hand. It is advisable before testing a sample 
 of oil in this way to remove from the oil all impurities, as far as 
 possible. Volatile oil is removed with comparative ease. Free 
 rosin can be largely removed by repeated treatment with moder- 
 ately strong alcohol, and subsequent removal of any alcohol that 
 may remain dissolved in the oil by treatment with water and set- 
 tling, keeping the vessel hot. Unsaponifiable matter and soaps 
 cannot be easily removed, but in extremely important cases it 
 might be advisable to prepare a quantity of the fatty acids of the 
 sample to be examined by saponifying and then acidifying the oil, 
 after freeing it from rosin, as far as possible. Volatile oil could be 
 removed during the saponification. This sample of fatty acids 
 could then be tested under the same conditions as the fatty acids 
 prepared from samples of pure linseed-oil. 
 
 Livache's Test. The power possessed by linseed-oil in 
 greater measure than by any other oil to absorb oxygen from 
 the air, and consequently to increase in weight, is measured 
 by Livache's test (Compt. rend., 1895, I2 j &4 2 )- * n order to 
 hasten the absorption of oxygen a weighed quantity of the oil 
 is spread out in a thin film on a watch-glass, and mixed with 
 finely divided precipitated metallic lead. At the end of each 
 period of twelve or twenty-four hours the mixture is weighed 
 and the increase in weight noted. The amount of oxygen 
 absorbed in this way by oils is roughly proportional to the absorp- 
 tion of bromine and iodine, except in the case of fish-oils. Men- 
 
LINSEED-OIL. 6r 
 
 haden-oil, though having a power to absorb bromine or iodine 
 but slightly inferior to that of linseed-oil, falls very short in prac- 
 tical drying properties, and as Livache's test comes nearer than 
 any other to an actual determination of the real drying power 
 of an oil, menhaden-oil is indicated by a proportionately lower 
 absorption of oxygen than of that of linseed-oil, than the bromine 
 or iodine figures of the sample. Details of the process will be 
 found in Benedikt, Allen, and Gill. 
 
 Livache found linseed-oil to gain 14.3 per cent of its weight 
 in two days, while Jean (Monit. Scient., 15, 891) found menhaden- 
 oil to gain only 5.454 per cent, in three days. 
 
 Thus if an oil have a bromine addition figure (after allow- 
 ing for the effect of other impurities found) that is only slightly 
 lower than that of linseed-oil, but absorbs only a small amount 
 of oxygen by Livache's test, there is good proof of the presence 
 of menhaden-oil. 
 
 With regard to other adulterants of linseed-oil the test does 
 not furnish information at all comparable in value with that 
 obtained by determining the bromine figures. 
 
 Index of Refraction. With regard to the index of refraction 
 the difference between the figures of linseed-oil and of its adul- 
 terants is comparatively small, and much less work has been 
 done in this direction than in others. The following figures- 
 are taken from several authorities: 
 
 Oil. Refractive Index. 
 
 Linseed-oil i .484 to i .488 at 15 C. 
 
 Cottonseed-oil i .475 at 15 C. 
 
 Rosin-oil i . 535 to i . 549 at 18 C. 
 
 Mineral oil i . 438 to i . 507 
 
 Turpentine-oil i . 464 to i . 474 
 
 Rosin (colophony) 1-548 
 
 (1.478 at 20 C. 
 
 Corn-oil. \ _ 
 
 (1.4765 at 15 C. 
 
 Fish-oil i .480 at 15 C. 
 
 The Action on Polarized Light. The use of the polariscope 
 is very limited in testing linseed-oil. Little has been done with it,. 
 
^2 TECHNOLOGY OF PAINT AND VARNISH. 
 
 and its value in this connection seems to be confined to the detec- 
 tion of rosin-oil, which is dextro-rotatory. Valenta finds its 
 rotatory power to be 3O-4O, and Demski and Morawski find 
 it to be 50. American oil of turpentine deviates polarized light 
 to the right, while the French oil of turpentine deviates to the 
 left. Mineral oils have no rotatory power, or only a slight one, 
 and, according to Bishop, vegetable oils, with the exception of 
 sesame-oil, rotate to the left. Therefore a right-handed rotation 
 in a sample of linseed-oil is indicative of rosin-oil. 
 
 The Best Tests to Apply in Analyzing Linseed-oils. In 
 examining linseed-oil for adulteration it will usually be found 
 advisable to make the following determinations: 
 
 1. Determine the specific gravity at 15. 5 C., water at the 
 same temperature being taken as i.ooo. This should be between 
 .931 and .937 for raw oil, and between .931 and .950 for boiled 
 oil. 
 
 2. Determine the bromine addition figure and the bromine 
 substitution figure. The former should be between 100 and no 
 and the latter should not be higher than 5, though it may rarely, 
 in a pure oil, be as high as 7, probably from the presence of an 
 unusual amount of non-fatty matter extracted with the oil from 
 the seed. The figures to be expected are the same for raw oil 
 and boiled oil as now made. 
 
 3. Test for volatile oil by the odor and determine the amount 
 present by distillation with steam. There should be none. 
 
 4. Determine the amount of non-volatile unsaponifiable 
 material. There should be less than 2.5 per cent, in either raw 
 or boiled oil. 
 
 5. Determine the acid figure. It should be less than 5 in 
 either raw or boiled oil, but figures as high as 7 may indicate 
 that the oil is old rather than adulterated, and a still higher figure 
 may prove to be due to the presence of mineral acid from 
 refining. 
 
 6. Determine the Kcettstorfer figure. This should not be less 
 than 187 in the case of raw oil, nor less than 186 in the case of 
 boiled oil, and in neither case should be higher than 196. 
 
LINSEED-OIL. 63 
 
 7. If the appearance, odor, etc., of an oil point to the presence 
 of fish-oil, apply Maumene's and Livache's tests. 
 
 Adulteration will usually be indicated by more than one test, 
 and if abnormal figures are obtained by one process pointing 
 to a certain kind of adulteration, while others, which would also 
 be expected to be abnormal, are not so, it is evident that some 
 new adulterant is to be sought for, or that the oil has, perhaps, 
 been made by some unusual process. 
 
 Detection and Determination of the Several Adulterants. 
 i. Non-volatile Mineral Oil. Indicated by low bromine absorp- 
 tion, low bromine addition figure, low Kcettstorfer figure, and 
 low specific gravity. Separated and weighed together with 
 rosin-oil as unsaponifiable matter, and separated from rosin- oil 
 by nitric acid. 
 
 2. Benzine. Indicated by odor, low specific gravity, low 
 Kcettstorfer and bromine addition figures, and low bromine 
 absorption. Separated and weighed or measured together 
 with turpentine, as volatile oil, by distillation with steam, and 
 separated from turpentine with fuming nitric acid. 
 
 3. Turpentine. Indicated by odor, low specific gravity, low 
 Kcettstorfer figure, and high bromine absorption, bromine addi- 
 tion figure, and bromine substitution figure. Separated and 
 weighed together with benzine as volatile oil by distillation with 
 steam, and determined by difference, after treating the volatile oil 
 with fuming nitric acid and hot water. 
 
 4. Rosin-oil. Indicated by high specific gravity, low 
 Kcettstorfer figure, often high acid figure, low bromine absorption 
 and bromine addition figure, and high bromine substitution 
 figure. Separated and weighed together with non-volatile mineral 
 oil as unsaponifiable matter, and determined by difference, after 
 treating the mixture with nitric acid. 
 
 5. Rosin. Indicated by high specific gravity, high bromine 
 absorption, low bromine addition figure, high bromine substitution 
 figure, and when in the free state by high acid figure. Separated 
 and weighed or titrated by TwitchelPs process (J. Soc. Chem. Ind., 
 1891, 10, 804). It is carried out by treating the mixed fatty and 
 
TECHNOLOGY OF PAINT AND VARNISH. 
 
 rosin acids obtained by acidifying the soap solution after extrac- 
 tion with ether in the determination of unsaponifiabie matter, in 
 absolute alcohol solution, with hydrochloric gas. By this treat- 
 ment the fatty acids are converted into ethyl esters, while the rosin 
 acids are not. The products of the reaction are boiled with water, 
 the mixed fatty acid esters and rosin separated and dissolved in 
 naphtha. From this solution the rosin is extracted by potassium 
 hydrate solution. The rosin soap solution is treated with acid and 
 the liberated rosin weighed. For full details Allen's Comm. Org. 
 Anal. (3d ed.) should be consulted. 
 
 Cladding's method, Amer. Chem. J., 3, 416, formerly much 
 used for the determination of rosin, depends upon the solubility of 
 silver resinate in ether, while the silver salts of fatty acids are in- 
 soluble. 
 
 6. Menhaden-oil. Indicated by a bromine addition figure 
 slightly lower than that of linseed-oil, but a higher Maumene figure 
 and a very much lower figure by Livache's test. Indicated also 
 by characteristic taste and odor. 
 
 7. Corn- and Cottonseed-oils. Indicated by low specific gravity, 
 low bromine absorption, and low bromine addition figure. 
 
 TABLE SHOWING THE EFFECTS OF TEMPERATURE UPON THE SPECIFIC GRAVITY 
 
 OF LINSEED-OIL. 
 
 (In all cases water at 15.5 C. taken as unity.) 
 
 
 g 
 
 A* 
 
 4J 
 
 44 
 
 J 
 
 o 
 
 J 
 
 
 1 
 
 
 1 
 
 
 
 
 O **' 
 "0 
 
 OiL 
 
 j| 
 
 Oj 
 
 5 
 
 O . 
 
 IM P< 
 
 ^0 
 
 ^0 
 
 
 4j 
 
 "? 
 
 ^d 
 
 tC 
 
 Si 
 
 SiT 
 
 M 
 
 
 1 
 
 |% 
 
 g 
 
 11 
 
 o< 
 
 WD 
 
 CJ, 
 
 8? 
 
 6" 
 
 American raw linseed. . . 
 
 S 2 
 
 .9336 
 
 9255 
 
 .8736 
 
 . 000650 
 
 .000721 
 
 .000711 
 
 Raw Calcutta linseed 
 
 
 
 
 
 . 000698 
 
 
 
 Raw American linseed. . 
 
 02 
 
 0^6 
 
 02 CC 
 
 
 . 000650 
 
 
 
 Raw American linseed. . 
 
 9e 
 
 .Q-24C 
 
 .026"? 
 
 
 .000656 
 
 
 
 Boiled American linseed. 
 
 j 
 38 
 
 yo "O 
 .9385 
 
 y^ w o 
 
 .9297 
 
 
 . 000707 
 
 
 
 Boiled American linseed. 
 
 
 
 
 
 onA^Sc 2 
 
 
 
 Raw American linseed . . 
 
 58 
 
 9327 
 
 .] 9293 
 
 .8732 
 
 ."] 
 
 
 
 . 000704 
 
 Raw American linseed . . 
 
 73 
 
 9332 
 
 9 2 45 
 
 .8731 
 
 .000693 
 
 .000714 
 
 . 0007 i i 
 
 Boiled American linseed. 
 
 72 
 
 933 6 
 
 .9258 
 
 8735 
 
 .000625 
 
 .000726 
 
 .000714 
 
 Menhaden 
 
 71 
 
 .9316 
 
 .9235 
 
 .8712 
 
 . 000646 
 
 
 
 .000716 
 
 
 / 
 
 yo 
 
 
 
 
 
 
LINSEED-OIL. 
 
 A TABLE SHOWING THE CORRECTION FOR TEMPERATURE TO BE ADDED TO OR 
 SUBTRACTED FROM THE READINGS OF A GLASS HYDROMETER, CORRECT AT 
 60 F. (i5.5 C.)i IMMERSED IN LINSEED-OIL, FOR EACH DEGREE FROM 
 40 F. TO 85 F. 
 
 Calculated from the results obtained in determining the specific gravity of sam- 
 ples Nos. 88, 90, 92, 94, and 95, by the following formula: 
 
 Let a = weight of oil displaced by glass plummet at 15. 5 C.; 
 b = weight of oil displaced by glass plummet at 28. o C.; 
 c = weight of water displaced by glass plummet at 15. 5 C.; 
 d difference in apparent gravity of hydrometer for i. 
 
 a-b 
 
 = d. 
 
 28 - 15-5 
 
 By substituting 82. 4 F. and 60 F. for 28 C. in the formula the correction 
 will be found for i F. 
 
 Correction for i F. = .000361. Correction for i C. = .000650. 
 
 Ther- 
 mometer 
 Reading. 
 
 Subtract. 
 
 Ther- 
 mometer 
 Reading. 
 
 Subtract. 
 
 Ther- 
 mometer 
 Reading. 
 
 Add. 
 
 Ther- 
 mometer 
 Reading. 
 
 Add. 
 
 40 Fahr. 
 
 .0072 
 
 51 Fahr. 
 
 .0032 
 
 6 1 Fahr. 
 
 .0004 
 
 74 Fahr. 
 
 .0051 
 
 41 
 
 .0069 
 
 52 
 
 .0029 
 
 62 
 
 .0007 
 
 75 
 
 .0054 
 
 42 
 
 .0065 
 
 53 
 
 .0025 
 
 63 
 
 .001 1 
 
 76 
 
 .0058 
 
 43 
 
 .0061 
 
 54 
 
 .0022 
 
 64 
 
 .0014 
 
 77 
 
 .0061 
 
 44 
 
 .0058 
 
 55 
 
 .0018 
 
 65 
 
 .0018 
 
 78 
 
 .0065 
 
 45 
 
 .0054 
 
 56 
 
 .0014 
 
 66 
 
 .0022 
 
 79 
 
 .0069 
 
 46 
 
 .0051 
 
 57 
 
 .001 1 
 
 67 
 
 .0025 
 
 80 
 
 .0072 
 
 47 
 
 .0047 
 
 58 
 
 .0007 
 
 68 
 
 .0029 
 
 81 
 
 .0076 
 
 48 
 
 .0043 
 
 59 
 
 .0004 
 
 69 
 
 .0032 
 
 82 
 
 .0079 
 
 49 
 
 .0040 
 
 60 
 
 .0000 
 
 70 
 
 .0036 
 
 83 
 
 .0083 
 
 50 
 
 .0036 
 
 
 
 
 .0040 
 
 84 
 
 .0087 
 
 
 
 
 
 72 
 
 .0043 
 
 85 
 
 .0090 
 
 
 
 
 
 73 
 
 .0047 
 
 
 
66 
 
 TECHNOLOGY OF PAINT AND VARNISH. 
 
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70 TECHNOLOGY OF PAINT AND VARNISH. 
 
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CHAPTER VI. 
 
 MANUFACTURE OF VARNISH. 
 
 THE manufacture of varnish is carried on at the present time 
 as a definite business, independent of any other, and is in fact 
 subdivided so that the same concern does not make or try to 
 make all kinds of varnish. In fact it is not unusual for some of 
 the smaller and more rarely some of the larger manufacturers to 
 purchase varnishes, either for direct sale or for use in making 
 some special product, from other makers who are particularly 
 successful in certain lines of the work. The greater part of the 
 varnish now used is made from linseed-oil and resins, with tur- 
 pentine or benzine as dilutent ; but most, or probably all, of these 
 makers also make a little shellac varnish, which is a spirit varnish; 
 and they all make damar varnish, which is a solution of damarin 
 spirits of turpentine. On the other hand, they almost never try 
 to make the more unusual spirit varnishes, or those which have 
 nitro-cellulose as a base. Some of the spirit- varnish makers, 
 probably most of them, buy small quantities of oleo-resinous var- 
 nishes to add to their compounds, and not a few paint-manufac- 
 turers not only buy what varnish they use as an ingredient of 
 their paint, but do a considerable business as varnish-merchants 
 on goods made for them and put up in special packages under 
 their own label and seal. 
 
 The writer of this disclaims any special and particular knowl- 
 edge of what is done by English and European varnish-makers, 
 but in America the varnish-factory equipment may thus be briefly 
 described. 
 
 Raw Materials. The raw materials are resins, oil, and tur- 
 pentine or benzine. To these may be added the necessary driers, 
 
 71 
 
72 TECHNOLOGY OF PAINT AND VARNISH. 
 
 lead and manganese compounds; and, of course, fuel. The oil 
 is almost invariably bought as raw oil, i.e., oil which has no 
 addition of driers and has not been highly heated. This is bought 
 ^ either in barrels of 45 to 52 gallons each, usually called 5o-gallon 
 barrels, in which case the buyer pays for the barrel, which he 
 afterward uses to ship varnish in, or in large casks of 200 to 300 
 gallons, which are the property of the oil-merchant, to whom they 
 are returned. Oil is invariably bought from the manufacturers, 
 as no varnish-maker would feel confidence in oil bought from a 
 middleman, and is usually of especially fine quality, which sells 
 at from one to three cents a gallon above the market price of ordi- 
 nary pure oil. It is perfectly clear and bright from having been 
 tanked a sufficient time and filtered. 
 
 Storage and Treatment of Oil. When this oil is received, part 
 of it is used just as it is out of the barrels, but the most of that 
 which is to be used for fine varnishes is put through some sort of 
 treatment and then pumped into tanks holding one to three 
 thousand gallons, in a storehouse, where it can be held at a tem- 
 perature which is regulated by the operator, usually 90 to 110 
 F., probably never exceeding 120. This keeps the oil rather 
 thinly fluid, which promotes its settling and clearing. Each var- 
 nish-maker has his own secret methods of treating oil, which 
 probably are all about alike. One of the most common is to 
 heat the oil to 500 or 550 for a very short time. This seems 
 to char certain impurities and coloring-matter, which will then 
 settle out. Another is to heat with a very small amount of man- 
 ganese, or lead oxides, or both: not enough to make the oil dry 
 much more rapidly, but a very little seems to affect the quality of 
 the oil for further use. A comparatively small part of the oil is 
 converted into "boiled oil" of various sorts. The varnish-maker 
 does not make boiled oil for sale, but uses several different kinds 
 in his work. All these oils are tanked for a considerable time, 
 usually several months, before they are considered to be in the 
 best condition for use. 
 
 Resins. The varnish-resins are stored either in the original 
 packages in which they are bought, or in large bins. Usually a 
 
s # 
 

MANUFACTURE OF VARNISH. 73 
 
 considerable quantity of the more common ones is kept in bins, 
 but the less common in the original packages. It is the practice 
 of the varnish- makers to keep a large stock on hand, so as to be 
 able to take advantage of the market. Probably from 10 to 20 
 per cent, of the entire capital of the business is invested in this 
 way. These resins come from all parts of the tropical and 
 south temperate zones and are not always to be had when wanted. 
 Oil, on the contrary, can be contracted for any length of time 
 ahead. 
 
 Spirit of Turpentine. Nearly all varnish-factories contain 
 one or more tanks of turpentine. This is stored in steel tanks 
 built in the open air and sometimes hold over a hundred thousand 
 gallons of spirit of turpentine. These tanks are closed, except 
 for a vent to admit air when the liquid is being pumped in or 
 out. A few makers have also tanks for benzine, but usually this 
 is bought from day to day and no tank, or only a small one, is 
 necessary. Other supplies are kept in casks, boxes, or small 
 bins. 
 
 Packages. Varnish is sold in barrels, half-barrels, and in 
 tin cans ranging in size from lo-gallon jacketed cans (cased 
 with wood) and 5 -gallon cans, both with and without jackets, 
 down to half-pints. All these, except the jacketed cans and 
 the very small ones, are shipped in special boxes holding from 
 i to 12 cans of a size, so that considerable space must be allowed 
 for empty packages. When filled, these cans are closed, not 
 with a stopper, but with a piece of sheet brass, stamped to fit 
 the nozzle of the can and made tight by a reamer, a little device 
 worked by hand which makes an absolutely tight closure. In 
 the box with the can is placed a wooden stopper or a metal cap 
 to use after the brass cap has been torn off. 
 
 Labels. The can, of course, is properly labelled. The 
 stock of labels, several different sizes being required for each 
 kind of varnish, frequently amounts in cost to from two to four 
 thousand dollars. 
 
 The buildings are heated by steam, which is generated in 
 any suitable boiler. Comparatively little power is used, chiefly 
 
74 
 
 TECHNOLOGY OF PAINT AND VARNISH. 
 
 for pumping and the like, but coke is the fuel used under the 
 varnish-kettles, no other fuel having been found which so well 
 satisfies the requirements. 
 
 It was originally the custom to melt the resin in small quan- 
 tities; in fact the business was formerly a small business, but a 
 good many years ago the American practice was to melt 100 
 pounds at a time, and this amount was so convenient for compu- 
 tations that it is still accepted as the varnish-maker's unit, but 
 the present general practice is to melt 125 pounds at a time. 
 
 VARNISH-KETTLE AND TRUCK. 
 
 Varnish-kettle. For this purpose the kettle (see illustration) 
 is, when new, about 36 inches in height and also in diameter, 
 and weighs when new about 130 pounds. The bottom, which 
 is riveted on, is the part which gives out first. Then the strip 
 containing the rivet-holes is cut off and a new bottom put on, thus 
 decreasing the depth of the kettle. This is repeated from time 
 to time; finally, the whole of the kettle becomes too thin to be 
 safe, and when sold for old copper the weight is sometimes not 
 more than 80 pounds. The fireplace is cleaned out and the 
 material for the fire prepared before leaving at night, or very 
 early in the morning. The fire is started early, and the fire-pit 
 is a glowing mass of coke when the varnish-maker is ready to 
 begin work. The resin has already been put in the clean kettle, 
 which sets on its truck; the loose cover is on, and the kettle is 
 ready to put on the fire, which comes almost, but not quite, in 
 
FIREPLACE IN THE OLDEST AMERICAN VARNISH-CHIMNEY. 
 
 By the courtesy of Edward Smith & Co. 
 

MANUFACTURE OF VARNISH. 75 
 
 contact with the bottom of the kettle. Through a hole in the 
 cover the varnish-maker inserts a slender iron rod, set in a 
 wooden handle, as Theophilus did about a thousand years ago, 
 and stirs the melting mass of resin. 
 
 Melting the Resin. When all the lumps are gone, and the 
 melted gum, a little of which adheres to the stirring-rod when 
 the operator takes it out for inspection, is quite liquid, the kettle 
 is drawn off the fire. By this time it is about half an hour 
 from the beginning from 10 to 25 per cent., by weight, of the 
 resin has been driven off in the form of a pungent, irritating, 
 highly inflammable vapor. To keep this from catching fire the 
 cover is used, and the free escape of the vapor is permitted by 
 the little chimney in the middle of the cover, which so discharges 
 the issuing stream of vapor that the current of air which is rush- 
 ing up the chimney carries it quickly away from the fire. The 
 escaping vapor causes the melted part of the resin to foam, and 
 if this appears too near the top, the operator draws the kettle 
 away from the fire, unless he can, with his stirring-rod, beat 
 down the foam. It is clearly necessary to have considerable 
 space in the kettle over the resin, and formerly the kettles were 
 made much higher in proportion to their width than now. It 
 is not common to use a thermometer in melting resin because 
 the essential thing is not to reach a certain temperature, but to 
 melt the resin, and this is best told by the feeling of it through 
 the stirring-rod, by the experienced operator. In the laboratory, 
 however, where the lumps of resin are much smaller, the thermom- 
 eter is necessary. The temperature is seldom below 650 F. 
 when the melting is completed. The temperature and the 
 percentage of loss vary greatly with different resins. 
 
 Adding the Oil. When the resin is all melted and the kettle 
 has been drawn from the fire, and the heat subsided a little, 
 and the foam has gone down, the linseed-oil, which has been 
 made ready in another kettle, is slowly added. The oil is by 
 some, perhaps a majority of makers, previously heated to about 
 500, but many use less heat. Some heat only a little above 
 212 and some not above 100 F. Of course if only a little 
 
76 TECHNOLOGY OF PAINT AND VARNISH. 
 
 oil is added its temperature has not much effect on the mass, 
 but it is common to have the oil hot. The amount of oil added 
 is variable, according to the kind of varnish desired. It is com- 
 monly measured in United States gallons, which weigh 7j pounds, 
 but the varnish- maker is obliged to buy his oil by weight, and a 
 gallon is then said to weigh yj pounds. The price is always 
 so much per gallon, but a gallon of linseed-oil, when buying it 
 from the oil-manufacturers, is a conventional, not a standard, 
 gallon, so that the varnish- maker has to buy about 3 per cent. 
 more than he sells. Of course a gallon of hot oil weighs less 
 than a gallon of cold oil, and if it is added hot allowance must 
 be made for that, but usually, if it is hot, it was. previously meas- 
 ured cold into the pot in which it was heated. 
 
 Cooking the Varnish. As soon as the oil has been added, 
 which is done gradually, the mixture being constantly stirred, the 
 kettle is put back on the fire. Although the mixture appears to 
 be a complete solution, it is not really so at this stage, for if the 
 mixture, or a drop of it, be allowed to cool, the resinous part will 
 separate, making the drop cloudy ; and the common rule is to with- 
 draw the stirring-rod from time to time and let a drop or two of 
 the mixture fall on a piece of glass, where it cools at once and 
 shows by its cloudiness that the combination has not, or by its 
 clearness that it has, taken place. The more approved practice 
 now, however, is to keep a thermometer in the liquid and heat to 
 a certain temperature, previously determined as the best for the 
 particular varnish which is being made, for a certain length of 
 time. This temperature, roughly speaking, is not very far from 
 500 F., but not unfrequently it is found best to make the heat 
 increase and diminish from time to time, according to a tempera- 
 ture curve which is established for a given mixture. In general 
 it may be said that varnishes containing a large proportion of oil 
 require more cooking than those using a small amount. A 30- 
 gallon varnish, for example, may be cooked six or eight hours, or 
 more, while a lo-gallon one will be done in an hour or two, and 
 where a very small percentage of oil is used the mixture is only 
 heated enough to be sure it will not separate on cooling. One 
 
MANUFACTURE OF VARNISH. 77 
 
 effect of cooking is to make the varnish heavy in body, or, as the 
 English say, " stout"; that is, it increases its viscidity or viscosity, 
 and the longer it is cooked the more turpentine will be required 
 to thin it to the conventional standard of viscosity which is desired 
 in a finished varnish. 
 
 Undercooking. If it is cooked but a little it will take less 
 than the normal amount of turpentine; hence a gallon of such 
 varnish will contain a large proportion of non- volatile matter, and 
 when it is spread on a surface it will dry to a film of more than 
 the usual thickness, and this, in turn, requires more oxygen to dry 
 it, and hence a longer time, than a thinner film. 
 
 Overcooking. Conversely, a varnish which is overcooked 
 takes a large amount of turpentine, a larger percentage of the 
 film evaporates, the film is thinner, and it dries more quickly. 
 Looking at it in another way, since turpentine is less costly than 
 the finished product, the more the varnish is cooked and the more 
 turpentine is added the less is the cost per gallon; but an over- 
 cooked varnish is liable to be spoiled by carrying the cooking 
 process too far, and hence the risk makes such a varnish, in the 
 long run, more costly than it otherwise would be. From a stand- 
 point of durability, the varnish which is overcooked leaves a 
 thinner film, which is on that account less durable, than one less, 
 cooked; but if it is undercooked the oil and resin are not very 
 thoroughly combined, and the film perishes because its ingredi- 
 ents separate when exposed to the air and sunlight. Since var- 
 nishes continually grow darker in color by cooking, the varnishes 
 which are undercooked are paler in color, and on that account 
 fetch a higher price, but obviously are not to be compared in real 
 value and durability with a varnish of the same color made of 
 more costly materials, that is, with carefully bleached oil and 
 pure, clean, pale, hard resins which do not discolor so much in 
 melting, and more thoroughly combined by long and judicious 
 cooking. Most of these considerations apply also to melting the 
 resin. When this is nearly melted and the full heat is on, it 
 darkens rapidly every minute it is kept over the fire ; but the un- 
 decomposed resin is not soluble in oil, and if the process is not 
 
78 TECHNOLOGY OF PAINT AND VARNISH. 
 
 carried far enough the result will be, in extreme cases, that when 
 the oil is added the varnish so made will be a jelly, which must 
 be thrown away; and if the result is not so bad as that, the varnish 
 thus made, while pale in color, will easily suffer decomposition. 
 On the other hand, if the melted resin is heated too long it be- 
 comes very dark in color and is less valuable in other respects 
 also. As a rule, when we consider the different grades of a given 
 kind of resin, Kauri for instance, we find that the very pale sorts 
 are a softer resin than the darker pieces. These soft resins take 
 on color more rapidly than the hard ones, hence the tendency is 
 to melt them at a lower temperature, and the resulting varnish, 
 while pale in color, is less durable than that made of the darker 
 resins. 
 
 Different Qualities of Resins. But the cheaper grades, that 
 is, when we get below the normal or standard grade, are dark not 
 only because of the natural color of the resin, but because it con- 
 tains impurities of various sorts, dirt which, in most cases, settles 
 out and does not injure the varnish much, except in color. Some 
 of these moderately cheap, very dark-colored varnishes are of the 
 most excellent quality in everything but color, and in many cases 
 this is not an objection. For instance, a varnish for mahogany 
 or any such dark wood ought to be dark in color. The dry film 
 is like red-brown glass, perfectly clear and transparent, and im- 
 parts a rich effect whose brilliancy cannot be attained in any 
 other way. But if a pale varnish of fine quality is desired, it is 
 necessary to select a pale hard resin and one which discolors as 
 little as possible in melting. These are rare and costly. Some 
 of the finer sorts cost as much as 75 cents per pound. If such a 
 resin does not make a sufficiently pale product, the maker pro- 
 ceeds to pick out the very best pieces from this most valuable 
 resin. It may be necessary to pick over a thousand pounds to 
 get a hundred pounds, enough for one melt, of these select pieces. 
 This hand-picked resin not only costs the original 75 cets a 
 pound, plus the cost of skilled labor for picking over the thousand 
 pounds, but the residuary 900 pounds has by this process been 
 graded down to, let us say, 6ocent resin, a loss of 15 cents a 
 
MANUFACTURE OF VARNISH. 79 
 
 pound on 900 pounds, or $.1.35. If the labor cost $15, the 
 cost of this hundred pounds of resin would be $225, or $2.25 a 
 pound. Clearly, a varnish made of such a resin will be costly. 
 It will, therefore, be used only indoors, that is, for objects not 
 exposed to the weather. Therefore, it will be made with a 
 rather small proportion of oil, and since oil is cheap compared 
 with such a resin, it will have its cost reduced as little as possible 
 in this way. It is impossible to make, even if we could sell, 
 much of this sort of varnish, which must, therefore, have a 
 special small tank for itself, and it will naturally demand the 
 very best and highest-priced labor in the factory at every step 
 of its making and handling until it gets out of the shipping- 
 room. 
 
 Very Costly Varnish. The unavoidable waste in handling a 
 material which is sold in such small quantities is considerable, 
 and it is easily seen that it is quite practicable to make a varnish 
 which is easily worth, from a factory standpoint, at least twenty 
 dollars a gallon and which may be absolutely no better in any 
 respect except color than another made of similar but less costly 
 materials and sold for one-quarter or one-fifth the price. On the 
 other hand, if a man builds a yacht at a cost of half a million 
 dollars and wishes to have in it his wife's boudoir varnished with 
 such a material, the cost does not, and ought not, to stand in the 
 way. 
 
 It has been said that there is danger, if the resin is not 
 thoroughly melted and decomposed, or if the mixture of resin 
 and oil is not sufficiently heated for a long enough time, that 
 the same will be spoiled. It should further be said that if the 
 compound of resin and oil be overcooked it is liable to turn to 
 a viscid, insoluble, infusible mass, and this is the more likely 
 to occur if the resin was not in the first place properly melted, 
 and is more likely to take place with, varnishes containing little 
 oil than with those which have more. It may be remarked 
 here that varnishes containing little oil are sometimes spoken 
 of as "short" varnishes, and those with a large amount of oil 
 as "long" or sometimes "rich," but the terms "quick" and 
 
8o TECHNOLOGY OF PAINT AND VARNISH. 
 
 "slow" refer to the rate of drying and not to the composition. 
 It is also worthy of note that in all varnish-factories a certain 
 amount sometimes a pretty large one of common rosin, or 
 colophony, is used, and this is always called rosin; and partly 
 because of the similarity of this word to resin, partly because 
 from time immemorial all resins have been commercially spoken 
 of as "gums," the word resin is seldom heard in a varnish -factory, 
 all the true varnish-resins being called "gums." 
 
 " Gum." But rosin is never called a gum. When the oil 
 and resin have been properly cooked the kettle is withdrawn 
 from the fire and taken to a sufficient distance, usually into a 
 shed or well- ventilated room, from which it is impossible that 
 the vapors about to be generated should reach the fire and thus 
 cause a conflagration; a quantity of spirit of turpentine, which 
 has been measured out into a special receptacle, is added, being 
 allowed to run in in a small stream, while the attendant vigorously 
 stirs the liquid to promote the solution. 
 
 Thinning Down with Turpentine. Although the oil and 
 resin compound has previously been allowed to cool somewhat, 
 its temperature is still a little above the boiling-point of the tur- 
 pentine, and until the whole has been sufficiently cooled by the 
 addition of cold turpentine, part of the latter is converted into 
 vapor and flows over the edge of the kettle in the form of a gas, 
 highly inflammable, and indeed explosive if ignited. If benzine 
 is used instead of turpentine, as it is for making cheap varnishes, 
 this danger is greatly increased, and most varnish fires occur 
 from this cause. Fires do indeed sometimes, but rarely, occur 
 in the chimney where the oil and resin only are used, but these 
 are easily and quickly put out by smothering them, covering 
 the kettle with wet burlap or other wet cloths, a supply of which 
 is constantly on hand. Sooty matter sometimes collects on 
 the bottom of the kettle, and in this sparks of fire are preserved 
 for a considerable time, and the attendant should most care- 
 fully see that no such thing is allowed to cause a fire, which is 
 not only destructive to the part of the factory where it is, but 
 is also exceedingly dangerous to the workman who is stirring in 
 
MANUFACTURE OF VARNISH. 8l 
 
 the turpentine or benzine,, Fires are avoidable if proper care 
 is taken. In the factory with which the writer is connected 
 a fire of this sort occurred many years ago, when benzine was 
 first introduced and before it was known that it was more dan- 
 gerous than turpentine; but that one fire is the only serious one 
 in this factory in seventy-five years. The most common cause 
 of varnish fires is that the thinning-down shed is not far enough 
 away or not perfectly separated from the fireplace where the 
 varnish is made. When making cheap rosin varnishes, more- 
 over, it is common practice to make a batch of varnish, get it 
 thinned down and pumped out of the kettle all within an hour, 
 and sometimes considerably within the hour. Such haste, so 
 different from the more dignified and deliberate proceedings 
 which distinguish the making of high-class goods, is a contribu- 
 tory cause of much importance. 
 
 If the varnish is one containing a large proportion of linseed- 
 oil, the compound of oil and resin will be much more fluid than 
 if a small amount of oil is used, and consequently a smaller propor- 
 tion of turpentine will be needed than is used with the more 
 viscid compound containing a small proportion of oil. Of 
 course it is possible to overcook a "long" varnish so as to make 
 it take more than its normal percentage of turpentine, but since 
 this is rarely done we have some indication of the proportion 
 of resin and oil when we determine the percentage of turpentine, 
 or rather of volatile liquid corresponding to turpentine, which 
 fortunately may be easily done. Varnishes made with 8 gallons 
 of oil to ico pounds of resin have about 25 gallons of turpentine 
 added, those containing 30 gallons of oil have about 32 of turpen- 
 tine, and intermediate ones are somewhat in proportion. 
 
 Turpentine Better than Benzine. The question will naturally 
 arise, is turpentine, which costs three to five times as much as 
 benzine, any better than the latter? In most cases it is, for 
 several reasons. One of these is that it is much less rapidly 
 evaporated. There is much more attraction between the oleo- 
 resinous compound and turpentine than between it and benzine, 
 and for that reason turpentine goes off more slowly, and benzine 
 
82 TECHNOLOGY OF PAINT AND VARNISH. 
 
 dissolves in the air by diffusion far more rapidly than turpentine, 
 and this has a like effect. It is desirable to have the volatile 
 ingredient of varnish pass off somewhat slowly, especially at 
 first, for when the varnish is spread with a brush it is impossible 
 to avoid putting it on with slight irregularity, and the brush- 
 marks thus made will disappear if the varnish retains its liquid 
 condition for some time, as is the case if turpentine is the solvent. 
 The little ridges of liquid varnish flow out and level up the hollows 
 and the whole surface becomes smooth. Such varnish is said 
 to have good flowing quality. If made with benzine, the latter 
 evaporates almost at once and the varnish takes its initial set 
 before the ridges have disappeared; the surface then dries with 
 these imperfections, and the finished surface shows these brush- 
 marks. These may be seen in any furniture -store on low-priced 
 furniture. Good flowing quality is also helped by other things; 
 the composition, method of manufacture, and age of the varnish 
 have their influence, but the presence of either turpentine or 
 benzine is the most important single factor. 
 
 Oxidation of Turpentine. Another peculiarity of turpentine 
 is that it never completely evaporates. A small portion of it 
 remains behind as an elastic resinous substance, which is con- 
 sidered a desirable ingredient in varnish. Benzine evaporates 
 completely. This thickening of turpentine is due to a process 
 of oxidation, and there is no doubt in the mind of the writer that 
 turpentine has some effect as a drier, acting as lead and manganese 
 compounds do, by passing oxygen on from the air to the oleo- 
 resinous compound. It is possible that a turpentine varnish 
 dries through more quickly than a similar varnish made with 
 benzine, notwithstanding the slow setting of the former. 
 
 Factory Nomenclature. If 10 gallons of oil is added to the 
 melted mass, weighing, let us say, 95 pounds, which results from 
 melting 125 pounds of resin, the resulting varnish is said to be an 
 8-gallon varnish, because.it contains 8 gallons of oil to every 100 
 pounds of resin originally taken. Similarly, 25 gallons of oil 
 would make a 2o-gallon varnish, and so on, the varnishes being 
 designated by the proportion of pil to the hundred pounds of un- 
 
MANUFACTURE OF VARNISH. 83 
 
 melted resin, and nothing is said about the turpentine which is > 
 to some extent, a variable quantity. Of course this is purely a 
 factory nomenclature. The purchaser knows the varnishes he 
 buys by certain descriptive or trade names, and, as in every other 
 business, a name which takes the public fancy is very valuable. 
 Further, the varnish as it comes out of the kettle is not usually 
 of the same composition as any varnish sold, because, in order to 
 get certain qualities, it is necessary to mix varnishes made in dif- 
 ferent ways and of different resins. It will be obvious that if the 
 maker has, for example, three tanks of lo-gallon varnishes, made 
 respectively of Zanzibar, Kauri, and Manila resin, and also three 
 tanks of 3o-gallon varnishes made from the same resins, he is in a 
 position to supply nine different kinds of 2O-gallon varnish, each 
 differing from the others in certain properties peculiar to each 
 mixture, and also in price, making each of these mixtures from, 
 two tanks, and an indefinite number by mixing them in a more 
 intricate manner. 
 
 Art of Mixing Varnishes. It would be indeed remarkable if 
 some of these 20-gallon mixtures were not better for some special 
 purpose, or even for general use, than any possible 20-gallon 
 varnish, made from a single resin, just as it comes from the kettle* 
 It will also be obvious that an indefinite number of 12-, 15-, 18-, 
 22-, 25-, and 28-gallon varnishes may be made from these same 
 tanks, and if , in addition, the manufacturer has a set of tanks of 
 8-, 1 6-, and 20-gallon varnishes, each set representing, say, these 
 same three resins, the number of possible combinations passes 
 imagination. It is to be further remembered that varnishes are 
 made with as little as 3 gallons of oil and as high as 60; that the 
 'more important resins are sold in from two to ten grades, and 
 that the number of these resins is very great and is constantly 
 increasing. It will be seen that a knowledge of the qualities of the 
 various varnishes, and especially of their effect in mixtures, is of 
 as much importance as knowing how to manipulate the materials 
 in the kettle, and the expert, to be an expert, must be intimately 
 and practically acquainted with the use to which the varnish is 
 to be put and the way in which it is necessary to apply it, and how 
 
84 TECHNOLOGY OF PAINT AND VARNISH. 
 
 these uses and conditions vary. He should, therefore, have as 
 the simplest foundation a good working knowledge of the furni- 
 ture trade, of wagon and carriage building of railway engines and 
 coaches, of ship and boat construction, and of house painting and 
 decoration. To these he may add the lesser trades and special- 
 ties, from the making of oilcloth to the japanning of hooks and 
 eyes, as far as his natural abilities and acquired opportunities 
 may allow. 
 
 In view of all the foregoing facts, the proposition that the art 
 of varnish-making offers an opportunity for the continual activity 
 of an ingenious and receptive mind, for an indefinite period, is 
 confidently submitted to the acute perceptions of the candid 
 reader. 
 
CHAPTER VH. 
 
 TUNG-OIL. 
 
 TUNG-OIL, or Chinese wood-oil, is a remarkable oil which sur- 
 passes linseed in its rapidity of drying; it is obtained from the 
 seeds of a tree known to botanists as the Aleurites cor data, much 
 resembling the ornamental tree known to us as Paulownia 
 japonica; the seeds resemble chestnuts and contain somewhat 
 more than half their weight of oil, about four-fifths of which oil 
 is obtained by grinding the seeds and pressing, very much as lin- 
 seed and other vegetable oils are made. The nut is said to be 
 poisonous if eaten; but it is not reported that the oil is so. The 
 oil has a peculiar odor, resembling that of rancid grease obtained 
 from bacon; it is yellow in color, darker than linseed, and is, 
 when fresh, turbid; this turbid oil is said to dry better than it 
 does after it has been cleared. When spread on glass (or other 
 non-absorbent surface) it dries "flat," that is, with a rough sur- 
 face, not glossy, and makes an opaque white film. Linseed-oil, 
 after it has taken its initial set, dries from the outer surface ; but 
 it is commonly said that tung-oil dries throughout at the same rate. 
 As the oxygen is derived from the surface, this statement is no 
 doubt only approximately true; but it dries more rapidly and 
 uniformly than linseed. 
 
 The next most remarkable quality of tung-oil is that if it is 
 heated to about 400 F. it coagulates; it does not break like 
 linseed, but apparently the whole mass of the oil is converted 
 into a polymeric modification, and is a jelly, insoluble in all the 
 ordinary solvents; on this account great care must be taken in 
 "heating it. It may sometimes be heated to about 500 F. for a 
 
 85 
 
86 TECHNOLOGY OF PAINT AND VARNISH, 
 
 few minutes; but prolonged heating to 400 F. is likely to cause 
 it to coagulate into a gelatinous solid free from a greasy feeling. 
 
 Tung-oil seems to be rather more repellent to water than lin- 
 seed; but the writer has had very little practical experience with 
 it; the varnishes made with it have not seemed to be as reliable 
 as those made with linseed-oil; they are liable to undergo a de- 
 composition while standing in the tank or can, in many cases. 
 
 There is a considerable amount of this oil used in the United 
 States; the most of it seems to be purchased by makers of rosin 
 varnishes, some of whom must -have successful methods of using 
 it. It is more costly than linseed. 
 
 Its specific gravity averages about .938, varying from .936 to 
 .944; its saponification number is about 192.5, varying from 191 
 to 197; its iodine number is 160, varying from 155 to 165. 
 
 It is said by some authorities that the gelatinization of this 
 oil by heat is accompanied by a large absorption of oxygen; by 
 others that it is not so, but is a polymeric change. The latter 
 seems the more likely. 
 
 It derives its name of wood-oil from the fact that it is used 
 as a protective coating for wood in China, being used as a sort 
 of varnish. It combines readily with lead and manganese oxides 
 to form driers, and a certain proportion of lead in combination 
 is said to make the film glossy and transparent instead of fiat and 
 opaque. 
 
i?*.r 
 
 &trEsf ;.' / <?t'^ .. . v ^y 
 
CHAPTER Vin. 
 
 JAPANS AND DRIERS. 
 
 THESE terms, japans and driers, are perhaps the most in- 
 definite used in the varnish and paint business. It is commonly 
 known that the Japanese and Chinese make varnishes of peculiar 
 character, with which they make a beautiful glossy coating on 
 articles of various kinds; and at one time, about the middle 
 of the eighteenth century, imitations of this varnish, or var- 
 nishes made to imitate, rather remotely, the surfaces of this 
 sort, were called Japan varnish. One way of doing this work 
 was to put the varnished article into a hot oven and dry the coat- 
 ing from a melted condition, and the kind of varnish useful for 
 this treatment came to be called japan, and the process japan- 
 ning. This is one kind of japan made and used largely at the 
 present day; but it is now almost always spoken of as baking- 
 japan. The term japanning always refers to the use of this 
 article. Another kind of varnish was also used to imitate this 
 effect, and this was a thin liquid, which dried very rapidly and 
 to a hard surface. It was possible to apply many coats of this, 
 which was made to dry very quicky by being highly charged 
 with lead compounds. From this kind of varnish the term japan 
 has come to be applied to a liquid the most conspicuous property 
 of which is its capacity of exceedingly rapid oxidation, brought 
 about by loading it to saturation with lead and manganese com- 
 pounds. These two kinds of japan are therefore as unlike as 
 possible in appearance, composition, and use; and they agree 
 only in perpetuating the record of failure of the European varnish- 
 maker to successfully imitate the products of the country whose 
 name they bear. 
 
 87 
 
88 TECHNOLOGY OF PAINT AND VARNISH. 
 
 The subject of baking-japans will be reserved for a later 
 chapter; the drying- japans and the driers form a class by them- 
 selves. 
 
 Driers. It has already been explained that lead and man- 
 ganese compounds of linseed-oil impart to the oil or varnish 
 in which they are dissolved the property of more rapid oxidation; 
 it may now be added that lead and manganese combine readily 
 with common rosin, or colophony, to form resinates, and that 
 these act in the same way when dissolved in oil or varnish, and 
 that all such preparations are called driers. These compounds 
 are made by heating the oxides of the metals with the oil or 
 resin, and since this compound, which is liquid when hot, is a 
 solid cake when cold, the melted mass is dissolved in turpentine 
 or benzine, usually to a rather thin fluid. Various resins are 
 sometimes put into the kettle with the oil and the oxides, shellac 
 especially being used in this way, and either the lead and manga- 
 nese combine to some extent with the resins and make an oil- 
 soluble compound, or, more likely, the resins which, not having 
 been previously melted, are insoluble in oil are soluble in the 
 compound of oil with lead and manganese; at any rate, a com- 
 pound is made which when diluted with turpentine or benzine 
 possesses some of the qualities of varnish and not only dries 
 quickly itself, but imparts that property to any paint or varnish 
 to which it is added, and these varnish-like driers are called 
 japans. 
 
 Japans. Probably the original difference, if there ever was 
 an original difference, between japans and driers lay in this, 
 that a varnish resin was an ingredient of a japan, but the terms 
 have now become so confused that any sharp separation by 
 definition is impossible. Still there are substances to which 
 the name of japan is given which no one calls driers, and there 
 are driers which no one calls japans. 
 
 The action of driers may be best understood by first describ- 
 ing a different but analogous process, the formation of white 
 lead or carbonate of lead from metallic lead and the carbonic 
 acid of the air. Carbonic acid readily attacks metallic lead, 
 
JAPANS AND DRIERS. 89 
 
 but a very thin film is formed of lead carbonate which protects 
 the metal beneath. The sheet of metallic lead is, therefore, 
 put, loosely rolled, in a jar with a very small quantity of acetic 
 acid. This acid eagerly attacks the lead, forming lead acetate. 
 Carbonic acid is a stronger acid than acetic and it, in turn, attacks 
 the lead acetate, forming lead carbonate, and the acetic acid 
 is set free to attack a fresh quantity of lead, and this process goes 
 on until all the lead is converted. At the close we should theoret- 
 ically have all the acetic acid we began with; in practice some 
 of it evaporates. 
 
 Theory of Driers. Driers act in a similar manner, taking 
 up oxygen from the air and giving it up to the oil. These driers 
 are compounds of lead and manganese, in solution in the oil; 
 these metals have the power of forming two sets of oxygenated 
 compounds, the peroxidized ones having twice as much oxygen 
 as the others. When in linseed-oil they give up half their oxygen 
 to the oil; then, being exposed to the air, they absorb a fresh 
 equivalent of oxygen, which again the oil takes from them; in 
 this way they act as carriers of oxygen from the air to the oil, 
 acting, of course, only when the oil is spread out in a film and 
 exposed to the air. Since the oil is thus converted into a solid 
 dry substance, these agents are called driers. 
 
 Boiled Oil. When oil is treated with a small amount, usually 
 about 2 per cent., of these metallic oxides, it is called boiled oil; 
 a film of paint made with this oil will dry in twenty-four hours, 
 or about one -fifth the time required by a paint made with raw 
 oil. Boiled oil is commonly made by the larger concerns by 
 heating a portion of oil with the lead and manganese oxides 
 until union occurs; this is then added to the larger untreated 
 portion of the oil and thoroughly mixed with it. The term 
 drier is applied to the lead and manganese; it is also used in 
 the paint business to mean the oil-soluble compound of these, 
 diluted with turpentine or other solvent. These preparations 
 are of many kinds. 
 
 Driers ; How Made. The most simple drier is made by heating 
 a gallon of oil with about four pounds of the lead and manganese 
 
90 TECHNOLOGY OF PAINT AND VARNISH. 
 
 oxides in most cases there is a large amount of lead and a small 
 amount of manganese at a high temperature, from 500 to 
 600 F., until combination takes place; the resulting compound, 
 which is black in color, is, while still warm, dissolved in turpen- 
 tine. This high-temperature drier is highly oxidized. A much 
 paler drier may be made by dissolving the lead and manganese 
 in a larger amount of oil at a much lower temperature, and 
 finally diluting with turpentine. This low-temperature drier 
 is less highly oxidized, and driers of this class are believed to 
 exert a less injurious action on paint than do the others, though 
 all driers lessen the durability of the paint in some degree. Oil 
 is often made to dry rapidly by adding some of these made-up 
 driers to the oil, cold; such oil is called "bunghole boiled oil" 
 and is not commonly thought well of; but some of the best 
 authorities believe that such oil, if made with a low-temperature 
 drier, is better than regular boiled oil; and it is a significant 
 fact that many of the ready-mixed-paint manufacturers use raw 
 oil and prepared driers, which they would not do if they thought 
 it bad practice. Such driers as have just been described are 
 pure and of the best quality. They may be cheapened by using 
 rosin instead of oil, or by using rosin-oil to combine with the 
 lead. These are diluted with benzine or a mixture of rosin 
 or rosin-oil and benzine, and the odor of the latter disguised 
 by some highly odoriferous essential oil, such as is obtained by 
 the distillation of wood. Such products are less valuable, but 
 most of the driers on the market are made in this way. The 
 common compounds used for making driers are the oxides, but 
 the acetate of lead and the borate of manganese are also used. 
 These salts are white, and the supposition is that they make 
 pale driers. When they are dissolved by heat in oil the acetic 
 and boric acids are. driven off, as the salts are easily decomposed 
 and the acids are volatile, and there is probably no real advantage 
 in their use. 
 
 Driers Made from Soap. Some years ago there was a great 
 deal of drier made by making first a soda soap of the oil, and 
 decomposing this cold, or nearly so, with an aqueous solution of 
 
JAPANS AND DRIERS. 9 1 
 
 the metallic salts, using the acetate or nitrate of lead and the 
 chloride or sulphate of manganese. These cold-formed metallic 
 soaps were then dissolved at a low heat in suitable solvents which 
 would mix with oil. Great things were expected of these driers, 
 but they have nearly gone out of use. The chemical analysis of 
 a drier is a difficult task, and when the results are obtained they 
 are not of much use. To obtain special effects it is the practice 
 of the makers to mix several driers of different qualities in certain 
 proportions, so that really the best and most intelligent use of 
 driers is an art rather than a science and calls for the knowledge 
 of a specialist. For this reason, the analysis of a drier is of com- 
 paratively little value. To secure the proper drying of a naturally 
 slow-drying paint with the least possible amount of drier, and to 
 get the drier which will have the least deleterious effect on the 
 paint, is a problem which calls not only for a great deal of knowl- 
 edge of the matter, but also for a considerable amount of experi- 
 menting. A factory where such goods are made ought to have a 
 laboratory where hundreds of carefully conducted and recorded 
 experiments may be continually carried on. And when we come 
 to the use of driers in varnish and varnish paints, the intricacy 
 and difficulty of the problems become greatly increased, and even 
 a small gain is often of great value. 
 
 Japans. The term " japan " is also applied to substances 
 which promote the drying of a paint-film. It cannot be said that 
 there is any sharp line of definition between what are called driers 
 and what are called japans, but what we usually apply the latter 
 term to is a liquid which, by itself, dries to a hard film having 
 considerable coherence. This is often produced by the use of 
 some resin in the compound, not common rosin, or colophony, but 
 some of the varnish-resins. Such a compound partakes of the 
 nature of a varnish, and some of the japans, such as those in which 
 colors are ground for coach-painting, are practically varnishes 
 heavily charged with lead and manganese. Such japans would 
 not be called driers; and on the other hand, some of the driers, 
 notably the low-temperature driers, when evaporated leave a 
 greasy metallic soap for a residue, and such a drier would not be 
 
92 TECHNOLOGY OF PAINT AND VARNISH. 
 
 called a japan, but the two classes shade into one another, and 
 some preparations would be called driers by one man and japans 
 by another. A japan always has a drying effect; that is, when 
 added to oil it promotes oxidation in the film. The term "japan" 
 is also applied to a totally different class of preparations, namely, 
 such varnishes as are fused on the surface of metals and other 
 substances by subjecting the coated article to the heat of an oven. 
 These are also called baking-japans, or sometimes baking-enamels, 
 and as they depend on the action of heat to harden them they are 
 commonly made without any driers in them at all. There is not 
 the least resemblance in composition or use between these japans 
 and the other kind. 
 
 Bad Effect of Driers. The danger from the use of driers in 
 paint is this : Where oil without drier dries normally it absorbs a 
 certain amount of oxygen and becomes a stable substance; no 
 further oxidation takes place; but if it contains driers, they act 
 as carriers of oxygen, and although their action is enormously 
 decreased when the film hardens, it does not absolutely cease, and 
 the effect is finally to oxidize the film to such a degree that its 
 toughness is destroyed, so that the painter's saying that the drier 
 burns up the paint is absolutely accurate. Since it is impracti- 
 cable to get along without driers, as no one wishes for a paint 
 which remains wet four to ten days, the paint expert uses all his 
 knowledge and ability to make such a mixture of pigments and 
 such a combination of driers as shall secure the greatest immunity 
 from this result, in many cases with a good deal of success. But 
 the "subject is so intricate that it is impracticable to give rules 
 regarding it. 
 
 Low-temperature Driers. But it may be said that the low- 
 temperature driers, which leave a greasy film when spread by 
 themselves on glass and allowed to dry, are efficient driers in oil 
 when added in small proportions, that is, up to the point where 
 the oil itself is able to take up the lead and manganese contained, 
 and if more of this same drier is added the excess acts as though 
 no oil were present, and makes the film softer and more greasy, 
 that is to say, slower in drying, in proportion to the extra amount 
 
JAPANS AND DRIERS. 93~ 
 
 of drier added. As such driers are made, 5 to 10 per cent, of the 
 liquid drier is as much as should be added to a given measure of 
 oil or oil-paint. 
 
 Self-drying Driers. The high-temperature driers and japans, 
 on the other hand, which may be called self-drying, and which 
 when spread by themselves on glass dry rapidly to a hard film, 
 may be added in any proportion to oil, and the more is added the 
 more rapidly the oil will dry ; and as a corollary, oil may be added 
 to dilute and slow down paints ground in japan or a self -dry ing 
 drier. This is not uncommonly done, in carriage-painting for 
 instance, where the paint is ground to a paste in "grinding- japan.'* 
 
 Grinding- japan. A grinding-japan is in fact a varnish so 
 heavily loaded with lead and manganese that it dries to a hard 
 film almost immediately. This kind of japan must also have 
 the property of mixing with the pigments used by the carriage- 
 painter without chemical action, so that the paint thus made may 
 keep without decomposition for a reasonable length of time, and- 
 must admit of being thinned either with oil, or turpentine, or 
 both. From the fact that japans are mixed frequently with oil s 
 it is not very uncommon for the purchaser to think that the) 
 should mix in any proportions without clouding, that is, without 
 the precipitation of any of the ingredients of the japan. This is, 
 however, not borne out by practice, for the japans which will do 
 this usually contain little or no lead, which is the ingredient which 
 should enormously preponderate in a really good drier, and japans 
 which show a cloud when mixed in small proportion in oil are 
 often those which give satisfaction in use. 
 
 Curdling. This formation of a dark cloud in oil is spoken of 
 by carriage-painters as "curdling" the oil, but no curdy precipi- 
 tate is formed. The real value of a grinding-japan is known 
 only by its practical use. It is easy to make a japan that will 
 not curdle, but none such has come under the observation of the 
 writer which is of much value as a grinding-japan. Another 
 thing which often unnecessarily alarms the purchaser is the de- 
 position of a sediment, or "foots," from a clear or "bright" japan 
 or drier. This, it may be said, is almost qr quite invariably the. 
 
94 TECHNOLOGY OF PAINT AND VARNISH. 
 
 case with driers containing lead if allowed to stand a consider- 
 able time, also of low-temperature manganese driers, and is not 
 to be taken as a bad sign unless it goes on to such a degree that 
 the drying effect of the drier is evidently impaired, which may 
 sometimes be the case with manganese driers. It is probably 
 good practice to avoid carrying a very large stock of driers and 
 japans, which do not improve by age beyond two or three months, 
 and in general it may be said of varnishes that they improve with 
 age for a considerable time, and then do not deteriorate, while 
 paints of all sorts, and especially those ground in varnish and 
 japan, are never so good as when they come fresh from the mill. 
 It is obvious that as the chemical composition and stability of 
 pigments, and especially of those colors called "lakes," vary, it is 
 desirable to use with them such japans and varnishes as will 
 make the most permanent and stable mixtures; this is only to 
 be known by experiment, though, of course, the experience of the 
 manufacturer is a valuable guide in making new mixtures, and so 
 it comes that the business of making these japan colors and var- 
 nish paints is largely in the hands of the varnish- makers, who 
 know most of the actual composition and nature of the materials 
 used. 
 
 The activity of the business of making mineral and lake 
 pigments, which is incessant, leads to the continual improvement 
 (that is, change) of composition, and introduction of new colors, 
 and there is likewise change in varnish materials, especially resins, 
 and processes; so that a considerable proportion of the formulae 
 in use five years ago are now out of date. Even where names 
 are preserved substances change and formulae become mislead- 
 ing. It is but another case where "the letter killeth; the spirit 
 giveth life." 
 
CHAPTER IX. 
 ROSIN. 
 
 COMMON rosin, or colophony, is the residue remaining in 
 a still after the spirit of turpentine has been distilled off from 
 the crude turpentine which is obtained from the pine-tree. It 
 is commonly supposed that this crude turpentine consists of 
 colophony dissolved in spirit of turpentine. If this were so, 
 it should be possible by redissolving the rosin in the essential 
 oil to reproduce the crude turpentine, but this is not possible; 
 that is, it is easy to dissolve the rosin in the spirit of turpentine, 
 but the substance so obtained does not much resemble crude 
 turpentine. 
 
 Spirit- of Turpentine an Artificial Product. The charac- 
 teristic and peculiar odor of spirit of turpentine is almost or 
 quite absent from crude turpentine, and the probability is that 
 the latter is decomposed by the heat in the still, and that the spirit 
 of turpentine and colophony are both products of this decom- 
 position, which is a chemical rather than a physical one, being 
 in this similar to the change which we know takes place when 
 ordinary varnish-resins are melted and decomposed in the varnish- 
 kettle by heat. In the latter case the temperature of the melting 
 and decomposing resin is far higher than that of the vapor given 
 off, thus conclusively proving that the change is chemical and 
 that the liquid which distils off is a product of destructive distil- 
 lation, a fact which we know from other reasons also; and 
 although the writer has not had an opportunity of running a 
 turpentine-still, he is confident that a destructive distillation 
 occurs in it and that rosin, or colophony, and spirit of turpentine 
 are not natural substances, but products of chemical action. 
 
 95 
 
96 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Chemically considered, rosin is an acid substance; it in 
 fact consists mainly of a mixture of organic acids and therefore 
 it has a strong disposition to unite and combine chemically 
 with basic substances, such as soda, potash, lime, etc. It com- 
 bines with soda and potash to form rosin soap, a yellow soap 
 somewhat similar to ordinary tallow soap. This will mix in 
 all proportions with common soap, and as it is not entirely with- 
 out detergent properties and is very cheap, it is largely used as 
 an ingredient, and is commonly spoken of as an adulterant, of 
 laundry soaps. It is well known that the soda and potash com- 
 pounds are soluble in water, but the lime soaps are not, neither 
 are those of the metals, such as manganese ,and lead. These 
 lime and metallic resinates are soluble in oil or turpentine and 
 are used in varnish and driers. The resinates of lead and manga- 
 nese being efficient and cheap driers are very extensively used. 
 They are not as valuable as oil driers, their influence being 
 more deleterious to the durability of whatever they are put in 
 than is the case with oil driers,- and are somewhat unstable com- 
 pounds, which makes them rather unreliable. Rosin will dissolve 
 readily in oil, and a varnish may be made in this way, but such 
 a varnish remains for a long time tacky and never gets very hard, 
 particularly if much rosin is used. 
 
 Rosin Hardened by Lime. It has been found that the 
 addition of from 2 to 10 per cent, of lime to rosin hardens it con- 
 siderably, 5 or 6 per cent, of lime being the quantity most com- 
 monly used; it is added to the melted rosin and quickly combines 
 with it, but a part settles out, it having been found more con- 
 venient and expeditious to add more than will readily combine 
 under the common conditions of heat and time allowed. This 
 hardened rosin may be easily dissolved in oil, and really forms 
 the base of about all the very cheap varnish on the market. A 
 patent, 'which has now expired, for this lime-hardening of rosin 
 was granted, but the process was before that well known to all 
 varnish- makers and, so far as is known to the author, no regard 
 was ever paid to the patent, in this country at least. I am 
 told that it is described in an English book of the eighteenth 
 
ROSIN. 97 
 
 century. As a general rule, when rosin is spoken of by American 
 varnish- makers they refer to this lime-hardened article, which 
 they prepare as they want it. The common practice is to use 
 pulverized quicklime; formerly slacked lime, or calcic hydrate, 
 or a mixture of that and carbonate was used. Varnish may also 
 be made by dissolving rosin, either in its natural state or 
 hardened, in turpentine or benzine, making a product some- 
 what like damar varnish, and this is used to adulterate damar 
 varnish or as a substitute for it; it is also used to adulterate 
 other varnishes. One of the most important uses of rosin var- 
 nish is as an adulterant of regular oleo-resinous varnishes, but a 
 large amount is sold for use without any admixture of the more 
 valuable ingredients. These rosin varnishes are pale in color 
 as a rule, and of a brilliant lustre when recently applied. They 
 are free or nearly so from most of the "tricks" (formation of 
 an uneven and imperfect surface) to which better varnishes 
 are liable, but they qjjp not usually dry to a very hard surface 
 (but much progress has been made in late years in this regard), 
 and they lack durability, especially when exposed to the weather. 
 
 Good Effect in Mixtures. The addition of a very small 
 proportion of rosin varnish to an oleo-resinous varnish often 
 makes it ready for use in a short time. This may be due to 
 two causes, one of which is that the rosin is acid and combines 
 with any of the excessively minute particles of lead or manga- 
 nese which may be floating in the varnish and which would 
 cause flaws and imperfections in its surface; the other that rosin 
 is slow to set and harden and may act in the film as a flux, causing 
 the film to flow more evenly and thus making a more perfect 
 surface. 
 
 It may not be necessary to add, in order to secure these results, 
 more than 3 to 5 per cent, of rosin varnish containing a still smaller 
 per cent, of actual rosin, and this small amount may not be enough 
 to be sensibly deleterious, especially in a varnish of moderate 
 price and ordinary character. As a general rule, the addition 
 of rosin varnish is made in considerable quantity, as it must be 
 to sensibly affect the price, and is an injurious ingredient. 
 
98 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Viscosity of Rosin. Rosin is a brittle solid, easily reduced 
 to a powder, but if we lay a piece of rosin on a board, even in a 
 moderately cool room, it will in time flow out into a flat cake. If 
 we remove the head from a barrel of rosin and lay the barrel 
 on its side, the rosin will in time flow out. It is in fact inter- 
 mediate in its properties between a solid and a liquid, being 
 extremely viscous. It is very easily melted, and as a liquid has 
 unusual solvent qualities; it is a very effective flux. 
 
 This was known to the old varnish- makers, who, as has been 
 seen in the recipes already given, often put a small proportion 
 of it in the kettle in which they were about to melt their resin; 
 by doing so, the regular varnish resin was much more easily 
 melted. Sometimes a little oil was added for the same purpose. 
 It was common to rub the inside of the kettle with oil before 
 putting it on the fire, but rosin is much more effective. 
 
 Used with Asphaltum. Rosin easily dissolves and is dis- 
 solved by the asphaltums when melted, and is a common ingre- 
 dient of asphaltum varnishes and compounds. It adds so 
 greatly to the working qualities of these asphaltum compounds 
 that it is difficult to resist the temptation to put it in, and since 
 most of the asphaltum compounds and varnishes are sold at a 
 low price, and as rosin is the very cheapest thing used in the 
 business, the temptation is twofold. 
 
 Rosin Varnish Cracks. Every one must have observed on old 
 doors and sometimes on old furniture, especially chairs, that the 
 paint is cracked and the cracks have opened to a considerable 
 width, frequently a quarter of an inch, in a reticulated pattern 
 suggestive of alligator-leather. These cracks are at first minute; 
 then the paint or varnish on the interspaces contracts, drawing 
 slowly apart, until the cracks become wide bare strips. In nearly 
 all cases this is due to the use of rosin varnish, either by itself or 
 as a considerable ingredient in a paint. India-rubber as a con- 
 stituent of paint or varnish will act in the same way; but prac- 
 tically it is not in use. If a rosin varnish is made with very little 
 oil, it presents at first a brilliant and glassy surface, because of the 
 high percentage of resinous material, but the air rapidly acts on 
 
ROSIN. 99 
 
 it, possibly because the minute proportion of ammonia in the air 
 (which is much higher indoors than without) chemically attacks 
 the rosin, but also because pure air acts on it as well, and in a short 
 time the lustre is greatly reduced; then it begins to show under a 
 magnifying-glass minute cracks; these grow larger; after a time 
 the whole of the varnish cracks in pieces and comes off. If a 
 considerable amount of oil is used, the lustre is not at first as 
 good, and although it nearly disappears in a comparatively short 
 time, the varnish lasts much longer than the one just described, 
 and it is this sort of varnish (or the first kind mixed with an oil- 
 paint, which has the same effect in increasing the proportion of 
 oil) which shows the wide reticulated cracks spoken of; the 
 rosin varnish which is nearly all rosin usually falls off entirely 
 before the cracks become so wide. 
 
 Rosin may be hardened by zinc oxide, or by white lead, instead 
 of lime, and a rosin "ester" has been made in which the rosin 
 acids are combined with glycerine ; these products are better than 
 the lime-hardened article, but they also cost more and are darker 
 in color, and it soon becomes apparent that a varnish can be made 
 for about the same money out of a cheap Manila or other cheap 
 resin, which will be for actual use worth ten or twenty times as 
 much as the rosin varnish; so that practically the limed rosin is 
 the compound in actual use. Most of the recent writers on the 
 subject have laid stress on the fact that lead and manganese tend 
 to shorten the life of paint and varnish; the writer of this has 
 been as strenuous in insisting on this as anybody; but the fact is 
 that, excepting a small amount of varnish for special and very 
 limited use, all varnishes except rosin contain some lead; the 
 manganese is commonly so small in amount as to escape detection 
 by chemical analysis, though not unimportant in its action ; but 
 the presence of lead in a varnish, being with our present practice 
 unavoidable, is not to be taken as an objection, but rather the 
 contrary, while varnish containing lime may' be confidently re- 
 jected, as being a rosin varnish. The author does not, however, 
 regard the absence of lime as a definite proof of absence of rosin, 
 for evidence is at hand that rosin varnishes are made without 
 
100 TECHNOLOGY OF PAINT AND VARNISH. 
 
 lime, although the writer does not know as yet how they are 
 made; the making of rosin varnishes is quite an industry by 
 itself, and those who are engaged in it undoubtedly have been 
 working out processes and using materials not known to those 
 who are less familiar with that branch of the business. It is not 
 to be supposed that rosin varnishes as a rule do not contain some 
 lead and manganese ; as a rule they do. Rosin is so soft that var- 
 nishes containing it naturally dry slowly, and the makers put in 
 anything which will hasten their drying; but it is possible, and not 
 very uncommon, to make rosin varnish without these driers. 
 
 I cannot refrain from giving an illustration. Some years ago 
 I had occasion to give advice about varnishing the woodwork 
 posts, beams, doors, etc. of a chemical laboratory in one of our 
 universities. As I have spent the greater part of my life in a 
 laboratory and not a little of it in the varnish business, it did not 
 occur to me that I did not know practically how to varnish a 
 laboratory, and I advised using a varnish with about 20 gallons 
 of oil, and made, as nearly as I now recollect, of Kauri, Benguela, 
 and Zanzibar resins. The head professor of chemistry had, how- 
 ever, formed the idea that lead, even in traces, was objectionable, 
 not, however, because of its oxidizing action, but because he 
 feared it would be attacked by sulphuretted hydrogen, which is 
 always present in the air in such a laboratory. Of course all 
 chemists know that it does attack lead, and white-lead paint in 
 a laboratory quickly becomes blackened from the conversion of 
 the carbonate into sulphide ; but in varnish there is very little lead, 
 and what there is is probably so firmly combined that hydrogen 
 sulphide cannot attack it ; and besides all that the fact is that any 
 decent varnish is nearly impermeable to gases after it has become 
 well hardened ; it wastes away from the outer surface, or it cracks 
 from too rapid changes of temperature, or it is thrown off by 
 moisture in the underlying wood, trying in vain to pass through 
 it, but it is not penetrated and decomposed throughout by gases, 
 so that the reasoning which applies to an oil and pigment paint 
 does not bear on the varnish problem; but this was all unknown 
 to the professor of chemistry, a man of much learning and eminent 
 
ROSIN. I0i 
 
 in his own way, and he insisted on having a varnish free from 
 lead. I gave it up, wondering in my own mind what new and 
 unknown star was arising in the varnish world who had solved the 
 problem of making a raw-oil varnish without driers for such use. 
 
 The next time I saw the laboratory I found out. That beau- 
 tiful building had been subjected to the outrage of varnishing it 
 with the meanest kind of a rosin varnish, a cheap and much worse 
 than worthless "hard oil finish," three-fourths of which had 
 decomposed and fallen off, leaving dingy patches of rosin on the 
 blackened surface of the wood. But it had no lead in it, nothing 
 but lime. In the same building the desks, stair-railings, etc.,, 
 which had been bought ready-made from some respectable man- 
 ufacturers, and varnished with a good though not expensive var- 
 nish, were in as good' condition as when bought, ordinary wear 
 excepted. 
 
 Rosin Size. A solution of rosin, without any treatment, in 
 benzine is probably the cheapest varnish in use. I have seen it 
 sold in barrels for nine cents per gallon, f.o.b. cars. It is used 
 for varnishing building-paper and the like, but building-paper is 
 sometimes sized with a rosin size, which is added to the pulp, 
 and a great deal of this size is used for varnishing wall-paper. 
 
 The rosin varnishes are much less impermeable to water than 
 those made from standard varnish-resins, and when a rosin var- 
 nished surface is wet with water it usually turns whito because 
 of the action of the water on the rosin. Many varnishes not con- 
 taining rosin do this also, but not so readily, nor does the water 
 penetrate them so deeply. 
 
 Sponge Test. If we place on a flat horizontal varnished sur- 
 face a wet sponge, and leave it overnight, we shall find in the 
 morning whether the water has acted on it or not. A rosin 
 varnish will be white under the sponge, and frequently it will 
 be dissolved out down to the wood or nearly so, and this white 
 surface will remain white when dry, showing deep corrosion. A 
 better varnish, although it may turn white, will regain its original 
 color on drying, and a varnish made expressly to stand water 
 ought not to be affected. 
 
102 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Rubbing Test. If the reader will rub the varnished surface 
 of a piano or of any good piece of varnished furniture with the 
 ball of the finger, he will find that no effect is produced, except 
 to increase the polish; but if the same thing is done to a surface 
 covered with rosin varnish, the latter can be rubbed off in this 
 way, showing that it is softer and less tough than the better 
 article. 
 
 Rosin varnishes are chiefly used on the woodwork of the 
 cheaper class of houses, on cheap furniture, and on agricultural 
 machinery. They are also used to mix with the better varnishes 
 in order to reduce the price, and there is a great retail-store trade 
 in these goods. Every retail dealer in paint .and varnish keeps 
 two or three barrels of rosin varnish on tap, from which he sells 
 varnish to the house-painters and other people under any name 
 by which they may demand it. It is probable that more rosin 
 varnish is sold than of all the rest put together. It cannot be 
 denied that progress is being made in producing better qualities 
 of these goods, but it does not now seem likely that they will ever 
 equal the varnishes made from the natural resins, either in 
 appearance or durability. 
 
CHAPTER X. 
 
 SPIRIT VARNISHES. 
 
 IF we put some shellac resin, or gum shellac as it is called, 
 in a bottle with somewhat more alcohol than enough to cover it, 
 and let it stand a day or two, occasionally shaking it, the greater 
 part of the resin will dissolve, making shellac varnish. The 
 solution will take place much more promptly if the bottle is 
 placed in a shaking- machine, or attached to a revolving shaft, 
 and the common way of making shellac varnish is to put the 
 components in a revolving barrel or churn, or in a mixer where 
 the materials are agitated by a stirrer. In any case, it is done 
 without the application of heat, and the varnish thus made is 
 a spirit varnish containing no oil, nothing but a resin and a 
 volatile solvent. The part which does not dissolve is a sort of 
 wax, in appearance (when purified) not unlike carnauba wax; 
 this is soluble in benzine, and may be removed from the shellac 
 proper by the use of that solvent, leaving a clear and transparent 
 solution of the pure resin in alcohol. 
 
 When shellac varnish is spread on a surface the alcohol 
 evaporates and the resin, or the mixture of resin and wax, is 
 left as a film of exactly the same composition as the original 
 resin; the office of the alcohol having been to facilitate the 
 mechanical operation of spreading the resin out in a thin film of 
 nearly uniform thickness. This is very different from the action 
 of oil in oleo-resinous varnishes, which not only helps to reduce 
 the resin to a liquid condition, but itself remains as an important 
 and valuable part of the film. Shellac varnish is, therefore, 
 essentially different from those varnishes which have so far been 
 
 103 
 
104 TECHNOLOGY OF PAINT AND VARNISH. 
 
 described. It is the most generally used and the most important 
 of the spirit varnishes. 
 
 Composition of Shellac Varnish. The English and European 
 books on this subject commonly contain formulae for making 
 it with from five to fifteen or twenty parts by weight of alcohol 
 to one part of shellac. This will make a very thin varnish and 
 is not known commercially in this country, where ordinary or 
 standard shellac varnish is made with five pounds of gum shellac 
 to one gallon of 95 or 97 per cent, alcohol, or about one part by 
 weight of shellac to one and one-half parts by weight of alcohol. 
 This makes a varnish of rather heavy body, but one which may 
 be brushed out thin, and will dry quickly. All varnishes should 
 be put on in thin coats, but shellac is remarkable in this respect, 
 for if put on thin it dries very quickly and if put on thick it takes 
 on a waxy consistency and is excessively slow about getting hard. 
 
 Precautions in Using Shellac. One or two thin coats of 
 shellac may be applied and the object put to almost immediate 
 use, but great care should be observed in using more than two 
 coats or this persistently tacky condition may be encountered. 
 As shellac is a varnish very commonly used by amateurs, this is 
 worth remembering. Shellac very easily softens and melts with 
 heat, and if it is used as a first coat on woodwork and an oleo- 
 resinous varnish put over it, the object so coated should not be 
 placed near a fire or in the hot sun, lest the shellac soften and 
 blisters be formed. 
 
 The natural color of shellac is brownish yellow or reddish 
 yellow, and it is commonly spoken of as orange. The different 
 grades are designated by letters, D. C. being the best (the letters 
 are the initials of David Campbell). It is reported, and is prob- 
 ably true, that large quantities of common rosin are shipped to 
 India and used as an adulterant of gum shellac in making the 
 cheap grades. 
 
 Shellac is easily bleached with chlorine, becoming nearly 
 white, and called then white shellac. 
 
 Orange shellac is soluble in 85 per cent, alcohol, but white 
 shellac which is bleached in an alkaline aqueous solution, from 
 
SPIRIT VARNISHES. 105 
 
 which it is recovered by acidifying the solution, contains some 
 water and, perhaps for this reason, requires strong alcohol, 95 
 to 97 per cent., to dissolye it. Some of this water may be re- 
 moved by coarsely powdering the shellac and exposing it on 
 trays to dry air in a warm but not too hot room. 
 
 Insoluble White Shellac. If too much heat be applied, or 
 if the drying operation be too prolonged, the white shellac is 
 very liable to go over into an isomeric state and is then perfectly 
 insoluble. It is, therefore, stored in a cool damp place and 
 when wanted is got into solution with the utmost expedition. 
 Orange shellac requires no such care and may be used even 
 after it has been melted. 
 
 Shellac is not only soluble in common grain-alcohol (ethyl 
 alcohol), but also in wood- alcohol (methyl alcohol), and in some 
 of the other alcohols, but ethyl and methyl alcohols are the ones 
 commonly used. It is readily soluble in ammonia-water, also 
 in aqueous solutions of borax and of the carbonates of soda and 
 potash. 
 
 Alkaline Solutions. The ammonia solution has had some 
 use, especially as a polish for shoes, etc., and the borax solution 
 has some commercial use, especially, I have heard, as a glaze 
 for straw hats. Any of these varnishes may be colored by the 
 addition of a suitable dye or may be made into a varnish paint 
 with a pigment which has no chemical action on the shellac. 
 There are places where shellac is the best varnish that can be 
 used; for instance, nothing equals it for varnishing the wooden 
 patterns from which castings are to be made, and for floors on 
 ships where it is absolutely necessary that they should be ready 
 for use within an hour or two after they are varnished; it is, 
 in fact, used not a little for a floor varnish in houses, but it lacks 
 durability, and in general it is easily destroyed if exposed to the 
 weather. It dries more quickly than any other common varnish 
 and on that account is very useful. 
 
 Damar Varnish. As shellac may be taken as a type of the 
 alcoholic varnishes, so damar may represent that class which has 
 an essential oil as the solvent. Damar varnish is made by dis- 
 
106 TECHNOLOGY OF PAINT AND VARNISH. 
 
 solving damar resin in spirit of turpentine. This may be done 
 cold, in a revolving barrel or churn, or hot in a kettle. If the 
 latter, it is common to dissolve it in a small amount of turpentine, 
 and when it is dissolved thin with the necessary amount of cold 
 turpentine. This lessens the fire risk. It is not a perfect solu- 
 tion, remaining persistently cloudy, an opaque white liquid, 
 becoming more translucent by standing a long time. It dries by 
 the evaporation of the solvent, but, as has been said before, tur- 
 pentine does not wholly evaporate, part of it becoming oxidized 
 and remaining as an elastic resinous ingredient of the film. Damar 
 itself is not a hard resin, but it is very white and the varnish film 
 never becomes very hard (unless by baking), nor is it very dura- 
 ble, even within doors, but its extreme paleness and the ease with 
 which it may be used cause it to be very popular. f cheapen it, 
 benzine is often mixed with the turpentine and rosin with the 
 damar resin ; in fact, not a little is sold under the name of damar, 
 which contains no damar and no turpentine. Mixtures of this 
 sort may be made which will deceive all but the very elect. Per- 
 haps some of these are about as good as the straight damar, which 
 is not a very good varnish anyway; still, the people who use it for 
 fine work, such as fine baking enamels in delicate colors, can tell 
 the difference and not only insist on pure damar, but like that 
 made from selected pieces of resin. There is a general belief 
 that if it is made by the cold process it is better than if made 
 hot. It is usually made by dissolving five or six pounds of 
 damar resin in one gallon (seven and one-fifth pounds) of spirit of 
 turpentine. It should be allowed to settle for sixty days before 
 using. 
 
 Sandarac. Another resin of some importance is sandarac. 
 As has been already frequently stated, this was one of the first 
 known of the resins, and varnishes were made of it perhaps in 
 prehistoric times; certainly in early times. It is soluble in alco- 
 hol (not perfectly), also not very perfectly in spirit of turpentine, 
 with heat in oil, and has been a considerable and frequently the 
 most important ingredient in varnishes of a complex character. 
 It may be observed and the observation really lies at the foun- 
 
SPIRIT VARNISHES. 107 
 
 dation of the art of making spirit varnishes that when a resin is 
 found to be only partially soluble in a liquid, complete solution 
 may be attained by adding some other resin to the mixture; 
 sometimes by adding the dry resin, at others by dissolving the 
 second resin in the same or some other solvent and mixing the 
 solutions. Common rosin, or colophony, is remarkably efficient 
 in this respect, and it is said that Venice turpentine, Burgundy 
 pitch, and the like are also valuable. Sometimes a resinous 
 solution will dry flat, i.e., white and opaque, and the addition of 
 a portion of some other varnish will cure this tendency, making 
 the film full and transparent. Thus the art of making spirit 
 varnishes is one of great complexity, and the writer of this is no 
 more than an amateur in this kind of work. His advice and 
 information to the reader will, therefore, be correspondingly 
 scanty. 
 
 Sandarac, when new and fresh, is of a pale-yellow color, and 
 with age becomes reddish and darker; when applied as a varnish 
 it is left on the surface as a resin and, as would naturally be sup- 
 posed, darkens and becomes red. This has long been known, for 
 it has been used from early times to varnish pictures, and its 
 effect on their colors was a subject of comment among the painters 
 of the middle ages. They usually dissolved it in turpentine and 
 commonly added some other resin to the solution. 
 
 What has been said about sandarac may be applied to mastic : 
 it is only partially soluble in the ordinary solvents; alcohol dis- 
 solves about nine-tenths of it; turpentine is also a common sol- 
 vent for it. It is paler than sandarac and does not redden or 
 darken with age. It is somewhat softer than sandarac. 
 
 Damar, shellac, sandarac, mastic, and common rosin are 
 (except asphaltum, to be spoken of later) the only resins com- 
 monly sold by dealers in varnish resins in this country for mak- 
 ing varnishes of this class, i.e., solutions of resin in volatile sol- 
 vents, without oil. There are many other resins soluble, or partly 
 so, in alcohol or turpentine, which are said to be and probably are 
 used in spirit varnishes, prominent among which are elemi, Venice 
 turpentine, Burgundy pitch, and benzoin; these are to be had 
 
108 . TECHNOLOGY OF PAINT AND VARNISH. 
 
 from importers and dealers in drugs and are by them said to be 
 used in the manufacture of medicinal preparations, plasters, and 
 the like, and toilet articles. Probably a small amount also goes 
 to the spirit-varnish makers, but the market shows that the resins 
 first mentioned are the ones from which nearly all the spirit 
 varnishes are made. There are also a number of tinctorial resins, 
 such as turmeric, gamboge, dragon's blood, annatto, and the like, 
 but the spirit -soluble coal-tar colors have largely displaced them, 
 so that they are hardly worth mention. The opinion of the 
 writer, founded on considerable evidence and some knowledge of 
 the subject, but yet not that of an expert, is that shellac cleared 
 of wax is the foundation for most of the spirit 'varnish, its defects 
 corrected by mastic and sandarac (which latter are also used con- 
 siderably without shellac), and cheapened when necessary with 
 rosin. The solvent is chiefly wood- or grain-alcohol, more fre- 
 quently the former, not only because it is cheaper but because it 
 is better for making the wax-free shellac solution. 
 
 Alcohol will dissolve about 20 per cent, of benzine, and this may 
 sometimes be used to cheapen the mixture, and probably in some 
 cases to increase its solvent power, and a little oleo-resinous var- 
 nish or a little oil may be added in some instances to give certain 
 qualities. There are, of course, other solvents, the most im- 
 portant being coal-tar naphtha, great quantities of which are used 
 in making varnish for ships'-bottom paints; amyl acetate and 
 fusel-oil, which are used in the pyroxylin varnishes, and carbon 
 disulphide, used in certain asphaltum paints; and solvents ob- 
 tained in the fractional distillation of wood-tar are used in var- 
 nishes which are made and used in certain manufacturing opera- 
 tions, but the spirit varnishes of the market are probably of the 
 composition indicated. A considerable quantity is imported, 
 chiefly from France, and it is commonly believed in this country 
 that the French make more spirit varnishes, and know more of 
 them, than do the people of any other country, although they are 
 believed to be deficient in knowledge of the better sorts of the 
 oleo-resinous varnishes. 
 
 Closely allied to the spirit varnishes are some of those made 
 
SPIRIT VARNISHES. 109 
 
 with asphaltum. This is a black or brownish-black resinous 
 mineral, soluble in spirit of turpentine, and when melted mixing 
 in all proportions with linseed-oil, also with melted rosin, and the 
 solutions of it mix readily with the oleo-resinous varnishes. Like 
 rosin, it has considerable effect as a flux; but unlike rosin, the hard 
 varieties are highly permanent and durable, and where the color 
 is not an objection, it- is a valuable ingredient in oleo-resinous 
 varnishes. It has a rather bad name, due to several causes. In 
 the first place, its warm brownish-black translucent color (in a 
 thin film) has always been an attraction to artists, and the artist 
 is too often totally and phenomenally ignorant of the materials, 
 and especially of the vehicles and varnishes, which he uses, but 
 not lacking in confidence. Hence asphaltum dissolved in turpen- 
 tine has been used, and this, especially if -mixed with rosin, is 
 merely a spirit varnish, and is one of the most perishable of var- 
 nishes, because the vehicle evaporates and leaves the asphalt in 
 a thin film, which either immediately or very soon becomes a 
 powder; or, if mixed with rosin, cracks; and in any case is almost 
 certain to partly dissolve or be dissolved in the other paints used 
 on the same work, dissolving and destroying them. For these 
 and other reasons the belief has grown up among artist painters 
 that asphaltum is unstable and in every way dangerous. This is 
 all wrong. 
 
 Stability of Asphaltum. The great painters of the middle 
 ages used asphaltum freely, and in their hands it proved abso- 
 lutely permanent, and Eastlake says that there are no complaints 
 by any of the writers of that period of its flowing or cracking. 
 The reason is that they used it in a true oleo-resinous varnish, 
 which dries too slowly for modern practice, but which is the only 
 way to attain permanence. Another reason for its evil repute is 
 that it has been and is largely used as a cheap black varnish for 
 small (and large) pieces of iron used in the arts and manufac- 
 tures, as an inexpensive temporary finish, keeping them from 
 rusting until they come into the hands of the consumer. The 
 way to make a cheap asphaltum varnish is to melt it with rosin 
 and thin with benzine. The most durable asphaltum is not very 
 
no TECHNOLOGY OF PAINT AND VARNISH. 
 
 black, but brown and translucent as a film, so a softer and blacker 
 material is used, much more opaque but less durable. This is 
 not all. Much cheaper than asphaltum is coal-tar pitch, and a 
 great deal of asphaltum varnish is made of this, which is inferior 
 to asphaltum in every respect, even, unfortunately, in price. Such 
 varnishes are sold for fifteen cents a gallon, perhaps less. On 
 the other hand, if we substitute the best and hardest asphaltum 
 for all or a portion of the varnish resins in an oleo-resinous var- 
 nish, particularly one containing considerable oil, we find that 
 such a varnish is very slow to dry, and if we accelerate the drying 
 by lead and manganese driers, we are liable to add so much drier 
 that the varnish is shortly destroyed by their excess. But if we 
 make such a varnish and resolutely give it time enough to dry, we 
 find it to be a material of the highest excellence. Asphaltum seems 
 to be between soft bituminous coal on the one hand and liquid 
 petroleum on the other. The hardest varieties are the Egyptian 
 and that known as gilsonite, which comes from Utah. These are 
 so hard that they are very brittle, easily powdered, and at ordinary 
 temperatures the pieces have no more tendency to stick together 
 than pieces of coal. Trinidad asphaltum, on the other hand, 
 contains so much mineral oily matter that pieces which are pressed 
 together readily though slowly unite, and if a barrel of it is laid 
 on its side with the head removed the asphalt will in time flow 
 out of the barrel. It has about the consistency of soft rosin. 
 Many intermediate grades are found and also some which are even 
 softer than Trinidad, shading off indeed into heavy petroleum. 
 From some of these heavy mineral oils, notably those from Cali- 
 fornia, a residue from distillation is obtained very much like the 
 natural soft asphalts. 
 
 Maltha. This residue is known as maltha, a Greek name for 
 soft asphaltums, and is of varying consistency, according to the 
 temperature at which the distillation has stopped, and which is 
 varied according to the use to be made of the residue. 
 
 P. & B. Paint. In 1886 a patent was issued to Pearce & 
 Beardsley, two citizens of California, for a paint or varnish made 
 by dissolving this maltha in bisulphide of carbon, a preparation 
 
SPIRIT VARNISHES. 
 
 which attained a considerable degree of popularity under the 
 name of P. & B. paint. Bisulphide of carbon is a volatile 
 liquid which has the singular property of thinning maltha very 
 rapidly, so that a small quantity of it produces as great an effect 
 in making the compound fluid as several times as much spirit of 
 turpentine would have. Hence a varnish can be made in this 
 way which is almost all solid matter, and a much thicker layer 
 can be applied than of any other material. This is in itself an 
 advantage, but it is accompanied with the disadvantages that the 
 compound easily thickens by the spontaneous evaporation of even 
 a small amount of the thinning material, and also that the vapor 
 is highly poisonous and explosive. It has, in spite of these draw- 
 backs,, proved useful for many purposes. All these soft asphalts 
 owe their flexibility to the mineral oily matter which they contain, 
 and retain it if kept in masses of considerable thickness, for exam- 
 ple, in street pavements and the like; but when made into varnish 
 and spread out in a thin film, the ingredient which gives them 
 flexibility is absorbed by and passes off in the air and rain, and 
 the earthy constituent alone is left, without coherence, which 
 becomes a powder and falls off. If we start with a hard asphal- 
 tum like gilsonite, we find it necessary to add to it something to 
 make it coherent and elastic. 
 
 Permanently Elastic Asphaltum Varnish. This may be done 
 by dissolving it in linseed-oil, and this, unlike the mineral oil of 
 the soft asphalt, is permanent, and a film of such a varnish retains 
 its elasticity as well as one made from oil and the best varnish 
 resins. Varnishes may be made in this way of hard asphaltum 
 and hard varnish resins with linseed-oil, which have fine lustre and 
 extraordinary durability. They are usually rather slow to dry, 
 but this is less marked than when asphaltum alone is used with 
 the oil. What is commonly sold as asphaltum varnish is a solu- 
 tion of asphaltum in turpentine or benzine, mixed with a varying 
 amount of quick-drying varnish, usually rosin varnish, but as- 
 phaltum varnishes differ greatly in quality and price. Some- 
 important uses of asphaltum will be described in later chapters. 
 
CHAPTER XI. 
 
 PYROXYLIN VARNISHES. 
 
 IT has long been known that when cotton fibre (or in fact 
 any form of cellulose, as woody fibre in general is called) is 
 immersed in nitric, or, better, in a mixture of nitric and sulphuric 
 acids, for a very short time, and then removed and well washed, 
 it is found to have undergone a chemical change, although its 
 outward appearance is the same as before. One of the most 
 conspicuous things about this change is that while before it was 
 very combustible, afterward it became highly explosive; the 
 explosive thus made is called guncotton. Before nitrating, 
 the cotton or other fibre is insoluble in almost every known 
 liquid; afterward it is easily soluble in various alcoholic and 
 ethereal solvents. Cotton - thus treated is also called pyroxylin, 
 nitrocellulose, and soluble cotton, as well as guncotton, and 
 may be made of a considerable variety of composition, accord- 
 ing as it has been more or less acted on by the acid. A suitable 
 compound of this sort, dissolved in a mixture of ethyl alcohol 
 and ether, is the collodion, or "liquid court-plaster/' of the 
 pharmacists, which, on being applied to wounds, dries almost 
 instantly and forms a film like an artificial skin, which protects 
 from dirt and infection. This is probably the earliest use of a 
 pyroxylin varnish, and is still an important one. 
 
 The commercial use of pyroxylin lacquers for adorning and 
 protecting manufactured articles is a subject of interest and 
 importance. The writer has had no experience with these var- 
 nishes, but is fortunately able to supply the deficiency by the 
 aid of his friend, Mr. E. D. Williams, Superintendent of the 
 Celluloid Zapon Company of Milburn, N. J., the largest and 
 
 112 
 
PYROXYLIN VARNISHES. 
 
 most important manufacturers of these products in this or any 
 other country; hence the reader may accept with confidence the 
 following outline of the subject: 
 
 Collodion. The earliest use in the arts of a pyroxylin var- 
 nish was in the application of collodion to photographic plates; 
 when the wet method of preparing and using such plates was 
 in vogue collodion was an important part of the photographer's 
 outfit; and although dry plates are made without its use, it is 
 more used in photography than ever, as it is now used for making 
 the flexible films used in "Kodak" and other film cameras. 
 
 Kodak Films. For this purpose a methyl- alcohol solution 
 is used. The Eastman Kodak Company is said to make a solu- 
 tion as follows: 97 percent, methyl alcohol, 65 parts; amyl alcohol, 
 25 parts; amyl acetate, 10 parts. To a gallon of this solvent 
 1 6 ounces of pyroxylin is added. This varnish is spread on 
 long glass plates previously coated with a thin solution of paraffin 
 to prevent adhesion. This work must be performed in a room 
 the air of which is as dry as possible, to prevent the hygroscopic 
 wood-alcohol from taking up water. The air is dried by passing 
 it through refrigerating coils, by which means the moisture is 
 precipitated; when the air subsequently rises in temperature 
 it is dry in the sense that it will no longer give up moisture. 
 The films are finally stripped from the glass plates and coated 
 with the sensitive emulsion, thus producing a flexible sensitive 
 plate which will withstand the various chemicals used in photo- 
 graphic developers. A thin solution of pyroxylin in wood- 
 alcohol or other solvents is also often used to flow over the devel- 
 oped negative to protect the gelatine film from being scratched 
 or absorbing moisture. Many photographers use this same 
 solution to varnish their finished pictures. When thus protected, 
 negatives and pictures can be handled with little fear of injury, 
 
 As soon as pyroxylin varnishes came into extensive use for 
 photographic purposes, other uses suggested themselves; but 
 in order to adapt them for use on metals and wood, solvents 
 had to be found which would not dry too quickly or take up 
 moisture from the air and thus cause precipitation of the 
 
H4 TECHNOLOGY OF PAINT AND VARNISH. 
 
 pyroxylin. Among the solvents which were early discovered 
 were nitrobenzole ("oil of mirbane") and acetic ether, both of 
 which were used in conjunction with methyl alcohol, and as the 
 alcohol evaporated first, the resulting film, even though it turned 
 white, would eventually clear up, as the slower-drying solvents 
 remained until after the water had evaporated and redissolved 
 any pyroxylin which might have become precipitated. 
 
 As these mixed solvents had many objectionable qualities, 
 and the demand for a lacquer suitable for polished metallic 
 surfaces increased, a great deal of research work was done to 
 find suitable solvents for nitrocellulose which would dissolve 
 it perfectly and make a lacquei which would dry slowly enough 
 in the air to give a uniformly smooth, clear, transparent film 
 which would not impair the lustre of these polished surfaces 
 and would adhere to them. Camphor and all crystalline sub- 
 stances had to be eliminated, as they would recrystallize on 
 drying and give a dull finish. 
 
 Solvents. Among the solvents which we find mentioned in 
 the early history of the subject are acetone, nitrate of methyl, 
 butyric ether, valeric ether, benzoic ether, formic ether, salicylate 
 of methyl, formate of amyl, acetate of amyl, butyrate of amyl, 
 valerianate of amyl, sebacylic ether, oxalic ether, and amylic 
 ether. Few of these have been found to be of any practical 
 use except the amyl compounds, which are formed by the action 
 of various acids, as formic, acetic, etc., on amyl alcohol (fusel- 
 oil) and distilling in the presence of sulphuric acid. These 
 compound ethers have proved to be exceedingly useful in making 
 pyroxylin varnishes, as they are non-hygroscopic and flow out 
 perfectly, dry readily, and are not injurious to the health of the 
 workmen. Acetate of amyl has been most largely used and 
 is at the present time in such demand for this purpose that the 
 supply in this country and Europe does not nearly reach the 
 'requirements; while a few years ago fusel-oil, from which it is 
 made, was a waste product of the alcohol distilleries, for which 
 it was difficult to find disposal. Unfortunately no practical 
 way has yet been invented for making the amyl compounds 
 
PYROXYLIN VARNISHES. 115 
 
 synthetically, and it is impossible to obtain them except from 
 a by-product; so a shortage is a natural result. 
 
 Cellulose. Another .. important question to decide is what 
 form of cellulose shall be used to give a certain result; many 
 are used, such as cotton, both in the fibre and as cotton waste, 
 etc., straw, pith, flax, paper, ramie, etc.; the choice among these 
 has its own influence; and even the thickness of the fibre will 
 Cause one lot of cotton to entirely disintegrate in tlje acid mixture, 
 while a different fibre will nitrate and remain as strong as the 
 original. 
 
 Nothing but these pyroxylin lacquers has successfully an- 
 swered the requirements of the enormous factories which turn 
 out building hardware, gas and electric fixtures, lamps, all 
 sorts of polished brass, silver and silver-plated articles, all of 
 which easily tarnish and must be protected. 
 
 Colored Lacquers. These lacquers are also colored by dis- 
 solving various dyes in the pyroxylin solution, and are then 
 used for decorating metals and glass; the largest use of these 
 colored lacquers is probably for coloring electric-light bulbs. 
 
 Enamels. Beautiful enamels are also made by grinding 
 pigments in these varnishes; some difficulty is experienced with 
 heavy pigments, which are hard to keep in suspension; but the 
 lighter ones will remain a long time without settling. Velvet 
 blacks are especially used on ornamental metal work; also gray 
 colors are coming into use. 
 
 Resins Used with Pyroxylin. Pyroxylin varnishes are greatly 
 improved for use with the brush by adding to them various resins, 
 such as shellac, manila, sandarac, damar, mastic, tolu, benzoin, 
 etc. These give an increased body to the solution without 
 increasing its viscosity and thus enable us to get a heavier coat- 
 ing without changing the flowing qualities of the varnish. The 
 most serious difficulty experienced with these solutions is due 
 to the fact that most resins contain acids, and these cause the 
 film to decompose so that a polished metallic surface is liable 
 to darken after a week or so, which is a fatal objection. 
 
 Thin Films. The great desire of the pyroxylin-varnish 
 
Ii6 TECHNOLOGY OF PAINT AND VARNISH. 
 
 makers has always been to get an article which could be applied 
 to wood in such a way as to compete with oleo-resinous varnishes 
 and paints; the great difficulty has been that when pyroxylin 
 solution is made up to the consistency of these varnishes, there 
 are only about six ounces of pyroxylin to a gallon of solvent; 
 when the film dries the solvent evaporates, and the amount of 
 solids remaining is so small that there is an exceedingly thin 
 film, thus requiring many applications to get a sufficient covering; 
 while with the oleo-resinous varnishes the contents which become 
 solid on drying amount to three or four (or more) pounds to 
 the gallon and the thickness of the film is correspondingly greater. 
 
 Fillers. The best results in the use of these varnishes on 
 wood have been obtained by using a pyroxylin solution for a 
 filler which lays the grain of the wood exceptionally well, then 
 applying an oleo-resinous varnish over this for body, and finally 
 a finishing coat of pyroxylin varnish for hardness. This method 
 of procedure has been used very extensively in finishing pencils, 
 penholders, rulers, hair-brushes, and all sorts of small wood 
 articles. Oleo-resinous varnishes require either long drying or 
 baking, while the quick drying of the solvents makes the pyroxylin 
 lacquers more desirable for some of this work, especially as they 
 produce a surface of unusual hardness and durability. 
 
 Thinness of film, i.e., a lack of a sufficient amount of binding 
 material, prevents making paints for ordinary use; but 10 per 
 cent., or thereabouts, of pyroxylin solutions has been added to 
 linseed-oil paints with good results, and many large paint manu- 
 facturers are experimenting on this line. 
 
 Artificial Leather. Great interest has been manifested in 
 the problem of applying pyroxylin solutions to leather to avoid 
 cracking the enamel, which is so great a disadvantage of the 
 ordinary patent-leather finish. Every patent-leather maker in 
 the country has recently been working on this question, as rumors 
 have been rife that wonderful results have been obtained. As 
 this material has been used for years on cloth to make a flexible 
 coating which will not crack or deteriorate, there seems to be 
 no reason why it should not be applied with advantage to leather; 
 
PYROXYLIN VARNISHES. 1 17 
 
 but as yet no satisfactory results have been obtained. It probably 
 must be compounded with various fixed oils to give it sufficient 
 flexibility, as is done in the enamelled-cloth industries. In this 
 last-named work very beautiful results have been reached by 
 embossing the coated cloth with all sorts of ornamental designs 
 and then embellishing these figures with various colors; such 
 products are used for wall decoration and similar uses. 
 
 One of the best-known uses of pyroxylin lacquers is its use 
 as a medium for applying bronze and aluminum powders; amyl 
 acetate, which is the chief solvent, has a pungent odor resembling 
 bananas, hence the lacquer used for these bronze and aluminum 
 paints has the trade name of "banana liquid." In this way 
 the use of pyroxylin varnish is becoming generally familiar. 
 
CHAPTER XII. 
 
 OIL PAINTS AND PAINTS IN JAPAN. 
 
 PAINT has been used for decorative purposes from prehistoric 
 times, and is so used at the present day by all savages as well 
 as all civilized races. That which makes paint decorative is 
 its color, and this comes from the pigment which it contains. 
 Pigments are solid substances, insoluble in the oil or other liquid 
 which forms the fluid part of the paint (and which is technically 
 called the "vehicle"), and are in the form of a fine powder, 
 usually reduced to the desired fineness by grinding, but some- 
 times, as in the case of lampblack, chemically deposited in a 
 form so finely comminuted as to satisfy the needs of the paint 
 manufacturer. 
 
 Fineness. In general pigments should be so fine that they 
 will pass through a brass wire sieve having two hundred meshes 
 to the linear inch; for some uses pigments may answer which 
 are not so fine, but in any case should pass through a screen of 
 one hundred meshes to the linear inch. In preparing these, 
 the substances of which they are to be made are ground in burr- 
 stone mills, sometimes dry, sometimes mixed with water; in the 
 latter case, they may be sifted wet, but more commonly are 
 dried, crushed, and bolted. The bolting process is also applied 
 to dry ground pigments. But for cheap paints it is assumed to 
 be safe to determine by trial how the mills should be arranged 
 and then put the material through and use it as it comes from 
 the mill without any preliminary sifting or bolting. The paint 
 manufacturer who buys the prepared pigment has his own 
 methods of testing for fineness ; the most common thing is to rub 
 
 118 
 
OIL PAINTS AND PAINTS IN JAPAN. H9 
 
 it on a glass or porcelain plate with a palette-knife side by side 
 with a standard article. Practically nearly all selection of pig- 
 ments is by testing them against standard articles, chemical 
 analysis being only occasionally resorted to, and then for impur- 
 ities in well-known chemical substances, such as white lead. 
 
 It is not the purpose of the writer to go into any elaborate 
 account of the various pigments because there are now books 
 devoted to that subject which treat it more fully and with greater 
 knowledge than he can. But the action of pigments on the 
 vehicles or liquids in which they are mixed is a proper subject 
 to consider here, and while it cannot be discussed in a very 
 thorough manner, it is desired to say something about it, and 
 it is desirable to first say something about the most common 
 and important pigments. All very light colors have white as 
 their foundation or principal ingredient, and white pigments 
 are limited in number to a few substances, the chief being white 
 lead and white zinc. 
 
 White Lead. White lead, when made by what is known as V/ 
 the Dutch process, as most of it is, consists of a mixture of two 
 or three parts of carbonate and one part of hydrate of lead. It 
 is made from metallic lead, which is cast into plates of irregular 
 form, a few inches in diameter, termed " buckles," which are 
 suspended in earthern jars over dilute acetic acid and kept in a 
 warm place where they will be exposed to air containing a large 
 amount of carbonic acid, usually by burying the jars in ferment- 
 ing tan-bark. The acid attacks the lead, forming acetate of 
 lead ; this is decomposed by the carbonic acid, making carbonate, 
 and the acetic acid set free attacks a fresh portion of metallic 
 lead, and so on. The Bolognese MS., written early in the 
 fifteenth century, gives the following formula: "Take lead in 
 plates and suspend them over the vapor of very strong vinegar 
 in a vase, which after being luted must be placed in dung for 
 two months, then scrape away the matter that you will find upon 
 the plates, which is the white lead. Do this until the plates 
 are consumed." So that the process has remained unchanged 
 at least five hundred years, perhaps five times that. In fact, an 
 
120 TECHNOLOGY OF PAINT AND VARNISH. 
 
 almost identical formula is given by Dioscorides, in the first 
 century B.C. 
 
 Sulphate of Lead. There is some white lead made of a 
 different composition, namely, the sulphate. This is used es- 
 pecially as a filler or surfacing material for fine cardboard, as 
 it does not discolor with the heat of the calendering- rolls. White 
 lead as commonly made is not chemically an extremely stable 
 compound. The carbonates are all rather easily decomposed, 
 and the hydrate is in a form which will unite with acid substances 
 with great readiness. Owing to this, we find that in time (not 
 very rapidly) it combines with linseed-oil and more rapidly with 
 varnishes, some of which contain a little acid. Like all the 
 lead compounds, it is of high specific gravity, and a larger amount 
 by weight of white lead than of any other pigment can be com- 
 bined with a given weight of oil. 
 
 Paste White Lead. It is sometimes sold as a dry powder, 
 but. more commonly ground with 10 per cent, of its weight of 
 raw oil as white- lead paste. It is generally believed that if it 
 has once been dried it cannot then be made into as fine a paint 
 as when mixed with oil to a paste in the first place; for it has 
 been found that white lead wet with water, in which form it comes 
 from the washing-vats where the acetic acid, etc., are removed, 
 can be put into a steam-heated agitator or mixer with some oil, 
 and the oil will displace the water, because there is more attrac- 
 tion between the lead and oil than between the lead and water; 
 hence we find traces of water in paste lead. 
 
 White Zinc. White zinc is the oxide of zinc, and is made in 
 metallurgical works by burning zinc in air. It is not inferior 
 in whiteness to white lead in fact it is commonly thought to 
 be whiter but it is not so opaque, and more coats of zinc paint 
 are necessary to get a given effect over a dark background then 
 of lead. It is not very readily attacked by the acids in linseed- 
 oil, but both lead and zinc are to some extent so affected. 
 
 Lithopone. Another white paint containing zinc is known 
 by the trade name of lithopone; it is essentially the sulphide 
 of zinc mixed with a variable percentage of barytes. White 
 
OIL PAINTS AND PAINTS IN JAPAN. 121 
 
 lead and white zinc are practically the only white pigments used 
 in oil or varnish ; other white powders, such as powdered gypsum 
 (sold under the name of terra alba), whiting (which is powdered 
 chalk carbonate of lime), kaolin, and barytes, are used as 
 adulterants, though they are actually pigments of value in paints 
 ground in watery vehicles. The reason is that they are in their 
 nature transparent and appear white just as glass ground to 
 a powder does, but f when mixed with oil the refractive index of 
 the oil is nearly that of those pigments and so they become trans- 
 parent again. Watery vehicles, such as are used in water-colors, 
 fresco paints, and kalsomine, evaporate and leave them to show 
 their power of reflecting white light. So that whiting, which 
 was a favorite pigment with the ancient painters, who used a 
 watery solution of glue, or of albumen, as vehicle, is of very little 
 value to the oil painter, and it is, moreover, an alkaline substance 
 which attacks and after a time destroys the oil. Barytes is 
 perfectly neutral; it is sulphate of barium, a most unchangeable 
 salt. When chemically precipitated it is known as blanc fixe, 
 and this is made as a by-product in some chemical factories; 
 being amorphous while ordinary barytes is crystalline and 
 extremely fine, it is somewhat better than any of the other adul- 
 terants, and possibly has a little value of its own. 
 
 Barium Sulphate and Carbonate. Barium carbonate is also 
 used as an adulterant; it has an advantage over the use of the 
 sulphate in that it is soluble in the same acids which dissolve 
 lead carbonate and is on that account liable to be overlooked 
 in a chemical analysis ; if fraud is designed, it is, therefore, more 
 likely to escape notice, and it is here mentioned that analysts 
 may look for it. 
 
 Value of White Under-body. These white pigments, zinc 
 and lead, are the base of all light -colored paints, for it is impos- 
 sible to make a light -colored paint out of dark-colored materials. 
 They are also used to make a white foundation on which other 
 colors are overlaid. This is a practice of great antiquity and 
 is followed not only in the painting done by artists but also in 
 not a little technical work, using somewhat transparent colors 
 
122 TECHNOLOGY OF PAINT AND VARNISH. 
 
 over the white, which then serves as a sort of mirror, reflecting 
 the light which penetrates to it outward through the translucent 
 outer coat again, and thus producing a warm and brilliant effect 
 to be had in no other way. Eastlake says that "it is an important 
 fact in painting that a light, warm color, passed in a semi-trans- 
 parent state over a dark one produces a cold, bluish hue, while 
 the operation reversed produces extreme warmth. The secret 
 of Van Eyck and his contemporaries is always assumed to con- 
 sist in the vehicle he employed, but a far more important con- 
 dition of the splendor in the works of those masters was the 
 careful preservation of internal light by painting thinly, but 
 ultimately with great force, on white grounds." This is not a 
 new observation, though so true and important as to bear repeat- 
 ing. Aristotle made the same remark: "White surfaces, as a 
 ground for colors, have the effect of making the pigments appear 
 in greater splendor." Again Aristotle says ("De Sensu et Sen- 
 sibi"): "Another mode in which the effect of colors is exhibited is 
 when they appear through each other, as painters employ them 
 when they glaze a color over a lighter one, just as the sun, which 
 is iii itself white, assumes a red color when seen through darkness 
 and smoke. This operation also ensures a variety of colors, for 
 there will be a certain ratio between those which are on the sur- 
 face and those which are in depth." Compare this with Leonardo 
 Da Vinci, on Painting, Chapter CCXXXIII: "When a trans- 
 parent color is laid upon another of a different nature, it produces 
 a mixed color, different from either of the simple ones which 
 compose it. This is observed in the smoke coming out of a 
 chimney, which, when passing before the black soot, appears 
 bluish, but as it ascends against the blue of the sky it changes 
 its appearance into a reddish brown." It might be inferred 
 that Leonardo had read Aristotle, and no doubt he had, for he 
 was a man of much learning and not only one of the greatest 
 painters but also one of the greatest men who ever painted; but 
 it is to be observed that not only the foregoing, but about every 
 other important theorem on the subject, may be found in his 
 book. In regard to the same thing Pliny (1. xxxv, c. 18) says of 
 
OIL PAINTS AND PAINTS IN JAPAN. .123 
 
 Apelles: "No one was able to imitate one thing in that he spread 
 the varnish over his completed work so thin that it brought out 
 the brilliancy of the colors by reflection and protected it from 
 dust and dirt. It seemed to the beholder to be directly from 
 the hand of the artist. And this with good reason, for the bril- 
 liancy of the color could not offend the keenest eye, just like 
 looking through a piece of mica from a distance, and this thing 
 secretly gave darkness to the too-bright colors." 
 
 So it appears that there are both artistic and traditional 
 reasons for the very general use of white (especially white lead) 
 as a priming coat, and perhaps the tradition is a strong reason 
 for the general belief in it, especially when its color will finally 
 be of no effect. 
 
 Importance of Fine Grinding. In this connection it should 
 be pointed out that when it is desired to secure this brilliancy 
 by superimposing colors on a light ground, their clearness must 
 be greatly enhanced by having the pigments ground to the last 
 degree of fineness. This was well known to the great masters 
 in painting, who had them ground most carefully in their own 
 laboratories. Cennini (ch. 36) says: "To grind properly, pro- 
 cure a slab of porphyry which is strong and firm. There are 
 many kinds of stone for grinding colors, as porphyry, serpentine, 
 and marble. The serpentine is a soft stone, and is not good; 
 marble is worse, that is, softer; porphyry is the best of all, and 
 if you procure a slab very well polished, it will be better than 
 one with less polish. Take another stone, also of porphyry, 
 smooth on one side, and raised on the other, in the shape of a 
 porringer and half the height of one, of such a form that the 
 hand may hold and guide it at pleasure. Then take some of 
 the color and put it on the slab, and with that stone which you 
 hold in your hand break the pigment into small pieces. Put 
 some clean water, either from a river, a fountain, or a well, to 
 the color and grind it well for half an hour, or an hour, or as 
 long as you please; but know that if you were to grind it for 
 a year, so much the better would be the color. Then take a 
 flat piece of wood, part of which is pared thin like the blade of 
 
124 TECHNOLOGY OF PAINT AND VARNISH. 
 
 a knife, and with this blade collect the color neatly; keep it 
 liquid and not too dry, that it may flow well on the stone and 
 be thoroughly ground; then collect it carefully. Put it then 
 into a small vase and pour water on it till the vase is full, and 
 in this manner keep it always soft and well covered from the 
 dust, and from all other dirt, that is, in a little box adapted to 
 hold vessels of liquor." Again, when speaking of vermilion, he 
 says: "Put this then upon the slab above mentioned, grinding 
 it with clean water as much as you can if you were to grind 
 it for twenty years, it would be but the better and more perfect." 
 No care was too great for the proper mechanical preparation 
 of pigments, in his opinion; note the use of the wooden palette- 
 knife, to avoid contact with iron a very general precaution. 
 And after giving long and elaborate directions for preparing 
 ultramarine (the natural, not the artificial), he adds: "You 
 must know also that it (the care of preparation) is rather the 
 acquirement of youth than that of men, because they remain 
 continually in the house, and their hands are more delicate. 
 Beware especially of preparing it in old age." Again and again 
 he insists on having the best materials; thus in ch. 96: "It is 
 usual to adorn walls with gilded tin, because it is less expensive 
 than gold. Nevertheless, I give you this advice, that you en- 
 deavor always to use fine gold and good colors, particularly in 
 painting representations of Our Lady. And if you say that a 
 poor person cannot afford the expense, I answer that if you work 
 well (and give sufficient time to your work) and paint with good 
 colors, you will acquire so much fame that from a poor person 
 you will become a rich one, and your name will stand so high 
 for using good colors that if some masters receive a ducat for 
 painting one figure, you will certainly be offered two, and your 
 wishes will be fulfilled; according to the old proverb, good work 
 good pay. And even should you not be well paid, God and Our 
 Lady will reward you soul and body for it." Such are the 
 opinions set down in the oldest treastise on painting; though six 
 centuries old, they are worthy of remembrance. 
 
 Chrome Yellow. The more important of the yellow pig- 
 
OIL PAINTS AND PAINTS IN JAPAN. 125- 
 
 ments are chrome yellow and cadmium yellow. The chrome 
 yellows are made in three shades, pale, medium, and deep. Of 
 these the latter is, or,, should be, pure chromate of lead. It is 
 orange in color. The medium chrome is the same with some 
 carbonate or sulphate of lead, and the pale has still more of 
 the carbonate or sulphate. The chromate is a chemical pre- 
 cipitate, and in making the lighter shades carbonate or sulphate 
 of lead is precipitated at the same instant, thus securing a more 
 perfect mixture than can otherwise be had, and more brilliant 
 color. The chrome yellows when exposed to the weather are 
 somewhat inclined to fade, but they are colors of great beauty 
 and are very opaque. Some of the ochres are yellow also, but 
 not so pure a color; they are, however, permanent, and are 
 extensively used, especially in mixtures. Cadmium yellow is 
 both brilliant and permanent, and is an excellent paint where 
 the cost does not prevent its use; but it is expensive. The 
 chromate of strontium is a pale yellow of great brilliancy, but 
 transparent, so that it can be used only as a glazing color, usually 
 over chrome yellow; it is of the highest degree of permanence. 
 Yellow is not infrequently added to dark colors to give them 
 a warm tone, and is often present in considerable amount where 
 the untrained eye does not detect it at all. It has a most agree- 
 able effect in these mixtures. 
 
 Chrome Green. The most important green is chrome green,, 
 which is a mixture of chrome yellow and Prussian blue, the 
 latter being chemically a ferrocyanide of iron. Each of these 
 pigments separately has great "body" or opacity, and their 
 mixture is unsurpassed in this respect except by some of the 
 blacks. The different shades of this color are made in the same 
 way as the chrome yellows. 
 
 Paris Green. A much more transparent color, but of extra- 
 ordinary brilliancy, is Paris green, as it is called in this country, 
 known as emerald-green in England, and by various names in 
 Germany. It is an aceto-arsenite of copper, and not a very 
 satisfactory paint, but it is of unequalled color, which insures, 
 a considerable use. 
 
126 TECHNOLOGY OP PAINT AND VARNISH. 
 
 Chrome-oxide Green. There is another kind of chrome 
 green, namely, the green oxide, which is prepared both in the 
 hydrated and the anhydrous state, the latter being preferred 
 on all accounts. It is one of the most permanent and indestruc- 
 tible of colors, and is quite opaque, but rather dull in color. It 
 is often said that this is the only pigment to which the name 
 of chrome green should be applied, but in fact the name is ap- 
 propriated commercially by the chrome-yellow-Prussian-blue 
 compound, and in this country, at least, it has been found prudent 
 to designate the other as chrome-oxide green. It is rather expen- 
 sive and not brilliant in color, but of a color which, though rather 
 cold, is considerably liked. It is a very valuable pigment. Zinc 
 green and cobalt green are the same, a compound of zinc and 
 cobalt, of fine color and extreme permanence. Its cost is the 
 only objection to it. 
 
 Blue Pigments. Only two or three blue pigments are in 
 common use : Prussian or Chinese blue, a chemically prepared 
 ferrocyanide of iron, a dark blue pigment, quite opaque, not 
 extremely permanent; and ultramarine, a color originally had 
 from a mineral lapis lazuli but now made artificially in great 
 quantities. This is moderately permanent, not very deep in 
 color, and constitutes most of the blue used in ordinary paints. 
 In one respect it is an exception to a general rule, in that it is 
 not improved but rather injured by excessive grinding. It is 
 as though the color were on the outside of the particles as they 
 come from the ultramarine manufactory and as if, on grinding, 
 these particles were broken up and the color injured by bringing 
 into view the interior portions of the particles. 
 
 Cobalt blue is a compound of cobalt and alumina, a fine 
 color of the highest permanence, but rather costly. It is used 
 to some extent for high-class work, but is rather to be regarded 
 as an artist's color. 
 
 Vermilion. No doubt the most important of the red pig- 
 ments are the iron oxides, but as these . are not pure in color, 
 we may first mention vermilion, which is an artificial sulphide 
 of mercury, of a beautiful scarlet color; it has always been, in 
 
OIL PAINTS AND PAINTS IN JAPAN. 127 
 
 spite of its rather high price, a favorite pigment; it is not very 
 permanent. It is known in this country as English vermilion, 
 most of it being imported from England; formerly it was called 
 Chinese vermilion but that which comes from China does not 
 appear to be equal to the English. What is known as American 
 vermilion is made by precipitating red coal-tar colors on red 
 /lead, orange lead, or barytes, or on sulphate or carbonate of 
 lead, and there are a large number of reds used in the paint 
 trade which are made from the coal-tar dyes, some of which, 
 unlike American vermilion, are very fast to light, but they are 
 not of great opacity, being rather to be classed as lakes. It 
 may be remarked for the benefit of such readers as are not 
 familiar with these matters that lakes are compounds of the 
 coloring matters of dyes with a mineral substance, such as lead 
 or alumina; one of the best known being carmine, made from 
 cochineal, certainly the most beautiful red color that has ever 
 been seen and which is used in painting, especially in carriage - 
 painting, almost as much as ever, in spite of the fact that it is 
 not permanent. 
 
 Red lead is also used, but the consideration of this substance 
 will be deferred to a later chapter, since it is chiefly used as a 
 protective paint for iron and steel. The iron oxides are also so 
 used, but their chief use is in making cheap paints for wooden 
 surfaces, for which they are well adapted. Most of them are 
 quite permanent in color ; and though dull, they are of rather 
 pleasing colors, and have great covering power or opacity. There 
 are essentially two kinds of iron oxides, the anhydrous sesquioxide 
 and the same hydrated. They exist in nature, the first as the 
 mineral called hematite, the second as limonite. The former 
 when powdered is dark red, the latter yellowish red. There 
 are indeed other oxides of iron, notably the magnetic oxide, 
 which is black in color, but it is not used as a pigment. 
 
 Hematite occurs pure in large deposits, and is worked for 
 the manufacture of iron; .the same is true of limonite. Hematite 
 is, when a compact rock, hard and tough, and it is difficult to 
 redv.ce it to such a degree of fineness as will be suitable for a 
 
128 TECHNOLOGY OF PAINT AND VARNISH. 
 
 pigment; the deposits of this ore which are softer and less com- 
 pact are almost always mixed with limonite. The latter is 
 more easily worked than the former and is also more abundant. 
 The great supplies of iron-oxide paints are mixtures of these, 
 and are found in deposits where the ore is in granular or earthy 
 form, usually mixed with more or less clay; sometimes the clay 
 amounts to two-thirds the weight of the whole, not uncommonly 
 one-half. Such a material is easily reduced to a powder; it 
 is roasted in furnaces to drive off the moisture and to develop 
 a color, then ground dry. The author once operated one of 
 these mines; though it was of exceptional character, a short 
 description of the work may be of interest. 
 
 Iron Oxides. The ore was ferrous carbonate, which had 
 been brought to the surface by chalybeate springs and deposited 
 In beds which were overlaid by a deposit of peat, the reducing 
 .action of which preserved the ferrous carbonate from oxidation. 
 It was consequently a natural chemical precipitate and of extreme 
 fineness as well as purity. When this carbonate of iron, which 
 was nearly white in color, was exposed to the air it was rapidly 
 oxidized into the ferric compound; it was put while still moist 
 into a roasting-furnace, where it was heated in contact with air 
 and the carbonic acid driven off; the residue being, of course, 
 ferric oxide. By varying the heat and the amount of air different 
 colors were obtained, from a fine yellowish red to a dark purple, 
 the latter being the pigment known as crocus. The deep, strong 
 red of Indian red was to be seen and the dull brown of ordinary 
 oxide paint. These colors were all to be seen in the same charge, 
 some lumps being of one color and some another; the whole 
 was run through a mill, not to really grind it, for it was too fine 
 for that, but to crush the agglutinated lumps, and it came out a 
 mixture of tolerably uniform color, whose homogeneous appear- 
 ance never would suggest the fact, so obvious to the operator, 
 that it was composed of oxides of many different degrees of 
 hydration and perhaps of oxidation. The lesson to be learned 
 is that it is impossible to tell from the looks of such a paint what 
 it is made of, and that it is not impossible for a paint containing 
 
OIL PAINTS AND PAINTS IN JAPAN. 129 
 
 a large percentage of iron oxides to have other and deleterious 
 ingredients, since the strong and dominating quality of the oxide 
 may overshadow and conceal everything else. This is without 
 doubt a considerable reason for the difference of opinion, about 
 the value of oxide paints, which exists. The greater part of 
 these paints in this country is used for painting freight cars; 
 not a little of the finer qualities, such as those oxides known 
 as Indian and Tuscan reds, for house-painting and passenger- 
 cars. Quite a large amount is also used on steel bridges, chiefly 
 in the Western States, but its use for this purpose is less than 
 formerly. 
 
 A large amount of the better grades of iron oxides for paint 
 is imported from England and Germany. These are made, 
 not from minerals, but as by-products in chemical work, one of 
 the most common being the oxide left from the distillation of 
 sulphate of iron in making fuming sulphuric acid. The cheapest 
 way to dispose of this is to mix it with powdered chalk, or with 
 milk of lime, to absorb the sulphuric acid remaining in it, which 
 is thus converted into sulphate of lime. The pigment known as 
 Venetian red is made in this way and contains a large percentage 
 of sulphate of lime. Reds may also be made by washing and 
 roasting these residues, and some of these are of excellent quality. 
 No colors are more permanent than some of these pure oxides. 
 They have lasted for thousands of years and there is no reason 
 why they should ever change, except when they are subjected 
 to somewhat unusual chemical action. Such a statement does 
 not, however, apply to the impure oxides and especially it does 
 not apply to the impure hydrated oxide. It does apply to the 
 pure anhydrous and sometimes to the partially hydrated oxide 
 when used as a paint on wood or some neutral base, and pro- 
 tected either by its situation or by oil and varnish from access 
 of corrosive gases or liquids. Under such conditions, as, for 
 instance, on the walls of houses at Pompeii, it seems absolutely 
 permanent, keeping its brilliant color; but although it is a native 
 mineral and it is evident from the grea': quantities which are 
 found that it is a compound of great stability, it should not be 
 
130 TECHNOLOGY OF PAINT AND VARNISH. 
 
 assumed to be absolutely the most stable compound of iron, 
 incapable on that account of change, as we may think is the 
 case with barytes, for instance. 
 
 Iron Oxides not Absolutely Permanent. So accurate and 
 conservative an authority as Watt's Dictionary of Chemistry 
 says, speaking not of the comparatively unstable hydrate, but of 
 the anhydrous sesquioxide, that "even at ordinary temperatures 
 it frequently acts as an oxidizing agent in contact with organic 
 matter, and is thereby reduced to magnetic oxide, or even to 
 ferrous oxide, and then, by taking up carbonic acid, converted 
 into spathic iron; the reduced oxide, if in contact with moisture, 
 is frequently also reconverted into ferric hydrate by atmospheric 
 oxidation. The oxide is also sometimes further reduced by the 
 action of sulphydric acid and converted into pyrites." 
 
 The same authority also says of the hydrated sesquioxide 
 that it " easily gives up part of its oxygen to oxidable bodies 
 and is easily reduced by sulphurous acid, etc. In contact with 
 putrefying organic bodies, out of contact with air, it forms ferroso- 
 ferric compounds, or ferrous carbonate, but if the air has access 
 to it, it quickly recovers the oxygen which it has given up, and 
 can then again exert an oxidizing action, thus acting as a carrier 
 of oxygen from the air to the organic body ; hence it accelerates 
 the oxidation of woody fibre in the soil." 
 
 It is evident from the foregoing that, although, as has been 
 said, under favorable conditions some of these oxides are among 
 the most permanent of paints, their value depends on the con- 
 ditions under which they are used. It is also not to be forgotten 
 that when we speak of permanence in a paint we, perhaps uncon- 
 sciously, assume the standard to be the paintings on canvas or 
 the fresco painting on the interior walls of churches and the like, 
 in all which cases the paint has been most carefully preserved 
 and under favorable conditions. 
 
 The relative values of paints exposed to the weather might 
 be quite different; in fact, such is the universal experience. 
 
 There is, however, no reasonable doubt that some of the 
 iron oxides are valuable paints. Some of them are prepared 
 
OIL PAINTS AND PAINTS IN JAPAN. 131 
 
 from deposits of iron oxide mixed with clay, what might be 
 called an iron-bearing clay if we remember that the iron is prob- 
 ably present, not in chemical combination with the clay, but as 
 intermixed oxide; in these deposits the iron is in a finely com- 
 minuted condition, and these ores are easily worked and easily 
 ground, and the resulting pigment is much less liable to rapid 
 settling out of the oil or other vehicle than is the heavier pure 
 oxide. It is possible that some of these clays may be so roasted 
 as to become, like brick-dust, incapable of uniting with water; 
 but if not, they obviously are a source of weakness, and in all 
 cases are to be regarded with a reasonable amount of suspicion. 
 There is, indeed, reason for suspicion of cheap materials of every 
 sort, not because cheapness is an objection, for, of course, it 
 is not so, but in fact a merit, but because it is apt to blind the 
 eyes of the purchaser to such defects as the material may really 
 have. 
 
 Iron oxides are also important constituents of some of the 
 brown pigments, the most important of which is the earthy 
 material called sienna, from the Italian locality whence it is 
 obtained. This is of a beautiful red-brown, and is the pigment 
 used to make stains to match mahogany. Umber is a much 
 darker earth; both are still further darkened by roasting, when 
 they are known as burnt sienna and burnt umber. Both are 
 said to contain some oxide of manganese, and umber contains 
 enough to enable it to impart a decided drying quality to oil. 
 
 Bone- and Ivory-black. The black pigments are various 
 forms of carbon. Bone-black or ivory-black, lampblack, and 
 graphite are the principal sorts. Bone-black is made by calcin- 
 ing bones without access of air; the organic matter contained 
 is decomposed and the oxygen and hydrogen are mostly driven 
 off, the carbon being left with the phosphate and carbonate of 
 lime of the bone. Ivory-black is made in the same way from 
 ivory chips; but probably most of the ivory-black now sold is 
 a fine grade of bone-black. This contains about 10 or 12 per 
 cent, of carbon, to which it owes its color, 3 or 4 per cent, of 
 carbonate, and the remainder, phosphate of lime. It is a brownish 
 
132 TECHNOLOGY OF PAINT AND VARNISH. 
 
 black, the brown color being partly, at least, due to organic com- 
 pounds formed during the roasting, which were too stable to 
 be driven off at the temperature. These may be, to a considerable 
 degree, dissolved out by a solution of caustic soda, and the better 
 grades are so treated. These are of' a very rich and velvety 
 color. 
 
 Lampblack. Lampblack is made by burning oil with an 
 insufficient supply of air, or rather by thrusting into the flame 
 a large piece of cold porcelain or something of 1 the sort, which 
 so cools down the flame as to prevent perfect combustion, and 
 the carbon is deposited on the cold surface. Similar blacks are 
 made from gas-flames, but the details of these, processes are not 
 generally known, and the variety of products is surprisingly large. 
 Lampblack is always a bulky substance; of some of the finer 
 sorts only 4 or 5 pounds can be packed into a barrel, while of 
 some of the coarser kinds 20 or 30 pounds may occupy the same 
 space. It is sometimes adulterated with bone-black, but this 
 makes it much heavier. The texture of lampblack is incon- 
 ceivably fine; mixed with oil in any considerable quantity it 
 greatly retards its drying, which may be due partly to its obstruct- 
 ing mechanically the penetration of oxygen, and is certainly 
 partly due to the action of oily matters always found in it. It 
 is no doubt due to these that we find a surface which has been 
 painted with lampblack retards the drying of any paint applied 
 over it. Bone-black is also a non-drier, but in a less marked 
 degree. A very small proportion of lampblack is used to affect 
 the color of other paints; liberally mixed with driers it is used 
 alone, especially for signs and the like; it is mixed with red lead 
 to retard the setting of the latter and to get rid of its glaring 
 color. 
 
 Graphite is a mineral, a crystallized form of carbon, not used 
 in common paints, but only as a preservative against rust on iron. 
 Its use for that purpose will be discussed later. 
 
 Grinding. All these pigments may be made into paints by 
 grinding them with linseed- oil. There are two ways of doing 
 this: in one case we mix the pigment to a paste with oil in a mill 
 
OIL PAINTS AND PAINTS IN JAPAN. 133 
 
 especially designed for the purpose, and this "paste color," as it is 
 called, is thinned with rnore oil, with more or less driers and tur- 
 pentine; in the other, we put the oil and dry pigment into a 
 " mixer," usually a vertical cylindrical vessel whose height is Igss 
 than_jts_diameter and which is provided with some sort of stirring 
 apparatus, the simplest being a vertical revolving shaft with 
 blades extending radially; after being thoroughly mixed the oil 
 and pigment are run through a burr-stone mill to make a homo- 
 geneous mixture. Sometimes it is necessary to put it through 
 the mill a second time or even a third, when it is put into suitable 
 packages for shipment. It is not unusual to have some turpentine 
 in the mixture; one effect is to hurry the drying, because there is 
 less oil to 'dry, and because the turpentine itself acts to some 
 extent as a carrier of oxygen; another result is that the film con- 
 tains a larger proportion of solid pigment than it would otherwise 
 have. 
 
 Value of the Pigment. The effect of a pigment, aside 
 from its color and any chemical action it may exert, is threefold. 
 Oil dries to a more or less porous film; and even a film of var- 
 nish is not entirely without porosity. The particles of pigment 
 stop up some of these pores; this makes the coating more imper- 
 vious and consequently better. An oil-film when dry is a tough 
 but rather soft substance, easily scratched off; but the pigment 
 is a hard substance and imparts hardness and capacity for 
 resisting abrasion to the film. It is obvious that if we mix a solid 
 powder with oil, the mixture will be of a much thicker consistency 
 than oil alone, just as mud is thicker than water; hence we can 
 spread a much thicker film of such a mixture over a surface than 
 we can of oil alone, and this results in having a thicker film, which 
 in itself is desirable. So the film of paint is less porous, harder, 
 and thicker than an oil-film. If the oil used be boiled oil, the 
 paint may be nothing but pigment and oil; though, as has been 
 said, turpentine is sometimes a good addition. But if it be raw 
 oil, such a mixture will require a week before it seems to begin 
 to dry, and this prevents the use of raw-oil paints for most pur- 
 poses, unless we add to the mixture an amount of drier sufficient 
 
134 TECHNOLOGY OF PAINT AND VARNISH. 
 
 to make it dry to the touch in a day or thereabouts. It is a very 
 common practice to add to the oil more or less oleo-resinous 
 varnish, the object being to make a glossy paint and one some- 
 what harder. It is much to be regretted that it has become 
 common to use for this purpose a cheap rosin varnish, which is 
 an injury to a good oil paint in every way. Such a paint does 
 not dry properly, and the film will soften and blister if exposed 
 to heat; if very much varnish is used it will make the film crack; 
 it is the cause of most of the cracked paint we see. But if a good 
 varnish made of hard resins is used, the effect will be exactly the 
 opposite. The trouble is that any varnish which ought to be 
 used materially increases the cost of the paint, and the maker, 
 who finds it difficult enough to get a price which will enable him 
 to use pure oil, uses a varnish which costs less than the oil. Such 
 a varnish must be pale in color, or it will affect the color of the 
 paint, and can be made only of common rosin. 
 
 The adulterants of oil are legion. The cheapest are made of 
 mineral oil; these are of little or no value. It should be said 
 that, as compared with pure linseed-oil, nothing which can be 
 added to it increases its value except a good varnish; but some 
 of these things have some power to form a film and in that sense 
 may be said to have value. Probably the best is fish-oil, which 
 easily combines with driers, and if mixed in not too great propor- 
 tion with linseed- oil forms a film which dries after a fashion, 
 though slowly, and has fairly good weather-resisting qualities. A 
 mixture containing twenty per cent, of boiled fish-oil is believed 
 by some good paint -manufacturers to be superior to linseed-oil 
 alone for a roof -paint, but this is doubtful. 
 
 COACH-COLORS. 
 
 For painting carriages and coaches oil paints are too soft 
 and cannot be made to take a sufficiently smooth surface. It is 
 necessary to have a paint which will be hard and which can be 
 rubbed down with pumice-stone until all irregularities of the 
 surface disappear, and an oil paint will never get hard enough 
 for this. The pigment is, therefore, ground in varnish, and as 
 
OIL PAINTS AND PAINTS IN JAPAN. 135 
 
 no ordinary varnish is quick enough in drying, a special medium, 
 called grin ding-japan, has been concocted for this purpose. This 
 is essentially an oleo-resinous varnish charged with lead and 
 manganese to the highest degree, and it will not only dry hard 
 itself in an extremely short time, but so effective is it as a drier that 
 paints ground to a paste in this vehicle and thinned just before 
 use with a suitable mixture of oil and turpentine will dry in a few 
 hours to a perfectly hard surface, ready for the next operation. 
 
 Grinding- japan. The exact composition of these grinding- 
 japans is kept secret by the makers, but the best of them have 
 the best quality of shellac for the resinous ingredient, as has 
 been stated in a previous chapter, and the real secret is in the 
 purchase of the best materials and the use of a sufficient quantity 
 of good shellac. This, of course, makes the cost increase, but it is 
 in the end economical, because coach-colors are sold by the pound 
 instead of the gallon, and for rather high prices, as they must be 
 because of the labor expended on them, and on account of the 
 chemical activity or potency of the vehicle in which they are 
 ground they are more liable than most paints to undergo spon- 
 taneous changes inside the can before being opened ; losses of this 
 sort, which fall on the manufacturer, are much less if the japan 
 is of the best quality. The best is actually and literally the cheap- 
 est. The carriage -painter requires paints of excellent quality and 
 expects to pay good prices for them, consequently pigments are 
 used which are altogether too expensive for oil paints; no pig- 
 ments used by artists are too expensive for the best of this work. 
 
 Water-cooled Mills. These paints cannot be ground in an 
 ordinary mill, because the friction develops heat and heat starts 
 up the chemical activity of the japan, with the result that the 
 color and consistency of the product change; so they are ground 
 in a water-cooled mill. In such a mill the stones are cemented into 
 iron shells, just large enough in diameter to receive the stone, 
 which, however, does not fill the cavity to the bottom; its edge is 
 cemented to the interior of the iron shell, and a flat space remains 
 back of the stone between it and the iron. Through this space 
 a stream of cold water constantly flows, and thus the stone is 
 
136 TECHNOLOGY OF PAINT AND VARNISH. 
 
 always prevented from heating. Both upper and lower stones 
 are thus water-cooled and the proper operation of these mills 
 calls for the superintendence of a specially trained foreman, who. 
 receives high wages, and is commonly ranked next to the superin- 
 tendent of the works. The colors as they come from the mill 
 should be constantly watched and tested against standard sam- 
 ples, not only for fineness, but especially for color. The operator 
 has a slip of plain glass, on which with a palette-knife he smears a 
 bit of paint ; in contact with it he then lays on a bit of the standard ; 
 turning the glass over and looking at the paint through the glass, 
 the slightest difference is immediately noticeable. For the benefit 
 of those not familiar with these operations, it may be said that 
 the ordinary burr-stone mill, such as is used for grinding all sorts 
 of substances for such mills are used on most diverse materials 
 and will economically grind a larger number of substances than 
 all other kinds of pulverizing machines combined consists of 
 two flat circular stones, the upper of which is fixed in a rigid 
 frame, and has an opening in the centre, called the eye of the 
 stone, into which is dropped the material to be ground; the lower 
 stone, which has no eye, is supported somewhat loosely on the 
 upper end of a shaft, in such a way that when the shaft is made 
 to revolve the stone revolves, but it is loose enough so that when 
 pressed against the lower side of the upper stone it may adjust 
 itself to that, although the plane of their junction may not be at 
 right angles to the axis of rotation ; in which case the lower stone 
 will wobble as it revolves. The fineness of grinding is determined 
 in part by the closeness with which the stones are pressed together. 
 In the best form of water-cooled mill this construction is con- 
 siderably modified. The lower stone, in its metal shell, is screwed 
 firmly on the top at the shaft, like a face-plate on a lathe, so that 
 it cannot vary its position; the upper stone, instead of being 
 fixed to a rigid frame, is held in a frame provided with a universal 
 motion, essentially like the gimbals which support a ship's compass, 
 and this whole frame may be drawn down by a tension screw, 
 so as to make the upper stone fit itself to the position of the lower 
 one. A little consideration will show that in the common form 
 
OIL PAINTS AND PAINTS IN JAPAN. 137 
 
 of mill, having a loose lower stone, when the stone is in rapid 
 motion it will tend, by centrifugal force, to take a position at right 
 angles to the axis of rotation, and as this is not permitted by the 
 rigidity of the other stone, it will press against the latter on one 
 side and be free from it on the other; which is a fault, because 
 the two stones should be pressed together in all parts equally. This 
 defect is obviated in the newer form of mill, because the lower 
 stone revolves on a rigid bearing, and though it may not be dressed 
 truly in a horizontal plane, the centrifugal force can produce no 
 effect on its position; the upper stone, which is pressed against it, 
 has no rotary motion and is, by the universal joint in which it 
 swings, pressed uniformly all the time. It was for a long time 
 believed, and by many experienced but not well-informed people 
 is still believed, that colors can be ground to an extreme degree 
 of fineness only on a stone slab with a muller, as described by 
 Cennini, in a passage already quoted, because with such a rudi- 
 mentary apparatus the intelligence and watchful patience- of the 
 operator secures a uniform grinding and the slowness of the 
 operation prevents heating; at least, it is the operator and not the 
 paint that gets warm; but in a water-cooled mill of the improved 
 design, which has been described, these good results are auto- 
 matically secured and the paint is besides protected from the 
 action of the air and the dust during grinding, and by putting it 
 through the mill as many times as may be desired it may be 
 ground to any degree of fineness. Artist's colors of unequalled 
 excellence are now made in this way, and it is obvious that colors 
 can be ground in a volatile medium like turpentine or varnish 
 only with such a machine. These mills have been in use about 
 twenty years, but are still unknown to many. Water-cooled 
 mills of the older pattern are of much earlier date. 
 
 Few of my readers know where to look for the oldest paint-mill 
 in America. It was very different from those now in use ; it con- 
 sisted of a large flat rectangular stone, hollowed out to form a 
 stone trough capable of holding seventy-five or a hundred gallons 
 of paint ; the materials for which, having been put in the trough, 
 were mixed and ground together by a stone ball, about two feet 
 
138 TECHNOLOGY OF PAINT AND VARNISH. 
 
 in diameter, which was rolled from end to end of this receptacle, 
 and served both to mix and grind the contents. 
 
 This mill is in Boston Mfass. As you walk down Hanover 
 Street from Washington Street, keeping on the south side of 
 Hanover, just before reaching Blackstone Street, you may notice 
 a narrow lane called Marshall Street, turning off to the right. 
 Down this alley about fifty feet there is a little open triangular 
 space; when you reach it turn around, and in the foundation 
 of the building in front of you (which faces on Hanover) you will 
 see the "Boston Stone," as represented in the accompanying 
 illustration. This is the old paint-mill which was imported from 
 England about the year 1700 by a painter who had a little shop 
 in the old wooden house that then occupied this site. It is, there- 
 fore, more than two hundred years old. 
 
 Following the custom of the times, he placed on the Hanover 
 Street front of his home the English coat of arms carved in wood, 
 with his initials and the date, 1701, upon it, from which his dwelling 
 came to be known as the "Painter's Arms." When the old frame 
 house was removed in 1835, the "Painter's Arms" were taken 
 down and replaced on the new building. 
 
 At the same time, the Boston Stone, which had also been tem- 
 porarily removed, was put back in the position it now occupies. 
 The round stone above, which is about two feet in diameter, 
 was the grinder or "muller," and was rolled back and forth in 
 the trough hollowed out in one side of the larger stone under- 
 neath and thus ground the paint. The grinder was once lost 
 
OIL PAINTS AND PAINTS IN JAPAN. 139 
 
 for a time, and was discovered in digging the foundation for the 
 present building; the trough-stone was found in the yard of the 
 house when the place was bought from the painter, and as the 
 stone was of no use there, it was removed to the corner of the 
 house to protect the building from injury by carts. For some 
 time after it had been placed in this position it was utilized by 
 surveyors as a starting-point from which to run their lines. The 
 original stone, the capacity of which is said to have been nearly 
 two barrelfuls of paint, was finally split into four pieces, and it 
 is one of these fragments that now rests under the grinder with the 
 inscription "Boston Stone 1737" cut in it. The way in which 
 it came to be called the Boston Stone is thus described by a local 
 antiquarian : 
 
 "When I was a boy," said Dr. Elliott, "in passing the build- 
 ing, I saw a lad named Joe Whiting, whose father occupied the 
 shop, writing on the stone these words : ' Boston Stone, Marshall 
 Lane. 5 After I became a man, I asked Mr. Whiting who set 
 the boy at work on the stone. He said : ' Marshall Lane at that 
 time not being named, it was difficult to designate his place of 
 business. A Scotchman who opened a shop for the sale of ale 
 and cheese, directly opposite, made a complaint of the difficulty. 
 He said in London there was a large stone at a certain corner 
 marked London Stone, which served as a direction to all places 
 near it, and if I would let Joe write the words Boston Stone on 
 this, people would notice it and it would set them guessing what 
 it meant, and would become a good landmark. ' ' 
 
 That the Scotchman was right, in his belief is proved by the 
 fact that for generations past the dull red, weather-stained stone, 
 with the deeply cut, white lettering, has been one of the land- 
 marks of the North End, so well known that we find it in Whit- 
 tier's stirring appeal : 
 
 "Woe to thee, when men shall search 
 Vainly for the Old South Church; 
 When, from Neck to Boston Stone, 
 All thy pride of place is gone; 
 When from Bay and railroad car, 
 Stretched before them wide and far, 
 Men shall only see a great 
 Wilderness of brick and slate!" 
 
CHAPTER XIII. 
 
 VARNISH OR ENAMEL PAINTS. 
 
 ALL oleo-resinous varnishes are more or less dark in color 
 The very pale ones are yellow; the medium ones are brownish 
 yellow; the dark ones are yellowish brown. If, therefore, we 
 apply a coat of varnish over a painted surface, the color of the 
 latter will be changed ; and in order to avoid this, the painter may 
 mix some of his pigment in the varnish, thus bringing the pig- 
 ment to the surface and displaying its color, with less, but not 
 entirely without, influence from the color of the varnish. Of 
 course, if the paint is dark in color, the color of the varnish is of 
 no account, but to make a white enamel paint taxes the resources 
 of the most skilful varnish-maker. There are indeed varnishes 
 which are nearly free from color, such as bleached shellac; but 
 shellac is an acid resin, and if we mix white lead or white zinc with 
 it, a chemical action is at once set up and a doughy mass not in 
 the least resembling paint is formed. There are some spirit 
 varnishes which may be mixed immediately before using with 
 these pigments, but they lack durability. 
 
 Damar Enamel. The one most generally liked on account 
 of its free working quality, its color, and its moderate price is 
 damar, but this has not a very good lustre; it is, and always 
 remains, soft, or at least does not approach an oleo-resinous 
 varnish in hardness, and it soon loses whatever gloss it had 
 in the beginning, and if exposed to the weather it is almost imme- 
 diately destroyed. It is a good deal used in making white enamel 
 for iron beds and the like, and is hardened by baking. This 
 also greatly improves its lustre and its durability, and, as it is 
 not to be exposed to the weather or even to the sun, it is fairly 
 
 140 
 
VARNISH OR ENAMEL PAINTS. 141 
 
 satisfactory for this purpose. White is the color of sunlight, and 
 a surface of clean snow is probably the whitest thing we ever 
 see; no pigment will >ear comparison with it. So when we 
 talk of paints white is a comparative term; some paints look 
 more like white than others, and the best of them when ground 
 in oil look decidedly yellow, from the color of the vehicle, if com- 
 pared with the pigment either dry or made into a water-color. 
 Artists frequently use poppy-oil or walnut-oil, which are drying 
 oils (but less drying than linseed) because of their pale color, 
 but the advantage is only temporary, because they yellow with 
 age quite as much as linseed. Indeed they are much worse 
 because it is necessary, in order to make them dry, to load them 
 with driers far beyond the need with linseed-oil, and this, as has 
 been explained, has a most injurious effect on their permanence. 
 All these oils with age turn yellow, especially in the dark or in 
 weak light, and may from time to time be bleached by exposure 
 to the direct sunlight. A painted surface, as, for example, the 
 outside of a house, continually exposed to the sun remains white. 
 Varnish paints, however, do not change in any such marked 
 manner; they do not grow yellow, nor are they bleached by 
 sunlight very much. White lead or zinc ground in oil is whiter 
 than any oleo-resinous varnish paint, at least after being sun- 
 bleached, but very white enamel paint may be made if the neces- 
 sary expense is warranted. 
 
 These enamel paints are certainly the highest achievement 
 of the paint -maker's art. They are, like the varnishes, unlimited 
 in variety, and may be made of quality suitable for the most 
 diverse uses. If they are to be used on furniture, they will be 
 made with a hard varnish and may be rubbed and polished like 
 a varnished surface; if for interior woodwork of a house, a more 
 elastic varnish will be used, and to stand exposure to the weather 
 the varnish must be made especially for such service. The maker 
 must know first what pigments he will have to supply, then he will 
 consider what varnishes he has found suitable for use with these 
 pigments ; from a list of these he selects such as will make a vehicle 
 at once elastic in a high degree and hard to resist abrasion, with 
 
142 TECHNOLOGY OF PAINT AND VARNISH. 
 
 toughness to act as a binder and, especially if it is to be used on 
 metal or any impermeable material, extremely adhesive. When 
 a suitable mixture is found and ground with pigments which are 
 chemically inert and permanent we have a paint of the highest 
 degree of excellence. As a matter of practice the greater propor- 
 tion of enamel paints are light in color and, therefore, have white 
 lead or white zinc as a base, and the varnish used must be such as 
 will work properly with these pigments, which, as they cannot be 
 called chemically inert, are somewhat difficult to fit with an other- 
 wise suitable vehicle. The kauri varnishes seem to work better 
 than any others, perhaps because they are so completely free from 
 acidity; those made from the softer resins and from some of the 
 harder resins do not behave as well. 
 
 Defects of Enamels. The trouble is that the mixture becomes 
 thick, and if we thin it with more varnish or turpentine we, of 
 course, have less than the normal amount of pigment in it and it 
 lacks covering power ; moreover, the paint becomes ropy with age 
 and no amount of thinning will make it spread freely and uniformly. 
 I have never seen enamel paint containing much white lead (and 
 zinc, which works better in cheap enamels, is quite as bad in those 
 of better quality) which did not deteriorate somewhat on standing 
 a long time. This is a serious obstacle to their general use, and 
 even when fresh they do not and can not flow like an oil paint, nor 
 do they equal the oil paints in covering power. This is because 
 the varnish is much more viscid than oil alone, and if we put as 
 much pigment to a gallon of varnish as we would do to a gallon of 
 oil, the mixture would be too thick to work properly under the 
 brush. The enamel paint is, therefore, comparatively trans- 
 parent and it requires a great many coats to make a substantial 
 foundation of color. Hence it is the common practice to lay on a 
 foundation of oil paint, which has much more covering body, until 
 we get the desired color ; then finish with as many coats of enamels 
 as may be necessary. This is a violation of the general rule, 
 to be hereafter discussed, that the under-coat should always be 
 harder or not less hard than the outer one, and for severe expos- 
 ure out of doors it should not be followed; but for interior work, 
 
VARNISH OR ENAMEL PAINTS. 143- 
 
 where nearly all enamel is used, it is usually satisfactory, and it 
 is not only less expensive but far less tedious than building up a. 
 body of solid enamel paint. 
 
 Enamel may be Thinned with Varnish. When it is necessary, 
 as it sometimes is, to thin the enamel paint at the time of applying 
 it, this should never be done with oil, and it is not advisable to do 
 it with turpentine, but with varnish; and the varnish should be 
 slower-drying than the enamel. It would, of course, be right 
 to use the same varnish the enamel was made of, but this is not 
 often possible, and it is good safe advice to use for the purpose a 
 finishing carriage -varnish, or "wearing body" varnish as it is. 
 often called, which is at once pale in color, elastic, and possessed 
 of the very finest working qualities. Spar- varnish is also suitable. 
 These varnishes should, of course, be from reliable makers, because 
 not a little inferior varnish is put out under these names. It is 
 extremely dangerous (that is, to the quality of the paint) to add 
 oil to any -enamel paint, or to a varnish, for that matter; there is 
 no objection, usually, to adding a good varnish to oil or an oil paint, 
 for if it does no good it probably will do no harm; but adding oil 
 to varnish is only less reprehensible than adding drier or japan to 
 it, all of which things are not infrequently done by persons of a 
 sufficient degree of depravity. Enamels are sometimes made by- 
 grinding the pigment in oil to a paste and then thinning this with 
 varnish, and fairly good enamels may be made in this way; but it is. 
 better to grind the pigment directly with the varnish, because add- 
 ing in even this indirect way oil to the varnish slows down its drying 
 beyond all reason and makes it necessary to use a quick-drying 
 varnish, when we might just as well use all varnish and use one 
 which would be slower and much more durable and have better 
 working qualities. On the other hand, remembering what has 
 been said about the necessity of using mixtures of different var- 
 nishes to get a compound of the right character, we may usually 
 select a varnish to grind the color into a paste, which will be 
 especially suited for grinding, and in which the pigment will keep 
 well, and when the paint is called for, some of this paste may be 
 taken and mixed with the varnish which is to be used, the mixture 
 
144 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Tim through a mill to insure the proper mixing, and it is ready to 
 ship. It is generally a good plan to have your principal varnishes 
 mixed and tanked for a month or more before putting into cans, 
 because it takes a long time for the components which have sensi- 
 bly the same physical qualities to become uniformly mixed, and 
 this is an objection to thinning a varnish, even with pure turpen- 
 tine, and a reason why such a practice seems so seriously to injure 
 its working qualities ; if we add the turpentine and mix it as well 
 as we can and then set it away for a month or two, we shall find a 
 great difference. Any one may illustrate this by making a syrup 
 of sugar and water, and pour some of this thick, ropy syrup into a 
 bottle of pure water; though perfectly miscible, it will take an 
 astonishing amount of shaking before the two liquids become, 
 even to the eye, completely mixed. But this does not hold true 
 in case of these enamel paints, because we run the mixture (which 
 we admit to be an imperfect one) of paste color and varnish 
 through the mill, and this mixes them in the most perfect manner ; 
 the mixture is much more complete than would be the case if no 
 pigment were present. 
 
 It has already been said that some of these paints are made 
 with damar; it has also, in an earlier chapter, been remarked 
 that damar varnish is often adulterated with rosin, even up to the 
 vanishing-point, and these various statements may be combined, 
 when they explain the composition of some of the most atrocious 
 compounds known in the whole paint business. It would be a 
 waste of words, and of the sort of words which do not look well 
 in a book, to describe these products, which are in no small degree 
 responsible for the poor opinion of enamel paints held by many 
 worthy and otherwise intelligent people. It is not to be denied 
 that varnish or enamel paints have their drawbacks; as has been 
 said, they do not work as freely as oil paints, they are, especially 
 in white, a little less brilliant in color, they do not cover as well, 
 and they do not keep well in the can, but they work freely enough 
 so that a good workman can do the finest sort of work with them 
 when they are fresh; their lustre more than makes up for any 
 slight yellowing of the color, which is at any rate noticeable in 
 
VARNISH OR ENAMEL PAINTS 145 
 
 hardly anything but white; they have fair covering quality, and 
 the dark shades, which are made with opaque pigments, cover 
 perfectly; some of them appear to keep in the can indefinitely, 
 and even the whites, which are the worst, will usually keep, espe- 
 cially in a cool place, a year or more, which is longer than any 
 paint ever should be kept, for it is a general rule that paint is best 
 when it comes from the mill. Varnishes are thought to improve 
 by keeping, but such a thing has never been supposed of paint, 
 even oil paint, except that white lead and oil are supposed to 
 improve for a time. 
 
 Special Enamels for Special Uses. Paints of this sort, like 
 varnishes, should be made for the special uses to which they are 
 to be put; it is not practicable to use one kind for all sorts 
 of work, interior and exterior, and even out of doors there are 
 many places where a fine appearance is essential and others 
 where this is of less account than extreme durability. Dark 
 and dull colors are in general more durable than light and bril- 
 liant ones; this is true also of oil paints. If a paint is to be sub- 
 ject to frequent rubbing, as on a hand-rail, or to blasts of dust, 
 as on a railway car, it must have hardness to resist abrasion, 
 or it will not answer at all; and it may be that the necessary 
 hardness cannot be had without making the paint so inelastic 
 that it will in time crack from the rapid and extreme changes 
 of temperature it must endure; but if it is to stand the weather 
 alone, it may be made so tough that it can never possibly crack, 
 and, being practically water-proof, which an oil paint is not, it 
 will resist decomposition longer than any other preservative coat- 
 ing. But such a paint as that would be entirely out of place on 
 the interior finish of a house, and if applied to articles of fur- 
 niture, it would make a horrible mess. Yet with suitable enamels 
 the most dainty articles of the toilet-table are painted, and all 
 the most valuable pictures, made in the middle ages by the great 
 masters of art, have come down to us painted with pigments 
 .ground in just such varnish as we are making to-day. 
 
CHAPTER XIV. 
 
 CHINESE AND JAPANESE LACQUERS. 
 
 THE Jesuit missionary Father D'Incarville, who was a cor- 
 responding member of the French Academy of Sciences, wrote 
 from China a memoir on Chinese varnish; this was, as stated 
 in the text, a few years after the death of the Emperor Yung- 
 ching or Yong-toking, and in the beginning of the reign of Keen- 
 lung; that is, a few years after 1735. This memoir was said by 
 Watin to be practically inaccessible in 1772; inaccurate state- 
 ments said to be based on it appear in various encyclopaedias; 
 and as the writer has been so fortunate as to have secured a copy, 
 the following translation, which is complete with the except ion 
 of a few irrelevant sentences, is now presented, as an important 
 addition to our knowledge of the subject. The author claimed 
 no knowledge of varnish in general, but simply wrote out his 
 own observations. The mention of tung-oil is the earliest which 
 has come to the notice of the translator. 
 
 D'INCARVILLE'S MEMOIR. 
 
 It is commonly known in Europe that Chinese varnish is not 
 a composition, but a gum or resin which runs from a tree which 
 the Chinese call Tsichou, or varnish-tree. 
 
 This tree grows in most of the southern provinces of China; 
 it grows wild in the mountains; the trunk of the tree is some- 
 times a foot or more in diameter. Those which are cultivated 
 on the plains, or on certain mountains, the Chinese tap for their 
 juice when they are as large as one's leg; these cultivated trees 
 
 do not live more than about ten years. 
 
 146 
 
CHINESE AND JAPANESE LACQUERS. 14? 
 
 Varnish-trees. The varnish-tree is easily propagated from 
 slips; in the autumn they select such branches as they wish to 
 use for this purpose; they pack the twig not too firmly with 
 earth, a few inches beyond the place where it is to be cut off, and 
 this earth is formed into a ball about the size of one's head, and 
 wrapped in tow or linen cloth to keep it in shape; they water it 
 occasionally to keep it moist ; the branch puts forth roots, and in 
 the spring it is cut off above the ball of earth and is transplantable. 
 
 This tree grows as well in an open country as in the moun- 
 tains, and the varnish is quite as good, provided that the situation 
 is favorable; if the trees have not a good exposure or are in the 
 shade, they give more varnish, but not as good. This tree requires 
 no other culture than to have the earth stirred beneath it, and 
 to fertilize it with the leaves which fall from the tree. 
 
 Collection of Varnish. The varnish is collected in summer. 
 If it is a cultivated tree, the sap is drawn three times ; that which 
 is taken first is best, and the second is better than the third. If 
 the trees are wild, they tap them but once a year; or if they do 
 it three times, they then leave the tree undisturbed for three years. 
 
 To obtain the varnish they make, with a knife, three cuts 
 which go through the bark but do not raise it. These three cuts 
 form a triangle; in the base of this triangle they insert a clam- 
 shell to receive the liquid which runs out from the other two cuts ; 
 this is the practice with cultivated trees. With wild ones they 
 .make a cut in the tree with a hatchet, as they do in Europe to 
 get turpentine from the pine. It is possible to make twenty 
 incisions in one of these large trees; but on the cultivated ones 
 they set not more than four shells at a time, and they make new 
 cuts each time they wish to get more varnish. 
 
 It sometimes happens to the great wild trees that after having 
 made the incisions the varnish does not run ; it is then necessary to 
 slightly moisten the cut surfaces; for this they provide themselves 
 with hogs' bristles, some of which they moisten, if water is not 
 at hand, with saliva, and put about the place; which treatment, 
 by moistening, opens the pores of the tree and lets the varnish 
 escape. 
 
148 TECHNOLOGY OF PAINT AND VARNISH. 
 
 When it appears that one of the wild trees is exhausted, and 
 there is no hope of getting more from it, they cover the top of 
 the tree with a little straw, which they set on fire, and all the 
 remaining varnish in the tree is precipitated into the numerous 
 incisions which they have made near the foot of the tree. 
 
 Those who collect it go out before daybreak. In the morning 
 twilight they set the shells in place; each man can set about a 
 hundred. These they leave about three hours, after which they 
 collect the varnish, beginning with those first set. If the shells 
 are left longer the varnish is better, but less in quantity, because 
 the sun evaporates the aqueous parts, and this would cause a 
 loss to the seller. 
 
 The collector carries, hung to his girdle, a little bucket of bam- 
 boo in which he deposits the varnish. To do this he moistens 
 his finger by passing it over his tongue, and in wiping out the 
 shell the varnish does not stick to his finger because it is moist. 
 Some use a little wooden spatula which they moisten with water 
 or with the tongue. 
 
 Storage of Varnish. What each one collects in his little 
 bucket he carries to the dealer, who preserves it in casks. These 
 buckets and casks are carefully covered with a sheet of paper, as 
 confectioners cover their jars of preserves with a circular piece 
 of paper cut to fit the top of the jar. Those who collect the varnish 
 do not take the trouble to cut out the paper in this way, but they 
 fit it over the mouth of the vessel, to preserve the varnish better, 
 and to prevent the entrance of the least dust. Their paper, which 
 they call Moteou-tchi, is very suitable for this; it is made of 
 hemp. 
 
 Its Poisonous Qualities. It is necessary to take care, in cover- 
 ing and opening the vessels which contain the varnish, not to 
 expose one's self to the vapor; the face should be turned to one 
 side; unless one is careful there is risk of getting an eruptive 
 disease, such as is caused by the poison-ivy of Canada, except 
 that the poisoning by varnish is much worse; but it is not fatal. 
 To lessen the burning sensation of these blisters they bathe them 
 with cold water, if they have not burst ; but if they have, they 
 
CHINESE AND JAPANESE LACQUERS. 149 
 
 rub them with the yellow matter taken from the bodies of crabs, 
 or, if that is not to be had, with the flesh of shell- fish, which by its 
 coolness gives much relief. Few of those who work in varnish 
 are exempt from being attacked once by this disease. It is some- 
 what singular that people who are active and highly colored are 
 more subject to it than those of a phlegmatic temperament. 
 Some of the latter are never attacked. 
 
 To keep the varnish they set the vessels in caves where it is 
 cool and not too damp ; being well covered, they keep it as long 
 as they wish. 
 
 The varnish, when it comes from the tree, resembles liquid 
 pitch; exposed to the air it takes on a reddish color, and soon 
 becomes black, but not a brilliant black because of the water 
 which it contains. 
 
 Three Kinds. The Chinese distinguish three sorts of varnish : 
 the Nien-tsi, the Si-tsi, and the Kouang-tsi. The three words, 
 Nien, Si, and Kouang, are three names of the principal cities 
 from which they get the three kinds of varnish, namely, Nien- 
 tcheou-fou, Si-tcheou-fou, and Kouang-tcheou-fou. Tcheou-fou 
 signifies principal city, or city of the first class. 
 
 The Nien-tsi and the Si-tsi are two species of varnish which 
 they employ to make the black varnish ; the Nien-tsi is the better, 
 but it is very difficult to get it pure : the dealers mix Si-tsi with it. 
 
 The province from which they get the Nien-tsi is not very 
 extensive, and so there is not enough of it for all the work done 
 in China. The Nien-tsi is of a more brilliant black than the 
 Si-tsi; it costs at Pekin about a hundred sous for a livre (one 
 dollar a pound); the Si-tsi is one-third as costly. The Kouang- 
 tsi is of a yellowish color; it is more pure, or contains less water, 
 than the other kinds. 
 
 Tong-oil. It has another advantage : it is, that in using it 
 they mix it with about half of Tong-yeou, which is another varnish, 
 or rather an oil very common in China, which, at the places 
 where it is produced, costs only two or three cents per pound. I 
 have heard say that they sell it at Paris under the name of Chinese 
 varnish. It resembles turpentine. I have said that they mix 
 
150 TECHNOLOGY OF PAINT AND VARNISH. 
 
 half of this oil in the varnish called Kouang-tsi; that depends on 
 the purity of the varnish: if it is very pure they add more than 
 half; then the price is nearly that of Nien-tsi. 
 
 Drying by Evaporation. It is first necessary to remove from 
 it the aqueous part by evaporating it in the sun; unless this is 
 done it will never become brilliant. The Chinese set about it 
 in the following manner: they have for the purpose large flat 
 vessels the rim of which is not more than an inch or an inch and 
 a half in height; these are a sort of basket of woven reeds or 
 osiers, plastered with a composition of earth or ashes, over which 
 is a single layer of common varnish. They are convenient for 
 holding the varnish while it evaporates, and it can be removed 
 from them easily. 
 
 If the sun is warm, two or three hours are enough to remove 
 the moisture from the varnish, which is not more than an inch 
 deep in the dish. While it is evaporating they beat it with a 
 wooden stirrer almost incessantly, turning and re -turning it ; first 
 it forms white bubbles, which diminish in size little by little; 
 finally they take on a violet color; then the varnish is sufficiently 
 evaporated. 
 
 Further Treatment. When from this varnish, which I sup- 
 pose to be Nien-tsi, to which they have added a fourth part of 
 Si-tsi, they wish to make the fine ordinary varnish of China, after 
 having evaporated it about half they add to it about three-quarters 
 of an ounce of hog's gall to a pound of varnish: it is necessary 
 that this gall should have been previously evaporated in the sun 
 until it becomes somewhat thick; without this hog's gall the 
 varnish would be lacking in body, it would be too fluid. 
 
 After having stirred this gall with the varnish for a quarter of 
 an hour, they add a quarter of an ounce of Roman vitriol (sul- 
 phate of copper) to each pound of varnish; this vitriol they have 
 previously dissolved in a sufficient quantity of water (sometimes 
 they use tea) ; they continue to stir the varnish until, as I have 
 said, the bubbles which form on the surface show a violet color; 
 this varnish, thus prepared, is called, in China, Kouang-tsi, or 
 brilliant varnish; the word Kouang means brilliant. 
 
CHINESE AND JAPANESE LACQUERS. 151 
 
 Black Varnish. Within a few years the Chinese have imitated 
 the brilliant black varnish of Japan. This the Chinese call Yang- 
 tsi; Yang signifies the sea, as though to say a varnish which 
 comes from over seas, Japan being separated by the sea from 
 China. 
 
 The Yang-tsi differs from the Kouang-tsi only in this, that 
 when the Kouang-tsi is entirely evaporated they add to each 
 pound of it an eighth of an ounce of bone-black made from the 
 bones of a deer, reduced to a fine powder. (The Chinese claim 
 that the ribs make better bone-black than the other bones.) We 
 tried ivory-black; the workman found it better than bone-black, 
 and begged me to supply him with it. Besides this bone-black 
 they add an ounce of oil of tea, which they render siccative by 
 making it boil gently, after having thrown into it, in winter, fifty 
 grains of arsenic, half red arsenic or realgar, half gray or white; 
 in summer six grains are enough; they stir this arsenic constantly 
 in the oil with a spatula. To see when the oil has become suffi- 
 ciently siccative they let a drop fall on a piece of cold iron, and if, 
 when they touch the tip of the finger to this thickened oil, it 
 can be drawn out a little into a thread, it is done. This oil gives 
 a fine brilliance to the varnish. 
 
 Tea-oil. The Chinese say that no other oil than tea-oil will 
 dry the varnish, and that any other oil will separate from it- which 
 I doubt; the Tong-yeou rendered siccative does not separate, and 
 I believe that any other very siccative oil would have the same 
 effect. 
 
 This tea-oil is made from the fruit of a particular kind of a 
 tea-tree; it resembles our plum-trees; they cultivate it only for 
 its fruit and not for its leaves. This fruit resembles our chest- 
 nut, except that the outer husk does not bristle with points like 
 our chestnut-burs. The fruit of the Tong-chou, from which 
 they make the Tong-yeou, resembles it also. 
 
 The Chinese have still three other preparations of varnish, 
 as follows: the Tchao-tsi, the Kin-tsi, and the Hoa-kin-tsi. The 
 Tchao-tsi is that which they throw upon their powdered gold to 
 imitate aventurine. Tchao means to envelop, to cover, as one 
 
152 TECHNOLOGY OF PAINT AND VARNISH. 
 
 would say an exterior varnish. This varnish is a transparent 
 yellow; it is composed of half Kouang-tsi, that is to say, that 
 which comes from Kouang-tcheou-fou, and half Tong-yeou 
 rendered siccative. The Kin-tsi has its name from the color of 
 gold; the word Kin means gold. In fact, this varnish is of a 
 golden yellow; it is composed of the most common Si-tsi, or that 
 which has been collected as the third crop, half varnish and 
 half Tong-yeou. It is upon a layer of this varnish that they 
 scatter their gold-powder, over which they spread, as I have 
 said, a coat of Tchao-tsi. The gold-powder thus set between 
 these two coats of varnish imitates aventurine; but it is only 
 after a long time, for it is much more beautiful after a lapse of 
 years than it is within a few months; I have observed it. The 
 Hoa-kin-tsi is that which is used by painters in varnish for tem- 
 pering their colors, whence comes the name Hoa, which means to- 
 paint; that of Kin, because it serves or painting in gold or for 
 designs in gold: the varnish is composed of half Tchao-tsi and 
 half Kin-tsi. 
 
 PREPARATION OF VARNISH. 
 
 Straining. The first thing to be done is to strain the varnish 
 so as to purify it as much as possible from dust and sediment. 
 For this purpose they prepare some cotton as if to make a counter- 
 pane ; they spread three layers of cotton thus prepared on a piece 
 of thin cloth ; on these layers of cotton they turn the varnish, either 
 Yang-tsi or Kouang-tsi evaporated, and they cover it very accu- 
 rately with the cotton, layer by layer, cutting off, if it is necessary, 
 in the folds, a little of the cotton, so that it shall lie more smoothly 
 and evenly. When the three layers of cotton have thus been 
 spread upon the varnish, one after another, they cover the whole 
 with the cloth, to press out the varnish which is thus wrapped up. 
 The machine which the Chinese use for this operation is very 
 simple, and appears to me convenient. When the varnish does not 
 trickle out any more they open the cloth and with their fingers pull 
 to pieces the three layers of cotton, so as to be able to press out as 
 much as possible ; they repeat this manipulation two or three times. 
 
CHINESE AND JAPANESE LACQUERS. 153. 
 
 until they can get no more varnish out; finally they throw away 
 the cotton and recommence the operation with three other layers of 
 new cotton. They strain the varnish a third time; the third and 
 last time they do not use cotton, but a layer of See-mien. The 
 See-mien is made of the outer parchment which covers the chrysalis 
 of the silkworm. They spread upon the thin cloth, in place of 
 cotton, seven or eight layers of See-mien ; they envelop the varnish 
 as they did before when they used cotton, and press it out. The 
 varnish thus filtered is reckoned very pure. For this operation 
 it is necessary to have a place that is perfectly clean, where there 
 is no fear of dust, so that at the end there shall not a grain of dust 
 fall into the varnish thus purified. The Chinese receive it as it 
 runs out from the filter in a perfectly clean porcelain vessel, cover- 
 ing the vessel with a sheet of the paper called Maoteou-tchi, which 
 I have already mentioned, and put it in a suitable place until they 
 wish to use it, when they do not wholly uncover the vessel, but 
 only raise one corner of the paper cover. 
 
 APPLICATION OF THE VARNISH. 
 
 The Workshop. The workshop ought to be an extremely 
 clean place, situated where it will be as much as possible out of the 
 way of dust; to secure this result they cover the wall with mats, 
 and over these mats they paste paper carefully everywhere, so that 
 one cannot discover the least little exposure of the matting; the 
 very door of the workshop, which is made to close tightly, is cov- 
 ered with matting and papered like the rest. 
 
 Dust is Avoided. When the workmen have to apply the 
 varnish, especially the finishing coat, if the weather is such that 
 there is no fear of their taking cold, they wear only a pair of 
 drawers, not even a shirt, for fear of bringing dust into the work- 
 shop; if the season does not permit them to dispense with their 
 clothing, they take great care to shake off the dust before entering, 
 and they wear only such clothes as the dust will not easily adhere 
 to; they are particular to avoid any disturbance in the workshop,, 
 and no unnecessary persons are allowed to enter. 
 
154 TECHNOLOGY OF PAINT AND VARNISH. 
 
 The first thing the workmen do is to clean the brushes which 
 they are going to use. They have a little bowl with a little oil in 
 it, in which they clean them, for fear that there may be some 
 particles of dust in the brushes; they test them carefully before 
 they take them finally from the oil. The brushes being perfectly 
 clean, they uncover a corner of the bowl which contains the var- 
 nish which has been thrice filtered, as has been described. In 
 taking the varnish on the brush they only touch it to the top of the 
 varnish, and in withdrawing the hand they turn the brash two 
 or three times to break off the thread of varnish which strings 
 from the brush. 
 
 In spreading the varnish it is necessary to pass the brush in 
 every direction, applying it equally everywhere; in finishing the 
 brush must be always drawn in one direction. 
 
 Each Coat Dried and Rubbed. Each coa. f varnish has no 
 greater thickness than that of the thinnest paper ; if the varnish 
 is too thick it will make wrinkles in drying ; it is troublesome to get 
 rid of these ; sometimes one is even obliged to cut them off with a 
 chisel, instead of the easier method of grinding them off with 
 cakes made of brick-dust, such as will be described later. Although 
 it may not actually form wrinkles, such a coat of varnish will be 
 very troublesome to dry. Before the application of a second coat 
 of varnish it is necessary that the first coat be well dried, and 
 should ha've been polished with the cakes made of brick-dust. 
 
 Moist Air Dries Varnish. In order to se. away the varnished 
 pieces to dry as soon as they are varnished, they are accustomed 
 to have shelves all around the workshop from top to bottom ; on 
 these they place the varnished articles, setting them lower or 
 higher according as they wish them to dry more or less quickly. 
 The humidity of the earth dries them more or less rapidly accord- 
 ing as they are set nearer or farther from it. When they are 
 absolutely dry they may be put on the top shelves, and left there, if 
 it is thought best. At Pekin, where the air is extremely dry, it is 
 necessary, to dry the varnish, to put it in a humid place, sur- 
 rounded by matting which they sprinkle with fresh water; other- 
 wise the varnish will not dry. If it is an article which is so 
 
CHINESE AND JAPANESE LACQUERS. i$S 
 
 situated that it cannot be removed, they are obliged to hang wet 
 cloths about it. 
 
 When the first coat of varnish is quite dry it is necessary to 
 polish it ; if it is not entirely dry, it will roll up in places when they 
 try to rub it. The day after they have put a piece to dry on the bot- 
 tom shelf they examine it to see if it is dry; to do this they touch it 
 gently with the tip of the finger; when the finger is withdrawn, if 
 the varnish is felt to be tacky it is not dry enough to polish. There 
 is no risk in leaving a piece several days ; the drier the varnish is 
 the better it will polish. It is only necessary to be careful, in damp 
 weather, that the varnish should not be too moist; for then it 
 tarnishes and can never be brought back; if it is a finishing coat, 
 it is lost: it is necessary to rub it and add another coat. To avoid 
 this inconvenience, they do not at such times put pieces to dry on 
 the lowest shelves, but on the second or third ; it is better that the 
 varnish should dry slowly. However they polish the foundation 
 to which they are going to apply the varnish, they always find 
 some little inequalities, which one or two coats of varnish will not 
 be able to efface; this is why they are obliged to rub each coat ; the 
 varnish which is too thin is liable to be too easily removed. What- 
 ever care they take, some grains of dust are always found in the 
 varnish, which come from the little inequalities removed in rub- 
 bing; whence it follows that if each coat were not rubbed, the 
 last coat would be imperfect. 
 
 Polishing-powder. To rub the varnish they form little 
 cakes composed of brick-dust passed through a fine sieve and 
 washed in three waters ; after stirring it in water until it is turbid 
 they pour it off into another vessel and throw out that which has 
 settled to the bottom, as too coarse. They repeat this operation 
 three times, and then leave the water to settle; when it is well 
 settled they carefully pour off the water and cover the vessel 
 which contains the sediment, and set it in the sun to dry. When 
 dried they pass it through a fine sieve, they mix it with Tong-yeou, 
 or they drop in some Tou-tse and a little more than half of swine's 
 blood prepared with lime-water. To form it into cakes they roll 
 this material in cloth, give it the form they wish ; and finally put it 
 
1 56 TECHNOLOGY OF PAINT AND VARNISH. 
 
 to dry in the shade upon a plank covered with paper; if they put 
 it in the sun to dry, they shelter it, for fear that some coarse parti- 
 cles of dust may fall on it which, in polishing the varnish, would 
 make scratches. 
 
 The preparation of the swine's blood with lime-water is made 
 in this manner : They take a handful of straw, beaten and coarsely 
 chopped in pieces three or four inches long ; with this straw they 
 treat the blood hi the way pork-butchers do to separate the clots 
 of blood; after which they pass it through a cloth, and a little 
 later they add to it a third of its volume of lime-water which is 
 white with lime, not having been allowed to settle. This milk 
 of lime must be prepared on the spot and immediately added to 
 the blood, which being thus prepared is preserved in a covered 
 earthen vessel. 
 
 Rubbing. To rub the varnish they wet with water the end of 
 the cake of brick-dust, and they rub it vigorously all over the 
 surface to remove the little inequalities caused by any grains of 
 dust which may have been in the varnish or in the brushes; and 
 from time to time they pass over the surface a brush made of 
 long hair, wet with water, holding the varnished article over the 
 vessel in which they wet the brush, to wash off and remove the 
 mud made from the brick-dust, so as to see if there are still any 
 little defects; and they rub them away before they apply a second 
 coat of varnish. They rub the second coat like the first, when 
 it is thoroughly dry; at last they apply the third coat; it is 
 above all things important with this last coat to take all possible 
 care to avoid the least dust. 
 
 It is only within a few years, under the reigning emperor, 
 that the secret of the Yang-tsi, or the varnish which imitates the 
 brilliance of that of Japan, has been known outside of the palace. 
 About thirty years ago a private citizen of Sout-cheou, one of 
 the cities where they make the very finest varnished pieces in 
 China, found out the secret, or rather learned it from some Japan- 
 ese, the merchants of Sout-cheou having trade with those of 
 Japan. It is to be wished that they had also learned the secret of 
 preparing their Tchao-tsi, which surpasses infinitely that of China* 
 
CHINESE AND JAPANESE LACQUERS. 157 
 
 The Emperor Yong-Toking, father of the emperor now reigning, 
 wished to keep it a secret, and did not wish that it should go out 
 of the palace; in fact, the secret remained unknown to the people 
 outside for many years. At last Kien-long, now reigning, was 
 not so careful about varnish as his father, and did not prevent 
 the secret from being known outside the palace. I know one 
 of the workmen who worked in the palace, who has done in my 
 presence the things I have written in this memoir; it is from 
 this same workman, who has worked for three months in our 
 house, that I know what I have written about varnish. He is a 
 Christian and my convert; I have reason to believe that he does 
 not deceive me. 
 
 Polishing. Formerly the Chinese made only the varnish 
 which they call Toui-kouang; Kouang means brilliance, and Toui 
 to remove, as they say of varnish which has lost its lustre; the 
 reason being that they rubbed the last coat of varnish the same 
 as the others, and in that way got rid of its gloss. To partly 
 restore this, after having carefully rubbed this third coat they 
 gave it second rubbing with a bunch of hair which had been wet 
 in water in which they had suspended some very fine powder; 
 after this they rubbed it with a piece of very soft silk cloth, and 
 with this in the hand they rubbed vigorously, until the varnish 
 became bright. In the places which they could not reach with 
 the hand, they attached to the end of a bit of wood a piece of 
 this soft silk, and with this rubbed it; and finally they rubbed 
 the varnished surface with a bit of silk slightly moistened with 
 some clear oil, no matter what kind; this gave the varnish a little 
 gloss, but not to be compared with that of the varnish called 
 Yang-tsi. 
 
 The Yang-tsi, on account of the oil of tea which is combined 
 with it and which gives it its brilliance, cannot be rubbed; it is 
 therefore still more necessary to avoid dust than when using 
 Toui-kouang. The only remedy is to hide the defects, in painting 
 the varnished articles, by making the design conceal these imper- 
 fections. 
 
 In varnishing with Yang-tsi they employ this beautiful varnish 
 
158 TECHNOLOGY OF PAINT AND VARNISH. 
 
 'Only for the finishing coat. The Kouang-tsi, of which they make 
 the Toui-kouang, is perfectly good for the two under coats, because 
 these have to be rubbed. The last coat of varnish ought espe- 
 cially to remain a long time on the shelves at the top of the work- 
 shop, for at least fifteen days, before any painting is done on it ; there 
 is a chance that the varnish will be sticky; the gold will stick to 
 the places which are not entirely dry. 
 
 Observe that when one would make the beautiful varnished 
 boxes, like those of the Japanese, it will not do to have them liable 
 to open at the joints; it is necessary to cover all the joints with 
 strips of the paper called Che-tan-tchi. The Japanese use it, as 
 well as the Chinese, to make their work more substantial; but 
 in China, where they do not care so much for the excessive light- 
 ness of these boxes, they use a sort of canvas made of silk, called 
 Kieun, in place of Che-tan- tehi ; then their boxes will never come to 
 pieces. 
 
 Preparation of the Surface. To prevent the varnish of the 
 first coat from sinking into the wood they brush the piece over 
 first with gum- water mixed with chalk. The Che-tan-tchi or the 
 Kieun are applied with pure varnish not evaporated. Before 
 putting on the first coat it is necessary, with a piece of stone less 
 harsh than sandstone, to rub well the Che-tan-tchi or the Kieun; 
 to make their surface more uniform, after they have been rubbed, 
 they are obliged to lay on a light coat of the composition of brick- 
 dust which I have already described, immediately before the appli- 
 cation of the varnish, which they mix with a half of Tout-tsi. 
 (Note. Tou signifies earth, tsi signifies grain; as though to say, 
 grains of earth; or rather, earth which is in granular form; they 
 find it in abundance in the mountains.) 
 
 It is necessary that the Tout-tsi should be passed through a 
 sieve; the whole is mixed with varnish not evaporated, when the 
 composition is very clear and well finished. The Japanese some- 
 times employ only the Che-tan-tchi, and content themselves with 
 rubbing the pieces, before applying the first coat of varnish, with 
 wax, to prevent the varnish from penetrating the wood. The 
 Chinese sometimes do the same thing; but articles finished in this 
 
CHINESE AND JAPANESE LACQUERS. 159 
 
 way are not substantial, and are liable to crack at the joints, espe- 
 cially at Pekin, where the air is extremely trying to wood, no 
 matter how old it may be. 
 
 The wood which the Chinese use for making these varnished 
 articles is as light as that used by the Japanese, and if the work of 
 the Chinese is heavier than that made in Japan, it is because the 
 Chinese usually send their best work to Pekin, and wish them to 
 be substantial, fearing that they will not stand the climate of Pekin, 
 where, in spite of all precautions, they will not last unless they are 
 built as solidly as those which are made in Pekin itself. 
 
 The wood which the Chinese employ is called Ngou-tou-mou. 
 Mou is the generic name for wood; Ngou-tou is the name of the 
 trees. Its wood is very pliant and extremely light, excellent for 
 musical instruments ; they claim that it will give out a better sound 
 than any other wood. 
 
 The brushes for applying the varnish are made of hair; those 
 which are used to wash the pieces are made of the beards of she- 
 goats, or they can use that from cows' tails. The paste with 
 which they bind together the hair of the brushes is made of Tong- 
 yeou, litharge, and Tou-tse, which makes a compound that dries 
 very quickly. To this mixture they add a half of the swine's 
 blood treated with lime-water. Another composition may be used 
 for the same purpose, provided that it is elastic and, in working, 
 does not crumble and come out in dust, as sometimes happens to 
 our brushes in Europe. 
 
 If, in using varnish, it sticks to the hands, they rub them with 
 a little oil; it is easily removed. 
 
 It sometimes happens in time of rain or of high winds that 
 the varnish does not dry; if it does not dry in the usual time, it 
 never will dry. Then the only remedy is to rub it with lime and 
 set it on the lower shelves of the workshop; it will dry in a short 
 time. Before putting it away to dry, it is necessary to thoroughly 
 wipe off the lime with a piece of silk. If the lime has not entirely 
 removed the varnish which did not dry, it will raise up a quantity 
 of little points; these must be made to disappear in polishing the 
 article, after which another coat of varnish is to be applied. 
 
160 TECHNOLOGY OF PAINT AND VARNISH, 
 
 If, in the winter, they wish to evaporate the varnish, as there 
 is little heat from the sun, and the operation would require a 
 long time, they proceed thus : They roll up a mat into the form of 
 a muff, of the size of the vessel in which they wish to evaporate 
 the varnish. They set the mat upright, and place at the bottom 
 a chafing-dish with a little fire in it, and a foot or a foot and a 
 half above it they support, by means of a tripod, the dish of 
 varnish ; in an hour or an hour and a half the varnish is evaporated, 
 all the watery part is gone. 
 
 In rendering the Tong-yeou siccative, after having drawn it 
 from the fire, when they judge this oil to be sufficiently siccative, 
 while it is yet warm, coming from over the fire, they decant it 
 many times to disperse the fumes which come from it; without 
 this precaution the Chinese tell us that it will give a bad color to 
 varnish. 
 
 PAINTING ON VARNISH. 
 
 Painting on varnish is suitable only for furniture like tables, 
 chairs, cabinets, and the like; for large articles which one does 
 not look at too closely it produces a good effect; but for small 
 articles which require delicate designs it is not well adapted; it 
 should therefore be confined to furniture and on the inside of 
 boxes, especially large ones. 
 
 Only designs in gold are fit for delicate work. However 
 finely finished may be the gold-work on varnish done in China, 
 it is not comparable with the beautiful work which is made in 
 Japan. Up to the present time the Chinese have not found the 
 secret of the water-white varnish which the Japanese apply over 
 their gold designs. The transparent varnish of China, which 
 they call Tchao-tsi, inclines to a yellow color, but a muddy yellow, 
 so that it cannot be used for fine and delicate designs ; it may be 
 used to imitate aventurine, as I have already remarked; but this 
 aventurine does not compare with that of Japan. I am not 
 without hope that eventually we may invent in France some 
 varnish which can be applied over the Chinese varnish; and 
 
CHINESE AND JAPANESE LACQUERS. 161 
 
 then we will be able to compete with and even surpass the Japan- 
 ese, our European designs being much finer than those of Japan. 
 
 Designs are Transferred. The following are the details of 
 painting on varnish, as it is done in China. In the first place, 
 the master painter makes his design, the outlines of which he 
 sketches on paper with crayon, and then fills in the details with 
 a brush and ink. Upon this design the pupils follow all the 
 strokes of the brush with orpiment, distempered with water; 
 and, to imprint the design upon the varnished article, they apply 
 to it this design thus freshly traced, pressing lightly with the 
 fingers everywhere over the design, in order that all the marks 
 should leave impressions upon the work. Having taken off the 
 paper they use orpiment again, but mixed in gum-water, or in 
 water in which a little glue has been dissolved (where we use 
 gum- water the Chinese use size), going over all the marks with 
 a brush; then the design will not come off. 
 
 I have already said that the varnish employed by painters in 
 varnish is called Koa-kin-tsi; it is this varnish which is used for 
 a mordant in applying gold; also this varnish is used for dis- 
 tempering colors. To render the varnish more fluid they mix 
 with it a little camphor, which they have previously crushed and 
 mixed with some varnish; they make a paste of it which they 
 knead or rub with a spatula a quarter of an hour or so; it is this 
 paste of which they take a little to temper their colors. Their 
 mordant is nothing else, as has been said, than the varnish Koa- 
 kin-tsi, to which they add some orpiment; when the colors are 
 well mixed they strain them through Che-tan- tschi; they take 
 commonly a little at a time, perhaps an eighth of an ounce or 
 so, enveloping it in Che-tan-tschi, and twisting the two ends with 
 the fingers, they receive the color as it comes through on their 
 fingers with which they are twisting it*; they scrape it off on the 
 palette, which is only a piece of bamboo split in two in the middle ; 
 often, before they are done, the paper bursts. They ought, as 
 soon as the color begins to come through, to untwist the paper 
 a little without slackening the hands, but with one of the dis- 
 engaged fingers transfer the color as \ J : exudes to the place where 
 
162 TECHNOLOGY OF PAINT AND VARNISH. 
 
 it is to be received, being careful not to open the paper; in this 
 way the paper may usually be prevented from bursting. 
 
 If they wish the gold to have a high color, they mix vermilion 
 with the mordant; after the application of the mordant they set 
 the piece to dry in the workshop; about twelve hours is enough 
 for the mordant to be dry enough for the application of the gold. 
 
 Gilding. They have carefully prepared powdered gold in a 
 shell, which they apply with brushes of See-mien; with these 
 they rub the gold lightly over the place where there is mordant; 
 brushing off the surface, they find the gold applied to the design. 
 If they fear lest it may stick to places where they have not applied 
 the mordant, on account of the varnish not being sufficiently 
 dry, they crush some ball white, and with a bit of silk cloth they 
 rub it lightly over the suspected places; after having well wiped 
 the surface they boldly apply the gold upon the mordant. 
 
 Sometimes the painters do not put to dry in the workshop the 
 pieces on which they have applied the mordant. They have a 
 paper called Tchou-tchi, which is made of the pellicle which covers 
 the joints of the bamboo; it is made in great quantity in China: 
 the most of the books are printed on this paper; that which is 
 used for the purpose now mentioned is very thin the same 
 which is used for books of gold-leaf. This they apply several 
 times over the mordant, until hardly any trace of it remains; 
 then they apply the shell gold, which adheres in greater quan- 
 tity but with less lustre; for shading it is good, but elsewhere 
 it is better to apply it in the other manner. 
 
 The Chinese use three kinds of gold, the Ta-tchi, the Tien- 
 tchi, and the Hium-tchi. The Ta-tchi is ordinary gold; the 
 Tien-tchi is pale gold ; the Hium-tchi is made with silver-leaf to 
 which they have given a golden color by exposing it to the vapor 
 of sulphur. The Hium-tchi is not much used except for the edges 
 of dishes, and sometimes for unusually pale shades; to gild the 
 edges of vessels they pass the Hium-tchi through a sieve, and 
 with the end of the finger, on which they have placed some of 
 this powder, they apply it on the edges where they have just 
 before applied some mordant without using any Tchou-tchi to 
 
CHINESE AND JAPANESE LACQUERS. 163 
 
 take it up ; this is so that there may be a large amount on those 
 places which are most subject to wear; they do not care if the 
 mordant does dull the gold. 
 
 When they have been over the article with -the bunch of See- 
 mien, charged with shell gold, sometimes a little gold adheres to 
 the surface without being really attached; this they brush off by 
 lightly touching it with the bunch of See-mien. If there are any 
 places which they cannot reach with the bunch of See-mien, they 
 apply the gold with the pointed end of the brush-handle. 
 
 To imitate mountains, and make sharp separations, they cut 
 out a bit of Tchou-tchi according to the form which they wish to 
 give the mountain; with the paper they cover the place of the 
 mountain and pass the pale gold over the whole; it does not 
 adhere to the places covered by the paper. 
 
 To imitate the trunks and branches of trees or the stalks of 
 plants, after having laid on the first coat of gilding, they trace 
 anew the places which they wish to be marked; and when the 
 mordant has dried in the workshop twelve hours they go over 
 it with shell gold. Ordinarily they use the red mordant, that is, 
 that in which they have mixed vermilion instead of orpiment; 
 the gold is thus made brighter in color. 
 
 White in varnish is obtained by mixing with varnish leaves 
 of silver; only enough varnish is used to make a paste. As 
 much varnish as will make the bulk of a pea is enough for twenty 
 leaves of silver; they mix the leaves one after another; when all 
 are mixed they add a little camphor, which makes the paste almost 
 as clear as water. In place of silver-leaf, to be economical, the 
 Chinese sometimes use some quicksilver, prepared in a particular 
 manner. This is'a secret in a single family. All other material 
 than silver-leaf or the mercury thus prepared will blacken 
 when mixed with varnish; silver makes the most beautiful 
 white. 
 
 Varnish Colors. For red they use Tchou-tche, which appears 
 to be the mineral cinnabar. They can also use a lake made 
 of carthamus-flowers. 
 
 For green they use orpiment, which they mix with indigo. 
 
1 64 TECHNOLOGY OF PAINT AND VARNISH. 
 
 which they call here Kouang-tien-hoa ; it is true indigo and comes 
 from the southern provinces. 
 
 For violet they use Tse-che, or violet-stone (Che means stone ; 
 Tse, violet) ; they use it to make opaque glass. They reduce this 
 stone to an impalpable powder. They also use colcothar, or 
 green vitriol calcined until it is red; to free it from saline matter 
 they boil it in a large quantity of water. Varnish, they say, will 
 not endure any salt. 
 
 Yellow is made with orpiment. 
 
 Colors mixed with varnish are not brilliant at once, but change 
 after a time ; the older they are the more beautiful they become. 
 
 When painters wish to lay on an unusually heavy coat of 
 color they use See-mien instead of'Tchou-tchi. 
 
 To clean varnished articles they use a piece of silk, like an 
 old silk handkerchief; with this they dust off the surface by 
 whisking it, not by rubbing; if, after this, there are still some 
 dirty spots, they easily clean them by wrapping the finger in the 
 handkerchief and rubbing them; if that is not enough, they may 
 wet the end of the finger, still wrapped in the handkerchief, by 
 touching it to the tongue; but it is best if possible to dust off 
 the dirt with the wind made by using the handkerchief as a 
 whisk, and if that will not do, pass the finger, wrapped in the 
 handkerchief, through the hair, from which it will absorb a little 
 oil, which is excellent for cleaning the varnished surface. 
 
 If the varnished article has been softened by being set too 
 near the fire, it may be restored by leaving it out in the dew. 
 
 By exposing colors in varnish to the air, their brilliance is 
 increased. 
 
 Shell gold is thus prepared: They roll a sheet of paper into a 
 cone; in this they put the gold-leaf which is to be made into 
 shell gold. When they have enough, they take a very smooth 
 plate or porcelain platter; on this they pour a few drops of water 
 in which they have dissolved a little glue ; then they turn the gold- 
 leaf on the plate, and with the ends of the fingers they rub the 
 gold as if with a muller; the more they rub it the more beautiful 
 it becomes. They wash it twice with slightly warm water, and 
 
CHINESE AND JAPANESE LACQUERS. 165 
 
 put it away for use. This is the only way the Chinese have for 
 preparing it. 
 
 From Father D'Incarville's memoir there is an interval of a 
 century and a quarter to the next detailed account of oriental 
 lacquer, this time by a British acting consul, Mr. John J. Quin, 
 who in January, 1882, wrote from Tokio a paper of the highest 
 interest on the subject; it is evident from what he says that the 
 varnish must have been the same as that used in China; but the 
 methods of using varnish were far more elaborate than those 
 described by the Jesuit missionary. It is not improbable that 
 D'Incarville gave only the simplest procedure, and that more 
 intricate methods were in use*; in fact, we know that such must 
 have been the case. As described by Mr. Quin the processes 
 are much more prolonged; but he only gives what was in his 
 view the simplest practice. The following is condensed from 
 his paper, using wherever possible his own words; but the neces- 
 sary omissions have made it seem necessary to change the language 
 in many places, that the meaning may be clear. Those interested 
 may consult the original paper in the British consular reports. 
 
 Lacquer-trees of Japan. The Rhus vernicifera, the lac- 
 quer-tree of Japan, is met with all over the main island, and 
 also in smaller quantities in Kinshiu and Shikoku, but it is from 
 Tokio northward that it principally flourishes, growing freely on 
 the mountains as well as in the plains, thus indicating that a 
 moderate climate suits the tree better than a very warm one. 
 Since early days the cultivation of the trees has been encouraged 
 by the government, and as the lacquer industry increased planta- 
 tions were made in every province and district. 
 
 The lacquer-tree can be raised by seed sown in January or 
 February; in ten years the seedling trees will average ten feet 
 high, the diameter of its trunk two and one-half to three inches, 
 and its yield of lacquer sufficient to fill a three-ounce bottle. The 
 trees are set about six feet apart in the plantations. 
 
 A more common method is to cut off a piece six inches long 
 and the thickness of a ringer from the root of a vigorous young 
 
i66 TECHNOLOGY OF PAINT AND VARNISH. 
 
 tree, and planted with one inch of the root above ground. In 
 ten years tfyese will make trees larger than the seedlings by about 
 two- thirds and will yield nearly half as much more sap. 
 
 Lacquer plantations are only on hillsides and waste lands. 
 
 Collecting Lacquer. The trees are tapped once in four days 
 for twenty-five times in one season from June ist to October ist. 
 The cuts are each about an inch and a half long and are from near 
 the ground to as high as a man can reach about six inches apart 
 vertically, but diagonally, not one above another. Branches 
 one inch or more in diameter are also tapped. The tree is thus 
 destroyed in one year. When cut down the branches are cut up 
 and tied in bundles and steeped in water for ten days, after which 
 the lacquer which exudes from them is scraped off; this is called 
 Seshime, or branch lacquer; but this name is also applied to 
 purified and filtered raw lacquer obtained from the trunks of the 
 trees, as has been fully* explained by Rein, and in the following 
 directions, where the term "branch lacquer" is used, this purified 
 raw lacquer is undoubtedly meant. The confusion arises from 
 the same name, se-shime, being applied specifically to branch 
 lacquer and generally to purified raw lacquer. Only a small 
 amount of true branch lacquer is obtained, and it is of poor quality; 
 while from Mr. Quin's specifications it is plain that most of the 
 varnish used was what he calls "branch lacquer," really the 
 ordinary se-shime. 
 
 Shoots sprout up from the roots of the trees which have been 
 cut down, and grow rapidly. 
 
 The best lacquer for transparent varnish comes from large trees > 
 one to two hundred years old. These are, however, rapidly dis- 
 appearing. These large trees were formerly valuable because 
 wax was made from their berries, and this was used for lighting; 
 the introduction of kerosene has destroyed this industry. 
 
 True branch lacquer becomes extremely hard when once 
 dry, but used alone will not dry under some twenty days, so that 
 now, when time is an object, the pure sap is very little used. 
 The price of pure branch lacquer is, owing to the difficulty of 
 drying, only 70 per cent, of ordinary good lacquer. 
 
CHINESE AND JAPANESE LACQUERS. 
 
 Evaporating in the Sun. In preparing all lacquer from the 
 crude lacquer to the various mixtures the principal object is 
 to get rid of the water that exudes from the tree with the sap. 
 To effect this, it is exposed in broad flat wooden dishes, and 
 stirred in the sun. This, however, alone will not cause the original 
 water to evaporate, so from time to time, ordinarily about three 
 times in the day, a small portion of clear water is stirred in, say 
 one per cent, each time, for a couple or three days, according to 
 the heat of the sun; all the water then evaporates together. No 
 lacquer will dry until this process has been gone through. If 
 the lacquer is old, i.e., has been tapped a long time before using, 
 it is much more difficult to dry. In such cases a portion of fresh 
 lacquer is added to the old by the wholesale dealers; or else the 
 manufacturers, instead of water, sometimes mix sake (rice beer) 
 or alcohol to quicken it. 
 
 A very remarkable property of lacquer should be mentioned. 
 If crude lacquer, which is originally of the color and consistency 
 of cream, is exposed to the sun a few days without adding water, it 
 loses its creamy color, and becomes quite black, or nearly so, but 
 also becomes thinner and transparent, or rather translucent, as 
 can be seen when it is smeared on a white board. It will not now,' 
 however, dry if applied to an article, even if kept a month or more 
 in the damp press. But if water is mixed with the lacquer which 
 has thus been exposed and become black, it at once loses its black 
 color and its transparency, and becomes again of a creamy color, 
 though slightly darker, as if some coffee had been added, than at 
 first. After evaporating this water it can then be used like any 
 ordinary lacquer, either alone or in mixtures, and will dry in the 
 damp press, during which process it again turns black. 
 
 Black Lacquer. Black lacquer is made by adding to crude 
 lacquer about five per cent, of the tooth-dye used by women to 
 blacken their teeth, which is made by boiling iron- filings in rice 
 vinegar, and exposing it to the sun for several days, stirring the 
 mixture frequently until it becomes a deep black. 
 
 What lacquer-workers have found their greatest stumbling- 
 block is the difficulty of obtaining a clear transparent varnish. 
 
168 TECHNOLOGY OF PAINT AND VARNISH. 
 
 What is called a transparent varnish is really black to the eye 
 and requires grinding and polishing after application before it 
 presents a brilliant surface, becoming also much lighter after a 
 little time. 
 
 Perilla-oil. Only the cheapest and commonest kinds of lac- 
 quering are done with lacquer mixed with oil; the oil used is 
 that obtained from the plant called Ye (Perilla ocymoides). 
 These do not admit of polishing. Lacquer is prepared in this 
 way, sometimes as much as fifty per cent, of oil being added, 
 after which water is added and the whole evaporated again in the 
 sun ; and this is used to mix with colors to make enamel paints. It 
 is said that vegetable colors cannot be used with lacquer, being 
 in some way destroyed by it. The workmen have never been 
 able to produce white, purple, or any of the more delicate shades. 
 Vermilion, oxide of iron, and orpiment are the principal 
 colors. 
 
 For preparing the surface to be lacquered various priming 
 coats are used; cavities are filled with a sort of cement made 
 by mixing chopped hemp fibre with lacquer; joints are covered 
 with hemp or silk cloth, which is pasted on with a mixture of 
 wheat-flour paste and branch lacquer, or instead of wheat-flour 
 paste, rice-flour paste is used, but is not as good. A mixture of 
 whiting and liquid glue is used for a surface coat on cheap articles. 
 Surfacing compounds, like our rough-stuff, are made by mixing 
 lacquer with finely powdered brick-dust, or powder made of some 
 fine clay which has been burned. They have rubbing- stones of 
 four degrees of fineness; also they use scouring- rushes. (Equise- 
 tum) in place of sandpaper; they use several grades of charcoal 
 for polishing, or rather for rubbing before polishing; for a polish- 
 ing-powder they calcine deer's horns and reduce them to a very 
 fine powder. 
 
 The process of plain lacquering may be thus described : 
 
 1. The article to be lacquered is first carefully smoothed. 
 
 2. The wood is slightly hollowed away along each joint, so as to 
 form a circular depression. 
 
 3. The surface of the whole article is then given a coating of 
 
CHINESE AND JAPANESE LACQUERS. 169 
 
 branch lacquer, and the article set to dry in the .damp press for 
 about twelve hours. This press is air-tight, made of wood, with 
 rough unplaned planks inside; these are thoroughly wetted with 
 water before the articles are put in to dry. Lacquer absolutely 
 requires a damp closed atmosphere for its hardening; otherwise 
 it will run and will always remain sticky. The time of drying is 
 from six to fifty hours, according to the kind of lacquer and the time 
 of year. 
 
 4. The hollowed portions are filled with a mixture of finely 
 chopped hemp, rice paste, and branch lacquer; this is well rubbed 
 in with a wooden spatula, and the piece is set in the damp press 
 to dry for at least forty hours. 
 
 5. Over this is spread a coating made of two parts of finely 
 powdered burnt clay and one and a half parts of branch lacquer, 
 in with just enough water to mix the clay to a paste ; it is then set 
 to dry for twelve hours. 
 
 6. The next process is to smooth off with a rubbing-stone 
 any roughness of the preceding coats. 
 
 7. The article is then given a coating of a mixture of wheat- 
 flour paste with branch lacquer, over which is stretched a hempen 
 cloth, great care being taken to spread it smoothly and leave no 
 wrinkles or perceptible joinings; and it is then again inclosed in 
 the drying-press for twenty-four hours. 
 
 8. After taking the article out of the press all inequalities in 
 the cloth which has now under the influence of the lacquer 
 become harder than wood are smoothed down with a knife or 
 with a plane. 
 
 9. Next, a coating like No. 5 is applied with a wooden spatula, 
 to hide the texture of the hempen cloth, and the article is again 
 put in the press for twenty-four hours. 
 
 10. Next, a coating is given of one part of powdered burnt 
 clay and two parts of branch lacquer, applied with the spatula, 
 after which the article is inclosed in the drying-press for twenty- 
 four hours. 
 
 11. Next, a coating is given of one part of powdered burnt 
 clay and two parts of branch lacquer, applied with the spatula, 
 
1 70 TECHNOLOGY OF PAINT AND VARNISH. 
 
 after which the article is inclosed in the drying- press for twenty- 
 four hours. 
 
 12. Next, a coating is given of one part of powdered burnt 
 clay and two parts of branch lacquer, applied with the spatula, 
 after which the article is inclosed in the drying-press for twenty- 
 four hours. 
 
 13. Next, the article is given a coating of equal parts of pow- 
 dered brick and burnt clay, with which is mixed one and one-half 
 parts of branch lacquer, and the drying process is repeated for 
 twenty-four hours. 
 
 14. Next, the article is given a coating of equal parts of powdered 
 brick and burnt clay, with which is mixed one and one-half parts of 
 branch lacquer, after which it is set to dry for at least three days. 
 
 15. The surface is next ground smooth with a fine hard rubbing- 
 stone. 
 
 1 6. A hardening coat of branch lacquer is given with a spatula, 
 and set to dry for twenty-four hours. 
 
 17. A coat like No. 5 is applied with a spatula, and set to dry 
 for twenty-four hours. 
 
 1 8. When thoroughly hardened the surface is ground with a 
 fine hard rubbing- stone. 
 
 19. Next, a thin coating of branch lacquer is applied with a 
 spatula, and the article is set to dry for twelve hours. 
 
 20. A coating of ordinary lacquer is then applied with a flat 
 brush, and the article is set to dry for twenty-four hours. 
 
 21. The surface is then ground smooth with a kind of char- 
 coal having a rather rough grain; it is made from the Magnolia 
 hypoleuca. 
 
 22. A thin coating of branch lacquer is given with cotton wool 
 old wool being preferred because less likely to leave hairs behind 
 it and rubbed off again with soft paper, after which the article 
 is set to dry for twelve hours. 
 
 23. A coating of black lacquer is then applied, and it is set 
 to dry for twenty-four hours. 
 
 24. The surface is rubbed smooth with very fine and soft 
 charcoal. 
 
CHINESE AND JAPANESE LACQUERS. 171 
 
 25. A coating of black lacquer is then applied, and it is set 
 to dry for twenty-four hours. 
 
 26. The surface is rubbed smooth with very fine and soft 
 charcoal. 
 
 27. The surface is partly polished with finely powdered soft 
 charcoal, applied with a cotton cloth. 
 
 28. A coating of black lacquer is then applied, and it is set to 
 dry for twenty-four hours. 
 
 29. The surface is now polished with an equal mixture of 
 finely powdered burnt clay and calcined and powdered deer's 
 horns, applied with a cotton cloth and a little oil. 
 
 30. A coating of branch lacquer is next given, applied with 
 cotton wool very thinly, and the article is inclosed in the drying- 
 press for twelve hours. 
 
 31. The workman dips his finger in oil, and rubs a small 
 quantity of it over the surface, which he then polishes with deer's- 
 horn ashes, applied with a cotton cloth till a bright surface is 
 obtained. 
 
 32. A coating of branch lacquer is applied as in No. 
 30, wiped off with soft paper, and set to dry for twelve 
 hours. 
 
 33. The oil is applied as in No. 31, and then a final polish- 
 ing with deer's-horn ashes, given with the finger to the surface, 
 which now assumes the most brilliant polish of which it is sus- 
 ceptible. 
 
 For articles which are liable to get rubbed, such as scabbards, 
 these last two processes are repeated seven or eight times, the 
 surface getting harder at each repetition. 
 
 In describing the above processes the minimum time for 
 drying has in each case been given, but for the first twenty-five 
 processes the longer the article is kept in the press the better. 
 From the twenty-eighth process to the finish it is better not to 
 greatly exceed the times mentioned. 
 
 In making articles ornamented in gold lacquer the first twenty- 
 two processes are executed, and at this stage the object is ready to 
 receive the decoration. 
 
172 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Transfer of Designs. The picture to be transferred to the 
 article is drawn on thin paper, to which a coating of size made 
 of glue and alum has been applied. The reverse is rubbed smooth 
 with a polished shell or pebble, and the outlines very lightly 
 traced in lacquer, previously roasted over live charcoal to pre- 
 vent its drying, with a fine brush made of rat's hair. The paper 
 is then laid, with the lacquer side downward, on the article to be 
 decorated, and is gently rubbed with a whalebone spatula wher- 
 ever there is any tracing, and on removing the paper the impress 
 may very faintly be perceived. To bring it out plainly it is rubbed 
 over very lightly with a piece of cotton wool, charged with pow- 
 dered tin or the powder of a hard white stone, which adheres to 
 the lacquer. Japanese paper being peculiarly tough, upwards 
 of twenty impressions can be taken off from one tracing; this 
 tracing does not dry, owing to the lacquer used for the purpose 
 having been partially roasted, and can be wiped off at any time. 
 
 The next process is to trace out the veining of the leaves, or 
 such lines to which in the finished picture it is desired to give the 
 most prominence, and these lines are then powdered over with 
 gold-dust through a quill. The article is then set to dry for 
 twenty-four hours in the damp press. The outline is now drawn 
 carefully with a rat's-hair brush over the original tracing line 
 with a mixture of black lacquer and branch lacquer. The whole 
 is then filled in with this mixed lacquer applied with a hare's- 
 hair grounding-brush. Gold-dust is scattered over the lac- 
 quered portion, and the article is set to dry for twenty-four hours. 
 Another thin coating of this mixed lacquer is again given to the 
 gold-covered portions, and the article set to dry for twelve hours. 
 
 Next, a coating of black lacquer is applied over the whole 
 surface of the article, which is set to dry for at least three days. 
 It is then roughly ground down with coarse charcoal, the surface 
 dust being constantly wiped off with a damp cloth till the pattern 
 begins to appear faintly. Another coating of black lacquer is 
 then given and the article set to dry for thirty-six hours. It is 
 again ground down with coarse charcoal as before, this time 
 until the pattern comes out well. The ensuing processes are the 
 
CHINESE AND JAPANESE LACQUERS. 173 
 
 same as have been described from No. 28 to No. 33 inclusive, 
 for plain lacquer. 
 
 Another Method of Finishing. Another method consists in 
 first thoroughly finishing the piece in the manner first described ; 
 then a tracing is applied to the surface in the manner described 
 for gold lacquering; the outline is carefully painted over with a 
 fine brush of rat's hair and then filled in with a hare's-hair brush, 
 using branch lacquer mixed with an equal weight of bright red 
 oxide of iron. Over this surface gold-dust is scattered with a 
 brush of horse's hair until the lacquer will not absorb any more. 
 The article is then set to dry for twenty-four hours. A thin coat- 
 ing is next applied over the gold of the finest and most transparent 
 lacquer, and set to dry for twenty-four hours at least. It is then 
 most carefully smoothed with soft fine charcoal, and finally pol- 
 ished off with finely powdered burnt clay and a little oil on the 
 point of the finger, until the ornamental portion attains a fine 
 polish. The veining of leaves and the painting of stamens, etc., 
 of flowers, or such other fine work, is now done with a fine rat's- 
 hair brush charged with branch lacquer mixed with red oxide of 
 iron; for this special use the lacquer has been allowed to stand, 
 after mixing, about six months, which causes it to be thicker and 
 less disposed to run, so that it will make fine lines, and it will 
 besides stand up more. Over this fine gold-dust is scattered with 
 a horse's-hair brush, as before, and the article set to dry for twelve 
 hours. Some fine transparent lacquer is then applied to a piece 
 of cotton wool, and rubbed over the whole surface of the box 
 or other article, and wiped off again with soft paper. It is set to 
 dry for twelve hours, after which it is polished off with deer's- 
 horn ashes and a trifle of oil. If a very fine surface is desired, 
 this last lacquering and polishing is repeated. 
 
 Lacquer on Metal. For lacquering on iron or copper, brass 
 or silver, the metal is polished, then given a coat of black lacquer, 
 and put over a charcoal fire and the lacquer burnt on to the metal 
 until all smoke ceases to escape. The fire must not be too fierce, 
 and the metal must not be allowed to get red-hot, or the lacquer 
 turns to ashes. After it is baked quite hard the surface is rubbed 
 
174 TECHNOLOGY OF PAINT AND VARNISH. 
 
 smooth with soft charcoal ; these operations are repeated three or 
 four times, until a good foundation of lacquer has been obtained. 
 The subsequent treatment is exactly such as has been already 
 described, only that the lacquer may be either dried in a damp 
 press in the ordinary way or it may be hardened by baking over 
 the fire. 
 
 When work is required in a hurry the workmen sometimes 
 put a pan of hot water, healed by a charcoal fire, into the press; 
 the steam thus generated dries in an hour or two the lacquer 
 which would ordinarily take twenty-four hours. But lacquer 
 thus treated loses its strength and is never very hard. 
 
 Treatise by Dr. Rein. Some time after the publication of Mr. 
 Quin's report, Dr. J. J. Rein, professor of geography in the 
 University of Bonn, spent some time in Japan, at the expense of 
 ,the German government, studying the industries of that country. 
 The results of his investigations were published in a sumptuous 
 volume in 1889; and this book, called "Industries of Japan," 
 contains the most elaborate and detailed account of the art of 
 lacquering that has yet appeared. The book has been trans- 
 lated into English and may be found in almost any large library; 
 hence it has not been thought best to attempt to give any com- 
 plete review of its contents. In general it may be said that it 
 agrees with Mr. Quin's report; and the following extracts are 
 given to supplement and complete the account already tran- 
 scribed. These extracts are not to be understood as a continuous 
 statement from their author, but are chosen to explain what 
 seems to the present writer the most important points. 
 
 Raw Lacquer. The raw lac is called Ki-urushi; it must be 
 purified before it can be used at all. It is first pressed through 
 cotton cloth, and is then called Ki-sho-mi, or purified raw lac. 
 It then contains from ten to thirty-four per cent, of water, which 
 can be expelled by stirring in the sun or over a slow fire, but 
 especially by a water-bath. It also contains 1.7 to 3.5 per cent. 
 of nitrogenous matter, apparently a proteid ; and 3 to 6.5 per cent, 
 of gum, similar to gum arabic. It contains from 60 to 80 per cent, 
 of lac-acid or Urushi acid, which is the characteristic ingredient. 
 
CHINESE AND JAPANESE LACQUERS. 175 
 
 Traces of oil are sometimes found ; the tapster oils his knife 
 and his spatula or metal spoon to prevent the lac from sticking; 
 to them. The lac-acid is soluble in alcohol, ether, chloroform, 
 etc. 
 
 The Ki-sho-mi, or purified raw lac, if deprived of water, is a 
 gray or brown, syrupy sticky liquid; it will absorb water and is 
 thereby made into a jelly, which when painted on wood dries 
 very quickly. Lac may be thinned by heat, but is usually thinned 
 by the addition of camphor. This is pulverized and added, 
 undissolved, to the lac, in which it dissolves. 
 
 Lac dries best in a damp atmosphere at a temperature from 
 10 C. to 25 C. or at most 30 C. 
 
 Lacquer Dries by an Enzymotic Ferment. The lac-acid ex- 
 tracted by alcohol does not dry; it requires the presence of 
 the proteid and water; and if heated over 60 C. (to a tem- 
 perature which coagulates albumen) it loses its power to dry. 
 According to Korschelt (Chemistry of Japanese Lacquer, Trans.. 
 Asiatic Society of Japan, Vol. XII) the proteid acts as a ferment 
 upon the lac-acid and causes the latter to oxidize, which causes 
 it to become hard. This oxidized lac-acid is insoluble in all 
 the solvents of lac-acid, and is not acted on by either acids or 
 alkalies. 
 
 Ki-sho-mi is ground for some time in a shallow wooden tub, 
 to crush its grain and give it a more uniform fluidity. It is then 
 pressed through cotton cloth or hemp linen; it is then called 
 Se-shime, which is a purified, filtered, and evenly flowing raw 
 lac. It is ready for sale in this condition, but not for use; it 
 must be deprived of its water by evaporation. This is done by 
 evaporation in the sun, or by moderate heat over a coal fire. The 
 Se-shime is poured into shallow pans,, twenty to forty inches in 
 diameter and an inch or an inch and a half deep, and stirred 
 constantly with a flat paddle. If the wooden pan is heated by 
 holding it above a fire, the operation takes several hours; if 
 without fire, it may take sixteen or eighteen hours. After this it 
 is again filtered through cloth. About twenty varieties of lacquer 
 are made from Se-shime ; some of these are from new lacquer o 
 
176 TECHNOLOGY OF PAINT AND VARNISH. 
 
 choice quality, depending on the size and vigor of the tree and 
 the season, but most of the differences are made by admixtures 
 of other substances, such as gamboge, vermilion, and especially 
 .an oil, very much like linseed-oil, made from the seeds of a culti- 
 vated annual plant, the Perilla ocymoides, a labiate plant which 
 is sown in April, blossoms about the end of September and is 
 ripe two weeks later, by the middle of October. It is extensively 
 .grown in China and Japan. 
 
 The general rules to be observed by the lacquerer are as 
 follows : 
 
 1. Every coat must be laid on evenly and then gone over 
 crosswise with the brush or spatula, first in one. direction and 
 then afterward in the other. 
 
 2. No new coat must be put on before the last one is dry. 
 
 3. It can best be determined when a smooth surface is dry 
 by the condensation of the moisture breathed upon it. 
 
 4. Only the groundwork can be dried in the open air or direct 
 sunlight, and then only when the coating contains very little or 
 no lac admixture. 
 
 5. The drying of all genuine lacquer coats must take place in 
 the damp, unwarmed amosphere of a chest, cupboard, or chamber. 
 In order to secure this the chest is laid on its side and washed 
 with a wet cloth. Then the lacquered articles are put in, and 
 the cover, which has been washed also, is closed. The drying 
 cupboard with shelves is treated in the same way. 
 
 6. Such an arrangement serves to keep off draughts of air, 
 dust, and light during drying. 
 
 7. Every fine, finishing lacquer- varnish before it is laid on 
 must be pressed once or twice through a fine porous but strong 
 paper, by turning at both ends in opposite directions. Moder- 
 ately warmed, it flows more freely and hastens the process. 
 
 8. After almost every new coating, according to its nature, 
 comes rubbing off with a rubbing- or polishing-stone, or with 
 magnolia charcoal, or with burned deer's horn (in the first two 
 cases of course with the addition of water), according as the 
 operation follows groundwork or a later coating. 
 
CHINESE AND JAPANESE LACQUERS. 177 
 
 9. The carefully lacquered article when finished must not in 
 any way reveal the make or material of its framework, must be 
 free from accidental unevennesses, cracks, and spots, must have 
 a mirror-like surface and not change in drying nor by heating 
 with warm water. Finally, when breathed upon the moisture 
 must disappear quickly and evenly from the outside toward the 
 centre, as on polished steel. 
 
 Brilliance Developed by Age. Professor Rein further de- 
 scribes some of the various methods employed in decorating 
 lacquered articles with gold and colors; these methods are more 
 elaborate and prolonged than any ever practised in America or 
 Europe. This is partly due, no doubt, to the fact that some of these 
 lacquers, especially the finer and more transparent ones, although 
 they appear to dry in a few days, or weeks at most, do not acquire 
 their full perfection and beauty for a long time ; from Father 
 D'Incarville to the latest writer, all agree that one or more years 
 are required for the complete development of the brilliance of 
 the film after it has been applied. The present writer has two 
 friends who were for some years professors in the University of 
 Tokio, and who were told and believe that fine specimens of lac- 
 quered ware take from twelve to twenty years in finishing. These 
 gentlemen also say that when at intervals it was necessary to have 
 their desks varnished, their hands were poisoned by contact with 
 this freshly varnished surface. Broken fragments of lacquered 
 ware show a great number of layers; and there can be no 
 doubt that the most valuable and essential secret of the lacquer- 
 workers is their unlimited patience, which, with the cheapest 
 labor in the world and the readiness on the part of wealthy 
 collectors, both native and foreign, to pay for really fine lacquered 
 articles sometimes more than their weight in gold, make it possi- 
 ble to get results not attained by our more hasty methods. 
 
 Amount of Lacquer Produced. Both Mr. Quin and Professor 
 Rein agree that the price of raw lacquer in Japan in 1880 was 
 about sixteen dollars a gallon, wholesale; and from investiga- 
 tions made by the latter and from ofiicial Japanese government 
 reports it appears that the total annual product of lacquer in 
 
178 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Japan was from 8,000 to 13,000 imperial gallons. Its specific 
 gravity is about the same as that of water. Quin says a tree 
 will produce enough lacquer to fill a three-ounce bottle; Rein 
 estimates an average yield much smaller, from one to two 
 ounces; while W. Williams, in "The Middle Kingdom," gives 
 twenty pounds to a thousand trees, or only one-third of an 
 ounce to the tree. No doubt the yield varies in different regions. 
 The trees are a regular crop, being set out by the farmer in plan- 
 tations, on land otherwise waste, and require ten years to mature ; 
 then the owner sells the whole crop of trees the "stumpage," 
 as lumbermen say to a contractor, who in the course of a single 
 summer destroys this ten years' growth for the sap it will pro- 
 duce ; and he has the dead timber to sell for firewood ; after which 
 the land is again set out with trees for another ten years' crop. 
 As an acre will support a thousand or twelve hundred trees, it 
 may produce from four to ten gallons of varnish in ten years. 
 
 The most noticeable thing about this matter is the small 
 amount of the annual product. At the time of writing this (in 
 1903) a single American company (the International Harvester 
 Company) are using 375,000 to 400,000 gallons of varnish annu- 
 ally, or thirty times as much varnish as the total yield of lacquer 
 in Japan; and this is a very minute part of the varnish used in 
 this country. On the other hand, sixteen dollars a gallon is 
 more than any one pays for any considerable amount of varnish 
 in America or Europe; it is not likely that ten thousand gallons 
 of varnish is sold in America, Great Britain, all Europe, and all 
 their dependencies, at half of sixteen dollars a gallon, in a year. 
 
 Our varnishes, of all sorts, dry best in a warm, light, dry room; 
 but these oriental lacquers dry best in a cold, wet, dark closet. 
 This is an extraordinary thing; it is now universally believed 
 that lacquer dries by the agency of a ferment. It is to be remem- 
 bered that there are two sorts of ferments, one which appears 
 to be some sort of a living organism, such as yeast; another, 
 such as diastase, which converts starch into sugar, is not an 
 organized ferment, and ferments of this sort are called enzymes. 
 One of these enzymotic ferments is present in this oriental lac- 
 
CHINESE AND JAPANESE LACQUERS. 179 
 
 quer, and it is through its action that the film is oxidized and 
 becomes hard. Enzymes are very sensitive to heat, whence it is 
 necessary to dry this lacquer at a low temperature and in a damp 
 atmosphere. Attempts have been made by chemists to study the 
 ferments of this lacquer, and the surprising and interesting state- 
 ment has been recently published that its ash contains a large 
 percentage of manganese. This is very singular; if a drying-oil 
 was used in the mixture, it is possible that a manganese drier 
 had been added, but there is nothing to warrant such an infer- 
 ence, which was certainly not believed by the investigator. 
 
 In conclusion, the present writer wishes to disclaim any 
 original knowledge of the subject or wish to be regarded as an 
 authority. It is said, on what appears to be good authority, 
 in fact, the reports come from many sources and through a long 
 time, that manila and similar varnish-resins have long been 
 imported into China; and if we ever get a complete knowledge 
 of the matter we shall very likely find that oleo-resinous var- 
 nishes, made from these resins and tong and Perilla oils, have 
 also been long known. The lacquer, being at once the most 
 valuable and the most remarkable of varnishes, is the only one 
 which has attracted attention; but this is merely a speculation. 
 
CHAPTER XV. 
 
 PROTECTION OF METALS AGAINST CORROSION. 
 
 FROM early times the use of paints and varnishes to prevent 
 the rusting of metals has been known to be of importance. Brass 
 does not, under ordinary conditions, rust deeply, but it tarnishes 
 quickly and needs some kind of a lacquer to preserve its surface; 
 but iron and steel are easily corroded, and the corrosion goes on 
 more rapidly as it progresses. Metallic iron does not exist in 
 any appreciable quantity in nature; the principal ores of iron 
 are hematite, which is the anhydrous sesquioxide, and limonite, 
 much more abundant than the former. It is evident from this 
 that there must be a great affinity between iron and oxygen, and 
 since most of the ore contains a little water, not as a mixture, 
 but in chemical union, it is plain that the presence of water is 
 favorable to this combination of oxygen and iron. This com- 
 bined water is so firmly united to the oxide that it can be driven 
 off only by prolonged heating to redness, but the oxygen is so 
 strongly bonded to the iron that it is only removed by heating 
 the ore to a white heat in intimate contact with white-hot carbon, 
 which has such an intense attraction for the oxygen that it is able 
 to take it away from the iron which is left in a molten condition 
 from the effect of the intense heat necessary for the decomposi- 
 tion of the ore. Such being the attraction between metallic iron 
 and oxygen, it is not surprising that they should readily com- 
 bine, even at ordinary temperatures. Their existence apart is 
 contrary to natural law, and sooner or later they will get together 
 in their natural union. All we can hope to do is to prolong their 
 separation as much as possible. It is said that iron will not 
 
 rust in perfectly dry air, but this is not of much practical impor- 
 
 180 
 
PROTECTION OF METALS AGAINST CORROSION. 181 
 
 tance because there is no such thing, except as it is chemically 
 prepared and kept in sealed apparatus in a laboratory. It does 
 not rapidly rust in the comparatively dry air of a desert; but 
 nobody lives in the desert to use it; yet these facts clearly show 
 that moisture is a great help to rust. 
 
 Conditions Favorable to Corrosion. The air not only con- 
 tains moisture, but also a small proportion of carbonic acid, and 
 it has been clearly demonstrated that this also is an important 
 aid to corrosion. Since iron in its various forms is the most 
 useful of all metals, it is naturally used in greatest abundance in 
 cities, and the air of cities always contains, from the burning of 
 coal, an excessive amount of carbonic acid and an appreciable 
 amount of sulphur in various forms, chiefly as sulphurous and sul- 
 phuric acid, which are intensely corrosive, and on the seacoast 
 the air also contains sea- water spray floating in it, which greatly 
 increases its corrosive action. It is well known that heat accel- 
 erates chemical action, hence the hot, moist, sulphurous, and 
 strongly carbonic gases ejected from a railway locomotive, or 
 from any other coal-burning furnace, are most powerful as cor- 
 rosive agents, and conversely the cold dry air of northern latitudes, 
 away from the seacoast or other large bodies of water, has the 
 least action; in such situations, indeed, in the winter the effect 
 seems to be so slight as to be hardly worth considering. 
 
 Such, in brief, are the conditions which favor corrosion, and 
 from their consideration it is clear that what is necessary to pre- 
 vent corrosion is some means to prevent the access of air and 
 moisture. It is attempted to do this sometimes by embedding 
 the metal in cement or concrete. This is to be considered good 
 practice, because the cement is not only nearly impermeable, but 
 it is also strongly alkaline, and of course the free alkali prevents 
 the access of acid to the metal. 
 
 Protection by Cement. It is, however, possible to over- 
 estimate the completeness of this protection, for it is sometimes 
 asserted that such cement or concrete is really impermeable, 
 which of course is not the case. Even neat Portland cement 
 porous, and in fact there are testing-machines for 
 
182 TECHNOLOGY OF PAINT AND VARNISH 
 
 measuring the porosity of plates of cement, so it is clear that 
 both air and water, that is, gases and aqueous solutions, may 
 circulate, more or less slowly, through it, and as concrete is practi- 
 cally used it contains numerous cavities which, while not affording 
 continuous channels, appreciably lessen its impermeability. 
 
 Important engineering works are often built of concrete rein- 
 forced by steel wires, rods, or beams, sometimes by riveted steel 
 frames, but depending largely on the strength and rigidity of the 
 cement. It is an important matter to know whether the steel in 
 such a structure is indestructible or not. As to that the writer of 
 this does not propose to express any decided opinion; but objec- 
 tions are always in order, if for no other purpose than to suggest 
 desirable precautions. In the first place, it may be observed 
 that the design of the builder is to make an artificial stone. Either 
 this must be monolithic or it must have expansion-joints. If the 
 former, it must be remembered that it is difficult to make a really 
 monolithic structure of considerable magnitude; for concrete 
 poured fresh on a surface of similar concrete which has been 
 allowed to stand a day or so, or sometimes only overnight, does 
 not form a strong bond to it, even when the greatest care is taken, 
 and the block thus formed will separate along the surface where 
 the interruption in work took place, if any great stress be applied. 
 
 Considerations Relating to Reinforced Concrete. To make 
 a really monolithic block the work of adding the concrete must be 
 continuous, 'and this is difficult to insure on very extensive work 
 lasting perhaps for weeks. The steel may be so placed as to 
 strengthen these joints, but it must not be forgotten that the 
 strength depends chiefly on the steel at such places, and also that, 
 although such a joint may be water-tight, it is a place where 
 there is a tendency for the concrete block to crack from changes 
 of temperature. Steel thus embedded can change in temperature 
 only very slowly, but it does change with the mass, and its rate of 
 expansion and contraction may be slightly different from that 
 of the concrete. 
 
 It may be conceded that if air and moisture are kept from 
 the metal it will not rust; but it is hard to be sure that water is 
 
PROTECTION OF METALS AGAINST CORROSION. 183 
 
 kept out of such a structure, and if the steel rusts it not only loses 
 its strength, but exercises a most destructive action on the sur- 
 rounding concrete, tending with immense force to split it to 
 pieces, because of the increase in bulk of the iron. If we were 
 selecting a building stone, would we choose one which was tra- 
 versed in every direction by streaks or long crystals of a mineral 
 very different in chemical and electrical qualities from the matrix ? 
 It may be doubted. Quarrymen would not regard such a rock 
 as sound, and would expect to find it split in pieces or disinte- 
 grated by the action of the weather. It seems reasonable, then, 
 to expect that great care is necessary, in building such, structures, 
 to insure continuity, and especially to prevent the soaking of 
 the whole mass with water from rain and melting snow; for con- 
 crete often has voids and porous places, and little attention to 
 making its surface water-proof is usually given. Above all, pro- 
 vision should always be made for drainage, and this is too often 
 neglected ; the whole mass is soaked and sodden with water which 
 lies there month after month. 
 
 Expansion-joints. Some of these objections do not apply 
 to blocks of reinforced concrete put together with expansion- 
 joints. In these structures it is clear that the atmospheric water 
 will have access to the joints, and in cold weather will by freezing 
 tend to injure them unless it can be kept out by some elastic 
 water-proof packing or can be perfectly drained; perhaps both 
 precautions are not too much. It is difficult to permanently 
 close a crack in concrete, and it may be doubted if there has 
 yet been built a large mass of it, without expansion-joints, which 
 has not cracked. These cracks naturally lead to weak places 
 in the interior and conduct water and air to these unknown 
 and inaccessible recesses, perhaps to hasten the destruction of 
 the inclosed steel on which the strength of the structure depends. 
 
 Should the steel in such structures be painted? The objec- 
 tion commonly made is that in order to get the utmost advan- 
 tage from the use of the steel, we must have the concrete adhere 
 perfectly to it, so that there shall be no break in continuity between 
 the cement and the metal, and the latter shall be a part of the 
 
1 84 TECHNOLOGY OF PAINT AND VARNISH. 
 
 concrete in the same sense that the broken stone is. Is this 
 possible? The fragments of broken stone are of somewhat 
 similar nature with the cement. Their elasticity and rate of 
 expansion is the same; they exist in little isolated pieces, not 
 in long threads or flat plates, and their rough surface and irregu- 
 lar shape are perfectly adapted to the adhesion of the matrix. 
 It is not so with steel. It is frequently said experiment has 
 shown in a testing-machine that cement adheres to iron with a 
 force equal to its own cohesion, and this may be correct if proper 
 care is taken to make it a direct pull. But probably every one 
 has seen cement part from a steel surface without much resist- 
 ance, even if the surface was specially prepared for it. There is 
 not much difficulty in rattling the dried cement off a shovel, 
 for instance; and it is quite likely that in any case where the 
 enormous elasticity of steel comes into play and it is because 
 of its strength and elasticity that it is used the so-called bond 
 which exists between the cement and the metal is of very little 
 account. This bond is sometimes spoken of as though it were 
 something mysterious and sacred, but it may be doubted if cement 
 sticks to iron in any different way from what anything else does 
 or from what cement sticks to anything else. A definition of 
 this bond would tend to a clearer conception of the whole matter, 
 and it might then be found that an elastic and water-proof film 
 between the metal and the cement which would lend itself a 
 little to the differences in expansion was a source of strength 
 and permanence rather than weakness. A subject like this is 
 too important and too intricate to be approached with a feeling 
 of prejudice and a determination to settle the matter ex cathedra. 
 We have not yet got to the last word about reinforced concrete; 
 it is very true that time and use are the final test, and that some 
 of the earlier structures are still in good condition, but the earlier 
 structures were built by men who were in some sense inventors 
 and experimenters, and the work of an enthusiast is likely to 
 be much more carefully done than that of a man who works by 
 a formula. 
 
 Asphaltic Cement. A really impermeable cement is one 
 
PROTECTION OF METALS AGAINST CORROSION. 185 
 
 made of asphaltum applied in a melted condition; when of suit- 
 able composition and sufficient thickness this seems to be as 
 nearly perfect a protection as anything which has been devised. 
 Coal-tar pitch, which resembles asphaltum in appearance, is 
 usually an acid substance and should not be used for these pur- 
 poses, and it is not to be forgotten that asphaltum is mixed with 
 all sorts of things, some of which are not injurious if not used 
 in too great quantity, but the best of which usually so dilute the 
 asphalt, which is the real cementing material, as to lessen its 
 permanence. 
 
 To be of any value as a cement asphaltum must be tough 
 and somewhat flexible, a quality usually obtained by using a 
 naturally soft asphalt, or by tempering a harder asphalt with a 
 heavy mineral oil; in either case the elastic or softening ingre- 
 dient tends to be removed by atmospheric action, and still more 
 by the effect of the weather or of water, and it is necessary to 
 have a considerable thickness of cement over the metal, not 
 less than an inch, and better two or more inches, when efficient 
 protection may be reasonably expected. Such an asphaltic 
 cement is not only tough and flexible, but it is also viscous. It 
 will, especially in warm weather, flow slowly. This naturally 
 prevents its use in places where it can run off. It is used for 
 covering rail way- bridge floors, and when used in sufficient quan- 
 tity and with a reasonable appreciation of its properties satis- 
 factory results have been attained. An important use for ma- 
 terial of this sort is in coating water-pipe, a subject which will 
 be treated as a separate topic. These methods deserve fuller 
 treatment, especially the use of Portland cement, but at the 
 present time there is but little accurate knowledge and especially 
 hardly any which has been tabulated or otherwise made accessible 
 on the subject of hydraulic cement for such use, and the making 
 of serviceable mixtures of asphalt is in the hands of the great 
 asphalt paving companies, who do not make it known, so that 
 this must be left for some better-informed writer in the future. 
 
 Thinness of Films. We come, then, to the problem of pro- 
 tecting metal from corrosion by the use of films of varnish and 
 
186 TECHNOLOGY OF PAIN1 AND VARNISH. 
 
 paint. The statement of the problem involves naming its great- 
 est defect, which is that films are depended on for more or less 
 permanent protection, and these films are only one or two thou- 
 sandths of an inch in thickness. They are, therefore, easily 
 scraped off or removed by any sort of abrasion. They are not 
 very hard and are easily punctured, and if they are at all porous 
 the pores, which will naturally be at an angle to the surface of 
 the film, will extend through it because the distance is so little. 
 If the matter is fairly considered, it seems almost preposterous 
 to apply a film one or two thousandths of an inch thick to protect 
 a steel plate or beam an inch or more in thickness in a situation 
 where the uncoated metal would be destroyed in a short time, 
 yet this is what is constantly demanded, and it is also asked that 
 this material should be such as may be applied by unskilled 
 labor and to any kind of a surface. It is a wonder that any 
 favorable results are reached, yet they must be or the varnishes 
 and paints would not be used. 
 
 Paint is Engineering Material. Protective coatings, as applied 
 to structures designed by engineers, are engineering materials, 
 just as much as are the plates and beams to which they are applied. 
 When an engineer designs a structure, he makes it usually from 
 three to five times as heavy as the load actually requires, "for 
 safety"; really this factor of safety is so large chiefly to provide 
 for future deterioration, and a part of this excess of metal is added 
 to secure the rest of it against rust, which is exactly what the paint 
 is used for; hence the latter is fully as much engineering material 
 as the steel which it covers, and deserves just as careful and serious 
 consideration from the engineer which it seldom gets. Part of 
 the indifference to the subject is due to the fact that the engineer 
 feels that he is rather ignorant of the matter and concentrates 
 his interest on steel, of which he thinks he knows a great deal, 
 though it may be suspected that the chemists in the steel- works 
 have their own doubts about even that; but at any rate he has 
 books of tables of figures relating to steel, and these are a source 
 of satisfaction. The imaginative, the mathematical, the construc- 
 tive part of engineering is and must always be a delight to the 
 
PROTECTION OF METALS AGAINST CORROSION. 187 
 
 mind of the engineer, and is essentially different from that part 
 which has to do with the qualities of materials, which are best 
 understood, and even then only imperfectly known, by the experts 
 who make a business of their manufacture. 
 
 Protective Coatings not Necessarily Decorative. It has 
 already been said that varnish and paint are used both for decora- 
 tive effect and for protection of the underlying materials, and as 
 the decorative effect is the more conspicuous, most people regard 
 that as the primary quality; and when we speak of protective 
 coatings the idea of decorative effect underlies, in their minds, 
 the whole matter, perhaps unconsciously. By the very term 
 used it is, however, eliminated. The decorative effect has abso- 
 lutely nothing to do with the subject. Fortunately this con- 
 dition, that no attention whatever shall be paid to decorative 
 effect, can in most cases be enforced, because such effect may be 
 reached by decorative painting over the protective coating, not 
 only without injury, but in most cases with positive benefit to 
 the latter. This is an important consideration, for it enables us 
 to use materials which are quite unsuited for decorative use. 
 For example, a paint or varnish as commonly used must dry 
 " dust-free," i.e., so that dust will not stick to it, in about twenty- 
 four hours, or less, because every hour adds to the danger that 
 the beauty of the surface will be destroyed or injured by the 
 adhesion of dirt, insects, etc., and this quality of quick drying is 
 almost always obtained by the excessive use of driers which, as 
 has been already explained, greatly lessens the durability of the 
 compound, or else by the use of too large a proportion of resin- 
 ous matters, which makes a brittle coating which cracks with 
 changes of temperature, or too much volatile solvent is used, 
 which diminishes the proportion of cementing material and pro- 
 duces a film which is lacking in coherence. If, on the other 
 hand, we may leave out of account the looks of the paint or 
 varnish, it is clear that we are at liberty to use anything which 
 will add durability and impermeability to the film, which, in 
 most cases, may be allowed a long time to dry and may have a 
 comparatively rough and wrinkled surface. Thus, the members 
 
1 88 TECHNOLOGY OF PAINT AND VARNISH. 
 
 of a bridge are usually made up several weeks before erection, 
 and a first coat has all this time to dry and harden; then it is 
 painted after erection, and in most cases this coat may have all 
 the time necessary. Probably in most cases the next coat will 
 not be applied for some months, and in any subsequent painting 
 the use of a slow-drying paint does not interfere with the use 
 of the structure. Of course there are considerations which pre- 
 vent the use of non-drying or too-slow-drying materials: they 
 are liable to be rubbed off or even removed by the action of the 
 weather; it is desirable to have a paint or varnish which sets 
 within a reasonable time, say a day or two, but it may be allowed 
 to dry slowly after that, taking up its last portions of oxygen 
 only after a long period, and it is films of this nature, which show 
 a continually increasing reluctance to oxidize, which have the 
 greatest permanence. To exhibit a very smooth surface a paint 
 or varnish must contain a considerable proportion of resinous 
 matter; and while a certain amount is highly desirable, because 
 it acts as a flux and prevents the formation of pores, a quantity 
 sufficient to give a hard and very lustrous surface causes a lack 
 of elasticity which may be the occasion of cracks in the coating, 
 but a film intended only to protect against corrosion may have 
 exactly the most desirable ratio of ingredients. Decorative paints 
 must be made with certain pigments, and sometimes these are the 
 cause of deterioration; but an injurious pigment should be excluded 
 from protective coatings, which should contain only the best and 
 most suitable compounds for the purposes for which they are 
 made. 
 
 The preparation of the surface to which the protective coat- 
 ing is to be applied is a subject the consideration of which natu- 
 rally precedes that of the material itself and of the method of its 
 application. A great many years of experience and observation, 
 and of consultation with painters and with engineers, have con- 
 vinced the writer that paint and varnish adhere to a metal sur- 
 face in the same way that other things do, and that the same 
 conditions which favorably influence the adhesion of other coat- 
 ings are desirable in the use of these substances ; also that, making 
 
PROTECTION OF METALS AGAINST CORROSION. 189 
 
 due allowance for the impermeability of a metallic surface as 
 compared with a wooden one, the same principles which govern 
 their application to all other surfaces apply to their use on iron 
 and steel. Such statements as the foregoing will not probably 
 appear to the disinterested and speculative reader to be unreason- 
 able, much less revolutionary and inimical to all industrial prog- 
 ress, and he cannot fail to be interested in knowing that not only 
 the ordinary contractor but the great steel companies (who natu- 
 rally ought to be interested in the permanence of their products) 
 regard an engineer who tries to adapt these maxims to practical 
 work as a visionary theorist, to be humored when necessary and 
 evaded if possible, while the paint or varnish manufacturer who 
 promulgates such propositions is a dangerous crank, about as use- 
 ful to society as an anarchist. " That, " said the manager of one of 
 the great bridge companies, "is a good paint, but it always makes, 
 me laugh when I see a barrel of it; observe the notice on the 
 barrel-head: 'Do not thin this with anything.' Well, we thin it: 
 just the same. Oh, we have to thin it a little, you know, or we 
 couldn't put on two coats; with the same brush, you know; one 
 coat going this way" with a sweep of the arm indicating a free 
 and powerful artistic treatment "and the other" with a. 
 return sweep "going this way. Why," plaintively, "do you. 
 suppose we wish this steel to last forever?" "I suppose," said I 
 sadly, "you consider me an enemy of the human race." "Oh, 
 no, you're a good fellow, but you are an enemy of the steel men. " 
 Apply Paint to a Clean Surface. The most important con- 
 dition affecting the adhesion of any coating to any metal is that 
 it should be applied to a clean metallic surface. If the surface 
 is covered with dirt or grease, the coating does not come in con- 
 tact with the metal and so does not adhere to it ; and if the dirt 
 comes off, the coating comes with it. It might be supposed that 
 grease would be absorbed by the paint or varnish, but the coating 
 of grease or oil does not very readily mix with these. If it were 
 desired to mix such things, it would ordinarily be thought neces- 
 sary to agitate them thoroughly together. But an important 
 consideration is that the grease is always mixed with and covered 
 
TECHNOLOGY OF PAINT AND VARNISH. 
 
 by an adherent film of dirt which interferes with the action of 
 the paint or varnish upon it, which consequently makes a film 
 on a loose, greasy foundation. Further, the oil or grease is usually 
 a mineral oil, sometimes mixed with rosin or rosin-oil, and if 
 mixed with the regular coating will destroy the characteristic and 
 valuable qualities of the latter. Iron and steel beams and the 
 like should not be laid on the ground, but on skids or trestles. 
 They are heavy and press into the earth, which adheres to them ; 
 in wet weather they become covered with mud, which the con- 
 tractor strenuously objects to removing before painting. "Do 
 you expect me to clean this iron with a tooth-brush?" was the 
 angry protest of the manager and one of the principal stock- 
 holders of one of the largest construction companies in New 
 York, when the engineer was urging him to wash the mud off the 
 beams which had been lying in the street, although his contract 
 specified much more thorough cleaning than he was asked to do. 
 Sometime when steel becomes more costly than it is now, or 
 opinion on these matters becomes more enlightened, it will be 
 kept under shelter until the time comes for its erection. 
 
 Mill-scale. But oil and dirt are not the only things found on 
 steel. All structural metal as it comes from the mill is covered 
 with mill-scale, which is the black oxide of iron resulting from 
 the action of air on the hot metal. Frequently this scale is in 
 several layers; sometimes these stick together rather firmly, 
 sometimes the outer layers separate readily from those beneath. 
 Steel plates are often coated with a thin blue or iridescent mill- 
 scale, which immediately overlays the unoxidized metal, to which 
 it sometimes adheres with great tenacity. This is the anhydrous 
 sesquioxide, and is exactly similar in appearance and compo- 
 sition to the beautiful iridescent specimens of hematite ore which 
 may be seen in any mineralogical collection. This is an extremely 
 refractory substance, insoluble in acid, and might be thought to 
 be a sufficient protective coating in itself, but it is hard and not 
 very elastic, and its rate of expansion differs from that of the 
 metal, so that it soon becomes a network of cracks, which allow 
 water to reach the underlying metal, which then rusts and the 
 
PROTECTION OF METALS AGAINST CORROSION. 191 
 
 rust creeps under the little patches of scale and they are thrown 
 off. This may be easily seen by immersing a piece of such iron 
 in acid, which can reach the metal only through the cracks in the 
 scale. Scale which is of a more pulverulent character offers 
 little or no resistance to atmospheric agencies, but it does not 
 scale off easily unless in deep layers. .It is dangerous to leave 
 such oxide in contact with the iron, for it absorbs and holds in 
 contact with the metal the moisture and acids in the air and in 
 various ways acts to induce further and deeper oxidation. It 
 might be thought that saturating the oxide with oil would prevent 
 any further change, but this idea, though it crops up from time 
 to time and is the base of many a humbug in the paint line, is not 
 in the least supported by practical experience. I do not mean 
 to say that a surface covered with mill- scale, or even with ordinary 
 rust, may not be benefited by a good paint or varnish. These 
 coatings will undoubtedly retard the further action of rust, but 
 do not prevent it. More than a hundred years ago, Smeaton, 
 one of the greatest engineers of his time, said he "had observed 
 that when iron once gets rust, so as to form a scale, whatever coat 
 of paint or varnish is put on over this, the rust will go on pro- 
 gressively under the paint." The following century of obser- 
 vation has made no change in this remark, which is only confirmed 
 by longer experience. 
 
 Rust must be Removed. Iron and steel are of a grayish- white 
 color. When it is desired to coat articles of this metal with 
 porcelain or a vitreous enamel the workman finds it absolutely 
 necessary to have the surface show this color of the pure metal 
 in all its parts, for if there is any scale or rust on the surface, 
 even in minute spots, the enamel will chip off at those places. 
 This clean surface he gets by clearing off the scale with acid, in a 
 manner to be described later, or by the use of the sand-blast, or 
 sometimes by scraping and polishing the metal. At all events, 
 the enamel is applied to the metal and never to an intermediate 
 coating. The electroplater, who deposits another metal, such as 
 copper or nickel, on iron, is equally thorough. The bicycle- 
 maker, who covers his frames with a japan enamel, cleans them 
 
TECHNOLOGY OF PAINT AND VARNISH, 
 
 in the most perfect manner on an emery- belt, after which they must 
 not be touched even with the finger until the enamel is applied. 
 In making tin-plate, the iron plates are cleaned by acid and go 
 direct from the acid-bath to the pot of melted tin, for otherwise 
 no adhesion will take place. Galvanizing, or plating with zinc, 
 is done in the same way. 
 
 No Coating will Stand over Oxide. Excepting the painter, 
 every one who applies protective coatings to iron or steel insists, 
 as a matter which will not admit of discussion, on the absolute 
 and fundamental necessity of removing not merely all loose scale 
 and dirt, but absolutely all scale and all oxide, so as to apply the 
 coating to the pure metallic surface. Otherwise it has been found 
 that, sooner or later, the oxide will separate from the metal surface 
 and of course the superimposed coating has to come off. This 
 is what I mean when I say the conditions which favorably influence 
 the adhesion of other coatings are desirable for the application 
 of varnish and paint, and it is this idea of having an absolutely 
 clean metal surface on which to apply these coatings which seems 
 the extravagant dream of a doctrinaire to the ordinary contractor, 
 who will tell you that paint forms a continuous, film and keeps 
 out the air and water, so that there can be nothing to cause the 
 closely adherent oxide to separate from the metal. It is a suffi- 
 ciently complete answer to this argument to repeat that universal 
 experience shows that nothing can prevent it in practice. If it 
 cannot be done with such a perfect coating as electroplate or a 
 vitreous enamel, nor with a coating which in some respects is 
 even more remarkable, namely, one of baking- japan, which more 
 nearly resembles a varnish or paint, it is idle to expect it with 
 these latter, which are in their nature somewhat porous and 
 with which we have to obtain protection by putting one coat on 
 over another, trusting to the successive coats to fill up the pores 
 .and imperfections of those beneath. There is no doubt in my 
 mind that the right way to prepare a steel or iron surface for 
 painting is to clean it so that the gray color of the metallic iron 
 will be everywhere seen. This may be done in some cases by 
 scraping, in some by pickling in acid, in others by the sand-blast, 
 
PROTECTION OF METALS AGAINST CORROSION. IQ3 
 
 but in all the cost will be considerably more than is now com- 
 mon, because more work is done and a better result achieved. 
 Money judiciously spent to get a good surface is wisely invested; 
 no one doubts that it is if really high-class work is in question. 
 No doubt there is a great deal of work of a more or less tem- 
 porary nature where the cost of such high-class treatment is not 
 justified, but there is no place where a protective coating is called 
 for where it is not worth while to make some effort to secure a 
 fairly good surface, free from mud and dirt and loose scale, for 
 the varnish or paint. We may also consider the practice of the 
 painter who works on wood. No one ever thinks of painting 
 on wet wood; the paint will not stick; if it does not immediately 
 come off, it will subsequently blister; and even in such rough work 
 as exterior house-painting the painter removes all loose dirt, 
 old paint, etc., by scraping and brushing, as a preliminary; in 
 fine work, such as repainting a carriage, the old paint is removed 
 by scraping or burning off, and the surface made clean and 
 smooth and properly prepared by special fillers, so that the paint 
 or varnish may go on in a coat of uniform thickness to a surface 
 for which it has a natural affinity. Thus it will be seen in all 
 other painting the proper condition of the surface is a subject 
 of practical consideration, and its preparation a matter of serious 
 care. This also indicates that like precautions should be taken 
 with steel, in fact greater, because steel is in most situations 
 more perishable than wood. 
 
 Why Steel is not Fairly Treated. The curious reader will 
 perhaps wonder why it is that difficulty should be found in hav- 
 ing steel properly cleaned and painted. Primarily the trouble 
 is with the engineers who design and direct the work. If they, 
 as a class, felt the importance of the matter and were always 
 as strenuous about it as they are about the mechanical details, 
 and made it a rule to include in their estimates a reasonable 
 amount for having such work properly done, there would then 
 exist a better general practice, and if the average were higher 
 it would be comparatively easy to get really high-class work 
 done. Structural steelwork goes mainly into two classes, bridges 
 
194 TECHNOLOGY OF PAINT AND VARNISH. 
 
 and the framework of buildings. The building with a steel 
 framework is primarily designed by an architect who, while 
 not without engineering knowledge, hands over the details of 
 construction to an engineer. The chief architect himself is 
 mainly concerned with the design of a building suitable in its 
 general and detailed arrangements for the purposes of the owner 
 and in having its artistic features and its ornamental details as 
 agreeable as possible, and strict regard must and should be had 
 for economy of construction. Usually a sum to be expended is 
 fixed upon at first , and the common experience is that for various 
 reasons the estimated cost is finally exceeded. The architect 
 usually does not know or claim to know much about protective 
 painting. The engineer is sometimes directly and sometimes 
 indirectly in his employ and receives his directions. He is, 
 therefore, not finally responsible and, not being oversupplied 
 with subordinates, does not feel like assuming unusual authority 
 or cares. The metal framework is to be eventually covered from 
 sight, and as it is inclosed it is not as likely to rust as though 
 exposed; and above all, the current practice of architectural 
 engineers is to be indifferent about painting, so that, with lack 
 of responsibility, lack of authority, disbelief in the vital impor- 
 tance of the subject and accordance with current practice, the 
 engineer leaves the painting largely to the contractor, and it is 
 unreasonable to expect the latter to spend money for material 
 or labor which are not called for. Further, it is commonly the 
 case that when the money to build with is ready it is important 
 to get the building done as soon as possible. So the steel is 
 rushed through the shops as rapidly as may be; when it is de- 
 livered it is in the street in front of the building, and the building 
 permit is limited; hence it cannot stay there, but must be put in 
 place at once, and then the masons are waiting and there is no 
 time to paint. 
 
 Stone does not Rust. The engineer consoles himself by 
 thinking that he has done the best he can and as well as other 
 people do; and in fact the engineer who holds that life is too 
 short to be studying this paint question and that there is no oppor- 
 
PROTECTION OF METALS AGAINST CORROSION. 195 
 
 tunity in the construction and erection of metal-work for its 
 proper application may feel confident that he has good com- 
 pany and plenty of it; but his attention may be called to the 
 fact that some of our best and most important railroads have 
 gone back to the construction of enormously expensive stone 
 bridges simply because stone is reliable, while steel, as now 
 treated, is not. 
 
 As to bridge construction, it is common practice for one 
 department, whether of a private or public corporation, to design 
 and erect a bridge, and then turn it over to another department 
 for maintenance, and the bridge engineer holds that painting 
 is a part of maintenance, and that he may build the bridge with- 
 out regard to paint and let the engineer of maintenance paint it 
 as often as he likes. Hence it is of no use to try to interest such 
 a bridge engineer in materials or methods of painting. A little 
 consideration will show that this position is untenable if, as 
 has been claimed, paint is engineering material. The construct- 
 ing engineer might as well say that, as defective rivets and bolts 
 have to be renewed by the department of maintenance, it is of 
 no importance to him what is the quality of material or work- 
 manship employed in riveting. The place to begin painting 
 is on the metal, and the first coat is of more importance than 
 any subsequent one. My own belief is that a bridge should 
 never, except for decorative effect, be repainted throughout; 
 it should be well and properly painted when built, and any spots 
 which are defective should be repainted from time to time, pre- 
 cisely as all other repairs are managed; no one would think 
 of conducting other repairs in any other way, and the paint is 
 just as much a part of the bridge as any other material and should 
 be treated in the same way; and I am glad to be able to say that 
 some of the best-maintained railways have adopted this practice. 
 
 Scraping. This doctrine that rust and scale should be re- 
 moved as much as possible before painting is, of course, no new 
 thing; and the earliest method, and one which will always be 
 in many cases the only one available, was to clean the surface 
 by scraping. The most common scraper is one made by grind- 
 
196 TECHNOLOGY OF PAINT AND VARNISH. 
 
 ing the end of a large mill-file, which makes an efficient tool. 
 But there are many places which cannot be reached with such 
 an instrument, and now the workman is provided with sets of 
 scrapers of different widths, and with a hammer and chisel, which 
 are sometimes necessary. The common straight scraper is 
 operated by pushing, but others are made with the scraping end 
 bent at a right angle to the shank, which are pulled, like a hoe, 
 toward the operator. These are also made in different widths. 
 The edge of a scraper is naturally straight like that of a chisel, 
 the workman is also sometimes provided with one or two 
 ones having the edge serrated, like the teeth of a saw or of 
 a serrated ice-chisel, and these are useful for breaking up scale 
 so that it may more easily be removed. 
 
 Wire-brushing. After the scraping it is customary to go 
 over the surface with a wire brush, which leaves a good surface, 
 but the brush alone is not an efficient instrument. In my own 
 laboratory there is a rotary wire brush driven by power with a 
 peripheral speed of about five thousand feet per minute. A 
 suitable table is arranged so that the piece of metal to be cleaned 
 may be mechanically held at the right place and the brushing 
 may be continued as long as the operator desires. This is prob- 
 ably the most favorable condition for the use of a wire brush, but it 
 is found that even here it is impossible to remove scale which 
 adheres closely or which is very thick. I conclude, then, that 
 the wire brush is not sufficient and that its use should be pre- 
 ceded by scraping. The painter's torch is sometimes used as 
 an accessory. This throws a jet of flame on the surface of the 
 metal, and as the rust and scale become much more heated than 
 the metal they tend to crack off and are more easily removed, 
 and any water which is held in their interstices is driven off, but 
 of course the hydrated oxide is not dehydrated in the chemical 
 sense, for it requires a much higher heat to do this, as has been 
 already explained. Bridges which have been erected can usually 
 be cleaned only in such ways as have been just described, although 
 on some railroads bridges in place, especially old ones, are cleaned, 
 usually in part only, by the sand-blast. Those parts of the 
 
PROTECTION OF METALS AGAINST CORROSION. 197 
 
 bridge which are most badly rusted are cleaned with the sand- 
 blast, and the rest of the bridge with scrapers and wire brushes, 
 on the theory that the most exposed parts need the most care 
 and that the less rusted members will last long enough with 
 more inexpensive treatment, which is doubtless correct. 
 
 Sand-blast. The most thorough and perfect manner of 
 cleaning metal in any mechanical way is by the sand-blast, which 
 is a stream of particles of sand thrown with great velocity against 
 the surface; the grains of sand have sharp cutting edges and 
 partly by cutting and partly by the impact or hammering of 
 these little pieces of quartz the scale and rust are cut and broken 
 up and removed. It has been proposed to throw the sand with 
 levers, as from a catapult, or by centrifugal force, but the only 
 practical way is to mix it with an escaping current of compressed 
 air, which carries it along with great velocity, hence the name. 
 This method of applying power for cutting and abrasion was 
 invented by Gen. Benj. G. Tilghman, of Philadelphia, and 
 was patented by him Oct. 18, 1870, the patent being numbered 
 108,408. 
 
 Among the most important claims granted by that patent 
 were the following: 
 
 1. The cutting, boring, dressing, engraving, and pulverizing 
 of stone, metal, glass, pottery, wood, and other hard or solid 
 substances by sand used as a projectile, when the requisite veloc- 
 ity has been imparted to it by any suitable means. 
 
 2. The artificial combination of a jet or current of steam, 
 air, water, or other suitable gaseous or liquid medium, with a 
 stream of sand, as a means of giving velocity to the sand when 
 the same is used as a projectile as a means of cutting, boring, 
 dressing, etc., etc. 
 
 7. When a jet or current of steam, air, water, or any other 
 suitable gaseous or liquid medium is employed to give velocity 
 to sand used as a projectile, as a means of cutting, boring, dress- 
 ing, etc., the use of the following devices for introducing the sand 
 into the jet of steam, air, water, etc. First, the suction produced 
 by the jet of steam, air, water, etc. Second, a strong, close vessel, 
 
198 
 
 TECHNOLOGY OF PAINT AND VARNISH. 
 
 or sand-box, into which the pressure of the steam, air, water, 
 etc., is introduced and through which, when desired, a current 
 of it may be made to pass. 
 
 It is obvious from the foregoing that there is no existing 
 patent on the process, and while there is some patented apparatus 
 which is preferred by some of the people who use the process, 
 this is equally true of a very large proportion of all machinery 
 in use. 
 
 The Tilghman apparatus as improved and patented by 
 Mathewson is shown in section in the following illustration, 
 
 MATHEWSON'S SAND-BLAST. 
 
 (TRADE NAME, TILQHMAN.) 
 
 Hose with 
 Special End 
 
 In this apparatus a slotted slide, operated by a lever, regulates 
 
PROTECTION OF METALS AGAINST CORROSION. 199 
 
 the quantity of sand introduced into the current of air. This 
 machine was patented Dec. 25, 1894; No. 531,379. 
 
 In the Paxson- Warren machine, shown in the next figure, the 
 
 Pipefrom WARREN'S SAND-BLAST. 
 
 Air Receiver (TRADE NAME, PAXSON-W.ARREN4 
 
 Straight Hose 
 
 feed of the sand is regulated by a revolving piece, or valve, which 
 covers the opening in the bottom of the hopper to the extent 
 desired to let the proper quantity of sand fall through it and into 
 the air-pipe. 
 
 In the machine patented by J. M. Newhouse of Columbus, Ohio, 
 shown in the illustration on the next page, the sand passes from 
 the hopper at the bottom through an annular opening around the 
 end of a nozzle-shaped steel piece, which decreases in its outer cir- 
 
200 
 
 TECHNOLOGY OF PAINT AND VARNISH. 
 
 cumference toward the end and, by raising or lowering it, this 
 annular opening may be increased or diminished in size. The 
 distinguishing feature of this appliance is the use of this nozzle as 
 a siphon with its perforation as shown. The small holes permit 
 part of the air which flows through the small pipe and the siphon 
 
 THE NEWHOUSE SAND-BLAST. 
 
 to escape outwardly through the surrounding sand, thus stirring 
 it up and preventing it from clogging the opening. A similar 
 siphon, without the perforations, is placed in the air-pipe. 
 
 The process of cleaning with the sand-blast is essentially 
 as follows: Air at a pressure of 20 to 25 Ibs. per sq. in. is fur- 
 nished by any suitable air-compressor. If we assume that we 
 
PROTECTION OF METALS AGAINST CORROSION. 2OI 
 
 will use a discharging-nozzle T 9 g- in. internal diameter, when 
 new, each such nozzle will require 120 cu. ft. of air per minute, 
 measured at atmospheric pressure compressed to show a pres- 
 sure of 15 Ibs. per sq. in. at the nozzle. This is, however, to 
 be regarded as a minimum, for it is advisable to use a somewhat 
 higher pressure, say 20 Ibs., and the nozzle rapidly wears away 
 until it reaches a diameter of f in., at which it will discharge 
 nearly twice as much as when new, so that in practice it is well 
 to provide an air-compressor handling 240 cu. ft. of air per minute 
 and compressing the same to 20 Ibs. per sq. in. Recent work 
 has shown that a pressure as high as 35 Ibs. per sq. in. is desira- 
 ble and economical for removing heavy scale, which a blast at a 
 lower pressure will not remove. 
 
 Into this current of air dry sand is introduced at the rate of 
 about 10 cu. ft. of sand per hour for each such nozzle, or i cu. ft. 
 of sand to 1000 cu. ft. of air. The sand must be artificially 
 dried; some operators use coarsely powdered quartz. This, 
 latter can be used five times in succession; and in general the 
 sand may be used until it is broken up into a powder too fine 
 for use. In the plants which the writer has inspected the sand 
 and air are carried to the nozzle through a heavy rubber hose 
 about 2\ in. diameter. This is not worn away by the current 
 as a metal pipe would be, but it is necessary that the air should 
 not be hot, as this would rapidly injure the hose. The nozzles 
 are short pieces of extra-heavy iron pipe and have to be renewed at 
 frequent intervals. From data furnished me by Naval Con- 
 structor Bowles I find that the cost of cleaning the bottom of a 
 ship in dry dock amounted to about 4 cents per square foot, but this 
 was done with an experimental plant, and the method of drying- 
 the sand, which was used only once, was costly, and the cost 
 would certainly have been reduced to 3 cents per square foot if a 
 permanent plant had been in use. Since the installation of a 
 permanent plant no work has been done of sufficient magni- 
 tude to give figures. This was an exceedingly rusty surface, 
 but with this same experimental plant the mill-scale was removed 
 from 3,155 sq. ft. of surface of steel plates at a cost of $17.60, 
 
202 TECHNOLOGY OF PAINT AND VARNISH. 
 
 or about i cent per square foot anci at the rate of 4! sq. ft. per 
 minute per nozzle. 
 
 It may be well to add that in all the work referred to, which 
 was practically field work, being carried on out of doors and 
 with a somewhat portable plant, the labor amounted to one man 
 to hold each nozzle, one man to attend to each two sand-boxes, 
 and one man to clean up and carry sand for each four nozzles. 
 The supply of compressed air is an expense of a different sort, as 
 is also in field work the matter of staging, etc., but all are included 
 in the prices given. It seems reasonable to suppose that where 
 many pieces of metal of the same general character are to be 
 treated in a shop fitted up for the purpose, contrivances may be 
 introduced which will do away with a considerable part of the 
 labor. 
 
 4 Pickling. Iron and steel may also be cleaned by pickling in 
 acid and the subsequent removal of the latter. This may be done 
 in the following manner: The pieces of metal which have been 
 made ready for assembling are immersed in hot dilute sulphuric 
 acid having a strength of 25 to 28 per cent. Some use acid of 20 
 per cent. It is kept in this until the whole surface is free from 
 rust and scale. This will take from six to twelve minutes. If the 
 pieces of metal are somewhat rusty, so that rust has started 
 underneath the scale, the shorter time will be found sufficient, 
 but if it consists of plates covered with closely adherent blue or 
 iridescent rolled scale, the longer time will be necessary, since 
 this scale is itself insoluble in acid and is removed by the latter 
 penetrating the innumerable minute cracks in the scale and 
 attacking the iron underneath, thus mechanically throwing off 
 the scale. If, on the other hand, the iron is uniformly rusty, this 
 coating of hydrated oxide readily dissolves in acid, and in fact 
 a weaker acid of 10 to 12 per cent, might be used, although 
 the stronger acid is quite safe but will require a shorter time. It 
 has been suggested that it is desirable to previously clean the 
 metal with caustic alkali from all grease, etc., but if acid of the 
 above strength is used and kept as hot as possible this will not be 
 necessary. As soon as the acid has reached the iron in all parts 
 
PROTECTION OF METALS AGAINST CORROSION. 203 
 
 of the surface, the metal is taken out and washed by jets of water 
 discharged against it under high pressure, not less than 100 Ibs. 
 per square inch and much better if double that. In this way the 
 acid may be thoroughly removed. 
 
 In Germany it is said to be customary to use acid of 9 or 10 
 per cent, cold, and the metal is left in it five hours. This makes 
 a much larger plant necessary and has no advantages. 
 
 If it is attempted to remove the acid by soaking the metal 
 in still water, the following difficulty is encountered: the iron 
 becomes immediately coated with a gummy or colloidal substance, 
 very difficult to remove. What this is, is not known to the writer, 
 but is it well known that there are a number of insoluble or diffi- 
 cultly soluble compounds of iron with sulphuric acid, and it is 
 probable that some of these are precipitated on the surface of the 
 iron when water removes the excess of acid, but if a jet of water 
 is used the mechanical effect is to remove trie adherent ferrous 
 sulphate at the same instant, leaving a clean metallic surface. 
 It is also possible that if the acid contains arsenic, as is the case 
 with much of the acid made from pyrites, this may also be pre- 
 cipitated on the surface. In fact, it is sure to be, and acid free 
 from arsenic should always be used for this purpose, and as a 
 matter of practice it is insisted on by many. 
 
 It is often difficult, and sometimes impracticable, to pickle steel 
 high in carbon and cast iron containing graphitic carbon, on account 
 of the deposit of a film of carbon like stove-blacking on the surface. 
 Muriatic (chlorhydric) acid has been used instead of sulphuric, 
 but it is not well suited for the purpose, being much more expen- 
 sive and difficult to remove. It also forms a gummy coating on 
 the iron, worse than that with sulphuric, and in the subsequent 
 alkaline treatment it must be removed by caustic soda instead 
 of lime, or sometimes by a solution of sulphate of zinc. 
 
 After the iron has been freed from sulphuric acid in the man- 
 ner just described, it is put in a bath of lime-water or milk of 
 lime, boiling hot (it is very important that it should be hot), and 
 left there long enough to reach the temperature of the liquid. 
 It is then removed to an oven and dried, after which the lime is 
 
204 TECHNOLOGY OF PAINT AND VARNISH. 
 
 brushed off. If desired, the lime may be removed by washing before 
 putting in the oven. In this case it will be found that the surface, 
 which is perfectly clean and bright, rusts very easily and quickly, 
 whereas if the lime is removed by drying and brushing, the sur- 
 face is much less likely to rust, although even then it rusts easily 
 and should be painted immediately. 
 
 For most of the foregoing information relating to pickling I 
 am indebted to Mr. E. G. Spilsbury, who has had extensive 
 experience in this work -both in Europe and the United States, 
 and has applied the process to structural steel (bridge) work, as 
 well as to wire and wire rods. 
 
 Some of the largest work recently done has been treated as 
 follows : The steel as it came from the mill was put in hot 10 per 
 cent, caustic soda solution until all the grease and oil came off; 
 with this came all the dirt, with which the shop grease had become 
 mixed, and an appreciable amount of scale, making altogether 
 a bulky sludge. Next the steel was washed with boiling water; 
 then it was put in hot 10 per cent, sulphuric acid until the metal 
 surface was everywhere exposed; after which it was dipped in 
 boiling water, then in hot 10 per cent, solution of carbonate of 
 soda, then well washed in hot water, and finally dried in an oven. 
 The results were all that could be desired. 
 
 Much detailed information concerning the use of the sand 
 blast in cleaning structural steel may be found in the paper on 
 the subject by Mr. George W. Lilly, in the Transactions of the 
 American Society of Civil Engineers in 1903 and in the ensuing 
 discussion. 
 
 Treatment at the Mill. Many engineers believe that the 
 time to begin the protection of steel is at the rolling-mill, before 
 the metal is cold. It is said that careful methods of rolling will 
 prevent the formation of thick scale and that most of the scale may 
 be removed as the metal comes from the rolls, immediately after 
 which the hot surface (at a black heat) is to be sprayed with oil 
 or varnish or paint and the heat remaining in the metal will be 
 enough to bake this before the metal becomes entirely cold, thus 
 producing a coated and protected surface, which insures freedom 
 
PROTECTION OF METALS AGAINST CORROSION. 205 
 
 from rust for a period of at least some weeks, during which the 
 metal may be built up into riveted members and made ready for 
 painting. The details of this plan have not at present been worked 
 out in practice, but there is no doubt in my mind that it is a very 
 desirable thing and I believe it to be practicable. Putting bars of 
 various sections through straightening rolls has been proposed 
 as a means of removing the scale. It will remove thick scale and 
 will loosen all but the most closely adherent thin scale. This may 
 be seen where sheets of steel are rolled in a boiler-shop or in mak- 
 ing large pipe. Coatings have been very successfully applied to 
 such surfaces. 
 
 Shop-painting. In bridge work and the like, if it is decided 
 to clean by pickling or sand-blasting, it is a question as to when 
 this should be done. If it is done when the metal comes from 
 the mill (supposing that it has not been coated hot in the way 
 just mentioned) it will be necessary to do something to it at once 
 to prevent its rusting; for pickled or sand-blasted iron will begin to 
 rust almost immediately and the iron has to be at least a week 
 in the shop before it can be painted after assembling. What 
 can be done to it ? Probably a coat of linseed-oil will be applied. 
 Paint will be objected to by the shopmen and the inspectors will 
 demand a transparent coating. Boiled oil is commonly used for 
 any such purpose because it dries rapidly, but it is less durable 
 than raw oil, and it is the common opinion of the manufac- 
 turers of mixed paints, whose opinions in this matter are en- 
 titled to great weight, that boiled oil is less durable than raw 
 oil to which enough drier has been added to make its drying 
 qualities equal to boiled oil. The drier should probably be one 
 made at low temperatures. The cleaned surface may then 
 receive a coat of such oil and allowed a day or two to dry. But 
 it must be observed that oil does not dry to a hard film, but is 
 soft and rather sticky, and probably a very elastic varnish would 
 be better because cleaner; less likely to be contaminated with 
 dirt and machine-oil in the shop. Probably the increased cost 
 will be a barrier to its use. It might, and I think should, be very 
 thin, as it would then be harder, and it is not depended on for 
 
206 TECHNOLOGY OF PAINT AND VARNISH. 
 
 permanent protection, but it should be of good quality as the 
 foundation for all subsequent painting. 
 
 A much better plan is to defer the pickling or sand-blasting 
 until the structural steel has been long enough in the shop to 
 have been cut to required dimensions and all the holes punched 
 or bored and otherwise made ready for assembling. Then 
 let it be removed from the shop to the building where the sand- 
 blasting is done (for it should be under shelter), cleaned, and 
 painted. It is practicable to have it painted at this stage unless, 
 for purpose of inspection, it is thought better to have it oiled, 
 or, better, varnished. When the painting or varnishing has been 
 done and two or three days for the coating to begin to dry have 
 elapsed, it may be carried back to the shops and riveted up into 
 members, care being taken to again paint, and thoroughly, all 
 surfaces which will hereafter be inaccessible, for rusting in riveted 
 joints not only weakens but impairs the rigidity of the structure. 
 It is only fair to say that I have been told by engineers of bridges 
 who have had much experience in taking down riveted work 
 that it is uncommon for riveted joints to be dangerously rusted 
 and that the webs, rods, and other extended parts rust off before 
 the joints give way. This is partly because there is more metal 
 at the joints than elsewhere and probably partly because care is 
 usually taken to paint these surfaces heavily, and the paint is 
 mechanically protected by the location from external injury. 
 
 Shop-marks. Where it is undesirable to paint portions of 
 the surface on account of shop-marks, care should be taken that 
 these marks are as compact and small as is reasonable and to see 
 that they receive an extra coat in the final painting. Planed 
 and turned surfaces are at this time coated with a non-drying 
 grease, commonly a mixture of white lead and tallow, or a min- 
 eral grease similar to vaseline, which many' prefer. 
 
 Crevices. There are also found many crevices which will 
 be inaccessible after erection, and it is customary to fill these 
 with a fresh mixture of neat Portland cement and water. It is 
 possible to use other cementing substances, but nothing is so easily 
 used as the above, and it is good enough. 
 
PROTECTION OF METALS AGAINST CORROSION. 207 
 
 Shipping. The work is now ready for shipment. In ship- 
 ping, care should be taken to avoid scraping off the paint and to 
 avoid nesting the pieces except with packing material between 
 them; and, as has been already said, the pieces should not be 
 laid on the ground, but on skids or trestles. The paint should 
 be reasonably dry before the shipment is begun, not thoroughly 
 dry, but it should have its initial set and dry enough to be safely 
 handled, usually in two or three days after the paint has been 
 applied, sometimes one day in hot weather. 
 
 Striping Coat. The materials may now be supposed ready 
 for erection, after which the work should be carefully inspected, 
 and if there are any rusty spots these should be thoroughly cleaned 
 and painted, and any places where the paint has been rubbed 
 off should be repainted, and at this time all exposed edges and 
 angles should receive an extra striping coat of the protective 
 coating, covering the edge and the adjacent surface one or two 
 inches from the edge on each side, and all nuts, bolt-heads, 
 and rivet -heads should receive an extra coat. This may be 
 called the striping coat and is necessary for the following 
 reasons : 
 
 When paint begins to dry there is at first a sort of skin formed 
 on the surface, which contracts, and on rounded surfaces like 
 rivet- heads and on angles and edges seems to press away the 
 liquid paint beneath, so that on such surfaces there is less than 
 the normal amount. The same tendency to contract also exists 
 on flat surfaces, but in this case it is a balanced tension and pro- 
 duces no effect. There is besides the action of the painter's 
 brush, which presses harder on such places and draws off the 
 paint; but that this is not the main cause is shown by the fact 
 that pipe sections and other things which have been coated by 
 dipping exhibit the same appearance. In making paint tests, 
 it is necessary to leave out of account a strip about an inch wide 
 along the edges of the plate unless that portion has received 
 an extra coat, and the fact is well known to inspectors that such 
 surfaces are always thinly coated. The extra striping coat is 
 therefore necessary if we are to have two full coats or their 
 
208 TECHNOLOGY OF PAINT AND VARNISH. 
 
 equivalent over the whole surface, and it is the more impor- 
 tant because these portions are more exposed than the flat sur- 
 faces. 
 
 When this striping coat has become dry (two weeks or longer if 
 possible after its application), another full coat of the protective 
 coating should be applied to the whole surface. Of course, if a 
 coat of oil or thin varnish has been applied in the shop instead of 
 the regular protective coating, another full coat of the latter will 
 be necessary after erection, and the striping coat may intervene 
 between these two full coats. If, during erection, any small 
 cavities are produced they should be filled as already described, 
 and any large ones should be drained by making suitable open- 
 ings. Care should be taken that no undrained places are left 
 which may fill with rain or ice ; the latter by its mechanical action 
 is likely to tear off the best paint. 
 
 If the preceding directions have been followed, the structure 
 has two full coats of a protective coating and is ready for decora- 
 tive painting, if any is desired. If not, it should have a third 
 coat of the protective coating. Two or three or even six months 
 may, however, be allowed to elapse before this final painting is 
 done. The structure may now be regarded as finished and turned 
 over to the maintenance department, who should watch it care- 
 fully and repaint it before it begins to rust, or, at least (perhaps 
 better), touch up any doubtful places and so avoid any general 
 repainting. I believe that a structure treated in this way would 
 be easily maintained in practically perfect condition at a cost so 
 low as to be unimportant. It should not be forgotten in con- 
 nection with this whole subject that paint should not be applied 
 in freezing, rainy, or misty weather, or to surfaces which are not 
 dry and clean, but this is true of all painting. It is sometimes 
 necessary to apply paint in cool weather. It is then allowable 
 to heat the paint to a temperature of 150 F., which will be 
 found much better than thinning it. 
 
 It is folly to expect any general agreement as to what is 
 the composition of the best coating for structural metal. Those 
 which are practically in use are: 
 
PROTECTION OF METALS AGAINST CORROSION. 209 
 
 1. A variety of mixtures, of which coal-tar dissolved in ben- 
 zole or dead-oil may be taken as the type. 
 
 2. Paints made with linseed-oil or an alleged substitute, 
 and pigment ; containing some drier and usually some varnish. 
 
 3. Varnishes. 
 
 4. Varnish and pigment paints (the so-called varnish enamels). 
 Other materials are used on water-pipes, but these will receive 
 separate discussion. 
 
 Coatings of the first class need very little discussion. They 
 are used because they are cheap. I have heard of a mixture 
 of asphalt and mineral oil which cost, exclusive of packages, only 
 seven cents per gallon, which was used on some railway bridges; 
 the labor of applying it, and the constant repainting which was 
 required, made the final cost of maintenance so great that the 
 authorities changed to the use of a paint costing a dollar and 
 a half a gallon. Most of the so-called asphaltum varnishes 
 used on metal-work come under this heading. They contain 
 frequently nothing more expensive than coal-tar or petroleum 
 residues, and are thinned frequently with kerosene. Rarely 
 these mixtures are made with asphaltum and softened with palm- 
 oil stearine, or something of that sort, and thinned with benzine; 
 such a mixture may be very good for temporary use, being 
 impervious as long as its elasticity remains, and, unlike much coal- 
 tar, being free from acid which will attack the iron. Some of 
 the cheap coal-tar mixtures are actively corrosive; some are 
 mixed with pulverized lime to remove the acidity. It is by no 
 means unusual for a contractor, especially on public work or 
 on work where the inspection is not good, to contract for the use 
 of a good paint, and use instead some of these excessively cheap 
 and worthless mixtures. I would not include adulterated paints 
 under this heading, but among those paints which they imitate; 
 and I do not say that some of these mixtures or compounds are 
 not good enough for temporary use; and not a little steel is 
 v.sed in this way. But in general, it may be fairly said that these 
 mixtures are not as economical as better paints, and hence are 
 not suited for general use. 
 
210 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Oil Paints. In the second class, that of oil paints, among 
 which, as a matter of convenience, I will include red lead and 
 oil although this is considerably different from ordinary paints, 
 are found the most commercially important of the preservative 
 coatings. It will appear before this essay is finished that the 
 author believes in the use of varnish paints as the best, but it 
 must be observed that linseed-oil is the elastic base of varnish, 
 and as the varnish-resins are more costly than oil, and as 
 any labor expended in making varnish increases the cost of the 
 materials contained in it, so it is that a straight linseed-oil paint 
 may be made at a lower price than a varnish paint and is the best 
 paint that can be hard at the price. When we are able to say that 
 such a paint is really a good paint and that it is the best to be 
 had at the price, we have given reasons for its use which no 
 possible arguments can overthrow, though they may modify their 
 application. 
 
 An oil paint is composed of a pigment mixed with a liquid or 
 vehicle, which consists usually of raw linseed-oil to which has been 
 added 5 to 10 per cent, by volume of liquid drier, this latter con- 
 taining usually both lead and manganese, and either turpentine or 
 benzine as the volatile part. This mixture of oil and drier is not 
 very likely to change if kept from the air and is chemically unaf- 
 fected by most pigments; hence an oil paint has excellent keeping 
 qualities. Of course the pigment will in time settle to the bottom, 
 but commonly it can be stirred up again; however, a paint should 
 always be used up before it is injured in this way. Containing 
 little volatile matter it does not evaporate, and the oil works 
 freely under the brush, more so than the best varnish, so that 
 an oil paint is the easiest to apply of all paints. This in itself is a 
 great advantage, for it is easier both physically and mentally to 
 put on a good-looking coat of oil paint than of any other. This 
 quality of working freely and sweetly under the brush is the best, 
 thing about an oil paint, and this alone is the reason why these 
 have displaced the varnish paints in the work of modern artists, 
 while probably all the so-called oil paintings of the great painters 
 of the middle ages were done in pleo-resinous varnish. Oil is, 
 
PROTECTION OF METALS AGAINST CORROSION. 211 
 
 when spread in a thin film, very slow to set, and when it finally 
 begins to set it goes on rapidly until the paint is hard enough to 
 handle; the thorough hardening takes a long time, perhaps a 
 year. This slowness of setting facilitates working with a brush, 
 and, especially on wood, gives it time to penetrate the pores of 
 the surface to which it is applied. A coat of oil is, therefore,, 
 often used on wood as a priming coat even where varnish is sub- 
 sequently to be used. On account of its remarkable fluidity 
 linseed-oil may be mixed with a large proportion of pigment, and 
 if this pigment is very cheap it may actually reduce the cost, and 
 if it is dear the oil-paint still usually has advantages in price 
 because of the lower price of oil than of varnish^ and, as it carries 
 more pigment, its covering power, or opacity, is greater. Any- 
 thing which enables two coats to take the place of three is a great 
 advantage, for the cost of labor is an important item, sometimes 
 being much more than that of the paint. Oil is usually, when 
 fresh, more nearly colorless than varnish, and on that account 
 displays well the color of the pigment. This advantage, however,, 
 disappears very shortly, for oil paints quickly become dull and 
 show the effect of the weather more than varnish paints. 
 
 The possible supply of linseed-oil is unlimited. Flax will grow 
 anywhere that any cereals will, and when the seed is high in value 
 the acreage quickly increases, so the oil is subject to large and 
 rapid fluctuations in price. When it is high, there is a strong 
 temptation to adulterate it or to substitute something for it. 
 
 Oil Substitutes and Adulterants. The most common adul- 
 teration is with mineral oil, but substitutes are from time to time 
 proposed, the most important probably being fish-oil. This is. 
 normally a non-drying oil, but it may be cooked with^lead and 
 manganese and made into a slowly drying oil. It has, partly by 
 blowing air through it and partly by treating it with sulphur at 
 a moderately high temperature (vulcanizing) , been converted into 
 an elastic solid substance which is soluble in kerosene of low 
 boiling-point and thus has been made an oil which dries, like a 
 spirit varnish, by evaporation of the solvent. The first of these 
 oils, the fish-oil " boiled" with driers, is said by some very good. 
 
212 TECHNOLOGY OF PAINT AND VARNISH. 
 
 authorities to be a good addition to the extent at least of 20 
 per cent, to linseed-oil for making roof paints, its slower drying 
 not being noticeable in this case, and an advantage of greater 
 elasticity is claimed. This may be so. I have no experience in the 
 matter, but I think this is believed by some very honest and very 
 well-informed makers. As to the other preparation, it is well 
 thought of by some users, but in the cases which I have had 
 opportunity to examine it has not been equal to linseed-oil. 
 Most of the so-called substitutes are various mixtures of mineral 
 oil, fish-oil, rosin, rosin-oil, and rosin varnish. They are mainly 
 sold to be used surreptitiously as adulterations or substitutes 
 for linseed-oil, but from time to time are put out boldly with a 
 flourish of trumpets as a new and improved variety of paint oil, 
 are sold for a time to the unwary, and then are forgotten. There 
 is no oil worthy to be compared with linseed-oil for paint. 
 
 As has been stated in the chapter on driers, the objection to 
 these preparations is the danger that they may continue to act 
 after the film has become properly oxidized. But a paint which 
 dries slowly makes a rather soft film and is without lustre, so it 
 is common to add to it a quantity of varnish, which hardens the 
 film and makes it smooth and shining. If this varnish is made of 
 good materials it improves the paint in every way except working 
 quality and covering power and, in the amount generally used, 
 does not sensibly injure it in these respects. Such a varnish 
 ought not, however, to be made of rosin, but of some of the true 
 varnish-resins, and it will, in the nature of things, add to the cost 
 of the paint. A cheap rosin varnish is often, I fear I might say com- 
 monly, used for this purpose, and is bought by the paint-maker 
 at less than the price of oil, sometimes at half the price of oil. 
 The worse it is the greater is the temptation to use it to excess; 
 in fact, any varnish of this sort is an excess. 
 
 Lead Paints. As a rule there is no chemical action between 
 oil and pigments, but to this there are exceptions. Action un- 
 doubtedly occurs between oil and white lead, probably between 
 the oil and the lead hydrate, which constitutes at least a quarter 
 of the pigment. This takes place slowly, and painters prefer 
 
PROTECTION OF METALS AGAINST CORROSION. 213 
 
 white- lead paint which has been ground for a long time and believe 
 that it is more durable. This change is said to be due to resini- 
 fication of the oil, converting it into a sort of varnish; chemically 
 it would seem that it should be a saponification resulting in a lead 
 soap, which would dissolve in the unchanged oil. I am not aware 
 that any careful chemical study has been made of the subject. 
 Zinc oxide (white zinc) also acts on oil, but in a much less degree, 
 and a mixture of white lead and white zinc, usually in the propor- 
 tion of two of the former to one of the latter, is thought to be 
 better than either alone. Zinc works more freely under the 
 brush, but its covering power is less. 
 
 Red Lead. When we pass on to red lead, which is an oxide, 
 we find that the pigment and the oil readily unite; in red-lead 
 paint the oxide is present in excess, hence all the oil becomes 
 combined. If red lead and oil are mixed and sealed up in an 
 air-tight can, it will be found after a time that the mixture has 
 solidified, showing that the oxygen of the air, which is the har- 
 dening agent in ordinary paints, is not necessary. The oil is not 
 turned to linoxyn but is completely saponified to make a lead soap, 
 and the dry paint is composed of unchanged red lead cemented 
 together by this compound. As to the durability of the latter, 
 there is much difference of opinion. It is singular that every one 
 is agreed that this lead soap, or linoleate of lead, added to oil 
 paint, is an injury to it, the bad results increasing with the amount, 
 yet it cannot be denied that when this is used without any free oil 
 it makes a cementing material or binder of great permanence, less 
 durable perhaps than oil alone, but worthy to be compared with 
 it, and many think it superior to oil. It is natural to expect it to 
 crumble and fall off, and sometimes it does, but as a rule it does 
 not, but adheres to the iron with great tenacity. Not much is 
 known about the causes which promote or lessen the permanence 
 of red-lead paint. The subject needs long and expensive study. 
 We know that commercial red lead is of variable chemical com- 
 position, not because of adulteration, but from its method of 
 manufacture. It is a mixture of the peroxide and protoxide of 
 lead; the former is commonly thought to be the most important 
 
214 TECHNOLOGY OF PAINT AND VARNISH, 
 
 and characteristic ingredient, but the latter is present to an extent 
 which varies from 5 to 50 per cent. It is only reasonable to 
 expect different results from different mixtures of this sort, and 
 no one seems to know what are the best proportions. It is said 
 that by a second roasting of the dry red lead a considerable part 
 of the litharge in it may be changed into the peroxide. I believe 
 such treatment is given red lead for making storage batteries- 
 Such red lead has been used for paint, and the results are said 
 to be encouraging. It has long been known that the protoxide 
 (litharge) and glycerin will chemically combine when mixed 
 together and form a cement of great value used for cementing 
 the glass plates of aquaria and the like. We know that when oil 
 and lead oxide combine the glycerin of the oil is set free. This 
 does not combine with the peroxide, but in the presence of litharge 
 it probably unites with it, and this litharge- glycerin cement may 
 play an important part in the action of the lead soap with which 
 it is mixed. Again, it may be that the oil unites with the litharge 
 and not with the peroxide, and that when the proportion of the 
 former is low, part of the oil dries in the ordinary way by air- 
 oxidation. There is nothing against this supposition in the be- 
 havior of the paint. And yet again it may be that the oil com- 
 bines with the litharge and that a large proportion of the latter is 
 necessary to get the best results. As a matter of fact, we know 
 nothing accurately about it. I have been told by a manufac- 
 turer of red lead that no two sorts of furnaces will give the same 
 product, and that different men will get different products from 
 the same furnace by working at different temperatures. Enough 
 has been said to explain how there may be wide differences of 
 opinion in regard to the value of red lead as a paint for metal. 
 On one point there is a substantial agreement: that the amount 
 of dry red lead in a gallon of paint should be as large as practica- 
 ble, from 18 to 30 Ibs. to a gallon of finished paint; probably 
 most engineers recommend twenty-four or thereabouts. On an- 
 other point there is agreement of opinion that red lead is the 
 most difficult of all paints to apply, and this again may be an 
 important cause of failure. The working qualities of the paint 
 

 PROTECTION OF METALS AGAINST CORROSION. 215 
 
 are improved by the addition of lampblack, which probably adds 
 to its durability also. Because this paint will harden in closed 
 packages it is impracticable to prepare it in advance of use; it 
 should not be made up more than twenty-four hours ahead of 
 time, and it is better if mixed on the spot and immediately before 
 using. Various methods have been tried to avoid this difficulty; 
 one (patented) mixture contains a considerable amount of glycerin 
 instead of all oil; one maker mixed two-thirds red lead and one- 
 third white zinc: this will keep for a week or two; others add 
 whiting (carbonate of lime). 
 
 Ready-mixed Red Lead. Red lead is also mixed with oil and 
 allowed to stand and harden; then this lead and oil compound 
 is broken up and reground with fresh oil; after this treatment it 
 sets very slowly a second time. This is analogous to breaking up 
 Portland cement after it has begjn to set. None of these prepa- 
 rations has met with any general approval. This paint is often 
 adulterated with oxide of iron, which is much cheaper. Red-lead 
 paint adheres well to iron and is used by many for a first coat, 
 having some good paint or varnish over it to protect it. Being 
 already supersaturated with oxygen it is not attacked by that 
 element; it would seem that it might supply oxygen to the iron, 
 thus rusting it, but it does not do so. It may be that the presence 
 of carbonic acid is necessary, and this is kept away by the red 
 lead, which itself combines with it. This is, in fact, a common 
 cause of the whitening of red-lead paint exposed to the weather, 
 and a cause of its destruction. Red lead is a substance which 
 enters with great energy into chemical union with acids of almost 
 all kinds, and this accounts for its common failure when used 
 where the air contains them, and its comparatively excellent 
 service in the pure air of the country, especially away from the 
 seaboard; for, as nas been already said, the air near the sea 
 contains spray of sea-water to such an extent that the natural 
 fresh waters of the country near the coast contain an appreciable 
 amount of common salt, the proportion of which decreases as the 
 distance from the sea increases, and investigations have made it 
 possible to determine and draw on the map lines of percentages 
 
216 TECHNOLOGY OF PAINT AND VARNISH. 
 
 of chlorine more or less parallel to the coast-line. This has been 
 done by the chemists of the Metropolitan Water Commission of 
 Massachusetts and elsewhere. 
 
 The action of chlorine on lead is not very rapid, but many 
 acid substances act more violently, and so far as my own rather 
 extensive observations have gone, red-lead paint is never used 
 about chemical works, smelters, etc., where better results are had 
 by the use of varnish or a varnish paint. 
 
 Unreliable Reports. Actual use on a large scale is the best 
 test of a paint, but it is very difficult to be sure of your conclu- 
 sions even from such use. The chief metal structures which 
 are accessible for observation are bridges. A competent man 
 who should have charge of the painting of a large number of 
 these ought to be able to arrive at valuable results, but men 
 capable of making critical study of so difficult a matter are rare, 
 and are usually too valuable to be put to such work. Tenure of 
 office is often brief, as compared with the long time needed for 
 such investigations, and very often the corporation which owns 
 the bridge has adopted some one paint as a standard and this 
 seems to be able to prevent a fair judgment. The men who are 
 in charge become prejudiced in favor of their paint and can see 
 no defects in it, and nothing good in anything else. The very 
 workmen share in this feeling, and they have learned how to 
 use their standard paint to the best advantage, and it is applied 
 better than any other. They, in many cases, retouch w r ork 
 from year to year, which is quite right, but no record of such 
 work is made and the bridge is reported as having stood so many 
 years without repainting, while a bridge painted with some 
 other material is condemned as soon as it begins to look shabby* 
 The result is that one man who has charge of the bridges for 
 one road reports that a certain paint is satisfactory and better 
 than any other, while the next man on a parallel road condemns 
 the first man's paint and extols a paint which the other found 
 wanting. Both mean to be right; neither is capable of knowing 
 the truth. Nothing is more natural than the desire to think 
 well of one's own work, and in practice I would commonly prefer 
 
PROCTETION OF METALS AGAINST CORROSION. 217 
 
 the real opinion, if it can be got at, of a paint manufacturer to that 
 of a user, for the former has every incentive to find out the truth; 
 the trouble with him is that he is disposed to think, and especially 
 to speak, most favorably of the thing which sells the best. There 
 isn't much money in being a missionary or a reformer. Sell 
 people what they think they want, not what you think they ought 
 to want, is the business maxim; and this feeling interferes with 
 testing paint or anything else. 
 
 Paint Tests. Paint may also be tested with sets of test-plates. 
 If such experiments are made with sufficient care they are valu- 
 able, and as matters actually stand, this is the most available 
 way of getting reliable results. But it is not an easy or simple 
 thing to get at the truth in this way. I would say in the first 
 place that the plates should not be too small. I have myself 
 used plates measuring twelve inches by twenty, and I think 
 they would be better if they were larger. They should not be 
 of thin metal, never by any chance of sheet iron, but thick enough 
 so that they will not bend or spring under any pressure which 
 is likely to be applied to them. They should be of pickled and 
 cold-rolled steel, unless a test of the behavior of paint on other 
 metal is in question, and perfectly free from scale and rust; all 
 exactly alike in these regards. I mark plates with a steel num- 
 bering stamp on the middle of each side and also mark the same 
 plates with a series of saw-nicks on one edge; these latter are 
 perfectly reliable and easy to find; the former are more easily 
 read and sufficient in most cases. The paint or varnish used 
 should be in its best condition and applied under favorable con- 
 ditions of temperature and weather and after each coat the plate 
 should be hung up to dry for at least a month. To facilitate 
 hanging up these plates a hole should be bored in each end of the 
 plate, about half an inch in diameter, and the plate should be 
 hung alternately from these holes as alternate coats are applied. 
 For the reasons already given it is necessary to apply a striping 
 coat along the margins of the plates between the first and second 
 coats, and if three coats are applied it would be well to apply a 
 second striping coat between the second and third or else after 
 
218 TECHNOLOGY OF PAINT AND VARNISH. 
 
 the third; this I have not myself practised, usually making two 
 coat tests; the striping coat requires thorough diying. Unless 
 the test is simply a weathering test, the plates should be hung 
 up in a room where the air is ordinarily pure and dry for six 
 months after the painting is completed before the test begins; 
 but if they are to be used in a weathering test, they may be ex- 
 posed as soon as they are reasonably dry and it is certain that 
 all are in about the same condition. It is very desirable that 
 the thickness of each plate should be measured with a vernier 
 caliper before painting at certain designated spots; for example, 
 the caliper may be applied at a point il inches back from the edge 
 and 4 inches to the right of each corner. Record is made of these 
 measurements, and when the last coat of paint is dry the thick- 
 ness may be again measured; if the plate is painted on both 
 .sides, which I think is the better way, the difference in measure- 
 ment, divided by two, gives the thickness of the paint- or 
 varnish-film. 
 
 Electrical Tests. If the caliper can be depended on to read 
 the ten-thousandths of an inch this measurement will be impor- 
 tant, especially if the porosity of the coating is to be determined 
 by its electrical insulating power. If this test is made it must 
 be remembered that the ease of insulation varies with the square 
 of the thickness of the coating, and that only the direct current 
 Is to be used, because with the alternating current there is danger 
 that the plate will act as a condenser and conceal the real voltage. 
 Such electrical tests if made at different periods during the time 
 test will be of much interest; so far as I know this has never 
 been done. Coatings for special uses should, of course, be 
 tested after being applied in the way which is best suited to de- 
 velop their possibilities; if, for example, we are to test a baked 
 coating against an ordinary paint or varnish, we should bake it 
 under favorable conditions, but we would not therefore bake 
 the competing preparations, which should be applied in the 
 usual manner. 
 
 Protect Edges. In any method of exposing plates which I 
 liave ever seen, it is impossible to avoid injury to the edges of 
 
PROTECTION OF METALS AGAINST CORROSION. 219 
 
 the plates, and as the marginal portion of a plate of ordinary 
 size is a large proportion of its total surface, we should either 
 start out by saying that we will not count as part of the test the 
 strip, say an inch or an inch and a half wide, along the edge of 
 any plate, or we should take some extraordinary measures to 
 prevent such injury. This is especially important with plates 
 immersed in the water, which are often injured more by floating 
 objects carried by tides and currents, perhaps far below the 
 surface (ice, for example), which because of their weight and 
 rigidity strike severe blows and thus mechanically remove the 
 coating, no matter how firm it may be. I have thought that 
 it might be a good plan to set each plate in a wooden frame, 
 like those on the slates of school children; these would give 
 considerable protection. I have not known this to be done, 
 but I see no objection to it. This danger of marginal injury 
 is one of the most serious objections to plate tests. 
 
 A most serious matter is the difficulty of knowing that the 
 plates are all alike. When a coating for any reason begins to 
 fail, and even when perfectly new, if it is, like almost all coatings, 
 a little porous, it is obvious that if we have two plates coated 
 exactly alike, and the metal of one is more easily corroded than 
 the metal of the other, the coating on the former plate will appear 
 to perish sooner than on the latter. Chemical tests will, of course, 
 show differences of composition if there are any, but I do not 
 think it very difficult to get plates of the same chemical compo- 
 sition, but the physical or molecular structure has great influence, 
 and I do not know how to determine this condition. That its 
 effect is real is shown by the following facts : Copper pipe is used 
 on the ships of our navy for fire mains and other purposes; this 
 is made in sections with flanged ends. The flange is made by 
 slipping over the end of the pipe a tightly fitting brass ring, and 
 the projecting end of the copper pipe is expanded by hammering, 
 so that the ring cannot come off. This hammering, of course, 
 draws out the copper and disturbs its structure without affecting 
 its chemical composition; as the pipe is composed of copper, as 
 nearly chemically pure as can be commercially obtained, there 
 
220 TECHNOLOGY OF PAINT AND VARNISH. 
 
 may be said to be no chemical difference in its different parts. 
 These sections of pipe were coated with a varnish enamel all 
 alike. 
 
 Influence of Molecular Structure. After prolonged use it was 
 found that the coating was in good condition except near the 
 flanges, where the metal, though it had not been actually ham- 
 mered, had been drawn by the blows on the adjacent ends. This 
 occurred not in one but uniformly in very many instances, so that 
 the inference that the liability of corrosion of the copper is de- 
 pendent on its molecular structure was unavoidable. If this is 
 true of copper, it is probably true of steel and iron ; and the effect, 
 instead of being inconsiderable, is very marked. It is easy to 
 see that differences in temperature while rolling steel plate or 
 bars may make difference in structure, as do also differences of 
 thicknesses or section. This is, in fact, well known, for a steel 
 wire is three times as strong as the same metal rolled into a bar. 
 It is then possible that two test-plates which look alike may vary 
 by an important amount in resistance to corrosion, and this at 
 once introduces uncertainty into the most carefully conducted test. 
 This is, in fact, a valid objection, so far as it goes, to ail test-plate 
 experiments; yet the practical difficulties of getting fair experi- 
 ments made on a large scale are probably vastly greater. 
 
 The foregoing discussion of the way to conduct tests is pre- 
 liminary to the following account of some tests made by the author, 
 which will be followed by some remarks on varnishes and var- 
 nish paints, as used for the protection of structural metal. The 
 substance of these experiments has already been published in the 
 Transactions of the American Society of Civil Engineers, but it 
 is worth while to bring together the whole in a somewhat more 
 connected form. 
 
 In 1895 I had eighty- four plates prepared for a test in sea- 
 water. Permission was ob tamed from the U. S. Navy Depart- 
 ment to make use of the facilities of the New York Navy Yard, 
 and I was especially fortunate in having the cordial assistance and 
 co-operation of Naval Constructor F. T. Bowles (afterward Chief 
 Constructor and Rear Admiral), in carrying out the work after 
 
PROTECTION OF METALS AQAINST CORROSION. 221 
 
 the plates had been made ready. The plates were coated at the 
 works of Edward Smith & Co., who, moreover, paid the ex- 
 penses of this and the following series of tests, the most extensive 
 and I believe the most important that have been made up to the 
 present time. Thirty of these plates were of aluminum, and 
 were furnished without cost by the Pittsburgh Reduction Com- 
 pany, makers of aluminum. Prior to this time aluminum had 
 been used in marine work and had been condemned, as the sea- 
 water attacked and dissolved it, but pure aluminum had not been 
 used, and it was desirable to know whether the pure metal or 
 some alloy of known composition might not be available, and 
 also, of course, what coating was best for its protection. Five 
 series of aluminum plates and alloys were provided, ranging from 
 75 per cent, aluminum to 994 per cent., which was at the time the 
 purest aluminum which could be commercially prepared. There 
 were six plates in each series and a corresponding number of 
 varnish coatings were applied, so that each of these coating com- 
 pounds was applied to one of each of the different kinds of alu- 
 minum plates. In this way the different alloys could be com- 
 pared and so could the different coatings. The same coatings 
 were applied to some of the steel plates, but the greater number 
 of the latter, and the fact that they were all of one metal, made it 
 possible to use a much greater number of coatings. The gen- 
 eral plan, which was carried out more fully in the later set of 
 tests, was to determine the comparative value of pure linseed-oil 
 as a vehicle, then of a varnish containing a maximum proportion 
 of oil to the unit amount of resin, then a medium varnish, then 
 one having a minimum proportion of oil; and as different resins 
 may have varying values, to duplicate and in fact to triplicate those 
 varnish experiments with varnishes made of resins of three dif- 
 ferent classes. The resins selected were Zanzibar, Kauri, and 
 Manila. The latter is said to be a "recent" resin, that is, one 
 taken from the living tree ; Kauri is a semi-fossil resin, from trees 
 of a species now living, but of no use except as it has lain buried 
 in the ground for a long time and undergone chemical change ,- 
 while Zanzibar is a fossil so old that the trees themselves have 
 
222 TECHNOLOGY OF PAINT AND VARNISH. 
 
 become extinct. The three resins are well known and are com- 
 monly regarded as types of the classes to which they belong. 
 Besides these there were a few special paints or compounds tried, 
 red lead and oil being one, and another the baked enamel known 
 as the "Sabin Coating," which will be more particularly men- 
 tioned in describing the coating of pipes; also a special oleo- 
 resinous varnish known by the trade name of Durable Metal Coat- 
 ing, in which a certain amount of gilsonite replaces a correspond- 
 ing amount of vegetable resin. It is interesting to note that a 
 varnish of very similar composition to this was used in the first 
 really scientific sea-water tests of which I can find any record, 
 t)y Mr. Robert Mallet, who made reports to the British Asso- 
 ciation for the Advancement of Science in 1838, 1842, and 1843; 
 and such a varnish, with one other made entirely from fossil 
 resins and containing a large amount of oil, were the best of all 
 the different paints and coatings which he tried. His exposures 
 were for a period of eighteen months and are worthy of study by 
 any one interested in the subject. He was handicapped by lack 
 of knowledge of the art of making varnish and paint, and of their 
 practical use, but he approached the subject with a truly scien- 
 tific spirit, and without unreasonable prejudice or interest. The 
 aluminum plates were put in a cage or framework by themselves; 
 the steel plates in two similar cages. Each cage or frame con- 
 sisted of four corner-posts each about 3 ins. square and 4 or 5 ft. 
 long; these were mortised into 2-in. plank ends which were about 
 2^ ft. square, and the tenons were held in place by wooden pins. 
 Each of these corner-posts had grooves about f in. deep and wide 
 enough to receive the edge of a plate cut across one side every 
 2 ins., and these posts were so set that the plates could be slipped 
 into these grooves like shelves, a couple of inches apart. In this 
 way thirty plates would fill a frame 60 ins. long. After the plates 
 were all in place they were prevented from sliding out by fixing 
 a bar across each end of the set of plates parallel with the corner- 
 posts, and the plates were moreover made tight in the grooves by 
 little wooden wedges at each corner of each plate. It was not 
 desirable to use any metal about the frames, for iron would rust 
 
PROTECTION OF METALS AGAINST CORROSION. 22$ 
 
 out and there was danger that the vicinity of any other metal 
 might induce galvanic action. These frames, when filled, were 
 heavy and rather awkward to handle. They were suspended by 
 substantial iron chains which went entirely around each cage 
 lengthwise. The iron rods from which the links of these chains 
 were made were f in. in diameter, and so severe was the corrosion 
 that in some cases these chains, of which two were attached to each 
 cage, were entirely rusted away, although the chains were " gal- 
 vanized" or zinc-coated; and in consequence some of the plates 
 were lost. In the first test fourteen steel plates were lost, as is 
 shown by the table. This first set of plates was put in the water 
 in January, 1896, and was taken out July 29, 1896, after six 
 months' immersion. During this time they were suspended 5, 
 or 6 feet below the level of the water, in the New York Navy 
 Yard, in Brooklyn. The water here is foul because of the dis- 
 charge of sewerage from the city, and the conditions are more un- 
 favorable than they would be in the water of the open sea. The 
 strong tide constantly stirs up the mud from the bottom. When 
 the plates were finally removed for examination it was done in 
 the presence of the Naval Constructor and of several well-known 
 engineers and of representatives of the technical press. The 
 reports in the following tables are substantially those made by 
 the combined inspection of these authorities. It has been said 
 that the ends of the frames in which the plates were suspended 
 were of solid wood. After soaking in the water these ends 
 swelled, thus separating the corner-posts more than they were at 
 first, and in consequence the plates became loose. This caused 
 considerable damage to the coatings at the corners where they 
 were in the grooves, and the edges of the plates also suffered from 
 abrasion by objects floating in the water. This, as has been 
 already explained, is a serious cause of error, or at least made it 
 difficult to arrive at just conclusions. Four-fifths of all the cor- 
 rosion occurred along this marginal strip. 
 
 Among the pigments mentioned is one called by a trade name 
 "Flamingo Red." This was included, although its composition 
 was unknown, but consists in considerable part of a red coloring- 
 
224 TECHNOLOGY OF PAINT AND VARNISH. 
 
 matter derived from coal-tar, and it had seemed very permanent 
 in the air. It did not prove to be of much value in these tests. It 
 will be noted that some of the aluminum plates are said to have 
 "one side baked" and that the steel plates are mostly made up 
 in pairs in this first test. Of each of these pairs one plate was 
 baked at a temperature of 215 to 240 F. for four hours or 
 longer. The steel plates bearing the odd numbers were dried 
 .slowly at the ordinary temperature and the ones with the even 
 numbers were baked. This was done because it was thought 
 possible that baking might add to the durability of the coatings, 
 but the result showed that while a special coating made to be 
 baked on was durable, the baking of coatings not designed to 
 stand a high temperature was on the whole injurious to them, 
 more so to those which were naturally hard and brittle than to 
 those which were more elastic. One very remarkable thing was 
 observed, in this and the following tests, which can hardly be 
 made to appear properly in a tabulated report or indeed in any 
 kind of a report, which is that all these paints and varnishes 
 (except the "Sabin Coating," which was baked on at 400 
 F., and thus stands apart from the others) soften when soaked 
 for a very long time in water. They do not seem to dissolve, and 
 in many cases the water does not penetrate to the underlying 
 metal, but the coating becomes soft, and though it remains elastic 
 it can be scraped off in large strips. If, however, it is not dis- 
 turbed and the plate is set up in the air it will dry out and the 
 Tarnish will become hard again and even lustrous. When it is 
 soft it can be scraped off with the greatest ease, and this prevents 
 its being useful for submarine work. Some of the varnish enam- 
 els were much less affected in this way than the varnishes them- 
 selves, but none were very resistant. It is obvious, however, 
 that these same coatings might give satisfaction in places where 
 they would be dry part of the time. 
 
 In the following table the letter "K" stands for Kauri (resin), 
 "Z" for Zanzibar, and "M" for Manila, and the numerals pre- 
 fixed to these letters indicate the number of gallons of linseed-oil 
 which are combined with the unit amount, 100 Ibs., of resin 
 
PROTECTION OF METALS AGAINST CORROSION. 225 
 
 SERIES I. 
 
 Ninety-nine and One-half 
 Per Cent. Pure A1 n i " i "" 11 * 
 
 SERIES II. 
 
 Ninety-eight Per Cent. 
 
 Aluminum and Two Per 
 
 Cent. Copper. 
 
 S& Din Process 
 
 PCTlGCt* 
 
 Perfect. 
 
 107. 
 
 'Durable Metal Coating," 
 MM s:i- bated. 
 
 102. 
 
 ie.perfect. 
 Unbaked side, three blisters, 
 i in. diameter. No gen- 
 eral corrosion or roughen- 
 ing. The surface of the 
 paint had lost its gloss. 
 Coating good on edges of 
 
 108. 
 Baked side, one blister, I in. 
 
 Unbaked side, perfect. 
 
 Ultramarine Blue, one side, 
 
 "Flamingo Red," one side, in 
 
 20 K. varnish, not baked. 
 
 Blue. 103. 
 
 Scarcely any corrosion, but 
 shows roughening of coat- 
 pin- 
 
 Red. 
 
 General condition good ex- 
 cept near edges of plate; 
 there, busters on surface i 
 in. wide along one-fifth the 
 margin. Very little corro- 
 sion. 
 
 109. 
 
 Blue and red about the same 
 as 103, except that about 
 twice as much surface was 
 blistered. General condi- 
 tion good. 
 
 'White zinc in 20 K. varnish, 
 one side baked. 
 
 104. 
 
 Baked side, about 2 sq. ins. 
 in one place half covered 
 with small blisters. No 
 
 Unbaked side, first-rate con- 
 dition. 
 
 Baked side badly blistered in 
 spots along the edges, a- 
 mounting to about 6 per 
 cent, of the total surface of 
 the plate. Some corrosion 
 under these. 
 
 Unbaked side all right except 
 that i per cent, of the sur- 
 face showed pin-head blis- 
 ters on a strip about } in. 
 wide on one edge of plate. 
 
 oxide, in 20 K 
 varnish, one side baked. 
 
 105. 
 
 Baked side, one blister i in. 
 by $ in., otherwise first- 
 rate. No corrosion. 
 
 Unbaked side, perfect. 
 
 in. 
 
 Baked side, four central \ in. 
 blisters, numerous margi- 
 nal ones about i per cent, 
 of plate. Very httle corro- 
 
 Unbaked side, first-rate con- 
 dition. 
 
 Spar varnish, no pigment, one 
 ade baked. 
 
 Meet 
 
 106. 
 
 Baked side, two central blis- 
 ters, 2 and 4 sq. ins. and 
 nearly all the margin $ in. 
 wide. Considerable corro- 
 sion. Perfect except where 
 blistered, lustre good, etc. 
 
 Unbaked side, two central 
 blisters, } sq. in. and i sq. 
 in., slight marginal corro- 
 sion, coating evidently thin 
 on edges. 
 
226 
 
 TECHNOLOGY OF PAINT AND VARNISH. 
 
 SERIES III. 
 Ninety-eight Per Cent. Alu- 
 minum. (The quality 
 known in 1895 as com- 
 mercially pure aluminum.) 
 
 SERIES IV. 
 Ninety-three Per Cent. Alu- 
 minum, Seven Per Cent. 
 Copper. 
 
 SERIES V. 
 Seventy-five Per Cent. Alu- 
 minum, Twenty Per Cent. 
 Zinc, Three Per Cent. Cop- 
 per, One Per Cent. Iron. 
 
 113. 
 
 At one corner a break in the 
 coating let in water and 
 caused a blister of about 2 
 sq. ins. Coating rather over- 
 baked and brittle, but else- 
 where perfect. 
 
 Coating overbaked, cracked 
 at corners by the wooden 
 framework, and the sea- 
 water made blisters at the 
 corners, some of which 
 were 3 sq. ins. Remainder 
 of plate perfect. 
 
 Coating overbaked and brit- 
 tle; badly blistered along 
 the edges. All blisters un- 
 der pipe-coating enamel are 
 continuous and start from 
 the edge. The middle of 
 the plate was all right. 
 
 114. 
 Baked side perfect. 
 Unbaked side tough and ad- 
 herent, except one small 
 spot near the middle of the 
 late , which looked as if the 
 coating had been broken, 
 and where corrosion had 
 begun. 
 
 120. 
 
 Baked side showed three blis- 
 ters of about i sq. in. each, 
 and some corrosion under 
 these; otherwise all right. 
 Unbaked side perfect. 
 
 126. 
 Baked side badly blistered 
 along the edge, 6 or 8 per 
 cent, affected. 
 Unbaked side slightly blis- 
 tered along one edge : con- 
 dition otherwise good. No. 
 corrosion. 
 
 us- 
 
 Blue and red about alike. 
 No decided blisters, but 
 coating itself showed some 
 signs of decomposition, es- 
 pecially the blue, which had 
 a rough surface. 
 
 121. 
 
 Blue and red about alike; 
 about 30 per cent, blistered 
 and corroded. 
 
 1 27. 
 
 Blue, considerably blistered 
 along the edges, mainly 
 pin-head blisters. Little 
 corrosion. 
 Red, about the same but 
 some large marginal blis- 
 ters. The red had a smooth 
 surface but the blue was 
 rough. 
 
 1 1 6. 
 Both sides in good condition, 
 but showed some signs of 
 incipient blistering about 
 the edges. 
 
 122. 
 
 Pin-head blisters along the 
 edges ; general condition 
 all right. 
 
 128. 
 Baked side, nine or ten blis- 
 ters of about i ins. diam- 
 eter and considerable cor- 
 rosion; remainder of sur- 
 face good. 
 Unbaked side, i per cent, of 
 the surface near the edges, 
 with small blisters showing 
 some corrosion : the rest of 
 the surface all right. 
 
 117. 
 Perfect. 
 
 123. 
 Baked side all right. 
 Unbaked side, seven or eight 
 small blisters but no cor- 
 rosion. General condition 
 good. 
 
 1 29. 
 Baked side, a large number of 
 groups (about i in. diam- 
 eter) of small blisters with 
 some corrosion; the rest of 
 the surface all right. 
 Unbaked side, much the 
 same, not as bad. 
 
 118. 
 Perfect. 
 
 124. 
 Both sides badly blistered 
 and corroded along the 
 edge, about 10 per cent, 
 of the surface. Where not 
 blistered all right. 
 
 130. 
 
 About like 1 24. 
 
PROTECTION OF METALS AGAINST CORROSION. 227 
 
 weighed before melting. For example, 20 K. means an oleo- 
 resinous varnish made by melting 100 Ibs. of Kauri resin and 
 combining with it 20 gals., or 154 Ibs., of linseed-oil. The com- 
 pound was subsequently thinned with a suitable amount of spirit 
 of turpentine, but as this is volatile, no mention is made of that in 
 the abbreviation. 
 
 The result of this test was of so much interest that other plates 
 ivere prepared and coated. About three hundred plates were pre- 
 pared and the time of preparation was nearly a year, so that it 
 was late in June, 1897, before the plates were in place and the 
 exposure actually begun. The greater part of these were steel 
 plates which were painted in triplicate sets, with the intention of 
 putting one set in the sea-water in the New York Navy Yard, 
 one set in the Navy Yard at Norfolk, Va., and a third set in fresh 
 water. The place finally chosen for the last was Lake Cochituate, 
 Mass., part of the original Boston water-supply. 
 
 Besides these there were twenty-five plates of aluminum in 
 each of the Navy Yard sets, but no aluminum plates were put in 
 the fresh- water test because it is well known that pure water does 
 not attack aluminum. It will be observed that in the tables 
 already given the steel plates are numbered from i to 40, and the 
 aluminum from 101 to 130. It was, therefore, decided to number 
 the aluminum plates in this experiment from 151 to 200; the steel 
 plates for the New York Yard from 201 upward; for the Norfolk 
 Yard from 301 upward, and for the fresh- water set from 401 
 upward, and this was done. The aluminum plates were of two 
 sorts, part being commercially pure aluminum, as pure as could 
 be made in 1896, and the remainder were of aluminum alloyed 
 with 5 per cent, of other metal. The plates numbered from 151 to 
 163, inclusive, in the New York set correspond to those numbered 
 from 176 to 187, inclusive, in the Norfolk set, and are pure alu- 
 minum. Those numbered from 164 to 175, New York, correspond 
 to 188 to 200, Norfolk, and are of the aluminum alloy. 
 
 Besides these regular sets of plates, a cage containing twenty- 
 four plates, part steel and part aluminum, which had in 1896 
 been exposed for six months in the New York Yard and are de- 
 scribed in the foregoing tables, were again exposed in the New York 
 
228 TECHNOLOGY OF PAINT AND VARNISH. 
 
 STEEL PLATES. 1896 TEST. 
 
 White Zinc. 
 
 White Zinc. 
 
 White Zinc. 
 
 White Zinc and 
 White Lead. 
 
 8 K. ii,i2. 
 
 Hard and brittle, very 
 few blisters or rust- 
 spots. Outer coat 
 separated from the 
 under - coat when 
 scraped, leaving the 
 latter on the metal. 
 
 8 Z. 23, 24. 
 
 Poor; thin, brittle, 
 many rust-spots. 
 
 
 
 12 K. 9, 10. 
 
 No. 9. A large num- 
 ber of pin-hole rust- 
 spots on one side. 
 Hard and brittle. 
 No. 10. No rust or 
 blisters, hard and 
 brittle. These not 
 easily scraped off 
 while wet. 
 
 
 
 
 20 K. 7 8. 
 
 Good; a few small 
 rust - spots where 
 coating was thin, 
 near the margin ; 
 not easily scraped 
 off when wet. Coat- 
 ing brittle. 
 
 2O Z. 21, 22. 
 
 Good condition, thin 
 and brittle near 
 the margin; could 
 be scraped off with 
 difficulty when wet. 
 
 20 M. 15, 1 6. 
 
 Good condition, ex- 
 cept where the 
 coating was thin 
 and brittle near 
 the margin, where 
 there was some 
 rust. 
 
 20 K. 3, 4. 
 
 First-rate condition ; 
 coating could be 
 peeled off with a 
 knife when first 
 taken from the 
 water ; afterward 
 hardened again. 
 
 30 K. 5,6. 
 
 Tough coating, no 
 corrosion, some 
 small blisters near 
 the margin where 
 the coating was 
 very thin. 
 
 30 Z. 19, 20. 
 
 First-rate condition, 
 tough and adher- 
 ent ; not easily 
 scraped off when 
 wet. 
 
 30 M. 13, 14. 
 
 No. 13. Poor, many 
 minute rust-spots. 
 No. 14. Better; lit- 
 tle rust. Coating 
 tough and good on 
 both where heavy, 
 brittle and poor 
 where thin. 
 
 
 set. Half of these were lost by an accident in the New York 
 Yard, but the remainder are described in the following table, 
 pp. 232-239, their numbers of course being the same as in the 
 table on pp. 228, 229. To make them more prominent, they 
 are also distinguished by the date, 1896, after the number. 
 
 The sets of plates at the Norfolk Navy Yard and at Lake Co- 
 chituate were left untouched until July, 1899, a little more than 
 two years, but those in the New York Yard were in cages which 
 were suspended to a float which was accidentally sunk in July, 1898, 
 and more than half the plates were lost. The remainder, includ- 
 ing part of the 1896 plates just mentioned, were taken out July 
 21, 1898, after an immersion of exactly thirteen months. Besides 
 this loss, one cage or frame containing twenty-five plates Nos. 
 326-350 was lost at Norfolk by the rusting away of the heavy 
 
PROTECTION OF METALS AGAINST CORROSION. 229 
 STEEL PLATES. 1896 TEST. 
 
 White Lead. 
 
 Miscellaneous. 
 
 Miscellaneous. 
 
 8 M. 17,18. 
 
 Poor; coating badly 
 decomposed, the 
 action taking place 
 from the outer sur- 
 face. Not much 
 corrosion. 
 No. 1 8 much better 
 than No. 17. 
 
 31,32,33,34- 
 
 Durable Metal Coating. 
 Nos. 31 and 33 all right except 
 some blisters where the coat- 
 ing was thin. 
 Nos. 32 and 34 not so good, more 
 blisters. 
 Coating could be scraped off 
 while wet. 
 
 Oil. 40. 
 
 Red lead in linseed-oil. 
 A good many small rust -spots, 
 but no general corrosion. Coat- 
 ing considerably decomposed; 
 could be scraped off with diffi- 
 culty. Condition fair. 
 
 
 35,36,37,38. 
 
 Sabin Pipe Coating. 
 All perfect. 
 
 20 K. 25, 26. 
 
 Flamingo red in 20 K. 
 Bad condition, many rust-spots. 
 
 20 K. I, 2. 
 
 No. i. Good, first- 
 rate condition. 
 No. 2. Good, but 
 some small mar- 
 ginal blisters. 
 
 
 20 K. 27, 28. 
 
 Ultramarine in 20 K. 
 Not good; many small blisters, 
 not much rust. 
 
 
 Japan. 39. 
 
 Ivory-black ground in japan. 
 Very bad; rusty all over. 
 
 20 K. 29, 30. 
 
 Chromium oxide in 20 K. 
 Poor; very many small rust- 
 spots. 
 
 galvanized iron chains which suspended it, and the loss of these 
 plates causes vacant places in the table, so that, in order to save 
 space, it has been thought well to put the descriptions of the 
 aluminum and the 1896 plates in these otherwise vacant spaces. 
 If the reader will bear this in mind, little trouble will be found in 
 following out the plan of the table, the discrepancies of which are 
 caused by accidental losses of plates. No plates were lost in the 
 Lake Cochituate set. The cages, or frames, in which the plates 
 were held were suspended in the Navy Yard by chains about six 
 feet below the surface of the water in such a position that the 
 plates were horizontal. Barnacles and other marine organisms 
 attach themselves to the under side of the plates and by sus- 
 pending the plates so that they were horizontal, we had practically 
 a double test, one of the lower sides covered with marine growth 
 
230 TECHNOLOGY OF PAINT AND VARNISH. 
 
 and another of the upper sides which were practically clear. 
 There was no considerable deposit of silt on the plates. In the 
 two years' exposure in the Norfolk Yard the action of these 
 organisms was so severe as to destroy the coatings on the under 
 sides of all the plates with the exception of those coated with the 
 "Sabin Pipe Coating," which was not affected, although oysters 
 $ ins. in length were found growing on it. When these were re- 
 moved the coating was found to be intact. But with this excep- 
 tion it should be remembered in looking over the table that only 
 one side of the plates in the Norfolk set is described, the coatings 
 on the other side being uniformly destroyed, while in the New 
 York and Lake Cochituate sets both sides of the plates are in- 
 cluded in the description. 
 
 The cages containing the plates which were put in Lake 
 Cochituate were laid on the bottom, which was hard and smooth, 
 about 20 feet below the surface. The cages, or frames, naturally 
 laid on their sides, so that the plates were vertical. This made 
 no difference, because fresh-water organisms are rare and they 
 did not attack the plates. 
 
 In this triplicate test the general scheme was to apply to a 
 set of four plates a set of three varnishes containing respectively 
 20, 30, and 40 gallons of oil per 100 Ibs. of resin, and raw linseed- 
 oil. Then for another set of four plates, these same liquids were 
 mixed by grinding with white zinc; another set of four was 
 prepared with white lead; another set with ultramarine blue; 
 another with graphite, and so on. This ought to show whether 
 one pigment is better than another and which vehicle is the best. 
 Besides these, plates were painted with pure red lead in pure 
 linseed-oil, with two mixtures of red lead and white zinc, with 
 purple oxide of iron' (crocus), in oil, and with "Prince's Metallic" 
 oxide of iron, which is a very well-known pigment consisting of 
 iron oxide mixed with various silicates in oil. 
 
 Besides these coatings of known composition, two popular and 
 widely known proprietary paints, the Eureka paint and the graphite 
 paint made by the Detroit Graphite Manufacturing Company, were 
 tried. The oil and proprietary paints were presumed to afford a 
 sort of standard by which the other coatings could be judged. 
 
PROTECTION OF METALS AGAINST CORROSION. 231 
 
 The coating material described in the table as "Spar" is one 
 of the well-known class of spar varnishes used for exterior and 
 marine work, and the kind used was made by Edward Smith & 
 Company. The " I. X. L. No. 2 " is a well-known interior varnish. 
 The substance indicated by the letters "D. M. C." is Edward 
 Smith & Company's Durable Metal Coating, and "S. P. C." is 
 Sab in Pipe Coating, the same as in the former test. "Para- 
 hydric" is a coating similar to Durable Metal Coating, but con- 
 taining less oil, which has been used in painting the interior of 
 water-pipes and for steel in interior construction. "Keystone" 
 is a well-known pigment, probably ground slate, and was used 
 to furnish a pigment composed of silicates for comparison. The 
 iron oxide used is the purest commercial sesquinoxide of iron, 
 containing over 95 per cent, oxide of iron. The purple oxide 
 of iron is oxide which has been subjected to prolonged heating 
 and is supposed to be completely anhydrous. The "iron oxide 
 in shellac" mixture was prepared from a formula furnished by 
 Naval Constructor Bowles. The shellac is pure "D. C." shellac 
 in grain alcohol. The paints known as Raht Jen's, Mclnnes', and 
 Holtzapfel are anti-corrosive and anti-fouling ships '-bottom 
 paints and were furnished and applied by the New York Navy 
 Yard. 
 
 All the paints, except those coated with the Sab in Pipe Coat- 
 ing, which had two coats, received three full coats, well dried 
 between coats. The red-lead paint used weighed about 35 Ibs. 
 to the gallon and was put in with the plate in a horizontal position, 
 on the upper side of the plate. After the paint had set, the plate 
 was turned over and the other side was painted. The red lead 
 was in this way more perfectly applied than it probably can 
 ever be in actual work. The nomenclature and abbreviations 
 in the following table are the same as heretofore, with the follow- 
 ing additions : 
 
 Um. Blue = Ultramarine Blue' 
 
 W. Z. = White Zinc; 
 
 W. L. = White Lead; 
 
 A. = Pure Aluminum; 
 
 A. A. = Aluminum Alloy, 95 per cent. 
 
232 
 
 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Lake Cochituate, Boston. | 
 
 401-20 K. 
 
 No rust except where dam- 
 aged along edges; many 
 very small blisters. 
 
 404-20 M. 
 
 Much rust; coating much 
 injured. 
 
 407-20 Z. 
 
 Not much corrosion, but 
 coating about destroyed. 
 
 402-30 K. 
 Like 401 , not quite so good. 
 
 405-30 M. 
 
 Worse than 404; coating 
 nearly destroyed. 
 
 408-30 Z. 
 
 Like 407, but considerably 
 better. 
 
 403-40 K. 
 Like 401. 
 
 406-40 M. 
 Not quite so bad as 405. 
 
 40Q-Spar. 
 
 Like 408, but perhaps a lit- 
 tle better. 
 
 
 
 
 | Navy Yard, Norfolk, Va. | 
 
 301-20 K. ( 304-20 M. 
 
 301 to 310, coatings not destroyed; all considerably in- 
 jured ; blistered in small spots ; no considerable corro- 
 sion; 301 worst; 306 and 309 best; 307-8 not bad. 
 
 307-20 Z. 
 
 302-30 K. 
 
 305-30 M. 
 
 308-30 Z. 
 
 303-40 K. 
 
 306-40 M. 
 
 3og-Spar. 
 
 
 
 
 | Navy Yard, New York. 
 
 i (i8p6)-W. L. in 20 K. 
 
 Some rust along edges; 
 otherwise in good condi- 
 tion. 
 
 16 (i8Q6)-W. Z. in 20 M. 
 
 One-fifth of one side rusted ; 
 all the rest in good con- 
 dition. 
 
 47 (i8g6)-Spar. 
 
 Coating firm and good; very 
 little rust. 
 
 2 (i8g6)-W. L. in 20 K. 
 Like i. 
 
 1 8 (i8g6)-W. L. in 8 M. 
 
 Paint hard and firm; in 
 good condition. 
 
 35 (i8 9 6)-S. P. C. 
 
 A little corrosion near the 
 edges ; otherwise all right. 
 
 
 20 (i896)-W. Z. in 30 Z. 
 Good. No blisters; no rust. 
 
 113 (i8Q6)-S. P. C. 
 
 Two small blisters; other- 
 wise good. 
 
 
 22 (i8g6)-W. Z. in 20 Z. 
 
 Good. Some corrosion 
 along edges. 
 
 
PROTECTION OF METALS AGAINST CORROSION. 233 
 
 4x0-1. X. L. No. 2. 
 
 About like 407. 
 
 4I3-D. M. C. 
 
 Good, except where broken 
 and injured along edges. 
 
 41 7-Parahydric. 
 Numerous isolated rust 
 spots about i in. diam- 
 eter; coating otherwise 
 good. 
 
 Lake Cochituate, Boston. 1 
 
 41 1 -Shellac. 
 
 Very excellent condition. 
 
 414-0. M. C. 
 Like 413. 
 
 41 8-Parahydric. 
 Like 417. 
 
 4i2-Raw oil. 
 
 Surface generally cor- 
 roded; many tubercles. 
 
 4I5-D. M. C. 
 Like 413. 
 
 4i9-Parahydric. 
 Like 417. 
 
 
 4 i6-D. M. C. 
 Like 413. 
 
 42o-Parahydric. 
 Like 417. 
 
 310-1. X. L. No. 2. 
 
 3I3-D. M. C. 
 
 Many small blisters, in 
 outer coat chiefly; very 
 little corrosion. 
 
 3i7-Parahydric. 
 Coating all on; no blisters. 
 
 Navy Yard, Norfolk, Va. 1 
 
 3ii-Shellac. 
 
 Coating practically gone ; 
 badly rusted. 
 
 3I4-D. M. C. 
 Like 313. 
 
 3 1 8-Parahydric. 
 Like 317. 
 
 3i.2-Raw oil. 
 
 Coating destroyed; very 
 badly rusted. 
 
 3I5-D. M. C. 
 Like 313. 
 
 3i9-Parahydric. 
 Like 317. 
 
 
 3 i6-D. M. C. 
 Like 313. 
 
 32o-Parahydric. 
 Like 317. 
 
 124 (i8g6)-Spar, one side 
 baked. 
 
 Very few small blisters, 
 otherwise perfectly good. 
 
 105 (i896)-Chromium ox- 
 ide in 20 K., one side 
 baked. 
 A few blisters : otherwise in 
 excellent condition. 
 
 
 ,M 
 
 
 1 
 
 'd 
 
 1 
 
 1 
 
 
 
 
 104 (i8p6)-W. Z.in2oK., 
 one side baked. 
 
 Like 124. 
 
 
 
 122 (i8g6)-W. Z. in 20 K., 
 one side baked. 
 
 Like 122. 
 
 . 
 
 
234 
 
 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Lake Cochituate, Boston. 
 
 421-8. P. C. 
 Perfect, except where coat- 
 ing is in one or two places 
 broken at edge with cor- 
 rosion. 
 
 425-W. Z. in 20 K. 
 
 Half the surface, along the 
 edges, blistered, with rust 
 underneath. 
 
 428- W. Z. in 20 M. 
 
 Outer layer of coating near- 
 ly destroyed; under-coat 
 good. 
 
 422-8. P. C. 
 Like 421. 
 
 426- W. Z. in 30 K. 
 
 Much better than 425 ; some 
 blisters; little corrosion. 
 
 429- W. Z. in 30 M. 
 
 A few slight rust-spots; 
 outer coat blistered. 
 
 423-8. P. C. 
 Like 421. 
 
 427-W. Z. in 40 K. 
 
 Good condition ; some blis- 
 ters in outer layer of 
 coating; no rust. 
 
 430-W. Z. in 40 M. 
 
 About one-fifth rusted ; thin 
 rust. Blistered ; outer 
 coat chiefly. 
 
 424-8. P. C. 
 Like 421. 
 
 
 
 i 
 
 ^2 
 
 I 
 
 i 
 
 $ 
 r 
 
 321-8. P. C. 
 
 Perfectly good condition. 
 See note in text. 
 
 325-W. Z. in 20 K. 
 Blistered ; not very good. 
 
 179 A I. X. L. No. 2. 
 Coating all gone. 
 
 322-8. P. C. 
 Like 321. 
 
 176 A-20 K. 
 
 Three-fourths of coating 
 destroyed; thin rust. 
 
 1 80 A-Spar. 
 
 Two-thirds of coating gone, 
 but one-third in the mid- 
 dle perfectly good. 
 
 323-8. P. C. 
 Like 321. 
 
 177 A-30 K. 
 Like 176. 
 
 181 A-D. M. C. 
 
 One-fifth gone, one-fifth 
 blistered ; remainder 
 good. 
 
 324-8. P. C. 
 Like 321. 
 
 178 A-40 K. 
 Coating all gone. 
 
 182 A-S. P. C. 
 
 One-tenth gone on one 
 edge; remainder all right. 
 
 
 
 
 154 A-I. X. L. No. 2. 
 
 
 
 
 Varnish half gone. Corro- 
 sion not deep. 
 
 M 
 
 
 
 z 
 i) 
 
 2 
 
 
 151 A-20 K. 
 
 Blistered along edges and 
 a few spots. Varnish 
 firm. Little corrosion. 
 
 155 A-Spar. 
 
 Most of the varnish soft, but 
 some not affected. Not 
 badly corroded. 
 
 1 
 >> 
 > 
 t 
 g 
 
 
 152 A-30 K. 
 
 Much corrosion ; some deep. 
 Coating half gone; re- 
 mainder firm. 
 
 157 A-D. M. C. 
 
 Twenty per cent, blistered 
 around edges. Coating 
 firm; not much corrosion. 
 
 
 
 153 A-40 K. 
 
 Badly corroded; coating 
 nearly all destroyed. 
 
 158 A-S. P. C. 
 
 Excellent. Coating not in- 
 jured, except by acci- 
 dent in removing from 
 frame. 
 
PROTECTION OF METALS AGAINST CORROSION. 235 
 
 43I-W. Z. in 20 Z. 
 
 Not much rust; outer coat 
 badly blistered ; under 
 coat slightly so. 
 
 436-W. Z. in 20 K., baked. 
 
 Almost perfect; still shows 
 glossy surface of varnish. 
 
 439- W. Z. in 20 M., baked. 
 
 Good; coating brittle in 
 places and shows de- 
 terioration. 
 
 Lake Cochituate, Boston. 
 
 432-W. Z. in 30 Z. 
 
 Better than 431. Outer coat 
 blistered. 
 
 437-W. Z. in 30 K., baked. 
 Like 436. 
 
 440-W. [Z. in 30 M., baked. 
 A little better than 439 
 
 433-W. Z. in Spar. 
 Like 432. 
 
 438-W. Z. in 40 K., baked. 
 Like 436. 
 
 44I-W. Z. in 40 M., baked. 
 Almost perfect. 
 
 435-W. Z. in Raw Oil. 
 
 Four-fifths of surface 
 badly rusted; deep cor- 
 rosion. 
 
 
 
 183 A-S. P. C. 
 Perfectly good condition. 
 
 187 A-W. Z. in Spar. 
 Like 184. 
 
 191 AA-I. X. L. No. 2. 
 Coating all gone. 
 
 i 
 
 M 
 
 1 
 
 o 
 ^ 
 
 -^ 
 
 i 
 
 i 
 
 184 A-W. Z. in 30 K. 
 
 Pine; no rusting nor blis- 
 tering. 
 
 1 88 AA-20 K. 
 Coating all gone. 
 
 192 AA-Spar. 
 
 Three-quarters gone ; like 
 189. 
 
 185 A-W. Z. in 40 K. 
 Like 184, but discolored. 
 
 180 AA-30 K. 
 
 Three-quarters gone; small 
 patch in the middle all 
 right. 
 
 193 AA-Spar. 
 Like 192. 
 
 1 86 A-W. Z. in 30 Z. 
 Like 184. 
 
 190 AA 40 K. 
 Half gone; like 189. 
 
 194 AA-D. M. C. 
 
 One-third badly blistered 
 from edges ; remainder 
 good. 
 
 159 A-S. P. C. 
 Like 158 A. 
 
 163 A-W. Z. in Spar. 
 
 Not deeply corroded. Sev- 
 eral large blisters; other- 
 wise in good condition. 
 
 167 AA-I. X. L. No. 2. 
 
 Considerable blistering and 
 corrosion. Coating easily 
 scraped off. 
 
 i 
 
 1 
 
 I 
 
 | 
 
 ^ 
 
 1 60 A-W. Z. in 30 K. 
 
 Upper side perfect; lower 
 side slightly blistered. 
 Coating hard. 
 
 164 AA-20 K. 
 
 Badly corroded; three- 
 fourths of the varnish 
 destroyed. 
 
 1 68 AA-Spar. 
 
 Like 167, but not badly cor- 
 roded. 
 
 . 161 A-W. Z. in4oK. 
 
 No blisters; otherwise like 
 1 60 A. 
 
 165 AA-30 K. 
 Like 164 AA. 
 
 
 162 A-W. Z. in 30 Z. 
 Like 161 A. 
 
 1 66 AA-40 K. 
 Badly blistered, but not 
 badly corroded. Coating 
 on one side firm; on the 
 other soft. 
 
 169 AA-D. M. C. 
 
 Many blisters; very little 
 corrosion ; coating gen- 
 erally firm. 
 
236 
 
 TECHNOLOGY OF PAINT AND VARNISH. 
 
 J Lake Cochituate, Boston. 1 
 
 442-W. Z. in 20 Z., baked. 
 
 Nearly perfect. 
 
 445-W. L. in 20 K. 
 
 Very little corrosion. Some 
 superficial blisters. 
 
 449-Um. Blue in2o K. 
 
 Considerable rust.; not 
 deep; paint practically 
 destroyed. 
 
 443-W. Z. in 30 Z. baked. 
 
 Excellent; no rust; blisters 
 superficial and few. 
 
 446-W. L. in 30 K. 
 
 Good condition; no rust. 
 Some superficial blisters. 
 
 450 Um. Blue in 30 K. 
 A little worse than 449. 
 
 444-W. Z. in Spar, baked. 
 Like 443 .or better. 
 
 447-W. L. in 40 K. 
 Like 446. 
 
 45i-Um. Blue in 40 K. 
 Worse than 449; deep rust. 
 
 
 % 448-W. L. in Raw Oil. 
 
 Much deep corrosion ; 
 about half the plate in 
 good condition. 
 
 452-Um. Blue in Raw Oil. 
 
 Like 451; whole surface 
 rusted. 
 
 i 
 jy 
 
 1 
 
 -~ 
 
 ? 
 i 
 
 195 AA-W. Z. in 30 K. 
 
 Good; blistered a little on 
 the edges. 
 
 199 AA-S. P. C. 
 
 Blistered a little from 
 edges ; otherwise all 
 right. 
 
 
 
 196 AA-W. Z. in 40 K. 
 
 Fine, but discolored; like 
 185. 
 
 200 AA-S. P. C. 
 Like 199. 
 
 
 197 AA-W. Z. in 30 Z. 
 
 Fine, but blistered a little 
 along the edges. 
 
 
 3Si-Um. Blue in 40 K. 
 Nearly all gone. 
 
 198 AA-W. Z. in Spar. 
 Like 197. 
 
 
 352-Um. Blue in Raw Oil. 
 
 Coating all gone; very 
 badly rusted. 
 
 1 Navy Yard, New York. 
 
 170 AA-W. Z. in 30 K. 
 
 Very little corrosion. Blis- 
 ters amount to i per cent. 
 Coating good. 
 
 174 AA-S. P. C. 
 In perfectly good condition. 
 
 
 171 AA-W. Z. in 40 K. 
 
 Good, but not equal to 
 170 AA. 
 
 175 AA-S. P. C. 
 Like 174. 
 
 
 172 AA-W. Z. in 3 Z. 
 
 No corrosion; no blisters; 
 excellent condition. 
 
 
 25i-Um. Blue in 40 K. 
 
 Very many small blisters; 
 very little corrosion. 
 
 173 AA-W. Z. in Spar. 
 About like 172. 
 
 
 252-Um. Blue in Raw Oil. 
 
 Uniformly corroded; coat- 
 ing all gone. 
 
PROTECTION OF METALS AGAINST CORROSION. 237 
 
 453-Graphite in 20 K. 
 
 Very good; some small 
 blisters. 
 
 457-Keystone in 20 K. 
 
 Good condition; no rust; 
 scene small blisters. 
 
 46i-Iron Oxide in 20 K. 
 
 Very little rust; small blis- 
 ters in outer coat. 
 
 o 
 I 
 
 8 
 
 
 I 
 
 454-Graphite in 30 K. 
 Like 45 3. 
 
 458-Keystone in 30 K. 
 Like 457. 
 
 462-Iron Oxide in 30 K. 
 Better than 461 ; no rust. 
 
 455-Graphite in 40 K. 
 Like 453- 
 
 459-Keystone in 40 K. 
 
 A little rust; many small 
 superficial blisters. 
 
 463-Iron Oxide in 40 K. 
 Like 462. 
 
 456-Graphite in Raw Oil. 
 
 Deeply and generally 
 rusted; about one-tenth 
 of the paint still good. 
 
 46o-Keystone in Raw Oil. 
 
 Badly and deeply rusted; 
 patches of paint still 
 good. 
 
 464-Iron Oxide in Raw 
 Oil. 
 Corrosion deep and gen- 
 eral; paint all gone. 
 
 353-Graphite in 20 K. 
 
 Three-quarters gone; much 
 rust. 
 
 357-Keystone in 20 K. 
 
 Coating blistered and one- 
 quarter gone. 
 
 36i-Iron Oxide in 20 K. 
 
 Pretty good condition; a 
 few blisters. 
 
 Navy Yard. Norfolk, Va. 
 
 354-Graphite in 30 K. 
 Half gone; much rust. 
 
 358-Keystone in 30 K. 
 
 Blistered, but not de- 
 stroyed. 
 
 362-Iron Oxide in 30 K. 
 Not quite as good as 361. 
 
 355-Graphite in 40 K. 
 One-quarter gone. 
 
 359-Keystone in 40 K. 
 
 Blistered, but not in bad 
 condition. 
 
 363-Iron Oxide in 40 K. 
 Like 361. 
 
 356-Graphite in Raw Oil. 
 
 Nearly all gone; badly 
 rusted. 
 
 36o-Keystone in Raw 
 Oil. 
 All gone; badly rusted. 
 
 364-Iron Oxide in Raw 
 Oil. 
 Like 360. 
 
 253~Graphite in 20 K. 
 
 A few blisters ; very little 
 corrosion. 
 
 257-Keystone in 20 K. 
 
 No corrosion ; numerous 
 very small blisters. 
 
 26i-Iron Oxide in 20 K. 
 
 Blistered, but not very 
 badly. Not much corro- 
 sion. 
 
 a 
 
 ^ 
 
 0> 
 
 
 
 s 
 
 
 >> 
 
 > 
 
 cfl 
 g 
 
 254-Graphite in 30 K. 
 Like 253. 
 
 258-Keystone in 30 K. 
 Like 257. 
 
 262-Iron Oxide in 30 K. 
 
 Like 261. Not deeply 
 rusted. 
 
 255-Graphitein 40 K. 
 
 No corrosion. Paint in 
 good condition. Numer- 
 ous very small blisters. 
 
 25Q-Keystone in 40 K. 
 Like 257. 
 
 263-Iron Oxide in 40 K. 
 Like 262. 
 
 256-Graphite in Raw Oil. 
 
 Uniformly corroded; coat- 
 ing all gone. 
 
 26o-Keystone in Raw Oil. 
 
 Coating destroyed and 
 plate badly corroded. 
 
 264-Iron Oxide in Raw 
 Oil. 
 Like 260. 
 
238 
 
 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Lake Cochituate, Boston. 
 
 465-Red Lead in Raw Oil. 
 Paint still tough; looks 
 well. Blisters from the 
 bottom with slight cor- 
 rosion beneath. 
 
 469-Eureka Paint. 
 
 General corrosion ; paint 
 entirely destroyed. 
 
 
 
 47o-Detroit Graphite. 
 
 Like 469 ; paint nearly all 
 destroyed. 
 
 475-International Holtz- 
 apfel. 
 Like 469. 
 
 467-Prince's Metallic in 
 Raw Oil. 
 About one-quarter deeply 
 rusted; paint practically 
 all gone. 
 
 47 2-Iron Oxide in Shellac 
 Mixture. 
 Good condition; about 2 
 per cent, rusted. 
 
 477-Red Lead and W. Z. 
 in Raw Oil. 
 Many deep rust-spots; 
 about 5 per cent.; re- 
 mainder good. 
 
 468-Purple Oxide in Raw 
 Oil. 
 Like 467. 
 
 
 478-Red Lead and W. Z. 
 in Raw Oil. 
 Like 477. Not nearly as 
 good as 465. 
 
 . Navy Yard, Norfolk, Va. 
 
 3 6s-Red Lead in Raw Oil. 
 
 Coating destroyed ; plate 
 badly rusted. 
 
 369-Eureka Paint. 
 Like 365. 
 
 374-McInnes' Paint. 
 Like 372. 
 
 
 37o-Detroit Graphite. 
 Like 365. 
 
 375-International Holtz- 
 apfel. 
 Like 365. 
 
 367-Prince's Metallic in 
 Raw Oil. 
 Like 365. 
 
 372-Iron Oxide in Shellac 
 Mixture. 
 Paint destroyed; general 
 but not deep corrosion. 
 
 377-Red Lead and W. Z. 
 in Raw Oil. 
 Like 365. 
 
 368-Purple Oxide in Raw 
 Oil. 
 Like 365. 
 
 373-Rahtjen's Paint. 
 Like 365. 
 
 378-Red Lead and W. Z. 
 in Raw Oil. 
 Like 365. 
 
 Navy Yard, New York. 
 
 265-Red Lead in Raw Oil. 
 
 Coating badly destroyed. 
 Considerable corrosion. 
 
 26g-Eureka Paint. 
 Like 260. 
 
 274-McInnes' Paint,. 
 
 In good condition: no bar- 
 nacles. 
 
 
 27o-Detroit Graphite. 
 Like 260. 
 
 275-International Holtz- 
 apfel. 
 Paint badly gone; much 
 corrosion ; many small 
 barnacles. 
 
 267-Prince's Metallic in 
 Raw Oil. 
 Like 260. 
 
 272-Iron Oxide in Shellac 
 Mixture. 
 A few blisters; otherwise 
 in good condition. 
 
 277-Red Lead and W. Z. 
 in Raw Oil. 
 Coating thin; gone in 
 many places; consider- 
 able corrosion. 
 
 268-Purple Oxide in Raw 
 Oil. 
 Like 260. 
 
 273-Rahtjen's Paint. 
 
 Paint badly gone; consid- 
 erable rusting. Many 
 small barnacles. 
 
 278-Red Lead and W. Z. 
 in Raw Oil. 
 Like 277. 
 
PROTECTION OF METALS AGAINST CORROSION. 239- 
 
 481 20 K baked 
 
 48430 M. baked. 
 
 487-1. X. L. No. 2, baked. 
 
 
 Practically perfect; coat- 
 ing still glossy. 
 
 Several deep spots of rust, 
 coating badly blistered. 
 
 Like 481. 
 
 a 
 
 482-30 K., baked. 
 Like 481. 
 
 485-30 Z., baked. 
 Like 481. 
 
 4 88-Raw Oil, baked. 
 
 Badly and deeply rusted. 
 Two-fifths of the surface 
 good. 
 
 3 
 
 1 
 
 a; 
 
 1 
 
 483-40 K., baked. 
 Like 481. 
 
 4 86-Spar. baked. 
 Like 481. 
 
 4 8g-D. M. C., baked. 
 
 Fine; a few small blisters 
 in the outer coat. 
 
 ^ 
 
 '.H 
 
 y 
 
 C 
 
 0) 
 
 M 
 
 a 
 
 
 
 
 ,-J 
 
 381-20 K., baked. 
 
 Half of the coating de- 
 stroyed; the rest good. 
 Not much rust. 
 
 384-30 M., baked. 
 Like 382. 
 
 387-1. X. L. No. 2, baked. 
 Like 386. 
 
 J 
 
 382-30 K., baked. 
 
 Four-fifths destroyed; very 
 little rust. 
 
 385-30 Z., baked. 
 Like 382. 
 
 388-Raw Oil, baked. 
 All gone; rusted. 
 
 Norfolk, V 
 
 383-40 K., baked. 
 Like 382. 
 
 386-Spar, baked. 
 Nearly all gone; little rust. 
 
 389-0. M. C., baked. 
 
 Three-quarters gone; re- 
 mainder good; very little 
 rust. 
 
 'H 
 
 a 
 > 
 
 t 
 
 d 
 
 
 
 
 '/< 
 
 281-20 K., b,aked. 
 
 Plate thinly rusted along 
 the edges. 
 
 284-30 M., baked. 
 
 Many small and some me- 
 dium-sized blisters. Not 
 badly rusted. 
 
 287-1. X. L. No. 2, baked. 
 
 Not much corrosion; very 
 small blisters. 
 
 
 282-30 K., baked. 
 
 Small blisters, with thin 
 rust beneath, over most 
 of the plate. 
 
 285-30 Z., baked. 
 
 Good condition. Very little 
 rusting. Very small blis- 
 ters. 
 
 288-Raw Oil, baked. 
 
 Badly corroded. Coating 
 destroyed. 
 
 1 
 1 
 
 283-40 K., baked. 
 
 Very small blisters; not 
 much mst. 
 
 286-Spar, baked. 
 
 Coating badly destroyed; 
 much corrosion. 
 
 28g-D. M. C., baked. 
 
 Very many small blisters. 
 Not very much corro- 
 sion. 
 
 I 
 
 >, 
 
 1 
 
 
 
 
 
.1240 TECHNOLOGY OF PAINT AND VARNISH. 
 
 A careful study of the plates after their removal from the 
 ivater showed that it is generally true of all the better class of 
 coatings that corrosion begins at the edge of the plate. In the 
 case of aluminum plates it seemed evident to the writer that some 
 of these coatings, notably the spar varnish and the "Durable 
 Metal Coating, " had been gradually thrown off by corrosion creep- 
 ing from the edge, probably from some mechanical injury under 
 the varnish, a patch of which remained uninjured, elastic, and 
 apparently without deterioration on the middle of the plate. 
 This fact should not be lost sight of in considering this matter, 
 and is one of the points shown by an inspection of the plates, but 
 not brought out easily in a description. As a rule, with the 
 less effective coatings, they begin to deteriorate from the surface, 
 which becomes rough; then little blisters appear which are 
 caused by the separation of the last coat from those beneath; 
 finally the undercoat blisters, in which case it is found almost 
 invariably that rust has formed under the blister. If, however, 
 the coating is porous, and this seems to be the case with the 
 ordinary oil paints, the water reaches the metal and causes rust. 
 This throws off the paint-film, and the corrosion spreads rapidly 
 in this way. 
 
 These tests undoubtedly seem to prove, and I think they do 
 prove, that varnish forms a much more continuous (less porous) 
 film than oil, which agrees with all that has heretofore been 
 said of the nature of varnish-films. In all these tests the oil paints 
 have failed without exception, while the corresponding varnish 
 paints remained in most cases in good condition. The charac- 
 ter of the pigment does not seem to have much influence. All 
 the oil-paint samples were so badly rusted that differentiation 
 among them was impossible. It may be that an earlier inspec- 
 tion would have shown differences, but as it was, the appearance 
 of all these plates when removed from the water was so similar 
 that it seems unlikely, and certainly the varnish paints did not 
 show any great difference in the matter of the pigments, except 
 that white zinc seemed to be somewhat the best. The iron 
 oxides, graphites, and pulverized slate were all alike. The red 
 lead, in the Lake Cochituate and New York sets, was far better 
 
PROTECTION OF METALS AGAINST CORROSION. 241 
 
 than any of the oil paints. The mixtures of red lead and white 
 zinc were markedly inferior to red lead alone. In the Norfolk 
 test, which was much more severe, the red lead had finally been 
 quite destroyed. Deterioration in the case of red lead always 
 seems to start from centres. In the Lake Cochituate set the 
 red lead was in pretty good condition, but as it showed numerous 
 rust-spots, without superficial blisters, but all defects running 
 through to the metal, it probably would not have lasted more than 
 a year or so longer. Most of the varnish paints were much 
 better than the red lead. A study of the varnishes applied with- 
 out pigment seems to show that in the fresh-water exposure the 
 process of baking was, on the whole, of advantage, but not greatly 
 so. In the salt water the unbaked varnishes were better than 
 the same varnishes baked. This agrees with the results of the 
 1896 tests. The Manila varnishes are clearly inferior to the 
 Kauri and Zanzibar. The ''Durable Metal Coating" was best 
 of all. This is doubtless due, in a large degree, to the fact that 
 this varnish, which is intended especially for the protection of 
 structural steel, is made with a heavy body and the film is of greater 
 thickness than is the case with varnishes intended for woodwork. 
 Its composition has also been very carefully studied and designed 
 to secure great durability, which is of much less importance 
 than other qualities in ordinary varnishes. 
 
 By far the best results, however, with the exceptions to be 
 hereafter noted, were obtained from the best of the enamel paints. 
 Here, also, the Manila varnishes were decidedly inferior, and in 
 my opinion these should be excluded hereafter from any such 
 tests, although they make a very good showing on wood. In 
 the enamel or varnish paints, those made with the more elastic 
 varnishes (those containing the most oil) were decidedly the 
 better. The extreme durability of these is well shown by the 
 1896 plates. These were first exposed to the air two or three 
 months, then they were in the sea- water six months, then exposed 
 to the air nearly a year, then under water thirteen months, and 
 have since been exposed to the air five years, making a total of 
 eight years, and they are still, to all intents, perfect. It is true 
 that the air exposures have been indoors, but most paints rapidly 
 
242 TECHNOLOGY OF PAINT AND VARNISH. 
 
 lose their coherence when, after a prolonged immersion, they 
 are exposed to the air. Two years' continuous submersion in 
 fresh water has not injured some of these enamels, and two years 
 in the excessively severe exposure at the Norfolk Navy Yard 
 has left several of them in good condition, a few being practi- 
 cally uninjured. Undoubtedly the most obvious and conspicu- 
 ous and the most instructive part is the total and absolutely 
 universal failure of linseed-oil films, either alone or mixed with 
 any of the numerous pigments which were tried, while the corre- 
 sponding varnishes and enamel paints made with the same pig- 
 ments were in fair to good condition. It is not to be forgotten, 
 however, that the only varnishes used in this test were those 
 having 20, 30, and 40 gallons of oil to the unit ioo Ibs. of resin. 
 The 30 and 40-gallon varnishes may be regarded as special struc- 
 tural varnishes, being more elastic and less brilliant and hard 
 than are acceptable for any ordinary commercial work; the 
 20-gallon varnishes, which made the poorest showing, being the 
 only really commercial varnishes in these tests, except the spar, 
 which is intermediate between the twenties and thirties, made 
 especially for marine use, and the " Durable Metal Coating," a 
 highly elastic special varnish made exclusively for structural 
 metal protection. The relatively poor showing made in 1896 
 by the 8- and i2-gallon varnishes sufficiently proves that the best 
 ordinary varnishes, though made with the highest skill and of the 
 most expensive materials, are unfit for prolonged and severe 
 exposures. The results which are likely to be obtained from 
 the use of common cheap varnishes may safely be left to the 
 imagination of the reader. The great durability of the varnish 
 and enamel films in these tests confirms strikingly the opinion 
 long held by the writer that properly made varnish-films are 
 much more impervious and resistant than any others. The excep- 
 tional cases to be noted are: 
 
 First. The "Sabin Coating," a baked enamel, which is so 
 much superior to the others as to form a class by itself, and 
 
 Second. The extraordinary showing made by pure shellac 
 varnish in the Lake Cochituate test. 
 
PROTECTION OF METALS AGAINST CORROSION. 243 
 
 Shellac Varnish in Fresh Water. Shellac varnish is simply 
 a solution of shellac resin, which is chemically an acid substance, 
 in alcohol. There are many grades of shellac; the one used 
 was what has for many years been known as "D.C." Orange 
 Shellac, and it was dissolved in pure 97 per cent, grain (ethylic) 
 alcohol. Being an acid substance, it is attacked readily by the 
 ammonia in the atmosphere. It is removed easily by soap and 
 water. It has never been considered a durable varnish as ordi- 
 narily used on woodwork, and it does not stand at all in the sea- 
 water tests, but two years' exposure under 20 feet of fresh water 
 does not seem to have injured it sensibly. This may be a serious 
 matter, for while in this regard it is no better than some other 
 varnishes which cost less money, shellac varnish has some impor- 
 tant and exceedingly desirable qualities which no other varnish 
 has. For example, occasionally we encounter the problem of 
 repainting a large section of large water-pipe which can be 
 spared for use only a few days. The interior of this pipe is damp. 
 The best that can be done with it is to get out most of the visible 
 water, but the cold surface of the metal will always be damp. 
 No ordinary varnish will stick to such a surface, and corrosion 
 will probably be set up at once. No oleo-resinous varnish of 
 ordinary character, of sufficient durability to be worth putting 
 on, will dry in the limited time at our disposal. But shellac 
 is dissolved in a vehicle which has an intense affinity for water, 
 and a thin film of dew will be instantly absorbed and removed 
 by the evaporation of the slightly diluted alcohol; and shellac, 
 if applied in a thin coat, dries with the greatest rapidity. Three 
 coats may be applied in eight to twelve hours. There is no 
 unpleasant or dangerous odor, though ventilation should be 
 secured both on account of the risk of fire and because working 
 in an atmosphere of alcoholic vapor produces intoxication. It 
 certainly seems from this test as though we should be justified 
 in using shellac varnish in such a case. It is expensive, of course, 
 and it is almost certain that the cheaper grades, which are found in 
 ordinary use to be very much inferior in durability, would not be 
 so efficient. In any case, it would not be necessary to use it 
 
244 TECHNOLOGY OF PAINT AND VARNISH. 
 
 when the conditions are such that some equally good (or better) 
 but slower-drying coating can be used. 
 
 During the years which have elapsed since these tests were 
 made the writer has given considerable attention to the subject 
 of ships'-bottom paints, which are all made with a quick-drying 
 spirit varnish as the vehicle for the first coat, and there is no 
 doubt that these varnishes act as shellac acted in this test. Of 
 course none of these have as much durability, because they are 
 in sea-water instead of fresh water, but they are, like shellac, 
 coatings which will not stand weather exposures for even a few 
 months, but when put under water immediately after their appli- 
 cation they last six to twelve months. This is well-established 
 practice, known to all who have the care of ships, and strongly 
 confirms the opinion just expressed, that the use of shellac in 
 such a case as has been described could not be regarded as an 
 unwarranted experiment. 
 
 It is sometimes objected to these submarine tests that they 
 are of value only as regards the same conditions, and there is 
 some justice in such a criticism, but it is much weakened by the 
 obvious fact that there is a practical agreement between the 
 fresh-water and the sea-water tests. The latter were most severe, 
 but in most cases the difference has been one of degree only. 
 And in the rather large experience of the writer and his asso- 
 ciates these tests seem to agree in general with aerial exposures, 
 reasonable exception being made in the case of coatings intended 
 expressly for marine or for aerial use. The zinc and lead enamels 
 make a rather better relative showing under water than in 
 weather exposures, although excellent for the latter. 
 
 Laboratory Tests not Decisive. Exposure tests, such as these, 
 are of much more importance than laboratory tests. The manu- 
 facturers of paints and varnishes, some of whom are probably 
 the best experts in this matter, never depend on any but an expo- 
 sure test. It is by no means impossible that rapid laboratory 
 tests may yet be devised, but such crude ones as have been so 
 far proposed are in most cases of little value. Such a test, for 
 example, is that with caustic alkali. This is a substance unknown 
 
PROTECTION OF METALS AGAINST CORROSION. 245 
 
 in nature, and no good paint will stand it, while a perfectly worth- 
 less paint may be made which will stand it very well. A nitric- 
 acid test is of the same. sort. It will simply burn up any organic 
 substance, and some of the best linseed- oil paints yield to it most 
 readily. It would hardly be regarded as a fair test of the com- 
 parative health of a dozen animals to administer to each of them 
 a couple of ounces of nitric acid and watch to see which lived 
 longest, yet probably each could take a few drops of it per day 
 without inconvenience. This is about what many of the so- 
 called paint tests amount to. Some laboratory tests are of some 
 value, but none is conclusive. A heat test is at present popular. 
 The painted sample is heated to perhaps 400 Fahr. for a time 
 and its subsequent appearance studied, on the supposition that 
 the rapidly increased oxidation at high temperatures may bring 
 about the same changes which will occur at ordinary tempera- 
 tures slowly. This is plausible and there is something in it, but 
 it is applicable only to such coatings as are intended to stand a 
 high heat because other changes than oxidation are involved. 
 It has already been observed that we know of instances where 
 oak beams have been exposed to the air for a thousand years 
 without injury, while two hours in an oven at 400 Fahr. will 
 begin the decomposition of wood. Now the ratio between two 
 hours and a thousand years is as one to over four millions, which 
 shows the utter absurdity of any such test if applied to miscel- 
 laneous coatings. The preceding tables show the same thing in 
 a different way. Some of the coatings were improved by baking, 
 others were injured. Those which were designed by the makers 
 to be baked were bettered, and those which were planned to give 
 the best results without baking were injured. To make a suitable 
 compound to be applied by baking at a high temperature which 
 will show mechanical toughness, elasticity, and hardness, com- 
 bined with chemical inertness and permanence in the finished 
 product, is the most difficult thing yet attempted in this kind 
 of work. In such a compound the process of baking effects a 
 chemical union among its constituents as well as with the atmos- 
 pheric oxygen. In what has been said about the varnishes and 
 
246 TECHNOLOGY OF PAINT AND VARNISH. 
 
 enamel paints employed in the foregoing tests, the subject of the 
 use of these compounds for the protection of steel is tolerably well 
 covered. These experiments are, of course, greatly amplified 
 and supplemented by the experience of the author in the actual 
 protection of structures in great variety, leading to the following 
 general conclusions: 
 
 Ordinary varnishes are made to combine two functions; one 
 is the protection of the surface to which they are applied, the 
 other is to provide it with a hard and brilliant coating which 
 serves for ornament. To secure the latter it is necessary to have 
 the resin constitute about one-third to three-elevenths of the 
 weight of the dry film; these proportions correspond to varnishes 
 made with from 20 to 26 gals, of oil to 100 Ibs. of unmelted 
 resin. Varnishes made for interior use have sufficient dura- 
 bility even if the proportion of resin exceeds this, and as the resin- 
 ous ingredient increases, so does the brilliancy of the varnished 
 surface, and polishing-varnishes seldom have more than about 
 60 Ibs., say 8 gals., of oil to 100 Ibs. of resin, or the film will 
 contain considerably more than half its weight of resin, after 
 allowing for the loss of the latter in melting. Such is the char- 
 acter of commercial varnishes; but when we have reached the 
 maximum of 26 gals, of oil we have only begun to approach 
 the amount necessary for the highest degree of durability with- 
 out adornment, which is sought in the protection of metal from 
 corrosion. 
 
 Varnish for Steel Structures. For this purpose a varnish 
 of 26 gals, of oil to the 100 Ibs. of resin may perhaps answer, but 
 we know that 30 gals, is better and for many places a 4o-gal. 
 varnish is better than a 30. The broad statement may then be 
 made that varnishes made for any ordinary use on wood are not 
 suitable, not sufficiently elastic, for use on structural steel; and 
 conversely, that a varnish soft and elastic enough to be right 
 for the latter purpose has not enough hardness and lustre for 
 general use. It will, of course, be much harder and more lus- 
 trous than an oil-film, because oil is the softening ingredient 
 in varnish, and the added resin imparts hardness and brilliancy 
 
PROTECTION OF METALS AGAINST CORROSION. 247 
 
 and smoothness of surface; and it also acts, as has been 
 explained, as a flux, promoting in an extraordinary degree the 
 uniform and continuous oxidation of the compound (or the oil 
 which it contains) and thus producing a continuous and non- 
 porous film. A 4o-gal. varnish contains in the dry film resin in 
 the proportion of i part to 4 parts of oil; this may seem to the 
 unpractised reader, or perhaps even to the experienced user of 
 hard varnishes, not enough to have much effect, but it is. Prob- 
 ably almost every practising chemist has some time tried to 
 dissolve an old gold pen in nitric acid; the base metal, chiefly 
 copper and zinc, alloyed with the gold not only makes the article 
 cheaper, but -adds to its rigidity and elasticity, and frequently 
 amounts to two-thirds of the weight; and this is easily soluble in 
 acid, in which the gold is insoluble; but every one who has tried 
 it has been astonished to see how much the small amount of gold 
 protects the large amount of base metal, and how long a time it 
 takes to dissolve out the latter. It is exactly so with a varnish: 
 the effect of the resinous ingredient is out of all proportion to the 
 amount present. It is quite likely that this proportion of 4 parts 
 of oil to i of the melted resin is as great as can be made to enter 
 into true combination and that any further increase only dilutes 
 the varnish with oil ; certainly the making of a really good varnish 
 with so much oil as this is a matter of difficulty; in fact, as a 
 general rule, the less oil there is in a varnish the easier it is 
 to make, and a ic-gal. varnish, for example, diluted with 10 gals, 
 of oil is not in the least like a 2o-gal. varnish. The oil and resin 
 must be combined in the making, and no varnish can have a 
 high degree of durability unless its ingredients are thoroughly 
 united. It is, moreover, desirable, indeed indispensable, for 
 reasons already explained, that it should contain a minimum 
 amount of "drier," or lead and manganese compounds. There 
 are structures which, on account of their location and use, require 
 a varnish having more than the minimum degree of hardness 
 and smoothness in the coating. Where the proportion of oil 
 must fall as low as thirty gallons, perhaps sometimes even less, 
 such things are best known by experience and observation. The 
 
248 TECHNOLOGY OF PAINT AND VARNISH. 
 
 making of varnishes for such work is not a job for the inex- 
 perienced amateur, but for the scientific investigator, who may 
 well be, in the best sense, an amateur varnish-maker, it offers a 
 large and important field for practical and theoretical research. 
 
 The most serious objection to the use of varnish as a protec- 
 tive coating is the thinness of the film, which, although greater 
 than that of an oil-film, is less than that of a good oil paint, and 
 is usually too thin for permanent service. This may be remedied 
 by making the varnish heavier in body or more viscous, and it 
 may be thus made so thick that any desired thickness of film can 
 be obtained. If in making varnish the cooking be stopped as 
 soon as the oil and resin have combined enough so that they will 
 not separate on cooling, the product, if it contains a large pro- 
 portion of oil, will be sufficiently fluid for use with a compara- 
 tively small proportion of spirits of turpentine; it thus contains a 
 large percentage of non- volatile ingredients, which in itself is of 
 advantage; but in such a varnish the oil has not become suffi- 
 ciently united with the resin, and its durability will not be as 
 great as that of a well- cooked varnish. 
 
 Enamel Paints. It has already been said that pigments can 
 be used in varnish just as in oil, and the varnish paints, or enamels, 
 as they are sometimes called, are, if made of proper materials, 
 highly suitable for painting structural metal, especially bridges. 
 Some of these varnish paints, which naturally exceed in thick- 
 ness and hardness of film the varnishes themselves, while they 
 retain all their elasticity, are coatings of great beauty and per- 
 manence. The cost of properly applying a protective coating to 
 structural metal is often as great as the cost of the paint or var- 
 nish itself and not infrequently much more. There are places 
 where it costs $3 or $4 for labor to apply a gallon of varnish to a 
 clean surface, and it is not at all uncommon to spend $3 in clean- 
 ing the surface to which a gallon is to be applied. 
 
 True Economy in Painting. Quite a good many bridges are 
 now cleaned either wholly or in part with the sand-blast, and this 
 probably cannot be done at present for less than 2 cents per square 
 foot. A gallon of paint will cover at least 300 sq. ft.; the cost 
 
PROTECTION OF METALS AGAINST CORROSION. 249 
 
 of sand-blasting this would be at least $6. A dollar would proba- 
 bly be the minimum cost of labor to apply a gallon of paint in such 
 a place; this makes $7*. Suppose that a gallon of good oil paint 
 can be had for a dollar; the total cost is $8. Now suppose that 
 a varnish enamel paint for the purpose can be had for $3 a gallon; 
 the cost of a gallon of such paint would be when applied $10. 
 Obviously, if it lasts 25 per cent, longer than the oil paint it is 
 as cheap, and it certainly looks better. If, however, it costs only 
 $2 to clean the metal, the prices will become $4 and $6, and the 
 enamel must last 50 per cent, longer, and so on. The results of 
 the tests which have been given in detail, and it may be here 
 said that all the plates of the 1897-99 tests were exhibited before 
 the American Society of Civil Engineers, in New York, the Bos^ 
 ton Society of Civil Engineers, and the Engineers' Club, of Phil- 
 adelphia, certainly indicate that the best varnishes and varnish 
 enamels exceeded the best oil paints, and even red lead, more than 
 100 per cent., and probably very much more than that; and I 
 believe this is fully borne out in .practice, and that where perma- 
 nent protection is wanted and repainting from time to time is 
 anticipated, a good enamel paint, by preference one not contain- 
 ing much white pigment, is an economical paint to use. I am 
 also satisfied that a good durable black varnish without pigment, 
 containing a reasonable amount of asphaltum and a large pro- 
 portion of oil, can be made for such purposes at a very moderate 
 price and will outlast any oil or red-lead paint. Asphaltum, if 
 so combined as to prevent its crumbling, is very efficient in retard- 
 ing oxidation, and is a most valuable ingredient in a varnish where 
 its color is not an objection. It has so far been quite impossible 
 for any one to produce a baking enamel without asphaltum which 
 can at all compare in durability and indifference to chemical 
 action with the best of the enamels in which it is an ingredient. 
 
 Covering Capacity of Paint. In painting structural steel or 
 iron it is a general rule that any good paint or varnish covers 
 -about 300 to 400 sq. ft. to the gallon, one coat. Almost any paint 
 may be brushed out thin enough to cover from 50 to 100 per cent, 
 more surface than this, but this is not profitable, for the labor 
 
250 TECHNOLOGY OF PAINT AND VARNISH. 
 
 costs more than the paint, and the object of the painter should 
 always be to apply as heavy a coat as will dry uniformly. On 
 rough surfaces more paint is used than on smooth and less is used 
 on the second coat than the first. Tables have been published 
 showing much greater covering capacity than 400 sq. ft., and no 
 doubt 450 is a practicable number on flat, smooth work, such as 
 roofs and the like, and I have been shown evidence by railway 
 companies that red lead may be depended on to cover at least 
 600, but I have observed that some of these people who find such 
 high covering capacity are always finding fault with the dura- 
 bility of the paint, which is probably evidence that they are hav- 
 ing it brushed out too thin, and some of them follow the practice 
 already commended, of having a regular painter's crew retouching 
 all doubtful spots continually, so that they are unable to judge of 
 the economy of thin painting. Besides this, it is not to be for- 
 gotten that the surface painted is rarely measured, but is usually 
 guessed, and a guess usually allows for more work than has been 
 done. Very opaque pigments, such as are commonly used in 
 structural work, iron oxides, graphites, carbon pigments, and red 
 lead, lend themselves to this practice of thin painting, but this, 
 though a merit in a decorative paint, is the opposite in a struc- 
 tural one, where thickness of film is one of the prime requisites. 
 Anything which makes it more troublesome to get good work 
 done is objectionable, for it is natural to neglect doing that which 
 can be avoided, and even with the best intentions men forget; 
 they always have, and they always will; the intention is lost 
 sight of in the routine of daily toil. On this ground the use of 
 the less opaque varnishes and varnish paints is preferable; the 
 workmen can see as they work if they are putting on too thin a 
 coat. 
 
 The selling price of a paint or other protective coating often 
 determines the question of its use or the reverse. Economy is 
 always desirable, but it is not always gained by the purchase of 
 inexpensive material. Cost should be considered in the pur- 
 chase of supplies, but it is important that when paid for they 
 should be suited to their use. For example, if a contractor has 
 
PROTECTION OF METALS AGAINST CORROSION. 251 
 
 metal used for scaffolding and other false work which will be 
 frequently removed and erected and from which the paint will 
 be mechanically removed, so that it has to be repainted at fre- 
 quent intervals, a cheap paint is as good as any; the same is 
 true of all temporary structures; money may be saved in many 
 instances by buying cheap paint. But if the exposure is severe, 
 or if the structure is to receive little attention, it will be econom- 
 ical to buy a good paint. Bridges painted with good oil paints 
 require, unless very favorably situated, repainting every three to 
 five years; less often in a cold, arid country. If a better paint 
 will last ten years instead of five, we must consider that the cost 
 of the cheaper paint, which for convenience we will say is $i a 
 gallon, amounts to $2.75 in ten years, reckoning two paintings 
 and compound interest at 5 per cent. The equivalent of this 
 would be an enamel paint at a first cost of $1.86 per gallon to 
 last ten years. 
 
 Cost of Application. But we must not omit the cost of clean- 
 ing and repainting at the end of the first five years with the cheaper 
 paint, which could not be less than $i per gallon, and this addition 
 would make it proper to pay $2.71 per gallon for a ten-year paint, 
 as against $i a gallon for a five-year paint. The above figures 
 are assumed, merely to show the principle involved; in reality 
 the cost of oil paints will vary with the cost of materials from 
 75 cents to $1.50, and of varnishes and varnish paints from 
 $1.50 to $3, or more, and, as has been already stated, the cost of 
 cleaning and repainting may run up to $6 or $8 per gallon of 
 paint used. 
 
 Cost of Paint. Even the cheapest oil paints, those made of 
 iron oxides and graphites, cost something, more than most people 
 imagine. Linseed-oil varies in price from about 40 to 80 cents 
 per gallon, and some time ago when oil was at 56 cents, a fair 
 medium price, the writer went over this matter with the superin- 
 tendent of one of the largest and best paint-factories in the coun- 
 try, trying to get at the absolute minimum cost of such a paint. 
 In the first place, a gallon of paint contains about 6J Ibs. of oxide, 
 worth, say, pj cents, and 6J Ibs. of oil, which at 56 cents per 
 
252 TECHNOLOGY OF PAINT AND VARNISH. 
 
 gallon, is worth about 46 J cents, making 56 cents for material. 
 Now, if it is mixed in a paint-mixer, not ground through a mill, 
 as it ought to be, but as it is not usually, and is made in large 
 quantities, the cost of labor and power may be figured down to,, 
 perhaps, ij cents per gallon, without allowing anything for super- 
 vision; \ cent per gallon must be added for wear and tear; it 
 costs at least 2 cents per gallon for barrels, and i J cents to deliver 
 it f.o.b. in New York, making in all 5 cents per gallon. If to 
 this is made an allowance for superintendence, rent, insurance, 
 and interest on capital invested, at least 5 cents more must be 
 added, making the actual cost under the most favorable cir- 
 cumstances 66 cents per gallon. If it is to be put through a 
 mill, the cost of labor and power will be not less than 2 cents 
 per gallon additional, with another addition for superintendence, 
 etc., which would bring the cost up to 70 cents. But in any 
 manufacturing business there is more or less loss of material 
 and of time, and there must be also some little profit; and it 
 was the opinion of the expert that any man who attempted ta 
 sell a perfectly straight well-made oxide at 75 cents per gallon 
 would lose money. In the factory where he is superintendent, 
 it is necessary to grind certain cheap paints and deliver them,, 
 without packages, to another department of the same factory; 
 and it is customary to charge the second department i cent per 
 pound for grinding, which, in this case, would be 12^ cents per 
 gallon, which is the estimated actual cost; this substantially 
 agrees with the figures given. A large manufacturer in Canada, 
 where labor is cheaper than here, contracted to have his liquid 
 paints ground and put into the packages which he furnished 
 for 2 cents per pound for labor only, which would be 25 cents 
 per gallon on oxide paints; this was cheaper than he could do 
 it himself and proved to be too little to remunerate the con- 
 tractor. 
 
 The cost of a gallon of pure red-lead paint, very hastily and 
 imperfectly mixed (as it must be) just before using, cannot be 
 less than $1.50 per gallon, and probably is a good deal more 
 than that. The exact cost cannot be computed without know- 
 
PROTECTION OF METALS AGAINST CORROSION, 253 
 
 ing the amount of pigment used, in regard to which practice is 
 variable; but 20 Ibs. per gallon makes a very thin paint. The 
 cost may run up to $2 per gallon. This question of cost of paint 
 is of more importance than it might seem at first sight, for it 
 is evident that a very cheap paint is not what it is pretended 
 to be, and, if so, doubt is at once thrown on its whole value. 
 As a general rule, no really first-class goods can be made without 
 skilled labor, and the more skilled labor used, the greater will 
 be the cost. A thing is not good merely because it is expensive; 
 but if it is a thing which is capable of being made better by skill, 
 then the best of the sort cannot be cheap, and is yet likely to be 
 most economical in use. When paint is offered at less than 75 
 cents a gallon the price is against it, and it is easy to make a plain 
 oil and pigment paint which is honestly worth, from the factory 
 standpoint, $1.50 per gallon. 
 
 Spraying-machines. Paint is usually applied with a brush, 
 but within the last ten years a great deal of it has been put on 
 with spraying- machines, which operate with compressed air 
 and spray the paint over the surface. These work well on large 
 flat surfaces, but if used on bridge work or anything of that kind, 
 there is a considerable waste of paint caused by the narrowness 
 of the pieces to be painted; part of the paint floats off in the air 
 and is lost, and unless the paint is very cheap the loss of paint 
 makes up for the economy of labor, so that as a matter of fact 
 these machines are very little used on structural work. Their 
 principal use is in painting freight -cars; almost any one can hit 
 the side of a car if he stands near enough and a couple of men 
 can paint a car in three or four minutes. 
 
 There is difference of opinion as to the comparative merits 
 of machine and brush work. The advantage of the machine is that 
 the spray is carried along in a current of air and so penetrates 
 cracks and recesses which are inaccessible to the brush and it does 
 not skip anything; the most irregular surface is as well painted 
 as a plain one. The advantage of the brush is that the paint 
 may be rubbed with more force into the surface, and the universal 
 belief is that a paint well rubbed out is more durable than one 
 
254 TECHNOLOGY OF PAINT AND VARNISH. 
 
 less carefully applied. There is much difference in the quality 
 of work done with the brush. In the first place, there are differ- 
 ences in brushes. A cheap or worn-out brush containing not 
 enough bristlc-s does not absorb enough paint. In order to put 
 on a full, flowing coat the brush should be capable of holding 
 enough paint to act as a sort of reservoir, so that the end of the 
 brush which comes in actual contact with the surface will be 
 for a reasonable time amply supplied with paint and will not 
 drag and pull on the surface. With a dense, well-made brush, 
 .saturated with paint, the workman can spread and rub out the 
 paint without having it absorbed again by the brush. 
 
 Sometimes a skilful house-painter makes ,a poor job on 
 structural steel work for the reason that he has been accustomed 
 to rub out his paint very thin, so as to make an excessively thin, 
 smooth coat, and one which will dry quickly; whereas, the pri- 
 mary thing in this work is to put on a full, heavy coat, which will 
 afford protection to the metal, and while it is better to be smooth, 
 it is necessary that it should not be thin. House-painters, more- 
 over, find it hard to believe that a slow-drying elastic paint is 
 fit for any use and are possessed with a determination to improve 
 it by the addition of driers. In such a state of affairs about two 
 inspectors are needed to watch each painter. 
 
 Influence of the Weather. It is generally agreed that paint 
 should not be applied in wet or freezing weather, but one side 
 of a bridge is frequently shaded, and its temperature may be 
 less than that of the air, and if the latter is saturated with moist- 
 ure, or nearly so, the sunny side of the bridge may be dry and 
 in good condition to paint and the shaded side covered with 
 <lew. Similarly, bridges often span cool, dark ravines, and some- 
 times there are only a few hours in the middle of the day when 
 such a bridge is in the best condition to paint. So it appears that 
 besides proper cleaning of the structure and selection of the most 
 .suitable paint it is important and sometimes difficult to get the 
 paint put on in the best manner. Unless the metal in a structure 
 can be enclosed so as to keep the air away from it, it is probably 
 desirable to expose it to a free circulation, with the aim of keep- 
 
PROTECTION OF METALS AGAINST CORROSION. 255 
 
 ing it all as nearly as may be at the same temperature, so that no 
 part of it shall be so shaded or protected as to have its temperature 
 below the dew-point. 
 
 It should not be forgotten that strength, though essential, is 
 not the only desirable quality for a bridge. Rigidity is very 
 important and greatly promotes the preservation of the metal, 
 for if the bridge vibrates when a load passes over it, as many 
 highway bridges and some railway bridges do, the joints become 
 loosened, and if wet with rain or snow the water is mechanically 
 worked into the joints, the paint which was put there is broken 
 up and destroyed, and rusting is promoted in a decided manner. 
 
 Some engineers object to specifying the use of a particular 
 paint or other similar coating, the product of a single maker, 
 believing that this prevents competition in bids and results in 
 the. payment of a higher price than would otherwise be necessary. 
 They also seem apprehensive that such a course may injure their 
 reputation by the suggestion that they receive a commission from 
 the manufacturer. As to this latter point, the writer does not 
 believe there are many engineers whose characters are not good 
 enough to clear them from any such suspicion, and those who 
 cannot be indifferent to such a matter probably have not a great 
 deal of reputation to be damaged. An engineer or architect 
 should regard his employers' or clients' interests as though they 
 were his own, and if he thinks the best results are likely to be 
 obtained by using a particular paint or varnish, he ought to call 
 for it in his specifications; and the man who acts on that prin- 
 ciple can safely leave his reputation to take care of itself. 
 
 It is perfectly easy to get a competitive price. Let the engi- 
 neer, before writing his specification, ask the price from the 
 manufacturer; he can thus protect the contractor, for while the 
 manufacturer cannot guarantee the durability of his material, 
 which depends in great part on the preparation of the surface 
 and the care taken in applying the coating, he can always tell the 
 price. That is the only thing he can properly guarantee. There 
 are too many engineers, and some of them holding high positions, 
 who seem to think they are not doing their duty to their employers 
 
256 TECHNOLOGY OF PAINT AND VARNISH. 
 
 unless everybody they do business with loses money. No more 
 ruinous idea than this can be held. No business man wants to 
 do business with any one who is not making a profit and who 
 consequently has an incentive to give satisfaction. 
 
 Business Principles. Too many professional men are unedu- 
 cated in business and are ignorant of the principles by which it 
 is conducted, the most fundamental of which is that in any 
 legitimate business transaction both parties are benefited. Any 
 man who systematically attempts to buy supplies for less than 
 they are worth is thereby thrown into the hands of sharpers and 
 cheats, who try to satisfy him while giving him inferior material. 
 Perhaps it is not right to call them cheats, for our courts have 
 decided that a man who contracted for and paid for a turpentine 
 japan at less than the price of turpentine was not defrauded 
 when he received a benzine japan and could not recover pay- 
 ment, for it is assumed that he could not legally expect to buy a 
 thing for less than it cost. This was a famous and well-known 
 case; and the guilty man is the one who, in the first instance, 
 tries to perpetrate the fraud. The employers of such men deserve 
 whatever they get. 
 
 The engineer must make up his mind in some way that it 
 seems wise to use, on a particular structure, some special paint; 
 then he ought to specify that clearly, with the name and address 
 of the maker if possible, and let the contractor know at once 
 exactly what will be required. This tends to remove from the 
 latter a temptation to supply an inferior article and makes it far 
 easier to have proper inspection. If, in addition, the manufacturer 
 is notified and told who will buy the materials and the quantity 
 required, the chances are ten to one that he will make a special 
 test to see that they are not for any reason below the standard. 
 The maker takes far more interest in such an order than he does 
 in goods for miscellaneous trade, to be used he knows not by 
 whom, or how, or where. Fair and straightforward treatment 
 will always secure the interest and cordial co-operation of the 
 manufacturer. It is not straightforward to say that the paint 
 used shall be either of those made by Jones, by Brown, or by 
 
PROTECTION OF METALS AGAINST CORROSION. 257 
 
 Robinson, when everybody knows that Jones sells his paint at $i 
 a gallon, Brown at $1.25, and Robinson at $1.50. This is merely 
 an attempt on the part of an engineer to "save his face," as the 
 Chinese say; it deceives no one; it is undignified; it gains the 
 respect of none and forfeits that of many. On public works the 
 law sometimes requires such subterfuges, and then they may be 
 excusable; but the actual result of such restrictions is that in 
 the purchase of that class of supplies for which accurate descrip- 
 tive specifications cannot be written, some execrable materials 
 which would not be considered for a moment by any intelligent 
 private citizen have to be accepted. There is no part of our 
 public service which stands in greater need of reform than this 
 matter of purchasing supplies. 
 
CHAPTER XVI. 
 WATER-PIPE COATING. 
 
 THE engineers of water-supply are constantly in trouble on 
 account of the corrosion of the metal pipes used in conveying 
 water. Nearly all of these pipes are iron and almost all the 
 large pipes tare of cast iron. This metal does not rust as readily 
 as wrought iron or steel, and it is necessary to make it much 
 thicker than steel because of its inferior strength and greater 
 brittleness and also because it is liable to have thin or defective 
 spots, which is not the case with steel or iron pipe. It does not 
 therefore rust through, as a rule, as easily as the others. On the 
 other hand, it is not as tight, it is liable to leak at the joints, and 
 to be broken by the unequal settling of the earth about it, and 
 on account of its greater weight it costs more, at least in large 
 sizes, say above 4 feet in diameter. 
 
 Rusting of Cast Iron. Rust is, however, a very serious cause 
 of trouble with cast-iron pipe; it causes the surface to become 
 rough, and this interferes with the free flow of water. Cast iron 
 is not a homogeneous material, and rusting begins at spots where 
 the chemical action is most strongly induced, which may be due 
 to galvanic action due to the proximity of portions of different 
 composition, or often to the leakage to the pipe of an electric 
 current from an outside source. The spot becomes covered with 
 a mass of hydrated sesquioxide of iron, very bulky in proportion 
 to its weight (and its weight is two-thirds greater than that of the 
 iron which it contains), and this coating is believed to act cata- 
 lytically to induce further corrosion; at any rate, the spot soon 
 becomes covered with a nodule of rust, projecting an inch or two, 
 
 and sometimes much more, into the interior space; this not only 
 
 258 
 
WATER-PIPE COATING. 259 
 
 diminishes the cross-section of the opening, but, what is still 
 more important, sets up irregular and vortex currents which very 
 seriously affect the free ow of water through the pipe. 
 
 Diminished Flow. The rough surface thus produced also 
 serves for a foothold for algae and other vegetable growths, which 
 attach themselves to the wall of the pipe and float in the current 
 of water, from which they derive their sustenance, and to which 
 in some instances they impart taste and odor, the combined 
 result being that often the flow of water through a long water- 
 main is diminished 25 per cent., and sometimes 50 per cent, or 
 more. It is, therefore, desirable for more reasons than one to 
 prevent corrosion, even in cast-iron pipes; as for steel pipes, 
 these are so thin that comparatively little corrosion causes a leak,, 
 sometimes amounting to a serious failure of the pipe, and must 
 be prevented at any cost. 
 
 The R. Angus Smith Patent. What may be regarded as the 
 beginning of the modern practice of pipe- coating was the inven- 
 tion of Robert Angus Smith, Ph.D., F.C.S., a citizen of Man- 
 chester, England, and for a long time Secretary of the Literary 
 and Philosophical Society of Manchester. He was the author of 
 many scientific papers, and at the request of the society prepared 
 a Memoir of John Dalton, the eminent chemist, who was also a 
 member of that soceity. Dr. Smith (who was not a medical man, 
 but a scientific chemist and a physicist) was applied to for advice 
 in the matter of protecting the water-pipes laid down by the city 
 of Manchester between 1845 and 1850, probably because he was 
 the secretary and permanent executive officer of the society 
 before mentioned, which included many eminent technical and 
 scientific men of Manchester and neighboring cities. The result 
 of his investigations and experiments is set forth in the patent for 
 coating pipes which was issued to him October 19, 1848, and is 
 No. 12,291 of the British Patent Office. In the specifications 
 he says that "the coal-tar" (which was the principal ingredient, 
 in his estimation, of his coating) "is first to be reduced by dis- 
 tillation or otherwise, so as to obtain the product, which consists 
 of a thick pitch-like mass; this is to be kept at a temperature of 
 
260 TECHNOLOGY OF PAINT AND VARNISH. 
 
 300 F. (or such a temperature as will keep the matter fluid). 
 The pipes to be coated are first to have their interior surfaces 
 cleansed from oxide, so as to offer a clean metal surface, which I 
 prefer to coat over with linseed-oil. They are then to be heated 
 to 300 F. in a suitable stove, then immersed in the melted 
 coal-tar and remain there an hour." He also recommends the 
 addition of linseed-oil to the coal-tar to keep it of the proper con- 
 sistency; and although it is known that he also made various com- 
 pounds of coal-tar containing Burgundy pitch and other resinous 
 and oily substances, in this respect exactly agreeing with the prac- 
 tice of the varnish-makers of the time, it is clear that his primary 
 and essential compound was composed of coal-tar distilled until 
 it became a sort of artificial asphalt, which would not easily be 
 further changed by the action of air or water because it had lost 
 all its easily volatile constituents; this coal-tar pitch, the residue 
 of distillation at 300 F. or over, was brittle, and to make it 
 tough and elastic it was softened with linseed-oil; and this com- 
 pound of linseed-oil and coal-tar pitch was used either alone or 
 compounded with other oleo-resinous ingredients. The coal-tar 
 pitch was cheap, and its cheapness made it practicable to get 
 such a compound applied to low-priced material; and this, I 
 presume, was the occasion for his saying in his claim, "What I 
 claim is the coating of the interior of water-pipes by coal-tar by 
 the aid of heat." As a result (probably an unforeseen result) 
 of this wording of the claim it is legitimate for all users of a coal- 
 tar coating to call it the "Angus Smith Process," although we 
 cannot doubt that he would have unhesitatingly condemned the 
 current modern practice, both as to materials and mode of appli- 
 cation. 
 
 "The evil that men do lives after them; 
 The good is oft interred with their bones." 
 
 Let us note particularly some of the details of his process. In 
 the first place, he distilled the coal-tar until he got a pitch-like 
 residuum, which required a temperature of 300 F. or over to 
 keep it fluid. This is the hard pitch prepared for roofing-pitch 
 
WATER-PIPE COATING. 261 
 
 before the latter has been tempered with softening ingredients; 
 it is hard enough to be brittle when cold. 
 
 Pitch and Linseed-oil. This hard pitch can be compounded 
 with linseed-oil, which will not unite with liquid coal-tar; on this 
 point see the experiments of T. H. Wiggin in the Journal of the 
 Association of Engineering Societies (Boston), vol. 22. 
 
 A Clean Metal Surface. This compound of hard pitch and 
 linseed-oil was applied, not to an uncleaned pipe, but to a pipe 
 prepared by having "the interior surface cleaned" (not merely 
 from dirt and sand, but) "from oxide so as to offer a clean metal 
 surface"; there is no ambiguity about that. Dr. Smith was a 
 man distinguished for his literary and scientific attainments, and 
 knew exactly what his words meant. 
 
 Linseed-oil Coat. The inside of that pipe was pickled with 
 acid, and the "clean metal surface" was then coated with linseed- 
 oil, put in "a suitable stove," and baked at 300 F. Then it 
 was ready for the pitch and linseed-oil compound, in which it 
 was. immersed for "an hour" at 300 F.; then it was taken out 
 and the residual heat in the mass of the metal pipe baked it 
 on in a thin film. Note especially that the first coat of linseed- 
 oil was baked on, and that in this perfectly oxidized and hardened 
 condition it could not dissolve in the secondary coating, even when 
 immersed in it an hour. In another part of the patent specifica- 
 tion he advises that the hot pipe, when it has been removed from 
 the oil- and pitch-bath and partially drained, should be slushed 
 with linseed-oil, to help remove the excess of compound, and says 
 that part of this last application of oil will run back into the tank 
 and help to keep it properly tempered. 
 
 There is no doubt that pipe treated in this way will stand 
 service ; we can improve on the details, with our greater knowledge 
 and resources of materials, but we have not done it with cast-iron 
 pipe, nor has any such pipe been as well coated since his time. 
 
 Present Method. The current practice is thus described by 
 Mr. Wiggin, and as the pipe was made for the Metropolitan 
 Water Supply of Boston and vicinity, it was probably as good 
 as could be had in the country: 
 
262 TECHNOLOGY OF PAINT AND VARNISH. 
 
 "The inspector having passed judgment on the pipes, they 
 are rolled along down to the coating apparatus. The apparatus 
 consists of a number of ovens, with iron cars, on which the pipes 
 are rolled into the ovens and on which they stand during heating, 
 a vat or tank for the coating compound, a crane for hoisting 
 the pipes in and out of the vat, and various brushes, scrapers, 
 and mops for brushing out dirt and removing surplus coating 
 material. The coating material is crude gas-tar with sometimes 
 some dead oil of tar added. The pipes are given a fairly good 
 brushing before being put in the oven. The oven is merely an 
 enlarged chimney-flue, for all the smoke and gases of combustion 
 pass in at one end and out at another, so that a light but visible 
 deposit of soot is made on the pipes, which is not brushed off. 
 The old-fashioned ovens have simply a square hole through the 
 floor of the oven, connecting it with the fire, so that the hot gases, 
 and occasionally flame, act principally upon one portion of the 
 pipe, heating that portion very hot before materially affecting 
 the other portions. The newer ovens are fitted with an arched 
 bottom, with bricks left out at intervals all along the pipe, this 
 arrangement causing a more uniform temperature. The pipe 
 is left in the oven until the attendants think (no thermometer is 
 used) it is heated to about the correct temperature (48- in. pipes 
 are left in about twenty minutes); then it is put in the tar to 
 stay from a moment to ten minutes, according to the condition 
 of the work about the vat. On being removed from the vat, 
 the pipe is allowed to drain over the vat, and the drainage is 
 aided by scraping the invert with a segmental hoe, made to fit, 
 or at least to be of smaller radius than the pipe. The pipe is 
 then lifted out onto the skids and the coating smoothed up fur- 
 ther surplus tar removed and thin places reinforced by a 
 brush or mop. The brush is better because the mop leaves 
 part of itself behind on the pipe. The coating becomes hard 
 in from half an hour to two hours, according to conditions. 
 
 Kind of Tar Used. " Coal-tar varies very widely according 
 to the coal used and the temperature maintained in the manu- 
 facture of the gas. Furthermore, coal-tar varies at the different 
 
WATER-PIPE COATING. 263 
 
 heights in the tank in which it is collected at the gas-works. But 
 no tests are made to obtain any particular kind of tar for coatings. 
 The unrefined overflow from the hydraulic main of the gas- 
 plants is purchased where it can be obtained easiest and cheapest. 
 Specifications often call for deodorized tar, but the most notice- 
 able thing about coating-tar is its dense and pungent fumes 
 when heated. 
 
 "In summer tar is usually more fluid than molasses; in 
 winter it has often to be melted out of the barrels. This 
 crude tar cannot be used as a paint for cold surfaces, because 
 it will not harden; and tar from the coating- vat, though always 
 somewhat refined by the continued heating, does not harden 
 sufficiently when applied to cold surfaces. This suggests the 
 philosophy of the whole tar process of coating. By the heat 
 of the pipes the tar is distilled down to a compound which is 
 solid at atmospheric temperatures. A very favorable condition 
 for this volatilization of the liquefying constituents (which are 
 also the most volatile constituents) evidently exists when the 
 tar is exposed to the air, spread, as it is then, in a thin film over 
 the hot pipes; and that rapid volatilization takes place at this 
 time is indicated by the dense fumes given off. 
 
 Importance of Temperature. "As a corollary to the fore- 
 going, it follows that the temperature of the pipe, as it emerges 
 from the bath, is one vital factor in the character of the coating. 
 If the pipe is too hot, the coating is overdistilled and becomes 
 too brittle, or even may be reduced to an earthy, carbonaceous 
 residuum. If the pipe is too cool, a thicker coating is formed, 
 which will not harden sufficiently, will come off on the skids, 
 and will run in warm weather. 
 
 "At one foundry the pipes are often wittingly underheated on 
 days when strong north winds prevail, because the wind makes 
 it difficult to heat the ovens, and the day's work must be done 
 just the same. Again, pipes which stay in the oven during the 
 dinner half -hour are liable to go into the tank too hot, because 
 they are left in the oven too long and are not allowed to cool 
 down. The writer has often seen very hot pipes lowered into 
 
264 TECHNOLOGY OF PAINT AND VARNISH. 
 
 the tank, when they caused a violent boiling and much yellow 
 smoke (yellow smoke is the founder's sign of an excessively hot 
 pipe). An inspector said that at one foundry pipes hot enough 
 to set fire to the tar are so common that lids are rigged so that 
 they can be rapidly unhooked and allowed to fall over the tanks 
 and smother the flames. 
 
 "In general, the men fall into a certain routine of work, 
 so many pipes to brush out, so many to mop out, so many to 
 roll into the oven, etc., between dippings, and this routine fixes 
 the time of heating. A good dipman will not allow any notice- 
 able errors in temperature to pass, but he will not delay the 
 routine for minor errors. In other words, the application of 
 the method is inferior to the best judgment of the dipman. 
 
 " The character of the tar in the bath is another important 
 variable. New tar gives softer coatings, other things being equal, 
 because it contains more of the lighter constituents. Thick tar 
 gives thicker coatings than thin tar. Fresh tar requires a hotter 
 pipe than does old tar. Regularity in adding new tar would 
 give greater uniformity in coatings, but tar is often not in stock 
 when it is needed, and the dipman does not care much, so long 
 as the coating passes, and the inspectors do not usually pretend 
 to know much about coatings or to judge them very harshly. 
 
 Dead Oil. "Specifications often call for the use of dead oil 
 of coal-tar in the dip. The misconception is probably often 
 entertained that dead oil bears to tar-coating a relation similar 
 to that of linseed-oil in paint. A better comparison would be 
 that between dead oil in coal-tar and turpentine in paint. Dead 
 oil is of use principally to thin back the tar when it becomes 
 thicker than the dipman likes it. Ordinarily the necessary 
 adding of fresh tar is sufficient to keep the tar thin." 
 
 Such is the character of the coating for cast-iron pipes at 
 the present time. All the progress which has been made in the 
 last half century has been in the direction of cheapening the 
 material without regard to its quality, and of simplifying the 
 process so as to turn out a maximum amount of product with a 
 minimum of plant and labor. The result more than justifies 
 
WATER-PIPE COATING. 265 
 
 Mr. Wiggin's remark that "perhaps, if the truth were known, 
 the modern crude -tar coating would be found to be living on 
 the hard-earned reputation of the linseed-oil coating"; and 
 this is called the Angus Smith coating, though there can be no 
 doubt that if he were living he would condemn the whole thing 
 from beginning to end; in fact, though the use of his name may, 
 on account of the peculiar wording of his patent claim, be legally 
 justified by a- technicality, it is % unfair treatment of the name 
 of an able and careful man, amounting to breaking the seventh 
 and eighth commandments, by adulterating his invention and 
 stealing his reputation. 
 
 Coatings on cast-iron pipes serve sometimes another pur- 
 pose. Small sizes of pipe are thin, and if the iron is not of the 
 most suitable quality they are liable to be porous. An old 
 foundryman who practised for many years the manufacture of 
 small pipe, a man in whom I have the utmost confidence, says 
 that when he was making pipe it was all tested by hydraulic 
 pressure, and new pipe was very frequently leaky, by reason 
 of minute sand- holes. This was in Wisconsin, and gas- tar was 
 unknown at that time in that part of the country; so the pipe 
 was put in a bath of strong salt water for twelve hours and then 
 exposed to the air for a few days, when it was found to be per- 
 fectly tight, the openings having been closed with rust. Obvi- 
 ously a coal-tar dip would accomplish the same result. This is 
 in line with the current practice of shop-painting corrugated sheet 
 iron, which is often so full of pin-holes as to be unsalable unless 
 it is painted. The paint usually applied to corrugated iron is 
 more expensive than coal-tar, costing about twenty or twenty^five 
 cents per gallon. 
 
 Tar Not Used on Steel Pipe. It has always been recognized 
 that a coal-tar coating is not good enough to be of use on steel 
 riveted pipes, or on steel or iron welded pipes. Very large pipes 
 are usually made of steel plates rolled to the desired form and 
 riveted, the operation of making them being practically like 
 making the shell of a steam-boiler. These pipes are commonly 
 made up in three sheet sections, 25 to 30 feet long; these are 
 
266 TECHNOLOGY OF PAINT AND VARNISH. 
 
 coated and then are shipped to the point where they are to be 
 laid. The steel sheets are received at the shop in most cases 
 perfectly clean and free from dust, their surfaces being covered 
 with blue mill-scale very thin and adherent. When these are 
 passed through the bending-rolls they are of course put under a 
 strain, for sheets a quarter to a half inch in thickness do not bend 
 very easily, and this breaks loose all the scale which is at all dis- 
 posed to come off, so that even without pickling or sand-blasting 
 the surface is really in very good condition, not of course as good 
 as if entirely freed from scale, but much better than that of any 
 other structural work in its natural state. 
 
 Dipping in Asphaltum. These sections are then heated and 
 dipped into a vat of coating material, which is also hot; usually 
 this is a horizontal vat, and the pipe is rolled into it and rolled 
 over in it by means of chains which go around the pipe and which 
 form a sling for handling it; the pipe is then lifted from the vat, 
 not quite in a horizontal position, but with its axis inclined ten or 
 twenty degrees, and the surplus coating runs out of the interior 
 and off from the outside back into the tank. It is held thus over the 
 hot tank, the heat from which promotes the draining, until it ceases 
 to drip ; then it is removed and allowed to cool. The coating com- 
 pound is a soft asphaltum, made softer than its natural state by the 
 addition of mineral-oil residues of high boiling-point ; as this oily 
 matter gradually evaporates out it is replaced by further additions 
 from time to time. Much of this pipe-coating material is known 
 as maltha, and is separated from California petroleum as a residue 
 left in the retort after distilling off the more volatile portions of 
 the natural oil. The longer this process of distillation is carried 
 on the thicker and harder will be the residue; so the maker pre- 
 pares two kinds, one of which is perhaps a little too hard for use 
 by itself and the other much softer, and by mixing these the 
 dipman can get a compound of any desired degree of hardness. 
 
 Various Kinds of Asphaltum. Asphaltum is the name of 
 a class of minerals related to petroleum-oil, from which geolo- 
 gists think it is derived. Petroleum, according to Dana, passes by 
 insensible graduations into maltha, and the latter as insensibly 
 
WATER-PIPE COATING. 267 
 
 into solid bitumen; some of the solid asphalts, such as Trinidad, 
 while hard enough to be brittle when struck are soft enough to be 
 viscous and flow under long-continued pressure; the more fluid 
 of these cannot freely be made to unite with linseed-oil. From 
 these we gradually pass to gilsonite, a much harder substance, 
 which shows no viscosity at natural temperatures, but is yet 
 perfectly fusible and is called by mineralogists a resinous mineral 
 or a mineral resin. It is nearly free from mineral oily matter and 
 hence unites readily with vegetable oils ; and we may pass beyond 
 this to the mineral known as albertite, which is almost or quite 
 infusible and differs from bituminous coal chiefly in structure 
 and in the nature of the products of decomposition obtained 
 when it is subjected to intense heat. This latter does not soften 
 with oil and is of no interest in this connection. The semi-fluid 
 and tarlike bitumens are known by the name of maltha, an old 
 Greek name applied to these substances by Pliny, and still used 
 with that meaning; and, as has been said, it is also applied to 
 the bitumens artificially prepared from petroleum, especially the 
 dense and bitumen-bearing sort found in California. Maltha 
 greatly resembles in appearance coal-tar or coal-tar pitch, but is 
 very different in its chemical properties, and the one cannot be 
 substituted for the other. 
 
 Defects in This Coating. When pipe sections have been coated 
 in the way described, it will be easily understood that the com- 
 pound runs off more from that side of the pipe which chances to 
 be uppermost while the pipe is being held in its approximately 
 horizontal position to drain, and will be thickest on the opposite 
 side; alike on the interior and exterior of the pipe. Usually it 
 runs off until there is a thickness on the thin portions of ^ to 7 V 
 of an inch; on the thicker portions, it may be T V to J of an inch; 
 but it is not uncommon to find pipe sections with a thickness of 
 i or 2 ins. of coating along the side which was the bottom when 
 the pipe was draining. The compound is heated in the dipping- 
 tank to about 300 or 350 F., and the mineral oil, which is the 
 softening ingredient, constantly distils off, so that the composition 
 continually changes, and no two successive pipe sections are 
 
268 TECHNOLOGY OF PAINT AND VARNISH. 
 
 coated alike. When the mixture gets so viscid that it will not run 
 off the pipe with what the dipman regards as reasonable freedom, 
 he adds a barrel or so of thinning compound, and the next few 
 pipes get a coating as much too thin as that on the preceding ones 
 was too thick. The specifications usually say that the compound 
 shall be of such a nature that it shall not be brittle in cold weather 
 nor run or be sticky in hot weather; as a matter of fact, it is 
 brittle under a blow always, and in hot weather masses of it 
 weighing several pounds will slide off the outside; and on the 
 inside, where the pipe lies so that the thickest part of the coating 
 is at the top, it runs down in stalactitic forms, sometimes extend- 
 ing across the whole diameter of the pipe; and I know of places 
 where workmen had to be sent through the pipe to break out 
 these obstructions. Asphalt compounds of this sort are, at 
 ordinary temperatures, fairly hard to the touch, and if struck 
 with a hammer are more or less brittle, yet they yield to gentle 
 continued pressure. If they can be got into service without injury 
 they last a long time, because they are perfectly impervious to 
 water, and are only destroyed gradually from the surface, not all 
 at once throughout their whole thickness as a porous substance 
 would be ; and as they are buried in the earth and filled with 
 water they change temperature but little and that little with 
 almost inconceivable slowness, so that they do not crack with 
 changes of temperature. The thicker such a coating is the longer 
 it is likely to last after once it gets into service; but the thicker 
 it is the more difficult it is to handle during the three to six months, 
 or sometimes more, which elapse between the time of coating and 
 the testing of the line, after which it can be covered with earth. 
 Before that time it is subject to misuse of more sorts than the 
 inexperienced reader can imagine. 
 
 Handling of Pipe. Usually it is loaded on open railway-cars, 
 on which it is piled up, one section on the top of another, and the 
 rivet-heads dig holes in the coating; but sometimes this is in 
 part prevented by laying old rope or other packing material be- 
 tween the pipes. The posts on the sides of the car scrape off some 
 during transit; and when it arrives at the point of destination by 
 
WATER-PIPE COATING. 269 
 
 rail the pipe is rolled off the car without very much ceremony; 
 sometimes it rests on skids, sometimes on the ground. After it 
 has been there a few days or weeks, during which time boys pelt 
 it with stones and hammer it with cudgels to hear the pleasing 
 and resonant sound it emits, and play hide-and-seek in it, it is 
 loaded on farm wagons and hauled over country roads and across 
 fields, sometimes as far as fifteen miles, and dumped by the side 
 of the ditch on the gravel and loose stones which have been exca- 
 vated; then it is partly slid and partly lowered into the ditch. 
 There one might suppose it 
 
 "... sleeps well. 
 
 Malice domestic, foreign levy, nothing 
 Can touch him further." 
 
 Not yet. The sides of the ditch are covered with fresh earth, 
 poor walking in dry weather and banks of mud when it rains; 
 but the pipe lying in the ditch makes a beautiful asphalt walk, 
 and is used as such not only by the curious rustic and the casual 
 visitor but also by the entire gang of laborers going to and return- 
 ing from work. Thus a large part of the coating on the outside 
 of the top is removed; and if it is at all brittle, on cool mornings 
 the vibration from people walking over it cracks it off from the 
 inside of the upper segment. This kind of thing may be called 
 the "malice domestic." Then comes the "foreign levy" in the 
 shape of a gang of tramp riveters to do the field riveting. They 
 are armed with sledges, hammers, crowbars, and chisels; part 
 of them work inside the pipe and part on the outside. They wear 
 hob-nailed shoes; their sensibilities are not attuned to the high- 
 est pitch of refinement. The pipe had a good coating to start with 
 if there is much left on it when they get through. And over all 
 arches the clear blue sky, from which the July sun shines down, 
 and its heat is reflected from the yellow sides of the ditch, and is 
 absorbed by the black pipe until it is so hot that one cannot hold 
 the hand on it, and if the coating is at all viscous it softens and 
 slides off from the outside, and on the inside forms great tears 
 and stalactite shapes. Then it rains, and all the bare places, in- 
 side and out, get rusty. And the chief engineer objurgates and 
 
27 TECHNOLOGY OF PAINT AND VARNISH. 
 
 deplores, and when he wants sympathy has to look for it in the 
 dictionary. 
 
 Repairs. These defective places in the coating are repaired 
 by painting. Long before the experiments on paints and var- 
 nishes 'described ' in the previous chapter Were made, the water- 
 works engineers had found out that no reliance could be placed 
 on oil and pigment paints for hydraulic work; and the coating 
 most commonly applied is a sort of spirit varnish, made of the 
 same asphalt compound used in dipping the pipes, dissolved in 
 some volatile solvent either turpentine, benzine, or bisulphide of 
 carbon. All these form inflammable vapors which are explosive 
 when mixed with air, hence incandescent electric lights, the wires 
 of which are most carefully insulated, are the only source of light 
 which should be used; and as these vapors are unhealthful, and 
 that of carbon disulphide in particular is extremely poisonous, 
 the pipe should be ventilated by blowing a steady blast of air 
 through it from the direction from which the painters enter the 
 pipe, so as to blow against their backs and always carry the gases 
 from them. This is a precaution which should never for a 
 moment be omitted; men have lost their lives or become insane 
 from inhaling some of these gases. 
 
 If the varnish thus applied does not make a very thick coat, 
 two or three coats should be used; the more the better, for the 
 pipe will never again be so accessible. It is possible at this time 
 to use an elastic oleo-resinous varnish, one containing asphaltum, 
 and this is, in my judgment, the best thing to use, but it is slow 
 to dry unless a current of air is passing through the pipe, which 
 is often the case. Not less than two coats of such a varnish 
 should be used. On the outside of the pipe it is often possible 
 to apply some of the hot, melted compound, such as was used in 
 the dipping-vat; it may be melted by the side of the ditch in a 
 kettle and applied with a swab or brush, or sometimes poured on 
 from a ladle. 
 
 Corrugations. Pipes coated in this manner frequently, per- 
 haps I may say commonly, exhibit ridges and furrows occasioned 
 by the irregularities of flow of the compound while draining; the 
 
Laying Water-mains of 40- and 38-inch Steel Enamelled Pipe 
 
..ITY 
 
WATER-PIPE COATING. 
 
 271 
 
 accompanying illustrations show the character of these, both on 
 the outside and inside of the pipe. On the outside they do little 
 
 harm; on the inside they seriously diminish the flow of water by 
 causing eddies and irregular currents. 
 
272 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Vertical Dipping-tank. An attempt has been made to im- 
 prove on this method of dipping by using a vertical tank in which 
 the pipe section is. entirely immersed; it is then slowly lifted, end- 
 ways of course, and as the lower end of the pipe is in the liquid, 
 the cold air cannot get in, and so the compound does not chill, but 
 runs of! smoothly, from the inside; and this improvement makes 
 it possible to use a compound which has a much higher melting- 
 point than that used in the horizontal dipping-tank, which will in 
 consequence be unaffected by the heat of the sun. Such com- 
 pounds have been made ; I do not know their composition, but I 
 imagine from a rather hard asphalt, perhaps from "gilsonite 
 seconds," inferior gilsonite from that part of the deposit of 
 mineral which has been exposed to the weather, softened with a 
 very thick and heavy mineral lubricating oil from which all the 
 products except those of very high boiling-point have been dis- 
 tilled. These compounds have a considerable degree of tough- 
 ness even when quite cold, and stand transportation and rough 
 handling very much better than the ordinary coating, such as has 
 been described. The temperature of the dip is about 400 F., 
 and the compound sets and ceases to run on the outside of the 
 pipe while still far too hot to be touched by the hand ; it does not 
 flow off well from the exterior surface, and men stand around the 
 mouth of the tank when the pipe is being hoisted out with scrapers 
 and scrape off as much as they can from the surface back into 
 the tank. The compound sets so rapidly that it v is often possible 
 to see the marks of these scrapers on the finished pipe. I think 
 they are liable to scrape it off too closely, leaving too thin a coat- 
 ing on the outside. I have myself seen sections of such coated 
 pipe which had been exposed to the weather for a few weeks which 
 had considerable areas of coating so thin that in a favorable light 
 I could see the metal through the coating; and where the weather 
 had removed the elastic ingredient from the superficial layer I 
 could with my finger rub off all the coating and expose the clean 
 metal; the coating, being extremely thin, had become earthy and 
 friable, and could be easily rubbed off by friction. Of course 
 such a coating was no protection; but the inside of these same 
 
WATER-PIPE COATING. 273 
 
 pipes was well and uniformly coated and most of the outside had 
 a fair coat. A coating of this sort, if properly applied, ought to 
 give good service. Its principal defect, which it shares with the 
 asphalt dip previously described, is that the elastic ingredient is a 
 mineral oil which becomes lost by diffusion, and leaves the asphalt, 
 or rather the asphaltene part of the asphalt, in an earthy and fri- 
 able condition ; this action takes place from the surface and con- 
 sequently does not rapidly produce a decomposition of the coating 
 as a whole, but it- is progressive and is the principal cause of the 
 failure of asphalt coatings, which after a long time become earthy 
 and lose their coherence throughout and cease to afford protec- 
 tion; and long before they reach this stage the deterioration of 
 the surface makes it a suitable foothold for algae and other aquatic 
 growths. I suppose that a compound could be made of asphaltum 
 tempered with linseed-oil which would be much better, but it 
 would be costly and has never been attempted. 
 
 Varnish Enamels. The oldest varnish-makers and users of 
 whom we have any definite record, artisans of the tenth to the 
 fifteenth centuries, knew that varnish applied to metal and then 
 hardened by baking made a coating of great durability. This 
 probably was discovered by observing that the more elastic 
 varnishes are the more durable, and then that these varnishes, 
 which contain a large proportion of oil, are slow to dry, and 
 not very hard when they are dry. No doubt varnishes were in 
 those days much slower than are those of approximately the same 
 composition to-day, because they did not understand the refining 
 of oil as well as we do, nor was their knowledge of varnish-making 
 in its details to be compared with ours. But human nature 
 has been about the same, and when a knight got a new sword-hilt 
 he probably did not bring it in to be enamelled until the day 
 before the tournament, and had to have it back that same after- 
 noon. Thus the enameller, although he was ignorant of the fact 
 that the activity of the ions was augmented by an increase in 
 temperature, learned to observe that varnish dried more quickly 
 if exposed to heat, and he put the varnished hilt in the oven and 
 baked it for two or three hours, and everything was satisfactory. 
 
274 TECHNOLOGY OF PAINT AND VARNISH. 
 
 The materials were not very costly and the process was simple, 
 so that all sorts of small metal objects were treated in this way, 
 not only for ornament, but for common use; and the practical 
 details were well understood long before any one cared about 
 the theory of the matter. 
 
 The Rochester Pipe-line. Only small things were treated 
 in this way. When freshly varnished objects are put into an 
 oven the volatile solvent, turpentine or benzine, is quickly evapo- 
 rated, and this causes danger of fire; and this has the effect of 
 prohibiting such work on a large scale; but when, in 1893, I 
 was applied to by the authorities of the city of Rochester, N. Y., 
 for advice as to the best way of preserving their new water-main 
 from corrosion, I decided that this must be the process, and 
 that it must be so modified as to make it practicable. The pipe in 
 question was an intake from Hemlock Lake, and was for most 
 of its length a 38- in. steel riveted pipe; the coating was the com- 
 mon asphalt or maltha dip, and was not satisfactory, for the 
 reasons which have been indicated - in the foregoing account of 
 that process. It seemed to me that the best coating which could 
 be applied would be a true varnish enamel. While it was true 
 that fairly satisfactory results had been obtained on cast-iron 
 pipe by Dr. L. Angus Smith with a sort of an enamel of coal- 
 tar pitch and linseed-oil, this could not be depended on for steel 
 pipe, for the following reasons: 
 
 The R. Angus Smith Process Not Suited to Steel Pipe. In 
 the first place, the Smith coating was baked on by the residual 
 heat in the pipe after coming out of the dip; this could be done 
 because the weight of metal was very great, but steel pipe is thin 
 and does not hold much heat. Second, it was not a rational 
 method. As has been seen, the pipe was first dipped in pure oil, 
 then baked, then again dipped in an oil and pitch compound, 
 then rinsed off with oil, and the final baking was partly a process 
 of oxidizing the oil and partly hardening the pitch by evaporat- 
 ing its volatile constituents, which, however, could have been 
 present in only small amounts. The final result would, of course, 
 depend on the proportion of oil in the coating, which must have 
 
WATER-PIPE COATING. 275 
 
 been quite variable, and the thickness, and consequent rate of 
 cooling, of the pipe. The pipe was not coated with a definite 
 compound; and the oil and pitch were not united by cooking 
 together, as is the practice of the varnish- maker. Third, it 
 was expensive; the pipe practically had two coatings, one of 
 oil and one of the indeterminate mixture, and the results would 
 depend on the skill of the operator in a rather excessive degree. 
 Fourth, cast-iron pipe does not need such perfect protection 
 as steel pipe, as it is not so much inclined to rust and is much 
 thicker, and a coating which might answer for one would not 
 do for the other, as in fact was agreed by everybody, and the 
 modern coal-tar coating was not to be considered. But asphaltum 
 is a substance which can be had of a definite composition and 
 character, in any quantity desired, and it is greatly superior in 
 every way to coal-tar pitch; and if the pipe were baked in an 
 oven it could be exposed for any desirable period to any desired 
 temperature; hence we can not only temper the coating com- 
 pound with just enough oil to make it slightly tough, but can 
 put in all the oil we need to give it any desired degree of elasticity, 
 because we will leave the coated pipe in the oven until the coating 
 is perfectly and exactly oxidized. Besides all this, the coating thus 
 applied is thin and hence much less costly than it would be if as 
 thick as a common asphalt dip, so that in making such an enamel 
 we are not restricted by cost to asphaltum for a resinous ingredi- 
 ent, but can use in addition any other resins of low price, and 
 some of the low-priced varnish resins are of a high degree of 
 excellence in everything except color, and the oil can be properly 
 refined, and the compound made up according to the best knowl- 
 edge of the varnish-maker. 
 
 The Sabin Process. The danger of fire was avoided by 
 the simple means of leaving the turpentine or benzine out entirely; 
 the compound was of course thick and stiff at ordinary tem- 
 peratures, but by heating it in a tank to about 300 F. it be- 
 came fluid, and was applied by dipping the object to be coated 
 in it, precisely as though it were an asphalt or a coal-tar dip. 
 After dipping the pipe was at once put in a suitable oven and 
 
276 TECHNOLOGY OF PAINT AND VARNISH. 
 
 baked until the coating was properly oxidized. Of course, such 
 a compound and such a process were far more expensive than 
 the coal-tar dip as used on cast-iron pipes; but that had nothing 
 to do with the question. It was not excessively costly as com- 
 pared with a good asphalt dip, nor in fact very much more so; 
 and it was not a matter of stopping up sand-holes, nor of making 
 the pipe look as though it had been coated, but of securirg a 
 really adherent and preservative film which would endure toler- 
 ably well the unavoidable rough handling which sections of 
 water-pipe receive. About 14 miles of 38-in. steel pipe was 
 coated in this manner for this Rochester conduit, and the work 
 was done with remarkable uniformity. Considering the fact that 
 this was the first attempt to coat large work of any sort in this 
 way and that the apparatus and process of handling were in a 
 large degree experimental, the uniform and excellent results 
 obtained not only reflect credit on the operators but show that 
 the process must be in its nature reasonably simple and easy to- 
 conduct. The pipe sections were 28 feet long and weighed about 
 2 tons each, part of them 2\ tons; they were after coating trans- 
 ported on wagons to the place of use, the distance being in some 
 cases 14 miles, over very ordinary roads; and it was the general 
 opinion of all who saw the work that the coating stood the neces- 
 sary handling extremely well. Of course, the rivets of the field- 
 riveted joints had nothing on them, and their heat destroyed 
 the coating with which they came in immediate contact; but 
 these places were painted with an air-drying varnish of com- 
 position similar to that of the baked coating, as were also all 
 spots from which the coating had been abraded, which were, 
 however, very few and small; for not only does such a coating 
 stand hard usage well, but on account of its beauty and apparent 
 delicacy it actually gets much more careful treatment from the 
 workmen than does a coarser and rougher one. 
 
 Character of the Coating. A coating of this kind is hard 
 and elastic enough to stand a smart blow with a hammer with- 
 out injury, but anything can, by the application of sufficient 
 force, be scraped off any metallic surface. It is, however, a 
 

 
 l/N/y, 
 
Laying Water-mains of 40- and 6o-inch Steel Enamelled Pipe. 
 
WATER-PIPE COATING. 277 
 
 mistake to compare a pipe -line to a chain, whose strength is 
 that of its weakest link, and say that its protection is measured 
 by that of the least protected spot; if this were so, there would 
 be no water-pipes in use. 
 
 Corrosion is Local. As a matter of fact corrosion is not uniform 
 and general, but local; and if 99 per cent, of the surface is pro- 
 tected the durability of the pipe is probably increased at least 
 90 per cent. I have seen old pipe with practically no coating 
 removed from a bed of blue clay without the least rust on it ; but 
 we must remember that the coloring-matter of clay is iron, and 
 in blue clay it is in the ferrous condition, not saturated with oxygen ; 
 when we burn blue clay it becomes red because the iron in it 
 becomes more highly oxidized. Hence it is plain that blue clay 
 may act as a reducing agent, net as an oxidizing one, and tends 
 to abstract oxygen from anything with which it is in contact; 'and 
 it is well known that peat does the same thing. So it is that in 
 one place a pipe may tend to rust and in another it will be 
 preserved, independently of the effect of a coating; and the 
 fact that we cannot attain absolute perfection in a pipe coating is 
 no reason why we should not apply as good a protection as is 
 available. 
 
 The Allegheny and Cambridge Lines. Owing to the impor- 
 tance of the subject, the novelty of the method employed, and in 
 no small part the high reputation of the engineer in charge (Mr. 
 Emil Kuichling), this Rochester pipe-line attracted a great deal 
 of attention; and a similar coating was applied, the year after 
 this was finished, to the pipe-line at Allegheny, Pa., which was 
 nearly 10 miles in length and 5 feet in diameter, at the time, 
 I believe, the largest pipe-line in the world, and to a conduit in 
 Cambridge, Mass., about 4^ miles long and 40 inches in diameter. 
 The pipe sections at Cambridge were of about the same dimen- 
 sions as those at Rochester; for the Allegheny pipe they were only 
 25 feet long, but as they were 60 inches in diameter, and the steel 
 plate of which they were made was \ inch in thickness, they 
 weighed 5 tons each. The oven constructed for handling these 
 enormous pipes had a capacity of eight sections, and was divided 
 
278 TECHNOLOGY OF PAINT AND VARNISH. 
 
 into four parts, so that one part of the oven could be opened with- 
 out cooling off the other three. Two hours was required for 
 baking and about an hour was used in charging and emptying 
 the oven, so that eight pipe sections could be baked every three 
 hours, or the oven could be charged and emptied eight times in 
 twenty-four hours; or sixty-four sections a day, equal to 320 
 tons; and this was actually accomplished. When finished, the 
 pipes were tested by pounding them at intervals of a foot or two 
 with a J-in. steel rod, and if any of the coating could thus be 
 loosened it was rejected ; but it was necessary to recoat only a few 
 of these sections, perhaps a dozen out of the nearly 2000 which 
 were made. Since then this process has been applied to ordi- 
 nary small sizes of steam-pipe, for electric conduits, and other 
 uses, and I have seen J-in. pipe which had been coated bent 
 around a post into a coil with an internal diameter of about 8 
 inches, without cracking the coating, which was so hard that it 
 could not be scratched with the -thumb-nail; and in one estab- 
 lishment as high as 28,000 linear feet of pipe has been coated 
 per day. 
 
 Used in the U. S. Navy. Not long after the completion of 
 the work which has been described the Bureau of Construction 
 and Repair of the U. S. Navy Department built a coating plant 
 for using this compound, which by this time had become known 
 by the name of the Sabin compound (and the method as the 
 Sab in process), in the New York Navy Yard at Brooklyn. The 
 especial use to which the naval authorities put it is for the pro- 
 tection of fire-mains and flushing-mains on board ships. The 
 former of these in particular have been a source of a great deal 
 of trouble. Although made of heavy copper of the best quality 
 they rapidly corrode, not uniformly, but holes appear, the cor- 
 rosion taking place from the inside, which is filled with sea- 
 water under a pressure of 100 to 150 Ibs. to the square inch. 
 These pipes sometimes last only two months, rarely twelve, and 
 formerly had an average life of about six months. Since using 
 this coating they have lasted three and four years, and their 
 ultimate durability is not yet determined. This coating is, 
 
WATER-PIPE COATING. 279 
 
 consequently, specified on all war-ships ; and at most of the navy 
 yards and at several private yards plants for its application have 
 been constructed. 
 
 It may here be said that in 1903-4 the steel underfloors of the 
 roadways and sidewalks of the Williamsburg Bridge over the 
 East River in New York City were pickled and coated by this 
 process in a manner quite satisfactory to the engineers in charge, 
 and that this was the second lot of structural steel (except for 
 ship-building) to be pickled in this country; undoubtedly the 
 first to be pickled, dipped, and baked in any country. 
 
 The proper application of such a coating requires a film of 
 uniform thickness to be spread over the surface of the metal, and 
 that this should be oxidized to a certain normal point correspond- 
 ing to the complete and perfect oxidation of linseed-oil to linoxyn, 
 or "oil-rubber"; but the oxidation should not be carried beyond 
 this point, or the coating will lose its elasticity, and, if carried 
 much beyond it, its adhesiveness to the metal. In order to get 
 this uniform film, the object to be coated is thoroughly cleaned, 
 heated a few minutes in a hot oven, and dipped in the hot com- 
 pound. It is well known that all metallic surfaces have nor- 
 mally an adherent film of air, which is removed only with diffi- 
 culty, and the easiest way to break up this adhesion is to heat the 
 metal. The hot liquid, therefore, wets the hot metal much 
 more readily and perfectly than a cold liquid will wet a cold 
 metal; and as the heat is maintained for a considerable time the 
 liquid gradually crawls over any minute uncovered portions and 
 in this way a perfect and continuous contact between the metal 
 and the coating is established. This is promoted by the strong 
 capillary attraction which exists between the compound and the 
 surface of the metal, especially if the latter is iron or steel; much 
 less attraction seems to be manifested between the compound 
 and zinc, brass, or even copper, although the latter two are con- 
 stantly being coated at the Navy Yard plants. 
 
 Details of the Process. The object to be coated is left in the 
 dipping-tank two or three minutes, then taken out, held over it to 
 drain for a short time until the greater part has run off, but not 
 
280 TECHNOLOGY OF PAINT AND VARNISH. 
 
 until the compound appears to be thickening with cold, then put 
 in the hot oven. Ordinarily about twice as much compound will 
 adhere to the object as is need.ul to form the coating. The sur- 
 plus runs off and is caught in a convenient receptacle, from which 
 it is returned to the dipping-tank. If it were left in the oven it 
 would be wasted, and would, moreover, be carbonized and fill the 
 oven with smoke, to the injury of the coating. Commonly it takes 
 from fifteen minutes to half an hour for the surplus coating to run 
 off; and it is necessary that the oven should be hot to promote the 
 rapid and perfect drainage, for if any part of the coating is too 
 thick it will not be oxidized as soon as the rest and will make a 
 soft and imperfect spot in the coating. This is a matter of the 
 utmost importance; and it is, therefore, essential that the oven 
 should be uniformly heated and particularly that there should be 
 no leaks or crevices through which the cold air from without can 
 get in, for a jet of this cold air would infallibly make a bad spot 
 on the coating. The tendency of the hot air to get out and of 
 the cold air to enter is very strong, because at the temperature 
 of the oven, 400 F., the density of the outer air is twice that 
 of the hot air in the oven. After the coated object has been in 
 the oven about two hours it is done, and when removed and cooled 
 it is ready to be put in service. It is not to be forgotten that the 
 object of heating the oven is to increase the chemical activity of 
 the oxygen and of the oxidizable material, and that the same 
 results may be reached by baking at a lower temperature for a 
 longer time, or at a higher temperature for a short time. The 
 principal difficulty is in the matter of drainage; if the oven is not 
 fairly hot the drip does not run off properly, and if it is very hot 
 it may not be uniform. Some things can be coated and the excess 
 wiped off; wire, for example, after dipping can be drawn through 
 a hole in scraper which will allow only the exact amount needed 
 to go on into the oven, and I have in this way baked a good coating 
 on wire in twelve or fifteen minutes at a temperature of 500 to 
 600 F. This is rather delicate work, because it is necessary 
 to know exactly the temperature, and from previous experiments 
 exactly the time required, and remove the wire at just the right 
 
WATER-PIPE COATING. 281 
 
 time, or it will be overbaked and brittle. It could be easily done 
 on a large scale automatically. 
 
 The Dipping-tank. The dipping-tank may be a horizontal 
 trough or a vertical tank of cylindrical, oval, or other convenient 
 horizontal section; for coatir.g straight pipes nothing is better than 
 a vertical cylindrical tank, about a foot larger in diameter than 
 the pipe. If the pipe is not straight the tank may be made ova 1 , 
 or the lower part cylindrical and the upper part oval. Such a 
 tank will naturally be made of riveted steel and must be heated 
 by an external flue. It is impracticable to heat such a tank by 
 a steam-jacket or to heat any tank with a steam-coil; for by the 
 continual heating and cooling, rivets will get loose and leaky, and 
 the joints of a steam-coil, though when new they may be tight at 
 1000 Ibs. pressure, will in time leak a little; and a very slight 
 leakage of steam into the compound will in time destroy it. The 
 tank should never be exposed directly to the fire, but it may be 
 conveniently heated by a flue which intervenes between the fur- 
 nace and the chimney. The whole should be well insulated to 
 prevent radiation, and it is to be remembered that neither in the 
 dipping-tank nor the oven is there any evaporation of liquid, hence 
 very little fuel will be needed if proper insulation is secured. 
 
 Treatment of the Compound. The heating-flue should never 
 come up as high as the lowest level which will ever be reached by 
 the compound in the tank; if it does, the part of the shell of the 
 tank above the level of the liquid will be overheated, and as it is 
 alternately wet and dry as the level is disturbed in use, it will be 
 covered with thickened and overcooked compound, which will 
 from time to true be redissolved in the liquid, which is thereby 
 made thick and viscid, far more than would be supposed; for it 
 is a peculiarity of varnishes in general that an overcooked por- 
 tion of varnish continually grows thicker until it becomes a jelly, 
 and what is more remarkable, it imparts this property to fresh and 
 uninjured varnish to which it is added. In this way it acts exactly 
 as though it were a ferment. I do not suppose it is a ferment, 
 though some enzymotic ferments act under about as unlikely con- 
 ditions; but the chemical character of these charges is unknown. 
 
282 TECHNOLOGY OF PAINT AND VARNISH. 
 
 So far as I know, overcooked oil does not act in this way, but 
 only the compounds containing oil united with resinous matter. 
 An overcooked varnish may be thinned with spirits of turpentine, 
 and will keep growing thick, until an incredible amount of tur- 
 pentine has been added without avail; but turpentine is not neces- 
 sary, for this pipe compound does the same thing and there is no 
 turpentine in it. It is a strange thing, but it is true nevertheless, 
 and if the compound in a tank gets overcooked, all that can be 
 done is to throw it away and clean the tank out absolutely clean, 
 so that not a trace of the old compound is left in it, before refilling 
 it. If the compound is only a little thickened it may be thinned 
 with a properly made thinner, which is a similar compound made 
 with a large excess of oil; but this is a makeshift. The man in 
 charge of the work should be strongly impressed with the great 
 importance of not spoiling his compound by overheating it, which 
 he is most likely to do by trying to heat it from a cold condition 
 too quickly. It should be heated very gently; if there is a large 
 amount, the heating should be begun the day before it is to be 
 used. Of course, when the work is continuous from day to day 
 the heat is never allowed to go down altogether. But no amount 
 of care will avail if the heating-flue extends above the level of the 
 liquid in the tank. 
 
 Horizontal Tanks. Instead of using a vertical tank, horizon- 
 tal ones are in use in some of the navy-yard plants. These are 
 more convenient for dipping objects of irregular section, or with 
 projecting parts, as such things, after being heated in the oven, 
 may be laid in the tank and the hot compound poured with ladles 
 over the uncovered parts. It is, besides, possible to get along with 
 a less amount of compound in those tanks; and if made in the 
 way I shall describe, one end of the tank may be heated (for 
 coating small articles, such as pipe-fittings) and the rest of the 
 tank left cold. It is not a good plan to make such a tank of steel 
 plate and heat with a flue, unless it is for larger work than has 
 yet been done. It has recently been proposed to coat bridge mem- 
 bers in this way and very likely a horizontal steel tank might then 
 be the best; but for ordinary work a horizontal tank should be 
 
WATER-PIPE COATING. 283 
 
 made in cast-iron sections, each section being a short, wide, and 
 deep trough with open ends; the ends should be flanged, and the 
 sections should then be bolted together to make a long trough,, 
 the ultimate ends of which may be closed with plates bolted on. 
 Each of these sections should be cast with a steam-jacketed double 
 bottom, like a soap- kettle; and these should be separately piped, 
 each with its own independent inlet and outlet, for steam at 60 
 or 80 Ibs. pressure. These steam-jackets, being made of cast iron 
 without rivets, cannot leak into the compound, and it is impossible 
 to overheat the latter. Several of the sectional tanks have beea 
 built and are giving the greatest satisfaction. If only one section 
 is desired, a steel-plate diaphragm may be put in to divide the 
 compound in this section from the rest of the trough; as there is 
 no hydrostatic pressure there is no particular tendency for the 
 compound to leak by, and that in the rest of the tank remains un- 
 melted. The disadvantage of this kind of a tank is that it exposes 
 a large surface to the air and the compound tends to oxidize in 
 the tank; it is not as rapidly worked nor as convenient as a ver- 
 tical tank, especially for pipe ; only one piece can be dipped at a, 
 time, and in coating small pipe it is common to dip a hundred at 
 a time in a vertical tank; and it is more difficult to keep dirt out 
 of it. Everything which goes into an oven has to drip, conse- 
 quently most things have to be supported with their longer axis 
 vertical. Pipes can be baked in no other position, and so nearly 
 all ovens are vertical; if the tank is also vertical, the top of it may 
 be level with the top of the oven, which is in many ways conven- 
 ient. A pipe-coating plant should be built on a vertical plan 
 throughout if at all possible. 
 
 The Oven. The essential thing about the oven is that it 
 should contain pure hot air. The process is one of oxidation,, 
 and the carbonic-acid and other gases from the furnace should 
 not be allowed to enter, nor should the smoke and ashes; it 
 may be heated by an external or internal flue or flues, or the 
 air which it contains may be heated in an external stove and 
 forced into the oven with a blower. On very large work the 
 latter would be the best, as it would insure steadiness and uni- 
 
284 TECHNOLOGY OF PAINT AND VARNISH. 
 
 formity of heat. Further, the oven should be of such a shape 
 that the coated object can be supported in it, either by suspen- 
 sion or by resting on a grating in such a position that it will 
 drain quickly and uniformly; it mv.st be so tight that drafts of 
 cold air cannot enter; and the bottom of the oven must not be 
 heated, because the drip will fall on it drop by drop, and if it is 
 hot these drops will char and be destroyed and will fill the oven 
 with smoke. This drip must be caught in a removable drip- 
 pan, and by it run off into a convenient receptacle which can 
 from time to time be emptied into the tank. There must be some 
 means provided for varying the heat in the top and bottom of 
 the oven, so that if one part is too hot the heat may be partly 
 withdrawn and diverted to another. This may be effected by 
 having two or three entirely separate heating- flues : one, for exam- 
 ple, to heat the lower part of the oven, another for the middle 
 region, and a third for the upper portion. Or it is possible that 
 a single flue, surrounding the oven, with an outlet to the chimney 
 near the bottom and several separately controlled inlets at differ- 
 ent heights from the furnace, might be efficacious. It has also 
 been proposed to cause the air to circulate vertically in the oven 
 by withdrawing it from the bottom and blowing it in near the top 
 with a blower. Of course, if the air is heated with an external 
 flue and blown in it will be easy to arrange the heat as we choose. 
 Provision of some sort should always be made in an oven of 
 more than 12 ft. in height for local heating. 
 
 The common and very satisfactory kind of oven for pipe- 
 work consists of a steel cylinder, not less than i ft. larger in diam- 
 eter and 2 ft. greater in length than the largest pipe which is 
 to be put in it, securely set up in a vertical position, and sur- 
 rounded with a 1 6- or 2o-in. brick casing, to keep the heat in. 
 Between the steel shell and the brick wall is a space of 6 ins. to 
 i ft. in width all around, as a flue for the products of combus- 
 tion from a neighboring furnace on their way to the chimney. 
 This flue envelops the steel shell from top to bottom (but does not 
 extend under the bottom of the oven) and may be divided by one 
 or two horizontal annular partitions into two or three independent 
 
WATER-PIPE COATING. 285 
 
 flues. The top of the oven is covered with a light cover, usually 
 made of sheet iron backed with a layer or two of asbestos-paper, 
 and then with inch-boards; the cover keeps the heat in, and 
 can be easily lifted off by a couple of men when it is time to 
 remove or put in pipe. A gallery for these men to walk on is 
 provided, a couple of feet lower than the top of the oven, and 
 this may extend to and around the top of the dipping-tank, if 
 the latter is of the vertical type. If more than one section of 
 pipe is to be coated at once, as many of these ovens as are de- 
 sired may be built together in the same mass of brickwork; 
 each steel shell may be made large enough to take in not more 
 than two large pipe-sections at a time. If the units are made 
 larger than this trouble will be experienced on account of the 
 escape of great quantities of hot air whenever the oven is opened 
 to take out or put in a pipe. 
 
 The dipping-tank and oven must be inclosed in a well-lighted, 
 substantial building which can be heated in winter to a tempera- 
 ture of not less than 60; for if the pipe is taken out of the dipping- 
 tank into cold air or into a wind of even warm summer air the 
 compound on it will be chilled and will stop running off; three 
 or four times as much as is proper will be carried over into the 
 oven, and before it gets off some of it will have begun to set 
 from the heat and chemical action, and then it never will run off, 
 and the pipe will be unevenly coated. It is therefore impor- 
 tant to have the whole apparatus inclosed in a building. And if 
 the pipe is to be lowered down into the oven from the top, it is 
 clear that the building must be somewhat more than twice as 
 high as the oven, and some kind of hoisting apparatus must be 
 provided; an electric crane is probably the best if much work 
 is to be done, but a derrick with a swinging-boom has been used, 
 also a trolley, and for occasional use still simpler apparatus has 
 been made to answer. The height of the building may be some- 
 times lessened by sinking the ovens and dipping-tank below 
 the level of the floor. If this is done a blower, made especially for 
 hot air, such as is used instead of a chimney to induce draft, 
 may be used to force the hot flue gases from the furnace to the 
 
286 
 
 TECHNOLOGY OF PAINT AND VARNISH. 
 
 Enamelling-plant, Sabin Process. 
 
WATER-PIPE COATING. 
 
 287 
 
 GROUND 
 
 LINE 
 
 
 CONCRETE CONCRETE 
 
 VERTICAL SECTION 
 
 PLAN 
 
 Enamelling-plant, Sabin Process. 
 
288 TECHNOLOGY OF PAINT AND VARNISH. 
 
 oven; in some situations it is possible to build on a side hill 
 and excavate on one side. This is an almost ideal state of things. 
 Ovens opening from the side, with a door like a closet, have 
 been built. They have so far been not very successful. The 
 trouble is that there is leakage around the door, no matter how 
 carefully it is made, and that side of the oven is cooler than the 
 others. An oven is now in process of construction on this plan, 
 but is built with a sort of vestibule, so that leakage into or out 
 of the oven is into a little room intermediate between the outer 
 air and the oven; this ought to be more successful. 
 
 EnameUing-ovens have been built which consisted simply of 
 brick rooms heated by iron pipes which passed through the 
 room and radiated heat which was supplied by the furnace gases 
 passing through these pipes; this is a very simple and efficient 
 form; if carefully made, it should be susceptible of the most 
 exact adjustment of temperature. This style of oven has been 
 used for such things as bicycle frames and the like, never for 
 very large work. 
 
 In any oven it is important to have thermometers. Nothing 
 is equal to a good mercurial thermometer within the limits of 
 its range, and they can now be had with nitrogen over the mer- 
 cury, instead of a mercurial vacuum, which can be depended 
 on to 800 F. 
 
 Thermometric Readings. Any mercurial thermometer has 
 range enough, if constructed for the purpose with a long stem, 
 for this varnish enamel work. Two or three tubes of common 
 steam-pipe should penetrate through the brick wall, the flue, 
 the iron shell, and enter an inch or two into the oven; thermometers 
 attached to a rod can be pushed in as far as these pipes go, and 
 the outer ends of the pipes plugged with a handful of fibrous 
 asbestos; from time to time a thermometer may be drawn out 
 and read. A thermometer may also be lowered from the top 
 with a wire. It must be remembered that the temperature indi- 
 cated by the thermometer may not be the actual temperature 
 of the greater part of the oven; the thermometer may be in an 
 under- or over-heated place, but since it is always the same place, 
 
WATER-PIPE COATING. 289 
 
 it is sufficient. The operator finds that when the thermometer 
 gives certain readings the baking is successful, and then he always 
 tries to keep the temperature at these standards. The apparent 
 temperatures of different ovens, doing practically the same work, 
 are usually different ; the real average temperature must be about 
 the same. When the plant is properly constructed almost the 
 whole thing is a matter of temperature. 
 
CHAPTER XVII. 
 
 SHIPS'-BOTTOM PAINTS. 
 
 THERE are several species of aquatic animals which bore 
 holes in unprotected submerged wood, and are particularly dan- 
 gerous to the bottoms of wooden ships. To protect ships from 
 these the practice arose of covering the exterior of the ship below 
 the water-line with sheets of copper, as a sort of armor-plate 
 against aquatic enemies. It was found that not only did the 
 copper protect from the teredo, but that barnacles and other 
 organisms did not adhere to it, and this was a great advantage, 
 because frequently these growths were several inches in thickness, 
 and impeded the rapid progress of the ship through the water. 
 A coppered bottom is, in fact, very efficacious at first ; it does not 
 appear that it is actively poisonous to barnacles and the like, but 
 that it has a laminated structure, probably from having been 
 rolled, and under the action of sea-water the exterior laminae 
 scale off, and of course any marine growth attached falls off with 
 the scale of copper. 
 
 Exfoliation Said to be Superficial. It is said that this lamina- 
 tion is most marked near the outside of the copper sheet, and 
 that the middle part (in thickness) of the sheet is of more homo- 
 geneous, unstratified metal; so that after a few years the laminated 
 part wears off, and then the copper ceases to exfoliate, and the 
 barnacles and other things grow as well on the copper as they 
 would on anything else. 
 
 When iron ships came into use the danger from the teredo 
 disappeared, but the loss of speed consequent on fouling with 
 barnacles, weeds, etc., was as serious as ever; and as the speed 
 of steamships increases the objection to fouling is greater. Chief 
 
 290 
 
SHIPS'-BOTTOM PAINTS. 291 
 
 Constructor Bowles is authority for the statement "that while 
 the fouling of the battleship Indiana between her launching and 
 trial was very slight, it was sufficient to make a difference to the 
 builders of $100,000 in the premium earned for speed. It probably 
 increased the resistance of the ship about 15 per cent. A ship 
 subject to ordinary service, staying in port about half the time, 
 will foul so rapidly that in from six to nine months there will be 
 a loss of speed of from 25 to 40 per cent.; where ships are running 
 rapidly and regularly the loss is less." (Trans. Am. Soc. C. E., 
 Vol. XXXVT, p. 494.) The prevention of fouling of iron and 
 steel ships is therefore a matter of great and practical importance; 
 and as this is attempted almost entirely by painting, it is proper 
 to give the subject consideration here. 
 
 I say almost entirely; for if we attach plates of copper to the 
 outside of a steel ship, as soon as the sea- water gets in between 
 the two, as it is sure to do, galvanic action sets up and the steel 
 is rapidly corroded. 
 
 Wood Sheathing. It has been thought that if there were no 
 metallic connection between the steel and copper this action could 
 not take place; so in many cases the outside of the ship has been 
 sheathed with 3 or 4 ins. of wood, in the form of planks bolted 
 on, and the copper sheathing attached to the wood. This has 
 not been successful because the wood becomes water-soaked, and 
 thus a galvanic couple is formed. It has always seemed to me 
 that this method might be made far more successful by kiln- 
 drying the wood, then soaking it for a day or two in melted paraffin, 
 until the latter had penetrated the planks to the centre. 
 During this treatment they would shrink 10 per cent. ; then if they 
 were applied and closely fitted on, and all interstices filled with 
 melted paraffin or some similar material, the water never could 
 get in to do any damage. Of course it would cost money, but 
 the relative cost would not be so very much more, and if it were 
 efficient, and the other way is not, it would be the way to do it. 
 There would still be the objection that copper sheets^ cease to 
 exfoliate after two or three years and would have to be torn off 
 and replaced; but the planking would not need renewal. If a 
 
292 TECHNOLOGY OF PAINT AND VARNISH. 
 
 ship can be kept really clean by recoppering every two years, or 
 perhaps three, without any other trouble, it might be worth con- 
 sidering. 
 
 Electroplating the ship with copper has been unsuccessfully 
 tried. Electroplate, if of considerable thickness, is a spongy 
 deposit, and does not answer. 
 
 Paint, then, is practically the universal means of protecting 
 ships' bottoms. All sorts of nostrums have been tried for the 
 purpose. The vagaries of inventors are infinite and unaccountable, 
 but none are quite so absurd as some of the patented preparations 
 which have been not designed (they couldn't have been 
 designed) put together to sell to the seafaring man. Here is a 
 sample : 
 
 A Sample Patent. "I take 100 Ibs. of rosin-oil, 100 Ibs. of 
 black lead, 50 Ibs. of French chalk, 50 Ibs. of white zinc, 75 Ibs. 
 of oxide of iron, and 25 Ibs. of tallow. These ingredients are 
 thoroughly mixed. I then heat together 125 Ibs. of thick tur- 
 pentine, 50 Ibs. of linseed-oil, 125 Ibs. of common rosin, 25 Ibs. 
 of Gallipoli oil, and 125 Ibs. of tallow; and when the mixture is 
 cold I mix with it 25 Ibs. of shellac dissolved in 50 Ibs. of alcohol 
 or naphtha. I then add to the mixture 50 Ibs. of Venetian red, 
 125 Ibs. of zinc paint, and thoroughly mix the ingredients. I then 
 add to the mixture 50 Ibs. of tar-spirit and again thoroughly stir 
 the mixture. The two compositions thus formed are then thor- 
 oughly mixed and the paint is ready for the market. " 
 
 This mixture was patented by an Englishman, both in Eng- 
 land and America; and while it is more elaborate than most it 
 can hardly be said to be more absurd or less efficacious. 
 
 Practically there are now in general use three kinds of ships'- 
 bottom paints. All require a first coal, which is essentially the 
 same in all cases, being a quick-drying spirit varnish. This is said 
 to prevent rusting, and is called the anti-corrosive coating as 
 distinguished from the second or anti-fouling coating. 
 
 Copper-oxide Paint. In the first class of these anti-fouling 
 
 faints the pigment is oxide of copper, which is claimed to be 
 
 poisonous. This is mixed with a varnish similar to that used with 
 
SHIPS'-BOTTOM PAINTS. 295 
 
 the anti-corrosive paint, which latter has commonly an oxide of 
 iron as its pigment. I am told that 6,000,000 Ibs. of copper scale 
 (oxide) are annually used for this purpose in the United States. 
 The efficacy of this class of paints is a matter of dispute. I believe 
 that neither the navy or any of the more important steamship 
 lines use these paints, whose most undeniable merit is the 
 moderate price at which they may be sold. Their very great 
 sale, on the other hand, may be taken as clear proof that they 
 are not worthless. I have had no personal experience with them, 
 my own experiments having been along a different line, as will 
 be told later. 
 
 The Varnish Used. The varnish used in these paints con- 
 tains little or no oil, but is made of a cheap grade of Kauri or 
 some similar resin dissolved in benzole or some solvent of which 
 benzole is a considerable ingredient, some cheap grade of coal- 
 tar naphtha, mixed probably with a little benzine, and sometimes 
 with a little wood-alcohol and fusel-oil. As they are used in the 
 open air the odor of these liquids is not particularly objectionable; 
 and it would make no difference if it were, for an oleo-resinous- 
 varnish is not good for such service, and it is necessary to use a 
 solvent which will dissolve a suitable resin. Paints of this sort 
 dry in an hour or two, so that the second coat may be applied 
 almost immediately. 
 
 It is not impossible that the resin itself is repellent to the 
 organic growths, at least in some degree. I know of at least one 
 very successful maker of this kind of paint who believes that the 
 copper oxide he uses is chiefly valuable as a selling feature and 
 that the varnish, which is of a peculiar kind, is what keeps the 
 barnacles off. There may be something in this. I am certain 
 that the common buffalo- moth can be kept out of rugs by var- 
 nishing the floor on which the rug is laid, two or three times a 
 year with a good Kauri varnish; and some other insects, equally 
 objectionable, will not come into a house, the entire woodwork of 
 which is kept well varnished. We know that these oleo- resinous 
 varnishes continue to harden for a year or more, which shows 
 that some slow chemical action is going on, and although we can 
 
294 TECHNOLOGY OF PAINT AND VARNISH. 
 
 detect no odor it must be that something objectionable to the more 
 acute sensations of insects is being given off. I have no doubt 
 about this, although I do not understand what takes place. But 
 if this is so, it may be possible that the right kind of a varnish 
 may prevent the adhesion of marine growths to the bottom of a 
 vessel. It is all a question of evidence, and I am not aware that 
 a sufficient amount of evidence is accessible. 
 
 Poisonous Ingredients. The same kind of a varnish is used 
 with the second sort of paint, but the pigment is usually iron 
 oxide or something of the kind, to which has been added from half 
 , a pound to a pound per gallon of some mercury compound. Some 
 makers claim to use oxide of mercury, others chloride; probably 
 it makes little difference, as it is converted into the extremely 
 poisonous bichloride of mercury (corrosive sublimate) by the 
 action of sea-water. This, of course, kills anything which tries 
 to adhere to its surface; and as the varnish is gradually worn off 
 fresh supplies of poison are exposed, until the anti- fouling coat 
 is practically gone. Arsenic does not seem to be efficacious ; mer- 
 cury is practically the only poison in use. Paints of this sort, if 
 well made, are very satisfactory; but they are expensive, and of 
 course have to be renewed frequently. The rule in the navy is 
 to repaint the bottoms of ships every six months. The time varies 
 according to the kind of service, the temperature of the water, and 
 many other things; the same paint will seldom give similar results 
 twice on the same boat. 
 
 Copper-soap Paint. The third kind of paint is of an entirely 
 different nature. It is essentially a copper soap, made by precipi- 
 tating a common soda soap from solution by adding a solution of 
 sulphate of copper, making a stearate or oleate of copper; with 
 this is probably mixed some tallow or other grease. The mixture 
 is made liquid by heat and is applied in a melted condition with 
 brushes, exactly as melted wax was used on ships' bottoms two 
 thousand years ago, as described by Pliny. This paint is applied 
 in a rather thick layer, about ^ in. in thickness, and is slowly 
 worn off by the action of the water as the boat moves rapidly 
 through it. Its action is therefore similar to the exfoliation of 
 
SHIPS'-BOTTOM PAINTS. 295 
 
 copper, and is quite effectual. It is claimed by those who sell it 
 that the bottom of the boat is by its use rendered slimy, and thus 
 the friction is decreased; but it is to be noticed that racing yachts 
 use a hard varnish, which may fairly be taken as a demonstration 
 that the soap paint has no superiority in that respect, though it 
 certainly does seem to be very smooth. 
 
 In 1900 I prepared carefully thirty plates painted with various 
 anti-fouling coatings, which it had been determined by previous 
 experiments to investigate. These consisted of (i) an oleo-resinous 
 varnish, containing rather more than 30 gals, of oil to each 100 
 Ibs. of Kauri resin; (2) a spirit varnish made by dissolving Manila 
 resin in a suitable solvent; (3) a similar varnish, made from a 
 more easily dissolved resin than Manila, but otherwise much like 
 it; (4) shellac, in alcohol; and (5) a rather complex varnish con- 
 taining a proportion of shellac, and also oil. The second, third, 
 and fourth of these were also used with the addition of various 
 fixed oils : linseed, tong, and castor. All were made into paints by 
 adding a neutral pigment, unacted on by the varnish or sea- water ; 
 and each was tried with the addition of a mercury compound and 
 also (separately) with arsenic. Some of the latter trials were 
 duplicated, using in one case powdered metallic arsenic and in 
 the other white arsenious acid. Some of the mercury tests were 
 in triplicate, using i lb., i lb., and i Ib. of mercury to the gallon 
 of paint. Besides these were half a dozen special paints, one of 
 which (for purposes of comparison), was a well-known proprie- 
 tary ships '-bottom paint of excellent quality. The result may be 
 briefly told. The oleo-resinous varnish made a very fair paint, 
 but was soft and would have been easily scraped off; the Manila 
 varnish was hard, and with the addition of a little oil was a good 
 paint; the other, more soluble copal, was not as good as Manila; 
 the shellac went to pieces; so did the special paints; but No. 5, 
 which was a mixed varnish, gave the best results of all, a little 
 better than the standard proprietary paint, indicating that a little 
 shellac and a very little wax are useful additions to such a paint. 
 Kauri was the best resin; mercury was much better than arsenic; 
 and a considerable proportion of mercury is desirable. The best 
 
296 TECHNOLOGY OF PAINT AND VARNISH. 
 
 paints were, unfortunately, the most expensive, and none of them 
 showed much durability after a year's exposure; some were nearly 
 destroyed before that time. No experiments in this series were 
 made with the copper soap or grease paints, nor with copper oxide. 
 It seemed possible to make a somewhat better mercury paint than 
 is now in use, but not a great deal better; and the difficulty of 
 carrying on these experiments is prodigious. 
 
 In conclusion it may be added that some of the yachtsmen, to 
 whom expense is not an objection, varnish the bottoms of their 
 vessels, sometimes with spar varnish and sometimes with a spirit 
 varnish, and while the surface is tacky rub it over (with a brush) 
 with copper-bronze powder; and this is said to be very excellent- 
 Often the bronze powder is mixed with the varnish before the 
 latter is applied. Racing yachts usually receive nothing but var- 
 nish, or a thin varnish paint, applied a day or two before the 
 race. Probably no other surface offers so little friction as that of 
 a clear, well-dried varnish. 
 
CHAPTER XVIII. 
 
 SHIP- AND BOAT-PAINTING. 
 
 WITH a few exceptions the methods and materials used in 
 house-painting are applicable to ships and boats, the most 
 remarkable difference being in painting the outside of pleasure- 
 craft, which are commonly white. This color gives a cool and 
 agreeable effect; but as these vessels spend much of their time 
 in harbor, and as harbor-waters are frequently covered with a 
 black, slimy, oily film, they quickly become foul, and are then 
 anything but pleasing to the eye. The remedy for this state of 
 things is one which, from a painter's viewpoint, may fairly be 
 called heroic. 
 
 White Paint for Boats. To keep them white, they are painted 
 with white lead, mixed not with oil but with spirit of turpentine. 
 Paste white lead, containing 10 per cent, of oil, is mixed up with 
 turpentine, and after standing overnight to settle, the turpentine 
 is poured off; this removes about half of the oil. The residue 
 is then mixed with fresh turpentine, and the boat painted with 
 it. In this way is obtained a coating of unparalleled whiteness, 
 for the yellowish tint of ordinary white paint is due to the oil it 
 contains; but paint made in this way is necessarily lacking in 
 binding material. It therefore washes off easily, and thus exposes 
 a fresh surface. As it dries with great rapidity, owing to the small 
 amount of oil it contains, and the excessive thinness of film which 
 this oil has, it is possible to apply many coats in rapid succession, 
 thus building up a thick coat of paint; and as there is nothing 
 about it which has a natural affinity for water it does not become 
 water- soaked and all come off at once from the surface to which 
 it was applied, but gradually wastes away from the outside, or 
 
 297 
 
298 TECHNOLOGY OF PAINT AND VARNISH. 
 
 if necessary, may be cleaned off with scrubbing-brushes, thus 
 always presenting a white surface of great purity. This, of course, 
 means frequent repainting and a use of material which would in 
 other cases be considered wasteful; but in no other way can the 
 results be obtained. 
 
 On deck the conditions are very different. The deck-houses 
 are sometimes painted, and this should be done with enamel 
 paints, made with the most durable and elastic varnishes, say 
 25 to 30 gals, of oil to 100 Ibs. of (unmelted) resin; the interior 
 of the cabins and other rooms with a somewhat harder and 
 quicker- dry ing enamel. 
 
 Spar Varnish. Some of the exterior woodwork, frequently 
 a large part of it, is left unpainted and is protected by "spar" 
 varnish; this varnished but unpainted wood is called, on ship- 
 board, "bright work." The masts are sometimes, but not com- 
 monly, painted, and the spars are left "bright." Spar varnish 
 is used on these, and this is the origin of the name. Spar var- 
 nish is a very durable and elastic varnish, pale in color though 
 not excessively so, for a yellow varnish looks well on spruce, 
 and dark varnishes are much better than pale ones on mahogany 
 and such woods, and should contain not less than 25 gals, of oil 
 to 100 Ibs. of resin. It is in fact very much such a varnish 
 as is used for a finishing coat on carriages, except that it must 
 dry more quickly. If a boat could be built in a shop and var- 
 nished in a room free from dust, carriage-finishing varnish would 
 be better than spar; but in practice the quicker-drying varnish is 
 the better. It is frequently a more fluid, or thinner, varnish than 
 such as are made for shop work. This tends to make a thinner 
 film, which is less durable, but is quicker to dry; and as most 
 spar varnish is used on repair work, it is absolutely necessary 
 that it should dry quickly. It is even the practice in some of the 
 best yards to thin it with spirit of turpentine for very hurried 
 work; and this is better than adding drier, though, of course, it 
 makes a still thinner and more perishable coating than the regu- 
 lar spar. Sometimes spar varnish is applied to the unfilled wood, 
 and repeated coats used until a sufficient body has been built 
 
SHIP- AND BOAT-PAINTING. 299 
 
 up, and this is the best practice; in this way the wood is pro- 
 tected by a homogeneous coating which no severity of exposure 
 can cause to separate^ but often a cheaper varnish is used for 
 the under-coat work. This should be similar in its nature to spar; 
 rubbing-varnish is not fit for this, and worst of all is shellac. 
 The latter is often used because of its excessive rapidity of dry- 
 ing; but as has been already stated, this rapidity is partly only 
 apparent; and at any rate shellac is not a varnish which ought 
 to be exposed to the hot sun, nor to sea- water, and not infre- 
 quently causes blisters under the spar varnish which is subse- 
 quently applied. 
 
 Shellac. There is a legitimate use for shellac on board ship. 
 Some of the decks, not exposed to the weather, but those which 
 serve as floors, must be scrubbed clean daily; and as it is mani- 
 festly impossible to use a slow- dry ing varnish on these, the best 
 thing is a thin shellac, one coat of which will dry almost imme- 
 diately, and will answer, for a day or two, to prevent grease and 
 dirt from penetrating the wood. This is especially the case on 
 men-of-war, where large numbers of men are crowded into con- 
 fined spaces, and the sanitary value of varnish is of the utmost 
 account; not only does it keep out the dirt, but the strong alcohol 
 and the resin both act as germicides. But nothing is more repre- 
 hensible than the practice which some captains have of ordering 
 all the bright work varnished, over and over again, with shellac. 
 It is not uncommon to see naval vessels come in from a cruise 
 with the bright work so bedaubed and plastered with shellac 
 that it was enough to discourage the constructor and the master 
 painter from ever trying to make a ship look well. Spar var- 
 nish, and that of the best quality, and not too much of it, is the 
 only thing which should ever be used on bright work; it may 
 be cleaned and repolished as often as necessary. It is good prac- 
 tice to use spar also when it is necessary to thin enamel paints, 
 rather than to use turpentine or oil; nothing is better for this 
 purpose on land as well as at sea. 
 
 Ships are often repainted too much; a naval constructor 
 told the writer that he had removed layers of paint which con- 
 
300 TECHNOLOGY OF PAINT AND VARNISH. 
 
 tained, when viewed with a microscope, over a hundred laminae. 
 It seems as though the officers who were responsible for this 
 ought to be taught a little common sense. Yachts and other 
 pleasure-boats are looked after with more intelligence in this 
 respect, and are usually in admirable condition. 
 
 A white interior enamel is often made for some of the cabins 
 of ships, especially in the navy, by mixing the pigment with 
 damar varnish. This probably makes the whitest enamel; but 
 it lacks ' durability, and especially very quickly loses its gloss. 
 On vessels of any value it is advisable to use a better article, 
 for a good oleo-resinous enamel, which is white enough for the 
 finest house, is certainly white enough for a cabin; and it has 
 durability. Damar dries more quickly, but never has as good 
 a surface, and it is certainly better to use a more permanent 
 coating. 
 
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CHAPTER XIX. 
 
 CARRIAGE-PAINTING. 
 
 To treat fully of the painting of carriages and coaches would 
 require a volume, and volumes have been written about it; but 
 the casual inquirer into the art may be satisfied with an outline 
 of the methods and the principles involved. It has always been 
 near the border between artistic and industrial painting, and 
 its practitioners have held a high rank. Carriages must be 
 pleasing to the eye; but still more they must be strong and dur- 
 able, retaining not only their form and strength, but, if possible, 
 their finish after exposure to the inclemencies of the sun, wind, 
 mud, and rain. 
 
 Severe Exposure of Varnish on Carriages. Pictures are pro- 
 tected by frames, hung on shaded walls, untouched save to remove 
 carefully the dust which settles on them ; furniture is indeed used, 
 often carelessly, sometimes, though not usually, exposed to the 
 sun, but at any rate it is protected from the snow and rain ; but 
 carriages are drawn by horses, or propelled by engines, rapidly 
 through grinding sand, dust, mud, and exposed to injury from 
 branches of trees and accidents of every sort, yet the surface 
 must be polished and lustrous, and the moisture must be kept 
 out of the wood, or it will fall in pieces. The deacon's one-hoss 
 shay was, we may be sure, painted and varnished with a knowl- 
 edge and skill which need not have shamed its historian; else 
 there would have been no tale to tell. 
 
 It is a general belief that carriages are painted in a less durable 
 manner than was formerly the practice; and this is in some 
 instances probably true. It must be remembered, however, that 
 where one carriage has lasted for a generation thousands have 
 
 301 
 
302 TECHNOLOGY OF PAINT AND VARNISH 
 
 perished, leaving no sign, in a few years; and probably some of 
 our posterity will point to a few long-surviving coaches of our own 
 time as we do to the relics which have come down to us. It must 
 be that there have always been, as there are now, good finishers 
 and poor. The latter are soon forgotten if they belong to a former 
 generation, but if they are our own contemporaries we not only 
 remember them but unjustly judge their better fellow workmen 
 from their work. This is indeed a general law. It applies not 
 only to carriage-painters but to varnish-makers as well; and there 
 will always be those who exalt the past at the expense of the 
 present, and discredit the skilful workman because poor work is 
 common. It has always been common, and it always will be. 
 
 Good Work is Slow. It is said in the twenty- eighth chapter 
 of the book of the prophet Isaiah that "he that believeth shall 
 not haste"; and this may well be taken for a motto, not by car- 
 riage-painters alone, but by all who have to do with varnish, 
 whether as makers or users, and perhaps by some other people. 
 Good varnish is slow to dry, so is good paint; a job which must 
 be hurried will lack in durability, but a job which takes a long 
 time is costly. 
 
 It is in general true that it is essential to have a suitable founda- 
 tion on which to apply a finish, whether for beauty or utility. 
 Xenophon, who wrote, four hundred years before the Christian 
 era, the oldest treatise on horsemanship with which we are 
 acquainted, says that "just as a house would be good for nothing 
 if it were very handsome above but lacked the proper foundations, 
 so too a war-horse, even if all his other points were fine, would yet 
 be good for nothing if he had bad feet, for he could not use a 
 single one of his fine points." It is exactly so with painting; 
 if the foundation be poor the subsequent work and material are 
 thrown away. The basic material is wood; this must be properly 
 treated to make a suitable foundation. In the first place it 
 must be dry; not merely kiln-dried, but previously well- seasoned; 
 but this is a matter which belongs to the art of the wood- worker. 
 It must be so treated as to be damp-proof, and this involves 
 filling the pores of the wood on both sides and on exposed edges; 
 
CARRIAGE-PAINTING. 33 
 
 not a place may be omitted. This is equally true of furniture, 
 and in fact the finishing of the latter is based on the practice 
 of carriage-painters. 
 
 Filling. The pores of the wood, then, are to be filled; the 
 first coat is usually linseed-oil, to which a little white lead has 
 been added, just enough to color the oil. Some painters use 
 varnish for the priming coat, but this is because they are in 
 haste, and they use a quick- dry ing varnish, which is not as good 
 as oil. In place of white lead some use finely ground silica, and 
 some use yellow ochre, and many a mixture of these; but it is 
 of little consequence in the priming coat, for this is chiefly oil, 
 and the oil is really absorbed by the wood. The real surfacing 
 now begins; and many men use many things. The object all 
 aim at is to get a hard, smooth, level surface; on this the paint 
 is applied, and then the varnish. If the foundation is too elastic 
 it will not hold the surface in place, and the latter will crack, even 
 though of tough and elastic material. These "elastic under-coat 
 cracks" are sometimes very puzzling. The writer has seen them 
 on the surface of a highly elastic varnish which had been applied, 
 four coats in thickness, on a steel surface, as a protective material; 
 the hot sun hardened the outside pellicle, and when it suddenly 
 cooled and all such exterior work is subject to frequent and 
 considerable changes of heat this surface cracked, because the 
 under-coat was so elastic that it practically gave it no support. 
 Such cracks are purely superficial, and are not likely to affect the 
 protective action, but they ruin the beauty of the finished surface. 
 Elastic under-coat cracks, then, must be prevented by making 
 the foundation hard and firm, and gradually working up, by the 
 progressive use of more and more elastic coatings, to the finishing 
 varnish, which is as elastic as is compatible with a sufficient degree 
 of lustre. 
 
 White Lead as a Filler. At this stage the chief differences in 
 treatment are in the use of white lead or of a filler composed of 
 silex or silicates. The older practice is to use white lead, and 
 this is susceptible of variations. The first method of using lead 
 consists in painting the surface with a white- lead paint. This 
 
304 TECHNOLOGY OF PAINT AND VARNISH. 
 
 probably was originally white lead in pure linseed-oil, but at pres- 
 nt it is made by thinning paste white lead (which is called by 
 painters "keg lead") with half oil and half turpentine; the pro- 
 portion of turpentine is increased often to five-eighths and some- 
 times to three-fourths; the greater the hurry the more turpentine 
 is used; five-eighths turpentine is very common. This is well 
 brushed out so as to make as smooth a coat as possible. It is 
 followed by another coat of lead which is prepared by thinning 
 paste or "keg" lead with spirit of turpentine; sometimes a little 
 oil is added, not usually as much as 5 per cent, by measure. 
 Paint made in this way will have a lustreless surface, called "flat" 
 or "dead." Commonly a very little lampblack is added to the 
 lead in both these coats, enough to produce a lead or slate color; 
 and to hurry the work about 2 per cent, of japan is also used. 
 The last coat should be applied with great care, to produce as 
 smooth a surface as possible. 
 
 Rub-lead. Instead of these two coats it is also a practice to 
 use what painters call "rub- lead." This is white lead mixed with 
 lampblack to a slate color and thinned with oil and japan. A con- 
 siderable amount of the latter is used, often 20 or 25 per cent. 
 This by good rights ought to be ground through a mill. It may 
 be remarked that the lampblack is thought to add to the smooth- 
 ness and flowing quality of the lead. This is made of such a con- 
 sistency that it may be brushed on with a stiff bristle brush; and 
 when it has been on long enough to set well and be decidedly stiff 
 the lead is rubbed well into the pores of the wood; this is best 
 done with the palm of the hand. In this way a very fine, dense 
 surface is obtained, and after hardening two or three days it is 
 ready to be sandpapered. 
 
 Knifing-lead. More rapid work still is done by mixing lead 
 to a putty and applying it with a putty-knife. For this purpose 
 paste lead is mixed with about an equal weight or twice its weight 
 of dry white lead (the larger the proportion of the latter the quicker 
 it is to work, because the oil slows it), and with a mixture of equal 
 parts of rubbing- varnish and japan; usually a little spirit of tur- 
 pentine is added. In fact, painters of all sorts usually add a 
 
CARRIAGE-PAINTING. 35 
 
 little turpentine to everything, without much thought of the con- 
 sequences. It promotes the union of the different parts of a mix- 
 ture, as it is a powerful solvent, and adds to the fluidity of the 
 whole. This lead compound is, for very rapid work, colored to 
 suit the paint which is to be used over it; otherwise it is tinted 
 with lampblack. It is either put on with a putty-knife or is 
 thinned with turpentine to a very heavy paint and applied with a 
 brush, after which, as soon as it sets, it is worked into the wood 
 with the flat blade of the knife, and always the surplus is carefully 
 removed. Rub-lead is almost universally used on wheels and 
 running-gear, and frequently on bodies; but knifing- lead is re- 
 stricted to bodies, the process being adapted to flat surfaces. 
 
 These are the various ways in which lead is used as a filler. In 
 all cases after it is thoroughly hard it is sandpapered to get a very 
 smooth surface. If lead is not used a wood-filler is applied. This 
 is of course a paste-filler, having a body of powdered quartz or 
 some equivalent, often containing some white lead ; and the liquid 
 in which it is ground is a varnish. This is well rubbed into the 
 wood with a stiff brush, and when dry and hard is sandpapered. 
 Two or more coats are often applied. 
 
 Putty. It is the practice of house- painters to putty holes and 
 crevices immediately after priming; but carriage- painters usually 
 wait until the filler is all in. The operation is the same, except 
 that as the work is to receive one or more additional surfacing 
 coats and is then to be painted, it is not essential to a fine finish 
 that so much care be taken not to scratch the surface, and steel 
 putty- knives are used. If there is a crack where there is a possi- 
 bility of flexibility between two adjacent pieces of wood it is bad 
 practice to putty it, as the putty will in time work loose and come 
 out. Putty, on a carriage, is for nail-holes and the like. White- 
 lead putty is universally used, usually mixed with some japan to 
 make it harden very rapidly. Of course it is more durable if 
 mixed only with oil, or perhaps finishing-varnish; but tough putty 
 cannot be sandpapered. 
 
 We have now got the woodwork primed, filled (either with lead 
 or prepared filler), and puttied. The next thing is sandpapering. 
 
306 TECHNOLOGY OF PAINT AND VARNISH. 
 
 In fact the first thing is too, for before the priming is applied the 
 painter should see that the surface is as level and true as possible, 
 and if he cannot make the wood- worker turn it over to him in 
 that condition he must do it himself, for that is the time when it 
 ought to be done and can be most easily. Usually each coat from 
 the priming up is sandpapered a little; but at this point, after the 
 putty has been applied, the surface must be made as good as 
 possible, and all dust be thoroughly removed. 
 
 Rough-stuff. The next coat is rough- stuff. The makers of 
 carriage-paints prepare better rough-stuff than the amateur ever 
 makes; but in general it may be said that it is essentially com- 
 posed of a silicious filler not quartz, but some mineral silicate, 
 ground to a moderate degree of fineness, mixed with some white 
 lead; from a third to a quarter the weight of pigment may be 
 lead, but as lead is twice as heavy as the silicate, the latter will 
 amount to five-sixths or seven-eighths the bulk of the whole. 
 Ochre is regarded by some as a valuable ingredient. The liquid 
 is essentially a rubbing-varnish; the carriage- painter who mixes 
 his own adds japan, but the paint manufacturer (who in this case 
 is also a varnish-maker) makes a special varnish which possesses 
 just the right qualities for the purpose without the addition of a 
 needless amount of injurious driers. The thing aimed at is to 
 make a sort of paint which will dry rapidly to a very hard surface, 
 capable of being ground down to a smooth, glassy finish, and at 
 the same time have about the same rate of expansion and con- 
 traction as the foundation on which it rests, so that it will not 
 crack and come off. This is no simple thing to accomplish; and 
 it is in general safer to buy of a maker who purchases his filler in 
 lots of one to ten car-loads, and always uses the same materials, 
 than to try to use those things which are bought in small quanti- 
 ties and from miscellaneous sources. 
 
 It is applied with the brush, and as it is quick to set it must 
 be put on rapidly and smoothly with a soft brush and by a skil- 
 ful hand. One coat a day can be put on; three to five are needed, 
 and often the latter number is doubled. If the material is right 
 it is not necessary to sandpaper or give similar treatment between 
 
CARRIAGE-PAINTING. 307 
 
 coats in order to secure adhesion, but a substantial body may be 
 rapidly built up. 
 
 Guide-coat. It is usual to color the last coat with ochre or 
 white lead. This is called a guide-coat, as it serves as a guide to 
 uniform rubbing of the surface. After a sufficient amount has 
 been laid on the whole should be allowed two or more days to 
 harden. It ought to be as hard as it will become, and time is well 
 spent waiting for it to dry. 
 
 Pumicing. This is not sandpapered, but is brought to a sur- 
 face with pumice and water; and in this case the pumice is not 
 powdered, but blocks of natural pumice-stone, which is a sort of 
 porous lava, are used. These are sawn to the desired shape, ground 
 down on a flat surface, and they are ready for use. The lightest 
 and most open pieces cut most rapidly; the more dense are used 
 for finishing. The rubbing is not done with circular or irregular 
 motions, but back and forth in the same direction. The surface 
 is kept well wet with pure water, but not flooded; but it should 
 be frequently washed off and examined. It is sponged off with a 
 clean sponge, and wiped dry with a clean piece of chamois leather. 
 This operation is to be learned by experience and observation, 
 not from books. It is one which requires patience and skill, and 
 produces the surface on which the color and varnish are to be 
 exhibited. 
 
 Color. The next step is the application of the color. Paint 
 for carriages is made of the necessary pigments, ground to the 
 last degree of fineness. They ought to be ground as fine as artists' 
 tube-colors; but instead of being ground in oil they are ground in 
 "grinding- japan," a sort of varnish, loaded nearly to the point of 
 saturation with lead and manganese driers. Not all colors can 
 be ground in the same medium, or they will gelatinize and spoil. 
 Such must have a special varnish or japan, the nature of which 
 must be learned by experiment. These "coach- colors" are 
 sold in air-tight tin cans, well filled, and the best of them will 
 not keep forever. They should be purchased from fresh stock 
 as they are needed. Varnishes improve with age, but no paint 
 does, and coach-colors are, though perhaps not as bad as var- 
 
308 TECHNOLOGY OF PAINT AND VARNISH. 
 
 nish- enamel paints, worse than those ground in oil. Coach- 
 colors are sold in what is practically a paste form, and are to 
 be thinned with oil and turpentine. Some use varnish instead of 
 oil, but the latter is generally advised. They are put on in thin 
 coats and dry rapidly. 
 
 Rubbing-varnish. Over this is applied rubbing-varnish in 
 full, heavy coats. These do not depend entirely on oxidation for 
 hardness, for rubbing- varnishes contain only from 6 to 12 gals. 
 of oil to 100 Ibs. of resin, and the large proportion of the latter 
 helps materially to give them hardness. They should, however, 
 be allowed ample time to dry. They are called rubbing-var- 
 nishes because they are hard enough to bear grinding down to a 
 smooth, even surface with pumice and water; but in this case 
 the blocks of stone are not used. The pumice is powdered, and 
 is applied with a piece of thick felt, well wet with clean water. 
 Several coats of rubbing- varnish are applied; not less than three, 
 often more. Each coat is rubbed; the first lightly, the others more 
 thoroughly. Before rubbing the surface is wet with clean water; 
 then the wet pad of felt is touched to the powdered pumice and 
 the rubbing begins. This is an art and must be learned; but 
 the observer will notice that the expert uses steady strokes, all 
 in one direction; at first rubbing lightly, aftirward with more 
 force. The edges and mouldings are first treated, and the work- 
 man finishes up a panel in the middle. It is easier to cross-rub 
 the ends of panels ; but this is not regarded as good form by 
 many of the professionals. When the surface has been rubbed 
 it is well washed, and the utmost care is required to have all 
 the utensils for this service clean. 
 
 Cleanliness. An entire extra set of sponges and chamois 
 leather is kept for finishing up the washing, so that the surface 
 at last may be as clean as possible. It goes without saying that 
 all this work of varnishing and cleaning must be done in a room 
 kept clean and free from dust. A varnishing- room should not 
 contain shelves or anything to hold dust ; it must be free" from 
 draft, and should be entered from a vestibule which has a second 
 door opening into some other room; and the floor should be 
 
W 
 
 B _ 
 
 r 2 
 
CARRIAGE-PAINTING. 309 
 
 higher than that of the adjacent room, so that there will be a 
 step up, which helps to keep out the dust which naturally lies 
 on the floor. Nine-tenths of the trouble which varnish-users 
 encounter comes from dirty and badly contrived rooms. Every 
 varnish-maker is a victim of innumerable instances of this. The 
 fault of the location is attributed to the varnish, and the user is 
 intolerant of criticism. It is seldom of any use to tell a man that 
 his trouble is due to his own deficiencies, whether personal or 
 of his surroundings. He wants something which will compensate 
 for those things ; he doesn't get it. 
 
 Finishing-varnish. The finishing-varnish, which contains 
 about 25 gals, of oil to 100 Ibs. of the best hard varnish- resins, 
 and is of all varnishes the most exacting and the most difficult to 
 make, is in this country often called "wearing-body" varnish. 
 It is at once brilliant, hard, elastic, and durable. This is the kind 
 of a varnish which the great painters of the middle ages were 
 trying to make. Kept indoors, as works of art are, it would last a 
 very long time. It is not the most durable varnish that can 
 be made, but is the most durable brilliant varnish. Contain- 
 ing a large proportion of oil its flowing qualities are second only 
 to that of oil itself; and it is applied as a heavy flowing coat 
 with a large, thick brush of the finest hair. Like every difficult 
 operation of art it is only to be learned by observation and practice. 
 It is the finish and crown of all the work which has gone before. 
 
 Keep the Carriage Warm, Dry, and Clean. When it is 
 done the structure is left at rest in a dry, warm, clean room for 
 a day ; then it is dry* enough so that dust will not stick to it easily, 
 and it may be removed to another dry, warm, clean room to 
 remain until it is thoroughly dry and hard. Varnish, while 
 drying, must always be kept warm, and of an even temperature, 
 not exposed to sudden changes of any sort, and dry as well as 
 clean. A damp atmosphere, sometimes unavoidable because of 
 the climate, is a fruitful source of trouble. Dirt and dust are 
 the great adversary, and there is no peace in this life for the 
 varnish-user who cannot overcome them. When one reads of 
 the Chinese and Japanese lacquers which harden in rooms with 
 
310 TECHNOLOGY OF PAINT AND VARNISH. 
 
 wet floors and the walls hung with wet sheets he is moved to envy. 
 The heathen Chinee certainly does accomplish wonderful things 
 in this, and perhaps we may have to learn from him; though 
 it is believed by many that there are just as great heathen engaged 
 in the varnish business in this country as there are anywhere. 
 
 Shorter Methods. It is not here asserted that every grocer's 
 delivery wagon is finished with the elaborate detail which has 
 been described. There are many short cuts to economy. For 
 instance, it is very common to omit the use of rough- stuff. The 
 work is primed, given a coat of rub-lead (which may be tinted 
 the color of the paint which is to follow), sandpapered, painted, 
 and given a coat, not of rubbing- varnish, but of finishing- varnish ; 
 and good durable varnishes are made at a less cost than wearing- 
 body. Such a finish is not as smooth or brilliant as a more costly 
 one, but it may be reasonably durable. Rough- stuff is very 
 commonly omitted on the running- gear of carriages, especially 
 on the wheels, as being too hard and possibly brittle. The 
 running-gear is made up of pieces with curved surfaces. These 
 are much more shiny than flat ones, hence require less work to 
 make them look well. Gears are usually finished with a darker, 
 and therefore cheaper varnish than that used on the carriage- 
 body. There is no limit to the ingenuity which has been dis- 
 played in inventing cheap ways to refinish wagons and still have 
 them look well enough to be accepted by the owners. Even the 
 railroad- coach painters can take lessons from the carriage men 
 in this. As Denham's couplet has it : 
 
 " They varnish all their errors, and secure 
 The ills they act, and all the world endure." 
 
 But these things are out of place here. The aim of the fore- 
 going sketch of the subject is to tell the uninstructed but inter- 
 ested inquirer the general methods employed by good workmen, 
 the principles of which are common to all the high- class shops, 
 whose works do praise them; and of whom we may say, with 
 Shakespeare : 
 
 "We'll put on those shall praise your excellence, 
 And set a double varnish on the same." 
 
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CHAPTER XX. 
 
 HOUSE-PAINTING. 
 
 THE most important branch of the art of painting is that which 
 relates to the protection and decoration of houses, by far the 
 greatest portion of which are built of wood, and those which are 
 said to be of brick or stone are largely of wood, having wooden 
 floors, doors, and door- and window- casings. Oil paints are 
 almost universally used on the exterior woodwork, and very 
 largely within. Varnishes are also used on the interior, and in 
 the bettef class of houses enamel paints are used to a considerable 
 extent. Ceilings sometimes receive an alleged de oration with 
 fresco or distemper paints, but the less said about that the better. 
 It is only palaces and very fine houses which should be decorated 
 in fresco. 
 
 The vast majority of houses in this country are painted with 
 white-lead paint, either pure or (more commonly) adulterated 
 with barytes (barium sulphate), terra alba (sulphate of lime), 
 whiting (carbonate of lime), or other less important sophisti- 
 cations. Carbonate of barium is sometimes used instead of the 
 sulphate. These barium compounds are the least objectionable, 
 being in fact substances chemically inert and of stable composi- 
 tion ; but they are practically without coloring power, being nearly 
 transparent in oil, and while they probably help to protect the 
 wood they are really used only to cheapen the paint, and commonly 
 to increase the profit to the maker or dealer; not at all for a benefit 
 to the consumer. The latter is not an object of unreserved pity; 
 he gets these things because he is unwilling to pay a fair price 
 for the more economical material, and this because of his ignorance. 
 
 White zinc is also an important and valuable white paint; 
 
312 TECHNOLOGY OF PAINT AND VARNISH. 
 
 zinc paint is harder than lead paint, and a mixture of zinc is 
 therefore regarded by many as better than pure lead, especially 
 for finishing- coats. It is commonly thought to be of a purer 
 white than white lead, and is largely used on interior work espe- 
 cially; when added to white lead it is usually in the proportion 
 of one-third zinc to two-thirds lead. 
 
 Very many houses are painted white, but more commonly 
 with some light color made by the addition of a tinting material 
 to the white paint. Some of these tinted paints are fast to light. 
 This is commonly true of the grays, and of those yellows which 
 contain ochre, and all those paints tinted with the iron oxides; 
 but yellows tinted with chrome yellow, or colors made with chrome 
 green or Prussian blue, are fugitive, and light shades of these 
 colors should be avoided for exteriors. 
 
 White lead is usually sold as "paste white lead" ground 
 with 10 per cent, of linseed- oil, and when obtained in this form 
 from the manufacturers of white lead (who are sometimes but 
 not usually makers of prepared paints) is always pure, so far as 
 my experience goes. This should be thinned with pure linseed- oil. 
 
 Do Not Use Thinners. No turpentine or benzine should ever 
 be allowed about the premises where this work is going on. Most 
 of the failures of lead and zinc paints are due to the use of these 
 volatile thinners. If raw linseed- oil is used it may be desirable 
 to add 5 per cent, of a good drier. This should be pale in color, 
 indicating that it has been made at a low temperature, and should 
 be free from rosin. The latter is not an easy thing to detect, but if 
 a fair price is paid, say $1.50 to $2 a gal. at retail, and freedom 
 from rosin is guaranteed by a maker of good reputation, the buyer 
 ought to be safe. For the benefit of the maker of paints it may 
 be said that such driers are made usually of oil, combined with 
 much lead and a little manganese. Japan driers containing resins 
 (not rosin) are also excellent, but their price is high if they are 
 of good quality. There are some low- temperature manganese 
 driers which have a good name, but the black or very dark japan 
 driers are to be avoided, for they injure the durability of the 
 paint. Every bit of drier you use is a damage to you, and the 
 
HOUSE-PAINTING. 3 1 3 
 
 lack of it is fatal, for the paint certainly must dry in a reasonable 
 time. 
 
 Dark Colors Most Durable. Paints made with white lead and 
 white zinc as a basis are good paints, but there are more durable 
 paints (for wood) made of other pigments. The ochres, umber, 
 sienna, and the iron oxides in general are far more permanent, 
 and to paints the color of which will admit the use of an appreci- 
 able amount of lampblack this latter pigment imparts a high 
 degree of stability There is no paint so lasting on wood as 
 black paint made with lampblack as the coloring-matter. A 
 great variety of subdued yellows, browns, and reds may be made 
 which will outlast the lead or zinc paints. Sometimes, where the 
 final color can only be had by one of the latter, the priming-coat 
 and the second may be of the former with advantage. They are 
 also cheaper. Lead and zinc are expensive pigments, and a white- 
 lead paint weighs 20 Ibs. to the gallon when ready for use, while 
 oxides weigh about 12 Ibs. per gallon. 
 
 Knots. Pine wood usually contains knots, some of which are 
 full of pitch, and this pitch will penetrate any oil paint or oleo- 
 resinous varnish and make a bad spot. These knots may be 
 covered with shellac varnish, on which the pitch does not act, 
 before painting. Some of the liquids distilled from pine wood, 
 of which many are on the market, are also said to be efficient for 
 this purpose. Some woods, southern pine in particular, are very 
 bad to paint because of the pitch they contain, which makes the 
 paint peel off; and this should be remembered when passing 
 judgment on a job of painting which has not lasted well. If 
 shellac is used for stopping knots it is common to use white shellac 
 if a very light paint is to be used over it; but if the paint is dark 
 use orange shellac because it is a better varnish than white shellac. 
 The latter must be used if the wood is to be finished in the natural 
 colors with varnish. 
 
 Priming-coat. If a coat of good thick paint is applied to a 
 fresh surface of wood the oil is absorbed, leaving the pigment 
 without enough binding material. For this reason it is proper to 
 first prepare the surface of the wood before the paint is applied. 
 
314 TECHNOLOGY OF PAINT AND VARNISH. 
 
 This is called filling the surface ; in reality it is filling the pores, 
 and the material used is called a filler. The best filler for wood 
 which is to receive ordinary oil paint is a coat of pure raw linseed- 
 oil. After this has disappeared in the wood a coat of very thin 
 paint may be applied. Sometimes this second coat is also pure 
 oil, but if pigment is added very little should be used. 
 
 Putty. After the wood is thus filled, or primed, is the time to 
 putty up all nail- holes and other defective places. Ordinary putty 
 should not be used for this, but only white- lead putty, made of 
 paste white lead with enough dry white lead worked into it to 
 make it stiff enough to suit the workman. This is better than 
 the best common putty, which is made of whiting or ground 
 chalk mixed with linseed-oil, and if honestly made is very durable ; 
 but, cheap as this is, it is made cheaper by using inferior oil, and 
 it is now very difficult to get any pure putty. It is therefore very 
 important to use white-lead putty, which may be tinted to match 
 the paint. On outside painted work it is perhaps allowable to 
 apply putty with a steel putty- knife; but on interior work a 
 wooden stick or spatula must be used, so as not to mar the surface. 
 Putty should never be applied to the natural surface of the wood, 
 since that would absorb part of the oil and leave the putty dry 
 and friable; the wood must first be primed. 
 
 The surface is now ready to be painted, and should receive 
 at least two good coats of paint, sufficient time to dry being allowed 
 between coats. If the window- casings and other raised surfaces 
 are to be painted a different color from the body of the house, it 
 is well to do this first; the body-color may then be laid neatly up 
 to the other. It is a good plan to paint the back or interior sur- 
 face of all window- and door- casings before they are erected with 
 a cheap oxide paint, made with pure linseed-oil; this will prevent 
 warping and distortion. This is not commonly done except on 
 fine houses, but it is desirable. 
 
 Area Covered. A gallon of paint ought not to cover more than 
 500 sq. ft., and a gallon of priming-coat not more than 300; as 
 a matter of fact, for outside painting a gallon does not cover as 
 much as this. 
 
HO USE-PAIN TING. 3 J 5 
 
 The foregoing directions apply to the most common sort of 
 exterior painting. Nothing has been said about the use of varnish 
 in paint for this purpose, but in fact the best makers of house- 
 paints are large buyers of varnish, the addition of which increases 
 the durability and improves the appearance of the paint. It makes 
 it glossy, so that dirt does not so easily adhere to it. If varnish 
 is used for this purpose it ought to be good varnish, and this will 
 increase the cost of the paint. 
 
 Interior Woodwork. The treatment of the interior woodwork 
 is much more complicated. It should be thoroughly seasoned 
 and dry before any finishing is done, and should be sandpapered 
 to an even surface, all sandpapering to be done with the grain of 
 the wood. As recommended for window- and door-casings, the 
 back of all interior woodwork must be thoroughly painted with a 
 good, durable linseed- oil paint, thin enough to serve as a priming- 
 coat. This must be done immediately after the pieces are delivered 
 on the premises. The first coat of filler must also be applied to 
 the front or outer surface. In this way the absorption of moisture 
 will be prevented; and all this should be done before the work 
 has been allowed to remain overnight on the premises. This 
 may seem somewhat exacting, but we should remember that 
 neglect of this precaution may impair the value of the material 
 during its whole service. The most important of all things is to 
 start right. The first coat of filler is usually linseed-oil, and this 
 may be applied very rapidly. 
 
 Fillers. There are two sorts of fillers made: liquid fillers and 
 paste fillers. The former are commonly rosin compounds, and 
 never should be used for any purpose. If a liquid filler must be 
 used, fill the wood completely with raw or boiled linseed-oil, or 
 with a good varnish. The very best filler that can ever be put on 
 wood is a good varnish; but this is not what is commonly meant 
 by a filler. Paste fillers are a sort of paint; the best have pul- 
 verized quartz as the solid part, corresponding to the pigment, 
 and the liquid is a quick-drying varnish. Only enough liquid is 
 used to make a sort of paste, and before applying this is mixed 
 with spirit of turpentine to such a consistency that it can be applied 
 
3 1 6 TECHNOLOGY OF PAINT AND VARNISH. 
 
 with a short, stiff bristle brush, and it must be rubbed well into 
 the pores of the wood. In about half an hour it will be found to 
 have set, and the excess must then be rubbed off clean, first with 
 excelsior (fibrous wood- shavings) and then with felt, rubbing 
 across the grain of the wood so as to force the filler into the pores. 
 It is practically impossible for the amateur to make as good a 
 filler as he can buy. The pigment must be ground fine, yet it 
 should not be so fine as to have too little grit, and the mixing of 
 a varnish to have just the right properties is a difficult matter. No 
 better advice is possible to any one desiring to experiment in this 
 direction than to get the best paste filler on the market and try 
 to match it. Wood-fillers may be, and usually are, stained by 
 the addition of oil-stains to the color of the wood, or to the color 
 desired by the designer. This is done when they are finally 
 thinned before using. These oil-stains are really paints made 
 with selected pigments of extraordinary fineness, and may be 
 added to or thinned with oil, varnish, or turpentine. Such pig- 
 ments are used as are somewhat transparent but have a deep 
 and brilliant color; great staining- power, but not great opacity. 
 Raw (unroasted) sienna may be regarded as a typical pigment of 
 this class. 
 
 The practice of filling wood completely with varnish has been 
 recommended. It is a very old method. It is natural that those 
 who do this should wish to use a cheaper varnish for this use than 
 that with which they finish ; also that they should want a varnish 
 which will dry quickly. The combination of these qualities, car- 
 ried to the extreme, results in a rosin varnish loaded with driers; 
 and this is what is meant now, in the trade, by a liquid filler. 
 Rosin, with little oil, requires very little turpentine or benzine to 
 make it a thin liquid; in fact pale rosin is almost a liquid already, 
 so that a varnish of this sort has very little volatile matter in it and 
 consequently fills up the pores of the wood very quickly, and dries 
 almost as a spirit varnish does by the evaporation of the solvent. 
 But no good ought to come to the man who puts such a compound 
 on a piece of wood which is afterward to be varnished with decent 
 material. 
 
HOUSE-PAINTING. 317 
 
 A good paste filler, on the other hand, has just as much solid 
 matter in it as possible, and what cementing material there is 
 may be of first-rate quality. There is so little of it anyway that it 
 is not expensive to have it good. 
 
 Object of Filling. The object in using a paste filler is to fill 
 the pores of the wood with solid matter, so that the surface to be 
 varnished shall be without any soft and absorbent places, but 
 hard and glassy. The filler is rubbed into the wood when it is 
 applied, and when it has hardened it is rubbed so that all that can 
 be crowded into the wood may remain, and the surplus be taken off. 
 This is also the way furniture is treated; but rubbing- varnishes 
 are then sometimes used on furniture, while they should not be 
 used on the woodwork of houses, which should be varnished with 
 at least three coats of a moderately elastic varnish, made with 20 
 gals, of oil to 100 Ibs. of resin. Not less than a week should 
 elapse between coats. It is best to sandpaper the first coat with 
 very fine sandpaper, and the second coat, when dry, should be 
 rubbed with curled hair until the gloss is removed. These pre- 
 cautions secure a more perfect union between the different coats, 
 and a more perfect surface. After the last coat has become quite 
 hard, if the glossy surface is not liked, it may be rubbed with 
 powdered pumice and water, with a piece of thick felt, until the 
 gloss is removed. Four coats of varnish are better than three, 
 and if a wood- filler has not been used four coats are necessary. 
 
 Exterior Varnished Work. Exterior woodwork, such as out- 
 side doors, railings, and the like should never receive any filler, 
 which lessens the durability of the varnish, but should be treated 
 with not less than four coats of spar varnish or a varnish made 
 on the same lines as spar; that is, the wood should be both filled 
 and varnished with the same material. There is no objection to 
 a preliminary coat of oil, which should have plenty of time to 
 dry. Usually it is most convenient to apply oil for the preliminary 
 coat, which is to hinder the hygroscopic action of the wood, and 
 is put on before or immediately after the woodwork has been 
 brought on the premises; and all inside blinds, window-sills, and 
 jambs, in fact everything exposed to the direct rays of the sun, 
 
3i8 TECHNOLOGY OF PAINT AND VARNISH. 
 
 must be treated as exterior woodwork. Outside blinds are painted 
 with the same kind of paint, though not the same color, as the 
 outside of the house. 
 
 Interior Enamel Painting. If any of the interior woodwork 
 is to be finished in white enamel paint (or any light- colored 
 enamel), it should be well painted with pure white lead and 
 linseed-oil This should be done according to the directions for 
 outside work. It is allowable, however, to add some spirit of 
 turpentine instead of all oil, as this makes the paint dry more 
 quickly, and on interior work will be sufficiently durable. Two 
 coats of white enamel paint are to be applied for a finish. The 
 question may' arise, why not do all the painting with enamel 
 paint? Because the oil paint contains more 'pigment and less 
 vehicle, and hence is much more opaque than enamel. It is 
 cheaper by the gallon, very much cheaper in labor, far more 
 rapid, and is good enough. Two coats of an enamel paint applied 
 to a good white under- coat, which should consist of a priming- 
 coat and two full coats, will give a beautiful surface. The first 
 of these enamel coats should be rubbed with curled hair, and 
 the second may be finished to suit the owner. 
 
 Floors. Floors are a source of endless trouble. Soft-wood 
 floors are sometimes painted, and this is easy, for when the paint 
 wears off it can be renewed. Some soft-wood floors are stained. 
 The best way to do this is to thin down an oil-stain with spirit of 
 turpentine and color it. The stain sinks into the wood and cannot 
 be removed, except as the wood wears off. The floor can then be 
 varnished. If it has already been filled with varnish the stain 
 cannot get in; then the easiest way is to add some oil- stain to a 
 floor varnish and apply it. Hard-wood floors are not stained, 
 but are varnished to show the natural color of the wood, and 
 look very fine when new, but the soles and especially the nail- 
 clad heels of shoes will wear the varnish off after a little; not 
 all over the floor but near doors and wherever people continually 
 pass. The margins of the floor are all right but the worn places 
 ' look badly, and if not attended to, dirt gets into the grain of the 
 wood and can hardly be removed. If these places are revarnished 
 
HO USE-PA IN TING. 3 * 9 
 
 and the rest of the floor left untouched a spotty appearance is 
 produced; but the owner may be consoled by rinding that if the 
 varnish is rubbed out thin around the edges of the newly var- 
 nished places it does not show so much, and after a week or two 
 is not at all conspicuous; and in the judgment of the writer this 
 is better than to pile up varnish on those parts of the surface 
 which do not need it. The art of varnishing a floor is not very 
 difficult, and there ought always to be some one about a house 
 with energy enough to do such work in case of emergency. A 
 good floor varnish dries rapidly. If a thin coat is put on at night 
 it is hard enough to use next day. White shellac varnish is 
 very often used on floors, chiefly because it dries almost immedi- 
 ately. It is in fact a very good floor varnish ; but it is not nearly 
 as durable as a good oleo- resinous varnish, and the chief trouble 
 about floors is that the best varnish is short-lived. Factory 
 floors are sometimes covered with galvanized sheet iron, and 
 this wears out after a time; so it must surprise no one to have a 
 coating of varnish wear off, especially as it is only a tenth part as 
 thick as the sheet iron. We must not expect to walk continuously 
 for many months on a layer of anything which is only two or 
 three thousandths of an inch in thickness. 
 
 A filler should never be used on a floor, which should be 
 thoroughly saturated with oil and varnish. The latter should 
 be fairly hard; as it is not exposed to the weather it is not likely 
 to crack, and a soft varnish does not wear as well as a hard one. 
 It may contain 12 to 18 gals, of oil to 100 Ibs. of resin. Less 
 oil makes it brittle; more makes it soft. It would probably be a 
 good plan to use a good varnish- remover once in five or six years 
 and take off all the paint and varnish from a floor and begin anew. 
 Since the improvements in these preparations, paint and varnish 
 can be easily removed without the danger of fire which attends 
 the use of a gasoline torch in a furnished house. 
 
 Floor Wax. There is still another way to treat a floor, which 
 is by the use of wax. The wax is made into a paste with spirit 
 of turpentine and the floor is thoroughly filled with it. This is a 
 rather laborious job and takes some time. The brushes used 
 
320 TECHNOLOGY OF PAINT AND VARNISH. 
 
 for rubbing in and polishing the wax are large and stiff. They are 
 weighted with heavy iron backs and are attached to a long handle. 
 The floor ought to be polished with this brush daily, and twice 
 a month a little fresh wax should be added. A properly kept 
 waxed floor is very handsome. It looks rather better than a well- 
 varnished one, but it requires a great deal of attention, and if 
 neglected nothing can look worse; and after a floor has been 
 well waxed it is difficult, some think impossible, to wash it out 
 so that it will take varnish. A waxed floor in good condition 
 is also very slippery, sometimes almost dangerously so ; rugs slide 
 around on" it like boards on ice. But it certainly is a beauti- 
 ful finish, and protects the wood; and the necessity of keeping 
 it rewaxed, if it is to look well, makes it necessary to do it by 
 domestic labor, and this tends to keep the floor in condition. 
 It is rather hard work to use the polishing-brush efficiently. 
 
 The wax used is not commonly beeswax, but a vegetable 
 wax called carnauba wax, harder than beeswax. Floorwax 
 is not a simple substance, but the best preparations are appar- 
 ently rather complex; each maker has his own formula. Bees- 
 wax is sometimes used; but the carnauba- wax mixtures are less 
 sticky, and much superior to it in every way. Printed direc- 
 tions are furnished by the makers, and may be carried out by 
 any one of ordinary intelligence. Wax finishes are sometimes, 
 though rarely, used on interior woodwork, but not on stair- 
 rails, nor on furniture. They can be applied to floors which 
 have been varnished, if the varnish has worn or been scrubbed 
 off. The fact that the wood is filled with varnish is no objection. 
 In fact the directions for using wax usually advise filling the 
 wood before waxing. 
 
 Metal Roofs and Gutters. Tin roofs and metal gutters and 
 leaders have been a source of trouble from time immemorial. 
 The painter's tradition is that tin roofs cannot be painted until 
 they have stood long enough to become rusty; then the paint 
 will adhere. This is "flat burglary as ever was committed." 
 It is true that paint does not adhere well to new tin. The reason is 
 .that new tin is greasy, or covered with some chemical substances 
 
HO USE-PA IN TING. 321 
 
 which are inimical to paint. Tin plate, it is well known, is made 
 from thin iron plates (called " black plates") by dipping them 
 in a bath of melted tin; in the same way galvanized iron is made 
 by dipping iron in melted zinc. But the melted metal will not 
 adhere to the iron unless the latter is chemically clean. This is 
 effected by dipping it in acid, from which it goes to the bath of 
 hot metal. A little acid is in this way carried over, and thus is 
 formed a film of chloride or sulphate of tin or zinc, which, in 
 an anhydrous and melted condition, floats on top of the bath, 
 and as the coated plates emerge, a little of this compound sticks 
 to them. This is powerfully corrosive, and will destroy any 
 paint. Another trouble is caused by the practice some makers 
 have of covering the melted metal with hot oil, usually palm-oil, 
 to prevent the air from getting at it; and as the plates come 
 through they get a final coating of hot oil. Still another prac- 
 tice is that of hanging the coated tin plates in hot oil to drain. 
 In some of these ways nearly all tin and galvanized iron is coated 
 with something which prevents the adhesion of paint. The 
 remedy is obvious. Clean the roof before you paint it. It 
 ought to be thoroughly scrubbed with soap and water. The addi- 
 tion of sand makes a more thorough job. Some rub the metal 
 well with coarse cloths, such as burlap, well wet with benzine. 
 If soap and water are used, the scrubbing should be followed 
 by a thorough rinsing with clean water, and of course the roof 
 should be dry when painted. By following these directions, 
 tinned and galvanized metal- work may be painted; and aside 
 from these directions the methods and materials employed on 
 structural steel should be used. It is a wise, though not very 
 usual, practice to paint the lower side of the tin before laying 
 it on the roof. This prevents corrosion from below. New 
 metal roofs should receive three coats of a highly elastic varnish 
 or paint; probably four would be economical, for they will almost 
 certainly be neglected. They are exposed to very severe con- 
 ditions, and a varnish or paint too elastic or soft to be used almost 
 anywhere else will grow hard under the heat and intense chemical 
 action of the rays of the sun. There are plenty of compositions 
 
.322 TECHNOLOGY OF PAINT AND VARNISH. 
 
 .sold for painting these surfaces, the secret of which lies in fol- 
 lowing directions essentially like those just given, by which any 
 .good paint may be made to adhere. They are like the drugs 
 which are sold to cure the tobacco habit, which will certainly 
 cure if taken according to directions, one of which is that the 
 patient shall abstain from the use of tobacco for a term of some 
 years; so if these metal paints are used strictly as prescribed 
 they will stick. No doubt they will, if they are good for any- 
 thing. 
 
 Fire-proof Paints. Shingled roofs are sometimes painted 
 ivith what are called fire-proof paints. No paint is really fire- 
 proof, but it may be made to retard the spread of fire. If a roof is 
 painted with something which will prevent its being set on fire 
 by a burning fragment carried by the wind from some other build- 
 ing, it must be conceded that a substantial gain has been secured, 
 and this can probably be effected. In the first place it must be 
 remembered that any oil or varnish is in its original condition 
 highly combustible; that combustion is a process of oxidation; 
 that oil and varnish dry by oxidation, and hence that when they 
 are thoroughly dry they are far less easily set on fire than when 
 fresh; hence it is not fair to test a fire-proof paint until it is thor- 
 oughly dry. Any good paint may be made more resistant to 
 fire by adding to each gallon of it J Ib. or i Ib. of boric (boracic) 
 acid. This is a solid substance which is purchased in the form of 
 a powder or flakes. When subjected to heat this fuses and 
 forms a sort of glass, and this protects the wood from the access 
 of air; also it is slowly converted into vapor, and this forms a 
 protective coating over the roof, for if the air cannot get to the 
 wood the latter may be heated so as to char, but it will not burn, 
 and this is just what takes place. Some of the patented paints 
 contain instead of boric acid some very easily fusible glass, pow- 
 dered. The glass melts with the heat and protects the wood. 
 Ordinary glass will not answer; and this extra-fusible glass is 
 open to the same objection as boric acid, in that it is soluble in 
 water and gradually is washed out by the rain; but, of course, 
 in all cases the oil or varnish in the paint keeps the rain from 
 
HO USE-PA IN TING. 323 
 
 the soluble constituents for a considerable time. Such paints 
 must therefore be renewed rather frequently. 
 
 Sanding. When paint is partly dry, but while it is still tacky, 
 it is sometimes sanded. This is done by sprinkling dry sand over 
 its surface. The effect of this is to make a rough, hard surface 
 somewhat resembling stone in appearance. It does not appear 
 to be generally known that any dry pigment may be mixed with 
 the dry sand, by tumbling them together in a revolving barrel 
 or by any equivalent means; by doing so the grains of sand 
 receive a film of dry paint, and when applied to the painted sur- 
 face an effect is produced which is sometimes much better than 
 can be had by the use of sand alone. A black varnish, for in- 
 stance, can be thus made brown, olive, dark green, or almost 
 any dark color. If desired, a sanded coat, when thoroughly 
 dry, may receive a very thin coat of paint and be sanded again. 
 In this way a very rough surface is produced. The influence of 
 the sand in resisting abrasion is considerable. Metal gutters 
 and leaders on stone buildings can be painted to match the color 
 of the stone and then sanded, when they are much less con- 
 spicuous than if treated in any other way. 
 
 Cellars are usually whitewashed or calcimined; "cold- water" 
 casein paints are also used. These the writer does not recom- 
 mend or disapprove. In some U. S. Government tests they are 
 said to get mouldy, but this does not seem unavoidable, as 
 some germicide ought to be mixed with the paint. 
 
 Plastered walls are sometimes painted. These should be 
 allowed to stand a year before painting if possible; this is to 
 get rid of caustic alkali. They may then be painted with any 
 oil or varnish paint. If time cannot be allowed, they should, 
 before painting, be washed with a solution of brown sugar and 
 vinegar or acetic acid, to neutralize the alkali. This is a standard 
 formula of house-painters; probably the sugar makes saccha- 
 rate of lime. The author has not experimented with it. 
 
 In general it may be said that thin coats of paint or varnish, 
 well brushed out, are more durable than an equal amount of 
 material applied in heavy coats, and are not so liable to crack; 
 
324 TECHNOLOGY OF PAINT AND VARNISH. 
 
 that varnishes and enamel paints should always be rubbed between 
 coats with curled hair or fine sandpaper to remove the gloss, for 
 if this is not done the succeeding coat does not adhere properly; 
 and that on exterior work the last coat of varnish or enamel should 
 be left with the full gloss, as its durability is impaired by removing 
 the gloss from the last coat. There are three sorts of finish for 
 interior varnished or enamelled surfaces, the first being the least 
 and the last the most expensive: they may be left with a full, 
 natural gloss; they may be rubbed to a dull finish with curled 
 hair, very fine sandpaper, or pumice and water; or they may 
 be first pumiced and then given a high polish with rottenstone 
 and water. 
 
 Above all things, use good material. A good varnish may 
 be had for $3 a gallon at retail, and will give a finish that with 
 moderately good care will last many years; while a cheap varnish 
 sold for $1.50 or $2 will lose its lustre in a short time and will be 
 a positive eyesore in a year or two. The former, even if it cost 
 $15 a gallon, would be cheaper than the latter. There are legiti- 
 mate and proper uses for cheap varnishes; but it is a shameful 
 thing to put them on a house which people have got to live in 
 and look at, and which is intended to last for generations. Not 
 only is the appearance of such things poor, but they do not pro- 
 tect the surface, which gets full of dirt and germs of all sorts. 
 A good varnish or paint is one of the best aids to cleanliness and 
 purity of which we can avail ourselves. 
 
 Putty for Windows. The use of white- lead putty has been 
 recommended for filling cracks. Carriage-makers mix a little 
 japan with this to make it dry quickly, and this may perhaps 
 be permitted, though not recommended, for interior work, but 
 not for exterior use; but white- lead putty is not advised for set- 
 ting glass, because it is so difficult to remove when the glass is 
 broken and must be renewed. Regular putty is made by working 
 pure linseed-oil and whiting, which is ground chalk, together 
 until of the proper consistency. It is applied in a plastic condition, 
 but rapidly sets and finally becomes hard and is very durable. 
 But the reader is advised that pure putty is only to be obtained 
 
HO USE-PA IN TING. 325 
 
 with great difficulty. It is adulterated, or rather a spurious sub- 
 stitute is made, by the use of marble- dust instead of whiting. 
 Marble-dust is granular and harsh, whiting is soft and smooth; 
 and the oil is adulterated with or entirely substituted by some 
 cheap mineral oil or rosin mixture. If pure putty is used the 
 amount used on an ordinary house probably does not amount 
 to $i ; yet the use of an inferior article, the removal and replace- 
 ment of which will cost from 50 cents to $i per window, prob- 
 ably gives a profit to the contractor of 25 to 50 cents on the whole 
 house. The contractor should be required to guarantee the putty 
 for two years, and of the money due him at least $i a window 
 should remain unpaid until the guarantee has expired. The 
 real reason for this very common and inexcusable adulteration 
 is that sash are not hand-made, but factory made, and are com- 
 monly supplied ready glazed, so that the sash-maker is the man 
 who buys the putty, and he buys it in ton lots. Instead of paying 
 say $60 a ton he buys it for $30, and thus makes $30. To secure 
 this he gets bad material, really much worse than none, on fifty 
 houses, at a final cost to the ultimate purchasers of $1,000 or $2,000 
 in the aggregate. The only remedy is in requiring a guarantee, 
 which the contractor may in turn require from the sash-maker. 
 There is absolutely no risk to him if he uses straight goods. If 
 this practice were generally adopted the manufacture of adulterated 
 putty would immediately cease. Putty is made by machinery; 
 but not necessarily, for any one can make it with no other appa- 
 ratus than his hands, and while hand-made putty is costly as 
 compared with the other, $3 or $4 worth of labor would make all 
 the putty needed for an average house; so there is no excuse 
 for using an inferior article. 
 
 Burning-off. Painted woodwork, and especially painted out- 
 side doors, sometimes require the entire removal of the old paint 
 before repainting. The regular way to do this is by "burning- 
 off." This does not mean that the paint is actually burned: 
 If this were done the wood would be charred and injured. It is 
 done by the aid of a painter's torch, burning kerosene or naphtha, 
 by which a flaring flame is directed against the painted surface. 
 
326 TECHNOLOGY OF PAINT AND VARNISH. 
 
 The operator holds the torch in one hand and a broad-bladed 
 putty-knife in the other. The heat softens the old paint and with 
 the putty-knife or scraper he scrapes it off. The paint is not 
 burned at all but softened and loosened by heat. 
 
 Paint-removers. Many preparations have been tried for 
 removing old paint and varnish by chemical action, but these 
 have never been liked because the solution, which has contained 
 water and alkali, gets into the wood and unfits it for recoating; 
 but lately a new sort of paint- and varnish- removers have come 
 on the market. Containing no water and no alkali, they are com- 
 posed of wood-alcohol and other alcohols, benzole, and various 
 other liquids, mixed together, and are very efficient. When their 
 work is done the surface may be washed off with benzine and 
 is ready for repainting or varnishing. Many of the varnish- 
 manufacturers are now selling compounds of this nature. They 
 are applied with less risk and labor than are involved in burning- 
 off. Of course they only soften the old coat, which must then 
 be scraped off in the usual way. 
 
CHAPTER XXI. 
 
 FURNITURE-VARNISHING. 
 
 THERE is an art of varnishing furniture and similar belong- 
 ings, and also a trade. The latter is divided into many parts, 
 and concerns itself with supplies and methods; the former is a 
 matter of principles and the materials for their embodiment. 
 " Furniture varnish" is a term of reproach among the varnish- 
 makers. It is made of " North Carolina Zanzibar gum," other- 
 wise known as common rosin. If there is a normal price for it, it 
 is about the same as that of spirit of turpentine, but it is often sold 
 for half that sum. The writer has among his archives a letter offer- 
 ing a special brand of it for 9 cents a gallon, in barrels, f.o.b. 
 Cleveland, and soliciting permission to send a barrel sample to a 
 large manufacturer of woodenwares. Nothing was said about dis- 
 counts, and perhaps this is "rock- bottom." Lest this notice 
 should cause a rush of trade to Cleveland it should be said that 
 cheap varnish is made elsewhere. In fact, if with New York as 
 a centre and a radius infinity we describe a circumference, the 
 furniture varnish-maker will be found to flourish anywhere within 
 the circumscribed area. 
 
 In justice to the furniture-makers (though justice is about the 
 last thing wanted, or received either, by the users of so-called 
 furniture varnish), it must be said that a large part of the cheap 
 stuff sold under the name is used, not by the furniture men, but 
 by painters of cheap houses for varnishing interior trim, and by 
 makers of cheap mixed paints. It appeals to the latter as being 
 cheaper than linseed-oil. As a house varnish, the name has been 
 displaced largely of late years by that of "hard oil-finish," but 
 the material remains the same, though of course some makers 
 
 327 
 
328 TECHNOLOGY OF PAINT AND VARNISH. 
 
 sell a pretty fair varnish under the latter name, just as some 
 belated individuals or firms make furniture varnish out of var- 
 nish-resins and linseed-oil; but they don't sell much of it. 
 
 Legitimate Use for Cheap Varnish. There are two sides, and 
 usually more than two, to most questions; and the man who 
 makes kitchen chairs says that all the varnish is for is to keep the 
 chair looking fresh until it is sold, and that the best varnish will 
 be scrubbed off the chair as quickly as soap and sand will do it 
 after it reaches the kitchen; all of which is true, and as these 
 chairs are turned out at the rate of a car-load a day in some fac- 
 tories the economy in buying cheap varnish, which is purchased 
 in car-load lots, is a substantial one. The varnish serves some 
 such a use as the practice of leaving the edges of books uncut. 
 It is a guarantee that the goods are not second-hand. The var- 
 nishing of kitchen chairs, by the way, is done by a method which 
 is a refinement of simplicity and economy. Many years ago the 
 makers of agricultural machinery found that they could paint and 
 varnish their apparatus by dipping it in a tank of paint or varnish, 
 properly thinned; but the chair-makers keep a pump in opera- 
 tion, and a stream of varnish falls constantly into a shallow pan, 
 or drained platform, on the floor. The workman holds the chair 
 in this falling stream, turns it about skilfully, then throws it aside, 
 all varnished except the under side of the chair seat, which does 
 not need it. If the chair were dipped this place also would ab- 
 sorb varnish, which would be a waste, and extravagance is a sin; 
 besides, economies like this make dividends, and keep the com- 
 pany out of the hands of a receiver. So it is with many other 
 things: there is no use in using a varnish which will outlast the 
 piece of furniture on which it is put; and the law of the survival 
 of the fittest does not apply to such things as chairs. 
 
 Furniture which does not receive a high polish ought to have 
 as elastic a coating as floor varnish, that is, one containing 12 
 or 15 gals, of oil to 100 Ibs. of resin. Dark woods, such as dark 
 oak and especially cherry and mahogany, should receive a dark- 
 colored varnish, which is made from dark resin. These are cheaper 
 than pale resins of the same kind and are harder and better. Such 
 
FURNITURE-VARNISHING. 329 
 
 a varnish may therefore be of excellent quality and moderate 
 price. Many things will stand a still more elastic varnish, a 20- 
 gallon for instance, such as would be put on interior woodwork. 
 This becomes hard enough to rub in a week or two, and if a rubbed 
 but not polished finish is wanted it is hard enough. It would be 
 too slow for factory work, but it would outlast most furniture. 
 
 Dark Varnishes. The reason why dark varnishes are best on 
 dark woods is that their color enhances the beauty of the wood. 
 It is a dark brownish red, and is transparent. The effect of a trans- 
 parent color is far more brilliant than that of an opaque one, and 
 three or four coats of such a varnish are like a layer of colored 
 glass: it seems as though one could look down into the wood. 
 The more varnish is applied the more pronounced is this effect. 
 
 Brilliance. The larger the proportion of resin the more bril- 
 liant is the varnish, and the richer in depth of color. This is proba- 
 bly one reason why varnishes approaching the type of carriage 
 rubbing-varnish are so much liked on furniture, in spite of their 
 diminished durability. The brilliancy of a varnish, like that of 
 a gem, depends on its index of refraction of light, and this sensibly 
 increases with the increase in the percentage of resin. Therefore 
 in order to get the finest possible effect, on a piano- case for instance, 
 it is necessary to sacrifice durability to an appreciable extent. It 
 it not exactly true that brilliance varies with percentage of resin, 
 for some resins are more capable of imparting this effect than 
 others. An 8-gallon Manila varnish is less brilliant than an 8-gallon 
 Zanzibar. It is a remarkable fact that the index of refraction of 
 a varnish is higher than that of its component parts. It may thence 
 be inferred that this quality is developed in making the varnish, 
 and that skill in the operations will enable one to make a brilliant 
 varnish with a larger proportion of oil than could be used if the 
 operator had less skill; and this is true. A brilliant varnish 
 ought then to be made from the materials which experience has 
 shown to be best, and by a skilful maker, according to a tried 
 .and satisfactory as well as a rational formula. There are so many 
 variables that no two varnishes from different sources are likely 
 to be alike; and it is possible for a maker to produce a varnish 
 
330 TECHNOLOGY OF PAINT AND VARNISH. 
 
 which is actually better for a special use than any one else has 
 made. This again is practically true; but the art of varnish- 
 making is far from stationary, and the best varnish to-day may 
 be superseded next year. 
 
 Filling. It has been said that the finishing of furniture is much 
 like that of carriages. Of course unpainted furniture, which com- 
 prises the greater part of it, receives only priming, filling, and 
 varnish, and the wood-filler used is never lead, but a transparent 
 filler such as silica. The so-called liquid wood-fillers are also 
 used largely on cheap furniture, but nothing good can be said of 
 them. The priming is like all priming, done with linseed-oil; 
 then the wood may be filled with varnish directly. Usually when 
 this is done a rubbing- varnish is used; or a silica filler, such as 
 is used on interior varnished woodwork in houses, may be used. 
 This fills the pores of the wood. Often a colored pigment is mixed 
 with it, the object being to change the color of the wood by filling 
 the pores with color. Sometimes the color of the whole of the 
 wood is changed, as when birch is stained to resemble mahogany. 
 This is done with an oil- and- pigment stain, mixed in turpentine, 
 and applied before the priming; more rarely the wood is treated 
 with a dye. There are a great many dyes which are soluble in 
 alcohol, and some which dissolve in turpentine. These are better 
 than water dyes, as they do not disturb the grain of the wood. 
 Dyeing is necessarily done before anything else. 
 
 Varnishing. When the surface is properly filled it is sand- 
 papered, and is then ready for the varnish. Any good rubbing- 
 varnish will answer, but usually a special rubbing for furniture 
 is employed. The various coats are applied and treated sub- 
 stantially as on carriage-work. The finishing-coat is not usu- 
 ally much different from the preceding ones, because a very 
 elastic varnish is not hard and firm enough for the kind of use 
 furniture receives. It is flowed on with a full, soft brush, and 
 is either left with the gloss, is rubbed to a dull surface, or is pol- 
 ished with rottenstone, as has been described in the chapter on 
 house-painting. 
 
 Polishing. It is a rather common practice for the workman, 
 
FURNITURE-VARNISHING. 33 * 
 
 after he has polished the surface as well as he can with rottenstone 
 or some such powder, to finish by rubbing with the palm of the 
 hand. The reader may notice how the well-varnished hand- 
 rails in business offices get polished by continual handling. This 
 is the sort of finish obtained by hand- polishing, and is the high- 
 est possible finish; also the most expensive, for it is an almost 
 inconceivably laborious and tedious task. A good workman 
 will sometimes spend a day on a surface a foot square. It may 
 be worth while to give here a translation from "The Art of the 
 Painter, Gilder and Varnisher," by Watin, published in 1772. 
 This is regarded as the oldest systematic treatise of any value 
 on the subject. Watin's description of the method of polishing 
 is as follows : 
 
 "To polish varnish is to give it a surface glossy, clear, and 
 smooth, which can never be secured by repeated coats unless 
 we efface the little inequalities which occur. To do this we use 
 pumice and tripoli. Pumice is a stone which has become light 
 and porous because it has been calcined by subterranean fires, 
 and thrown by eruptions into the sea, where it is found floating. 
 Without regarding its form, there are many sorts, various weights,, 
 some gray, some white. Those most esteemed are the coarsest, 
 the lightest, and the purest. It ought to be porous, spongy, with 
 a salt taste. It is brought from Sicily, opposite Mt. Vesuvius, 
 from which it is thrown out. 
 
 "When we wish to use it in powder, it is necessary that this 
 powder should be impalpable, so that it will not scratch the work 
 we are polishing. 
 
 "Tripoli is a light stone, pale in color, inclining slightly to 
 red, which is brought from many localities, in Bretagne, Auvergne, 
 and Italy. It is thought from the lightness of this stone that it 
 has been calcined by subterranean fires. We find two sorts in 
 France. The first and the best is that which is brought from a 
 mountain near Rennes in Bretagne. They find it in beds about 
 a foot thick. It is used by painters, lapidaries, goldsmiths, and 
 coppersmiths to brighten and polish their work. The second, and 
 less valued, comes from Auvergne, near Riom. It will not serve 
 
33 2 TECHNOLOGY OF PAINT AND VARNISH. 
 
 for our uses, but it is used in houses to clean and brighten the 
 kitchen utensils. 
 
 "To polish an oleo- resinous varnish, when the last coat is 
 thoroughly dry, proceed as follows: Pulverize, grind, and sift 
 some pumice, so that you may suspend it in water, and with this 
 saturate a piece of serge and polish lightly and uniformly, not 
 more in one place than another, so as to avoid spoiling the founda- 
 tion. Then rub with a bit of clean cloth moistened with olive- 
 oil and with tripoli in very fine powder. Many workmen use for 
 this pieces of hats; but this always tarnishes the work and may 
 injure the foundation. Wipe it off with a soft cloth in such a 
 way that it shall be bright and show no streaks. When it is 
 dry, polish it with starch-powder or whiting 1 by rubbing with 
 the palm of the hand, and wiping it off with a linen cloth. This 
 last is the operation of polishing. Spirit-of-wine varnishes may, 
 when they are very dry, be polished in the same way, only omit- 
 ting the use of pumice." 
 
 " Vernis-Martin." Watin, as has been said, was the first 
 writer on the subject. He was an artist and a man of science; 
 but long before his book was written, Robert Martin had estab- 
 lished a great reputation, which has lasted until, the present time, 
 as a maker and especially as a varnisher of fine furniture. There 
 were three brothers of the name, one of whom, William, estab- 
 lished himself as a varnisher at Rochefort, but Robert, whom 
 Watin calls "the famous Martin," was at Paris. Watin speaks 
 of "my profound veneration for all who carry the name of Martin, 
 our masters in the art of varnish," and describes the varnish 
 made by melting copal, adding linseed- oil and turpentine, and 
 says: "It is thus that the famous Martin made his beautiful 
 pale oleo-resinous varnishes, which gave him so much reputa- 
 tion." It is worthy of remark that these brothers were carriage- 
 builders, and that their skill as finishers, at a time when every 
 shop made its own varnish, led them into the more lucrative 
 business of fine furniture, in which they became unrivalled. 
 The later editions of Chambers' s Encyclopaedia were published at 
 the time when Martin was producing his work. From this source 
 
FURNITURE-VARNISHING. 333 
 
 we learn that Martin used an oleo-resinous varnish, a mixture 
 of one- third amber and two- thirds copal, with enough linseed- oil 
 to make, in our nomenclature, about a i3-gallon varnish. Diderot 
 and D'Alembert, in their Encyclopaedia, written in Paris about 
 the same time, give the same, only with a larger proportion of oil. 
 Martin's process is thus described by Chambers : 
 
 "The article to be varnished, after having been varnished 
 smoothly, and dried in the intervals, half a dozen times, and 
 suffered to dry thoroughly, must be rubbed with a wet, coarse 
 rag, dipped in pumice-stone powdered and sifted, till the streaks 
 of the brush and all blemishes are removed. When it is per- 
 fectly smoothed, washed, and dried, the coats of varnish are to 
 be repeated, for ten or twelve times, till there be a sufficient 
 body. After having again used the pumice-stone, and washed 
 it off as before, let it be rubbed with fine emery till the surface 
 becomes even and smooth as glass; then with powder of fine 
 rottenstone, till by passing the palm of the hand two or three 
 times over the same place, you discover a gloss equal to that 
 of glass; having dried it clean, dip a rag, or a piece of flannel, 
 in sweet- oil, and rub the surface a few times over, and clear it 
 off with fine dry powder, flour, or the hand; and a piece of fine 
 flannel, dipped in flour, and rubbed over it, when cleared of oil, 
 will give it an excellent lustre. Between every coat of varnish it 
 will be advisable, if the subject admits of it, to set it in a warm 
 oven, or to heat the varnished pieces by stoves." 
 
 Durability of Good Work. That was the way they finished 
 furniture in the year 1750; that is the finish called "vernis- 
 Martin"; and that finish is on that same furniture to-day. Do 
 not say that varnish is necessarily a short-lived commodity. 
 Remember what Xenophon said about the horse's feet, and 
 the counsel of the prophet Isaiah. 
 
 Ancient Practice. But Martin was not the originator of the 
 method of polishing which he practised. It is mentioned by the 
 monk Theophilus in the tenth or eleventh century, who says 
 that varnish is polished with the hand. Going further back 
 we find that Vitruvius, in the first century B.C., says that wain- 
 
334 TECHNOLOGY OF PAINT AND VARNISH. 
 
 scotting is varnished, then rubbed and polished. "Subigendiet 
 poliendi," are his words (book vn, chap. 4), and he also says 
 that this rubbing was done with a powder like ochre interposed. 
 Elsewhere the same author uses, with the same meaning, the 
 words "subactum et bene fricatum." Cicero says that Apelles 
 polished his paintings, but possibly this only refers to his skill in 
 varnishing them, of which mention has already been made; but 
 Nicias, who was a painter of the fourth century B.C., is expressly 
 said by Pliny to have "put his hand to" his work, and to have 
 taken "much care in rubbing" it (book xxxv, chap. 28). Thus 
 we have what seems to be a clear case of handing down a tech- 
 nical method for twenty- three hundred years. 
 
 Refinishing Old Furniture. To refinish old furniture it is 
 desirable to remove first the old varnish, not because old varnish 
 is harmful as such, but because we know nothing about it, and 
 if we are to spend a large amount of work on an article we should 
 be sure about the foundation. The old varnish may be removed 
 by scraping it with steel scrapers or with broken glass, then 
 scouring it with sandpaper; or else we may begin with a paint- 
 remover and carefully take off all the varnish, and immediately 
 wash it off with benzine. This part of the work should be done 
 out of doors, for fear of fire. Then apply a thin varnish. This 
 maybe from a 15- to a 2o-gallon varnish (gallons of linseed-oil per 
 hundred pounds of resin), and should be of good, hard resins, 
 part Kauri and part some hard African resin. This should be 
 thinned with turpentine. Starting with a varnish of ordinary 
 body it is well to add from an eighth to a fifth its volume of tur- 
 pentine, and this mixture, after being well shaken, should stand 
 in a warm room at least two or three months. This may be regarded 
 as essential, for if used at once, although the original varnish may 
 (and must) have been well aged, the mixture will behave in 
 some ways like a fresh varnish. This thin varnish is carefully 
 brushed on in thin coats, plenty of time being given for each to 
 dry and become hard, at least two weeks between coats, unless 
 there is a hot room, with a temperature of at least 130 F., in 
 which it may be set; then the time will be reduced according to 
 
FURNITURE-VARNISHING. 335 
 
 the temperature. Each coat when perfectly dry should be 
 rubbed, at first with very fine sandpaper, but after enough coats 
 have been put on to be sure that none of the water used can 
 reach the wood, powdered pumice and water may be used spar- 
 ingly. The surface should then be washed with clean water, using 
 a clean brush to get it into corners and depressions, and made 
 perfectly dry and warm before the following coat of varnish is 
 applied. Of course all the precautions against dirt, dust, and 
 dampness which can be thought of must be used, and in par- 
 ticular the brushes must be treated with care. Only as much 
 varnish as is to be used at one time should be taken from the 
 can, which should be then immediately stoppered. Any varnish 
 which has been taken out should not be put back, for fear of 
 getting dirt in the can, a thing which would almost certainly 
 happen. The very thin coats secured in this way will make a 
 body of varnish which is much more uniform and homogeneous 
 than if thicker varnish were used; and the reader will easily 
 understand that these are to be repeated until a thickness has 
 been secured great enough to be rubbed to an even, level surface. 
 Then repeat the treatment until enough varnish has been applied 
 to get the desired lustre; after which it should be rubbed and 
 polished. Always remember the intermediate light rubbing 
 between coats, to get a proper adhesion of the successive layers. 
 Flow on the varnish lightly, but smoothly and rapidly, with a 
 fine new brush, and do not brush it too much or it will be full of 
 bubbles, and if you brush it after it has begun to set it will roll 
 up; then all that can be done is to get it off as quickly as possible 
 with a brush wet with spirit of turpentine, and immediately 
 revarnish ; but this should never occur. The successful varnisher 
 works rapidly, with a steady hand, and is not afraid of the varnish ; 
 but he does not use too much. The amateur will do well to go 
 from time to time and watch some good workman. The art, like 
 all arts, is learned from observation and practice combined. 
 The amateur should practise by preparing and finishing experi- 
 mental panels. For this purpose he can buy, in the city shops, 
 
336 TECHNOLOGY OF PAINT AND VARNISH. 
 
 cake-boards of a convenient size, dry and smooth, for a trifling 
 sum; nothing can be better for practice. 
 
 Violin Varnish. Occasionally a mechanic, especially an 
 amateur mechanic, is also an amateur musician; a trouble- 
 breeding combination, which sometimes leads to the construction 
 of violins. There is a belief, so universal that it is probably true, 
 as it is inherently reasonable, among violinists that the varnish 
 on a violin affects its musical quality. It is therefore desirable to 
 use a suitable varnish. Books of recipes usually advise using a 
 spirit varnish, which may be colored to suit; but the writer does 
 riot believe such varnishes were ever used by the great violin- 
 makers. From the nature of the case it is difficult to get samples 
 for examination, but one can occasionally have an opportunity 
 to look carefully at an old violin, and these always appear to have 
 been coated with an oleo- resinous varnish. A varnish expert 
 has shown me an old violin, about two hundred years old, very 
 valuable, which had in one place what appeared to be the original 
 varnish in a layer of considerable thickness; on this surface a 
 long- continued pressure with the finger-nails made a sensible 
 depression, which afterward disappeared. If this varnish was 
 old, and it certainly was, it must have been made with at least 
 35 gals, of oil to 100 Ibs. of resin; and such a varnish would 
 probably last two or three hundred years, possibly several times 
 that, under the conditions in which a valuable violin is kept. 
 Such a varnish could have had little, probably not any, drier in it. 
 The violin was varnished, put in a dry dust-proof cupboard, and 
 left for some months before the next coat was applied. The time 
 was of no consequence, since it is generally believed that a violin 
 must be kept a year or two after it is made before it is ready for 
 use, and such a varnish would by its perfect elasticity not inter- 
 fere with the normal vibrations of the wood; whereas the writer 
 is told by experts that spirit varnishes, which produce simply a 
 layer of dry resin on and in the surface, make the tone of the 
 instrument harsh. As to color, in the first place the old instru- 
 ment-makers made amber varnish. We are accustomed to think 
 of amber as a pale golden-yellow resin, but the sorts used in 
 
FURNITURE-VARNISHING. 337 
 
 varnish-making are dark brownish red, and in melting all resins 
 darken very much; so that amber varnish is very dark in color, 
 so much so that it is unsalable for any ordinary work. It might 
 have had color enough to suit the makers; and it is a beautiful, 
 rich, deep color. Then comes in the matter of age. No one can 
 look at one of these old instruments without feeling that the tone 
 of the color is due to age; the long- continued darkening action 
 of light can never be imitated by a dye. There is besides evi- 
 dence of a historical sort. The great violin-makers lived at the 
 time when the great masters of painting were executing their 
 works in amber and copal varnish, and must have known of the 
 value of these preparations. Eastlake describes a manuscript in 
 the British Museum, dated 1620, written by De Mayerne, who 
 was chief physician to the King of England, and who is well 
 known to have been a man of great and varied technical learning, 
 De Mayerne describes the making of varnish from amber and 
 linseed-oil, as it was experimentally taught him by M. Laniere, 
 who learned it from the daughter of the eminent Florentine 
 painter Gentileschi, whose paints were made with this varnish 
 as the vehicle. This was called the amber varnish of Venice. It 
 was at first turbid but could be settled by mixing brick-dust with 
 it; and De Mayerne says it was commonly used for lutes and 
 other musical instruments. Mrs. Merrifield and others have also 
 collected evidence showing that although turpentine varnishes 
 were unquestionably in common use, yet all the makers of high- 
 priced wares used also varnish made of amber and oil. There 
 is considerable of this sort of evidence, and when taken in con- 
 nection with the fact, which probably most experts would agree 
 upon, that the varnish on these old instruments appears to be 
 oleo- resinous, and the further unquestioned fact that no spirit 
 varnish of such qualities is known to us either experimentally or 
 by tradition, it seems that we are warranted in believing that 
 such varnishes as have been described were the ones used by 
 the more important makers of violins; and that we are to advise 
 the use of a carriage finishing-varnish unless one darker and 
 more elastic can be had. Probably most varnish-makers can 
 
33 8 TECHNOLOGY OF PAINT AND VARNISH. 
 
 supply a 25- to 3o-gallon dark varnish, although they do not ordi- 
 narily sell it unmixed with a harder one. If the writer were to 
 make a special varnish for this use it would be a straight amber 
 varnish, with 35 or 40 gals, of raw linseed-oil. 
 
 To revert for a moment to the subject of furniture, it should 
 be said that the makers of the better class of these goods use very 
 good varnish, not unfrequently thinned with benzine instead of 
 turpentine, for cheapness, which accounts for brush-marks often 
 seen on articles which are left with the natural gloss, and the 
 finish is surprisingly good when we consider the price received for 
 the finished furniture. Such a finish cannot be produced if a very 
 poor varnish is used. 
 
 Brushes. A few words may be here added concerning the 
 proper care of varnish- and paint-brushes. If these are left to 
 dry with the varnish or paint in them they are spoiled; they are 
 to be cleaned thoroughly, or else kept in some liquid which will 
 preserve them. As to what this liquid should be there is differ- 
 ence of opinion; some put the brushes in water, some in linseed- 
 oil, some in varnish, but probably the most use turpentine. What- 
 ever liquid is used the treatment is the same; the brush is not 
 immersed, handle and all, but is suspended in a vertical position, 
 dipping just far enough in the liquid so that it comes, up to where 
 the bristles (or hair) disappear in the binding which unites them 
 to the handle. The brush should not rest on the point of the 
 bristles, as this will injure its shape and, in time, its elasticity, 
 but should be hung up by the handle. Tin boxes for this pur- 
 pose, called brush safes or keepers, are for sale by the dealers. 
 They are tightly covered to prevent evaporation and to keep out 
 dust, and have hooks or other attachments for suspending the 
 brushes. A simple and perfectly good keeper for one or perhaps 
 two brushes may be made by soldering to a tin cup (one without 
 a handle), or a small empty can with the top removed, a wire; this 
 wire stands vertically when the cup is on its bottom, and reaches 
 up about as high as the length of the brush, handle and all. Then 
 bend this wire at right angles, say 2 ins. below the top, so that the 
 bent part may overhang the cup. Make a good-sized hole in the 
 
FURNITURE-VARNISHING. 339 
 
 handle of the brush at a suitable place, so that when it is hung on 
 the bent part of the wire it will hang in the cup, the bristles just 
 clearing the bottom. Then fill the cup with turpentine or oil, so 
 as to wet the bristles; and to keep out dust the whole thing may 
 be lowered into a glass fruit- jar and the top screwed down. In 
 order to more easily lower the apparatus into and draw it out of 
 the jar, it is common to solder a second piece of wire to the first, 
 projecting above it, for a handle. This is a cheap and satisfac- 
 tory arrangement and illustrates the principles on which all brush 
 safes should be constructed. Brushes used in spirit varnishes 
 should not be put in water, but in alcohol, and if a brush is to be 
 put away for a long time it may be washed out with turpentine or 
 benzine (a spirit- varnish brush in alcohol, usually wood- alcohol), 
 and when as clean as it can be conveniently made in this way it 
 may be washed out with soap and water, very thoroughly rinsed 
 with clean water, and dried as quickly as possible. Each brush 
 should be separately wrapped in clean paper, and kept in a dry 
 place. 
 
 As to choice of brushes, that is too large a subject to be treated 
 here. The student will do well to write to some of the brush-makers 
 for an illustrated catalogue, and by studying that, get some idea 
 of the sorts and shapes of brushes in use, after which he may ask 
 advice of the professional painter who is doing the sort of work 
 which interests the amateur. There is considerable room for the 
 personal equation; but all agree that good work cannot be done 
 without good brushes, and the best brushes quickly cease to be 
 good if not kept clean. 
 
CHAPTER XXII. 
 CONCLUSION. 
 
 IT is probable that many of the readers of this book will feel 
 a reasonable interest in knowing something about the former prac- 
 tice of those who made and used the products which have been 
 described. Many references of this sort have been incidentally 
 made. Our knowledge of former applications of the art is not 
 continuous, nor even connected, but the total amount is consider- 
 able; more concerning its decorative and artistic branches than 
 of the technical side. Pliny's Natural History is the great foun- 
 tain of knowledge of such things; much may be learned from 
 Vitruvius and Dioscorides. These writers had access to writings 
 and other sources of information now lost, and no doubt they give 
 reasonably correct accounts of earlier practice, and there is no 
 reason to doubt their accuracy when they describe their own 
 times. Aside from these writers we may only pick up occasional 
 bits from the more ancient writers, introduced incidentally, and 
 to illustrate some other matter. Thus, in Xenophon's " Econo- 
 mist" one of the speakers tells that his wife was at one time in 
 the habit of rubbing white lead into her skin to make her face 
 look white, and then dyeing her cheeks and lips with alkanet to 
 make them red, and adds that she also wore high-heeled shoes 
 to make herself tall; which shows that white lead has been properly 
 valued for twenty- three centuries at least. It is pleasing to be able 
 to add that in this particular case the husband assured his wife 
 that he would love her just the same if she washed her face and 
 put on comfortable foot-gear; and she, being recently married, 
 and knowing that she. was young and pretty anyway, did as he 
 advised, and of course had continued to do so up to the time when 
 
 340 
 
CONCLUSION. 341 
 
 he told of it. It is unnecessary to say that the use of white lead 
 as a cosmetic did not cease; and we find in Cennim's time that 
 not only was paint used, but that one of the branches of the artist- 
 painter's work was to paint, and not only to paint but to varnish, 
 people's faces. Hear him : 
 
 " Sometimes, in the course of your practice, you will be obliged 
 to paint flesh, especially the faces of men and women. You may 
 temper your colors with yolk of egg; or, if you desire to make them 
 more brilliant, with oil, or with liquid varnish, which is the most 
 powerful of temperas. But should you wish to remove the colors 
 or tempera from the face, take the yolk of an egg, and rub a little 
 of it at a time on the face with the hand. Then take clean water 
 that has been boiled on bran, and wash the part with it; then take 
 more of the yolk of egg, and rub it again on the face, and again 
 wash it with the warm water. Do this many times until the color 
 be removed from the face." (Chap. 161.) 
 
 In another chapter he expresses his disapprobation of the prac- 
 tice, saying: 
 
 "It sometimes happens that young ladies, especially those of 
 Florence, endeavor to heighten their beauty by the application of 
 colors and medicated waters to their skin. But I advise you, that 
 if you desire to preserve your complexion for a long period, to wash 
 yourselves with water from fountains, rivers, or wells; and I warn 
 you, that if you use cosmetics, your face will soon become withered, 
 your teeth black, and you will become old before the natural course 
 of time, and be the ugliest object possible. " 
 
 Between Cennini, who described the art as practised in the 
 fourteenth century, and the classical writers there are many 
 authorities of more or less importance. The best known is 
 the monk Theophilus, a varnish formula from whom has already 
 been given; but there are others, both earlier and later. The- 
 ophilus is especially eminent for two reasons: his work is a sys- 
 tematic treatise on various arts, giving simple and intelligible 
 working directions; and there exist several manuscript copies, 
 showing that it was widely known. This is also evident by the 
 extracts from it found in later writers. Among the earlier writers 
 
342 TECHNOLOGY OF PAINT AND VARNISH. 
 
 is Eraclius, who is by some authorities assigned to the seventh 
 century. He was at any rate prior to Theophilus, as has else- 
 where been mentioned; his style indicates an early date. The 
 formula he gives for refining linseed-oil has already been given. 
 It is noteworthy that he says this refined oil was used for mixing 
 with pigments, showing that oil painting was practised in his 
 time. The carriage-painter will be interested to read how Erac- 
 lius recommends preparing the surface of wood, particularly his 
 way of making rough-stuff: 
 
 "First plane the wood perfectly, rubbing the surface at last 
 with shave-grass. If the wood is of such a nature that its rough- 
 ness cannot be reduced, grind dry white lead on a slab, but do not 
 grind it so finely as if you were to paint with it. Then melt 
 some wax on the fire; add finely pulverized tile and the lead 
 already ground; mix together, stirring with a small stick, and 
 suffer the composition to cool. Afterwards, with a hot iron, 
 melt it into the cavities until they are even, and then with a knife 
 scrape away inequalities; and should you be in doubt whether 
 it is advisable to mix white lead with wax, know that the more 
 you mix the harder it will be. The surface being smooth, take 
 more white, finely ground with oil, and spread it thinly, with a 
 brush adapted for the purposes, wherever you wish to paint; 
 then let it dry in the sun. When dry add another coat of color 
 as before, rather stiffer, but not so stiff as to make it necessary 
 to load the surface, only let it be less oily than before, for great 
 care is to be taken never to let the second coat be more fat than 
 the first. If it were so, and at the same time more abundant, the 
 surface would become wrinkled in drying." 
 
 This is a remarkable passage, when we consider that it was 
 written a thousand, and probably twelve hundred years ago. 
 The remark that lead to be used as a filler should not be too 
 fine is evidence of great discernment; and the use of powdered 
 tile for the necessary grit in the rough-stuff is excellent. Wax 
 was used instead of varnish; probably wax may make a good 
 vehicle, but more difficult to apply than the other. It was mixed 
 with a stick; this was a common precaution to avoid getting a 
 
CONCLUSION. 343 
 
 trace of Iron into the compound. Compare Cennini's use of a 
 wooden spatula for scraping the porphyry slab on which colors 
 are ground. Then note that the surface was levelled and cleaned 
 with a knife, exactly as "knifing-lead" is used on wagon-bodies 
 to-day. Shave-grass is the scouring-rush, a species of Equise- 
 tum, and was used as we now use sandpaper, down to quite recent 
 times. It is full of spiculae of silex and is a perfectly good sub- 
 stitute for sandpaper, only less rapid in its action. Evidently 
 the man who wrote this account was skilled in the art, and the 
 art itself was not of a crude sort. Cennini, who wrote six hun- 
 dred years later, gives directions essentially similar. His details 
 are scattered through the book and are not readily copied as a 
 whole. He recommends the use of bone-dust as an ingredient of a 
 filler. He says: 
 
 "For this purpose take the bones of the ribs and wings of 
 fowls or capons, and the older they are the better. When you 
 find them under the table, put them into the fire, and when you 
 see that they are become whiter than ashes take them out and 
 grind them well on a porphyry slab, and keep the powder for 
 use." The translator remarks that this rather singular allusion 
 to the manner of the times shows that the practice of picking 
 bones, and throwing them under the table, was universal. East- 
 lake says that as late as the middle of the nineteenth century 
 Spanish painters saved chicken-bones from the table for a similar 
 purpose. Cennini says that some boards which are to be painted 
 are "primed with chalk mixed with white lead and oil, using the 
 bone-dust as before mentioned." Parchment was also filled in 
 this way. He also describes a filler made of gypsum; but what 
 is more interesting, he describes the use of a guide-coat, by sifting 
 powdered charcoal over the surface of the filler, laying it smoothly 
 with a feather; when the rubbing is afterward completed it will 
 be seen that this guide-coat has disappeared. He says of the 
 surface of the wood: "Let it be made quite smooth; if it be de- 
 faced with knots, or if it be greasy, you must cut it away as far 
 as the grease extends, for there is no other remedy. The wood 
 must be very dry; and if it be such a piece that you can boil in 
 
344 TECHNOLOGY OF PAINT AND VARNISH. 
 
 a cauldron of clean water, after the boiling it will never split. Let 
 us now return to the knots, or any other defect in the smooth- 
 ness of the panel. Take some glue, and about a glassful of clean 
 water, melt and boil two pieces in a pipkin free from grease; 
 then put in a porringer some sawdust, and knead it into the glue; 
 fill up the defects or knots with a wooden spatula, and let them 
 remain. Then scrape them, with the point of a knife, till they are 
 level with the rest of the panel. Examine if there be any nail, 
 or other thing, that renders the panel uneven, and knock it into 
 the panel; then provide some pieces of tin-plate, like small coins, 
 and cover the iron with them. And this is done that the rust of 
 the iron may not rise through the ground. The surface of the 
 panel cannot be too smooth." (Chap. 113.) Note the use of 
 the wooden spatula, to avoid marring the wood, as we now use 
 one in puttying interior woodwork. 
 
 The same writer gives directions for boiling oil, but none for 
 making varnish ; but his description of varnishing pictures appears 
 to be the earliest complete account of the operation, and for that 
 reason deserves reproduction: "You must know that the longer 
 you delay varnishing your picture after it is painted, the better it 
 will be. And I speak truth when I say, that if you would delay 
 for several years, or at least for one year, your work will remain 
 much fresher. The reason for this is, that the coloring naturally 
 acquires the same condition as the gold, which shuns a mixture 
 with other metals; so the colors when mixed with their proper 
 tempera dislike the addition of other mixtures to their own tem- 
 pera. Varnish is a strong liquor, which brings out the color, 
 will have everything subservient to it, and destroys every other 
 tempera. And suddenly, as you spread it over the picture, the 
 colors lose their natural strength, and are powerfully acted on 
 by the varnish, and their own tempera has no longer any effect 
 on them. It is therefore proper to delay varnishing as long as 
 you can; for if you varnish after the tempera has had the proper 
 effect on the colors, they will afterwards become more fresh 
 and beautiful, and the greens will never change. Then take 
 liquid and clear varnish, the clearest you can obtain; place your 
 
CONCLUSION. 345 
 
 picture in the sun, wipe it as clean as you can from dust and dirt 
 of every kind. And varnish it when there is no wind, because 
 the dust is subtle and penetrating; and every time that the wind 
 blows over your picture you will have more difficulty in making 
 it clean. It will be best to varnish it in a green meadow by the 
 sea- side, that the dust may not injure it. When you have warmed 
 the picture and the varnish also in the sun, place the picture level 
 and with your hands spread the varnish well over the surface. 
 But be careful not to touch the gold with it, for varnish and 
 other liquors injure it. If you do not choose to spread the var- 
 nish with your hand, dip a piece of clean sponge into the varnish 
 and spread it over the picture in the usual manner. If you 
 wish the varnish to dry without sun, boil it well first and the 
 picture will be much better for not being too much exposed to 
 the sun." (Chap. 155.) 
 
 It may be well to repeat that the word tempera means the 
 liquid, or vehicle, with which the colors are mixed; modern 
 painters often use it as though it meant only a vehicle for water- 
 colors, but there is no doubt that the word was commonly used 
 exactly as we use the word vehicle. In chapter 161, already quoted, 
 Cennini says: "You may temper your colors with yolk of egg; 
 or if you desire to make them more brilliant, with oil, or with 
 liquid varnish, which is the most powerful of temperas." 
 
 It is evident that in his time it was well known that paint 
 required age, at least a year, to reach a condition of permanence. 
 He devotes several chapters to the subject of painting with linseed- 
 oil; he also describes gold size (doratura), which was made of 
 linseed-oil, boiled on the fire, in which was ground some white 
 lead and verdigris; to this was added some varnish resin, and 
 the whole was boiled all together for a short time. This was 
 applied, as thin a coat as possible, and left until the next day, 
 when it was tried with the finger, and if tacky it was ready for 
 the application of the gold-leaf. He adds that this is made for 
 immediate use; if it is to be kept in stock the verdigris is to be 
 omitted. 
 
 The whole of Cennini' s treatise, which was translated into 
 
346 TECHNOLOGY OF PAINT AND VARNISH. 
 
 English by Mrs. Merrifield (who also translated several other 
 Italian treatises on art of much interest) in 1844, is worthy of 
 careful study; the more so since he wrote at the time when the 
 art of painting was about to receive its greatest advancement. 
 It is said that the method of painting with oil as vehicle was 
 discovered by Jan Van Eyck, a Flemish painter, otherwise called 
 John of Bruges, in 1410. Cennini's treatise was written several 
 years after this date, but he was at the time of its writing an old 
 man, and he expressly says that his methods are those of the 
 middle of the preceding century. It is clear that oil as a vehicle 
 was not first used by Van Eyck; it was known to Eraclius, to 
 Theophilus, and as has been seen in an earlier chapter, was 
 used in England in the thirteenth century. Cennini says it was 
 in common use in Germany ; and it is probable that it was known 
 throughout the whole, or nearly the whole, of the Christian era. 
 Van Eyck no doubt invented something; but it was some improve- 
 ment in materials and processes, not something radically new. 
 All the experts agree that his paintings, and those of his pupils, 
 are made with an oleo- resinous varnish as a vehicle; but he did 
 not invent the varnish, nor was he the first to use it as a vehicle, 
 for Cennini says that varnish is the most powerful of all vehicles. 
 It is possible that he first saw the advantage to be gained by 
 thinning varnish with turpentine; none of the recipes prior to 
 his time speak of this, and it seems to have been the common 
 practice to rub the varnish on with the finger, which would be 
 correct if it were not thinned; it is expressly stated that it will 
 be too thick if laid on with a brush. To adapt it to artistic paint- 
 ing it must have been thinned; the paintings made with it by 
 the great masters show brushwork of the most skilful and deli- 
 cate sort. 
 
 In illustration of this it will be interesting to quote one or 
 two authorities. Gulick and Timbs, whose book was published 
 in 1859, say: 
 
 "Probably every person who sees for the first time a picture 
 by Van Eyck, if not surprised by its antiquated treatment or 
 quaintness of expression, will be very much astonished to find that 
 
CONCLUSION. 347 
 
 the work of the reputed inventor of oil-painting has preserved 
 its brilliancy of tone after the lapse of more than four centuries 
 far better than most pictures executed within the last hundred 
 or even the last fifty years. By 'brilliancy of tone' we do not 
 mean the force and depth, the luscious richness of color and ful- 
 ness of effect which are the principal charms of painting in oil, 
 as exhibited particularly by the Venetian school; but that the 
 color of Van Eyck, though quiet, will still be vigorous and fresh; 
 that it will have limpid transparency, and an almost illusive 
 vacuity of space. In addition to this, it will exhibit an amount 
 of truthful realization of the most minute and exquisitely delicate 
 details which is scarcely ever found united with the same imperish- 
 able durability elsewhere. 
 
 "These characteristics distinguish more or less all the early 
 Flemish pictures; and from persons habitually engaged in restor- 
 ing them we learn that the colors of these pictures are mostly of 
 a harder body than those of a later date; they resist solvents 
 much better; and if rubbed with a file, they show a shining 
 appearance, resembling a picture painted in varnish. Examina- 
 tion of the pictures themselves, and the researches of several 
 learned writers within the last few years, leave us no room to doubt 
 that their durability is attributable chiefly to the vehicle employed, 
 and that the colors were used not simply with oils, but with an 
 oil- varnish of the kind we call 'hard,' or in other words, an 
 oleo-resinous vehicle, such as might strictly be employed as a 
 varnish over a picture when finished." 
 
 The same authors say in another place that "it is probable 
 that varnishes composed of resins dissolved in oil have been used 
 in the most ancient times. Beyond all doubt the composition of 
 varnish was known in Persia, India, and China before the best 
 period of painting in Greece; and it is, then, not to be supposed 
 that the Greeks were unacquainted with this art." 
 
 Another well-known English critic, Sarsfield Taylor, who 
 wrote in the first half of the last century, says : 
 
 "That he [Van Eyck] had, whether he did or did not invent 
 it, a very superior vehicle for painting is unquestionable; and 
 
348 TECHNOLOGY OF PAINT AND VARNISH. 
 
 his pictures, after having been above four centuries painted, are 
 almost in as bright and firm a state as when they first came off 
 the easel. It is feared that his secret has long been lost, and 
 that it was not the ordinary mixture of oils and colors, such prob- 
 ably as was used here [in England] at that time, is very evident; 
 for none of our early oil-color pictures can stand any competition 
 with' those of John and Herbert Van Eyck for clearness of light 
 and shade, brightness of hues, or state of preservation; it has all 
 the same advantages over works of the French school painted 
 two or three centuries ago." 
 
 It may well be noted in connection with the numerous formulas 
 for making varnish known in times earlier than that of Van 
 Eyck, that Facius, an Italian historian contemporary with that 
 painter, says that Van Eyck was familiar with the writings of 
 the ancients. 
 
 Eastlake relates that the English landscape painter, Fair- 
 field, had learned the use of oleo- resinous varnish as a vehicle 
 from the Dutch painter Van Strij, who was a successful imitator 
 of Cuyp, and though not a contemporary of that painter was 
 well acquainted with his methods; and he assured F airfield that 
 hard copal or amber varnish was Cuyp's ordinary medium. This 
 agrees with the remarkable hardness of Cuyp's paintings; and 
 this seems to be a consecutive tracing back of this vehicle for a 
 period which now amounts, if we reckon to the elder Cuyp, 
 whose processes appear to be the same as those of his more famous 
 son, to nearly or quite three hundred years. Rembrandt is said 
 by his contemporaries to have painted with amber varnish; and 
 Sir Joshua Reynolds, who was always experimenting with vehicles 
 and pigments, it is said that he destroyed pictures by the older 
 masters to get the materials for analysis, and was certainly 
 competent to form a correct opinion, said that Rubens used oleo- 
 resinous varnish as a vehicle. Leonardo da Vinci, certainly one 
 of the greatest of Italian painters, is commonly said by con- 
 noisseurs to have used varnish as a vehicle; and about 1515 he 
 was commissioned to paint a picture for Pope Leo X. Vasari 
 relates the story in his Lives of the Painters. It seems that 
 
CONCLUSION. 349 
 
 Da Vinci had recently come to Rome. As was common practice 
 among artists he prepared his own materials, and not having yet 
 had time to supply himself, he began first to make them. Leo 
 inquired the cause of the delay and was told that the painter 
 was getting oils and resins to make his own peculiar varnish. 
 This the Pope criticised, thinking that varnish was the last thing 
 needed, as was indeed the case with distemper painting. The 
 painter became angry and left the court. 
 
 Various authorities might be quoted to show that the use of 
 oleo- resinous vehicles, which rendered a final varnish needless, 
 was common still in Flanders in the seventeenth century. 
 
 As we come down to more recent times it becomes, of course, 
 easier to find more material; but enough has been said to 
 satisfy the reader that the extreme durability of the work of 
 the great masters of painting was connected with their use of 
 amber varnish or its equivalent. If the reader will remember 
 what has also been said in a former chapter of the value of a 
 white background and the use of semi- translucent paints over it, 
 and will then note the readiness with which such paints may be 
 made, even with very opaque pigments, by mixing them with 
 varnish, and the difficulty of doing this with the vehicles in earlier 
 use, even with oil, it will be plain that this vehicle added so greatly 
 to the brilliancy of pictures that a new era was opened; men of 
 artistic taste were irresistibly attracted to this new art, and so 
 arose the great revival and renewal of the painters' art. If it be 
 said that the same reasons exist now and that nevertheless the 
 use of varnish has again given place to oil, the answer is, first, 
 that the early painters had very few colors, and to get intermediate 
 effects painted a thin color over one already laid on, while modern 
 painters have an almost indefinite variety. Sir Humphrey Davy, 
 who gave great attention to this matter, states that "the earlier 
 Grecian masters used only four colors, namely, Attic ochre for 
 yellow, sinopis for red, the earth of Melos for white, and black." 
 Ivory-black is said to have been invented by Apelles. Boschini 
 relates a remark of Titian, that whoever would be a painter should 
 be well acquainted with three colors, and have perfect command 
 
350 TECHNOLOGY OF PAINT AND VARNISH. 
 
 over them, namely, white, red, and black. Cennini recommends 
 only twelve pigments, ten of which could be used in oil; he knew 
 no brown pigment, though modern painters have fifteen or twenty 
 of this color. The second answer is, that in fact, so far as we can 
 judge, modern paintings do not equal those of the masters of the 
 middle ages in permanence. As has been before remarked, the 
 unequalled facility with which oil can be used has been the cause 
 why it has displaced varnish. For glazing colors some painters 
 now use a mixture of mastic varnish and boiled linseed-oil, called 
 megilp. This has been used for many years; but it was known 
 and discarded by the artists who lived before Van Eyck. In 
 Vasari's life of Antonello da Messina he informs us that the 
 painter, when seeking for a vehicle, had tried the experiment of 
 mixing liquid varnish with their oil colors, and that the result had 
 been unsatisfactory. The translator of Cennini says: "It is some- 
 what curious that the painters of the nineteenth century should 
 have revived and practised, as a new invention, what those of the 
 fourteenth century had tried and rejected; and more extraordinary 
 still, that, unwarned by experience, they should continue to use 
 it, in spite of the awful gashes and cracks that disfigure the pic- 
 tures painted with this vehicle." 
 
 The literature of paint and varnish as now technically used 
 really begins in the last part of the eighteenth century; the first 
 notable treatise is that by Watin, published in 1772. This author 
 was familiar with the art of varnish-making, and gives explicit 
 directions for making oleo- resinous varnishes, spirit varnishes, 
 and those made by dissolving resins in the essential oil of turpen- 
 tine. The book passed through many editions; it contains direc- 
 tions for executing a great variety of work in painting, varnish- 
 ing, and gilding. A general idea of Watin's knowledge of var- 
 nish-making may be had by reading his precepts, or general prin- 
 ciples, which he made for the guidance of his readers. 
 
CONCLUSION. 351 
 
 ON THE COMPOSITION OF OLEO-RESINOUS VARNISH. 
 
 I. 
 
 Copal and amber are the two principal substances used in 
 oleo- resinous varnish; each of these two materials combines solid- 
 ity and transparence, which are the primary qualities of varnish. 
 
 II. 
 
 Copal and amber are not used together; copal, being whiter, 
 is reserved for the more transparent varnishes; amber, a harder 
 resin, serves for gold varnish or to make varnish to be used over 
 dark colors. 
 
 III. 
 
 Amber and copal can be dissolved, as has been already said, 
 in oil, but we believe it is a better plan to melt them alone over a 
 naked fire. By so doing, they are less liable to be scorched and 
 are always whiter and more clear. When we dissolve them in oil 
 they darken, for as they are difficult to dissolve it is necessary to 
 have a very violent fire. 
 
 IV. 
 
 The oil which is employed either to dissolve or to mix with 
 the melted resin ought to be perfectly clarified and as pale as 
 possible. It is not permitted to use any oil in making varnish 
 which is not siccative, otherwise it would never dry. 
 
 V. 
 
 To dissolve amber or copal it is necessary to cook them alone 
 and dry; and when they are well melted, which is known by their 
 fluidity, we are to add the proper quantity of prepared fixed oil. 
 
 VI. 
 
 Never put several ingredients together to dissolve or melt, 
 since the more manageable will be first liquefied and will be scorched 
 before those which offer more resistance will have arrived at the 
 like condition. 
 
3$2 TECHNOLOGY OF PAINT AND VARNISH. 
 
 VII. 
 
 To melt the resins it is proper to have a glazed earthen pot 
 which can be covered with a lid. This must not be full because 
 we are to add to it the oil and spirit of turpentine, and there must 
 be room besides for it to swell up without overflowing. 
 
 VIII. 
 
 Set the glazed earthen pot containing the resin over a naked 
 fire of glowing charcoal which does not blaze, for fear of setting 
 fire to the contents. 
 
 IX. 
 
 In fusing the resins avoid heating them too much. They will 
 turn black and lose their valuable qualities; too much scorched 
 they will be of no use. 
 
 X. 
 
 We recognize that the resin is in the proper state of fluidity to 
 receive the oil when it offers little resistance to the iron stirring- 
 rod and runs off from it drop by drop. 
 
 XI. 
 
 When we are ready to incorporate the oil with the melted resin, 
 it ought to be very hot, almost boiling, but it ought to be well 
 purified and clarified. It is necessary to heat it only at the moment 
 when it is to be used. If it is used cold it will dissolve less often 
 melted resin, and by cooling will harden it; while if both are of 
 the same temperature they will be rendered more compatible. 
 
 XII. 
 
 Do not add the prepared oil until the resin is completely 
 fluid, ready to receive it, which will occur only after it has boiled 
 up several times. In adding the oil, turn it in little by little, 
 stirring it always with the spatula. Let the mixture finally be 
 united by boiling it up several times over the fire. 
 
CONCLUSION. 353 
 
 XIII. 
 
 When the oil appears cooked with the resin, take away the 
 pot from the fire, and when it has partly cooled and is only warm 
 turn in, with constant stirring, the spirit of turpentine, which ought 
 to be in larger quantity than the oil. If, when the spirit of tur- 
 pentine is added, the oil is too hot, the spirit will take fire and 
 burn the varnish. 
 
 XIV. 
 
 Skilful manipulators, when they wish to make a very fine 
 varnish of copal or amber, do not wait until all the resin is melted. 
 When the greater part is boiling and appears to rise up and 
 then settles down, then they add the oil, which combines with the 
 part of the resin which is melted and does not dissolve that which 
 is not yet fused. By this means the copal and amber are not 
 subjected to a too prolonged heat and are, therefore, more clear 
 and more beautiful. If, when the oil is incorporated, the oper- 
 ator tries to dissolve the unmelted resin, then, as I have already 
 said, he darkens the varnish. 
 
 XV. 
 
 The varnish being made, it is necessary to be careful to strain 
 through a cloth, to remove any foreign matter which may be in it. 
 If any unmelted pieces are found these must not be put back on 
 the fire with the melted resins, as this would result in making 
 the varnish dark in color. 
 
 XVI. 
 
 You may put the pieces of unmelted gum by themselves into 
 the earthen pot and recommence to liquefy them, afterward 
 adding oil and spirit of turpentine; but you may be sure that the 
 second varnish will not be as white as the first, for the reason 
 that the resin has been impregnated with oil and will turn dark 
 in cooking. If one does not wish to use up immediately these 
 pieces of copal or amber, and if one has the time to let them dry 
 in the sun and separate them from their oil, they may subse- 
 quently be used as though they had never been treated. 
 
354 TECHNOLOGY OF PAINT AND VARNISH. 
 
 XVII. 
 
 Let the varnish settle at least twice twenty-four hours to 
 clarify it. The longer it stands the more it will clear and it does 
 not clear so quickly as spirit- of -wine varnish. 
 
 XVIII. 
 
 Oleo-resinous varnish, if properly kept, becomes more beauti- 
 ful, but grows thicker. It is necessary, when one is ready to use 
 it, to mix with it a little spirit of turpentine and to heat it for a 
 time in a water-bath. This clears it. 
 
 XIX. 
 
 When we wish to make fine pale oleo-resinous varnish, it is 
 necessary each time to use a new melting-pot, for usually the 
 action of the fire cracks the glaze, and the oil and turpentine 
 enters these cracks and penetrates the earthenware. Then when 
 we again attempt to melt resins, these liquids which have been 
 absorbed ooze out and burn and mix with the resins and blacken 
 them. Those who do not use this precaution will be much 
 surprised to not have the same result as before, and t will not 
 know to what to attribute this accident. 
 
 XX. 
 
 In fine summer weather these varnishes ought to dry in twenty- 
 four hours. In the winter the varnished objects are usually put 
 in ovens or in a room where there is a hot fire. They dry more 
 or less rapidly according to temperature. 
 
 XXI. 
 
 The oil, as has been observed, is incorporated with the resins 
 only to preserve them in a fluid condition and prevent them from 
 coagulating; but as the oil is thick, the spirit of turpentine ren- 
 ders it more freely flowing, more easy to spread and to dry. 
 
 XXII. 
 
 It is necessary to use spirit of turpentine, without which the 
 varnish will never dry. The quantity is commonly double that 
 
CONCLUSION. 355 
 
 of the oil. We use less turpentine in summer because the oil, 
 drying more quickly by the heat of the sun, becomes thick more 
 rapidly and the work dries from the bottom. On the other 
 hand, in the winter, when the heat is less, and often only arti- 
 ficial heat, we put in less oil so that the varnish may dry more 
 quickly, but we also add more spirit of turpentine, which evapo- 
 rates more easily. 
 
 XXIII. 
 
 The less oil there is the harder and quicker drying is the 
 varnish; as the oil is increased it loses its body, but it spreads 
 more easily. 
 
 XXIV. 
 
 A very large proportion of oil in a varnish hinders its drying^ 
 and if there is too little, it cracks. It is not possible to deter- 
 mine the precise quantity. The ordinary proportion is, to incor- 
 porate with each pound of copal or amber from a quarter to a half 
 pound of oil. 
 
 GENERAL PRECEPTS ON THE MAKING OF VARNISH. 
 
 I. 
 
 All varnish ought to contain material which is durable and 
 brilliant. These two qualities constitute the beautiful and the 
 good in varnish. It ought to be very quick- dry ing, hence it is 
 necessary that the liquids which are employed to dissolve the 
 materials should be perfectly dehydrated and siccative 
 
 II. 
 
 All bitumens and resins suitable for making varnish, if they 
 are heated too much, will become burnt when they are brittle 
 and may be reduced to powder, and when we try to polish them, 
 we find they are worthless. 
 
 III. 
 
 It is necessary to clean, select, and break into little pieces all 
 the resins used in making varnish but not to reduce them to 
 
356 TECHNOLOGY OF PAINT AND VARNISH. 
 
 powder before melting, because the powdered resin will stick 
 to the sides of the interior of the vessel and very easily become 
 scorched. It is most easily melted when it is in little pieces. 
 
 IV. 
 
 It is forbidden by various regulations to make varnish in the 
 middle of towns. This is a prudent policy. The Tesins are so 
 combustible, they are able to cause serious fires; besides which, 
 their odor is so penetrating that it is noticeable at a distance and 
 is disagreeable to the neighborhood; so that varnish-makers are 
 obliged to work outside the city limits and in the country. They 
 are not so particular in regard to spirit- of- wine varnishes, yet they 
 are not less dangerous. It is important that one's attention should 
 be constantly on the work, and to take every precaution against 
 accident. It is necessary to make all solutions by day and to 
 avoid artificial light. If the operator, working in an obscure 
 place, should wish to bring a wax taper 'or a lighted candle near 
 the work, the vapor of the resins, the spirit of wine, or the oil 
 may take fire and cause a conflagration. It is necessary, in case 
 of accident, to have several sheepskins or calfskins, or cloths 
 folded in several thicknesses, always kept wet, to throw over the 
 vessels which contain the varnish materials, to smother the flame. 
 
 V. 
 
 The action of fire serves to combine the liquids and resins 
 which, by their union, make varnish, but it is not possible to 
 determine the time during which the heat must be applied; that 
 depends on the tensity of the fire, which should be kept perfectly 
 steady, neither increasing nor diminishing. 
 
 VI. 
 
 If the workmen should get burned, in order to prevent blisters, 
 the wound should be at once wet with spirit of wine, or wrapped 
 with a compress wet with spirit of wine, then cover the wound 
 with a plaster of olive-oil and litharge which have been rubbed 
 together until they become a smooth pulp. 
 
CONCLUSION. 357 
 
 VII. 
 
 Varnish is sometimes made of various colors. The Dictionnaire 
 Economique gives numerous recipes, but such varnishes are less 
 fine than the others. The substances which are put in to color 
 them change their character and, not dissolving, always form a 
 sediment which dulls the surface. It must, therefore, be remem- 
 bered that it is much better to apply a suitable color first and 
 afterward put on the varnish, which, if it has been well made, 
 will not at all change the tone of the colors. 
 
 VIII. 
 
 A general rule, which should never be forgotten, is to ahvays 
 keep perfectly clean and well stoppered the vessels which hold 
 the materials from which the varnish is to be made as well as 
 those in which it is to be kept, for nothing evaporates so easily as 
 a varnish; and a varnish which evaporates becomes thick and 
 darkens and changes the colors over which it is used. 
 
 IX. 
 
 When the varnish is made, it is carefully purified, as much 
 as is possible, from all dirt and dust, by passing it through a 
 strainer of silk or fine linen, and when it is purified, care should 
 be taken to close the bottle which contains it, for fear that par- 
 ticles of dust may fall into it. 
 
 X. 
 
 The nature of the object to be varnished should determine the 
 kind of varnish to be used. If it is to be exposed to the weather, 
 it is necessary to use an oleo-resinous varnish. If, on the con- 
 trary, it is to be kept within doors, cared for, and preserved in 
 the interior of the house, then we may use spirit-of-wine varnish, 
 which, while it is brilliant, gives off no odor, dries quickly, and is 
 durable as long as it is not too much exposed to the air and the 
 sun. As for varnish of spirit of turpentine, it is, except such as 
 are used on paintings, hardly deserving the name of varnish. 
 Those which are called so are in reality commonly composed of 
 
358 
 
 TECHNOLOGY OF PAINT AND VARNISH. 
 
 common resins which will dissolve together and of which the 
 turpentine is the foundation. 
 
 XI. 
 
 Oleo- resinous varnishes endure easily the heat of the sun, 
 because the amber or the copal which they contain are too durable 
 to be changed. Sandarac, on the contrary, which is the base 
 of spirit-of-wine varnish, is affected by the sun and cannot long 
 resist it when made into a varnish. This one often sees in the 
 heat of summer, when the spirit-of-wine varnish on the interior 
 of rooms suffers decomposition and gives off an odor, as if it 
 were not well made. 
 
 XII. 
 
 Varnish is made in glazed earthen pots which are commonly 
 changed at each operation, for a reason given elsewhere. 
 
 This illustration represents a varnish-maker's furnace, date about 1778; from 
 the thirteenth volume of the Oeconomische Encyclopedic. The fuel was charcoal. 
 The resin was melted and the varnish made in the flask. 
 
 The next book of importance was the "Painters' and Var- 
 nishers' Guide," published in Geneva in 1803, and written by 
 
CONCLUSION. 359 
 
 P. F. Tingry, a chemist and scientific man of some note. He 
 was a member of the Society at Geneva for the Encouragement 
 of the Arts, Agriculture, and Commerce. As this society desired 
 that a methodical description of the art of varnishing should be 
 a part of their publications, and as Tingry had lectured both 
 publicly and privately on the subject, they requested him to 
 undertake the work. His book brought it up to about a third of 
 a century later than the treatise of Watin. It passed through 
 numerous French and at least two English editions. He notices 
 the fact that formulas for making both varnishes and colors had 
 long been known, and asserts that Watin was the first to system- 
 atically weed out the useless and explain the sequence of the 
 valuable ones, thus establishing a method of study which sub- 
 sequent writers might enlarge and perfect. He gives twenty-nine 
 varnish formulae. These are divided into five classes, or genera, 
 of which the first includes three kinds, called drying- varnishes 
 made with alcohol. Two contain only mastic, sandarac, and 
 Venice turpentine for solid ingredients; the third contains a 
 small amount of "powdered copal of an amber color," and pre- 
 viously melted. In all cases these are made in batches of about 
 one -quart, in glass flasks immersed in hot water, stirred contin- 
 ually with a stick, and cleared by settling with powdered glass. 
 He mentions the use of camphor as an assistant to solution. The 
 second genus includes seven varnishes, also having spirit of wine 
 as the solvent, made in the same quality and manner as those 
 already described, but less drying than the first genus, by which 
 he means less hard and more flexible. The various ingredients 
 are sandarac, elemi, anima, rosin, shellac, Venice turpentine, 
 mastic, benzoin, copal, or amber (not all these resins in any one 
 varnish, but three, four, or five), camphor to assist the solution, 
 and in some of them coloring-matter was added, the list being 
 dragon's-blood, sandalwood extract, saffron, gamboge, and ex- 
 tract of canna indica. In all cases he uses 10 or 12 ounces of 
 resinous matters to a quart of alcohol, or about half as heavy a 
 varnish as our modern standard shellac. 
 
 This third genus of varnishes has spirit of turpentine for a 
 
360 TECHNOLOGY OF PAINT AND VARNISH. 
 
 solvent. The resins are mastic, which is always used in this class, 
 so is Venice turpentine; sandarac and seed- lac are also used, and 
 coloring-matter as before. These varnishes are for application 
 to finished paints, or for metals and wooden boxes. The batch 
 is about one quart, and is made in the way already described. 
 There are six of these formulae. 
 
 The fourth genus, six in number, is based on copal, by which 
 Tingry meant apparently a soft copal like Manila. At all events, 
 it was wholly soluble in ethylic ether ("sulphuric" ether), and 
 partly soluble in alcohol. One of the solvents in this class is 
 essential oil of lavender. The powerful solvent qualities of this 
 liquid are believed to be due, at least in part, to a camphor which 
 it contains. He also- added about 2 per cent, of camphor to the 
 oil of lavender. The principal solvent or diluent was spirit of 
 turpentine. It is worth noting that one of these varnishes was 
 suitable for the varnished wire gauze used in ships instead of 
 glass. 
 
 The fifth genus comprises what he calls fat varnishes, or oleo- 
 resinous varnishes. The materials which enter into their com- 
 position are copal, amber, prepared linseed-oil, nut- and poppy- 
 oil, and essential oils, especially spirit of turpentine. In all cases 
 the resin was first melted and the oil afterward added to it in 
 the usual manner. Four to eight ounces of resin made a batch. 
 Seven formulae are given, only five of which are of true oleo- 
 resinous varnishes: one is a gold size, and one is caoutchouc 
 dissolved in oil. His own preference was for varnishes of the 
 fourth genus; but he admitted that for durability oleo- resinous 
 ones must be used. 
 
 He gives a long and interesting discussion of the effect of light 
 on spirit of turpentine, showing that it increases its specific grav- 
 ity and its solvent powers, qualities now thought to be due to the 
 action of oxygen, the possibility of which he suggests. 
 
 TINGRY' s FURNACE FOR MELTING RESIN. 
 
 It is built of fire-clay. The cover of the inner tube, C, is of 
 iron, which may be luted to the clay or porcelain tube. The net 
 
CONCLUSION. 
 
 361 
 
 D is of brass wire, woven to a brass ring which rests in the coni- 
 cal upper extremity of the tube. The upper part of the furnace 
 is filled with charcoal; the copal, in pieces not larger than a nut, 
 on the wire net. The lower end of the tube C is immersed about 
 i in. in water contained in a suitable capsule F\ or this capsule 
 
 mBHIHIIIIII! ~~H 
 
 may contain oil, kept hot by setting the capsule on a plate of hot 
 iron, in which case the melted resin will be at once dissolved by 
 the oil, which will also collect the products of distillation, or such 
 parts as can be liquefied. The laboratory furnace, A B, is 
 17^ insc in total height, the interior diameter at the top 9^ ins., 
 and at the bottom 7 ins. G is a larger furnace, built on an iron 
 tripod. But the inventor says: "I must always insist on the ad- 
 vantage of employing not more than 6 ounces of resin in one 
 operation." 
 
 The next author is M. Tripier-Deveaux, who published in 
 1845 a "Theoretical and Practical Treatise on the Art of Varnish- 
 making." His book has the great merit of having been written 
 by a man engaged commercially in the manufacture and sale of 
 varnish, and he therefore knew what varnishes were in demand 
 and in successful use. He devoted his time chiefly to varnishes 
 composed of resins dissolved in alcohol and in turpentine, and 
 contributed considerably to the accuracy of our knowledge of 
 these; but he also made oleo- resinous varnishes, in which branch 
 he shows most advancement in preparing oil with driers. 
 
 In 1866 M. Henri Violette published a treatise, entitled a 
 " Practical Guide for the Manufacture of Varnish," valuable 
 
362 TECHNOLOGY OF PAINT AND VARNISH. 
 
 from a historical point of view, but apparently not the work of 
 a practical manufacturer. He gave much more careful descrip- 
 tion of the various resins, etc., than any of his predecessors, and 
 collected what chemical and other scientific information was at 
 that time accessible to him. His detailed accounts of the prepa- 
 ration of drying oils with litharge and oxide of manganese are 
 of interest; but evidently at that time the making of oleo-resinous 
 varnishes was not in a very advanced state in France. We know 
 from other sources that these varnishes were more extensively 
 made in England at that time, and probably also in the United 
 States; but we have no books of importance on the subject in 
 English, as the English and American makers tried to keep their 
 processes secret. 
 
 In Germany the most notable early treatise was that of Dreme, 
 a book similar to those of Watin and Tingry. It was published 
 in 1821 at Brunn. An interesting book on encaustic painting 
 by Fernbach (" Die enkustische Malerei ") was published at 
 Munich in 1845. 
 
 Mention should also be made of a paper which received a 
 gold medal from the Society of Arts, London, published in Vol. 49 
 of their Transactions, by Mr. J. Wilson Neil, which gives a de- 
 tailed account of the actual operation of melting the resin and 
 combining it with oil and turpentine. It is interesting from a. 
 historical point of view, but contains nothing essentially novel, 
 and very little that is practised now. It is to be found, practically 
 in full, in Ure's "Dictionary of the Arts and Sciences," which is to 
 be found in almost every collection of technical books. 
 
 Within the last half-century several books on varnish have 
 appeared, and some, of notable merit, on pigments. Some of 
 these have been mentioned in preceding chapters of this book. 
 
 One of the most serious difficulties of the subject is that in 
 different countries different names are given to the same resin, 
 and the same name to different resins. Violette, for instance, 
 describes under the name of East Indian Copal the resin now 
 known in England and America as Zanzibar, and he describes 
 under the name Zanzibar a soft, "semi-hard" resin of unknown 
 
CONCLUSION. 363 
 
 origin. Animi is a name the value of which can never be known 
 except from the context; and even when we speak of a well- 
 known resin like Kauri it is difficult to properly describe the 
 grade. What is known in the New York market as No. i Kauri 
 is decidedly inferior to the resin sold under the same name, for 
 about one-third the present price, twenty years ago. Some of 
 the fine African resins formerly used are now rare, and on the 
 other hand new resins are appearing on the market every year. 
 For these and other similar reasons it is useless to give formulae 
 for making particular varnishes. Every maker is gradually chang- 
 ing his formulas continually, and must if he keeps up with the 
 improvements of the art. 
 
 The writer has had some thoughts of giving an outline of tne 
 chemical work which has been done on varnishes, but it would 
 be of little use. Chemists who are interested have usually access 
 to the original papers, published in the various chemical journals. 
 Methods of analysis of varnishes and paints are rapidly changing, 
 and are still very unsatisfactory. Up to the present time the 
 ingenuity of the manufacturer has been able to keep ahead of the 
 skill of the analyst. It is to be hoped and I am glad to believe 
 that there are grounds for hope that our analytical methods 
 will be greatly improved within a few years. At present every 
 manufacturer depends finally on time and exposure tests; but 
 let a warning be given that paints and varnishes may only be 
 tested under fair conditions, and that the best materials will 
 sometimes give bad tests. If we are testing several varnishes of 
 the same class, and keep repeating the tests often enough, we 
 will finally get a trial in which the best varnish shows the poorest 
 result. The explanation of this is that we do not know, or can- 
 not control, all the conditions of the test. All this is equally 
 true of paints and varnishes. 
 
 In writing on this subject it is hard to tell what to put in 
 and what to leave out. If the writer expresses too copiously 
 his own experience, the technical details will interest only those 
 who are themselves engaged in like work, and who may be pre- 
 sumed to have as much knowledge of the subject as himself; 
 
364 TECHNOLOGY OF PAINT AND VARNISH. 
 
 and these observations will in a few years be out of date in any case. 
 The general principles involved, and the established and approved 
 methods, are the essential things. These may be comprehended 
 by those who will give the subject the attention it deserves. 
 Painting is an Art Whether our interest in it is as a fine art or 
 an industrial art, the technical principles are the same; and it 
 is as old as civilization itself. Its practitioners can show an un- 
 broken descent from "the early dusk and dawn of time." They 
 may feel, like all who dignify an art by faithful and intelligent 
 service, that 
 
 "The gods hear men's hands before their lips, 
 
 And heed beyond all crying and sacrifice 
 Sight of things done and noise of laboring men." 
 
INDEX. 
 
 PAGE 
 
 Aetius 35 
 
 Albert! ig 
 
 Alcherius 14 
 
 Alessio 3 6 
 
 Allegheny pipe line 277 
 
 Apelles 23, 334 
 
 Aristotle 122 
 
 Asphaltic cement 184 
 
 Asphaltum : 109, 266 
 
 coating on pipe 266 
 
 Architectural metal work 194 
 
 Bacon, Lord 24 
 
 Banana liquid . 117 
 
 Barium carbonate 121, 311 
 
 " sulphate 121, 311 
 
 Berenice 27 
 
 Boiled oil 40, 89 
 
 Boneblack 131 
 
 Boston Stone 138 
 
 Brick-dust 18, 155 
 
 Bridge-painting 195 
 
 Brilliance of varnish 329 
 
 Bromine, action of 46 
 
 Brushes 338 
 
 Brush-safe 338 
 
 Burning-off paint 325 
 
 Burgundy pitch 107 
 
 Bunghole oil 41 
 
 Callimachus 27 
 
 Calomino , 30 
 
 Cambridge pipe line 277 
 
 Caneparius 19 
 
 Carriage-painting 301 
 
 365 
 
3 66 INDEX. 
 
 PAG2 
 
 Catullus 27 
 
 Cellars, painting 323 
 
 Cennini 14, 31, 123, 341, 343, 350 
 
 Chairs, varnishing 328 
 
 China wood-oil 85 
 
 Chinese blue 126 
 
 Chinese lacquer 146 
 
 Chrome green 125 
 
 " oxide....' 126 
 
 *' yellow 124 
 
 Cicero 23, 24, 334 
 
 Coal-tar coatings, modern 261 
 
 Coating steel at the mill . . 204 
 
 Cobalt 37 
 
 " blue T 126 
 
 Collodion 113 
 
 Colophony 16, 95 
 
 Copal 29 
 
 Copper on ships' bottoms 290 
 
 Copper oxide paint 292 
 
 Copper soap paint 294 
 
 Corrosion of iron, conditions which promote 181 
 
 Corrugations of pipe coating 270 
 
 Cost of paint 251 
 
 Cost of painting 248 
 
 Covering capacity of paint (area) , 249, 314 
 
 Covering power of paint (opacity) 142 
 
 Crevices, how treated 206 
 
 Cuyp 348 
 
 Damar..., 105, 140, 300 
 
 Damar enamel paint 140 
 
 Dark varnishes 329 
 
 Davy, Sir Humphry 349 
 
 Dead-oil of coal-tar 264 
 
 De Mayerne MS 37, 337 
 
 Diminished flow of water in rusty pipe 259 
 
 D'Incarville's memoir 146 
 
 Dioscorides 23, 36, 340 
 
 Distemper 4, 311 
 
 Dreme 362 
 
 Driers 33, 40, 88, 312 
 
 " bad effects of 92 
 
 ' ' from soap 90 
 
 " low-temperature 92, 312 
 
 " self-drying 93 
 
INDEX. 3 6 7 
 
 PAGE 
 
 Eastlake 25, 122, 337, 348 
 
 Economy in painting 248 
 
 Egyptian varnish r 7, 8, 21 
 
 Elastic-undercoat cracks 303 
 
 Electron 29 
 
 Elemi 107 
 
 Enamel coatings in U. S. Navy 278 
 
 " on bridge-work 279 
 
 paint . 140, 248 
 
 ' ' for steel structures 248 
 
 Encaustic painting 4, 25 
 
 Enzymes 178 
 
 Eraclius 37, 342 
 
 Eustathius 28 
 
 Facius 348 
 
 Fair field. ... 348 
 
 Ferment of Japanese lacquer 175, 178 
 
 Fernbach 362 
 
 Fillers. ....... 315 
 
 Finishing varnish 309 
 
 Fireproof paints 322 
 
 Fish-oil 134 
 
 Floor finishing 318 
 
 Floor-wax 4, 319 
 
 Fortunato 30 
 
 Frankincense n, 25, 29 
 
 Furniture-varnishing 327 
 
 Galen 23, 36 
 
 Gentileschi . . 337 
 
 Glassa 13, 14, 29 
 
 Glue 8 
 
 Grease paints 6 
 
 Greek pitch '. . . . . 16, 17 
 
 Grinding Japan 135 
 
 Guide-coat 307, 343 
 
 Gulick and Timbs 346 
 
 Hippocrates 23 
 
 House-painting 311 
 
 Incense n 
 
 Influence of weather on painting 254 
 
 Iron in nature 180 
 
 Iron oxides 128 
 
 " " permanence of 129,130 
 
INDEX. 
 
 PAGE 
 
 Ivory-black 131 
 
 Jacobus de Tholeto 15 
 
 Japan 87, 91, 312 
 
 " grinding 93, 135 
 
 John.J. F 7 
 
 Juniper resin n, 15, 19 
 
 Karabe 29 
 
 Kodak films 113 
 
 Knifing-lead 304 
 
 Knots 313 
 
 Laboratory tests of paint incomplete 244 
 
 Lacquer, Chinese 146 
 
 " colored 115 
 
 Lampblack 132 
 
 Laniere 337 
 
 Lead paints 212 
 
 Lead compounds in varnish 38, 87 
 
 Lead sulphate 120 
 
 " white 119 
 
 Leather, artificial 116 
 
 Leonardo da Vinci 32, 122, 348 
 
 Leonidas 24 
 
 Libravius 19 
 
 Linseed-oil, bleached 35 
 
 " breaking of 34 
 
 " mucliage in 34 
 
 " oxidation of 3, 35 
 
 " % phosphates in 34 
 
 " saponification of 51 
 
 " specific gravity of 43 
 
 " tests for 43,62 
 
 Linoxyn 3, 35, 133 
 
 Litharge. . . 19 
 
 Lithopone 120 
 
 Livache's test 60 
 
 Lucca MS 28 
 
 Mcllhiney , 38, 39 
 
 Mcllhiney's bromine process 47 
 
 Maltha no 
 
 Manganese * 37 
 
 Mappae Claviculi 28 
 
 Marcellus 36 
 
INDEX. 3 6 9 
 
 PAGE 
 
 Marcian MS 16 
 
 Mastic 16, 107 
 
 Mathioli , 19 
 
 Maumene test 59 
 
 Merrifield, Mrs 337, 346 
 
 Mercurial paints 294 
 
 Metal roofs 320 
 
 Mills for paint 135, 138 
 
 Mill-scale 190 
 
 Mineral oil, detection of 53 
 
 Minium 15 
 
 Minutoli .. 7 
 
 Mixer 133 
 
 Molecular structure affects corrosion 220 
 
 Neil, J. W ' 362 
 
 Nero 28 
 
 Nicias 23, 334 
 
 Nickel 37 
 
 Oil of cedar 22 
 
 Oil paint 118 
 
 " " for structural metal 210 
 
 Old furniture, refinishing 334 
 
 Olibanum 25 
 
 Ovid 28 
 
 Oxides of iron 128 
 
 " " " permanence of 129,130 
 
 " P. & B." paint no 
 
 Paint 4 
 
 " in I3th century 10 
 
 " as engineering material, 186 
 
 " films, thickness of 185 
 
 " removers 326 
 
 " tests 217 
 
 Paris green 125 
 
 Paste color 133 
 
 Perilla oil 168, 176 
 
 Petitot 37 
 
 Pickling metal 202 
 
 Pigments 4, 119, 133 
 
 " fineness of 118,123 
 
 Plaster, to paint .' 323 
 
 Pliny 23, 28, 334, 340 
 
 Poisonous quality of Chinese varnish 148 
 
37 INDEX. 
 
 PAGE 
 
 Polishing varnish 157, 171, 330 
 
 Portland cement to protect iron , 181 
 
 Pounce 5 
 
 Praxiteles 23 
 
 Price of Japanese lacquer 177 
 
 Priming coat 313 
 
 Protective distinct from decorative coatings 187 
 
 Protogenes 23 
 
 Prussian blue 126 
 
 Putty 305, 314, 324 
 
 Pyroxylin 112, 114 
 
 Quin's memoir on lacquer 165 
 
 R. Angus Smith patent 259 
 
 Red lead 213 
 
 Refraction, index of 61 
 
 Rein's treatise on lacquer 174 
 
 Reinforced concrete 182 
 
 Rembrandt 348 
 
 Reports on painting unreliable 216 
 
 Resins. 72, 78 
 
 " tinctorial 108 
 
 Reynolds, Sir Joshua 348 
 
 Rochester pipe line 274 
 
 Roofs 320 
 
 Rossello 18 
 
 Rosin 95 
 
 " and lime , 96 
 
 " varnish 97 
 
 " " cracks in 98 
 
 " " rubbing test for 102 
 
 sponge test 101 
 
 Rough-stuff 306, 342, 343 
 
 Rubbing-varnish 156, 170, 308 
 
 Rub-lead 304 
 
 Rusting of cast iron 258 
 
 " " water-pipe 258 
 
 Sabin process 275, 279, 286 
 
 Salmasius 10, 28 
 
 Sandarac 5, 10, 15, 17, 19, 106 
 
 Sand-blast 197 
 
 Sanding 323 
 
 Scraping 195 
 
 Sea-water tests. 220 
 
INDEX. 371. 
 
 PAGE 
 
 Shellac 104, 243, 299 
 
 " white, insoluble 105 
 
 " varnish in fresh wafer 243 
 
 Ship and boat painting 297 
 
 Shipping structural metal 207 
 
 Ships'-bottom paints 290, 295 
 
 Shop marks 206 
 
 Shop painting structural metal 205 
 
 Sienna 131 
 
 Size 8 
 
 Solvents for pyroxylin , 114 
 
 Spar varnish 298 
 
 Spraying paint 253 
 
 Striping coat 207 
 
 Substitutes for linseed-oil 211 
 
 Surface of metal before painting 188, 192; 
 
 Table of "1896 " tests 225.- 
 
 " " 1897-9" tests 232 
 
 Taylor, S 347 
 
 Tempera 345, 
 
 Terra alba 121, 311 
 
 Theophilus n, 12, 22, 333, 
 
 Thinness of paint films 185, 
 
 Thinning enamel paint 143 
 
 Thompson, G. W 34 
 
 Tingry 2O, 359 
 
 Tingry's furnace 361 
 
 Tin-plate, to paint 321 
 
 Titian 349 
 
 Tripier-Devaux 361 
 
 Tung-oil ... 85, 149 
 
 Turpentine... 7, 95, 133, 312 
 
 oxidation of 82 
 
 Ultramarine 126 
 
 Umber ; 37, 131 
 
 Vanadium 38 
 
 Van Eyck 122, 346 
 
 Van Strij 348 
 
 Varnish, benzine in Si 
 
 " damar 105 
 
 " definition of 2 
 
 " Egyptian 7, 8, 21 
 
 " enamels 273, 
 
372 INDEX. 
 
 PAGE 
 
 Varnish, flowing of 82 
 
 " for steel structures 246 
 
 " films, thickness of 185, 248 
 
 " how made 2, 12, 75 
 
 " kettle 74 
 
 " -maker's furnace (1778) 358 
 
 " manufacture of 71 
 
 " mixing of 83 
 
 " over-cooking 77 
 
 packages 73 
 
 4t paint 140, 248 
 
 " remover 326 
 
 " shellac 104 
 
 " spirit 103 
 
 " under-cooking 77 
 
 Vehicle 118 
 
 Venice turpentine .' 107 
 
 Verenice 28 
 
 Vermilion 15, 126 
 
 Vernice liquida 9 
 
 Vernis-Martin 332 
 
 Vernix 9, 10 
 
 Violette 361 
 
 Violin varnish 336 
 
 Vitriol 33 
 
 Vitruvius 26, 333, 340 
 
 Walnut oil 36 
 
 Water colors 4 
 
 Water-cooled mills 135 
 
 Watin 351, 353 
 
 Wax 4, 9. 319. 342 
 
 White lead 119, 212, 297, 311, 340 
 
 White under-body , value of 121 
 
 Whiting 121 
 
 White zinc 120 
 
 Williams, E. D 112 
 
 Wire-brushing 196 
 
 Wood sheathing for ships'-bottoms 291 
 
 Xenophon 302, 340 
 
 Zinc sulphate 33 
 
 " white 120 
 
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 Theatre Fires and Panics i2mo, z 50 
 
 Holly's Carpenters' and Joiners' Handbook i8mo, o 75 
 
 Johnson's Statics by Algebraic and Graphic Methods 8vo, 2 oo 
 
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 Law of Operations Preliminary to Construction in Engineering and Archi- 
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 The World's Columbian Exposition of 1893 Large 4to, i oo 
 
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 Manual for Courts-martial i6mo, morocco, z 50 
 
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 Woodhull's Notes on Military Hygiene i6mo, go 
 
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 ASSAYING. 
 
 Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe. 
 
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 Thome and Bennett's Structural and Physiological Botany z6mo, a as 
 
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 Allen's Tables for Iron Analysis 8vo, 3 oo 
 
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 Austen's Notes for Chemical Students zamo, z 50 
 
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Eissler's Modern High Explosives ................................... 8vo, 4 oo 
 
 Effront's Enzymes and their Applications. (Prescott.) ................ 8vo, 3 oo 
 
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 Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe 
 
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 Fowler's Sewage Works Analyses ................................. i2mo, 2 oo 
 
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 Manual of Qualitative Chemical Analysis. Parti. Descriptive. (Wells.) 
 
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 System of Instruction in Quantitative Chemical Analysis. (Cohn.) 
 
 2 vols .................................................. Svo, 12 50 
 
 Fuertes's Water and Public Health ................................ 12010, i 50 
 
 Furman's Manual of Practical Assaying ............................. Svo, 3 oo 
 
 Getman's Exercises in Physical Chemistry ........................... i2mo, 
 
 Gill's Gas and Fuel Analysis for Engineers .......................... i2mo, I 25 
 
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 Helm's Principles of Mathematical Chemistry. (Morgan.) ............ izmo, i 50 
 
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 Hinds's Inorganic Chemistry ...................................... Svo, 3 oo 
 
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 Ladd's Manual of Quantitative Chemical Analysis ................... I2mo, 
 
 Landauer's Spectrum Analysis. (Tingle.) ............................ Svo, 3 oo 
 
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 Mandel's Handbook for Bio-chemical Laboratory .................... i2mo, i 50 
 
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 Miller'* Manual of Assaying ...................................... "mo, 
 
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 50 
 
 00 
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 Morgan's Outline of Theory of Solution and its Results ................ I2mo, 
 
 Elements of Physical Chemistry .............................. I2mo, 
 
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 Prescott and Winslow's Elements of Water Bacteriology, with Special Refer- 
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 Richards and Woodman's Air /Water, and Food from a Sanitary Standpoint . 8vo, a oo 
 
 Richards's Cost of Living as Modified by Sanitary Science lamo, i oo 
 
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 Richards and Williams's The Dietary Computer 8vo, i 50 
 
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 Non-metallic Elements.) 8vo, morocco, 75 
 
 Ricketts and Miller's Notes on Assaying 8vo, 3 o 
 
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 Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 oo 
 
 Salkowski's Physiological and Pathological Chemistry. (Orndorff.) 8vo, a 50 
 
 Schimpf's Text-book of Volumetric Analysis iamo, a 50 
 
 Essentials of Volumetric Analysis iamo, I 35 
 
 Spencer's Handbook for Chemists of Beet-sugar Houses i6mo, morocco, 3 
 
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 Quantitative Analysis. (Hall.) 8vo, 4 oo 
 
 Turneaure and Russell's Public Water-supplies 8vo, 5 oo 
 
 Van Deventer's Physical Chemistry for Beginners. (Boltwood.) iamo, i 50 
 
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 Short Course in Inorganic Qualitative Chemical Analysis for Engineering 
 
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 Whipple's Microscopy of Drinking-water 8vo, 3 50 
 
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 Wilson's Cyanide Processes lamo, i 50 
 
 Chlorination Process iamo. i 50 
 
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 CIVIL ENGINEERING. 
 
 BRIDGES AND ROOFS. HYDRAULICS, MATERIALS OP ENGINEERING 
 RAILWAY ENGINEERING. 
 
 Baker's Engineers' Surveying Instruments lamp, 3 oo 
 
 Bixby's Graphical Computing Table Paper 19$ X 24! inches. 35 
 
 ** Burr's Ancient and Modern Engineering and the Isthmian Canal (Postage, 
 
 27 cents additional.) 8vo, net, 3 50 
 
 Comstock's Field Astronomy for Engineers 8vo, a 50 
 
 Davis's Elevation and Stadia Tables 8vo, I oo 
 
 Elliott's Engineering for Land Drainage zamo, i 50 
 
 Practical Farm Drainage lamo, i 
 
 FolwelTs Sewerage. (Designing and Maintenance.) 8ro, 3 eo 
 
 Freitag's Architectural Engineering, ad Edition Rewritten 8vo, i 50 
 
 5 
 
French and Ives's Stereotomy 8vo, a 3 
 
 Goodhue's Municipal Improvements i zmo. I 7f 
 
 Goodrich's Economic Disposal of Towns' Refuse 8vo, 3 50 
 
 Gore's Elements of Geodesy , 8vo, 2 50 
 
 Hayford's Text-book of Geodetic Astronomy 8vo, 3 oo 
 
 Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, a 50 
 
 Howe's Retaining Walls for Earth i amo, i as 
 
 Johnson's Theory and Practice of Surveying Small 8vo, 4 oo 
 
 Statics by Algebraic and Graphic Methods 8vo, a oo 
 
 Kiersted's Sewage Disposal xamo, x as 
 
 Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.) i2mo, a oo 
 
 Mahan's Treatise on Civil Engineering. (1873 ) (Wood.) 8vo, 5 oo 
 
 Descriptive Geometry 8vo, I 50 
 
 Merriman's Elements of Precise Surveying and Geodesy 8vo, a 50 
 
 Elements of Sanitary Engineering 8vo, a oo 
 
 Herriman and Brooks's Handbook for Surveyors i6mo, morocco, a oo 
 
 Hugent's Plane Surveying , 8vo, 3 90 
 
 Ogden'f Sewer Design izmo, a oo 
 
 Patton's Treatise on Civil Engineering 8vo half leather, 7 50 
 
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 Rideal's Sewage and the Bacterial Purification of Sewage 8vo, 3 50 
 
 Siebert and Biggin's Modern Stone-cutting and Masonry 8vo, x 50 
 
 Smith's Manual of Topographical Drawing. (McMillan.) 8vo, a 50 
 
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 Arches 8vo, a oo 
 
 Taylor and Thompson's Treatise on Concrete, Plain and Reinforced. (In press.) 
 
 Trautwine's Civil Engineer's Pocket-book i6mo, morocco, 5 oo 
 
 Wait's Engineering and Architectural Jurisprudence 8vo, 6 oo 
 
 Sheep, 6 50 
 
 Law of Operations Preliminary to Construction in Engineering and Archi- 
 tecture 8vo, 5 oo 
 
 Sheep, 5 50 
 
 Law of Contracts 8vo, 3 oo 
 
 Warren's Stereotomy Problems in Stone-cutting 8vo, 2 50 
 
 Webb's Problems in the Ue and Adjustment of Engineering Instruments. 
 
 i6mo, morocco, i as 
 
 Wheeler's Elementary Course of Civil Engineering 8vo, 4 oo 
 
 Wilson's Topographic Surveying 8vo, 3 50 
 
 BRIDGES AND ROOFS. 
 
 Boiler's Practical Treatise on the Construction of Iron Highway Bridges. .8vo, a oo 
 
 Thames River Bridge. . . .' 4to, paper, 5 oo 
 
 Burr's Course on the Stresses in Bridges and Roof Trusses, Arched Ribs, and 
 
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 Foster's Treatise on Wooden Trestle Bridges 4to, 5 oo 
 
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 Howe's Treatise on Arches 8vo, 4 oo 
 
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 Part I. Stresses in Simple Trusses 8vo, a 50 
 
 Part II. Graphic Statics 8vo, 2 50 
 
 Part III. Bridge Design. 4th Edition, Rewritten 8vo, 2 50 
 
 Part TV. Higher Structures 8vo, 2 50 
 
 Morlson's Memphis Bridge 4to, 10 oo 
 
 6 
 
WaddelTs De Pontibus, a Pocket-book for Bridge Engineers. . . i6mo t morocco, 3 o 
 
 Specifications for Steel Bridges i amo, i 25 
 
 Wood's Treatise on the Theory of the Construction of Bridges and Roofs . 8vo, a oo 
 
 Wright's Designing of Draw-spans: 
 
 Part I. Plate-girder Draws 8vo, a 50 
 
 Part II. Riveted-truss and Pin-connected Long-span Draws 8vo, a 50 
 
 Two parts in one Tolume v , .8vo, 3 50 
 
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 Barin's Experiments upon the Contraction of the Liquid Vein Issuing from an 
 
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 Bovy*s Treatise on Hydraulics 8vo, 5 oo 
 
 Church's Mechanics of Engineering 8vo, 6 oo 
 
 Diagrams of Mean Velocity of Water in Open Channels paper, i 50 
 
 Coffin's Graphical Solution of Hydraulic Problems i6mo, morocco, a 50 
 
 Flather's Dynamometers, and the Measurement of Power zamo, 3 oo 
 
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 Fuertes's Water and Public Health lamo, x 50 
 
 Water-filtration Works xamo, a 50 
 
 Oanguillet and Kutter's General Formula for the Uniform Flow of Water in 
 
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 Hazen's Filtration of Public Water-supply 8vo, 3 oo 
 
 Hazlehurst's Towers and Tanks for Water- works 8vo, a 50 
 
 Herschel's 115 Experiments on the Carrying Capacity of Large, Riveted, Metal 
 
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 Mason's Water-supply. (Considered Principally from a Sanitary Stand- 
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 Merriman's Treatise on Hydraulics. 9th Edition, Rewritten 8vo, 5 oo 
 
 * Michie's Elements of Analytical Mechanics 8ro, 4 oo 
 
 Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water- 
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 Turneaure and Russell's Public Water-supplies 8vo, 5 oo 
 
 Wegmann's Desiam and Construction of Dams .' 4to, 5 oo 
 
 Water-supply of the City of New York from 1658 to'iSos 4to, 10 oo 
 
 Weisbach's Hydraulics and Hydraulic Motors. (Du Bois.) 8vo, 5 oo 
 
 Wilson's Manual of Irrigation Engineering Small 8vo. 4 oo 
 
 Wolff's Windmill as a Prime Mover 8vo, 3 oo 
 
 Wood's Turbines 8vo, a 50 
 
 Elements of Analytical Mechanics 8vo, 3 oo 
 
 MATERIALS OP ENGINEERING. 
 
 Baker's Treatise on Masonry Construction 8vo, 5 oo 
 
 Roads and Pavements 8vo, 5 oo 
 
 Black's United States Public Works Oblong 4to, 5 oo 
 
 Bovey's Strength of Materials and Theory of Structures 8vo, 7 50 
 
 Burr's Elasticity and Resistance of the Materials of Engineering. 6th Edi- 
 tion, Rewritten 8vo, 7 50 
 
 Byrne's Highway Construction '.8vo, 5 oo 
 
 Inspection of the Materials and Workmanship Employed .in Construction. 
 
 i6mo, 3 oo 
 
 Church's Mechanics of Engineering 8vo, 6 oo' 
 
 Du Bois's Mechanics of Engineering. VoL I Small 4to, 7 50 
 
 Johnson's Materials of Construction Large 8vo, 6 oo 
 
 Keep's Cast Iron 8vo, a 50 
 
 Lanza's Applied Mechanics 8vo, 7 50 
 
 Martens's Handbook on Testing Materials. (Henning.) a vols 8vo, 7 50 
 
 Merrill's Stones for Building and Decoration 8vo, 5 oo 
 
 7 
 
Meniman's Text-book on the Mechanics of Materials 8vo, 4 oo 
 
 Strength of Materials i2mo, i oo 
 
 Metcalf 's SteeL A Manual for Steel-users lamo, 2 oo 
 
 Patton's Practical Treatise on Foundations 8vo, 5 oo 
 
 Richey's Hanbbook for Building Superintendents of Construction. (In press. ) 
 
 Rockwell's Roads and Pavements in France I2mo, i 25 
 
 Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 oo 
 
 Smith's Materials of Machines i2mo, i oo 
 
 Snow's Principal Species of Wood 8vo, 3 50 
 
 Spalding's Hydraulic Cement izmo, 2 oo 
 
 Text-book on Roads and Pavements i2mo, 2 oo 
 
 Taylor and Thompson's Treatise on Concrete, Plain and Reinforced. (In 
 press.) 
 
 Thurston's Materials of Engineering. 3 Parts 8vo, 8 oo 
 
 Part I. Non-metallic Materials of Engineering and Metallurgy 8vo, 2 oo 
 
 Part H. Iron and Steel 8vo, 3 50 
 
 Part in. A Treatise on Brasses, Bronzes, and Other Alloys and their 
 
 Constituents 8vo, 2 50 
 
 Thurston's Text-book of the Materials of Construction 8vo, 5 oo 
 
 Tillson's Street Pavements and Paving Materials 8vo, 4 oo 
 
 Waddell's De Pontibus. (A Pocket-book for Bridge Engineers.) . . i6mo, mor., 3 oo 
 
 Specifications for Steel Bridges i2mo, i as 
 
 Wood's Treatise on the Resistance of Materials, and an Appendix on the Pres- 
 ervation of Timber 8vo, 2 oo 
 
 Elements of Analytical Mechanics 8vo, 3 oo 
 
 Wood's Rustless Coatings: Corrosion and Electrolysis of Iron and Steel. . .8vo, 4 oo 
 
 RAILWAY ENGINEERING. 
 
 Andre ws's Handbook for Street Railway Engineers. 3X5 inches, morocco, i 25 
 
 Berg's Buildings and Structures of American Railroads 4to, 5 oo 
 
 Brooks's Handbook of Street Railroad Location i6mo. morocco, i 50 
 
 Butts's Civil Engineer's Field-book i6mo, morocco, 2 50 
 
 Crandall's Transition Curve x6mo, morocco, i 50 
 
 Railway and Other Earthwork Tables 8vo, i 50 
 
 Dawson's "Engineering" and Electric Traction Pocket-book. i6mo, morocco, 5 oo 
 
 Dredge's History of the Pennsylvania Railroad: (1879) Paper, 5 oo 
 
 * Drinker's Tunneling, Explosive Compounds, and Rock Drills, 4to, half mor., 25 oo 
 
 Fisher's Table of Cubic Yards Cardboard, 25 
 
 Godwin's Railroad Engineers' Field-book and Explorers' Guide 1 6mo, mor., 2 50 
 
 Howard's Transition Curve Field-book i6mo, morocco, i 50 
 
 Hudson's Tables for Calculating the Cubic Contents of Excavations and Em- 
 bankments 8vo, i oo 
 
 Molitor and Beard's Manual for Resident Engineers i6mo, i oo 
 
 Nagle's Field Manual for Railroad Engineers i6mo, morocco. 3 oo 
 
 Philbrick's Field Manual for Engineers i6mo, morocco, 3 oo 
 
 Searles's Field Engineering i6mo, morocco, 3 oo 
 
 Railroad Spiral. i6mo, morocco, i 50 
 
 Taylor's Prismoidal Formula and Earthwork 8vo, i 50 
 
 Trautwine's Method of Calculating the Cubic Contents of Excavations and 
 
 Embankments by the Aid of Diagrams 8vo, 2 oo 
 
 The Field Practice of [Laying Out Circular Curves for Railroads. 
 
 1 2 mo, morocco, 2 50 
 
 Cross-section Sheet Paper, 25 
 
 Webb's Railroad Construction. 2d Edition, Rewritten i6mo. morocco, s oo 
 
 Wellington's Economic Theory of the Location of Railways Small 8vo, 5 oo 
 
 DRAWING. 
 
 Barr's Kinematics of Machinery 8vo, 2 50 
 
 * Bartlett's Mechanical Drawing -. 8vo, 3 oo 
 
 " Abridged Ed 8vo, i 50 
 
Coolidge's Manual of Drawing 8vo, paper, i oo 
 
 Coolidge and Freeman's Elements of General Drafting for Mechanical Engi- 
 neers. (In press.) 
 
 Durley's Kinematics of Machines 8vo, 4 oo 
 
 Hill's Text-book on Shades and Shadows, and Perspective 8vo, 2 oo 
 
 Jamison's Elements of Mechanical Drawing. (In press.) 
 Jones's Machine Design: 
 
 Part I. Kinematics of Machinery 8vo f i 50 
 
 Part n. Form, Strength, and Proportions of Parts 8vo, 3 oo 
 
 MacCord's Elements of Descriptive Geometr} , 8vo, 300 
 
 Kinematics; or. Practical Mechanism 8vo, 5 oo 
 
 Mechanical Drawing 4to, 4 oo 
 
 Velocity Diagrams 8vo, i 50 
 
 * Mahan's Descriptive Geometry and Stone-cutting 8vo, i 50 
 
 Industrial Drawing. (Thompson.) 8vo, 3 50 
 
 Mover's Descriptive Geometry. (In press.) 
 
 Reed's Topographical Drawing and Sketching 4to, 5 oo 
 
 Reid's Course in Mechanical Drawing 8vo, 2 oo 
 
 Text-book of Mechanical Drawing and Elementary Machine Design. .8vo, 3 oo 
 
 Robinson's Principles of Mechanism 8vo, 3 oo 
 
 Smith's Manual of Topographical Drawing. (McMillan.) 8vo, a 50 
 
 Warren's Elements of Plane and Solid Free-hand Geometrical Drawing. . I2mo, x oo 
 
 Drafting Instruments and Operations 12010, x 25 
 
 Manual of Elementary Projection Drawing I2mo, i 50 
 
 Manual of Elementary Problems in the Linear Perspective of Form and a 
 
 Shadow i2mo, x oo 
 
 Plane Problems in Elementary Geometry i2mo, x 25 
 
 Primary Geometry i2mo, 75 
 
 Elements of Descriptive Geometry, Shadows, and Perspective 8vo, 3 50 
 
 General Problems of Shades and Shadows 8vo, 3 oo 
 
 Elements of Machine Construction and Drawing 8vo, 7 So 
 
 Problems. Theorems, and Examples in Descriptive Geometry 8vo, 2 50 
 
 Weisbach's Kinematics and the Power of Transmission. (Hermann and 
 
 Klein.) ; . . . 8vo, 5 oo 
 
 Whelp ley's Practical Instruction In the Art of Letter Engraving 12 mo, 2 oo 
 
 Wilson's Topographic Surveying 8vo, 3 50 
 
 Free-hand Perspective 8vo, 2 50 
 
 Free-hand Lettering 8vo, x oo 
 
 Woolf 's Elementary Course in Descriptive Geometry Large 8vo, 3 oo 
 
 ELECTRICITY AND PHYSICS. 
 
 Anthony and Brackett's Text-book of Physics. (Magie.) Small 8vo, 3 oo 
 
 Anthony's Lecture-notes on the Theory of Electrical Measurements 12 mo, i oo 
 
 Benjamin's History of Electricity 8vo, 3 oo 
 
 Voltaic CelL 8vo, 3 oo 
 
 Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood.). .8vo, 3 oo 
 
 Crehore and Sauier's Polarizing Photo-chronograph 8vo, 3 oo 
 
 Dawson's "Eneineering" and Electric Traction Pocket-book. .i6mo, morocco, 5 oo 
 Dolezalek's Theory of the Lead Accumulator (Storage Battery). (Von 
 
 Ende.) izmo, * 2 50 
 
 Duhem's Thermodynamics and Chemistry. (Burgess.) 8vo, 4 oo 
 
 Flather's Dynamometers, and the Measurement of Power I2mo, 3 oo 
 
 Gilbert's De Magnete. (Mottelay.) 8vo, 2 50 
 
 Hanchett's Alternating Currents Explained 12 mo, i oo 
 
 Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 
 
 Holman's Precision of Measurements 8vo, 2 oo 
 
 Telescopic Mirror-scale Method, Adjustments, and Tests. Large 8vo, 75 
 
 9 
 
Landauer's Spectrum Analysis. (Tingle.) ............................ 8vo, 3 <> 
 
 Le Chatelier's High-temperature Measurements. (Boudouard iJurgess.)i2mc, 3 oo 
 
 Lob's Electrolysis and Electrosynthesis of Organic Compounds. (Lorenz.) i zmo, i oo 
 
 * Lyons's Treatise on Electromagnetic Phenomena. Vols.I.and IL 8vo, each, 6 oo 
 
 * Michie. Elements of Wave Motion Relating to Sound and Light ....... 8vo, 4 oo 
 
 Niaudet's Elementary Treatise on Electric Batteries. (Fishoack. ) ...... i amo, 50 
 
 * Rosenberg's Electrical Engineering. (Haldane Gee Kinzbrunner.) ---- 8vo, 50 
 
 Ryan, Norris, and Hozie's Electrical Machinery. Vol. L ............... 8vo, 9* 
 
 Thurston's Stationary Steam-engines ............................... 8vo, 50 
 
 * TUlman's Elementary Lessons in Heat .............................. 8vo, 90 
 
 Tory and Pitcher's Manual of Laboratory Physics .............. Small 8vo, oo 
 
 Hike's Modern Electrolytic Copper Refining ....................... 8vo, 3 oo 
 
 LAW. 
 
 * Davis's Elements of Law ........................................ 8vo, 2 50 
 
 * Treatise on the Military Law of United States ................... 8vo, 7 oo 
 
 Sheep, 7 So 
 
 Manual for Courts-martial .............................. i6mo, morocco, i 50 
 
 Wait's Engineering and Architectural Jurisprudence ................... 8vo, 6 oo 
 
 Sheep, 6 50 
 Law of Operations Preliminary to Construction in Engineering and Archi- 
 
 tecture ................................................ 8vo, 5 o 
 
 Sheep, 5 SO 
 
 Law of Contracts ............................................. 8vo, 3 oo 
 
 Winthrop's Abridgment of Military Law ............................ i2mo, 2 5* 
 
 MANUFACTURES. 
 
 Bernadou's Smokeless Powder Nitro-cellulose and Theory of the Cellulose 
 
 Molecule .............................................. I2mo, 2 5 
 
 Holland's Iron Founder ......................................... izmo, 2 50 
 
 " The Iron Founder,** Supplement ........................... i2mo, 2 50 
 
 Encyclopedia of Founding and Dictionary of Foundry Terms Used in the 
 
 Practice of Moulding .................................... izmo, 3 oo 
 
 Eissler's Modern High Explosives ................................... 8vo, 4 oo 
 
 Effront's Enzymes and their Applications. (Prescott.) ................. 8vo, 3 oo 
 
 Fitzgerald's Boston Machinist .................................... i8mo, z oo 
 
 Ford's Boiler Making for Boiler Makers ............................ i8mo, i oe 
 
 Hopkins's Oil-chemists' Handbook ................................. 8vo, 3 oo 
 
 Keep's Cast Iron ................................................. 8vo, 2 50 
 
 Leach's The Inspection and Analysis of Food with Special Reference to State 
 
 Control. (In preparation.) 
 Matthews's The Textile Fibres. (7n press.) 
 
 Metcalf's Steel. A Manual for Steel-users ......................... ismo, 2 o* 
 
 Metcalfe's Cost of Manufactures And the Administration of Workshops, 
 
 Public and Private ....................................... 8vo, 5 oo 
 
 Meyer's Modern Locomotive Construction ............................ 4to, 10 oo 
 
 Morse's Calculations used in Cane-sugar Factories .......... i6mo, morocco, i 50 
 
 * Reisig's Guide to Piece-dyeing ................................... 8vo, 25 oo 
 
 Sabin's Industrial and Artistic Technology of Paints and Varnish ...... 8vo, 3 oo 
 
 Smith's Press-working of Metals .................................... 8vo, 3 oo 
 
 Spalding's Hydraulic Cement ..................................... i ?.mo, 2 oo 
 
 Spencer's Handbook for Chemists of Beet-sugar Houses ..... i6mo, morocco, 3 oo 
 
 Handbook tor sugar Manufacturers ana their Chemists. . . z6mo, morocco, 2 oo 
 Taylor and Thompson's Treatise on Concrete, Plain and Reinforced. (In 
 
 Thonton's Manual of Steam-boilers, their Designs, Construction and Opera- 
 
 tion ................................................... 8vo, 5 oo 
 
 10 
 
* Walke'v Lectures on Explosive* 8vo, 4 oo 
 
 West's American Foundry Practice i2mo, 2 50 
 
 Moulder's Text-book X2mo, 2 50 
 
 Wiechmann's Sugar Analysis Small 8vo, 2 50 
 
 Wolf's Windmill as a Prime Mover 8vo, 3 oo 
 
 Woodbury's Fire Protection of Mills 8vo, 2 50 
 
 Wood's Rustless Coatings: Corrosion and Electrolysis of Iron and Steel. . .8vo, 4 oo 
 
 MATHEMATICS. 
 
 Baker's Elliptic Functions 8vo, x 5 
 
 * Bass's Elements of Differential Calculus I2mo, 4 o* 
 
 Briggs's Elements of Plane Analytic Geometry. / X2mo, I oo 
 
 Compton's Manual of Logarithmic Computations i2mo, x 50 
 
 Davis's Introduction to the Logic of Algebra 8vo, x 50 
 
 * Dickson's College Algebra Large I2mo, x SO 
 
 * Answers to Dickson's College Algebra 8vo, paper, as 
 
 * Introduction to the Theory of Algebraic Equations Large 12 mo, x 25 
 
 Halsted's Elements of Geometry 8vo, x 75 
 
 Elementary Synthetic Geometry 8vo, x 50 
 
 Rational Geometry I2mo ( 
 
 Johnson's Three-place Logarithmic Tables: Vest-pocket size paper, 15 
 
 100 copies for 5 oo 
 
 * Mounted on heavy cardboard, 8 X 10 inches, as 
 
 xo copies for a oo 
 
 Elementary Treatise on the Integral Calculus Small 8vo, x 50 
 
 Curve Tracing in Cartesian Co-ordinates i2mo, x oo 
 
 Treatise on Ordinary and Partial Differential Equations. .... .Small 8vo, 3 50 
 
 Theory of Errors and the Method of Least Squares xamo, x so 
 
 * Theoretical Mechanics ramo, 3 oo 
 
 Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.) i2mo, 200 
 
 * Ludlow and Bass. Elements of Trigonometry and Logarithmic and Other 
 
 Tables 8vo, 3 oo 
 
 Trigonometry and Tables published separately Each, a oo 
 
 * Lud low's Logarithmic and Trigonometric Tables 8vo, x oo 
 
 Maurer's Technical Mechanics 8vo, 4 oo 
 
 Merriman and Woodward's Higher Mathematics 8vo, 5 oo 
 
 Merriman's Method of Least Squares 8vo, 2 oo 
 
 Rice and Johnson's Elementary Treatise on the Differential Calculus . Sm., 8vo, 3 oo 
 
 Differential and Integral Calculus. 2 vols. in one Small 8vo, 2 50 
 
 Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 oo 
 
 Wood's Elements of Co-ordinate Geometry 8vo, a oo 
 
 Trigonometry: Analytical, Plane, and Spherical xamo, x oo 
 
 MECHANICAL ENGINEERING. 
 
 MATERIALS OF ENGINEERING, STEAM-ENGINES AND BOILERS. 
 
 Bacon's Forge Practice xamo, x 50 
 
 Baldwin's Steam Heating for Buildings xamo, 2 50 
 
 Barr's Kinematics of Machinery 8vo, 2 50 
 
 * Bartlett's Mechanical Drawing 8vo, 3 oo 
 
 ' " Abridged Ed 8vo r x s* 
 
 Benjamin's Wrinkles and Recipes izmo, 2 oo 
 
 Carpenter's Experimental Engineering 8vo, 6 oo 
 
 Heating and Ventilating Buildings 8vo, 4 oo 
 
 Gary's Smoke Suppression in Plants using Bituminous CoaL (In prep- 
 aration.) 
 
 Clerk's Gas and Oil Engine Small 8vo, 4 oo 
 
 Coolidge's Manual of Drawing 8vo, paper, x oo 
 
 11 
 
Coolidge and Freeman's Elements of General Drafting for Mechanical En- 
 gineers. (/TJ press.) 
 
 Cromwell's Treatise on Toothed Gearing i2mo, I 50 
 
 Treatise on Belts and Pulleys I2mo, i 50 
 
 Barley's Kinematics of Machines 8vo, 4 <x> 
 
 Flather's Dynamometers and the Measurement of Power i2mo, 3 oo 
 
 Rope Driving I2mo, 2 oo 
 
 Gill's Gas and Fuel Analysis for Engineers , i2mo, i 25 
 
 Hall's Car Lubrication i2mo, i oo 
 
 Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 
 
 Button's The Gas Engine 8vo, 5 oo 
 
 Jones's Machine Design: 
 
 Part I. Kinematics of Machinery Svo, i 50 
 
 Part IL Form, Strength, and Proportions of Parts 8vo, 3 oo 
 
 Kent's Mechanical Engineer's Pocket-book i6mo, morocco, 5 oo 
 
 Kerr's Power and Power Transmission 8vo, 2 oo 
 
 Leonard's Machine Shops, Tools, and Methods. (In preta.) 
 
 MacCprd's Kinematics; or, Practical Mechanism 8vo, 5 oo 
 
 Mechanical Drawing 4to, 4 oo 
 
 Velocity Diagrams 8vo, i 50 
 
 Mahan's Industrial Drawing. (Thompson.) 8vo, 3 50 
 
 Poole's Calorific Power of Fuels 8vo, 3 oo 
 
 Reid's Course in Mechanical Drawing 8vo. 2 oo 
 
 Text-book of Mechanical Drawing and Elementary Machine Design. .8vo, 3 oo 
 
 Richards's Compressed Air xamo, i 50 
 
 Robinson's Principles of Mechanism 8vo, 3 oo 
 
 Schwamb and Merrill's Elements of Mechanism. (In press.) 
 
 Smith's Press-working of Metals 8vo, 3 oo 
 
 Thurston's Treatise on Friction and Lost Work in Machinery and Mill 
 
 Work 8vo, 300 
 
 Animal as a Machine and Prime Motor, and the Laws of Energetics . i2mo, i oo 
 
 Warren's Elements of Machine Construction and Drawing 870, 7 50 
 
 Weisbach's Kinematics and the Power of Transmission. Herrmann 
 
 Klein.) 8vo, 5 oo 
 
 Machinery of Transmission and Governors. (Herrmann Klein. ). .8vo, 5 oo 
 
 HydrauLcs and Hydraulic Motors. (Du Bois.) 8vo, 5 oo 
 
 Wolff's Windmill as a Prime Mover 8vo, 3 oo 
 
 Wood's Turbines .8vo, a 50 
 
 MATERIALS OF ENGINEERING. 
 
 Bovey's Strength of Materials and Theory of Structures 8vo, 7 50 
 
 Burr's Elasticity and Resistance of the Materials of Engineering. 6th Edition, 
 
 Reset 8vo, 7 50 
 
 Church's Mechanics of Engineering 8vo, 6 oo 
 
 Johnson'" Materials of Construction Large Svo, 6 oo 
 
 Keep's Cast Iron Svo, 2 50 
 
 Lanza's Applied Mechanics 8vo, 7 5<> 
 
 Martens's Handbook on Testing Materials. (Henning.) 8vo, 7 50 
 
 Merriman's Tert-book on the Mechanic* of Materials 8vo, 4 oo 
 
 Strength of Materials i2mo, i oo 
 
 Metcalf's SteeL A Manual for Steel-users i2mo, 2 oo 
 
 Sabin's Industrial and Artistic Technology of Paints and Varnish Svo, 3 oo 
 
 Smith's Materials of Machines iamo, i oo 
 
 Thurston's Materials of Engineering 3 vols , Svo, 8 oo 
 
 Part II. Iron and Steel Svo, 3 50 
 
 Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their 
 
 Constituents. Svo 2 50 
 
 Text-book of the Materials of Construction Svo, 5 oo 
 
 12 
 
Wood's Treatise on the Resistance of Materials and an Appendix on the 
 
 Preservation of Timber 8vo, a oo 
 
 Elements of Analytical Mechanics 8vo, 3 oo 
 
 Wood's Rustless Coatings: Corrosion and Electrolysis of Iron and Steel. . ,8vo, 4 oo 
 
 STEAM-ENGINES AND BOILERS. 
 
 Carnot's Reflections on the Motive Power of Heat. (Thurston.) i2mo, i 50 
 
 Dawson's "Engineering" and Electric Traction Pocket-book. . t6mo, mor., 5 oo 
 
 Ford's Boiler Making for Boiler Makers x8mo, i oo 
 
 Goss's Locomotive Sparks 8vo, a oo 
 
 Hemen way's Indicator Practice and Steam-engine Economy 12 mo, a oo 
 
 Button's Mechanical Engineering of Power Plants 8vo, 5 oo 
 
 Heat and Heat-engines 8vo, 5 oo 
 
 Kent's Steam-bo'ler Economy 8vo, 4 oo 
 
 Kneass's Practice and Theory of the Injector 8vo i 50 
 
 MacCord's Slide-valves 8vo, a oo 
 
 Meyer's Modern Locomotive Construction 4to, zo oo 
 
 Peabody's Manual of the Steam-engine Indicator zamo, z 50 
 
 Tables of the Properties of Saturated Steam and Other Vapors 8vo, z oo 
 
 Thermodynamics of the Steam-engine and Other Heat-engines 8vo, 5 oo 
 
 Valve-gears for Steam-engines 8vo, a 50 
 
 Peabody and Miller's Steam-boilers 8vo, 4 oo 
 
 Pray*s Twenty Years with the Indicator Large 8vo, a 50 
 
 Pupln's Thermodynamics of Reversible Cycles in Gases and Saturated Vapors. 
 
 (Osterberg.) zamo, z as 
 
 Reagan's Locomotives : Simple, Compound, and Electric zamo, a 50 
 
 Rontgen's Principles of Thermodynamics. (Du Bois.) 8vo, 5 oo 
 
 Sinclair's Locomotive Engine Running and Management zamo, a oo 
 
 Smart's Handbook of Engineering Laboratory Practice zamo, a 50 
 
 Snow's Steam-boiler Practice 8vo, 3 oo 
 
 Spangler's Valve-gears 8vo, a 50 
 
 Notes on Thermodynamics i amo, z oo 
 
 Spangler, Greene, and Marshall's Elements of Steam-engineering 8vo, 3 oo 
 
 Thurston's Handy Tables 8vo, z 50 
 
 Manual of the Steam-engine a vols. 8vo, zo oo 
 
 Part I. History. Structuce, and Theory 8vo, 6 oo 
 
 Part II. Design, Construction, and Operation 8vo, 6 oo 
 
 Handbook of Engine and Boiler Trials, and the Use of the Indicator and 
 
 the Prony Brake 8vo 5 oo 
 
 Stationary Steam-engines 8vo, a 50 
 
 Steam-boiler Explosions in Theory and in Practice zamo z 50 
 
 Manual of Steam-boilers , Their Designs, Construction, and Operation . 8vo , 5 oo 
 
 Weisbach's Heat, Steam, and Steam-engines. (Du Bois.) 8vo, 5 oo 
 
 Whitham's Steam-engine Design 8vo, 5 oo 
 
 Wilson's Treatise on Steam-boilers. (Flather.) z6mo, a 50 
 
 Wood's Thermodynamics Heat Motors, and Refrigerating Machines 8vo, 4 oo 
 
 MECHANICS AND MACHINERY. 
 
 Barr's Kinematics of Machinery 8vo, a 50 
 
 Bovey's Strength of Materials and Theory of Structures 8vo, 7 50 
 
 Chase's The Art of Pattern-making zamo, a 50 
 
 ChordaL Extracts from Letters zamo, a oo 
 
 Church's Mechanics of Engineering 8vo, 6 oo 
 
 Notes and Examples in Mechanics 8vo, a oo 
 
 13 
 
Compton's First Lesson* in Metal-working iamo, i 50 
 
 Compton and De Groodt's The Speed Lathe iamo, i 50 
 
 Cromwell's Treatise on Toothed Gearing xamo, x 50 
 
 Treatise on Belts and Pulleys iamo, i 50 
 
 Dana's Text-book of Elementary Mechanics for the Use of Colleges and 
 
 Schools iamo, i 50 
 
 Dingey's Machinery Pattern Making iamo, a oo 
 
 Dredge's Record of the Transportation Exhibits Building of the World's 
 
 Columbian Exposition of 1893 4to, half morocco, 5 oo 
 
 Du Boit's Elementary Principles of Mechanics : 
 
 Vol. I. Kinematic! 8vo, 3 50 
 
 Vol. n. Statics 8vo, 4 oo 
 
 Vol. HI. Kinetic* 8vo, 3 50 
 
 Mechanics of Engineering. VoL I Small 4to, 7 50 
 
 VoL IL Small 4to, 10 oo 
 
 Durley'* Kinematics of Machines 8vo t 4 oo 
 
 Fitzgerald's Boston Machinist i6mo, x oo 
 
 Flather's Dynamometers, and the Measurement of Power xamo, 3 oo 
 
 Rope Driving xamo, a oo 
 
 Go**'* Locomotive Spark* Svo a oo 
 
 Hall's Car Lubrication xamo, x oo 
 
 Holly** Art of Saw Filing iSmo 75 
 
 Johnson's Theoretical Mechanic* xamo, 3 oo 
 
 Statics by Graphic and Algebraic Method* Svo, a oo 
 
 Jones'* Machine Design: 
 
 Part I. Kinematic* of Machinery Svo, x 50 
 
 Part IL Form, Strength, and Proportion* of Part* Svo, 3 oo 
 
 Ken's Power and Power Transmission Svo, a oo 
 
 Lanza's Applied Mechanic* Svo, 7 50 
 
 Leonard s Machine Shops, Tools, and Method*. (In press.) 
 
 MacCord's Kinematic*; or, Practical Mechanism Svo, 5 oo 
 
 Velocity Diagram* Svo, x 30 
 
 Maurer's Technical Mechanics Svo, 4 oo 
 
 Mtrriman'i Text-book on the Mechanics of Material* 8vo, 4 oo 
 
 * Michie'* Elements of Analytical Mechanic* 8vo ( 4 oo 
 
 Reagan's Locomotive*: Simple, Compound, and Electric iamo, a 50 
 
 Reid's Course in Mechanical Drawing Svo, a oo 
 
 Text-book of Mechanical Drawing and Elementary Machine Design . . Svo, 3 oo 
 
 Richards's Compressed Air iamo, x 50 
 
 Robinson's Principles of Mechanism Svo, 3 oo 
 
 Ryan, Norris, and Hoxie's Electrical Machinery. Vol.1 Svo, a s* 
 
 Schwamb and Merrill's Elements of Mechanism. (In press.) 
 
 Sinclair's Locomotive-engine Running and Management xamo, a oo 
 
 Smith's Press-working of Metals Svo, 3 oo 
 
 Materials of Machines iamo, x oo 
 
 Spangler, Greene, and Marshall's Elements of Steam-engineering Svo, 3 oo 
 
 Thurston's Treatise on Friction and Lost Work in Machinery and Mill 
 
 Work Svo, 3 oo 
 
 Animal as a Machine and Prime Motor, and the Law* of Energetic* . xamo, x oo 
 
 Warren'* Element* of Machine Construction and Drawing Svo, 7 50 
 
 Weisbach's Kinematic* and the Power of Transmission. (Herrmann 
 
 Klein.) Svo, 5 oo 
 
 Machinery of Transmission and Governors. (Herrmann Klein.). Svo, 5 oo 
 Wood's Elements of Analytical Mechanics Svo, 3 oo 
 
 Principles of Elementary Mechanics iamo, x as 
 
 Turbines Svo, a 50 
 
 The World's Columbian Exposition of 1893 4to, i oo 
 
 14 
 
METALLURGY. 
 
 Bgleston's Metallurgy of Silver, Gold, and Mercury: 
 
 VoL I. Silver .............................................. 8vo, 7 So 
 
 VoL II. Gold and Mercury ................................... 8vo, 7 So 
 
 ** Iles's Lead-smelting. (Postage 9 cents additional.) ............. lamo, 50 
 
 Keep's Cast Iron ................................................. 8vo, 50 
 
 Kunhardt's Practice of Ore Dressing in Europe ...................... 8vo, 50 
 
 Le Chatelier's High-temperature Measurements. (Boudouard Burgess.) . lamo, oo 
 
 Metcalf's Steel. A Manual for Steel-users ................... . ...... iamo, oo 
 
 Smith's Materials of Machines .................................... xamo, oo 
 
 Thurston's Materials of Engineering. In Three Parts ................ 8vo, 8 oo 
 
 Part II. Iron and Steel ................ <. ............. ........ 8vo, 3 So 
 
 Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their 
 
 Constituents .............................. . ............ 8vo, a 50 
 
 Hike's Modern Electrolytic Copper Refining .......................... 8vo, 3 oo 
 
 MINERALOGY. 
 
 Barringer's Description of Minerals of Commercial Value. Oblong, morocco, a 50 
 
 Boyd's Resources of Southwest Virginia ............................. 8vo, 3 oo 
 
 Map of Southwest Virginia ............. , ........... Pocket-book form, a oo 
 
 Brush's Manual of Determinative Mineralogy. (Penfield.) ............ 8ro, 4 oo 
 
 Chester's Catalogue of Minerals .............................. 8ro, paper, x oo 
 
 Cloth, x as 
 
 Dictionary of the Names of Minerals ............................ 8vo, 3 50 
 
 Dana's System of Mineralogy ..................... Large 8vo, half leather, xa 50 
 
 First Appendix to Dana's New "System of Mineralogy." ---- Large 8 vo, i oo 
 
 Text-book of Mineralogy ...................................... 8vo, 4 oo 
 
 Minerals and How to Study Them ............................ lamo, 50 
 
 Catalogue of American Localities of Minerals .............. Large 8vo, oo 
 
 Manual of Mineralogy and Petrography ............. ......... xamo, oo 
 
 Eakle's Mineral Tables ............................................ 8vo, as 
 
 Egleston's Catalogue of Minerals and Synonyms ...................... 8vo, so 
 
 Hussak's The Determination of Rock-forming Minerals. (Smith.) Small 8vo, oo 
 
 Merrill's Non-metallic Minerals: Their Occurrence and Uses. ............ 8vo, 4 oo 
 
 * Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests. 
 
 8ro, paper, o 50 
 Rotenbusch's Microscopical Physiography of the Rock-making Minerals. 
 
 (Iddings.) ............................................... 8vo, 5 oo 
 
 * TiUman's Text-book of Important Minerals and Docks ............... 8ro, a oo 
 
 Williams's Manual of Lithology .................................... 8vo, 3 oo 
 
 MINING. 
 
 Beard's Ventilation of Mines ..................................... xamo, a 50 
 
 Boyd's Resources of Southwest Virginia ............................. 8vo, 3 oo 
 
 Map of Southwest Virginia ........................ Pocket-book form, a oo 
 
 * Drinker's Tunneling, Explosive Compounds, and Rock Drills. 
 
 4to, half morocco, as oo 
 
 Bissler's Modern High Explosives .................... ............. 8vo, 4 oo 
 
 Fowler's Sewage Works Analyses ................................. xamo, 
 
 Goodyear's Coal-mines of the Western Coast of the United States ...... xamo, 
 
 Ihlseng's Manual of Mining ....................................... 8vo, 
 
 ** Iles's Lead-smelting. (Postage gc. additional.) .................. xamo, 
 
 Kunhardt's Practice of Ore Dressing in Europe ....................... 8vo, 
 
 O'Driscoll's Notes on the Treatment of Gold Ores ..................... 8vo, 
 
 * Walke's Lectures on Explosives .................................. 8vo, 
 
 Wilson's Cyanide Processes ...................................... xamo, 
 
 Chlorination Process ........................................ xamo, 
 
 Hydraulic and Placer Mining ................................. xamo, 
 
 Treatise on Practical and Theoretical Mine Ventilation ........... xamo 
 
 15 
 
 oo 
 50 
 oo 
 50 
 50 
 oo 
 oo 
 50 
 30 
 oo 
 as 
 
SANITARY SCIENCE. 
 
 Cope land' Manual of Bacteriology. (In preparation.) 
 
 FolwelTs Sewerage. (Designing, Construction and Maintenance.) Svo, 3 oo 
 
 Water-supply Engineering 8vo, 4 oo 
 
 Fuertes's Water and Public Health xamo, z 50 
 
 Water-filtration Works xamo, 2 50 
 
 Gerhard's Guide to Sanitary House-inspection i6mo, i oo 
 
 Goodrich's Economical Disposal of Town's Refuse Demy 8vo, 3 5* 
 
 Hazen's Filtration of Public Water-supplies 8vo, 3 oo 
 
 Kiersted's Sewage Disposal iamo, i 25 
 
 Leach's The Inspection and Analysis of Food with Special Reference to State 
 
 Control. (In preparation.) 
 
 Mason's Water-supply. (Considered Principally from a Sanitary Stand- 
 point.) 3d Edition, Rewritten 8vo, o 
 
 Examination of Water. (Chemical and Bacteriological) 12 mo, 25 
 
 Merriman's Elements of Sanitary Engineering Svo, oo 
 
 Nichols's Water-supply. (Considered Mainly from a Chemical and Sanitary 
 
 Standpoint.) (1883.) Svo, 50 
 
 Ogden's Sewer Design i zmo, oo 
 
 Prescott and Winslow's Elements of Water Bacteriology, with Special Reference 
 
 to Sanitary Water Analysis I2mo s 25 
 
 * Price's Handbook on Sanitation xamo, 50 
 
 Ricbards's Cost of Food. A Study in Dietaries 1 2tno, oo 
 
 Cost of Living as Modified by Sanitary Science zzmo, oo 
 
 Richards and Woodman's Air, Water, and Food from a Sanitary Stand- 
 point Svo, oo 
 
 * Richards and Williams'* The Dietary Computer Svo, 50 
 
 Rideal's Sewage and Bacterial Purification of Sewage Svo, 3 50 
 
 Turneaure and Russell's Public Water-supplies Svo, 5 oo 
 
 Whipple's Microscopy of Drinking-water Svo, 3 50 
 
 Woodhull's Notes and Military Hygiene i6mo, z 50 
 
 MISCELLANEOUS. 
 
 Barker's Deep-sea Soundings Svo, 2 oo 
 
 Smmons's Geological Guide-book of the Rocky Mountain Excursion of the 
 
 International Congress of Geologists Large Svo z s 
 
 Petrel's Popular Treatise on the Winds 8vo 4 oo 
 
 Haines's American Railway Management iamo, 50 
 
 Mott's Composition, Digestibility, and Nutritive Value of Food. Mounted chart. s 
 
 Fallacy of the Present Theory of Sound z6mo oo 
 
 Ricketts's History of Rensselaer Polytechnic Institute, 1824-1894. Small Svo, oo 
 
 Rotherham's Emphasized New Testament Large Svo, 2 oo 
 
 Steel's Treatise on the Diseases of the Dog Svo, 50 
 
 Totten's Important Question in Metrology Svo a 50 
 
 The World's Columbian Exposition ot 1893 4to, z oo 
 
 Von Bearing's Suppression of Tuberculosis. (Bolduan.) (In press.) 
 Worcester and Atkinson. Small Hospitals, Establishment and Maintenance, 
 and Suggestions for Hospital Architecture, with Plans for a Small 
 
 Hospital zamo, t 25 
 
 HEBREW AND CHALDEE TEXT-BOOKS. 
 
 Green's Grammar of the Hebrew Language Svo, 3 oo 
 
 Elementary Hebrew Grammar Z2mo, z 25 
 
 Hebrew Chrestomathy Svo, 2 oo 
 
 Gesenius's Hebrew and Chaldee Lexicon to the Old Testament Scriptures. 
 
 (Tregelles.) Small 4to, half morocco, 5 oo 
 
 Letteris's Hebrew Bible Svo, 2 2 
 
 16 
 
 UN! 
 
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