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Fourth Edition, 5s. ; cloth boards, 6s. ! CROSBY LOCKWOOD & CO., 7, STATIONERS' HALL COURT, E^C. ORNAMENTAL BRICKWORK No. 43, St. Martin's 'Lane, London, A RUDIMENTARY TREATISE ON THE MANUFACTURE OF BRICKS AND TILES CONTAINING) AN OUTLINE OF THE PRINCIPLES OF BRICKMAKING BY EDWARD DOBSON, A.I.C.E., M.I.B.A. ti AUTHOE OF "THE ART OF BUILDING," "MASONRY AND STONE-CUTTING," "FOUNDATIONS AND CONCRETE WORK," ETC., ETC. REVISED AND CORRECTED BY CHARLES TOMLINSON, F.H.S- SEVENTH EDITION WITH ADDITIONS BY ROBERT MALLET, A.M., F.R.S., M.I.C.E., Ere. SBith numcwu* Illustration* LONDON CEOSBY LOCKWOOD AND CO. 7, STATIONERS' HALL COURT, LUDGATE HILL 1882 TPSay ' - THE AUTHOE'S PEEFACE. THE preparation of this little work has necessarily ex- tended over a considerable period of time, and, although our limits preclude anything like an attempt at a com- plete view of the principles and practice of Brick- making, it will be found to contain much practical information which has never yet been published, and descriptions of processes which are little known be- yond the localities where they are practised. The whole of the illustrations have been drawn expressly for the work, and the descriptions of tools and pro- cesses have been written from personal observation, no dependence having been placed on verbal descrip- tion, even by experienced workmen. "Working brick- makers are mostly illiterate men, unable to describe correctly their own operations, and still less to explain their meaning. I have therefore considered it necessary to have every process here described carefully watched throughout, either by myself or by some one on whose accuracy of observation I could place dependence. In the course of last autumn I drew up several papers of questions, embracing a variety of points on which it was found difficult to obtain correct information, but which were distributed amongst those of my friends who were likely to have opportunities of ascertaining what was required. b 390318 IV Many of these papers in course of time were returned, accompanied by valuable details, and I have to express my thanks and obligations to many gentlemen per- sonally unknown to me for the assistance thus afforded. Amongst those from whom I have received valuable assistance during the progress of the work, I may especially mention the names of Mr. Arthur Aikin ; Mr. John Lees Brown, of Lichfield ; Mr. William Booker, of Nottingham ; Mr. Richard Prosser, of Bir- mingham ; and Mr. Frederick Ransome, of Ipswich. Mr. Richard Prosser has kindly contributed a valuable account of the practice of Brickmaking in Stafford- shire, which will be read with much interest, and it will be worth the reader's while to compare the processes described in this chapter with those made use of in the neighbourhood of Nottingham, described in Chapter III. The details given in Appendix I. respecting the manu- facture of Suffolk bricks were kindly furnished by Mr. Frederick Ransome, to whom I am also indebted for drawings of a Suffolk kiln, which were intended by him as a contribution to the work, but which, un- fortunately, were committed to the post for transmis- sion, and never reached their destination. In collecting the information requisite for writing the accounts of Brickmaking and Tilemaking as practised in the neighbourhood of London, I am under great obli- gations to Mr. Adams and Mr. Randell, of the Maiden Lane Tileries, and to Mr. Samuel Pocock, of the Cale- donian Fields, Islington, for the kindness with which they afforded me facilities for inspecting and sketching their works, and for the liberal manner in which they furnished me with details of prices and quantities. Although much time and pains have been bestowed upon the work, there is so much difficulty in writing 8 THE AUTHOR'S PREFACE. v strictly accurate account, even of a simple operation, that I cannot hope that it is perfectly free from errors ; but 1 trust that they are only of a trivial nature, and I shall be greatly obliged to any reader who will point out any omissions or mis-statements, that I may be able to correct them in a future edition. There has long been a want of rudimentary treatises on the Materials of Construction, published in a cheap form, and written in a simple and practical style, divested of scientific technicalities, which render such books nearly useless to those by whom they are most needed. I venture to express a hope that this work may be of service in supplying this deficiency with regard tc one very important class of building materials. At the same time it must be observed that the Science of Brick- making is as yet untrodden ground, comparatively little being known of the manner in which different sub- stances mutually act upon each other when exposed to furnace heat, or of the relative proportions of silica, alumina, lime, and other usual ingredients of brick- earths, which are best calculated to produce a sound, well-shaped brick, of a pleasing colour. All that I have attempted here, therefore, is to give a clear description of the actual manufacture of bricks and tiles, and to explain the leading differences which exist in the manner of conducting the several operations of Brickmaking ii) various parts of this country. How far I have succeeded in this attempt the reader alone can determine. EDWAUD DOBSOK PKEFACE TO THE FOUETH EDITION. THIS work was revised by Professor Tomlinson in 1863 } and some matter become useless by time and the altera- tion of the Excise laws judiciously expunged. A chapter was at the same time appended on making bricks by machinery, but since that period many improvements and new inventions have necessitated a supplemental chapter, in which the editor has endeavoured to give an outline of that part of the subject reaching to the present day. He has also added a sketch of that which was properly called by the author of the work the Science of Brickmaking. A few notes, revising the text gene- rally, will be found in the Appendix, and to which the alphabetical index now given affords easy reference. Though small and elementary, this work may pro- bably claim to be the most complete upon its subject in the English language. ROBERT MALLET. CONTENTS. N.B.The Numbeis refer to the Paragraphs and not to the pages, except where otherwise stated. INTRODUCTION. (Pages 1-12.) I. Early history of the art would not add to our practical know- ledge. II. Burnt brick used in the building of the Tower of Babel ; in the walls of Babylon ; both burnt and sun-dried bricks used in ancient Egypt. III. Bricks extensively used by the Eomans ; the art of brick- making abandoned at the decline of the Roman Empire ; subsequently revived in the middle ages. IV. Early and extensive use of bricks in Holland and the Netherlands. V. Brickmaking introduced into England by the Romans ; arrived at great perfection at the time of Henry VIII. ; only used for large mansions in the time of Queen Elizabeth. VI. Brick generally introduced as a building material in London after the great fire of 1666 ; many fine specimens of brickwork still extant, executed at the beginning of the 18th century. VII. Enumeration of the duties suc- cessively imposed upon bricks and tiles ; abolition of the distinction between common and dressed bricks, by 2nd and 3rd Viet. c. 24. VIII. The new act a great boon to the public. IX. Number of bricks made yearly in Great Britain. X. Differences in the processes employed in briekmaking in differents parts of England. XI. Average strength of various kinds of bricks. XII. Comparison between the crushing strengtn of hand-made and machine-made bricks. CHAPTER I. GENERAL PRINCIPLES OF THE MANUFACTURE OF BRICKS AND TILES. I. BRICKS. (Page 12.) 1. Classification of the various operations of the brickmaker. PREPARATION OF BRICK-EARTH. (Pages 12 25.) 2. Enumeration of qualities to be aimed at in making bricks. 3. Suc- cess depends principally on the selection and preparation of brick-earth. 4. Br.ck-earths may be divided into three principal classes; viz., pure clays, marls, and loams ; few earths fit for briekmaking r tout some 53 VI 11 CONTENTS. mixture. 5. Alumina the principal ingredient in brick-earth; cracks in drying, after being moulded, and will not stand firing ; necessary to add sand to strong clays, to diminish their contraction ; lime and sifted oreeze used near London for the same purpose. 6. Composition of fire clay; mode of making the Dinas fire brick. 7. Fire clay generally mixed with burnt clay, broken crucibles, &c. 8. Enumeration of prin- cipal localities where fire bricks are made ; relative cost of "Windsor, Welch, and Stourbridge fire bricks. 9. Bricks made of refractory clay, baked rather than burnt. 10. Composition of fusible earths. 11. London bricks not made of clay, but of loams and marls. 12. Bricks may be divided into two classes, baked and burnt; difficulties in treating the fusible earths. 13. Cutting bricks made from sandy loams, either natural or artificial. 14. Colour depends not on the natural colour of the clay, but upon its chemical composition. 15. Bricks might be made of various colours by the employment of metallic oxides. 16. Floating bricks. 17. TTnsoUing. 18. Clay digging and weatlwring. 19. Stones must be picked out by hand ; injurious effect of limestone in the clay. 20. Grind- ing. 21. Washing. 22. Cutters made of washed earth mixed with sand. 23. Sufficient attention not generally paid to the preparation of brick- earth. TEMPERING. (Pages 2528.) 24. Object of tempering; is effected in various ways ; treading, grind- ing, pugging, 25. Brickmaking on the Nottingham and Grantham railway. 26. Use of the pug-mill. MOULDING. (Pages 2835.) 27. Slop moulding and pallet moulding. 28. Description of slop moulding. 29. Description of pallet moulding. 30. Description of moulding table. 31. Brick moulds, their varieties. 32. Difference in rate of production per stool, according to the process employed. 33. Slop and pallet moulding sometimes combined. 34. Moulding by machinery. 35. Disadvantages of dense bricks. 36. Method invented by Mr.Prosser of moulding in the dry state. 37. Defects of pressed bricks. 38. Dif- ficulties in making moulded bricks, arising from warping in the kiln. 39. Dimensions of bricks. 40. Bricks made of various shapes in country yards, but not generally in London. 41. Bricks with hollow beds. 42. Ventilating bricks. DRYING. (Pages 35 38.) 43. Slop-moulded bricks dried on flats, and hacked under cover. 44. Bricks hacked in the open air where brickmaking is conducted on a large scale. 45. Clamp bricks hacked at once, and not dried on flats. 46. Recapitulation of differences between slop moulding and pallet moulding. 47. Different clays require different treatment. BUENING. (Pages 3842.) 48. Bricks burnt in clamps and in kilns. 49. Peculiarities of clamp burning. 50. Three classes of kilns. 51. Management of a kiln. 52. Impossible in a rudimentary treatise to describe all the processes CONTENTS. IX II. TILES. (Pages 42 47.; 53. Differences in the manufacture of bricks and tiles. 54. Three classes of tiles, viz., paving tiles> roofing tiles, and draining tiles. 55. Business of a tilery includes the making of pottery. 56. Tiles burnt ia the country together with bricks ; in London in separate kilns. 57. Drain- ing-tiles principally moulded by machinery. 58. Importance of making drain tiles a home manufacture. 59. Concluding observations. CHAPTER II. ON THE MANUFACTURE OF BRICKS AND TILES IN HOLLAND. BY HYDE CLARKE, C.E. I. BRICKS. (Pages 47 48.) Bricks extensively used in Holland. Dutch clinkers made at Moor, near Gouda. Materials for making them ; river slime and sand ; localities from whence obtained. For Flemish bricks the sand is brought from the river Scheldt. The slime and sand are mixed and kneaded together by treading. Dimensions of paving bricks and Dutch clinks House bricks and tiles made at Utrecht from brick-earth found in the neighbourhood. Dimensions of house bricks. II. BRICK-KILNS. (Pages 48 51.) Sometimes made to burn upwards of a million of bricks. Fire holes left in the side walls. Doorway made in the breadth of the kiln. Sheds erected on each side of the kiln to shelter the fires. Mode of setting the kiln. Mode of firing. III. TILES. (Page 52.) Varieties of tiles made in Holland. Clay ground in a pug-mill. Kneaded by women before moulding. Two moulders, viz., a rough moulder and a finisher. Tiles dried nrst in sheds and afterwards in the sun. Moulding of flat paving tiles. Iron moulds used in Switzerland. IV. TILE-KILNS. (Pages 53 55.) Tiles burnt in covered kilns with arched furnaces. Setting. Burn- ing. Cooling. Mode of giving a grey colour. Glazing. Utrecht the principal seat of the tile manufacture. Gouda celebrated for pottery and tobacco-pipes. CONTEXTS. CHAPTER III. BK1CKMAKING AS PRACTISED AT NOTTINGHAM. (Pages 5559.) 1. Peculiarities in manufacture of bricks near Nottingham. 2. Use of _ brass moulds not confined to Nottingham. 3. Object of crushing the brick-earth between rollers. 4. Advantages and disadvantages of the use of rollers. 5. Description of brickmaking at Nottingham applies, with slight variations, to the practice of the neighbouring counties. 6. Brick-earth from the marls of the new red sandstone ; abounds with layers of skerry and veins of gypsum. 7. Colour of Nottingham bricks. 8. Common bricks made without picking the clay. 9. Preparation of clay for making front bricks. 10. Manufacture of rubbers. 11. Clay at Nottingham not generally suited for making roofing tiles. 12. Size of old and modern bricks. GENERAL ARRANGEMENT or A BRICKWORK. (Pages 5980.) 13. Locality of existing yards. 14. Eental and cost of clay. 15. Ar- rangement of buildings. 16. Description of clay-mill. 17. Addition of a second set of rollers a great improvement. 18. Eeference to engravings of clay-mill ; mode of boxing up the machinery. 19. Improvement to conceal machinery. 20. Duty performed. 21. Length of time a clay- mill will remain in working condition. 22. Description of Wash-mill. 23. The Pug-mill not used at Nottingham. 24. Moulding sand. 25. Mould- ing table, description of. 26. Brick mould, description of. 27. Use of copper moulds confined to small articles. 28. Mould placed on the moulding table and not upon a stock-board. 29. Plane, description of. 30. The flats, how prepared; size of. 31. The Hovel, description of; sometimes provided with flues. 32. Best bricks dried wholly under cover in flued hovels. 33. The Clapper, description of ; use of. 34. Dressing bench and dresser. 35. Machinery for pressing bricks ; points to be attained in making machinery. 36. Machine-pressed bricks cheaper than those dressed by hand. 37. Kiln, detailed description of. 38. Different mode of constructing the walls. 39. Comparison of the two methods. 40. Eeference to engravings. 41. Steps tothe tops of the kilns. 42. Sizes of kilns. 43. Duration of kilns. PROCESS OF BRICKMAKING. (Pages 80 87.) 44. Clay digging. 45. Tempering. 46. Cost of. 47. Moulding, descrip- tion of process. 48. Drying; laying on flats; hacking. 49. Timo that should be allowed for drying. 50. Cost of moulding and drying. 51. Pressed bricks. 2. Polished bricks. 63. Size of brick-moulds. 54. Eate of production. 55. Burning; management of the firing. 56. Cost of fuel. 57. Effect of the fire upon the colour of the bricks. 58. Cost of setting and drawing the kiln. 59. Cost of labour in firing. 60. Enumeration of the varieties of brick ware manufactured at Not- tingham. CONTENTS. XI COST OF MANUFACTURE. (Pages 8794.) 61. Land and brick-earth ; difficulty of estimating rental ; cost of clay. 62. Buildings and machinery; difficulty of ascertaining best relative sizes of working floors, hovels, and kilns. 63. Approximate estimate of extent of buildings and plant required for a weekly production of 46,800. 64. Additional buildings required in a yard, where all kinds of brickware are made. 65. Enumeration of tools required. 66. Labour, how paid for. 67. Summary of cost of production. 68. Relative value of dif- ferent qualities of bricks. 69. Reference to illustrations, figs. 1 to 18. CSAPTEE IY. BRICKMAKING AS PRACTISED IN THE STAFFORDSHIRE POTTERIES. BY R. PROSSER, C.E. BRICKS. (Pages 95 96.) 1. Bricks; enumeration of kinds of brick manufactured. 2. Drab bricks chiefly used for furnace work. 3. Tiles. 4. Clay. 5. Names of strata in the pottery district. 6. Two examples given of the process of brick and tile making. FIRST EXAMPLE BRICK.MAKING. (Pages 97 101.) 7. Buildings and plant. 8. Rates of production. 9. Tempering. 10. Moulding. 11. Drying. 12. Loss of weight whilst drying. 13. Burn- ing. 14. Cost of manufacture. 15. Rental. DESCRIPTION OF ILLUSTRATIONS. (Pages 102 105.) 16. Clay-mill. 17. Moulding table. 18. Brick mould. 19. The oven or cupola. SECOND EXAMPLE TILE-MAKING. (Pages 105 111.) 20. Enumeration of articles made at Basford. 21. Weathering and tempering. 22. Moulding. 23. Drying. 24. The Set. 25. Quarries and Dust Bricks. 26. Drain tiles. 27. Tile machines. 28. Firing; detailed description of. 29. Selling prices of different articles. DESCRIPTION OF ILLUSTRATIONS. (Pages 111 117.) 30. Moulding bench. 31. Mode of drying tiles. 32. Tile-block and horse. 33. Mode of setting lower part of oven. 34. Mode of setting upper part of oven. 35. Desirability of improving the mode of conduct- ing the manufacture of bricks. 36. Expense of carriage. 37. Analysis of clays, &c. Xll CONTENTS. ON THE SOUTH STAFFORDSHIRE RAILWAY. (Pages 117119.) 38. Bricks made for this line by Mr. G'eorge Brown, of "Walsall "Wood. Material not clay, but marl. Description of strata. Description of pi'ocesses employed. Cost of bricks at the kiln. CHAPTER V. BRICKMAKING IN THE VICINITY OF LONDON. (Page 119.) 1. Subject divided into three heads. I. MATERIALS AND PLANT. (Pages 119 133.) 2. Brick-earth divided into three qualities. 3. Strong clay. 4. Loam. 6. Malm. 6. Diiferent modes of preparation. 7. Object of adding chalk. 8. Soil. 9. Sand. 10. General arrangement of a Brickwork. 11. C/ial.t and Clay Mills. 12. The Pug-mill. 13. The Cuckhold. 14. The Mould- ing Stool. 15. The Brick Mould. 16. The Stock-board. 17. The Strike and Pallets. 18. The Hack Barrow. 19. The Hack Ground. II. PROCESS OF MANUFACTURE. (Pages 138158.) 20. Clay digging. 21. Quantity of clay required per 1,000. 22. Maiming. 23. Soiling. 24. Tempering. 25. Pugging. 26. Moulding. 27. Hacking. 28. Clamping, requires skill. 29. General principles of. 30. Foundation. 31. Upright. 32. Necks. 33. Firing. 34. Breeze. 35.. Proportion required depends on the nature of the clay. 36. Time allowed for burning. 37. Upright and Outside. 38. Variations in the mode of clamping. 39. Table of the qualities and prices of bricks made for the London market. 40. Brickmaking at Cheshunt. 41. Brick- making practised generally all round London. III. COST OF MANUFACTURE. (Page 150.) 42. Cost divided under three heads. 43. Clay. 44. Chalk. 45. Sand. 46. Breeze. 47. Soil. 48. Coals and wood. 49. Water. MATERIALS AND FUEL. (Pages 159 161.) . 45. Sand. 46. Breeze. 47. Soil. 48. Coals MACHINERY AND TOOLS. (Page 161.) 50. Cost of plant. LABOUR. (Page 162.) 61. Details of cost. CONTENTS. xiii BRICKMAKING AT THE COPENHAGEN TUNNEL, ON THE GREAT NORTHERN RAILWAY. (Pages 162 164.) Description of rollers, drying sheds, and kilns. REFERENCE TO ILLUSTRATIONS. (Pages 164 167.) 62 to 59. Description of figures 1 to 21. CHAPTER VI. LONDON" TILERIES. INTRODUCTORY. (Pages 167169.) 1. The present chapter confined to a description of the mamifacture of pantiles. 2. List of principal articles made at the London Tileries. BUILDINGS AND PLANT. (Pages 170 183.) 3. Pug-mill. 4. Sling. 5. The Moulding Shed. 6. The Pantile Table. 7. TU Block and Stock-board. 8. The Tile Mould. 9. The Roll. 10. The Washing-off Table. 11. The Splayer. 12. The Thwacking Frame. 13. The Tile Kiln. PROCESS OF MANUFACTURE. (Pages 183 186.) 14. Clay getting and weathering. 15. Tempering. 16. Slinging. 17. Moulding. 18. Thwacking. 19. Kilning. COST OF MANUFACTURE. (Pages 186 188.) 20. Tabular view of cost. 21. Selling prices. 22. Differences in the processes employed in the manufacture of various articles. 23. DESCRIPTION OF ILLUSTRATIONS. (Pages 188 189.) CHAPTER VII. ON THE MANUFACTURE OP ENCAUSTIC TILES. (Pages 189191.} 1. Revival of the manufacture of encaustic tiles. 2. Difficulties arising from the unequal shrinkage of differently- coloured clays. PROCESS OF MANUFACTURE. (Pages 191 195.) 3. Clay. 4. Moulding. 5. Inlaying. 6. Drying, firing, and glazing, 7. Manufacture of tesserse. 8. Tesselated pavements. S1V CONTENTS. CHAPTER Yin. ON THE MANUFACTURE OF BRICKS AND DRAIN-PIPES BY MACHINERY. (Pages 195209.) Object to deal with principles rather than with minute details. Various patents for making bricks by machinery. Description of Oates's brick- making machine. Crushing strength of bricks made by this machine. Machine can utilise materials unserviceable to the hand brickmaker. Cost of machine. Description of drain-pipe making machine. Hollow bricks also made by it. Various forms of hollow bricks. CHAPTER IX. ADDITIONAL REMARKS ON THE MANUFACTURE OF BRICKS BY MACHINERY. (Pages 210244.) BY ROBERT MALLET, A.M., F.R.S. Improvements in brickmaking since 1863. Whitehead's improved clay crushing and grinding roller-mill. Whitehead's pug-mill. Whitehead's perforated pug-mill. Portable clay -mill. Composite machines, in which crushing rollers and horizontal pug-mills are combined. Brickmaking machines, by Whitehead, M. Jardin, Clayton & Co. Machine for working with plastic clay. Brick -pressing machines, by Longley, Whitehead, and Bradley and Craven. Dry-clay brickmaking machines, by Hersey and Walsh, Bradley and Craven, and "Wilson of Campbell- field. Tile-making machines, by Page & Co., and Whitehead. Hoffmann's brick-kiln. APPENDIX I. BY CHARLES TOJELINSON, F.R.S. (Pages 245261.) On the plasticity and odour of clay. On drying bricks. On the.use of coal-dust in making clamp bricks. Brickmaking at Great Grimsby. Brickmaking in Suffolk. On the making and burning of drain-tiles. APPENDIX II. BY ROBERT MALLET, A.M., F.R.S. (Pages 262272.) The science of brickmaking. Coloured bricks. Infusorial siliceous materials. Plasticity and odour of clay. Water chemically combined oc mechanically present. RUDIMENTS OF THE ART OF MAKING BRICKS AND TILES, INTRODUCTION. I. IT would be impossible., in a little volume like the present, to enter at any length upon the early history of the Art of Brickmaking, nor would such an investi- gation, however interesting in a historical point of view, add much to our practical knowledge of the subject. It is, however, desirable that we should give a few par- ticulars relative to the progress of the manufacture in this country ; and we propose at the same time to give a brief sketch of the legal restrictions which have been imposed from time to time upon the mode of conduct- ing the operations of the brickmaker. II. The use of brick as a building material, both burnt and unburnt, dates from a very early period. Burnt brick is recorded in the Bible to have been used in the erection of the tower of Babel ; and we have the testi- mony of Herodotus for the fact, which is confirmed by the investigations of travellers, that burnt bricks, made from the clay thrown out of the trench surrounding B A INTRODUCTION. the city, were used in building the walls of the city of Babylon. These very ancient bricks were of three kinds ; one of which was very similar to the modern white Suffolk bricks, and another to the ordinary red brick of the present day. Sun-dried bricks were extensively used in ancient times, especially in Egypt, where their manufacture was considered a degrading employment, and, as such, formed the principal occupation of the Israelites during their bondage in Egypt after the death of Joseph. Very interesting ancient representations of the processes employed are still in existence, and throw much light on various passages of Scripture. Thus, the passage in Psalm Ixxxi. 6, " I removed his shoulder from the burden; his hands were delivered from the (water) pots," is strikingly illustrated by pictures still preserved to us, in which labourers are carrying the tempered clay on their shoulders to the moulders, whilst others are engaged in carrying vessels of water to temper the clay. The Egyptian sun-dried bricks were made with clay mixed with chopped straw, which was furnished to the Israelites by their Egyptian taskmasters before the application of Moses to Pharaoh on their behalf, after which the obligation was laid on them to provide their own straw, which appears to have been a grievous addi- tion to their labour. It would appear from the details given, that the Israelites worked in gangs, under the superintendence of an overseer of their own nation, who was provided with all necessary tools and mate- rials, and who was personally responsible for the labour of the gangs. Burnt bricks were, however, also used in Egypt for river walls and hydraulic works, but, probably, not to any very great extent. INTRODUCTION. 6 It is recorded in 2 Samuel xii. 31, that David put the children of Ammon under saws, and harrows, and axes of iron, and made them pass through the brick- kiln : without entering on the question whether the Ammonites were made to labour in the brickfields as the Israelites had themselves previously done during the time of their bondage in Egypt, or whether we are to understand that they were put to death with horrible tortures, as supposed by most commentators, there is a strong presumption that the implements here spoken of in connection with the brick-kiln were employed in the preparation of the clay ; and if this view be correct, the passage is interesting as evidence of the use of machinery in making bricks at a very early period of history. III. The Romans used bricks, both burnt and un- burnt, in great profusion ; all the great existing ruins at Rome being of brick. At the decline of the Roman Empire, the art of brickmaking fell into disuse, but was revived in Italy after the lapse of a few centuries. The mediseval ecclesiastical and palatial architecture of Italy exhibits many fine specimens of brickwork and ornamental work in terra-cotta; cornices and other decorations of great beauty being executed in the latter material. IV. In Holland and the Netherlands, the scarcity of stone led, at an early period, to the extensive use of brick, not only for domestic but for ecclesiastical build- ings, and these countries abound in fine specimens of brickwork, often in two colours, combined with great taste, and producing a very rich effect, as in the cele- brated examples at Leeuwarden in Friesland. It is worthy of remark, that in the fens of Lincolnshire and Norfolk, where we should naturally have expected to B 2 4 INTRODUCTION. have found the same material made use of, the churches, many of which are exceedingly fine specimens of archi- tecture, are built of small stones, said to have been brought from a great distance on pack-horses. V. Brickmaking appears to have been introduced into England by the Romans, who used large thin bricks or wall tiles as bond to their rubble construc- tions ; and such wall tiles continued to be used in England until rubble work was superseded by regular masonry, about the time of the Norman Conquest. Brick does not appear to have come into general use as a building material until long afterwards. In the reign of Henry VIII., however, the art of brickmaking had arrived at great perfection, and the remains of many buildings erected about this time exhibit some of the finest known specimens of orna- mental brickwork. The following is a list of some of the principal brick buildings erected at the period of which we speak : NAME. WHEN BUILT. Hurstmonceaux Castle, Sussex . Early in the reign of Henry VI. Gate of the Ryehouse in Hertfordshire Ditto. Tattershall Castle, Lincolnshire . A.D. 1440. Lollards' Tower, Lambeth Palace Oxborough Hall, Norfolk . Gateway, Rectory, Hadleigh, Suffolk Old part of Hampton Court Hengrave Hall, Suffolk A.D. 1454. About A.D. 1482. Close of 15th century. A.D. 1514. Finished A.D. 1538. Manor House, at East Barsham, Norfolk During the reign of Henry VII. Thorpland Hall, Norfolk . . . Ditto. Parsonage Hcuse,Great Snoring, Norfolk During the reign of Henry VIII. Many of these buildings have been engraved in Pugin's " Examples of Gothic Architecture," to which we would refer the reader. The decorative details of the Manor House at East Barsham, and of the Parsonage House at Great Snoring, are particularly worthy of notice ; INTRODUCTION. 5 the panelled friezes, cornices, and other ornamental work, being constructed of terra- cotta moulded to the required form. The use of terra-cotta for decorative panels and bas-reliefs appears to have been common during the reign of Henry VIII. The gateway of York Place, Whitehall, designed by Holbein, was de- corated with four circular panels, which are still pre- served at Hatfield Peveril, Hants. The gateway of the Hectory in Hadleigh churchyard is very similar in character to that at Oxborough Hall, engraved in Pugin's work, above referred to. It has been lately restored very carefully, the terra-cotta work for the purpose being made at the Layham Kilns, near Hadleigh, in moulds of somewhat complicated con- struction. In the time of Queen Elizabeth, brick seems only to have been used in large mansions. Ft/x common build- ings, timber framework, filled in with lath and plaster, was generally used, and this construction was much employed, even when brickwork was in common use, the brickwork, up to a late period, being merely intro- duced in panels between the wooden framing. VI. On the rebuilding of London after the great fire of 1666, brick was the material universally adopted for the new erections, and the 19th Car. II. c. 11, regu- lated the number of bricks in the thickness of the walls of the several rates of dwelling-houses. One of the resoiations of the corporation of the city of London, passed about this time, is interesting ; it is as follows : " And that they (the surveyors) do encourage and give directions to all builders, fur ornament sake, that the ornaments and projections of the front buildings be of rubbed bricks; and that all the naked parts of the walls may be done of rough bricks, neatly wrought, or all 6 INTRODUCTION. rubbed, at the direction of the builder, or that the builders may otherwise enrich their fronts as they please." Much of the old brickwork still remaining in London, in buildings erected at the end of the 17th and be- ginning of the 18th century, is very admirably executed. The most remarkable feature of the brickwork of this period is the introduction of ornaments carved with the chisel. A fine example of this kind of work is shown in the Frontispiece,* which is a sketch of No. 43, St. Martin's Lane, one of a block of houses built by a person of the name of May, who about the same time erected May's Buildings, to which the date of 1739 is affixed. The house in question is said to have been intended by Mr. May for his own residence. Its deco- rations consist of two fluted Doric pilasters, supporting an entablature, the whole executed in fine red brick- work; the mouldings, flutings, and ornaments of the metopes having been carved with the chisel after the erection of the walls. f VII. It was not till the close of the last century that bricks were subjected to taxation. The 24th Geo. III. c. 24, imposed a duty of 2s. 6d. per thousand on bricks of all kinds. By the 34th Geo. III. c. 15, the duty was raised to 4s. per thousand. By the 43rd Geo. III. c. 69, bricks were divided into common and dressed bricks, and separate rates of duty were imposed on each kind. These duties and those on tiles were as follows : * The author is indebted to the kindness of Mr. Edis for this sketch of one of the most interesting specimens of ornamental brickwork in the metropolis. t This fact was discovered some years ago, when the house was undergoing a thorough repair, and the scaffolding afforded facilities for a close inspection of the ornamentation. Cast terra-cotta imitations of carved stone for architectural decoration were sent by Mr. Blanchard to the Exhibition of 1851, and were strongly recommended in the Jury Keport, Class XXVIII. INTRODUCTION. < SCHEDULE (A) DUTIES. BRICKS AND TILES. . rf. For every thousand bricks which shall be made in Great Bri- tain, not exceeding any of the following dimensions, that is to say, ten inches long, three inches thick and five inches wide . . . .050 For every thousand of bricks which shall be made in Great Britain exceeding any of the foregoing dimensions . . 10 For every thousand of bricks which shall be made in Gi'eat Britain, and which shall be smoothed or polished on one or more side or sides, the same not exceeding the superficial dimensions of ten inches long by five inches wide . . 12 For eveiy hundred of such last-mentioned bricks, exceeding 7 The duties on the aforesaid superficial dimensions ) paving-tiles. For every thousand of plain tiles which shall be made in Great Britain 4 10 For every thousand of pan or ridge tiles which shall be made in Great Britain . 12 10 Fur every hundred of paving tiles which shall be made in Great Britain not exceeding ten inches square . . .025 For every hundred of paving tiles which shall be made in Great Britain exceeding ten inches square . . . 4 10 For every thousand tiles which shall be made in Great Bri- tain, other than such as are hereinbefore enumerated or described, by whatever name or names such tiles are or may be called or known 4 10 N.B. The said duties on bricks and tiles to be paid by the maker or makers thereof respectively. By the 3rd William IV. c. 11 (1833), the duties on tiles * were wholly repealed, and two years afterwards the duty on bricks was again raised, making the duty on common bricks 5s. IQd. per thousand. The brick duties formed the subject of the 18th Report of the Commissioners of Excise Enquiry, 1836; and in 1839 these duties were repealed by the 2nd and 3rd Viet. c. 24, and a uniform duty of 5s. lOd. per thou- * By a curious oversight, this Act, which was intended to put roofing tiles on the same footing as slates, also repealed the duties on paving tiles, whilst bricks used for paving remained subject to duty as before. Thus a lump of clay put into a mould of 10 in. X 5 in. X 3 paid duty, but the same quantity of clay put into a mould 10 in. square was duty free, because it came under the denomination of a tile. The manufacturer, and nr the public, reaped the advantage thus given 8 INTRODUCTION. sand imposed on all bricks of which the cubic content did not exceed 150 cubic inches, without any distinc- tion as to shape or quality. VIII. The new Act was a great boon to the public as well as to the trade, as, in consequence of the removal of the restrictions on shape, bricks might be made to any required pattern ; and moulded bricks for cornices, plinths, string-courses, &c., could be manufactured at a moderate price. Under the old regulations, also, the brickmaker was precluded from correcting any defect which might arise from warping or twisting in the process of drying, without making himself liable to pay the higher rate of duty. In 1850 the duty on bricks was entirely repealed. IX. The number of bricks annually made in Great Britain is very great ; just before the duty was repealed, a charge was made on about 1,800,000,000 bricks annually. In 1854 the number manufactured was estimated to be over 2,000,000,000, of which about 130,000,000 were made in the brickfields in and around Manchester, and about a similar number by the London brickmakers. The weight of this annual produce is upwards of 5,400,000 tons, representing a capital employed probably exceeding 2,000,000. Comparatively few bricks are made in Scotland, on account of the abundance of stone in that country. Those who are not practically connected with engineer- ing works may find some difficulty in forming a clear conception of the immense number of bricks annually made for railway purposes ; and which may be roughly estimated at from 600 to 800 millions annually. In 1821, before the introduction of the railway system, the number of bricks charged with duty in England and Scotland amounted to 913,231,000. In 1831 the INTRODUCTION. VI number was 1,153,048,581. In 1840 the number rose to 1,725,628,333. A common turnpike road bridge over a railway requires for its construction, in round numbers, 300,000 bricks; and the lining of a railway tunnel of ordinary dimensions consumes about 8,000 for every yard in length, or in round numbers about 14,000,000 per mile. X. The processes employed in the manufacture of bricks differ very greatly in various parts of the country. In some districts the clay is ground between rollers, and the pugmill is never used. In others, both rollers and pugmills are employed. In the neighbourhood of London the clay is commonly passed through a wash- mill. Equal differences exist in the processes of mould- ing and drying. Lastly, the form of the kiln varies greatly. In many places the common Dutch kiln is the one employed. In Essex and Suffolk the kilns have arched furnaces beneath their floors ; in Staffordshire bricks are fired in circular domed ovens called cupolas ; whilst near London kilns are not used, and bricks are burnt in clamps, the fuel required for their vitrifica- tion being mixed up with the clay in the process of tempering. XI. Bricks vary very much in their strength, a point to which, although of considerable importance, very little attention is paid. There is a striking difference in this respect between modern and ancient bricks ; a differ- ence very much in favour of those made centuries ago; and, perhaps, the weakest bricks made are supplied by London makers. In some experiments by Mr. Hawkes (a detailed account of which is given in' the Builder for 1861) it was found that of thirty-five kinds of bricks which were tested, the average strength of the strongest B 3 10 INTRODUCTION. was 2,855 Ibs. ; of those of medium tenacity, 2,125 Ibs. ; and of those of least strength, 1557 Ibs. These bricks were of the ordinary form, and varied in thickness from 3'25 to 1'7 inches. It was also found that the thinner kinds of bricks were proportionally stronger than those which were thicker ; the greatest, mean, and least strengths of the former being respectively 4,088 Ibs., 2,954 Ibs., and 2,070 Ibs. In comparing weight with strength, it was found that the average weight of twenty-five bricks from dif- ferent districts, was 7*85 Ibs., and that the heaviest bricks were usually the strongest. The results of the following experiments are calculated according to a uniform standard : Tipton blue bricks, weighing 10 Ibs., gave 5,555 Ibs., 3,975 Ibs., and 2,801 Ibs., as the greatest, mean, and least degree of strength. Boston bricks, weighing 9'88 Ibs., gave 4,133 Ibs., 3,198 Ibs., and 2,616 Ibs., as the value of the same items. Roman hypocaust tiles from the ancient city of Uriconium, near Wroxeter, gave 4,670 Ibs., 3,567 Ibs., and 2,630 Ibs. The Leeds bricks, weighing 9" 17 Ibs., gave 4,133 Ibs., 3,198 Ibs., and 2,616 Ibs. Dutch clinkers, with a weight of only 6'56 Ibs., gave the respec- tive strength of 4,006 Ibs., 3,345 Ibs., and 2,542 Ibs. This is an exception to the general result of the heaviest bricks being the strongest. Lastly, the lightest London bricks, weighing 6'19 Ibs., gave 1,496 Ibs., 998 Ibs., and 366 Ibs. The experiments also gave evidence of the fact that bricks were unable to sustain for any length of time a weight considerably less than that which was originally required to break them ; for example, a Bal- timore brick, which required 850 Ibs. to break it, car- ried a weight of 735 Ibs. for ten hours only, and then broke. It must be borne in mind that the second INTRODUCTION. 11 result is represented in terms of the whole brick, for the sake of rendering the comparison more easy, although, of course, the experiment could only be made on the half brick. XII. Now that machine-made bricks are getting into general use, notwithstanding that some opposition has been made to their introduction, the following table may be interesting. It is a report of the results of some experiments on hand-made and machine-made bricks, with Messrs. Burton and Co/s hydraulic press. All the bricks were bedded upon a thickness of felt, and laid upon an iron-faced plate. Pressure to crack. Pressure to crusb. tons. tons. Good London grey stocks . . . 12-00 . . . 14-00 Best paviours to be got ... 14-00 . . . 23-00 Red bricks, not fully burnt . . . 13-75 . . . 25 05 Ditto, ordinary quality .... 13-00 . . . 26'25 Three white bricks made by Clay- ) ,- A . ., n .- ton and Co.'s machinery . ) 17 ' ' ' Ditto, second best, with four bricks 16'25 . . . 41'00 In the following pages we have described at con- siderable length the practice of brickmaking as carried on in Nottinghamshire, Staffordshire, Suffolk, and in the neighbourhood of London j and although the prac- tice of almost every county presents some local pecu- liarity, the reader who has carefully gone through these accounts will be enabled to understand the object of any processes not here described, and to form a toler- ably correct judgment as to whether the process of manufacture in any district is conducted in a judicious manner; or whether the brickmaker has merely fol- lowed the practices handed down by 'lis predecessors without any consideration as to the possibility of im- proving upon them. Before, however, entering upon the practical details of the subject, it is necessary that 12 RUDIMENTS OF THE the reader should have some knowledge of the general principles of brickmaking, and of the nature of the processes employed; and these we shall proceed to consider in the following chapter. CHAPTER I. GENERAL PRINCIPLES OF THE MANUFACTURE OF BRICKS AND TILES. 1. BRICKS. 1. The whole of the operations of the brickmaker may be classed under five heads, viz. : Preparation of brick earth. Tempering. Moulding. Drying. Burning. We propose in this chapter to describe these opera- tions one by one, pointing out the object to be effected by each, and comparing at the same time the different processes employed in various parts of this country for the same end. PREPARATION OF BRICK EARTH. 2. The qualities to be aimed at in making bricks for building purposes may be thus enumerated : Sound- ness, that is, freedom from cracks and flaws ; hardness, to enable them to withstand pressure and cross strain ; regularity of shape, that the mortar by which they are united may be of uniform thickness to insure unifor- mity of settlement ; uniformity of size, that all the bricks in a course may be of the same height ; uni- ART OF MAKING BRICKS AND TILES. 13 formity of colour, which is of importance only in ornamental work ; facility of cutting, to enable the bricklayer to cut them to any given shape, as required in executing all kinds of gauged work; lastly, for furnace-work, and all situations exposed to intense heat, infusibility. 3. Success in attaining the desired end depends chiefly on a proper selection of brick earths; their judicious preparation before commencing the actual process of brickmaking, as well as on the drying and burning of the bricks. The other operations are matters of minor importance. Brickmaking may be viewed in two lights as a science, and as an art. The former has been little studied, and is imperfectly under- stood ; whilst the latter has been brought to great perfection. 4. The argillaceous earths suitable for brickmaking may be divided into three principal classes, viz. : Pure clays, composed chiefly of alumina and silica, but containing a small proportion of other substances as iron, lime, &c.* (See Appendix II., page 263.) * The following analyses of various kinds of day are given in the second volume of the English translation of " Knapp*s Technological Chemistry." Cornish washed Kaolin. Stour- bridge fire clay. Pipeclay. Sandy clay. Blue clay. Brick clay. Silica . 46-32 64-10 53-66 66-68 46-38 49-44 Alumina 39-74 23-15 32-00 26-08 38-04 34-26 Oxide | 0-27 1-85 1-35 1-26 ro4 7-74 J of iron J Lime 0-36 0-40 0-84 1-20 1-48 Magnesia 0-44 0-95 trace trace trace 5-14 Potash 1 & soda J ) 12-67 - Water . j 10-00 12-08 5-14 13-57 1-94 99-80 100-05 99-49 lOO'OO 100-23 100-00 14 RUDIMENTS OF THE Marls, which may be described as earths containing it considerable proportion of lime. Loams, which may be described as light sandy clays. It very seldom happens that earths are found which are suited for the purpose of brickmaking without some admixture. The pure clays require the addition of sand, loam, or some milder earth ; whilst the loams are often so loose that they could not be made into bricks without the addition of lime to flux and bind the earth. Even when the clay requires no mixture, the difference in the working of two adjacent strata in the same field is often so great that it is advisable to mix two or three sorts together to produce uniformity in the size and colour of the bricks. 5. It appears,, then, that a chemical compound of silica and alumina is the principal ingredient in all brick earth.* This silicate of alumina, or pure clay alone, or those clays which contain but little sand, may, when beaten up with water into a stiff paste, be moulded with great ease into any shape ; but will shrink and crack in drying, however carefully and slowly the ope- ration be conducted ; and will not stand firing, as a red heat causes the mass to rend and warp, although it becomes very hard by the action of the fire. The addition of any substance which will neither combine with water, nor is subject to contraction, greatly remedies these defects, whilst the plastic quality of the clay is not materially affected. For this reason the strong clays are mixed with milder earth or with sand. The loams and marls used for brickmaking in the neighbourhood of London are mixed with lime and sifted breeze for the same purpose, and also to effect the fluxing of the earth, as will be presently described. * Some remarks on the plasticity of clay will be found in the AppeTidix. ART OF MAKING BRICKS AND TILES. 15 6. Fire clays or refractory clays are compounds of silica, alumina, and water, or hydrated silicates of alu- mina represented by the formula A1 2 O 3 , 2SiO 3 -f- 2HO. Such clays owe their refractory qualities to their com- parative freedom from lime, magnesia, metallic oxides, and similar substances which act as fluxes. Few clays, however, exist in nature according to this pure type. The composition and quality of clays in con- tiguous beds in the same pit, and even of clay from the same contiguous horizontal bed, may vary. "If we compare different clays together in respect to elementary composition, we find the relation between the silica and alumina to be extremely variable, and accordingly, the formulae which have been proposed to express their rational constitution are very discordant. This is in great measure to be explained by the fact, that in many clays a large proportion of silica exists uncombined either as sand, or in a much finer state of division. The grittiness of a clay is due to the presence of sand."* Fire-bricks are used in those parts of furnaces where the heat would soon destroy ordinary bricks. They are made of various shapes and sizes as required, and are 3ften produced, as in the iron works of South Wales, on the spot. The clay is ground between rolls, or under edge stones, and kneaded by treading. The bricks are made by hand in moulds ; they are carefully dried in stoves, and burnt at a high temperature in closed kilns. Burnt clay in powder is sometimes mixed with the raw clay. Stourbridge clay is celebrated for the manufacture of fine bricks, but clay from the coal-measures is also largely used. All these bricks have a pale brownish colour, but they are sometimes mottled with dark spots, * " Metallurgy," by John Percy, M.D., E.R.S., Lecturer on Metallurgy at the Government School of Mines. London, 1861. 16 RUDIMENTS OF THE which Dr. Percy refers to the presence of particles of iron pyrites. The Dinas fire-brick consists almost entirely of silica, the material beiDg obtained from the rock of that name in the Vale of Neath. It lies on the limestone, and occasionally intermixes with it, and contains probably about 5 per cent, of calcareous matter. The bricks have extraordinary fire-proof qualities. The material had long been used as a sand, and many attempts were made to form it into bricks, without success, until a method was contrived by the late Mr. W. W. Young, when in 1822 a company was formed for the manufacture of these bricks. The mode of making the Dinas brick was long kept secret, but a number of original details concerning it are given in Dr. Percy's work. The material which is called clay is found at several places in the Vale of Neath in the state of rock, and disintegrated like sand. The colour when dry is pale grey. The rock is crushed to coarse powder between iron rolls ; it softens by exposure to the air, but some of it is too hard to be used. " The powder of the rock is mixed with about 1 per cent, of lime and sufficient water to make it cohere slightly by pressure. This mixture is pressed into iron moulds, of which two are fixed under one press, side by side. The mould, which is open at the top and bottom, like ordinary brick-moulds, is closed below by a moveable iron plate, and above by another plate of iron, which fits in like a piston, and is connected with a lever. The machine being adjusted, the coarse mixture is put into the moulds by a workman, whose hands are protected by stout gloves, as the sharp edges of the fragments would otherwise wound them : the piston is then pressed down, after which the moveable bed of iron on which the brick is formed is lowered and taken away with the ART OF MAKING BRICKS AND TILES. 17 brick upon it, as it is not sufficiently solid to admit of being carried in the usual manner. The bricks are dried on these plates upon floors warmed by flues passing underneath; and when dry they are piled in a circular closed kiln covered with a dome, similar to kilns in which common fire bricks are burned. About seven days of hard firing are required for these bricks, and about the same time for the cooling of the kiln. One kiln contains 32,000 bricks, and consumes 40 tons of coal, half free-burning and half binding. The price (1859) is 605. the thousand,"* The fracture of one of these bricks shows irregular particles of quartz, and the lime which is added acts as a flux, causing them to agglutinate. These bricks expand by heat, while bricks made of fire clay contract. Hence they are useful for the roofs of reverberatory furnaces, and for parts where solid and compact lining is required. These siliceous bricks must not be exposed to the action of slags rich in metallic oxides. 7. Fire clay, being an expensive article, is frequently mixed with burnt clay, often as much as two parts by weight to one of Stourbridge clay. Broken crucibles, old fire bricks, and old glass-pots ground to powder are also mixed with fire clay. 8. Fire clay is found throughout the coal measures, but that of Stourbridge is considered to be the best, as it will bear the most intense heat that can be produced without becoming fused. Next in esteem to those of Stourbridge are the Welsh fire bricks, but they will not bear such intense heat. Excellent fire bricks are made at Newcastle and Glasgow. Fire bricks are made near Windsor, at the village of Hedgerly, from a sandy * In this year bricks were much cheaper than they have been since. 18 RUDIMENTS OP THE loam known by the name of Windsor loam, and much used in London for fire-work, and also by chemists for luting their furnaces, and for similar purposes. The relative merits of Windsor, Welsh, Stourbridge, and other fire bricks, are best shown by their commer- cial value. The following items, extracted from the "Builders' and Contractors' Price Book for 1868," edited by G. R. Burnell, exhibit their relative cost : Per 1000. s. d. Windsor fire bricks . . . .540 Welsh ditto 540 Stourbridge ditto 700 Newcastle ditto 550 Alloa ditto 580 Dorset ditto 4 16 9. Bricks made of refractory clay, containing no lime or alkaline matter, are baked rather than burnt ; and their soundness and hardness depend upon the fineness to which the clay has been ground, and the degree of firing to which it has been exposed. 10. It is very seldom that the common clays are found to be free from lime and other fluxes ; and when these are present in certain proportions, the silica of the clay becomes fused at a moderate heat, and cements the mass together. Some earths are very fusible, and, when used for brickmaking, great care is requisite in firing the bricks to prevent them from running together in the kiln. 11. The earths used for brickmaking near London are not clays, but loams and marls. To render these earths fit for brickmaking, they are mixed with chalk ground to a pulp in a wash -mill. This effects a double purpose, for the lime not only imparts soundness to the bricks, acting mechanically to prevent the clay from shrinking and cracking, but also assists in fusing the ART OF MAKING BRICKS AND TILES. 19 siliceous particles ; and when present in sufficient quan- tity,, corrects the evil effects of an overdose of sand, as it takes up the excess of silica that would otherwise remain in an uncombined state. 12. It will be seen from these remarks that we may divide bricks generally into two classes baked bricks made from the refractory clays, and burnt or vitrified bricks made from the fusible earths. The fusible earths are the most difficult of treatment, as there is considerable practical difficulty in obtaining a sufficient degree of hardness without risking the fusion of the bricks ; and it will be found that ordinary kiln-burnt bricks, made from the common clays, are for the most part of inferior quality, being hard only on the outside, whilst the middle is imperfectly burnt, and remains tender. The superior quality of the London malm bricks, which are made from a very fusible com- pound, is chiefly due to the use of sifted breeze,* which is thoroughly incorporated with the brick earth in the pugmill, so that each brick becomes a kind of fire ball, and contains in itself the fuel required for its vitrifica- tion. In building the clamps the bricks are stacked close together, and not as in ordinary kiln-burning, in which openings are left between the bricks to allow of the distribution of the heat from the live holes. The effect of these arrangements is to produce a steady uni- form heat, which vitrifies the bricks without melting them. Those bricks which are in contact with the live holes or flues melt into a greenish black slag. 13. Cutters, that is, bricks which will bear cutting and rubbing to any required shape, are made from sandy loams, either natural or artificial. In many * Breeze is a casual mixture of cinders, small coal, and ashes, such as is collected by the dustmen. 20 RUDIMENTS OF THE districts cutters are not made, there being no suitable material for the purpose. Bricks made from pure clays containing but little silica are hard and tough, and will not bear cutting. 14. We now come to the consideration of colour, which depends on the varying proportions of the hydrated oxide of iron in the clay, which change according to the amount of heat to which the bricks are subjected, and not on their natural colour before burning. This should be borne in mind, because brick- makers often speak of clays as red clay, white clay, &c., according to the colour of the bricks made from them, without any reference to their colour in the unburnt state. If iron be present in clay without lime or similar substances, the colour produced at a moderate red heat will be red, the intensity of colour depending on the proportion of iron. The bind or shale of the coal mea- sures burns to a bright clear red. If the clay be slightly fusible, an intense heat vitrifies the outside of the mass and changes its colour, as in the case of the Staffordshire bricks, which, when burnt in the ordinary way, are of a red colour, which, however, is changed to a greenish blue by longer firing at a greater heat. The addition of lime changes the red produced by the oxide of iron to a cream brown, whilst magnesia brings it to a yellow. Few clays produce a clear red, the majority burning of different shades of colour, varying from reddish brown to a dirty red, according to the propor- tion of lime and similar substances which they contain. Some clays, as the plastic clays of Suffolk, Devon- shire,* and Dorsetshire, burn of a clear white, as may * The plastic clay of Devonshire and Dorsetshire forms the basis of the English stone ware. It is composed of about seventy-six parts of ART OF MAKING BRICKS AND TILES. 21 be seen in the Suffolk white bricks, which are much esteemed for their soundness and colour. The London malms have a rich brimstone tint, which is greatly assisted by the nature of the sand used in the process of moulding. 15. By employing metallic oxides and the ochreous metallic earths, ornamental bricks are made of a variety of colours. This, however, is a branch of brick- making which has as yet received very little attention, although, with the rising taste for polychromatic deco- ration, it is well worthy of consideration. (See note, page 270.) Yellow clampt burnt bricks are made in the vicinity of the metropolis, and in other* situations where similar material and fuel are readily obtained. White bricks are made from the plastic clays of Devonshire and Dorsetshire, and also Cambridgeshire, Norfolk, Suffolk, and Essex, as well as in other counties. Red bricks are made in almost every part of England ; but the fine red or cutting brick is not generally made. Blue bricks are made in Staffordshire, and are much used in that part of England. Sound and well-burnt bricks are generally of a clear and uniform colour, and when struck together will ring with a metallic sound. Deficiency in either of these points indicates inferiority. 16. Bricks sufficiently light to float in the water were known to the ancients. This invention, however, was completely lost until rediscovered at the close of the silica and twenty-four of alumina, with some other ingredients in very small proportions. This clay is very refractory in high heats, a property which, joined to its whiteness when burned, renders it peculiarly valuable for pottery, &c. * Yellow clampt burnt bricks are made at Margate, in Kent, from the patches of plastic clay lying in the hollows of the chalk. The older part of Margate is built of red bricks said to have been brought from Canter- bury. 22 RUDIMENTS OF THE last century by M. Fabbroni, who published an account of his experiments. M. Fabbroni succeeded in making floating bricks of an infusible earth called fossil meal, which is abundant in some parts of Italy. Bricks made of this earth are only one-sixth of the weight of common clay bricks, on which account they would be of great service in vaulting church roofs, and for similar pur- poses. Ehrenberg, the eminent German microscopist, showed that this earth consists almost entirely of the frustules or siliceous skeletons of various kinds of minute water plants. (See note, page 271.) Having thus briefly sketched the leading principles which should be our guide in the selection of brick earth, we will now proceed to describe the several pro- cesses by which it is brought into a fit state for use. 17. Unsoiling. The first operation is to remove the mould and top soil, which is wheeled away, and should be reserved for resoiling the exhausted workings when they are again brought into cultivation. In London the vegetable mould is called the encallow, and the operation of removing it, encallowing. 18. Clay-digging and Weathering. The brick earth is dug in the autumn, and wheeled to a level place pre- pared to receive it, when it is heaped up to the depth of several feet, and left through the winter months to be mellowed by the frosts, which break up and crumble the lumps. At the commencement of the brickmaking season, which generally begins in April, the clay is turned over with shovels, and tempered either by spade labour or in the pugmill ; sufficient water being added to give plasticity to the mass. 19. During these operations any stones which may be found must be carefully picked out by hand, which is a tedious and expensive operation, but one which ART OF MAKING BRICKS AND TILES. 23 cannot be neglected with impunity, as the presence of a pebble in a brick generally causes it to crack in drying, and makes it shaky and unsound when burnt. If the earths to be used are much mixed with gravel, the only remedy is to wash them in a trough filled with water, and provided with a grating sufficiently close to prevent even small stones from passing through, and by means of which the liquid pulp runs off into pits prepared to receive it, where it remains until, by evaporation, it becomes sufficiently firm to be used. This process is used in making cutting bricks, which require to be of perfectly uniform texture throughout their whole sub- stance ; but it is tedious and expensive. In working the marls of the midland districts, much trouble is experienced from the veins of skerry or im- pure limestone with which these earths abound. If a small piece of limestone, no bigger than a pea, is allowed to remain in the clay, it will destroy any brick into which it finds its way. The carbonic acid is driven off by the heat of the kiln, and forces a vent through the side of the brick, leaving a cavity through which water finds its way, and the first sharp frost to which such a brick may be exposed generally suffices to destroy the face. 20. Grinding. To remedy this serious evil, cast-iron rollers are now generally used throughout the midland districts for grinding the clay and crushing the pieces of limestone found in it, and their introduction has been attended with very beneficial results. The clays of the coal measures contain much ironstone, which requires to be crushed in the same manner. In many yards the grinding of the clay is made to form part of the process of tempering, the routine being as follows : clay-getting, weathering, turning over and 24 RUDIMENTS OF THE wheeling to mill, grinding, tempering, and moulding. In Staffordshire the clay is not only ground, but is also pugged in the process of tempering, as described in chap. iv. art. 38 ; the routine is then as follows : clay-getting, grinding, weathering, turning over, pug- ging, moulding. At a well-mounted brickwork in Nottingham, belong- ing to Moses Wood, Esq., the clay used in making the best facing bricks is treated as follows : it is first turned over and weathered by exposure to frost ; it is then again turned over, and the stones picked out by hand, after which it is ground between rollers set very close together, and then left in cellars to ripen for a year or more, before it is finally tempered for the use of the moulder. The bricks made from clay thus prepared are of first-rate quality, but the expense of the process is too great to allow of much profit to the manufacturer. 21. Washing. The preparation of brick-earth in the neighbourhood of London is effected by processes quite different from those just described. For marl or malm bricks, the earth is ground to a pulp in a wash-mill, and mixed with chalk previously ground to the consistence of cream; this pulp, or, as it is technically called, malm, is run off through a fine grating into pits pre- pared to receive it, and there left, until by evaporation and settlement, it becomes of sufficient consistency to allow a man to walk upon it. It is then soiled, i.e. covered with siftings from domestic ashes, and left through the winter to mellow. At the commencement of the brickmaking season the whole is turned over, and the ashes thoroughly incorporated with the earth in the pugmill. In making common bricks, the whole of the earth is not washed, but the unwashed clay is AST OF MAKING BRICKS AND TILES. 25 heaped up on a prepared floor, and a proportion of liquid malm poured over it, after which it is soiled in the same way as for making malms. These processes are well calculated to produce sound, hard, and well-shaped bricks. The washing of the clay effectually frees it from stones and hard lumps, whilst the mixing of the chalk and clay in a fluid state ensures the perfect homogeneousness of the mass, and enables the lime to combine with the silica of the clay, which would not be the case unless it were in a state of minute division. 22. There are very few earths suitable in their natural state for making cutters. They are therefore usually made of washed earth mixed up with a proportion of sand. Without the addition of sand the brick would not bear rubbing, and it would be very difficult to bring it to a smooth face. 23. It maybe here observed that sufficient attention is not generally paid to the preparation of brick-earth, as it too frequently happens that the clay is dug in the spring instead of the autumn, in which case the benefit to be derived from the winter frosts is quite lost. The use of rollers, to a certain extent, counterbalances this ; but bricks made of clay that has been thoroughly weathered are sounder and less liable to warp in the kiln. TEMPERING. 24. The object of tempering is to bring the prepared brick earth into a homogeneous paste, for the use of the moulder. The old-fashioned way of tempering was to turn the clay over repeatedly with shovels, and to tread it over by horses or men, until it acquired the requisite plasti- city. This method is still practised in many country 26 RUDIMENTS OF THE yards ; but where the demand for bricks is extensive, machinery is usually employed, the clay being either ground between rollers or pugged in a pugmill. This latter process is also called grinding, and, therefore, in making inquiries respecting the practice of particular localities, the reader should be careful that he is not misled by the same name being applied to processes which are essentially different. When rollers are used in the preliminary processes, the labour of tempering is much reduced. Their use is, however, most generally confined to the process of tempering, which is then effected as follows : The clay, which has been left in heaps through the winter to mellow, is turned over with wooden shovels (water being added as required), and wheeled to the mill, where it is crushed between the rollers, and falls on a floor below them, where it is again turned over, and is then ready for use. When the clay is sufficiently mild and free from lime and ironstone as not to require crushing, tempering by spade labour and treading is generally adopted ; but in the districts where rollers are used, the brick- earths are generally so indurated that a great proportion could not be rendered fit for use by the ordinary processes. The advantages and disadvantages of the use of rollers are considered at some length in chap. iii. art. 4. 25. In making bricks for railway works, which has been done lately to an almost incredible extent, con- tractors are generally little anxious as to the shape or appearance of the article turned out of the kiln, pro- vided it be sufficiently sound to pass the scrutiny of the inspector or resident engineer. As the whole process of railway brickmaking often occupies but a few weeks from the first turning over of the clay to the laying of ART OF MAKING BRICKS AND TILES. 27 the bricks in the work, the use of rollers in such cases is very desirable, as a partial substitute for weathering. On the line of the Nottingham and Grantham Railway several millions of bricks have been made as follows : The clay is first turned over with the spade, and watered and trodden by men or boys, who, at the same time, pick out the stones. It is then wheeled to the mill and ground ; after which it is turned over a second time, and then passed at once to the moulding table. 26. Although in many country places, where the demand for bricks is very small, tempering is still per- formed by treading and spade labour, the pugmill is very extensively used near London, and in most places where the brick-earth is of mild quality, so as not to require crushing, and the demand for bricks sufficiently constant to make it worth while to erect machinery. The pugmill used near London is a wooden tub, in shape an inverted frustrum of a cone, with an upright revolving shaft passing through its centre, to which are keyed a number of knives, which, by their motion, cut and knead the clay, and force it gradually through the mill, whence it issues in a thoroughly tempered state, fit for the use of the moulder. Some contend that the pug- mill is no improvement on the old system of tempering by manual labour; but, without entering into this ques- tion, there can be no doubt that it does its work very thoroughly, and its use prevents the chance of the tem- pering being imperfectly performed through the negli- gence of the temperers. In the London brickfields the process of tempering is conducted as follows: The malm, or maimed brick-earth, as the case may be, is turned over with the spade, and the soil* (ashes) dug * Soil, i.e. ashes, must not be confounded with soil, vegetable mouldy which is in some places mixed with strong clay, to render it milder. c 2 28 RUDIMENTS OF THE into it, water being added as may be necessary. It is then barrowed to the pugmill, and being thrown in at the top, passes through the mill, and keeps continually issuing at a hole in the bottom. As the clay issues from the ejectment hole, it is cut into parallel opipedons by a labourer, and, if not wanted for immediate use, is piled up and covered with sacks to prevent it from becoming too dry. In Staffordshire steam power is used for driving both rollers and pugmill, and the case of the latter is usually a hollow cast-iron cylinder. MOULDING. 27. A brick-mould is a kind of box without top or bottom, and the process of moulding consists in dashing the tempered clay into the mould with sufficient force to make the clot completely fill it, after which the superfluous clay is stricken with a strike, and the newly- made brick is either turned out on a drying floor to harden, or on a board or pallet, on which it is wheeled to the hack-ground. The first mode of working is known as slop moulding, because the mould is dipped in water, from time to time, to prevent the clay from adhering to it. The second method may be distinguished as pallet moulding ; and in this process the mould is not wetted, but sanded. These distinctions, however, do not universally hold good, because in some places slop-moulded bricks are turned out on pallets. 28. These differences may, at first sight, appear trivial, but they affect the whole economy of a brick- work. In slop moulding the raw bricks are shifted by hand from the moulding table to the drying floor, from the drying floor to the hovel or drying shed, and from ART OF MAKING BRICKS AND TILES. 29 the hovel to the kiln. It is therefore requisite that the works should be laid out so as to make the distance to which the bricks have to be carried the shortest pos- sible. Accordingly,* the kiln is placed in a central situation in a rectangular space, bounded on two or more sides by the hovel, and the working floors are formed round the outside of the latter. In the process of slop moulding the newly-made brick is carried, mould and all, by the moulder's boy to the flat, or drying floor, on which it is carefully deposited ; and whilst this is being done, the moulder makes a second brick in a second mould, the boy returning with the first mould by the time the second brick is being finished. As soon, therefore, as the floor becomes filled for a certain distance from the moulding table, the latter must be removed to a vacant spot, or the distance to which the bricks must be carried would be too great to allow of the boy's returning in time with the empty mould. 29. In pallet moulding but one mould is used. Each brick, as it is moulded, is turned out on a pallet, and placed by a boy on a hack-barrow, which, when loaded, is wheeled away to the hack-ground, where the bricks are built up to dry in low walls called hacks. One moulder will keep two wheelers constantly employed, two barrows being always in work, whilst a third is being loaded at the moulding stool. When placed on the barrow, it is of little consequence (comparatively) whether the bricks have to be wheeled 5 yards or 50 ; and the distance from the moulding stool to the end of the hacks is sometimes considerable. SO. The moulding table is simply a rough table, made * There are, of course, some exceptions; but, where practicable, the drying floors and hovel are placed close to the kilns. SO RUDIMENTS OF THE in various ways in different parts of the country, but the essential differences are, that for slop moulding the table is furnished with a water trough, in which the moulds are dipped after each time of using ; whilst in pallet moulding, for which the mould is usually sanded and not wetted, the water trough is omitted, and a page (see account of Brickmaking as practised in London) is added, on which the bricks are placed preparatory to their being shifted to the hack-barrow. 31. Brick moulds are made in a variety of ways. Some are made of brass cast in four pieces and riveted together ; some are of sheet iron, cased with wood on the two longest sides ; and others again are made entirely of wood, and the edges only plated with iron. Drawings and detailed descriptions of each of these constructions are given in the subsequent chapters. In using wooden moulds the slop-moulding process is almost necessary, as the brick would not leave the sides of the mould unless it were very wet. Iron moulds are sanded, but not wetted. Brass, or, as they are techni- cally called, copper moulds, require neither sanding nor wetting, do not rust, and are a great improvement on the common wooden mould formerly in general use. They, however, are expensive, and will not last long, as the edges become worn down so fast that the bricks made from the same mould at the beginning and end of a season are of a different thickness, and cannot be used together. This is a great defect, and a metal mould which will not rust nor wear is still a great desi- deratum. It is essential that the sides of the mould should be sufficiently stiff not to spring when the clay is dashed into it, and it is equally requisite that it should not be made too heavy, or the taking-off boy would not be able to carry it to the floor. A common ART OF MAKING BRICKS AND TILES. 31 copper mould weighs about 4 Ibs., and, with the wet brick in it, about 12 Ibs., and this weight should not be exceeded. 32. There is a great difference in the quantity of bricks turned out in a given time by the pallet moulding and by the slop moulding processes. In slop moulding 10,000 per week is a high average, whilst a London moulder will turn out 36,000 and upwards in the same period. This arises in a great measure from the cir- cumstance that in pallet moulding the moulder is assisted by a clot moulder, who prepares the clot for dashing into the mould ; whilst in slop moulding the whole operation is conducted by the moulder alone. 33. In some places the operation of moulding par- takes both of slop moulding and pallet moulding, the bricks being turned out on pallets and harrowed to the hack-ground, whilst the moulds are wetted as in the ordinary process of slop moulding. 34. The substitution of machinery for manual labour in the process of moulding has long been a favourite subject for the exercise of mechanical talent ; but although a great number of inventions have been pa- tented, there are very few of them that can be said to be thoroughly successful. The actual cost of moulding bears so small a proportion to the total cost of brick- making, that in small brickworks the employment of machinery would effect no ultimate saving, and> there- fore, it is not to be expected that machinery will ever be generally introduced for brick moulding. But in works situated near large towns, or in the execution of large engineering works, the case is very different, and a contractor who requires, say, 10,000,000 of bricks, to be made in a limited time, for the construction of a tunnel or a viaduot, can employ machinery with great 32 RUDIMENTS OF THE advantage. A chapter on brickmaking machines will be found in another part of this volume. 35. It has been much discussed by practical men, whether bricks moulded under great pressure are better than those moulded in the ordinary way. They are of denser texture, harder, smoother, heavier, and stronger than common bricks. On the other hand, it is difficult to dry them, because the surfaces become over-dried and scale off before the evaporation from the centre is completed. Their smoothness lessens their adhesion to mortar ; and their weight increases the cost of carriage, and renders it impossible for a bricklayer to lay as many in a given time as those of the ordinary weight. On the whole, therefore, increased density may be con- sidered as a disadvantage, although, for some purposes, dense bricks are very valuable. 36. Mr. Prosser, of Birmingham, has introduced a method of making bricks, tiles, and other articles by machinery, in which no drying is requisite, the clay being used in the state of a nearly dry powder. The clay from which floor-tiles and tesserae are made is first dried upon a slip-kiln,* as if for making pottery, then ground to a fine powder, and in that state subjected to heavy pressure f in strong metal moulds : by this means the clay is reduced to one-third of its original thickness, and retains sufficient moisture to give it cohesion. The articles thus made can be handled at once, and carried direct to the kiln. In some experiments tried for ascer- taining the resistance of bricks and tiles thus made to * The slip-kiln is a stone trough bottomed with fire tiles, under which runs a furnace flue. It is used in the manufacture of pottery for evapo- rating the excess of water in the slip, or liquid mixture of clay and ground flints, which is thus brought into the state of paste. f It is a common but an erroneous notion, that articles made by Mr. Prosser's process are denser than similar articles made in the common vay : the reverse is the fact. ART OF MAKING BRICKS AND TILES. 33 a crushing force, a 9-inch brick sustained a pressure of 90 tons without injury. 37. Mr. Prosser's method offers great advantages for the making of ornamental bricks for cornices, bas- reliefs, floor-tiles, tesselated pavements, &c. Screw presses are used to a considerable extent for pressing bricks when partially dry, to improve their shape and to give them a smooth face ; but we have in many in- stances found pressed bricks to scale on exposure to frost, and much prefer dressing the raw brick with a beater, as described in chap. iii. art. 34. 38. The great practical difficulty in making moulded bricks for ornamental work is the warping and twisting to which all clay ware is subject more or less in the process of burning. This difficulty is especially felt in making large articles, as wall copings, &c. In moulding goods of this kind it is usual to make perforations through the mass, to admit air to the inside, without which precaution it would be impossible to dry them thoroughly; for, although the outside would become hard, the inside would remain moist, and, on being subjected to the heat of the kiln, the steam would crack and burst the whole. The Brighton Viaduct, on the Lewes and Hastings Railway, has a massive white brick * dentil cornice, the bricks for which were made in Suffolk after several unsuccessful attempts to make bricks of still larger size. The thickness of the bricks first proposed presenting an insurmountable obstacle to their being properly dried, their dimensions were reduced, and large perforations were made in each brick to reduce its weight, and to enable it to be more thoroughly and uniformly dried ; * Brick was preferred to stone on account of the expense of the lattei material. c 3 34 RUDIMENTS OF THE and by adopting this plan the design was successfully carried into execution. 39. The usual form of a brick is a parallelopipedon, about 9 in. long, 4 in. broad, and 3 in. thick, the exact size varying with the contraction of the clay. The thickness need not bear any definite proportion to the length and breadth, but these last dimensions require nice adjustment, as the length should exceed twice the breadth by the thickness of a mortar joint. 40. Bricks are made of a variety of shapes for par- ticular purposes, as enumerated in art. 60, chap. iii. The manufacture of these articles is principally carried on in the country, the brickfields in the vicinity of the metro- polis supplying nothing but the common building brick. 41. A point of some little importance may be here adverted, to, viz., is any advantage gained by forming a hollow in the bed of the brick to form a key for the mortar ? There are various opinions on this point ; but we think it may be laid down as a principle, that if it is useful on one side it will be still better on both, so as to form a double key for the mortar. In London, the brick mould is placed on a stock board, which is made to fit the bottom of the mould ; and the relative positions of the two being kept the same, no difficulty exists in forming a hollow on the bottom of the brick, this being effected by a kick fastened on the stock board. But this could not be done on the upper side, which is stricken level. In slop moulding, the mould is simply laid on the moulding stool, or on a moulding board much larger than the mould, and both sides of the brick are flush with the edges of the mould, no hollow being left, unless the moulder think fit to make one by scoring the brick with his fingers, which is sometimes done. When machinery is used in moulding, it is equally easy ART OF MAKING BRICKS AND TILES. 35 to stamp the top and the bottom of the brick ; and we have seen, at the Butterly Ironworks, in Derbyshire, excellent machine-made bricks of this kind made in the neighbourhood. 42. Amongst the many inventions connected with brickmaking which have been from time to time brought before the public, ventilating bricks deserve attention, from the facilities they afford for warming and venti- lating buildings. The annexed figures show the form of the bricks and the way in which they are used. Fig. 1. Fig. 2. Fig. 1 is a representation of a 9-in. wall, built with the ventilating bricks, with one common brick used at the angle of each course. Fig. 2 is a representation of a 14-in. wall ; the half ventilating brick, being used alternately in the courses, forms a perfect and effectual bond. Fig. 3 is an isometrical drawing showing the venti- lating spaces. DRYING. 43. The operation of drying the green bricks requires great care and attention, as much depends upon the 36 ' RUDIMENTS OF THE manner in which they are got into the kiln. The great point to be aimed at is to protect them against sun, wind, rain, and frost, and to allow each brick to dry uniformly from the face to the heart. Slop-moulded bricks are usually dried on flats or drying floors, where they remain from one day to five or six, according to the state of the weather. When spread out on the floor they are sprinkled with sand, which absorbs superfluous moisture, and renders them less liable to be cracked by the sun's rays. After remaining on the floors until sufficiently hard to handle without injury, they are built up into hacks under cover, where they remain from one to three weeks, until ready for the kiln. In wet weather they are spread out on the floor of the drying shed, and great care must then be taken to avoid drafts, which would cause the bricks to dry faster on one side than the other. To prevent this, boards set edgeways are placed all round the shed to check the currents of air. The quantity of ground required for drying bricks in this manner is comparatively small, as they remain on the floors but a short time, and occupy little space when hacked in the hovels. The produce of a single moulding stool by the slop-moulding process seldom exceeds 10,000 per week, and the area occupied by each stool is, therefore, small in proportion. Half an acre for each kiln may be considered ample allowance for the working floor and hovel. 44. In places where brickmaking is conducted on a large scale, drying sheds are dispensed with, and the hacks are usually built in the open air, and protected from wet, frost, and excessive heat, by straw, reeds, matting, canvas screens, or tarpaulins ; all of which we have seen used in different places. ART OF MAKING BRICKS AND TILES. 37 45. Bricks intended to be clamp burnt are not dried on flats, but are hacked at once on leaving the moulding stool, antl remain in the hacks much longer than bricks intended to be kilned. This is rendered necessary by the difference between clamping and kilning. In the latter mode of burning, the heat can be regulated to great nicety, and if the green bricks, when first placed in the kiln, be not thoroughly dried, a gentle heat is applied until this is effected. In clamping, however, the full heat is attained almost immediately, and, therefore, the bricks must be thoroughly dried, or they would fly to pieces. In the neighbourhood of London a good moulder, with his assistants, will turn out from 30,000 to 40,000 bricks per week, and the clamps contain from 60,000 to 120,000 bricks and upwards. From these combined causes, the area occupied by each stool is greater than in making slop-moulded bricks. In Mr. Bennett's brick-ground at Cowley, ten stools occupy twenty acres. 46. At the risk of wearying the patience of the reader, we recapitulate the leading points on which depends the difference of area required for each mould- ing stool in making : Slop-moulded bricks, hacked under London pallet-moulded sand stocks, cover, and burnt in kilns. burnt in clamps. Dried one day on flats ... 1st Hacked at once. Closely stacked in hacks 17) f Bricks loosely stacked in hacks, courses high, placed close 2nd] 8 courses high and 2 bricks together undercover . . . j f wide > th , 9 /t. spaces be- l_ tween the hacks. Remain in shed 10 to 16 days 3rd Remain in hacks 3 to 6 weeks. Rate of production per stool, 1 . , /A gang will turn out 30,000 to about 10,000 weekly . . ./ a 1 40,000 per week. Kiln holds about 30,000 bricks, 1 f Clamp contains 60.000 to and may be fired once in 10 I 5th \ 120,000 bricks, and burns days J [ from 2 to 6 weeks. 47. It is scarcely necessary to observe that different 38 RUDIMENTS OF THE clays require different treatment, according to their composition, some bricks bearing exposure to sun and rain without injury, whilst others require to be carefully covered up to keep them from cracking under similar circumstances. [See Appendix.] Superior qualities of bricks are generally dressed with a beater when half dry, to correct any twisting or warping which may have taken place during the first stage of drying. BURNING. 48. Bricks are burnt in clamps and in kilns. The latter is the common method, the former being only employed in burning bricks made with ashes or coal- dust. It should be observed, however, that the name of clamp is applied also to a pile of bricks arranged for burning in the ordinary way, and covered with a temporary casing of burnt brick to retain the heat ; but this must not be confounded with close-clamping as practised in the neighbourhood of London. 49. The peculiarity of clamp burning is that each brick contains in itself the fuel necessary for its vitrifi- cation ; the breeze or cinders serving only to ignite the lower tiers of bricks, from which the heat gradually spreads over the whole of the clamp. No spaces are left between the bricks, which are closely stacked, that the heat to which they are exposed may be as uniform as possible. It is unnecessary here to go into the details of clamping, as they are very fully given in the account of London Brickmaking. [See also Ap- pendix.] 50. A kiln is a chamber in which the green bricks are loosely stacked, with spaces between them for the passage of the heat ; and baked by fires placed either ART OF MAKING BRICKS AND TILES. 39 in arched furnaces under the floor of the kiln, or in fire holes formed in the side walls. There are many ways of constructing kilns, and scarcely any two are exactly alike; but they may be divided into three classes : 1st. The common rectangular kiln with fire-holes in the side walls. This is formed by building four walls enclosing a rectangular space, with a narrow doorway at each end, and narrow-arched openings in the side walls exactly opposite to each other. The bricks are introduced through the doorways, and loosely stacked with considerable art, the courses being crossed in a curious manner, so as to leave continuous openings from top to bottom of the pile to distribute the heat. In the lower part of the kiln narrow flues are left, about 8 in. wide and about 2 ft. or 3 ft. high, connecting the fire-holes in the side walls. The kilns having been filled, the doorways are bricked up and plastered with clay to prevent the ingress of cold air ; the top of the kiln is covered with old bricks, earth, or boards, to retain the heat, and the firing is carried on by burning coal in the fire-holes. A low shed is generally erected on each side of the kiln to protect the fuel and fireman from the weather, and to prevent the wind from urging the fires. The details of the management of a kiln are given in another place, and need not be here repeated. This kind of kiln is he simplest that can well be adopted, and is in use in Holland at the present day. It is the kiln in common use through the Midland districts. 2nd. The rectangular kiln with arched furnaces. This consists also of a rectangular chamber ; but differs from the first in having two arched furnaces running under the floor the whole length of the kiln, the furnace 40 RUDIMENTS OF THE doors being at one end. The floor of the kiln is formed like lattice-work, with numerous openings from the furnaces below, through which the heat ascends. The top of the kiln is covered by a moveable wooden roof, to retain the heat, and to protect the burning bricks from wind and rain. These kilns are used in the east of England. 3rd. The circular kiln or cupola. This is domed over at the top, whence its name is derived. The fire-holes are merely openings left in the thickness of the wall, and are protected from the wind by a wall built round the kiln at a sufficient distance to allow the fireman room to tend the fires. These cupolas are used in Staf- fordshire and the neighbourhood, and the heat employed in them is very great. Drawings of a cupola are given in chap, iv., with an account of the manner in which the firing is conducted, and therefore it is unnecessary to enter here upon any of these details. 51. The usual method of placing bricks in the kiln is to cross them, leaving spaces for the passage of the heat, but there are objections to this, as many bricks show a different colour, where they have been most exposed to the heat. Thus in many parts of the country, the bricks exhibit a diagonal stripe of a lighter tint than the body of the brick, which shows the portion that has been most exposed. In burning bricks that require to be of even colour, this is guarded against by placing them exactly on each other. On first lighting a kiln the heat is got up gently, that the moisture in the bricks may be gradually evaporated. When the bricks are thoroughly dried, which is known by the steam ceasing to rise, the fires are made fiercer, and the top of the kiln is covered up with boards, turf, old bricks, or soil, to retain the heat. As ART OP MAKING BRICKS AND TILES. 41 the heat increases, the mouths of the kiln are stopped to check the draft, and when the burning is completed, they are plastered over to exclude the air, and the fires are allowed to go out. After this the kiln is, or should be, allowed to cool very gradually, as the soundness of the bricks is much injured by opening the kiln too soon. Pit coal is the fuel commonly used, and the quantity required is about half a ton per 1,000 bricks ; but much depends on the quality of the coal, the construction of the kiln, and the skill with which the bricks are stacked. Wood is sometimes used as fuel in the preliminary stage of firing, but not to a great extent. In a letter received on the management of the Suffolk kilns, the writer says, " The usual mode of firing bricks in Suffolk is in a kiln. The one near me, belonging to a friend of mine, is constructed to hold 40,000 ; it is about. 20 ft. long and 15 ft. broad, and is built upon two arched furnaces that run through with openings to admit the heat up. The bricks are placed in the usual way for burning, by crossing so as to admit the heat equally through, when the whole mass becomes red hot : the first three or four days, wood is burnt in what is called the process of annealing; with this they do not keep up a fierce fire. After this from 12 to 14 tons of coal are consumed in finishing the burning. Private individuals sometimes make and clamp 20,000 or 30,000 without a kiln ; then there is great waste, and the bricks are not so well burnt. 52. In the preceding pages we have briefly sketched the operations of brickmaking, and the principles on which they depend. In the following chapters the reader will find these operations described in detail, as practised in different parts of the country; it need 42 RUDIMENTS OF THE hardly be said that the illustrations might be greatly extended, as there are scarcely two counties in England in which the processes are exactly similar, but this would lead us far beyond the limits of a Rudimentary Treatise, and enough is given to show the student the interest of the subject, and to enable him to think and examine for himself. If he be induced to do this from the perusal of these pages, the aim of this little volume will have been completely fulfilled. II. TILES. 53. The manufacture of tiles is very similar to that of bricks, the principal differences arising from the thin- ness of the ware, which requires the clay to be purer and stronger, and renders it necessary to conduct the whole of the processes more carefully than in making bricks. 54. Tiles are of three classes, viz., paving tiles, roof- ing tiles, and drain tiles. Paving tiles may be considered simply as thin bricks, and require no especial notice. Roofing tiles are of two kinds : pantiles, which are of a curved shape, and plaintiles, which are flat, the latter being often made of ornamental shapes so as to form elegant patterns when laid on a roof. Pantiles are moulded flat, and afterwards bent into their required form on a mould. Plain tiles were formerly made with holes in them for the reception of the tile-pins, by which they were hung on the laths ; but the common method is now to turn down a couple of nibs at the head of the tile, which answer the same purpose. Besides pantiles and plaintiles, hip, ridge, and ART OF MAKING BRICKS AND TILES. 43 valley tiles, come under the denomination of roofing- tiles ; these are moulded flat, and afterwards bent on a mould, as in making pantiles. Draining tiles belong to the coarsest class of earthen- ware. They are of various shapes, and are made in various ways. Some are moulded flat, and afterwards bent round a wooden core to the proper shape. Others are made at once of a curved form, by forcing the clay through a mould by mechanical means. Tile-making machines are now almost universally superseding manual labour in this manufacture, and many machines of various degrees of merit have been patented during the last few years. 55. Besides the above articles, the business of a tilery includes the manufacture of tiles for malting floors, chimney-pots, tubular drains, and other articles of pottery requiring the lathe for their formation. We do not, however, propose now to enter upon the potter's art, which, indeed, would require an entire volume, but shall confine ourselves to the description of the manu- facture of roofing tiles as made in Staffordshire, and at the London tileries, adding a few words on the making of tesserae and ornamental tiles as practised by Messrs. Minton, of Stoke-upon-Trent. 56. In the country it is common to burn bricks* and tiles together, and as, in most places, the demand for bricks is not great, except in the immediate vicinity of large towns, where the demand is more constant, the manufacturer generally only makes so many bricks as are required to fill up the kiln. Where there is a great and constant demand for bricks and tiles, their manufacture is carried on sepa- * In some places bricks and lime are burnt together. 41 RUDIMENTS OF THE rately, and tiles are burnt in a large conical building, called a dome, which encloses a kiln with arched fur- naces. There are many of these in the neighbourhood of London, and, as we have described them very fully in the chapter on London Tileries, we need say nothing further here on this subject. 57. The manufacture of draining tiles is one which daily assumes greater importance 011 account of- the attention bestowed on agriculture, and the growing appreciation of the importance of thorough drainage. Any discussion on the best forms of draining tiles, oi the most advantageous methods of using them, would, however, be out of place in this volume. Neither need we say much on the practical details of the manufacture, as it is exceedingly simple, and as regards the prepara- tion of the clay, and the processes of drying and burning, is precisely similar to the other branches of tile-making. With regard to the process of moulding, there is little doubt but that hand moulding will soon be entirely superseded by machinery ; and the discussion of the merits of the numerous excellent tile-making machines now offered to the public, although of great interest to those engaged in the manufacture, would be unsuited to the pages of a rudimentary work, even were it practi- cable to give the engravings which would be necessary to enable the reader to understand their comparative advantages or defects.* A few words on the principal features of the manufacture of drain tiles are, however, required to enable the reader to appreciate its peculiar character. 58. Bricks, paving tiles, and roofing tiles, are little required, and seldom manufactured, except in the neigh- * A few details will be found in the chapter on Brickmaking by Machinery. ART OF MAKING BRICKS AND TILES. 45 bourhood of towns or of large villages, where the demand is likely to be sufficiently constant to warrant the erection of kilns, drying sheds, and other appurtenances of a well-mounted brickwork. If a cottage is to be rebuilt, a barn tiled, or it may be once in twenty or thirty years a new farm steading erected in a rural dis- trict, it is generally cheaper to incur the expense of carting a few thousand bricks or tiles than to erect the plant necessary for making these articles on the spot. But with drain tiles the case is reversed. They are most wanted precisely in situations where a brick-yard would be an unprofitable speculation, viz., in the open country, and often in places where the cost of carriage from the nearest brick-yard would virtually amount to a prohibition in their use, if they cannot be made or the spot, and that at a cheap rate. What is wanted, therefore, is a good and cheap method of making drain tiles without much plant, and without erecting an expen- sive kiln, as the works will not be required after sufficient tiles have been made to supply the immediate neighbour- hood, and therefore it would not be worth while to incur the expense of permanent erections. The making drain tiles a home manufacture is, therefore, a subject which has much engaged the attention of agriculturists during the last few years, and it gives us great pleasure to be enabled to give engravings of a very simple and effective tile-kiln erected by Mr. Law Hodges, in his brick-yard, and described in the Journal of the Royal Agricultural Society, vol. v., part 2, from which publi- cation we have extracted so much as relates to the description of this kiln, and the cost of making drain tiles in the manner recommended by him. [See Ap- pendix.] 59. We have already extended this sketch of the 46 RUDIMENTS OF THE general principles and practice of brick and tile making beyond its proper limits, and must therefore pass on to the practical illustrations of our subject. The chapter " On the Manufacture of Bricks and Tiles in Holland" is reprinted from the third volume of Weale's " Quarterly Papers on Engineering/' and will be read with interest on account of the great similarity of the English and Dutch processes. The account of brickmaking, as practised at Not- tingham and the Midland counties, was written from personal examination of brickworks in the vicinity of Nottingham, and in the counties of Derby, Leicester, and Lincoln, and has been carefully revised by a gen- tleman long connected with one of the principal brick- works near Nottingham. The paper " On Brickmaking, as practised in the Staffordshire Potteries/' was contributed to this volume by Mr. B. Prosser, of Birmingham, whose name is a sufficient guarantee for the value of the information therein contained. The details for this paper were col- lected by Mr. Prosser's assistant, Mr. John Turley, of Stoke ; and the valuable analyses of brick-earths were made for Mr. Prosser by Mr. F. C. Wrightson, of Birmingham, at a considerable expense. The description of brickmaking in the vicinity of London has been drawn up with great care, and is the first illustrated account that has yet appeared of the manufacture of clamp bricks. The drawings accom- panying this paper, and that on the London Tileries, are from the pencil of Mr. B. P. Stockman. Professional engagements preventing a personal exa- mination of the processes employed in brick and tile- making in the vicinity of the metropolis, Mr. Stockman kindly undertook this task, and to his persevering ART OP MAKING BRICKS AND TILES. 47 energy and talent we are indebted for a great mass of practical details embodied in these two chapters. Lastly, in the Appendix are inserted various par- ticulars relative to brickmaking which could not have been introduced in any other part of the volume with- out interrupting the continuity of the text. It should be noted that the various prices and esti- mates given in the following pages, refer to the time at which the descriptions were given. They are, of course, subject to later modifications. CHAPTER II. ON THE MANUFACTURE OF BRICKS AND TILES IN HOLLAND. BY HYDE CLARKE, C.E. I. BRICKS. THE Dutch make a most extensive use of bricks, of which they have several kinds. Not only are bricks used for ordinary building purposes, and for furnaces, but also in great quantities for foot pavements, towing- paths, streets, and high roads. It may be observed, that they have of late been used very effectively in this country for the pavement of railway stations. The paving bricks, or Dutch clinkers, are the hardest sort, and are principally manufactured at Moor, a smal vil- lage about two miles from Gouda, in South Holland. The brick-fields are on the banks of the river Yssel, from which the chief material is derived, being no other than the slime deposited by the river on its shores, and at the bottom. The slime of the Haarlem Meer is also extensively used for this purpose, as most travellers know. This is collected in boats, by men, with long 48 RUDIMENTS OF THE poles having a cutting circle of iron at the end, and a bag-net, with which they lug up the slime. The sand is also obtained by boatmen from the banks of the river Maes. It is of a fine texture, and grayish colour. The hard bricks are made with a mixture of this slime and sand, but in what proportions I am not informed. River sand is recognised as one of the best materials for bricks, and is used by the London brickmakers, who obtain it from the bottom of the Thames, near Wool- wich, where it is raised into boats used for the purpose. For what are called in France, Flemish bricks, and which are manufactured in France, Flanders, and on the corresponding Belgian frontier, river sand is pre- ferred, and is obliged to be obtained from the Scheldt. At Ghent, and lower down, a considerable traffic is carried on in the supply of this material. The quantity used there is about one cubic foot of sand per cubic yard. The slime and sand, being mixed, are well kneaded together with the feet, and particular attention is paid to this part of the process. The mixture is then depo- sited in heaps. The mode of moulding and drying is similar to that used elsewhere. Paving bricks are generally about 6 in. long, 4 in. broad, and If in. thick. Dutch clinks made in England are 6 in. long, 3 in. broad, and 1 in. thick. The house bricks and the tiles are made for the most part at Utrecht, in the province of the same name, from brick earth found in the neighbourhood. House bricks are about 9J in. long, 4J in. wide, and nearly 2 in. thick. II. BRICK-KILNS. The kilns are built of different sizes, but generally on the same plan. Sometimes they will take as many ART OF MAKING BRICKS AND TILES. 49 as 1,200,000 bricks. A kiln for burning 400,000 bricks at once is represented in the " Memoirs of the Academy of Sciences of France." It is a square of about 33 ft. or 35 ft. long by 28 ft. or 30 ft. wide, closed in with four walls of brick, 6 ft. thick at the base, and which slope upwards outside to their extreme height, which is about 18 ft. Some slope also slightly inwards, but in a dif- ferent direction. Different plans are nevertheless adopted with regard to the form of the external walls, the great object being, however, to concentrate the heat as much as possible. In the walls, holes are left for six flue-holes, and sometimes for eight or ten or twelve. In ODC of the walls, in the breadth of the kiln, an arched doorway is made, about 6 ft. wide and 12 ft. high, by which the bricks are brought into the kiln. The arrangements as to the doorway are also subject to variation. The interior of the kiln is paved with the bricks, so as to present a level base. The walls are laid with mortar of the same earth from which the bricks are made, and with which they are also plastered in- side ; yet, notwithstanding the strength with which they are built, the great power of the kiln fire sometimes cracks them. The kilns, I would observe, are not usually covered in, but some of those for baking building-bricks have roofs made of planks, and without tiles, to sheker them from the wind and rain. Others are provided with rush mats, which are changed according to the side on which the wind blows. The matting also serves for protecting the bricks against the rain, whilst the kiln is being built up. A shed, or hangar, is put up on each side of the kiln, in order to contain the peat turf, or to shelter the fire-tender, and to preserve the fires against the effects of wind. Such being the practice with regard to roofing, when the bricks are put into the 50 RUDIMENTS OF THE kiln, a layer, or sometimes two layers, of burnt bricks is placed on the floor, laid lengthwise, about three- quarters of an inch from each other, and so as to slope a little from the parallel of the walls, that they may the better support the upper rows, which are always laid parallel to the walls. This layer is covered with old rush mats, on which are arranged the dried bricks, which are laid without intervals between them. It is said that the mats serve to prevent the humidity of the soil from penetrating to the bricks while the kiln is being filled, which generally takes from about three weeks to a month. This row of burnt bricks is so placed as to leave channels or flues of communication with corresponding openings in the kiln walls. Six layers of dried bricks having been put down, the next three rows are made to jut over, so as to shut up the channels or flues. The layers are thus carried up to about forty-five in number, the last two being of burnt bricks, though in some kilns four layers of burnt bricks are used for closing in. The crevices are secured with brick earth or clay, on which sand is put ; the door of the kiln is then closed with one or two thicknesses of burnt brick, then an interval of about 10 in. or 12 in. filled in with sand, and this secured with walling, and by a wooden strut. The object of the sand is to prevent any of the heat from escaping through the crevices. It is to be remarked that, in laying the bricks in the kiln, as they are laid down, a cloth is put over them and under the feet of the workmen, so as to prevent any of the sand which might fall off, from getting down and blocking up the interval or interstice which natu- rally remains between each brick, and so interrupting the passage of the flame, and causing an unequal heat or combustion in the kiln. The kiln being filled, a sufficient quantity of peat turf ATVT OF MAKING BRICKS AND TILES. 51 is introduced into the flues, of which one end is closed up with burnt bricks, and the turf is set fire to. The turf used is from Friesland, which is reckoned better than Holland turf, being lighter, less compact, and less earthy, composed of thicker roots and plants, burning quicker and with plenty of flame, and leaving no ash. The general time in Holland during which the supply of turf by the flues is kept up, is for about four-and- twenty hours, taking care at first to obtain a gradual heat, and supplying fresh turf about every two hours. The fireman, by practice, throws the turfs in through the small fire openings, and as far in as he judges necessary. When one side has thus been heated, the flue openings are closed, and the other ends opened for four-and-twenty hours, and supplied with fuel; and this alternate process is kept up for about three or four weeks, the time necessary to burn large bricks. In some kilns, however, the fire is kept up for five or six weeks, depending upon their size and the state of the weather. A fortnight or three weeks is, however, sometimes enough for the clinkers. The burning having been concluded, about three weeks are allowed for cooling. It generally happens that the mass of brick sinks in in some places, arising partly from the diminution of volume produced by burning, and partly from the melting of some of the bricks which have been exposed to too great heat. The quality of the bricks depends upon the degree of burning to which they have been subjected. Those from about a third from the middle of the top of the kiln, or near the centre, are black, very sonorous, com- pact and well shaped, breaking with a vitrified fracture. These are generally employed for cellars, reservo/rs, and cisterns, and are most esteemed. D 2 52 RUDIMENTS OF THE III. TILES. The tiles manufactured in Holland are flat, hollow, S shaped, or with a square opening in the middle to let in a pane of glass, being much used for lighting lofts and garrets all over the Low Countries. They are either red, grey, or hlue, or glazed on one side only. The flat paving tiles are about 8J in. square by 1 in. thick; they are used principally for cisterns and for bakers' ovens. The clay for tiles, it is to be noted, is in all cases more carefully prepared than that for bricks, being ground up wet in a pugmill or tub, with a shaft carrying half a dozen blades. By this means, roots, grass, &c., are got rid of. The clay comes out of the pugmill of the consistence of potters' clay, and is kept under a shed, where it is kneaded by women, with their hands, to the rough form of a tile, on a table dusted with sand. These pieces are carried off to the moulders, who are two in number, a rough moulder and a finisher. The tiles are then dried under sheds, and afterwards in the sun. With regard to the flat paving tiles, they are at first rough-moulded about an inch larger than the subsequent size, and a little thicker, and then laid out to dry under a shed, until such time as the thumb can hardly make an impression on them. They are then taken to a finishing-moulder, who, on a table quite level and slightly dusted with sand, lays one of the tiles, and strikes it twice or thrice with a rammer of wood larger than the tile, so as to compress it. He then takes a mould of wood, strengthened with iron and with iron cutting edges, and puts it on the tile which he cuts to the size. The mould is of course wetted each time it is used. The tiles are then regularly dried. In Switzcr- and and Alsace an iron mould is used. ART OF MAKING BRICKS AND TILES. 53 IV. TILE-KILNS. The tile-kiln is generally within a building, and about 16 ft. long (in ordinary dimension), 10 ft. wide, and 10 ft. high. The walls are from 4J ft. to 5 ft. thick, secured outside with great beams, and so secured to- gether as to form a square frame. Some of the largest of them are pierced with four flue-holes, as in brick- kilns ; but the flues are formed by a series of brick arches, about 2i ft. wide by 16 in. high. The opening of the flue-hole is about 10 in. by 8 or 9 in. high. On their upper surface, these series of arches form a kind of grating, on which the tiles are laid. The kiln is covered in at top with a brick arch, pierced with holes of different sizes. The kilns are charged from an open- ing which is constructed in one of the side walls, which opening is, of course, during the burning, blocked up and well secured. The fuel used is turf, as in the brick- kilns, and the fire is kept up for forty hours together, which is considered enough for the burning. Three days are then allowed for cooling, and they are after- wards taken out of the kiln. Those tiles which are to be made of a greyish colour are thus treated. It having been ascertained that the tiles are burnt enough, and while still red hot, a quantity of small fagots of green alder with the leaves on is introduced into each flue. The flue-holes are then well secured, and the holes in the roof each stopped with a paving tile, and the whole surface is covered with 4 in. or 5 in. of sand, on which a quantity of water is thrown, to prevent the smoke from escaping anywhere. It is this smoke which gives the grey colour to the tiles, both internally and externally. The kiln is then left closed for a week, when the sand is taken off the top, the door and roof-holes 54 RUDIMENTS OF THE are opened, as also the flue-holes, and the charcoal produced by the fagots taken out. Forty- eight hours after, the kiln is cool enough to allow of the tiles being taken out, and the kiln charged again. Whenever any of the tiles are to be glazed, they are varnished after they are baked ; the glaze being put on, the tiles are put in a potter's oven till the composition begins to run. The glaze is generally made from what are called lead ashes, being lead melted and stirred with a ladle till it is reduced to ashes or dross, which is then sifted, and the refuse ground on a stone and resifted. This is mixed with pounded calcined flints. A glaze of manganese is also sometimes employed, which gives a smoke-brown colour. Iron filings produce black ; copper slag, green ; smalt, blue. The tile being wetted, the composition is laid on from a sieve. The manufacture of tiles, as already observed, is principally carried on near Utrecht, in the province of Holland, which, like most of the great cities of Hol- land, has facilities for the transportation of its produce by water communication all over the country. Gouda is a great seat of the pottery and tobacco- pipe manufactures, of which formerly Holland had a virtual monopoly, with regard to foreign trade, exporting largely Delft ware, Dutch porcelain, tobacco-pipes, bricks, Flanders' bricks, painted tiles, and paving tiles. The manufacture of painted tiles, for the decoration of the old fireplaces, was very extensive; and an infinite variety of designs, principally on Scripture subjects, employed many humble artists. This, however, is almost of the past. The manufacture of tobacco-pipes was another great business, suitable to the consumption of tobacco by the Netherlander. Gouda alone had, at one time,, as many as 300 establishments for the pro- ART OF MAKING BRICKS AND TILES. 55 duction of this article of trade. The manufacture of tobacco-pipes is still a large manufacture in England, much more considerable than is generally supposed ; while manufactures of bricks and porcelain constitute a staple means of employment for many thousands of our population A great part of these descriptions, it will be seen, strictly apply to our own practice, and are trite enough and trivial enough ; but in matters of this kind, there is nothing lost by being too minute, and it is always- safe. In the present case, it is worth knowing these things, for the sake of knowing that there is no difference. CHAPTER III BRICKMAKING AS PRACTISED AT NOTTINGHAM. 1. The mode of making bricks at Nottingham and the neighbourhood presents several peculiarities, of which the principal are : 1st. The use of rollers for crushing the brick-earth. 2nd. The use of copper moulds. 3rd. The hacking of the bricks under cover. 2. The use of copper moulds is not confined to the immediate neighbourhood of Nottingham, but has been for some years gradually extending to other districts, and will probably, sooner or later, become general throughout the country for the manufacture of superior qualities of bricks. 3. It may be proper here to say a few words on the object of grinding the clay, so generally practised throughout Staffordshire, Derbyshire, Nottinghamshire, and Lincolnshire, and probably in many other places. 56 RUDIMENTS OF THE 111 many brickworks the earth used is not pure clay, but a very hard marl, which cannot be brought into a state of plasticity by the ordinary processes of weather- ing and tempering without bestowing upon it more time and labour than would be repaid by the value of the manufactured article. The expedient of grinding is, therefore, resorted to, which reduces the earth to any state of fineness required, according to the number of sets of rollers used, and the gauge to which they are worked, all hard lumps and pieces of limestone,* which would otherwise have to be picked out by hand, being crushed to powder, so as to be comparatively harmless. 4. The advantages and disadvantages of the use of rollers may be thus briefly stated, 1st. A great deal of valuable material is used which could not be made available for brickmaking by the ordinary processes. 2nd. The process of grinding, if properly con- ducted, greatly assists the operations of the temperer by bringing the earth into a fine state, quite free from hard lumps. On the other hand : The facilities afforded by the use of rollers for working up everything that is not too hard to be crushed by them, induce many brickmakers to make bricks without proper regard to the nature of the material. A common practice is to work the rollers to a wide gauge, so that comparatively large pieces of limestone are suffered to pass through without being crushed by them. Where this has been the case, it need hardly be said that the bricks are worthless. They may appear sound, and * It may be necessary to explain, that all pebbles and hard stones must be picked out by hand before grinding ; where the brick earth used is much mixed with gravel, the only resource is the use of the wash mill. ART OF MAKING BRICKS AND TILES. 57 may have a tolerable face, but rain and frost soon destroy them, and, in situations where they are exposed to the weather, they will become completely perished in a very few years. 5. The following description of the mode of making bricks at Nottingham will apply pretty faithfully to the practice of the brick-yards for many miles round. It will, of course, be understood that in no two yards is the manufacture carried on in exactly the same way ; there being differences in the designs of the kilns, the arrangement of the buildings, and other points of detail, which may be regulated by local circumstances, or which, from the absence of any guiding principle, may be left to chance ; the general features, however, are the same in all cases. 6. Brick-earth. The brickmakers of Nottingham and its immediate vicinity derive their supplies of brick- earth from the strata of red marl overlying the red sandstone on which the town is built, and which in its turn rests on the coal-measures, which make their appearance at a short distance to the west of the town. The banks of the river Trent present many good sections of these strata, as at the junction of the rivers Trent and Soar ; where they are pierced by the Red Hill tunnel, on the line of the Midland Railway ; and at Radcliff-on-Trent, where they form picturesque cliffs of a red colour covered with hanging wood ; and they are exposed to view in many places in the immediate vicinity of Nottingham, as in the cutting for the old road over Ruddington Hill, in the Colwick cutting of the Nottingham and Lincoln Railway, and Goose Wong Road, leading to Mapperly Plains. The marl abounds with loose and thin layers of skerry, or impure limestone, and in many places contains veins D 3 58 RUDIMENTS OF THE of gypsum, or, as it is called, plaster stone, which are extensively worked near Newark, and other places, for the manufacture of plaster of Paris. The water from the wells dug in these strata is strongly impregnated with lime. 7. The colour of the bricks made at Nottingham and in the neighbourhood is very various. For making red bricks the clay is selected with care, and particular beds only are used. For common bricks the earth is taken as it comes, and the col our is very irregular and unsatis- factory, varying from a dull red to a dirty straw colour. Some of the marl burns of a creamy white tint, and has been lately used with much success in making ornamental copings and other white ware. 8. In the manufacture of common bricks no care is taken in the selection of the clay, and it is worked up as it comes to hand indiscriminately, the great object >f the manufacturer being to clear his yard ; the same price being paid for all clay used, whatever its quality. Stones and pebbles are picked out by hand, but the pieces of limestone are generally left to be crushed by the rollers, and much bad material is worked up in this way which could not be made use of if the tempering were effected by treading and spade labour only. There are, however, many beds which are sufficiently free from limestone not to require grinding, and when these are worked the rollers are not used. 9. For front bricks, and the superior qualities, the clay is selected with more or less care, receives more preparation previous to grinding, is ground finer, and is sometimes left to mellow in cellars for a considerable time before using. 10. For making rubbers for gauged arches, the clay is carefully picked, and run through a wash-mill into ART OF MAKING BRICKS AND TILES. 59 pits, where it remains until by evaporation and settle- ment it has attained a proper degree of consistency. The clay for this purpose is generally mixed with a cer- tain quantity of sand to diminish the labour of rubbing the bricks to gauge, the proportion varying according to the quality of the clay. The sand used for this purpose is the common rock sand, which burns of a red colour. 11. The clay immediately near the town of Notting- ham is not well suited for making roofing tiles, the ware produced from it being generally very porous. This statement, however, is not to be taken without exceptions, as there is plenty of suitable clay for the purpose within a few miles' distance. 12. The old houses in Nottingham are built with very thin bricks, much of the old brickwork gauging 10^ in. to 4 courses in height, including mortar joints. These bricks are of a dark red colour, and were from works that have been long since abandoned. The bricks now made are much thicker, the walls of many new build- ings gauging 21 in. to 7 courses in height, or about 13 J in. to 4 courses in height, including mortar joints. The common bricks are of a very uneven colour, which arises partly from the manner in which they are set in the kiln, and partly from the want of care in selecting the clay, and the quantity of limestone ground up with it. From this circumstance the fronts of many of the new buildings have a mottled appearance, which ia extremely unsightly. GENERAL ARRANGEMENT OF A BRICKWORK. 13. The brick-yards from which the town of Not- tingham is at present supplied are situated on the slopes of a small valley along which runs the public 60 RUDIMENTS OF THE road from Nottingham to Southwell,, and, being situ- ated on the sides of the hills, great facilities exist for draining the workings and for bringing the ground into cultivation again after the clay has been exhausted. 14. The proprietor of a brickwork usually rents the required land from the owner of the soil, at a price per acre, and in addition to the rent pays for all clay dug, whatever its quality, at a set price per thousand bricks made and sold, exclusive of those used for the erection and repairs of the buildings and works. AKT OF MAKING BRICKS AND TILES. 61 15. The arrangement of the several buildings varies with each yard more or less; but the principle on which they are laid out is the same in all cases, viz., to advance towards the kiln at each process, so as to avoid all unnecessary labour. This will be understood by inspection of fig. 1, which, it must be understood, is not an exact representation of a particular brickwork, but a diagram to explain the principle of arrangement usually followed. The pits from which the clay is dug are at the rear of the works, and at some little distance from them is placed the clay-mill, which, to save labour in wheeling the clay, is shifted from time to time as the workings recede from the kiln by the exhaustion of the clay. This is, however, not always done, as, where the mill has been fixed in a substantial manner, the saving in labour would not repay the cost of re-erection. The hovel or drying shed generally forms two sides of a rectangular yard adjoining the public road, the kiln being placed as close to the hovel as practicable, and the working floors or flats in the rear of the latter. By this concentration of plan, the distance to which the bricks have to be carried between the successive processes of moulding, drying, hacking and burning is reduced to a minimum, which is an important point to be attended to, as the raw bricks are shifted by hand and not harrowed. As it is not always possible to obtain a supply of water at those parts of the works where it is wanted to be used, a water-cart* is kept at some yards for this purpose, the supply being taken from a pond into which the drainage of the works is conducted. * The water-cart is seldom used, except where the water has to be fetched a considerable distance indeed rarely, but in times of drought. It is usually carried, in the yard, in buckets with yokes, as in the time of Pharaoh. 62 RUDIMENTS OP THE The goods for sale are stacked in the open part of the yard as near the public road as practicable. 16. Clay-Mill. The machinery used in grinding the clay is very simple. The clay-mill consists of one or more pairs of cast-iron rollers, set very close together in a horizontal position, and driven by a horse who walks in a circular track, and, by means of the beam to which he is attached, puts in motion a horizontal bevelled driving-wheel placed at the centre of the horse track. A horizontal shaft connected at one end with one of the rollers by a universal joint, and having a bevelled pinion at the other end, communicates the motion of the driving-wheel to the rollers by spur-wheels keyed on their axles. The clay is tipped in a wooden hopper placed over the rollers, and passing slowly between the latter falls on a floor about 8 feet below them, where it is tempered for the moulder. 17. The common clay-mill has only one set of rollers, but the addition of a second set is a great improvement. In this case the bottom rollers are placed almost in contact with each other, and should be faced in the lathe to make them perfectly true. If only one set be used this is a useless expense, as the gauge to which they are worked is too wide for any advantage to be derived from it. 18. Figures 2, 3, 4 represent a one-horse mill with a single pair of rollers 18 in. in diameter, and 30 in. long, manufactured by Messrs. Clayton and Shuttle- worth, of Lincoln, who kindly furnished the drawings from which the engravings have been made. The detailed description of the several parts will be found in art. 69. ART OF MAKING BRICKS AND TILES. 63 Fig. 2 64 RUDIMENTS OF THE Fig. 3. ART OF MAKING BRICKS AND TILES. 65 This is a very good mill, of simple construction, and not expensive, the cost when ready for fixing (exclusive of foundations and brickwork) being 35. It cannot be too strongly insisted upon that the machinery should be boxed up close, so as to prevent stones or clay from clogging the wheels, as where this 66 RUDIMENTS OF THE is not done the machinery will unavoidably become deranged in a very short time. 19. In many yards, the horse-track is raised to the level of the top of the hopper, so that none of the machinery is exposed. A very good arrangement of this kind is shown in fig. 5, of which a detailed descrip- tion is given in art. 69. 20. The quantity of work performed will of course vary greatly, according to the distance between the rollers and the consequent fineness to which the clay is ground. One mill will grind sufficient clay to keep six moulders fully employed, and therefore there are very few yards in which the rollers are constantly in work. 21. The length of time during which a clay-mill will last in good working condition is chiefly regulated by the wear of the rollers. If the iron is of very uniform quality, and care be taken to pick out all the pebbles from the clay, a pair of rollers will last many years. The other parts of the machinery will last with care for an indefinite length of time. 22. Wash-mill. The wash-mill is used only in the manufacture of arch bricks, and does not differ from that used in other places. The only one visited by the author consists of a circular trough, lined with brick- work, in which the clay is cut and stirred up with upright knives fastened to a horse-beam. From this trough, the slip runs through a grating into a brick tank, where it remains until by evaporation and settle- ment it becomes sufficiently consolidated for use. 23. The Pug-mill is not used in the Nottingham* brick-yards ; the tempering of the clay, after grinding, being effected by treading and spade labour. Instead of the clay being tempered directly after grinding, it is * It is, however, used in the neighbourhood. ART OF MAKING BRICKS AND TILES, 67 r 68 RUDIMENTS OF THE sometimes deposited to ripen in damp cellars for a year or more. This is done for the best bricks only. 24. The Moulding Sand used is the common rock sand, which burns of a red colour. In making white bricks this is a great disadvantage, as it causes red streaks, which greatly injure their colour. The sand is only used to sprinkle upon the table to prevent the clay from adhering thereto, and therefore sand with a sharp grit is preferred. 25. The Moulding Table is shown in fig. 6. It is Fig. 6. ART OF MAKING BRICKS AND TILES. 69 furnished with a sand-box, which is sometimes fixed to the table, as shown in the cut, and sometimes detached, and with a water-box, in which the moulder dips his hands every time he moulds a brick. In the operation of moulding, the moulder stands in front of the table, with the water-box immediately in front of him, the tempered clay at his right hand, and the sand-box at his left. A sloping plank is placed at one end of the table to enable the boy who brings the clay from the temperer to deposit it more conveniently on the table. The boy who takes off the newly-made bricks, and brings back the empty mould, stands on the side of the table opposite the moulder, to the right of the water- box, in which he washes his hands after each journey, to prevent the clay from drying on them. The cost of a moulding table varies according to the care with which it is made. Such a one as shown in the cut will cost about 20s., and will last, with occasional repairs, for several years. The part where the brick is moulded soon becomes worn, and has to be cased as shown in the cut. This casing extends over the part where the brick is taken off by the carrier boy ; but, as the wear is not uniform over this space, the casing is in two or more pieces, the part where the brick is moulded wearing much faster than the others, and requiring renewal sooner. It is of importance that the drippings from the table should not fall on the drying floor, as they would render it slippery and unfit for use ; a rim is therefore placed at one end, and along a part of one side of the table, and the opposite side is furnished with a kind of apron and gutter, by means of which the slush is conducted to a tub placed under one corner of the table, but which is not shown in the cut. 70 RUDIMENTS OF THE 26. Brick Moulds. Until lately the moulds used were made of wood, but these have been almost entirely superseded by brass, or, as they are technically called, copper, moulds. There are several different ways in which these moulds are made. Some- times the brass work is merely an inside lining, screwed to a wooden mould; but the best construction appears to be that shown in fig. 7, in which the mould is of brass, cast in four pieces, and riveted together at the angles, the wood- work being in four distinct pieces and attached to the brass mould by the angle rivets. These moulds are costly, and formerly a pair of moulds cost 2 } but they may now be had for 1 bs. the pair. It will be seen, by reference to the engraving, that the brass overlaps the woodwork all round the mould on each side, and these portions of the mould wear away very rapidly, so that the bricks made at the close of the season are considerably thinner than those made at its commencement. This renders it necessary to renew the projecting rims from time to time as they become worn down with use, and this will require to be done every season if the mould has been in constant use. It is an expensive operation, as the new rim has to be brazed on to the old part, and this must be done with great nicety, and so as to make a perfectly flush joint on the inside of the mould, or the latter would be rendered useless. The cost of plating a pair of moulds is nearly the same ART OF MAKING BRICKS AND TILES. 71 as their original cost, 20s. being charged for the opera- tion, and therefore it would be preferable to use the moulds until they are quite worn out, and then to replace them with new ones. 27. The use of copper moulds is confined to the making of building bricks, and quarries for paving floors, their weight and great cost preventing their employment for larger articles. 28. The mould has no bottom as in the London practice, nor is it placed upon a raised moulding board as in Staffordshire ; but rests on the moulding table itself, the top and bottom beds of the brick being formed at two distinct operations with a little instrument called a plane. 29. The Plane, fig. 8, is usually made 9 in. long by 3 in. broad, with a handle at one end. Its use is to compress the clay in the mould, and to work over the top and bottom beds of the brick to give them an even surface. The strike is not used at Nottingham. 30. The Flats, or working floors, are prepared with care, by levelling and rolling, so as to make them hard and even, and are laid out with a slight fall, so that no water may lodge on them. They are well sanded, and constant care is requisite to keep them free from weeds. Their usual width is about 10 yards. In unfavourable weather a single moulder will sometimes have as many as 7,000 bricks on the flats at once, for which an area of from 300 to 400 superficial yards will be required. This, however, is an extreme case, and in good drying weather a moulder does not require more than half that extent of floor, or even less than this. 72 RUDIMENTS OF THE 31. The Hovel, or drying shed, in which the bricks are hacked, is generally built in the roughest and cheapest manner possible, with open sides and a tiled roof, supported by wooden posts or brick piers; the width of the hovel is about 18 ft., or rather more than the length of a hack, but the eaves are made to project a couple of feet or so beyond this distance, in order to give additional shelter from the rain, for which reason, as well as for the sake of economy, the eaves are carried down so low as to make it necessary to stoop to enter the shed. Some of the hovels have flues under the floor, the fire-places being placed in a pit sunk at one end of the hovel, and the chimney at the opposite end. These flues are made use of when the demand for bricks is so great that sufficient time cannot be allowed for dry- ing in the open air, and also during inclement seasons. The sides of the hovel are then walled up with loose brickwork to retain the heat. No specific rule can be given for the relative sizes of the hovel and the drying floor. The common practice appears to be to make them of the same length, which allows ample room, and enables the moulder to keep a portion of his shed always available as a drying floor when the weather is too wet to allow of the bricks being laid out on the flats. When this is the case the moulder protects the raw bricks from drafts, by surrounding them with a skirting, so to speak, of planks. This is a very neces- sary precaution, for the currents of air from different parts of the shed would cause the bricks to dry un- equally, and they would crack and become unsound. Matting is frequently hung up at the sides of the hovel for this purpose, and is also much used in some yards to prevent the finer clays, when tempered, from drying ART OF MAKING BRICKS AND TILES. 73 Fig. 9. too rapidly where cellars are not provided for that purpose. 32. The above description applies to the ordinary hovel, but the best front bricks are dried wholly under cover in a brick hovel inclosed by walls on all sides, and furnished with flues, by which the place is kept at a regular temperature. The expense, however, of conducting the whole of the drying under cover in this manner is too great to allow of its general adop- tion. 33. The clapper, fig. 9, is simply a piece of board 12 in. by 6 in. with a handle on one side. It is used to flatten the sur- faces of the bricks as they lie on the floors, and the bricks are also beaten with it during the process of hacking, to correct any warping which may have taken place in the fist stage of drying. 34. Dressing Bench. Fig. 10. This is simply a stout bench, to which is fitted a plate of cast-iron, on which the best front bricks are rubbed or po- lished, to make them per- fectly true and even; the workman, at the same time, beating them with a wedge-shaped beater, tipped with iron, called a dresser, fig. 11. This operation toughens the brick, corrects any warping which may have taken place, and leaves the arrises very sharp. E Fig. 10. 74 RUDIMENTS OF THE Fi ff- 11- 35. Machinery for pressing Bricks. In some yards screw presses are used for pressing front bricks, and with considerable success. It is, however, questionable whether they are as durable as those dressed by hand. In making machinery for this purpose the great desiderata are, 1st, to make the metal mould in which the brick is compressed so strong that it shall not spring on the application of the power; and, 2nd, that the piston shall exactly fit the mould : when, from bad workmanship or long use, this is not the case, the clay is forced between the piston and the mould for a short distance, leaving a slightly-raised edge all round the side of the brick. 30. We do not propose here to enter upon a com- parison of the respective merits of machine-pressed bricks and those dressed by hand. The operation of dressing on the bench requires an experienced work- man, whilst a common labourer can use a machine. For this reason machine-pressed bricks can be pro- duced much cheaper than those dressed by hand, and there is little inducement to employ the latter process. 37. Kiln. The kilns vary considerably as regards their Dimensions and constructive details, but they are all built on the same principle. The kiln shown in figs. 12, 13, 14, 15, 16, and 17, is a good one, though rather weak at the angles, and will convey an idea of the general construction. (See chap, ix., page 210.) ART OF MAKING BRICKS AND TILES. 75 Fig. 12. It consists of four upright walls, inclosing a rectangu- lar chamber. The floor is sunk about 4 ft. below the general surface of the ground, and is not paved. The doorways for setting and drawing the kiln are merely narrow openings at the ends of the kiln, raised a step above the ground, and about 5 ft. from the floor. The fire-holes are arched openings opposite each other on the sides of the kiln, lined with fire bricks, which require to be renewed from time to time, generally every season. The width of these holes is reduced to the required space 76 RUDIMENTS OF THE by temporary piers of brickwork,, so as to leave a narrow opening about 8 in. wide and about 3 ft. high. This will be understood by reference to fig. 12, in which Fig. 13. ___SO__ i _Q_ '_ Fig. 14. ART OF MAKING BRICKS AND TILES. Fig. 15. 77 Fig. 16. . 17. the dark shading shows the fire-brick lining, and the unshaded parts the temporary piers. On each side of the kiln a pit is sunk to the level of the floor, and covered with a lean-to roof, which protects the fuel and the fire-man from the weather, and prevents the wind from setting against the fires. The walls of the kiln are about 3 ft. thick, and are built of old bricks, rubble stone, and the refuse of the yard. No mortar is used, as the use of lime would destroy the brickwork, 78 RUDIMENTS OF THE under the intense heat to which the walls are exposed. The bricks are therefore set in loam or fire-clay, if it can be readily procured. The fire-bricks for lining the fire-holes are sometimes brought from Ilkeston, where excellent fire-clay is worked, but it is most common to make them at the yards with such clay as can be got in the neighbourhood, which answers pretty well. This clay is brought from the neighbouring collieries, and is obtained when sinking shafts ; there is no fire-clay at any of the Nottingham yards. 38. Instead of being built with walls of parallel thickness, resting on arches, as in the example just described, some kilns are built with walls of great thickness at bottom, and diminishing by set-offs until, near the top of the kiln, they are comparatively thin. Many kilns also are provided with massive buttresses at the angles, with the intention of counteracting the tendency which the walls have to lift themselves with the heat. Very great care is requisite in drying a newly-built kiln, or the walls will be cracked at the first firing, and the thicker the walls the greater the care necessary. 39. So long as the brickwork is sufficiently thick to retain the heat, no purpose is attained by increasing the strength of the walls, unless they are made so massive that they are unaffected by the heat externally, and heavy enough to counteract the lifting cause by the expansion of the sides exposed to the fire. In the one case the walls expand bodily with the heat, forming large and dangerous cracks ; in the other, separation takes place between the inside and outside of the walls, from the expansion of the parts most exposed to the heat, and the kiln soon requires relining. 40. The kiln shown in figs. 12 to 17 is an example ART OF MAKING BRICKS AND TILES. 79 Fig. 18. of the mode of building with walls of the same thick- ness top and bottom ; that shown in fig. 18 is one of a more massive construction, and has buttresses at the angles. The upper part of this kiln is formed by build- ing,, in a temporary manner, a thin parapet round the inside of the top of the walls, about a couple of feet in height. This expedient is often resorted to for the sake of increasing the capacity of a kiln at a small expense. 41. Some of the kilns are provided with a flight of steps by which access is obtained to the top, in others ladders are used for this purpose. Many of the kilns have also a kind of light fence round the top, made of rough poles. This serves as a protection from falling, and as a scaffold to which screens may be hung in windy weather to keep the wind from setting on the top of the kiln. This fence is shown in fig. 2. The outside staircase is shown in figs. 1, 13, and 1(5. 42. The sizes of the kilns vary considerably. A kiln such as that shown in figs. 12 to 17, 20 ft. long, 10 wide, and 12 ft. high, will, with the addition of a parapet, burn 25,000 bricks at once, and will require rather more than that number of bricks for its erection. The cost of such a kiln would be from 30 to 50, the value of the materials being almost nominal. The capacity of a kiln may be roughly calculated on the assumption that ten bricks require a cubic foot of space in the kiln, but much, of course, will depend on 80 RUDIMENTS OF THE the nature of the clay and the amount of shrinkage before burning. 43. A well-built kiln will last for many years with occasional repairs. PROCESS OF BRICKMAKING. 44. Clay digging. The clay or marl is, or should be, dug in the autumn, and collected in large heaps at the bottom of the slopes, to be mellowed by the winter frosts. These heaps are shown in fig. 1. The cost of this operation varies from \s. to Is. 9d. per 1,000 bricks, according to the labour of getting the clay, and the distance to which it has to be wheeled. 45. Tempering. In the spring the clay is turned over by spade labour, being at the same time well watered and trodden. The pebbles and large lumps of lime- stone are picked out by hand with more or less care. The prepared clay is then wheeled to the mill, and tipped into the hopper. Sometimes the clay, after being ground, is at once tempered for use on the floor beneath the rollers ; but for the best bricks, as before stated, it is allowed to remain in cellars to ripen for a year or more. 46. The temperer is generally paid by the moulder, who contracts for tempering, moulding, and hacking at a price per 1,000. The cost of tempering for common bricks is about 1*. 3d., exclusive of the cost of horsing the mill, which is borne by the proprietor of the yard. One temperer will keep one moulding-table constantly supplied, and will also assist the moulder in getting up his bricks from the floor. 47. Moulding. A sufficient quantity of clay having been prepared on the tempering floor, one of the moulder's boys takes up as large a lump as he cau ART OF MAKING BRICKS AND TILES. 81 conveniently carry, and, placing it on his head, walks with it to the moulding table, and walking up the sloping plank, deposits it at the end of the table, to the right hand of the moulder at B, fig. 6. The moulder having sprinkled some dry sand over the part of the table marked D, takes from the heap of tempered clay a piece sufficient to make a brick, and kneads this clot with his hands on the sanded part of the table, so as to bring it approximately into shape. He then raises the clot in the air, and dashes it with some force into the mould, striking off the superfluous clay with his fingers. He then dips his hands into the water-box, and, with very wet hands, works over the face of the brick, so as to force the clay perfectly into the mould in every part. He next takes the plane and passes it backwards and forwards with considerable pressure, until the face of the brick is flush with the edges of the mould, and then, reversing the mould, planes the underside in the same way. The brick being moulded, the moulder slides it on the wet table to his left hand side, where it is taken off by a second boy, who carries it, mould and all, to an unoccupied part of the floor, where he turns it out carefully on one of its sides, and returns with the empty mould. Meanwhile the moulder has made another brick in a second mould, which is now ready to be taken off, and this process is repeated until the distance to an unoccupied part of the floor is too great to allow of the boys returning in time, and the table is then shifted to another part of the floor. 48. Drying. After the bricks have remained for a few hours in the position in which they were first placed on the floors, they are turned on their edges by a boy, who turns up two at once, one with each hand. They E3 82 RUDIMENTS OF THE remain in this position a few hours longer, and are then laid flat on the opposite side to that on which they were first placed. Careful moulders sprinkle sand over the wet bricks as they lie on the floor, which absorbs the superabundant moisture, and renders them less liable to crack ; but this is not always done. The new bricks sometimes also undergo a slight dressing with the clapper, to take off any roughness at the edges, and to correct any alteration of form which may have taken place on turning them out of the mould, and in some cases they are scraped with a small iron scraper, to remove any dirt that may adhere to them. After lying flat a few hours longer, they are carried by the boys, three at a time, to the hovel, where the moulder builds them into hacks 50 bricks long and 14 courses high, each hack containing 700 bricks. As the bricks are hacked they are batted with the clapper, to correct any warping which may have taken place whilst lying on the floors. The bricks remain in the hovel without being again shifted, until they are ready for burning. 49. The time allowed for drying varies with the weather, the size of the kiln, and the demand for bricks. Some brickmakers get the bricks out of the kiln within a fortnight of their leaving the moulds, but this haste is very prejudicial to the soundness of the bricks, and, as a general rule, three weeks is the least time that should be allowed for drying. The time that the raw bricks lie on the flats depends solely on the weather. In good drying weather the bricks are made one day and hacked the next ; but at other times several days may elapse before they are fit for hacking. 50. It is not very easy to separate the cost of hacking ART OF MAKING BRICKS AND TILES. 83 from that of moulding, as both operations are per- formed by the moulder. The price for moulding, in- cluding tempering and hacking, is from 5s. per 1,000, and upwards ; 5s. 3d. is a common price. Where the clay is ground the moulder pays for feeding the mill, but not for horsing it, this expense being borne by the proprietor of the yard. 51. The above description refers to the ordinary mode of proceeding, but for facing-bricks additional processes are employed. Pressed bricks, as their name implies, are prepared by putting the raw bricks one at a time, when nearly dry, into a metal mould, in which they are forcibly compressed by the action of a powerful lever which forces up the piston forming the bottom of the mould. This gives a very beautiful face to the brick, and leaves the arrises very sharp, but bricks so prepared require longer time for drying and judicious management in the kiln, otherwise they will be un- sound, and when exposed to the weather soon become perished. 52. Polished bricks, as they are called, are rubbed upon a bench plated with iron, to make their surfaces perfectly even, and are also dressed with a dresser, as before described. This process is only gone through with the very best bricks, and its cost is such that it is not employed to any very great extent. 53. The contraction of the clay in drying is very slight, and no perceptible diminution of size takes place in burning if the bricks have been previously thoroughly dried. The brick moulds are made of different sizes at dif- ferent yards, their proportions having been altered from time to time, so as to increase the depths of the moulds at the expense of the other dimensions. 84 RUDIMENTS OF THE When the thickness of a piece of brickwork is mea- sured by the number of bricks, as in house building, and not by feet and inches, as in building the piers of bridges and other solid works, the number of bricks required for the execution of a rod of brickwork is considerably reduced by a very trifling addition to the thickness of the bricks, and this is always an induce- ment to purchasers to prefer the yards where the deepest moulds are used. The largest common bricks now made measure, when burnt, 9J in. long, 4f in. wide, and 3^ in. thick, or thereabouts ; the size of the moulds being 9| in. long by 4i-J in. wide, and 3 in. deep. These bricks weigh about 7 Ibs. 15 oz. when burnt. The best red facing-bricks made at Mr. Wood's yard, in the Carlton Road, measure, when burnt, 9J in. long, 4 in. wide, and 2^f in. thick. The moulds for these bricks are 10 in. long, 4J in. wide, and 3J in. deep. 54. A good moulder, if solely occupied in moulding, will turn out 2,000 bricks in a day, bet ween 6 A.M. and 6 P.M. ; but as nearly one-third of the moulder's time is taken up with hacking, the average day's work is not more than about 1,300 per day, or between 7,000 and 8,000 weekly. 55. Burning. The setting of the kiln is an opera- tion on which much depends, and requires to be done by an experienced hand, as there is a great deal of art in arranging the bricks in a proper manner, so as to allow the heat to be diffused equally through the kiln, and to afford a proper draught, so as to obtain the greatest amount of steady heat with the smallest ex- penditure of fuel. The lower part of the kiln is filled with common bricks, narrow openings being left, as shown by the ART OF MAKING BRICKS AND TILES. 85 dotted lines in fig. 12, forming flues connecting the opposite fire-holes, the tops of these flues being formed by oversetting the bricks on each side till they meet. These flues are of the same height as the fire-holes. The best bricks* are placed in the middle of the kiln, and above these again are placed common bricks up to the top. The bricks are not placed close together, but a space is left all round each brick to allow of the pas- sage of the heat round it ; the bricks in the successive courses being crossed either slantwise, or at right angles to each other. When a brick rests partly .on others, and is partly exposed to the fire, the exposed part will commonly be found of a lighter red than those to which the fire has had no access, and this is one great cause of the mottled colour of the Nottingham bricks. When, therefore, it is wished to produce bricks of a uniform red tint, great care is taken to keep the faces and ends of the bricks in close contact, crossing them every few courses only. The kiln being topped, the doorways are built up with refuse brick and plastered over with clay, to prevent the admission of currents of cold air, and the fires being lighted, the heat is got up gradually, care being taken not to urge the fires, until all the steam is driven off from the bricks, and the actual burning begins. When the fire has attained its full heat, the fire-holes are partially stopped with clay, and the top of the kiln is covered over with earth, turfs, or boards, to check the draught, and a steady uniform heat is kept up until the completion of the burning, which generally occupies three days and three nights from the first lighting of * If tiles be burnt at the same time, which is frequently the case, as they cannot be burnt alone without great waste, they take the same position in the kiln as dressed bricks. 86 RUDIMENTS OF THE the fires ; at the expiration of which time the fire-holes are completely stopped, and the fires put out ; after the fires have been extinguished, the kiln should be allowed to cool very gradually, as the soundness of the bricks is much deteriorated by the kiln being opened too soon ; this, however, is a point not sufficiently attended to. 56. The fuel employed is coal,* the quantity f used being about half a ton per 1,000 bricks, the exact amount depending on the quality of the fuel and the judicious setting of the kiln. The town of Nottingham being situated on the very edge of the Nottinghamshire coal-field, the cost of firing is very low, and excellent coal can be laid down at the yards at from 8s. 6d. per ton upwards. The small coal or slack frequently used in the early stage of burning does not cost more than 5s. to 6s. per ton. 57. The colour and soundness of the bricks vary according to their position in the kiln and the intensity of the heat to which they have been exposed. Those nearest the fire become partially vitrified, and of a blackish tint. Those which have been more favourably placed burn of various tints according to the nature of the clay, from red to straw colour and white, and when struck together ring with a clear metallic sound. Those which are underburnt are tender, of a pale red colour, and give a dull sound when struck together. 58. The cost of setting and drawing the kiln is gene- rally reckoned at Is. 6d. per 1,000, this including stacking the bricks in the yard, or placing them in the carts of the purchasers. If, however, they are * Soft coal is preferred. f In some great yards a deal of coal is wasted on the top of the kiln. As the heat has always an upward tendency, this has very little effect on the bricks, and a great deal of fuel is wasted in vsmoke and flame. ART OF MAKING BRICKS AND TILES. 87 not for immediate sale, an additional Qd. is charged for loading the carts. 59. The labour in firing is reckoned at Is. per 1,000. 60. At "Nottingham, and at the yards in the neigh- bourhood, many varieties of brick are manufactured ; as cant, or splayed bricks, for plinths ; weathered and throated copings of several sizes ; round copings ; bricks with quarter-round ends ; wedge-shaped bricks for culverts ; compass, or curved bricks for lining shafts and wells, and also paving, roofing, and draining tiles of all descriptions. It is unnecessary to enter into any details on the manufacture of these articles, as they offer no particular points of interest. It may, however, be worth while to mention that the use of copper moulds is confined to the manufacture of those articles which are of a convenient size, and for which there is a large demand ; the moulds for cant bricks, compass bricks, and other fancy articles for which there is only a limited demand, being made of wood. COST OF MANUFACTURE. 61. Land, and Brick-earth. The proprietor of a brickwork usually rents the necessary land at a price per acre, and in addition pays for all clay removed at a set price, whatever its quality. As the brick-earth is exhausted, or the workings reach an inconvenient depth, the ground is levelled and again thrown into cultivation. This is of course done at the earliest period possible ; and in some cases the rental of the land is nearly made up by the profit de* rived from cultivating the site of the exhausted work ings, so that it is impossible to give an accurate estimate 88 RUDIMENTS OF THE of the proportion which the rental of the land bears to the total cost of manufacture, as it must vary widely in each particular case. This remark does not hold good with regard to the brick-earth, which is paid for at the rate of 8d. per cubic yard, or 2s. per 1,000 bricks, a thousand bricks requiring about 3 cubic yards of clay. It must be remembered that, as above stated, this price is paid for all clay removed, whether suitable or not for brickmaking. For common bricks the earth is taken as it comes, good and bad being ground up to- gether ; the cost of grinding being less than the loss which would result from the rejection of the inferior earths, which are often so hard, and contain so much skerry in pieces of all sizes from that of a walnut to that of a man's head, that they could not be worked up by the ordinary process of tempering by treading and spade labour only. For front bricks and the best qualities, the clay is carefully picked, and the cost is propor- tionately increased thereby. No estimate can be given for the amount of land required for making a given number of bricks, as it depends on the situation of the yard and the depth to which the workings can be carried. 62. Buildings and Machinery. From the circum- stance that in existing yards the buildings have been erected at different times without any very systematic plan, it is not very easy to ascertain what are the best relative sizes of working floors, hovels and kilns, or what extent of building and plant are required for working a yard to the greatest advantage. Unless the manufacture be conducted on a very large scale, the grinding-mill will, in most cases, be often unemployed ; and the wash-mill being used only in the manufacture of arch bricks, it is only in the immediate neighbour- ART OF MAKING BRICKS AND TILES. 89 hood of a large town that a return for the cost of its erection can be hoped for. It will always be found an advantage to have an excess of shed-room rather than the contrary. 03. The following rough estimate will give an idea of the buildings and machinery required for mounting a new yard, to produce from 40,000 to 50,000 per week : 1 clay -mill. 120 yards lineal of hovel, 6 yards wide. 1,200 yards superficial of working floor. This extent of hovel and floor will be sufficient for the operations of six moulders; and, taking the work of each moulder to average throughout the season 1,300 per diem, the week's work of the six moulders would produce 46,800 per week, or in round numbers 140,000 every three weeks. This rate of production would render necessary two kilns, each to burn 35,000, and these kilns would be kept in constant activity, each kiln being fired twice every three weeks. 64. For a yard in which it is proposed to make all kinds of brick ware additional buildings will be required, as : Cellars for ripening the ground clay ; A tempering shed, for tempering under cover ; One or more drying-houses, provided with furnaces and flues ; A wash-mill for running the clay for making rubbers. Besides the above erections, there will be required in all yards stabling to a greater or less extent ; a cottage for the under- taker of the yard ; and sheds and out- buildings for keeping tools, carts, and implements. 90 RUDIMENTS OF THE 65. Tools. The tools required by each moulder are : A pair of brass moulds ; A moulding table, and appurtenances complete ; A plane ; A clapper. In addition to these implements a variety of other articles are required, as shovels, picks, barrows, planks, sand baskets, sieves, &c., which are kept in store by the proprietor of the yard, and supplied to the men as required. 66. Labour. The proprietor of the yard finds all tools and implements, sand, and coals, and horses the mills. The general management of the yard is con- ducted by an under-taker, who superintends the yard and contracts with the proprietor for all the labour required in the actual manufacture, at a price per 1,000 on the tale of bricks delivered from the kiln, the under-taker bearing all loss from frost, wet, or other causes. The under-taker sublets the moulding to a moulder, who contracts with him at a price per 1,000 to mould and hack the bricks ready for setting in the kiln ; the moulder employing two boys to assist him in moulding and hacking, and also a temperer, who tempers the clay for him, and assists in getting up the bricks from the floor. The first turning over of the clay is per- formed by labourers, under the direction of the under- taker, who, with the assistance of a few boys and labourers, sets and draws the kilns himself, and attends to the burning. 67. The actual selling price of bricks is regulated more by the demand and the amount of competition ART OF MAKING BRICKS AND TILES. 91 than by the cost of their production. Good building bricks, made in copper moulds, may be had in Notting- ham at 255. per 1,000 ; but a fair selling price may be considered as 28s. per 1,000, which may be thus subdivided : Clay digging ; per 1,000 Turning over and watering clay and feeding mill Grinding ,, Tempering for moulder Moulding, drying and hacking ... Setting and drawing kiln .... Burning ,, Total cost of labour Coal, half a ton, at 8* Duty, 5s. IQd. per 1,000, with 5 per cent, added Clay Rent, tools, machinery, and profit ... Selling price at yard ... 180 This may be considered as the lowest price which will afford any profit to the proprietor of the yard, when proper allowance is made for depreciation in buildings and machinery, tools, repairs, and other contingencies. 68. The relative value of the different qualities of brick may be thus stated : s. d. Common bricks (the clay not picked) . . per 1,000 180 Front bricks (made in copper moulds, the clay picked) 1 13 Polished bricks (made in copper moulds, the earth selected with care, and the bricks dressed on a bench) it 300 92 RUDIMENTS OF THE 69. REFERENCE TO THE ILLUSTRATIONS ACCOMPANYING THE FOREGOING ACCOUNT OF BRICKMAKING AS PRAC- TISED IN NOTTINGHAM. Fig. 1. General view of a brickwork, showing the arrangement of the works. A. The face of the workings. B B. Heaps of brick-earth, dug in the autumn, to be worked up the following season, after being mellowed by the winter frosts. C. The clay-mill. D D. The working floors, generally made about 9 or 10 yards wide. E. The hovel. This hovel isflued, the door at the end of the hovel next the road is the entrance to the furnace pit ; the chimney into which the flues are conducted is shown at the opposite end. In some drying houses the flues are made to return nearly to the furnaces before they are led into the chimney, so that the latter is close to the former. F. The kiln. This form of kiln is a weak one, and is liable to be split from top to bottom by the expansion of the walls, from the intense heat to which they are exposed. The reader will observe the steps and the wooden fence round the top of the walls, men- tioned in article 41. G. Goods for sale. This illustration is not an exact representation of any particular brick- work, but has been made up from the details of several yards, to show the principle on which they are laid out ; which is, to save all unnecessary carriage of either brick-earth or bricks, from the time of first turning over the clay to the stacking of the finished bricks in the sale yard. Figs. 2, 3, and 4. Clay-mill, with a single pair of rollers 18 in. in diameter, and 32 in. long, as manufactured by Messrs. Clayton and Shuttleworth, of Lincoln. The letters of reference are the same in each figure. a. Horse beam, 12 feet long, from centre of horse track to centre of driving wheel. b. Bevelled driving wheel. c. Pinion. d. Driving shaft, 1 in. diameter. e. Universal joint. ff. Spur wheels. y g'. Cast-iron rollers 18 in. diameter and 32 in. long. The roller marked g' is longer than the other, having a flange round each end by which the roller g is kept in its proper position. The roller marked g' is connected by the universal joint e with the driving shaft d. h. Wooden hopper. i i. Cast-iron standards to support the hopper. ft k. Axles of rollers. ART OF MAKING BRICKS AND TILES. 93 / /. Bearings for the axles k k. These bearings are made to slide on the bottom plate m, in order that the gauge of the rollers may be adjusted at pleasure. TO. Bottom plate, on which the bearings rest. n. Strengthening bar. o o. Adjusting screws, by which the rollers can be set to any gauge, according to the degree of fineness to which the clay is required to be ground. p. End beam of framing. q q. Sides of framing. r. Balance weight to horse beam. The rollers in this mill are not faced in the lathe, but they are cast upright in loam moulds, which insures great accuracy in ^casting, and renders turning unnecessary, where only one set of rollers is employed. The arrangement of the rollers, when two or more sets are employed, is shown in chap, iv., figs. 1, 2, and 3, which shows the construction of the clay-mills used in Staffordshire. The temporary floor on which the clay falls after passing between the rollers is formed about 8 feet below them, and is inclosed on three sides with brick walls which support the wooden framework of the machinery. The clay is prevented from adhering to the surfaces of the rollers by strong knives fixed on their under sides. Fig. 5 is a diagram showing an improved arrangement of the ordinary clay-mill, in which the horse track is raised to the level of the top of the hopper, the whole of the machinery under the hopper being completely boxed up, so that no dirt or stones can lodge on the wheels. The driving wheel is placed in a circular pit lined with brickwork to keep up the horse track to the required height. Fig. 6. Isometrical view of a moulding table. A. Sloping plank, placed at one end of the table to enable the moulder's boy to deposit the clay on the table. B. End of the table where the tempered clay is deposited. c. Sand box. This is not always fixed to the table. In many cases it is a detached box, on three legs, placed close to the moulding table. D. The part of the table on which the clot is moulded. E. The place where the clot is put into the mould. F. The water-box, in which the moulder dips his hands each time he moulds a brick. G. A slip of wood on which the plane rests in order to raise it from the table, that the moulder may take it up the more readily. H. The part of the table at which the brick is taken off. This part of the table is always very wet, and the slush runs off into i. Gutter, to carry off the drippings from the table into a tub placed beneath it, but which is not shown in the drawing. If the water were allowed to run down on the working floor, the latter would soon become wet and slippery, and unfit for receiving the bricks. Fig. 7. Copper brick mould. This kind of mould is cast in four pieces and riveted together, the sides projecting half an inch beyond the ends. Each easting has a flange at top and bottom, forming a rim half an inch wide all round the top and bottom of tbs mould. These rims become 94 RUDIMENTS OF THE gradually worn down by the friction of the plane and the action of the moulding sand, and require replating from time to time. The expense of replating with brass has induced a trial of iron rims, but they have not been found to answer. The outside of the mould is cased with wood, secured to the brass by the rivets. To give a hold to the latter, each pair is passed through a piece of sheet copper, as shown in the cut. The moulds for making quarries are somewhat different, two of the sides only being cased with wood, whilst the others are stiffened by strengthening ribs cast on the sides of the mould. Fig. 8. The plane. Fig. 9. The clapper. Fig. 10. Bench on which the best bricks are polished and dressed with a dresser, as described in art. 34. Fig. 11. The dresser. Figs. 12, 13, 14, 15, 16, and 17. Plans, sections and elevations of a kiln. Fig. 12. Plan at level of floor, showing the firing sheds and fire-holes. The latter, in this example, are arched over, and are built of con- siderable width, which is afterwards reduced by temporary piers of brickwork. In many kilns, however, the fire-holes are made at once of the requisite width, and finished at top by oversetting the bricks on each side till they meet, instead of being arched over. The fire-brick lining to the fire-holes is indicated in the plan by a tint darker than that of the rest of the walls. The temporary piers of brickwork are shown in outline only. These are pulled* down whenever the fire-brick lining requires to be renewed. The floor of the kiln is not paved. Fig. 13. Plan, showing the roofs of the firing sheds (B B), and the steps (A) leading to the top of the kiln. Fig. 14. Cross section of kiln, taken through the firing sheds, and showing the construction of the fire-holes. Fig. 15. Longitudinal section, taken through the doorways at the ends of the kiln, and showing the appearance of the fire-holes in the inside. Fig. 16. End elevation of kiln, showing the doorway and the ends of the firing sheds, as well as the steps leading to the top of the kiln. Fig. 17. Side elevation, with the firing shed removed, in order to show the fire-holes. Fig. 18. Perspective view of a kiln. This kiln is built very differently from that shown in the previous figures, the walls being very massive at the bottom, and diminishing in thickness as they ascend. The angles are strengthened by buttresses. The doorways do not reach to the top of the walls, and are arched over, so that the latter form a continuous terrace all round the top of the kiln, on which a thin parapet is built up in a temporary manner, to increase its capacity. ART OF MAKING BRICKS AND TILES. 95 CHAPTER IV. BRICKMAKING AS PRACTISED IN THE STAFFORD- SHIRE POTTERIES. BY K. PROSSER, C.E. 1. Bricks. There are made in this neighbourhood the following sorts of bricks for building, viz., red, blue, and drab, and also a blue brick used as a paviour for footways, which brick is called a dust brick, from the circumstance of coal dust being used when it is moulded. When fired it has a smooth and somewhat glossy sur- face, and being very durable is extensively used as a paviour. 2. The drab brick is used to a limited extent for building, but more generally as a fire-brick by potters and iron-masters ; it is, however, inferior to the Stour- bridge brick, the latter being used where intense heat is generated. 3. Tiles. There is a variety of other articles made in the brick-yards of this locality, as, roofing tiles in several varieties, tubular drain tiles from 3 in. to 16 in. meter, and generally 18 in. long; also floor tiles or quarries both red and blue, the latter resembling the blue brick. 4. Clay. The blue colour is obtained from the same clay that fires red by additional heat being generated when blue is required, at a cost of half a ton more coal, and two hours more time allowed per oven. The clays or marls are selected for the purposes to which they are best adapted, and an extensive supply of the best quality for red is procured at Cobshurst, about two miles south of Longton (which marl is used to make the red orna- 96 RUDIMENTS OF THE mental and encaustic tiles, now so much admired, and which are extensively made by Messrs. Minton and Co., of Stoke-upon-Trent) . Marls and clays suitable for brickmaking are plentiful, and of several varieties, in this neighbourhood, but the most extensive bed of red marl runs in an almost unbroken line through this country from south to north, and generally west of the great coal-field, and is worked with the same results at Stourbridge, Tipton, Hanford, Basford, Tunstall, and other places. A reference to a map of the country will show the peculiarity of this long bed of stratified marls. 5. In the pottery district there are about ten distinct sorts or strata. The following names are given to the seven sorts most used ; and their position with relation to the earth's surface is shown by the order of their names here given. Top red marl, dun coloured, top yellow (rotten red, not used), mingled, bottom yellow, brown, and bottom grey. Seven of these marls vary but slightly in their chemical composition, and, when used, three sorts at least are generally mixed together. (For an Analysis of the above-named marls, see Table 1, art. 37.) In this locality there is a very favourable combination of circumstances for the manufacture of ornamental bricks for architectural decorations; and were archi- tects to give the subject their attention, and such bricks free from duty, much might be done. 6. The following description of the process and cost of brick and tile-making will apply, first, to the make of bricks, &c., upon the property of the manufacturer ; and, secondly, to the make of tiles, &c., at a yard which is rented. ART OF MAKING BRICKS AND TILES. 97 FIRST EXAMPLE. BRICKMAKING. 7. Buildings and Plant. This yard, with the ground opened for work, has an area of about 6 acres, and has the following buildings and machinery upon it, viz. : A 5-horse power steam engine ; A pug-mill ; A set of horizontal rollers ; Six drying-houses ; (Three pairs to the set, placed over And nine ovens, each other). The drying-houses measure 40 yards in length, by 8 yards in width, and have two flues under the floor through their entire length. At times they fire these nine ovens in one week ; and if used exclusively for bricks, each oven could be fired five times in a fortnight. Besides bricks, the following goods are made at this yard : pipe tiles from 3 in. to 16 in. diameter, roof and ridge tiles, quarries, dust bricks, &c. 8. Rate of Production. Provided the make were confined to bricks, with these conveniences they would make 100,000 weekly during the usual brick season, which at the present selling price, 1 8s. per 1,000, gives a weekly produce value .140, which quantity- would pay in duty 27 Us. 3d., the duty being 6s. l^d. per 1,000, with 10 per cent, off : this leaves for cost of production and profit 112 8s. 9d. 9. Tempering. The marls used at this yard answer to the description previously given. Their average con- traction when mixed is 1 in 10; that is, a 10-in. mould gives a 9-in. brick when fired, although some of the varieties used separately contract 1 in 6. The marls are dug and wheeled two runs for 4c?. to 7d. per cub,e yard, the price depending upon the difficulty of digging. The marl is then placed in a hopper over the topmost F 98 RUDIMENTS OF THE rollers, and passing successively through the three pairs, is deposited on a floor about 8 ft. below the hopper. The marl is then wheeled away, and some three or more sorts mixed together with a proper quantity of water, by spade labour (for the quantity of water in the marl when dug, see Analysis, Table 1, art. 37). The mixed marls, if wanted for tiles or dust bricks, are now passed through the pug-mill ; but if required for ordinary bricks, the ground marls are mixed with marls that have been weathered but not ground. Lastly, the marl is tempered by spade labour until the proper degree of plasticity is obtained. 10. Moulding. The bricks are moulded by what, is called the slop -moulding process at the rate of 3,000 per day.* The price paid for tempering and moulding is 46'. 6d. per 1,000. The process is as follows : the temperer wheels the prepared marl in a barrow up a plank, and empties it upon the moulding table. The moulder having sprinkled sand upon the moulding board, and upon that part of the table where the clot is moulded, takes as much clay as will fill the mould, and by a quick roll and a tap gives the clot an approxi- mate form to the mould ; he then lifts up this lump of clay about 12 in. high, and with force throws it into the mould, pressing it down with both hands to fill all the cavities, and strikes off the surplus with a wooden striker, which he throws into a small water-box in front of him after each time of using.f An attendant boy, who has previously dipped a mould in a water-trough by the side of the table, places it on the table ready for the moulder, and carrying away the moulded brick * In the neighbourhood of Nottingham, where the bricks are not stricken, but planed, the rate of production is only 2,000 per day. ED. f See chap. Hi., art. 47. ART OF MAKING BRICKS AND TILES. 99 in the mould,, carefully empties it on its flat side on the floor; these operations are repeated until the floor is filled, when the moulding- table is removed to a second floor. 11. Drying. The floors are of different sizes ; a con- venient size is 25 yards in length by 6 yards in breadth, upon which they will lay 3,000 bricks. Here they are allowed to dry until sufficiently hard to handle and place in hacks, the length of time depending upon the weather. In quick drying weather they will remain half a day as deposited from the mould, and half a day turned upon edge, and afterward they are placed up in hacks, where they remain until placed in the oven. 12. An ordinary blue brick weighs, wet from the mould, 12 Ibs. 4 oz. ; when fired it weighs 8 Ibs. 1 oz., having lost by evaporation in drying and burning 4 Ibs. 3 oz., or 34 per cent, of its original weight. The specific gravity of an ordinary blue brick in the wet state from the mould is . . .2,171 In the dry state, ready for the kiln . . 2,075 And when burned, the specific gravity is . 1,861 The Table on the next page shows the amount of evaporation during the process of drying. The total loss of weight in drying and burning is as follows : 196 ounces, the weight of a brick wet from the mould. 46 lost by drying, or 23^ per cent. 150 dry ready for the kiln. 21 lost in burning, or 14 per cent. 129 of an ordinary blue brick. 13. Burning. The oven is of a circular form, with a F 2 100 RUDIMENTS OF THE !! M I! saouno uj ?q3i9M jo ssoq 5 -1 PM ! t- ^^ W t^- !> 11 g ^ fcX3 G E-i c 'So ' i'g spherical top, and will contain 8,000 bricks, -which are so placed as to allow a space between the sides of each for the action of heat, and an equal diffusion thereof. When the oven is full, the clammins or doorway is made up, and the fires kindled and kept burning 36 hours for red, and 38 hours for blue bricks, consuming 3 J tons of coals for the former, and 4 tons for the latter. The ART OF MAKiftG CRICKS ANB T-IvES. 101 expense of setting, firing, and drawing an oven of 8,000 bricks is as follows : labour 12s., and coals 1 13*. 4d. 14. Cost of Manufacture. The details of the cost of manufacture are as follows : Clay getting Tempering and moulding ... Setting oven, firing and drawing Coals, 4 tons at 8s. 4rf., divided amongst 8,000 Duty, 5. IQd., with 5 per cent, added Kent, machinery, clay, contingencies, and profit Present selling price for ordinary blue bricks 15. Rental. Brick-yards with mines of marls are set with the following appendages, viz. : 1 oven, moulding or drying-house, and pug-mill, with a breadth of brick floor and marl bank sufficient to work one oven for 30 per annum ; if two ovens are worked in the take, they are set at 25 each. 102 ilLDTMENTC OF, THE DESCRIPTION OF ILLUSTRATIONS. 16. Figs. 1, 2, 3, Machine, with three pairs of Rollers, for grinding Marl. Fig. 1. Side elevation. Fig. 2. Front elevation, with the gearing removed. Fig. 3. Elevation of gearing, No. 1 being the driving wheel. CO ART OF MAKING BRICKS AND TILES. 103 17. Fig- 4. Isometrical View of a Moulding Table. A. Sand basket. B. Detached water-box. c. Moulding board D. Water-box. E. Clay knife. In the process of moulding the moulder takes in his hand, from the basket, a portion of sand, and dusts upon that part of the table where he rolls the clay into the form necessary to mould ; also upon tne moulding board. The water -box or trough, B, is used by the boy to wash the mould in, and is lower than the table, so as to be convenient for that purpose. The water-box, D, is level with the table, and is used to throw the strike in after each time of using. 18. Fig. 5. Isometrical View of a Brick Mould. N.B. The mould is made of oak, the edges plated with iron. 104 RUDIMENTS OF THE 19. Figs. 6, 7, 8, and 9. The Oven or Cupola Fig. 6. Plan taken at top of fire-holes at level A B, Fig. 9. MM? Fig. 7. Plan, looking down on top of oven. ART OF MAKING BRICKS AND TILES. 105 Fig. 8. Elevation. Fig. 9. Section, on line c D, Fig. 6. SECOND EXAMPLE. TILE MAKING. 20. At Basford there is an extensive hill of good marls from which eight brick-yards are supplied (working four- teen ovens), some of which have heen in work for forty years. The makers are subject to the rental stated in art. 15. The leading article made at these yards is roofing F 3 106 RUDIMENTS OF THE tiles ; besides which are also made some quarries, dust- b ricks, drain tiles, and just so many common bricks as are necessary for the manufacture of tiles, it being necessary, in order to set the oven properly, to burn 2,000 bricks with every oven of roof tiles, as will be hereafter ex- plained. The process of tile making here is as follows : 21. Weathering and Tempering. The marl is dug and spread upon slopes of this hill (which has a south- east aspect) to weather; the length of time depends upon the quality of the air : a hot dry summer's day will do good service, and three or four such days would enable the makers to collect a thin surface in a work- able condition. Frosty weather, provided it be dry, is preferred ; wet, and alternations of wet and dry, retard the process of what is termed weathering. During a hot dry season marl can be dug, weathered, and made in one month, and this is frequently done. At the yards here referred to, the workers collect their marls, so weathered, at the foot of these slopes, and mix them with a quantity of water. That to be used for tiles is placed in the pug-mill, and about 1 cube yard per hour is ground by one horse; and that used for common bricks is not ground, but simply mixed and tempered. The pug-mill consists of a wooden tub slightly tapered, the largest end being uppermost ; it is circular and about 6 ft. high and 3 ft. diameter at the top or largest end, in which a cast-iron spindle revolves, carrying a series of flat steel arms, arranged so as to form by rotation a spiral or worm-like motion upon the clay, which is thereby pressed from a larger to a less diameter of the tub in which the clay is confined, and ultimately comes oozing out of an aperture at the bottom : this operation kneads the clay, and more com- pletely mixes it, giving it great cohesive power. This ART OF MAKING BRICKS AND TILES-i 107 clay or prepared marl is now ready to make roof tiles, dust bricks, quarries, &c., and is wheeled away to the stock kept under cover for that purpose. The tiles, and all articles in the making of which coal-dust is used, are made in a building called by brickmakers the hovel or drying house : but they prefer placing their tiles when first moulded in the open air, weather permitting. The moulding of roofing tiles varies from that of bricks before described, principally in the clay being stiffer, and coal dust being thrown in the mould each time it is filled. 22. Moulding. The mould is 12 in. by 7J in. and ^ in. thick, made of oak plated with iron. The moulder at his bench takes up a lump of clay, and works it by hand into an oblong square, somewhat less than the mould, say 1 1 in. by 7 in. or thereabout ; the mould is placed upon the bench, and fine coal-dust thrown into it ; the man then takes up the lump of clay in the right position for the mould, and throws it into it with con- siderable force ; then, with a brass wire strained upon a wooden bow, cuts off the surplus clay level with the mould, removes the lump, and finishes moulding the clay left in the mould by adding a little clay if it be wanted, and smooths it over with a wooden^tool. By his side upon the bench he has two thin boards about the size of the moulded tile, their surfaces are dusted over with coal-dust ; upon one of these he places the moulded tile, without the mould, the half circular pro- jections extending beyond the board ; and so he repeats the process of moulding at the rate of from 1,300 to 1,500 per day, adding more clay to his lump about every six tiles moulded, and in quantity about as much as the six tiles moulded. 23. Drying. The attendant boy carries away two 108 RUDIMENTS OF THE tfles at each time to the floor ; he takes up one on the board, and by the thick part of the hand presses up the two projections at right angles with the face of the tile, and then places board and tile on his head, and takes up a second and operates upon this in like manner, as he walks to the floor, where he lays the two tiles, carrying the boards back to the moulding bench ; and so he repeats his operations. The tiles remain on this floor, out of doors in fine weather, about four hours ; they are then collected and placed close together, the nib end changed alternately to allow of their resting close and square ; in this state they are walled up in a dry but not hot situation, and so remain for a day or two : this is said to toughen them. 24. The Set. The next process is to give them a curved form, sometimes termed the set, which is done on a three-legged stool, called a horse, the top of which is a little larger than the tile, and is curved one way to about a 10 feet radius. With the horse is used a wooden block, curved to correspond with the surface of the horse. These implements are used as follows : six tiles are taken as last placed and put on this horse ; the man lifts up the wooden block and gives them three sharp blows with it ; they are then carried away and placed in an ingeniously built wall to complete the drying process (the wall built with the tiles to be dried), after which they are carried to the oven, twelve at each time, in a peculiar manner, with the edges of the tiles against the breast of the carrier. 25. Quarries and dust bricks are moulded in like manner from stiff clay, coal-dust being used to facilitate the articles leaving the mould. 26. Drain Tiles* Pipe drain tiles are made as foi- ART OF MAKING BRICKS AND TILES. 109 lows : the clay is first moulded to the length, width, and thickness required, and then wrapped round a drum, the edges closed together by hand, the drum or mandril turned round, and the pipe tile shaped by the operator's hand, assisted in some cases by a wooden tool : this is the mode of making pipe tiles from 3 in. to 16 in. in diameter, whether cylindrical, tapered, or egg-shaped. The usual length is 18 in., and the diameter from 3 in. to 9 in. They are sold at Id. per in. bore ; that is, a pipe 3 in. in diameter and 18 in. long, would cost at the yard 3d. ; and a pipe 9 in. in diameter and 18 in. long, 9d. This price applies to cylindrical pipes without sockets. 27. Tile Machines. One of Ainslie's machines has been introduced into this neighbourhood, upon the estate of the Duke of Sutherland, for making small tubular drain tiles, which makes two pipes 1J in. in diameter at the same time. The prepared clay is forced through two dods to form the tubes, which are cut into lengths by wires affixed to the machine, and when partially dry are rolled straight by hand upon a flat surface, and then set up in racks to finish the drying process. 28. Firing.* Firing the articles enumerated in the previous description requires much more care than firing bricks, and as roof tiles are the thinnest and require most care, the largest sized pipe tiles excepted, we shall describe firing an oven of such tiles. On the bottom of the oven are first placed 2,000 bricks, as shown in fig. 13, and upon these are placed 7,000 tiles, forming a square, the spaces between the tiles and the curved side of the oven being filled up with bricks, as shown in fig. 14. The tiler are placed 110 RUDIMENTS OF THE edgewise, in parcels of twelve, changing their direction each parcel of twelve. The nibs on the tiles space them off from each other, and support them in the vertical position ; from this description, and a reference to the illustrations, it will appear, that the goods placed in the oven are in each case so placed as to allow the diffusion of heat between them ; and as the uniformity of heat is the desideratum in firing blue bricks and tiles, the circular oven is found to answer better than any other at present in use. It is necessary to have a wall round the outside of the oven, about 6 ft. high, and at a distance therefrom to allow the fireman space to attend his fires conve- niently ; this wall is dry built generally with imperfect bricks, and its use is to avoid one fire being urged more than another by the set of the wind, which duty it performs tolerably well. The oven being set, the clammins (doorway) is made up with bricks daubed over with street sweepings as a loam ; then the fires are kindled, and are kept slowly burning for the first 5 hours, after which they are pro- gressively increased for the next 33, making 38 hours for hard fired blue tiles or bricks; four tons of coal being consumed in the firing. The heat is determined by the sight of the fireman directed to the mouths and top outlet of the oven. When the heat is obtained, and before the fires burn hollow, the mouths are stopped up with ashes to prevent the currents of cold air passing through the oven, which is then suffered to cool gradu- ally. An oven is usually fired once a week, but may be fired three times in a fortnight. After firing, twenty- four hours should be allowed for cooling before an oven is opened to take out the tiles. 29. The following table shows the selling price per ART OF MAKING BRICKS AND TILES. Ill 1,000, and cost per superficial yard, of quarries, dust bricks, and roof tiles : Size. Price per 1,000. Superficial mea- surement per 1,000. Price per superficial yard in pence. Thickness. Description. 6 in. sq. 7 35s. 46s. 27-89 yards. 37-80 15-00 14-59 I 1 inch Quarries. 9 80s. 62-50 15-36 I*. > 9X4f 40s. 31-25 14-33 2 Dust bricks. 10 8X7 25s. 58-33 5-14 Roof tiles. DESCRIPTION OF ILLUSTRATIONS. 30. Fig. 10. Isometrical View of a Bench for moulding Tiles. A. Coal-dust box, 14 in. by 8 in. B. Moulding board, 14 in. by 10 in. G. The bow. 31. Fig. 11. Elevation, showing the Manner in which the Tiles are placed during the last Drying. d (A laths, two to each course. 112 RUDIMENTS OF THE 32. Fig. 12. Tile Block and Horse, a. The block. b. The horse. c Tiles. 33. Fig. 13. Plan of Oven, as seen when eight courses of Bricks are placed edgewise. The eight rows of twelve bricks in each, as seen in plan, cover a apace left in continuation of flues from the eight fire-holes. The bricks in the first seven courses are so placed as to leave a flue of an average width of 4 inches. The dotted Hnes show the position of the fire-holes. ART OF MAKING BRICKS AND TILES. 113 34, Fig. 14. Plan of Oven, as seen when the first course of Tiles are placed upon the Bricks, as seen in Fig. 13. The tiles are placed in bungs of twelve, and laid alternately cross and lengthwise, the nib spaces them off, and supports them in a vertical position. Each side of the square is made up with bricks, as shown on the plan. 35. The manufacture of bricks, &c., for building and paving purposes, in a systematic manner, in suitable premises with improved conveniences, so that the opera- tives may be employed the whole of the year instead of a portion of it as now, is a subject deserving the atten- tion of the capitalist and inventor. Improvements in the quality and conveniences of this manufacture are intimately connected with the moral, intellectual, and physical condition of society, as may be seen by a visit to any ordinary brickyard, and a reference to the evidence before the Sanitary Commission. Where ex- tensive supplies of marls or clay are found, suitable works might be erected for such manufacture, could a 114 RUDIMENTS OF THE cheap and ready mode of transportation be commanded, so as to carry bricks, &c., a distance of 60 to 100 miles without materially increasing their price. 36. Assuming the weight of bricks to be 3^ tons per 1,000, the present railway charges for the carriage of bricks, viz. 2d. per ton per mile, if under 40 miles, and I%d. per mile if more than 40 miles, would add to their cost as follows : s. d. If carried under 40 railes . . .00 7 per 1,000 per mile. Or for a distance of 39 miles . .129 And if carried above 40 miles . .00 6 per 1,000 per mile. Or for a distance of 60 miles . .1107 Therefore a carriage of 60 miles at the lowest railway rate more than doubles the value of a common brick compared with the price at the yard. The high rate of charge for carriage, and the duty, which amounts to nearly 22 per cent, of the selling price at the yard, constitute obstacles to the improvement of the brick manufacture, and the bettering of the condition of the operatives em ployed therein. The recent improvemeDts in connection with domestic comfort and health, and the encouragement offered to architectural improve- ments in the houses for artisans, may probably awaken an interest in this department of industry, and place even brickinaking in the position its importance deserves, if not demands. ART OF MAKING BRICKS AND TILES. 115 TOM 00 1O 00 TJ< CO co -ajg B jjnq ^Si{ suanq '[.rum aa&SBg 00 w . *P 1 'P 1 r 1 i i ?' ^^ i QO i i r> 04 O) aniq uanq ^on HIM pun 'paj O (7^ ^H . ^ . g -^ oo CO suanq '^uajj,-uodn *^ O ^ CJ 1 r* 1 g _i w g -aqo^s raoaj XB[3 H aniq poo3 suanq ^g^ 6 2 g '? PUB 's '& 'I "sotf 'SXB[0 JO ajn^Xllfl goo 1 I 1 1 1 co * eqi puB*js ;ou HIM. o Tl< i-H t- CO l-l O Tj< 00 CO OS . CO O (N . C3> 01 t^ tD 1 >O -<" 0 (^ 00 O C3J t- t^ r- anjq qsippaj snanq 'iJBra ^.oip^! doj, CO ^ - 1 T* 1 i V 3 i i i P 00 | rH 1 | 1 T* 4 . The shoot to the brick-earth. E. The brick-earth turned over in readiness to receive the malm. F. The pug-mill. o. The moulding stool. n. The hack ground. K.K. Clamps. 53. The Chalk-mill. Figs. 2 and 3. Section and Plan. (Scale 10 ft to an inch.) a.a. Grinding-wheels. I. Inlet from pump. c. Outlet to clay washing-mill. Details. (Scale 5 ft. to an inch.) Fig. 4. Grinding-wheel. Fig. 5. Mode of connecting the axle-tree of the grin ding- wheels with the centre shaft. The mill consists of a circular trough lined with brick- work, and furnished with a pair of heavy wheels witli spiked tires, which, being drawn round by horses, crush arid grind the chalk until it is reduced to a pulp. The wheels arc shown in detail in fig. 4. It is necessary that they should accommodate themselves to the level of the chalk in the trough, and to effect this, the framing ART OF MAKING BRICKS AND TILES. 165 of which the axle-tree forms a part is secured to the centre shaft by a staple, as shown in fig. 5, which allows the whole of the timbering to rise or fall, as may be requisite. The centre shaft is a bar of iron, steadied by being built up in a mass of brickwork. The yoke beams are kept at the proper height, and their weight supported by common light chaise wheels, about 2ft. 6 in. diameter, which run on the outside of the horse track. The mill represented in these engravings is mounted for two horses ; many mills, however, have but one. 54. The Clay-washing Mill. Figs. 6 and 7. Plan and elevation. (Scale 10 ft. to an inch.' a. The inlet from the chalk-mill. b. The outlet to the shoot. c.c. The harrows. d.d. The cutters. e. The pump. Details. (Scale \\ in. to 5 ft.) Fig. 8. The cutters. Fig. 9. The outlet to the shoot, and the strainer. Fig. 10. The strainer. The mill consists of a circular trough of larger dimen- sions than that of the chalk-mill, also lined with brick- work, and furnished with a two-horse gin, to which are attached knives and harrows, which, in their passage round the trough, cut up the clay and incorporate it with the pulp from the chalk-mill. The framing of the gin is very simple, and requires no description. The knives, or cutters, are placed in two sets, four in each. They are fixed in an upright position, and steadied to their work by chains, and by being bolted together with bolts passing through tubular distance pieces, as shown >n fig. 8. The knives cut the clay and clear the way for the harrows, which are similar to those ujsed for agricultural purposes, and are merely suspended by 166 RUDIMENTS OF THE chains from the timber framing. The pump is worked by the horizontal wheel F, fig. 7, which is provided with friction rollers on its rim, for the purpose of lifting the lever G, which raises the lever of the pump by means of the spindle H. The outlet to the shoots is simply a square trunk made of 2 in. plank. It is furnished with a brass grating, or strainer,, shown in fig. 10. The bars are f in. wide, and J in. apart, so that even small stones will not pass through. This grating is fixed in grooves, so that it can be lifted out of its place by the handles, when required. 55. The Pug-mill. Fig. 11. Elevation. (Scale 4 ft. to an inch.) a. The yoke arm. b. The opening for the ejectment of the earth when ground. c. The brick-earth surrounding the mill, on which is an inclined barrow road to the top of the mill. Fig. 12. Section. (Scale 2 ft. to an inch.) a.a. Force knives. These are not provided with cross knives, their purpose being merely to force the ehrth downwards and out at the ejectment hole. 56. Fig. 13. Isometrical View of the Moulding StooL (Scale 4 ft. to an inch.) a. The lump of ground earth from the pug-mill. b. The moulder's sand. c. The clot-moulder's sand. d. The bottom of the mould, termed the stock-board. e. The water-tub. /. The page, which is formed of two rods of f ths of an inch round or square iron, nailed down at each end to the wooden rails or sleepers on which they rest. The use of the page is to slide the new bricks, with their pallets, away from the moulder with facility. ff. The pallets in their proper position for use. h. A newly-made brick just slidden from the moulder, and ready for the taking-off boy. k. The moulder's place. m. The clot-moulder's place. n. The taking-off boy's place. 0. The cuckhold, a concave shovel used for cutting off the ground-- earth as it is ejected from the pug-mill. ART OF MAKING BRICKS AND TILES. 167 75. Fig. 14. Isometrical View of the Brick Mould, with its detached bottom or Stock-board. (Scale 2 in. to a foot.) a.a.a. The iron pegs on which the mould rests during the opera- tion of moulding. They are driven into the stool in the positions shown in the drawing ; their height from the stool regulates the thickness of the brick. The mould is lined throughout with sheet-iron, which is turned over the edges of the mould at the top and bottom. 58. Fig. 15. The Hack .Barrow loaded. (Scale 2 ft. to an inch.) ! Fig. 16. The hack barrow unloaded. (Scale 2 ft. to an inch.) 59. The Clamp. Fig. 17. Transverse section (parallel to necks). (Scale 10 ft. to an inch.) Fig. 18. Longitudinal ditto ditto ditto. a. The upright. b.b. Close bolts. c. Live hole. d. Bestowing. Details. (Scale 2 ft. to an inch.) : Fig. 19. Plan of the lower course of scintles. : Fig. 20. Plan of the upper course of scintles. . The live hole. It should be understood that the directions of the scintles, as well as that of the paving below it, are changed for every neck, so as to correspond with the upper work, as shown in the figures. Fig. 21. Detail of the end of the upright, showing the paving, the scintling, the live hole, and the 7 in., 4 in., and 2 in. courses of breeze. CHAPTER VI. LONDON TILERIES. 1. The general term, " Tile Manufacture/' is so com- prehensive, that it would be impossible, within the limits of a little volume like the present, to give anything like a complete account of the manufacture of the different 168 RUDIMENTS OF THE articles made at a large tilery ; we only propose, there- fore, in the present chapter, to give a succinct account of the manufacture of pantiles, as carried on at the London tileries, which will serve to give the reader a general idea of the nature of the processes employed in tile-making. It must, however, be borne in mind, that although the principle of proceeding is the same in each case, there are no two articles made exactly in the same way, the moulding and subsequent processes being carried on in a different manner, and with different tools and implements, for every description of article. The manufacture of plain tiles and drain tiles has already been described in Chap. IV., to which the reader is referred, as also to the supplementary chapter at page 220. 2. The following is a list of the principal articles made at the London tileries : Oven tiles. 10-in. paving tiles. Foot ditto. Plain tiles. Pantiles. Ridge tiles. Hip tiles. Drain tiles. Kiln bricks. Fire bricks. Paving bricks. Circulars (for setting coppers,&c.) Column bricks (for forming co- lumns). Chimney-pots. Garden-pots. Drain pipes. And anything required to order. For all these articles (excepting fire bricks) the same clay is employed (mixed, for the making of paving tiles, oven tiles,* kiln bricks, paving bricks, circular bricks, and column bricks, with a certain quantity of loam), and they are all burnt in the same kiln, the fire bricks included ; but each different article presents some pecu- liarity in the processes intervening between the tem- pering and the burning, having its separate moulding- * For oveii tiles the stuff must be of superior quality. ART OF MAKING BRICKS AND TILES. 169 stool, frames, strike, &c., and being stacked and dried differently. The details of these differences, however (even would our limits allow us to describe them), would scarcely be suited to the pages of a rudimentary work tended for popular reading. K 170 RUDIMENTS OF THE 'iqs. 2 and 3. J/V BUILDINGS AND PLANT. 3. Pug-mill. The pug-mill used in tile making for pugging, or, as it is termed, grinding the clay, differs considerably from that used in brick-making. The tub, instead of being conical, is made to taper at both ends, ART OF MAKING BRICKS AND TILES. 171 Eg.b. 15 and the ejectment hole is at the bottom instead of in the front, as in the brick pug-mill. The knives, also, are made in a superior manner. 172 RUDIMENTS OF THE Fig. 4. Fig. 7. Fig. 8. Fig. 9. The mill is provided with force knives without cross knives at top and bottom. See figures 1, 2, and 3. The pug-mill is placed under cover in a shed called the grinding shed. ART OF MAKING BRICKS AND TILES. 173 Fig. 6. 4. The Slinff, fig. 4, is simply a piece of thin wire with two handles, used for cutting the clay. 5. Moulding Shed. Tiles are made under cover in sheds about 7 yards wide, the length of the shed de- pending on the number of moulding tables, the area allotted to each table being about 7 yards in length by 4 yards in breadth. The moulding tables are placed against one side of 174 RUDIMENTS OF THE Fig. 10. the shed, and the remainder of the area is occupied by the blocks or drying-shelves ; every shelf being formed with three 1 in. planks placed edge to edge, and sepa- rated from each other by bricks placed edgewise at the end of the planks, as well as at intermediate points, each block containing about 14 shelves, and thus measuring 12 ft. long by 2 ft. 8 in. wide, and about 7 ft. high. A passage way, 3 ft. wide, is left round the blocks, to give free access to every part of them. These details will be understood by reference to fig. 5. G. The Pantile Table, or moulding table, is shown in ART OF MAKING BRICKS AND TILES. 175 jr. 11. Fig. 12. Fig. 16. Fig. 15. fig. 6. It is furnished with a trug or trough, in which the moulder dips his hands when moulding, and with a block and stock-board, on which the tile mould is placed in the operation of moulding. 7. The Block and Stock-board is shown in fig. 7. The two form one piece, which rests on the moulding table, and is firmly keyed to it by means of a tenon on 176 RUDIMENTS OF THE Fig. 13. thb under side of the block passing through a mortice in the table. Four pegs, driven into the table at the corners of the block and stock-board, serve as a support for the mould and regulate the thickness of the tile, fin. being the thickness of a pantile. ART OF MAKING BRICKS AND TILES. 177 Fig. 14. IFT 8. The Tile Mould is shown in fig. 8, and requires no particular description. 9. The Roll, fig. 9, is merely a round roller ef a particular size, as shown by the scale, and is used for striking a smooth surface to the tile. 10. The Washing-off Table, fig. 10, is a stand with i 3 178 RUDIMENTS OF THE Figs. 17 and 18. fi --"36 7- _ 10 20 30 40 SOFT a water trough and a frame called the Washing- off Frame, see fig. 11, on which, when moulded, the tile is ART OF MAKING BKICKS AND TILES. 179 Fig. 19. 10 20 30 40 washed into a curved form. The washing-off table is placed at the left hand end of the pantile table, and near the block. 180 RUDIMENTS OF THE Fig. 20. 10 20 30 40 11. The Splay er, fig. 12, is an instrument on which the tile is removed from the washing-off frame to the block. 12. The Thwacking Frame, fig. 13, is a frame on ART OF MAKING BRICKS AND TILES. 181 Fig. 21. 182 RUDIMENTS OF THE Fig. 22. ART OF MAKING BRICKS AND TILES. 183 which the tile, when half dry, is thwacked or beaten with a thwacker (tig. 15), to correct any warping which may have taken place whilst drying in the block. When thwacking those tiles taken from the bottom of the block, the thwacking frame is placed upon the Thwacking Stool, fig. 13 ; but when the tiles to be thwacked are at the top of the block, the thwacking frame is placed upon the Thwacking Horse, fig. 14, which brings it conveniently to their level. The Thwacking Knife, fig. 16, is used for trimming the wing of the pantile immediately after thwacking. 13. The Tile Kiln, figs. 17, 18, 19, 20, 21, and 22, consists of a kiln with arched furnaces, enclosed in a conical building called a dome. The arrangement of the whole building will be clearly understood by refer- ence to the figures, and to the detailed description at the end of this chapter. PROCESS OF MANUFACTURE. 14. Clay-getting and Weathering. The clay used for making tiles is purer and stronger than that used for making bricks, and consequently requires more care in its treatment. When the clay is too strong, it is mixed with sand before passing it through the pug-mill, but this is not often required. The weathering of the clay is performed by spreading it out in thin layers, about 2 in. thick, during the winter, and each layer is allowed to receive the benefit of at least one night's frost before the succeeding layer is placed over it. Sometimes the clay is spread out in the summer to be scorched by the sun, which effects the weathering equally well. The greater the heat, or 184 RUDIMENTS OP THE the sharper the frost, the thicker may be the layers, but 4 in. is the maximum thickness. The object of the process of weathering is, to open the pores of the clay, and to separate the particles, that it may absorb water more readily in the subsequent process of mellowing. The clay thus weathered is thrown into pits, where it is covered with water, and left for a considerable time to mellow, or ripen. 15. Tempering. The process of tempering is per- formed simply bypassing the clay through the pug-mill. If the clay be very foul, that is, full of stones, it is slung before using, and passed a second time through the mill. For chimney-pots and similar articles, the clay is slung either once or twice, and pugged, or, as it is called, ground, twice or thrice, according -to the nature of the clay, and the purpose to which it is to be applied. 16. Slinging. The operation of slinging is as fol- lows : as the clay issues from the ejectment hole of the pug-mill, it is cut into lengths of about 2 ft., with a sling. These lumps are taken by the slingers and cut up into slices, not exceeding f in. in thickness, during which operation most of the stones fall out, and those which remain are picked out by hand. The clay thus freed from stones is once more ground, and is then ready for the moulder. (N.B. In some parts of England the clay is freed from stones by sifting, and the tempering is performed by treading ; this part of the work being done by boys, who tread in a spiral track, so as to subject each portion of the mass to a uniform amount of kneading.) 17. Moulding. The clay, as it issues from the mill, is cut into lumps, called pieces, which are stacked on a rough bench in the grinding shed. A labourer cuts ART OF MAKING BRICKS AND TILES. 185 these lumps in half, each half being called a fialf-piece, and wheels these half-pieces one by one to the pantile table. A rough-moulder, generally a boy, takes the half- piece and squares it up, that is, beats it up into a slab near the shape of the mould, and about 4 in. thick, from which he cuts off a thin slice, the size of a tile, and passes it to the moulder. The moulder, having sanded his stock-board, and placed his mould on the four pegs which regulate the thickness of the tile, takes the slice of clay from the rough-moulder, and puts it into the mould. He then, with very wet hands, smooths the surface, cutting off the superfluous clay with his hands, in long pieces, called strippings, which are thrown to a corner of the table. This done, he strikes the surface level with the roll; and turning the tile out of the mould on the washing-off frame, with very wet hands washes it into a curved shape. He then strikes it smartly with the splayer, and turns it over on that implement, on which he conveys it to the block, where he deposits the tile with the convex side uppermost, and, the splayer being withdrawn, the tile is left to dry. The button end of the tile is placed inside the block. 18. Thwacking. The tiles remain in the block until they are half dry, when they are taken out one by one, placed on the thwacking frame, and beaten with the thwacker to perfect their shape. The wing of each tile is then trimmed with the thwacking knife, and the tiles replaced in the block, still with the convex side uppermost ; but this time the button end is placed outside. The tiles then remain in the block until ready for kilning. It should be observed that the tiles flatten slightly 186 RUDIMENTS OP THE whilst in the block, and for this reason the washing-off frame is made a little more convex than the thwacking frame, which corresponds to the permanent form of the tile. 19. Kilning. In setting the kiln, a course of vitrified bricks is laid at the bottom, herring-bone fashion, the bricks being placed 1| in. apart. On this foundation the tiles are stacked as closely as they will lie, in an upright position, one course above another. As the body of the kiln is filled, the hatchways are bricked up with old bricks, and when the kiln is topped, they are plastered over with loam or clay. The top is then covered with one course of unburnt tiles, placed flat, and lastly, upon these a course of old pantiles is loosely laid. The fires are lighted on Monday morning, and are not put out until Saturday evening, whatever the articles in the kiln. The fuel used is coal, and the quantity consumed at each burning about eight tons. This, however, varies with the kind of articles to be burnt, hollow goods, as chimney- -pots, garden-pots, &c., requiring less than more solid articles. Foot tiles, oven ditto, and 10-in. ditto, are stacked in the kiln the same way as paving bricks. The covering on the top of the kiln varies in thickness, according to the sort of goods to be fired. COST OF MANUFACTURE.* 20. From the manufacture of tiles being carried on under cover, the establishment of a large tile-work involves a considerable amount of capital. The kiln * The estimates _here given refer to the First Edition, except where otherwise stated. ART OF MAKING BRICKS AND TILES. 187 used in London is very costly, such a one as we have shown in figs. 17 to 22 costing in its erection no less than 2,000. The cost of making pantiles is about as follows > per 1,000 : s. d. Clay this is usually included in the rent, but, if pur- chased separately, may be taken at 2s. 6d. per yard cube 2j yards cube make 1,000 pantiles . . .0 Weathering clay Mellowing ditto, and grinding once .... Add for horsing the pug-mill .* . . .0 If slung and ground a second time, add . . . .0 Moulding, including all labour in fetching clay from mill, moulding, washing, blocking, thwacking, and blocking second time 10 Setting and drawing kiln Burning 15 Cost of making Rent, repairs, breakage, contingencies, and profit Selling price per 1,000 2 4 1 1 5 10 3 10 21. The following are the ordinary prices, in 1862, for a variety of articles, which will give an idea of the comparative amount of labour bestowed upon them : d. Plain tiles per 1,000 2 4 Patent tiles . > 3 6 Pan, hip, or ridge tiles Ornamental plain tiles 3 3 5 4 Paving tiles, 9 in. , 9 10 t 12 12 14 10 Mathematical tiles, red 3 white 3 10 Oven tiles each 9 22. The above sketch of the manufacture of pantiles give the reader a general idea of the processes used in tile-making, but every article presents some pecu- liarity of manufacture. Plain tiles are dried on flats, called Place Grounds. Hip and ridge tiles are washed 188 RUDIMENTS OF THE and thwacked in a similar manner to pantiles. Drain tiles are only washed. Paving tiles and oven tiles are stricken with a flat strike instead of the roll, and are not washed, but they are thwacked and dressed with a knife. 23. Description of Illustrations. Figs. 1, 2, and 3. The pug-mill. The pug- mill used in tile-making is different from that used in brick- making, as will readily be seen from the figures. Fig. 1. Elevation of pug-mill. (Scale in. to the foot.) Fig. 2. Details of the knives. (Scale 4 in. to the foot.) These knives are made in a superior manner to those of the brick pug-mills, both as regards strength and fitting. The mill is provided with force knives at top and bottom, which have no cross knives attached to them. Fig. 3. Cross section of the tub. (Scale J in. to the foot.) a. The ejectment hole, which is at the bottom of the tub, and not at the side, as in the brick pug-mill. Fig. 4. The sling, or wire knife, used for cutting the clay into lengths as it issues from the pug-mill, and also for freeing the clay from stones (slinging). Fig. 5. The tile shed, shown in plan and section. (Scale 10 ft. to the inch.) a.a.a. The blocks, which consist of a series of shelves, on which the tiles are placed to dry. Each shelf is formed of three 11-inch planks. The shelves are 4 in. apart, and are spaced off from each other by bricks laid edgewise, at the end of the block, and also midway between these points. b.b.b. The moulding tables. Fig. 6. The pantile table, used for moulding pantiles. (Scale f in. to the foot.) a. The half-piece squared up. b. The block and stock-board. e. The trug or trough. d. The moulder's sand. e. The strippings. / A hole in the table for sweepings to drop through. g.ff.ff. The pegs on which the mould is placed. There are four of these pegs ; viz., one at each corner of the block and stock-board ; and the distance to which they are driven below the top of the stock-board, determines the thickness of the tile.* Fig. 7. The block and stock-board. (Scale 1 in. to the foot.) c. A tenon, which drops into a mortice in the table. d. A mortice in c, by which the block and stock-board is keyed tightly to the table. Fig. 8. The pantile mould. (Scale 1 in. to the foot.) Fig. 9. The roll. (Scale I in. to the foot.) ART OF MAKING BRICKS AND TILES. 189 Fig. 10. The washing-off table. (Scale in. to the foot.) a. The washing-off trug. 6. The washing-off frame. Fig. 11. The washing-off frame. (Scale 1 in. to the foot.) Fig. 12. The splayer. (Scale 1 in. to the foot.) Fig. 13. The thwacking frame placed on the thwacking stool. (Scale 1 in. to the foot.) Fig. 14. The thwacking horse, on which the thwacking frame Is placed for thwacking those tiles at the top of the blocks. (Scale } in. to the foot.) a. The table on which the thwacking frame is placed. d. The place where the thwacker stands to thwack. c.c. Two wheels to facilitate the moving of the horse from place to place when required. Fig. 15. The thwacker. (Scale 1 in. to the foot.) Fig. 16. The thwacking knife. (Scale 1 in. to the foot.) This is simply an iron blade, with a piece cut out exactly to the intended profile of the wing of the pantile, which is trimmed with it immediately after thwacking. Figs. 17 to 22. The tile kiln. (N.B. The whole of the furnace and body of the kiln is constructed of fire brick.) Fig. 17. Plan of the kiln, taken through the body. (Scale 20 feet to the inch.) h.h. The hatchways. Fig. 18. Plan of the basement, to the same scale, showing the entrance to the vaults. Fig. 19.* Section through the centre of the kiln, in the direction of the line a b, fig. 18. (Same scale.) Fig. 20. Section through the centre of the kiln, in the direction of the line c d. (Same scale.) Fig. 21. Transverse section of the furnaces. (Scale \ in. to the foot.) The section marked a is taken through the throat of the furnace, on the line marked x y, in fig. 22. Fig. 22. Longitudinal section of the furnaces. (Same scale.) The arrows in each of the above figures show the direction of the flues. CHAPTER VII. ON THE MANUFACTURE OF ENCAUSTIC TILES. 1. The highly-decorative pavements of the mediaeval ages, principally to be found in our old ecclesiastical structures, which often shared the fate of many beautiful * This cut and the following are not quite accurate, the sides of the dome not being straight, as shown in the engraving, but slightly convex. 190 RUDIMENTS OF THE details of architectural ornament, by being made to give way to what rustic churchwardens, and others of equal taste and discernment, deemed improvements after attracting the attention of the antiquary for centuries, have at length excited some interest amongst the prac- tical minds of these our stirring business times. About thirty years since a patent was obtained by Mr. S. Wright, of the Staffordshire Potteries, for the revival of this interesting branch of art, for such it may be truly called. As might have been expected, many difficulties beset the patentee, and for some years nothing was pro- duced equal to the old specimens. But still a beginning was made that promised success when skill and capital, and a determination to succeed, should be brought to bear upon the subject. And these were not long want- ing, as the patent ultimately passed into the hands of a gentleman undeterred by difficulties or previous failures, and who expressed his intention to make encaustic tiles, such as would secure the public approbation, even if each one cost him a guinea! This is the spirit that has achieved such surprising results in our manufactures generally, within a comparatively brief period ; and no wonder that in this, as in most other instances, success has been the satisfactory result. We need scarcely say that the gentleman referred to is Mr. Herbert Minton, who, with untiring industry, collected the best speci- mens of old tiles that could be found in this country, and by a succession of experiments overcame the obstacles that had retarded the success of the undertaking. 2. The chief of these obstacles was, to discover clays of different colours that could be made to amalgamate in such a way as to contract or shrink equally during the processes of drying and firing; and until this was effected, a perfect tile of several colours could not be produced, ART OF MAKING BRICKS AND TILES. 191 sundry unsightly cracks appearing on the inlaid parts of the surface. It will be unnecessary to speak of the present state of perfection to which these beautiful tiles have been brought, further than to observe that they are yearly becoming more appreciated, both on the score of durability and ornament; and there can scarcely be a doubt that, very soon, no ecclesiastical building, having any pretensions to architectural superiority, will be con- sidered to be complete in its decorations without them. By way of information, we may add, that not only copies of old tiles are manufactured, but every variety of design suitable for the character of the building they are intended for are supplied. Indeed, almost any pattern can be produced with facility; and we have seen some of the arms of our nobility and gentry so finely executed, that the uninitiated might be pardoned for mistaking these inlaid clays for the highly-finished and elaborate work of the pencil. In many instances they have been adopted as a substitute for oil-cloth in the halls and passages of the mansions of our nobility, being considered far more beautiful, and, from their durability, more economical also, in the long run. 3. We will now take a peep into the interior of Messrs. Minton and Co/s manufactory.* We must first notice, that the clays of which the tiles are composed are ob- tained in the immediate neighbourhood the ordinary marl producing a good buff" colour when fired ; another kind a warm red ; black is produced by staining with manganese; blue with cobalt, &c. W'th the native clays there is a slight admixture of Cornwall stone and clay, and flint from Kent, &c. The whole are subjected to a variety of washings and purifications the clay in- * Further details will be found in " Tomlinson's Cyclopedia " article, Pottery and Porcelain. 193 RUDIMENTS OF THE tended for the surface, especially and passed through fine lawn sieves in a liquid, or "slip" state, as it is technically termed. In this state it is conveyed to the slip-kiln, or rather pumped on it, and boiled, until it is in a plastic state, and fit for use. 4. After the modeller has done his part, the pattern is cast in plaster in relief, and is then placed in a metal frame of the size required ; but it should be stated that to produce the ordinary 6-in. square tile, it is modelled 6f in., to allow for shrinkage or contraction, which takes place during drying and firing. The maker then com- mences his operations. A piece of the fine clay for the surface is flattened out to about a quarter of an inch thick, somewhat after the manner of preparing a pie crust, and this is thrown upon, and pressed upon, the plaster pattern, and receives, of course, a correct indenta- tion, or outline of the design. The metal frame containing the plaster mould is divided horizontally, and after the surface is put in, the upper part of the frame is screwed on, and the maker fills up with clay of a somewhat coarser description, to form the tile of the requisite thickness. The tile is then put under a screw-press to impart the proper degree of solidity. 5. As far as we have gone, the tile is but of one colour; next comes the task of giving the different colours required. Suppose a tile be required of three colours red, blue, and buff. We will say the surface piece already put in is of abuff colour. The maker provides himself with vessels of a suitable kind, containing the one the blue, the other the red colour, in a ' ' slip" state, and these he pours into those parts of the indented surface that the drawing or finished tile before him tells him to be correct. These slips cover the surface entirely, and there is now not the slightest appearance of any pattern ART OF MAKING BRICKS AND TILES. 193 or design. After remaining in this state for three days, until the water has evaporated for the most part, the process of scraping or planing the surface commences, which is an operation requiring care, though easily effected by experienced hands. The pattern then makes its appearance, but the colours are scarcely distinguish- able the one from the other. 6. The tile is then finished as far as the maker is concerned; and, after remaining in the drying house from 14 to 21 days, according to circumstances, is con- veyed to the oven, where it is exposed to an intense degree of heat for about 60 hours. After being drawn from the oven, the tile is finished, except it be that the parties ordering wish the surface glazed, a rapid and easy process, the dipper merely placing the surface in a tub of glaze. 7. Plain self-coloured tiles, such as black, red, choco- late, buff, &c., and also tesserae, are made of the same material as the encaustic, only that it is dried longer in the kiln, passed through rollers to reduce it to a powder, and is then finely sifted. Presses of great power, made under Prosser's patent, make these tiles. The powdered clay is swept into a recess of the proper size, the screw descends, and, by its immense power, presses the powder into a solid tile, ready for drying and firing. One man can, with ease, make about 500 per day. 8. Tesserae. -^-The tesserae made by Messrs. Minton, under Mr. Prosser's patent, are now extensively used for mosaic pavements, for which they are admirably adapted. A few words will suffice to explain the nature of the improvements effected in this branch of art by the introduction ot the new material. The mosaic pavements made by the Romans were formed of small pieces of stone or marble of various K 194 RUDIMENTS OF THE colours, bedded one by one in a layer of cement, each of the pieces being levelled with the others as the work proceeded, and on the completion of the work the un- avoidable inequalities of surface were corrected by rubbing the whole to a plane surface. This mode of proceeding was attended with many defects. The irregular shapes of the tesserae caused the cement joints to be of a thickness that greatly in- jured the effect of the design, whilst the piecemeal way in which the work was laid rendered it very difficult to produce a level surface. It is not our purpose here to detail the several at- tempts that have been made during the last few years, with various degrees of success, to produce mosaic pave- ments, by the use of clay tesserae, coloured cements, &c. ; but it will readily be understood that the principal difficulties to be overcome in the use of solid tesserae are those arising from irregularity in the shape and size of the several pieces, as well as the great labour and expense attending the laying of such pavements piece by piece. These difficulties have been entirely overcome by the use of the patent tesserae, which, being made in steel dies, by the process above described, are perfectly uni- form in size, and fit closely together, with an almost imperceptible joint. The mode in which the tesserae are used is precisely the reverse of the Roman process, and is as follows : a coloured design of the intended mosaic having been drawn to scale, after the fashion of a Berlin wool pattern, the pattern is set out full size on a cement floor, perfectly smooth and level, and on this floor the tesserae are placed close together, the workmen being guided in the arrangement of the colours by the small drawing. ART OF MAKING BRICKS AND TILES. 195 The pieces are then joined together by a layer of cement applied to the upper surface, and in this way they are formed into slabs of convenient size, which, when hard, are ready for use, and can be laid with as much ease as ordinary flagstones. It will at once be under- stood, that the side of the slabs which is next the floor during the process of manufacture forms the upper side of the finished pavement, the pattern appearing reversed during its formation. CHAPTER VIII. ON THE MANUFACTURE OF BRICKS AND DRAIN PIPES BY MACHINERY. Ii is the general opinion that brickmaking by ma- chinery is not economical in small work, since the cost of moulding bears so small a proportion to the total cost. In large engineering works, however, where a contractor requires many millions of bricks in a limited time, for the construction of a tunnel or viaduct, the use of machinery may be desirable. In this chapter we do not, of course, pretend to give descriptions of the various patented and other machines connected with the manu- facture of bricks and tiles. Our object, in a work of this kind, being to deal with the principles of the art rather than with a multiplicity of minute details. We may, however, in order to show the great vitality of the trade, quote a few titles of inventions, &c., belonging to the years 1861 and 1862. The patent list displays the strong tendency to invention for making bricks, See., by machinery. Thus, we have K 2 196 RUDIMENTS OF THE Wimball's patent for making bricks,, tiles, and drain pipes. Morrell and Chamley's apparatus for making bricks, tiles, and other articles from plastic materials. Green and Wright's machinery for the manufacture of plain and ornamental bricks, slabs, tiles, and quarries. Basford's patent for constructing brick walls, and ornamenting the materials to be used for the same. Effertz' machinery for making bricks, tiles, &c. Grimshaw's patent for compressing brick-earth and other materials. Morris and Radford's patent for the manufacture of fire bricks, blocks, &c. Poolers patent for making ornamental bricks, tiles, &c Newton's machine for making bricks. Sharp and Balmer^s apparatus for the manufacture and drying of bricks. Grimshaw's patent apparatus, used in drying, pul- verising, and compressing clay. Platt and Richardson's apparatus for making bricks. Foster's method of rendering bricks impervious to damp. Smith's patent apparatus for the manufacture o bricks, tiles, &c. The following description of Oates's brickmaking machine is from Tomlinson's " Cyclopaedia of Usefu Arts, &c." It was described by Mr. J. E. Clift, o Birmingham, at a meeting of the Institution of Me- chanical Engineers, in November, 1859, and the descrip- tion is printed in the " Proceedings" of that body, anc is illustrated by four engraved plates, from which Mr Tomlinson has compiled the illustrative figure. We do not give this machine as the best, since there are many other well-known machines of merit in use ; but we ART OP MAKING BRICKS AND TILES. 197 offer it as an example of the mechanical means adopted in this class of inventions. The present brickmaking machines at work are divided by Mr. Clift into two classes, viz., those that operate on the clay in a moist and plastic state, and those for which the material requires to be dried and ground previous to being moulded. In the former class, the plastic column of clay, having been formed into a continuous length by the operation of a screw, pugging blades, or rollers, is divided into bricks by means of wires moved across, either while the clay is at rest or while in motion, by the wires being moved obliquely at an angle to compensate for the speed at which the clay travels. This wire-cutting requires the clay to be soft, so that the bricks are but little harder than those made by hand, and require a similar drying before being placed in the kiln ; and aP f his renders the expense of manu- facture about the same as for hand-made bricks. In the second class of machines, the bricks are compressed in a dry state in the mould ; but the processes for drying the clay, and reducing it to a uniform powder, add to the cost of manufacture. Mr. Gates has got rid of both objections, viz., the difficulty respecting the previous preparation of the clay, and the subsequent drying of the bricks. In his machine the clay is used of such a degree of dryness as to allow of its being mixed up and macerated, and compressed into bricks by a single continuous action, the clay being formed into a continuous column and compressed into the moulds by the action of a revolving vertical screw. The clay requires, in general, no previous preparation beyond that given by the ordinary crushing rollers, and, in some cases, may be put into the machine direct from the pit, unless it contain stones, when it is passed through 198 RUDIMENTS OF THT? a pair of rollers. Figs. 2 and 3, when joined at the parts indicated by the dotted lines, form a longitudinal section of the machine, and fig. 1 is a plan of the screw. Fig. 1. The cast-iron clay cylinder A is expanded at the upper part to form a hopper, into which the clay is supplied, and the lower cylindrical portion is about the same in ART OF MAKING BRICKS AND TILES. 199 Fig. 3. diameter as the length of the brick mould F, at the bottom of the pressing chamber B. The vertical screw C is placed in the axis of the cylinder, and carried by 200 RUDIMENTS OF THE two bearings in the upper frame D ; this screw is parallel at the lower part, the blade nearly filling the parallel portion of the clay cylinder, and is tapered conically at the upper part to nearly double the diameter. When the clay is thrown loosely into the hopper it is divided and directed towards the centre by the curved arm E revolving with the screw shaft, and drawn down by the tapered portion of the screw into the parallel part of the clay cylinder in sufficient quantity to keep this part of the cylinder constantly charged. The clay is then forced downwards by the parallel portion of the screw into the pressing chamber B, and into the brick mould F, which consists of a parallel block equal in thickness to a brick, and sliding between fixed plates above and below, and containing two moulds, F and G, corresponding in length and breadth to the bricks to be made. The mould-block F is made to slide with a reci- procating motion by means of the revolving cam H, which acts upon two rollers in the frame I, connected to the mould-block by a rod sliding through fixed eyes; and the two brick moulds are thus placed alternately under the opening of the pressing chamber B to receive a charge of clay, the mould-block remaining stationary in each position during one quarter of the revolution of the cam H. When the brick mould F is withdrawn from under the pressing chamber, the brick is dis- charged from the mould by the descent of the piston K, which is of the same dimensions as the brick mould; the piston is pressed down by the lever M, worked by the cam N, when the brick mould stops at the end of its stroke, and is drawn up again before the return motion of the mould begins. A second piston L acts in the same manner upon the second brick mould G, and the discharged bricks are received upon endless bands ART OP MAKING BHICKS AND TILES. 201 O, by which they are brought successively to the fronl of the machine, when they are removed by boys to the barrows used for conveying them to the kilns to be burnt. The solid block that divides the two brick moulds F and G is slightly wider than the discharge opening at the bottom of the pressing chamber B, having an over-lap, so that the making of one brick is terminated before that of the next begins, in order to ensure com- pleteness in the moulding. During the instant when this plank is passing the opening at the bottom of the pressing chamber, the discharge of the clay is stopped, and it becomes necessary to provide some means eithei of relieving the pressure during that period, or of stop- ping the motion of the pressing screw. Accordingly the pressure is relieved by an ingenious contrivance, forming in effect a safety-valve, which prevents the pressure in the chamber from increasing when the brick mould is shut off, and also serves to maintain a uniform pressure during the formation of the brick, so as to en- sure each mould being thoroughly and equally filled with clay; this is effected by an escape -pipe P, similar in form to the brick mould, but extending horizontally from the side of the pressing chamber, and is open at *he outer extremity. The regular action of the screw forces the clay into the escape-pipe, as far as its outer extremity, forming a parallel bar of clay in the pipe. The resistance caused by the friction of this bar in sliding through the pipe is then the measure of the amount of pressure in the machine ; and this pressure cannot be exceeded in the machine, for the instant that the brick mould is full, the further supply of clay, fed into the pressing chamber by the continuous motion of the screw, escapes laterally, by pushing outwards the column of clay in the escape-pipe. The uniform pres- K 3 202 RUDIMENTS OF THE sure of every brick in the mould up to this fixed limit is ensured by the escape-pipe not beginning to act until that limit of pressure is reached. Its action is similar to that of a safety-valve, and the amount of pressure under which the bricks are made is directly regulated by adjusting the length of the escape-pipe. The latter discharges a continuous bar of solid clay, advancing by intermittent steps of to in. in length, each time that the brick mould is shut off and changed. The projecting piece of clay from the end of the escape-pipe is broken off from time to time, and thrown back into the hopper of the machine. The upper side of the solid block separating the two moulds F and G is faced with steel: and the upper face of the brick is smoothed by being sheared off by the edge of the opening in the pressing chamber ; the under face of the brick is smoothed by being planed by a steel bar R, fixed along the edge of the under plate, and having a groove in it for discharging the shaving of clay taken off the brick. The screw shaft is driven by bevil gear from the shaft S, which is driven by a strap from the engine, the speed being adjusted according to the quality of the clay or the wear of the screw. The screw is driven at about thirty revolutions per minute, when at full speed, or one brick for each revolution of the screw. The machine completes 12,000 bricks per day, or an average of twenty per minute. The clay, as already stated, can be taken direct from the pit, passed through crushing rollers, and then fed straight into the moulding machine. Indeed, the clay within a quarter of an hour after being brought from the pit may be seen stacked in kilns, and in a few days burnt ready for use. The amount of power required for driving the machine, and the wear ART OF MAKING BRICKS AND TILES. 203 of the screw, vary according to the material worked. With a calcareous marl about twelve horse-power was found sufficient. When the material is very siliceous the cast-iron screws wear out quickly. Gun-metal has been found much more durable than iron for the screw and mould-block. In burning bricks that contain much alumina, and consequently retain a good deal of moisture, it is found advisable to stack the bricks in the kiln in lifts of from fifteen to twenty courses each. As soon as the bottom lift has been stacked, small fires are lighted to drive off the steam from the bricks, which might otherwise soften those stacked above ; the middle lift is then stacked and similarly dried, and then the top lift; after which the full fires are lighted. The crushing strength of these bricks made in the machines at Oldbury is said to be double that of the hand-made blue bricks of the neighbour hood , being an average of 150 tons compared with 76 tons, or 8,024 Ibs. per square inch compared with 4,203 Ibs. The trans- verse strength, with 7 in. length between the bearings, was found to be, for hand-made bricks, 2,350 lbs. r for machine-made bricks, 3,085 Ibs., and for the same, hard burnt, 4,320 Ibs. One of the advantages of this machine is, that clay containing a good deal of stone, which could scarcely be worked for hand-made bricks, can be used. Tfo> brick-earth at Cobham is very unfavourable for brick- making, it being so weak and friable that hand -made bricks made from it were crushed by a moderate pres- sure; when made by the machine, however, serviceable bricks were turned out. A material containing 84 per cent, of silica has been made by this machine into bricks. The bricks had not any hollow or frog in the 201 RUDIMENTS OF THE upper space for holding the mortar, but arrangement? were being made for producing it. The extent to which bricks absorb water is im- portant, since dry houses cannot be built with bricks that are very absorbent. A brick of 9 Ibs. weight will absorb about 1 Ib. of water, and it is stated that the bricks made by this machine absorb less. The cost of Oates's machine is from 150 to 200, exclusive of the engine for driving it. The cost of brick- making varies according to the price of coal in different localities ; but there is very little variation in the price of the unburnt bricks made by the machine, the differ- ence arising chiefly from the varying amount of royalty charged on the clay in the pit, which varies from Is. to 2s. 6d. per 1,000. A machine at Cobham, employed by Messrs. Peto and Betts, produced 200,000 bricks in a fortnight of eleven days, but the average number per week, of five and a half days, was considered to be 80,000, or at the rate of twenty-four bricks per minute. The contract for the bricks in and out of the kilns, exclusive of the cost of the coals, was first taken at 5s. 9d. per 1,000 bricks ; which was afterwards raised to 6s. 9d., owing to the distance of the clay from the machine. To this had to be added 6d. per 1,000 royalty, and the wages of the engine-driver at 6d. per 1,000, raising the expenses to 7s. 9d. per 1,000 bricks. The quantity of coals required for burning the bricks, and for the engine driving, might safely be taken at ^ ton per 1,000 ; and the price of coal at that place being 25s. per ton, the total cost of making the bricks by the ma- chine amounted to 20s. per 1,000, including the burning. The following particulars respecting drain-pipe mak- ing machines^ and hollow bricks, are also from Mi. Tomlinson's " Cyclopaedia." ART OF MAKING BRICKS AND TILES. 205 Fig. 4. The large and increasing demand for draining tiles and pipes has led to great economy in their manufac- ture. Some are moulded flat, and afterwards bent round a wooden core to the proper shape : others are made at once of a curved form by forcing the clay through a dod or mould, fig. 4, by mechanical pressure. The action will be readily under- stood from fig. 5, which repre- sents a section of a strong iron cylinder, containing a quantity of clay in the act of being pressed down with enormous force by a solid piston or plunger. The clay, as it escapes through the dod, is evidently moulded into the form of the pipe (also shown in section), which is cut off in lengths, by means of a wire, and these, after a preliminary drying, Fiff.5. are ready for firing. By using dods of different sizes, pipes of various magnitudes are formed. Fig. 6 is an elevation of a drain-pipe making machine, which we have copied from Mr. Green's works at Lambeth. The cylinder contains a second cylinder, capable of holding a given weight of clay, adapted to the moulding of a certain number of pipes at one charge. Thus, one box-full will furnish five 9-in. pipes, six 6-in. pipes, seven 4-in. pipes, and so on. By the action of the rack the piston forces the clay through the dod or die upon a table, so balanced by weights that the lengthening pipe is sufficient by its weight to force down the table, and when a certain ?.ength of pipe 206 RUDIMENTS OF THE is formed,, the boy stops the machine by shifting the strap which drives the rack-screw from the fast to the loose pulley, and then cuts off the length of pipe with Fig. 6. a wire, removes the pipe so formed, raises up the table, sets the machine in action, and receives a pipe upon the ART OF MAKING BRICKS AND TILES. 207 table as before. When all the clay is thus forced out of the cylinder, the action of the rack is reversed, whereby the plunger is drawn up out of the cylinder. The cylinder, which moves on a kind of hinge, is then tilted on one side to receive its charge of clay, and being restored to its vertical position, the action proceeds as before. By an ingenious contrivance, the fork which shifts the strap from the fast to the loose pulley, is weighted in such a manner that, when the boy raises his foot from a treadle, the strap is at once moved on to the loose pulley, and vice versa, thus giving the attendant a third hand, and diminishing the chances of danger from the strap. Mr. Green has a machine worked by a screw, in which the process is continuous. These pipes are washed with glaze before the firing, as will de explained hereafter. f_>y means of a tile machine, the hollow bricks are formed, which are so much recommended by the " So- ciety for Improving the Condition of the Labouring Classes/' and introduced by them in the construction of dwelling-houses for the poor. The idea of tubular bricks is not new, for such articles were used by the Romans in large vaultings, where lightness of construc- tion was required, and they are said to be in common use in Tunis at the present time. The size of the bricks is 12 in. long, and three courses rise 1 ft. in height. Nine hollow bricks will do as much walling as sixteen of the common sort, with only a slight increase in weight. In passing through the tile machine, or in the process of drying, the bricks can be splayed at the ends for gables, or marked for closures, and broken off as required in use, or they may be perforated for the purpose of venti- lation. If nicked with a sharp-pointed hammer, they will break off at any desired line ; and the angles may 208 RUDIMENTS OF TUT? be taken off with a trowel as in the common brick. The bricks for the quoins and jambs may be made solid or perforated, and with perpendicular holes, either cir- cular, square, or octagonal : those in the quoins may be so arranged as to serve for ventilating shafts. The hollow bricks, from their mode of manufacture, are more compressed than common bricks, require less drying, and are better burned with less fuel. The following figures represent some of the forms of hollow bricks in common use. a, fig. 7, is an external brick, 11 1 in. long, which with the quoin brick e, and the jamb brick b, are sufficient for building 9-in. walls, e is 10J in. long, with one splayed corner for forming external angles, reveals, and jambs of doors and windows, either square or splayed. The internal jamb and chimney brick, b } is 8| in. long ; c is an internal brick, adapted to any thickness of wall beyond 9 in. : d is for 5|-in. partitions, or internal walls, and arch bricks, and is used for floor and roof arches of 7 to 10 ft. span. / is used for the same purpose, with ART OF MAKING BRICKS AND TILES. 209 a webb to give extra strength, and to adapt them for using on edges in partitions,, 3| in. thick to rise in 6-in. courses. Fig. 8 represents a specimen of hollow brick work in 6-in. courses, with square rebated joints for extra strength. These bricks are adapted to the lining of flint or concrete walls. Fig. 9 is a section illustrative of the construction adopted in H. R. H. Prince Albert's model houses. The span of the arches is increased over the living rooms to 10 ft. 4 in., with a proportionate addition to their rise. The external springers are of cast-iron, connected by wrought-irori tie rods. It is stated that there is an advantage of 29 per cent. in favour of the patent bonded hollow bricks over ordi- nary bricks, in addition to a considerable diminution in the cost of carriage or transport, and of 25 per cent, on the mortar and the labour. 210 RUPIMENTS OF CHAPTER IX. ADDITIONAL REMARKS ON THE MANUFACTURE OF BRICKS BY MACHINERY, IT is proposed here to supplement the previous chapter, written by Professor Tomlinson in 1863, by giving full descriptions of some of the most remarkable, or most used, of the very many brickmaking machines now before the public. The trade in producing brick machinery itself has come to be a very large one, in which great intelligence, energy, and capital have been invested, and from which have emanated an immense number of inventions, chiefly the subjects of patents. The results have naturally been much rivalry and com- petition, so that, perhaps, there is no one of the trains of machinery for making brick, which has had a success enough to make it worth notice, which has not been ex- posed to partial advocacy, and to equally interested and frequently more unjust depreciation. It would be highly out of place that "an outline" such as this volume can alone pretend to, within its limits, should undertake to appraise the relative merits or demerits of the various machines we are about to notice the rather, as we are unable to treat the whole sub- ject in the exhaustive manner that alone would justify such criticism. The following notices, therefore, must be viewed as merely collecting before the reader, with sufficient illustrations, a few of the more prominent brick and tile machines, or those most in use in Great ART OF MAKING BRICKS AND TILES. 2 Britain, sufficient to serve as an index to those specially interested, whereby more complete information may be obtained through the respective makers or otherwise. As has been sufficiently shown in the preceding parts of this volume, the natural clays from which bricks are to be made, though they may occasionally be found in a state capable of being at once made into brick, must most usually be subjected, after having been dug out, to more or less disintegration, grinding, and mixing into perfect plasticity, before being em- ployed. For these purposes, the screen sometimes being used beforehand, the crushing rollers and the pug-mill are employed. Other methods of pro- ducing perfect freedom from adventitious matter and perfect plasticity are occasionally employed, when special qualities of extra fine bricks are sought for, but with those we need not trouble the reader here. The above machines are employed in combination, i.e., as parts of one compound machine, as produced by some makers, separately as turned out by others. The clay-mill, with crushing rollers working on edge in a circular pan, is also in use. Brick machinery itself, since the invention of Prosser, many years since, is divisible into two great classes, wet and dry clay ma- chines, i.e., machines which form the brick, by moderate pressure in moulds, from already tempered and plastic clay, and those which, under a far more severe com- pression, mould the bricks from clay perfectly commi- nuted, but either dry, or at most only very slightly moistened. One of the most salient advantages of the dry method is, that it produces a denser brick, and one that shrinks less both in drying and in baking than do those made wet ; and that a certain amount, though not a very great one, of the labour and cost of the 212 RUDIMENTS OF THE preliminary preparation of the clay is saved. The disadvantages, or some of them, are, that unless the clay in the dry or merely damp state be scrupulously well prepared, and unless a degree of pressure be employed which demands a good deal of power, the brick may be deficient in tenacity and in uniform solidity, or even in perfect fairness of face. On the other hand, with certain clays, and pressures beyond a given point, bricks are thus produced, which, though dense and resistant, have so ^porous a surface as hardly to take bond with either cement or mortar. Fig. 1 represents Whitehead's Improved Clay Crush- ing and Grinding Boiler Mill, consisting of two pairs of large iron rollers, fitted in a massive cast-iron frame. The dimensions of the top rollers (which revolve at equal speed) are 2 ft. 6 in. long by 1 ft. 8 in. diameter. The lower pair (running as two to one, for more thoroughly incorporating the clay) are 2 ft. 6 in. long by 1 ft. 6 in. ART OF MAKING BRICKS AND TILES. 213 diameter. The above mill is constructed for the pur- pose of reducing rough strong clays or hard marls not disintegrate by water, into a state to be rendered plastic by future operations in the pug-mill, of which two dif- r. 2. ferent examples are given in figs. 2 and 3 by the same maker. Fig. 2 is a large and powerful pug-mill. The cylinder is one strong loam casting made perfectly true ; it is erected upon a massive iron basement, and provided with two cast mouth-pieces for the discharge of the pugged clay, one situate on each side at bottom. These mouth-pieces may have sliding doors fitted, to increase or diminish the area of the orifice, so as to cause the clay to be more or less finely ground. This is valuable in admitting the adaptation of the mill to the pressing out of large and small pipes, &c. This mill makes about three revolutions per minute, worked by the power of one horse, The cylinder is 24 in. 214 RUDIMENTS OF THE diameter inside, and 54 in. high ; the total height to top of vertical shaft is 87 in. Fig. 3 represents Whitehead's Perforated Pug-mill. The advantage of this mill is, that during the opera- tion of pugging the clay is forced out through the perforations at the sides in the plastic state, leaving behind the stones, which are carried, by means of the internal arrangement of the knives on the vertical shaft, through an aperture at the bottom; thus combining the process of pugging and screening in one operation. We entertain some doubts of the advantages of this machine, however ingenious ; for screening as a pre- liminary operation should, whenever practicable, never be omitted. Fig. 4 shows a very good form of nearly portable ART OF MAKING BRICKS AND TILES. 215 clay-mill. Mills in this form may be used for grinding wet or plastic clay, but are more suitable for indurated dry clays, which, are to be used with one or other of the dry-clay brick machines. The pan, as is evident from the figure, revolves, and the runners are carried round by it, being free to move within a certain range verti- cally. The pan is provided with curved blades, so fixed as to keep the stuff constantly beneath the runners. We now come to the composite machines, in which crushing rollers and horizontal pug-mill are combined, as in fig. 5. For very hard clays, such as fire-clays for fire-brick, two or even more pairs of crushing rollers may be needed above each other, those closest set being at bottom. 216 ART OF MAKING BRICKS AND TILES. The rollers are driven at different speeds, so as to produce a rub as well as a mere squeeze between the sur- Fiy.6. faces, and so better disintegrate the clay. The rollers are usually made about 20 in. diameter, and about 3 ft. long. They are fed by hand, through a hopper at top. Having thus described the machinery generally in use for the preparation of the clay, whether plastic or dry, we proceed to illustrate a few of the brickmaking machines themselves, commencing with those for operat- ing on moist or plastic clays. Fig. 6 represents a large machine as constructed by Whitehead, of Preston, in which the rough clay thrown in between the rollers at top is ground, and then passes 218 RUDIMENTS OF THE at once into the vertical pug-mill, and is thence expressed in two continuous prisms of the size in section of a brick Fig. 7. on flat, and which are at intervals cut transversely into bricks by the wires of the frames, seen in the front of the drawing. These are moved by hand. Fig. 8 represents another form of machine, in which the clay, already tempered, is drawn in and con- tinuously expressed by a pair of rollers, the prism being cut asunder into bricks by the radial wires forming the arms of the wheel C, which is moved auto- matically. An extremely simply-contrived and most efficient French machine of this class was exhibited in 1862 in the French department. It was an invention of M. Jardin, and manufactured by Cazenave & Co., Paris. At work in the Exhibition, it made at the rate of twelve thousand per day of ten hours, with only the attendance of two men. The division of the prism of clay was effected by wires attached to a wheel moved by ART OF MAKING BRICKS AND TILES. 219 the machine, but differently arranged from that of fig. 8. The following machine belongs to this same class. It is Clayton and Co/s second- sized horizontal brick L2 ART OF MAKING BRICKS AND TILES. 221 machine, which combines the crushing rollers, pug- mill, and brick-forming in one machine. These machines are largely run upon, and have been employed extensively by our great contractors, and upon many public works facts which give the best assurance that they answer well. One of these machines weighs about 3J- tons, and of this second size, with about 8 or 10 horse power, will turn out from 75,000 to 90,000 bricks per week. We now come to another class of machines working Fig. 10. \vith plastic clay, though capable of employing clay nearly dry, or at least very stiffly tempered. The machine shown in fig. 10 consists of a vertical pug-mill, into the upper part of which the clay is fed, and in which it undergoes tempering and mixing, and, on 222 RUDIMENTS OF THE reaching the bottom of the mill, is pressed into the moulds, of the form and size of brick required, which are arranged in the form of a circular revolving table. As this table revolves, the piston-rods of the moulds ascend an inclined spiral plane, and so gradually lift the bricks out of the moulds, whence they are taken from the machine by a boy, and placed on an endless band which carries the bricks direct to the " waller." The speed of the several parts is so arranged, that the operations of pugging, moulding, and delivery proceed simultane- ously in due order, the whole being easily driven by a steam engine of about 6-horse power, which, at the ordinary rate of working, will make 12,000 bricks per day ; or with 8-horse power from 15,000 to 18,000. In consequence of the great pressure to which the clay is subjected in the moulds, the bricks produced by this machine may be made from stiffer clay, so that less nrater has to be evaporated in the drying, thus saving much of the time required for hand-made bricks, and avoiding the risk of loss from bad weather. One point of importance to remark as respects this last class of machines, compared with the previous one, is this wire-cut bricks are smooth and perfect in form, provided the clay be not only perfectly plastic, but per- fectly uniform and free from adventitious particles. If, however, the plastic clay contains gravelly par- ticles, or be of such a quality that it is necessary to mix it with ashes or '' breeze/' then the section made by the passage of the wire drags out and after it more or less of these solid particles, and the faces of section are rough and uneven ; in such cases resort is best had to those machines of pressure only. In the following brick-pressing machine also, for plastic clay, the moulded bricks are delivered by the ART OF MAKING BRICKS AND TILES. 223 machine directly on to the horizontal belt that carries them away ; so that the labour of attendance is nearly limited to feeding the tempered clay into the top hopper. "We are not aware to what extent as yet this ingenious machine has been employed. Figs. 11, 12, 13, and 14 illustrate a brick-pressing machine recently patented by Mr. W. Longley, of Leeds. The invention relates to an arrangement of brick- moulding machinery, whereby bricks are produced from "wet" clay, having great solidity, with a smooth ex- terior, and containing a less amount of moisture than those produced by hand, or by machinery at present in use. Fig 11 is a side elevation of the machine; fig. 12 is a partial end elevation, showing in longitudinal section the cylinder which carries the moulds, and presents them successively to a conical hopper to be fed with clay ; fig. 13 is a cross section of the mould- cylinder, showing its connection with the hopper ; and fig. 14 shows the means used for locking the cylinder, so as to keep the moulds stationary while being filled and discharged. A A is the main framing of the machine, upon which is mounted in suitable bearings a horizontal cylinder B. This cylinder is cast with open ends, and it is fitted near the middle of its length with a series of four moulds, C 0, arranged radially around it. These moulds are formed by recesses cut through the periphery of a projecting band a a, that surrounds the cylinder, having their ends closed by the rings b b (bolted to the cylin- der) : a series of close chambers, D D, are formed in a similar manner between the moulds for receiving steam for heating the latter. Immediately above this con- centric projection of the cylinder B, and in close prox- imity thereto, is situate the hopper E, in which a screw AHT OF MAKING BRICKS AND TILES. 225 is mounted for forcing down the clay into the moulds as they are presented to the former. Fitted into the moulds are plungers, F, the stems of which project through the inner periphery of the cylinder B, and are intended for discharging the bricks from the moulds ; the inner periphery of the cylinder B is also pierced to receive the ends of a cruciform arrangement of steam pipes, G- (fig. 13), for supplying steam from a central pipe running in the direction of the axis of the cylin- der to the chambers D ; an intermittent axial motion is given to the cylinder, for the purpose of bringing the moulds severally under the hopper to be filled, and subsequently under the action of a plunger the clay thus filled into the mould presented to it is compressed therein. When this is effected, and the cam in its revolution has passed out of action, the weighted crank lever draws back the plunger N out of the mould. An- other movement of the cylinder B now takes place, and the compressed brick is brought down to the position for being discharged on to an endless apron 0. This is effected by the stem of the plunger, F, of the mould, being pressed upon at its rear end by the rocking lever H. This rocking lever is mounted on a bent bracket arm attached to the main framing, and it is provided with a roller, which bears upon a rocking cam having a stud pin on the framing for its fulcrum. This rocking cam is jointed to a rod, which connects it with a rocking arm, pendent from a bracket on the framing. The arm carries a roller which bears against a cam on the cam shaft ; the revolution therefore of the cam shaft gives a reciprocating motion to the cam H, thus causing it to rock the lever H, and depress the plunger that has been brought beneath its inner end. This depression of the plunger effects the discharge of the brick, which L3 226 RUDIMENTS OF THE is facilitated by the heating of the moulds through tLe admission of steam as before explained. To prevent the adherence of the clay to the compressing plunger, that is made hollow, and steam is conveyed into it by an arrangement of jointed steam pipes, as shown at fig. 1 1 . The discharged brick is received on to an endless apron, 0, which receives motion from the spur wheel on the cylinder B, gearing into a spur wheel on the axle of one of the carrying rollers of the apron. The cylinder B is also furnished with a ring, in the periphery of which are four notches, corresponding with the moulds. These notches (see fig. 14) are for the purpose of receiving the taper end of a locking bar P, which, when it is desired temporarily to lock the cylinder (as at the moment of filling, pressing, and discharging the moulds), is thrust forward by a cam on the cam shaft pressing upon a roller, mounted on the end of the locking bar, which slides in guides provided to receive it. The release of the cylinder is effected by throwing back the locking bar by means of a weighted crank arm, as in the case of the compressing plunger. This machine (fig. 15), the subject of a patent, is made by Whitehead, of Preston ; it works upon tem- pered clay also. The merits claimed for it consist in simplicity of construction and efficient performance. The junk of clay or brick may be previously moulded as for other pressing machines, but with this machine it is not absolutely necessary to previously mould the lump, if only sufficient clay be supplied to make a brick, and be simply placed in front of the piston ; it then is forced into the mould or die (of which there are four on a revolving shaft) of the desired size, and any superfluous bulk of the clay is cut off, thus making all the bricks ART OF MAKING BRICKS AND TILES. 227 perfectly true and of uniform dimensions. During the return of the piston the box of dies or moulds resolves one-fourth of the way round, thus bringing another empty mould, which has already been oiled and cleaned by a self-acting lubricator, directly opposite the piston, Fig. 15. to receive the next brick. In the meantime, a self- acting push-plate forces the brick, already pressed, out of the die upon a self-acting table prepared for carry- ing it away. The following well-arranged machine belongs to the class which can operate upon either plastic or dry clay, but which is, in our opinion, best adapted to the former. The makers and patentees, Messrs. Bradley and Craven, of Wakefield, have had a large experience in machinery of this sort. Simplicity of parts and strength are the main cha- racteristics of this machine. If the material be coarse or strong, it must be crushed RUDIMENTS OF THE before being passed into the hopper, into which it may be delivered either with or without water. Two moulds receive the charge of clay at once. While these are being filled, the two that had been Fig. 16. just before filled are being subjected to a considerable pressure, and the two bricks that had just previously to that been so pressed are in process of delivery, out of the moulds and on to a flat belt which takes them away. For the production of smooth, well-squared facing bricks this machine works extremely well. We now arrive at the last class, namely, of ma- chines intended specially to operate upon dry clay, or nearly dry clay. Amongst these we may notice the patent machine of Hersey and Walsh, which has been recommended by a ART OF MAKING BRICKS AND TILES. 229 competent authority Mr. Humphrey Chamberlain, Consulting Pottery Engineer, formerly of Kempsey, near Worcester. This machine is stated to have been an American invention, which attracted attention from the simplicity of its movements and the enormous power it was capa- ble of exerting with a small amount of friction. It was found working successfully in the United States, and arrangements made for its introduction in this country. It produces an excellent article, and works satisfactorily here also. Some few alterations had to be made to adapt it to English- sized bricks, as American bricks are little more than one-third the cubical contents of the English. The weight of these machines is about 25 tons, which is necessary to withstand the enormous pressure they are capable of exerting. They are made with any number of moulds from 2 to 8. With 6 moulds, and driven by a 6-horse engine, to deliver 24 bricks per minute, one machine is capable of giving 330 tons pressure on the 6 bricks ; and if worked by a more powerful engine, the pressure can be increased, only limited by the strength of the machine. As few clays require more than 20 or 30 tons on a brick, from 4 to 5 horse power is ample. The motions of this machine are performed by a pair of cam wheels, the pressure being communicated by a pair of rollers running on the cams, with the mould pistons fixed on the shaft between them. The moulds are raised and lowered by the same cams. The bricks are delivered and the moulds re-fed with dry clay from the hopper by a feeder worked by friction. The ma- chine, after pressing 6 bricks, delivers them on a board ready for removal, so that they go direct to the kilns without being handled or injured. The whole machine 230 RUDIMENTS OF THE is fixed on one bed-plate, and is made of such strength as not to be likely to get out of order. The following machine will afford a sufficiently clear notion of the construction, or at least the general prin- ciples of construction, of the great majority of dry- clay brick-machines which have been brought into successful action. Fig. 17 represents the dry-clay brickmaking ma- 2%. 17. chine, of which Messrs. Bradley and Craven, of Wake- field, are the inventors and patentees. One of the disadvantages or difficulties of making per- fectly sound and solid bricks from completely dry clay, however finely pulverised, is that the air lodged in the interstices of the clay dust is sometimes not easily and completely expelled by a single compression, but lodges in one or more irregular cavities into which it has col- lected, and so leaves the brick hollow. One of the main objects of this machine is to obviate that evil, ART OF MAKING BRICKS AND TILES. 231 which is proposed being accomplished by its possessing the power of relieving each brick from pressure, and again applying it, so as gradually to force out the air, and finally consolidate the brick, and that to an extent that a single pressure, though greater, and hence exerting a greater strain on the machine, might not accomplish. The patentees state : " By this machine two or three distinct pressures can be given to each brick. If two pressures (that is, upward and downward) are sufficient to produce a good article from the clay, then the ma- chine makes two bricks at a stroke, or for every revolu- tion one brick by each eccentric. If the clay is of such a character that the whole of the air cannot be expelled, or the dust sufficiently condensed to make a perfect brick by two pressures, then a third is given by carry- ing the brick round under the second eccentric. With most clays two pressures will be found sufficient. It is only necessary to test a little of the clay to be worked so that the machine may be adjusted to mould and press from any kind of earth equally good bricks. The only change for giving three pressures is, to adjust the machine to run faster, and change the inclined plane for giving the upward or first pressure, and delivering the bricks. The action of the machine is easily understood. The clay being delivered by an elevator from the crushing rollers into the hopper of the machine in motion, the tappet wheel turns the mould table the length of one mould. This action delivers two empty moulds under the hoppers to receive clay, delivers two bricks to the attendant, and gives a powerful upward pressure to the clay received in the moulds that have just left the hoppers. The table is then for a moment stationary, while the two eccentrics give 232 P.UD1MENTS OF THE the final strain on two bricks. When the eccentric pistons are clear of the moulds the tappet again turns the table one brick's length, and the same action is renewed. During the time the eccentrics are giving pressure, the table is held firmly by a stop, which w then released." The last of this class which we shall notice is the dry-clay machine of Wilson, of Campbellfield Brick- works, Glasgow, which was exhibited in action at the Exhibition of 1862. The peculiarity of working of this machine is, that the dry and pulverised clay prepared for being made into brick is carried along automatically to the hopper, and, just before being delivered into it, is subjected to being blown upon by the waste steam discharged from the non-condensing engine which drives the machine. The result is a slight condensation of steam on and in the pores of the clay, and a slight warming of the clay itself. From this arises a much-increased tendency to rapid and perfect agglutination in the clay when sub- mitted to pressure in this state, between wet and dry, and a much readier expulsion of the air involved in the mass. There is not the slightest doubt of the great advantage derived from this very simple mode of treating the dry clay prior to compression. There are several contrivances in Mr. Wilson's ma- chine, as to details, also of value, especially one by which the maximum pressure possible is so regu- lated that the destruction of the machine is guarded against. One great improvement yet remains to be made to render perfect dry-clay brickmaking machines, namely, to adapt to them the same method that was employed by Mr. Brockedon, in his patent for compressing dry ART OF MAKING BRICKS AND TILES. 233 powder of plumbago into a dense and solid block to be sawed into pencils, namely, the operating the compres- sion in a vacuum, so that the air involved between the particles of dry clay (or dust, if quite dry) being thus extracted, the mechanical pressure is free to act fully and solely in producing condensation and agglutination of the clay particles. Any one of the brick machines of the first class, down to fig. 8, inclusive, may, by a suitable alteration of the discharging dies and receiving tables, be made to express and form perforated bricks, moulded bricks, drain or other pipes, or tiles of any sort, as in Fig. 7. We shall therefore confine our illustrations of tile- making machinery, specially so designed, to two exam- ples, viz., to fig. 18, the large drain-pipe machine of Fig. IS. Page and Co., of Bedford, which forces out a con- tinuous hollow cylinder from the plastic clay (as at A, fig. 19), and fig. 19. 234 RUDIMENTS OF THE The machine by Whitehead, of Preston, for pressing one end of the cylinder so cut off to a given length, as at A, into the socket form, as at B, fig. 19, so that the lengths shall go together with spigot and faucet joints. Dies of various forms, prepared to adapt to any of the brick or tile machinery, are supplied by the makers, ART OF MAKING BRICKS AND TILES. 235 by which almost any form (solid or hollow, tubular or multitubular, i.e., perforated like "perforated brick"), that can be produced by the advance of a given section parallel to itself, may be formed. The figures in Fig 7 show a few of the more usually employed sections those at the right being drain-pipes, those in the middle for building purposes, and the left-hand ones for roof- ing use. In addition to the machines for brick and tile making, which we have thus pretty copiously illustrated, there are other machines almost innumerable for making special forms in plastic or in dry clay, referable to the great family of bricks and tiles. A great tribe of these machines, to which our space forbids our making any allusion, is employed in Great Britain and abroad in the manufacture of encaustic, or inlaid, or intaglio tiles for flooring and other architectural purposes. Those who desire still more complete or enlarged infor- mation on the subject of this class of machinery should consult the Practical Mechanic's Journal Record of the Exhibition of 1862, Mr. D. K. Clarke's "Exhibited Machinery of 1862," the Reports of the Juries of Exhibition, 1862, and the volume of Abridgments of Patents, relating to drain tiles and pipes, bricks, tiles, and pottery, issued by the Patent Office, extending from 1619 to 1861. There have been many patents since that date, and many descriptions of machines of more or less value are also to be found scattered through the British and foreign mechanical journals, in encyclopaedia articles, &c. Though not important for those employ- ing brick machinery at home, it may be desirable, for the information of British colonists, that we should in- dicate the form of portable high-pressure steam en-gine most usually employed for actuating such. It is that 236 RUDIMENTS OF THE. shown in fig. 20, being one of this class of engines manufactured by Clayton and Shuttleworth. When bricks, &c., are required for a special contract or some private work presenting but a terminable demand, such Fig, 20. portable engines are the best and cheapest in everj way ; but, for a great and permanent brickmaking establishment, engines upon fixed bed-plates or founda- tions are to be preferred. In concluding these notices of the apparatus of the mechanical brick and tile maker, we must not omit to call the reader's attention to probably the greatest im- provement that has ever been made in the construction ART OF MAKING BRICKS AND TILES. 237 of kilns, for at once drying and burning brick, viz., the patent brick-kiln of Hoffmann. This kiln is, in fact, an admirable adaptation to brick drying and burning of Siemens's regenerative principle of furnace, as will be apparent from the following Fig. 22. account, abridged chiefly from a paper by Professor James Thomson, of Belfast. Fig. 21 is a half- plan on top of the kiln, the other being a horizontal section at 238 RUDIMENTS OF THE the level of the flues, leading into the central chimney- stalk, as seen in the vertical section, fig. 23. Fig. 22 is a diagram of the whole to a reduced scale, which is Jfy. 23. referred to in illustrating the description of the mode of working of the kiln. The accompanying engravings illustrate this remark- able form of kiln, invented by M. Hoffmann, of Berlin, but patented in England by Mr. H. Chamberlain, who supplies designs for their construction, &c. Some sixty of these kilns are already at work on the Continent and in Great Britain. The furnace or oven consists of a circular channel, O, of any section, which receives the objects to be fired, introduced through doors in the outside wall ; the fuel is fed in by apertures formed in the top of the arch. Flues lead from the bed of the ART OF MAKING BRICKS AND TILES. 239 furnace to the smoke- chamber K, which surrounds the base of the central chimney, the communication with which can be cut off when required by means of cast-iron bell-shaped covers. An intercepting damper can be lowered or placed in grooves built into the walls of the furnace immediately behind each flue, so as to separate it at any distinct or equidistant compartment. The fuel passes through apertures which are constructed in the arch, and falls through channels formed by the objects to be burnt to a chamber in the bed of the furnace, from which a certain number of small flues radiate to produce a frer current from fire to fire. In practice it is found bbtfter to divide the kiln into twelve chambers, to which there are twelve entries or doorways, and the same number of flues communicating with the smoke- chamber, and just as many openings in the arch for the reception of the large intercepting dampers thus the furnace can be divided at any one of the twelve parts. J?or clearer distinction, these compartments may be numbered, as in fig. 22, from 1 to 12, of which two, Nos. 12 and 1, we will suppose are separated by the intercepting damper. The objects to be burned may be bricks or tiles, &c. Suppose the fire in full operation the doors leading to the compartments 1 and 2 being open, No. 1 for filling it with fresh goods, and No. 2 for taking out those already burnt. The chambers Nos. 3, 4, 5, and 6, which are all filled with burned goods, are gradually cooling by the air entering through the doors of Nos. 1 and 2, and as it passes on through warmer and at last glowing ware, it will result that the kiln fires are supplied with atmospheric air almost as hot as the furnace itself. In chamber No. 7 the fire is burn- ing, and when its contents have reached the desired 240 RUDIMENTS OF THE temperature, No. 8 will have arrived at such a degree from the absorption of the waste heat, that the fuel introduced from the top is instantly inflamed. The compartments Nos. 9, 10, 11, and 12, will be dried off, and heated one after another by the waste heat which passes through and expends itself on the contents of these chambers, and on its arrival in No. 12, meeting with the obstruction of the large damper, it is conducted by the small flue to the chimney, with its temperature again so lowered that it will only just support the draught. No. 1 being now filled again, the damper between 12 and 1 is lifted and lowered be- tween 1 and 2. The bell damper above the mouth of the flue No. 12 is lowered, and that of No. 1 lifted. The doorway of No. 12 is then closed, and that of the compartment No. 3 opened, the contents of which will be sufficiently cooled to be taken out, while No. 2, which is empty, can be filled again. On the 5th of January, 1864, Professor J. Thomson, of Belfast, read a paper on the manufacture of bricks, before the Chemico- Agricultural Society of Ulster, in which he referred at considerable length to the Hoffmann oven. The following is an abstract of his paper : Having explained the chief methods in use for working the clay and forming it into bricks ready for the kiln, he then turned attention to the great loss of heat which occurs in the ordinary modes of burning bricks in com- mon kilns. This loss is twofold. First, during the burning of the bricks the air which has passed through the fuel, or among the heated bricks, and the smoke, including the gaseous products generally, passes away from the kiln to waste at a very high temperature, even at a red heat, during a considerable part of the process. Secondly, when the bricks are raised to the high tem- ART OF MAKING BRICKS AND TILES. 241 perature required to burn them, and render them per- manently hard, the great store of heat which they contain is entirely thrown to waste while they are left to cool. In this new kiln a remarkable economy of fuel is effected, by saving the twofold loss of heat already mentioned : first, it saves the heat of the gaseous products of combustion and unconsumed air passing through and away from the burning bricks, by applying this heat effectively in drying the new fresh bricks about to be burnt, and raising them up to an incandescent temperature, so that oiiiy a very slight addition of heat from ignited fuel directly is required to complete their burning; and, secondly, it saves the heat of the cooling bricks, after their having been sufficiently fired, by applying: it all again in warming the air which goes forward (o supply the fires ; so that the fuel is bufnt with air already at nearly an incan- descent temperature, instead of requiring, as usual, to heat the air for its own combustion. Professor Thom- son explained, as an example, the large kiln which Mr. Moore was then constructing at his brick- works at HayfieldPark,in the neighbourhood of Belfast. Thekiln, as will be seen, is built in the form of a large arched passage, like a railway tunnel, bending round in going forward on the ground till it closes with itself to form a great circular ring-chamber, within which the burning of the bricks is carried on. This ring-chamber may be of any convenient dimensions, 160 ft. diameter being a suitable size. Round its circumference there are twenty-four entrance doorways, admitting of being closed with temporarily-built bricks and clay, so as to retEfin the heat and exclude all entrance of air by the doorways so built up. The great ring- chamber may now be conceived as consisting of twenty-four compartments 242 RUDIMENTS OF THE or spaces, with one of these doorways to each. In the centre of the ring a high chimney is erected, and from each of the twenty-four compartments of the annular chamber an underground flue leads into the chimney. There are, then, twenty-four of these flues converging towards the centre like the spokes of a wheel, and each flue has a valve, by which its communication with the chimney can be cut off. Arrangements are made by which a partition like a damper can be let down at plea- sure, or otherwise placed, so as to cut off all communi- cation between any of the twenty-four compartments of the ring- kiln and the next one. Let us now suppose the working of the kiln to have been already fairly esta- blished ; for, after being once kindled, the fire is never extinguished, but the burning of new bricks and the removal of the finished produce are carried on by a con- tinuous and regular process from day to day. Two adjacent compartments have this day their entrance doors open, all the rest being perfectly closed. By the arrangement of the valves in the flues, and the large partition, the air which gets admittance alone by the two open doors has to go round the whole circuit of the ring-kiln in order to be drawn into the chimney. From one of the two open compartments men are taking out the finished and cooled bricks, and in the other one they are building up newly-formed unburnt bricks which are not yet quite dry. The air, entering by these two compartments, passes first among bricks almost cold and takes up their heat, and then goes forward to warmer bricks, and then to hotter and hotter, always carrying the heat of the cooling bricks forward with it till it reaches the part of the ring diametrically opposite to the two open and cold compartments. At this place it gets a final accession ART OF MAKING BRICKS AND TILES. 243 of heat from the burning of a very small quantity of small coal, which is dropped in among the bricks from time to time by numerous small openings furnished with air-tight movable lids. Thus at this part of the kiln there is generated the full intensity of heat which is required for the burning of the bricks. The hot air, including the products of combustion , which, for brevity, we may call the smoke, though it is really perfectly gaseous and free from sooty particles, then passes for- ward to the bricks, which, by its continuous current, are being heated ; and it passes on among them from hot bricks to those which are less and less hot, heating them as it goes, and then passes on to those which are still damp, drying them as it goes ; and then it passes to the chimney, in a state almost cold, and saturated with the moisture, in the form of steam or vapour, which it has taken from the damp bricks. On the following day to that on which the operations just described have been going on, the partition is shifted forwards by the space of one compartment, and a corresponding change is made as to the flue which is to communicate with the chimney, and as to the pair of compartments open for the admission of air and for the removal of finished cold bricks, and the building in of fresh damp bricks ; and so the air, including the products of combustion, at the end of its circuit in the annular chamber, just before passing off to the chimney, now passes among the fresh bricks which were described as built in on the yesterday of this new day. The place where the small- coal fuel is thrown in is also advanced round the circle by the stage of one compartment ; and so now the whole process goes on just as it did yesterday. The fire thus makes a complete circuit of the annular chamber in twenty-four working days. The whole M2 244 1RT OF MAKING BRICKS AND TILES, process may be left dormant on Sundays, merely by the closing of all apertures for the admission of the current of air. The same kind of kiln, with the same process of working, is applicable in the burning of lime ; and both for the brick-burning and the lime-burning, the saving of fuel, relatively to what is consumed by the ordinary methods, is such as to appear at first sight almost incredible. The Hoffmann or Chamberlain kiln is not so easily applicable to burning lime as it is to brick, nor will it answer without considerable modification for burning thin and light tiles or pottery. There must be mass enough in the goods to be fired to afford the requisite magazine of absorbed heat to be afterwards used up, and the draught must not be impeded as by the breaking down of limestone when burnt into lime. Those kilns are not necessarily made circular. They are, indeed, now more usually rectangular, with or without rounded ends, in plan. When originally writing the preceding, the author of this chapter had not himself seen those kilns at work, and hence quoted from others as to their properties, &c. He has since, however, had occasion, professionally, to make himself fully acquainted with their construction and perform- ance, and can indorse fully all that has been stated, and, indeed, might say much more in their com- mendation. Many structural improvements and simplifications have latterly been made in those kilns ; but as the patentee, Mr. H. Chamberlain, as a Pottery Engineer, is professionally engaged in providing designs for those who employ these kilns, it would not be fair that the writer should here enter into further details. APPENDIX I. THE following paper was read by Mr. Tomlinson at a meeting of the Geologists' Association, on February 3, 1862 : ON THE PLASTICITY AND ODOUR OF CLAY. It is a happy result of Bacon's method of inquiry that science is not required to explain the causes of things, but to state the laws of phenomena. Nevertheless, while these laws are obscure, and facts are scattered, theory may often do good service by collecting and marshalling them : for, as our great master of induction well observes, "Facts are the soldiers, but theory is the general." And again, " Truth is more easily evolved from error than from confusion." That is, a bad theory is better than none at all, for it serves to collect and arrange the facts, and thus makes them more easy to handle. In these remarks must be found my excuse to-night for endeavour- ing to bind together some of the facts respecting a property of a very common substance ; namely, the Plasticity of Clay. The more I consider this property the more wonderful and inex- plicable does it appear. Take a mass of dry clay ; it cracks easily, and crumbles readily : add to it a certain proportion of water, and it becomes plastic it obeys the will of the artist or the artizan, who can, out of this yielding mass, create new forms, or perpetuate old ones. Drive off the water at a red heat, and plasticity is for ever lost ; rigidity takes its place : the clay is no longer clay, but some- thing else. It may be reduced to powder, and ground up with water ; but no art or science can again confer upon it its plasticity. All this is very wonderful. There is another fact that is equally EO : if we combine the constituents of clay in the proportions indi- cated by the analysis of some pure type of that substance, we fail to produce plasticity. I have on the table specimens of Dorset clays dry and crumbling ; the same wet and plastic ; and the same in the forms of casts of fossils, which have been passed througli the. five, 246 APPENDIX. and have exchanged plasticity for rigidity. They are, in fact, in the form of biscuit. With respect to the temperature at which clay becomes rigid, we have no accurate information. It is much lower than is generally supposed, as will appear from the following experiment : I pounded and sifted some dry Dorset clay, and exposed it to a sand-bath heat in three portions varying from about 300 to 600. Specimens were taken out from time to time, and rubbed up with water, but they did not lose their plasticity. Some clay was put into a test tube with a small quantity of mercury, and heated until the mercury began to boil. At this temperature (viz. 650) the clay did not cease to be plastic. The flame of a spirit-lamp was applied, and the tube was heated below redness ; after which the clay, on being mixed with water, showed no sign of plasticity. In experiments of this kind, the first action of the heat is to drive off the hygrometric water. The clay then becomes dry, but is not chemically changed ; it does not cease to be plastic. On continuing to raise the temperature, the chemically combined water is separated, and the clay undergoes a molecular change, which prevents it from taking up water again, except mechanically. With the loss of this chemically combined water, clay ceases to be plastic. It was, I believe, first noticed by Brongniart,* that we cannot pro- duce plasticity by the synthesis of clay. The fire clay of Stem-bridge, for example, is a hydrated silicate of alumina, represented by the for- mula A1 2 3 , 2 Si 2 + 2 Aq. If we mix one atom of the sesqui- oxide of alumina with 2 atoms of silica and 2 of water, we get a compound which cannot be called clay, since it is wanting in plasticity. It is quite easy to obtain either alumina or silica in the gelatinous state ; but we cannot obtain them in the plastic state. Clay is almost the only substance in the mineral kingdom that pos- sesses plasticity. In loam, if the sand be in large proportion, and in marl, if calcareous matters abound, so as to deprive either material of plasticity, it ceases to be clay. There are also certain silicates of alumina which are not plastic ; such as bole, lithomarge, and fullers'- earth. Bole consists chiefly of a hydrated bisilicate of alumina, in which a portion of the alumina is replaced by sesquioxide of iron. Lithomarge also contains iron, and is sometimes so compact as to be used for slate-pencils. Fullers'-earth contains lime, magnesia, and iron, in addition to its principal ingredients. TraiM des Arts Cdramiques." Paris, 1844. Vol. 1. p, 82. APPENDIX. 247 There is probably no substance so indeterminate in its composition as clay. Regarding it, as Lyell does,* as " nothing more than mud derived from the decomposition of wearing down of rocks," it must necessarily contain a variety of substances ; such as oxide of iron, lime, magnesia, potash, silica, bitumen, fragments of undecomposed rock, &c. These substances impair the plasticity of the clay, and impress upon it certain characters which are of more importance to the manufacturer than to the chemist, or the geologist. Brongniartf enumerates, and gives the analyses of no fewer than 167 clays and 28 kaolins, all of which are in use in the arts in different parts of the world. They probably all differ in plasticity, but they all possess it ; and at a high temperature exchange it for rigidity. A rough method of measuring the plasticity of different clays is to note the length to which a cylinder of each can be drawn out in a vertical direction without breaking. In such a comparison, the clays must, of course, be worked equally fine, and contain the same proportion of water. It is commonly stated that the ingredient that confers plasticity on clay is its alumina ; and yet, strange to say, pure alumina alone whether gelatinous, or after having been dried and ground up with water for a long time, never gives a plastic paste. Indeed, nothing can be conceived less plastic than gelatinous alumina, as may be seen from the specimens on the table. We may drive off most of the water from this gelatinous hydrate, but it will not become plastic. Or we may form clay by mingling solutions of the silicate of alumina and the aluminate of potash. You see they are perfectly fluid. I apply the heat of a spirit-lamp, and we get an opalescent gelatinous mass, but still no plasticity. We have, indeed, formed a gelatinous clay. We cannot say that the gelatinous state of alumina is the cause of plasticity in clay ; for silica may be made as gelatinous as alumina, and silica is certainly not the cause of plasticity. It may be that the strong affinity of alumina for water (retaining a portion of it even when near a red heat) may be the cause of this property just as turpentine renders wax plastic; and water and gluten confer the same property on starch. We have seen that clay ceases to be plastic when its chemically combined water has been driven off. Still, however, water cannot be said to be the cause of plasticity, as a general property, since we have, in melted glass, a more perfect example of plasticity even than * "Manual of Elementary Geology " (1855), p. II. t " Des Arts Ce'ramiques," Atlas of Plates. 248 APPENDIX. in clay ; and few substances are more plastic than sealing-wax ut a certain temperature. A clear idea of plasticity, and of some of the other mechanical properties of matter, may probably be gained by considering them as variations of the forces of cohesion and adhesion, and by bringing these, in their turn, under Newton's great law of attraction, which, whether exerted between atoms or masses, is directly as the mass, and inversely as the squares of the distances. Now, if we suppose the distances between the molecules of matter to be 1-millionth or billionth, or 2, 3, 4, 5, 6, &c., millionths or bil- lionths of an inch asunder, the intensity of their attractions will be 1, th, -Jth, TVh> &c., or, to represent it in a tabular form : Distances 1 2 3 4 5 6 7 8 9 10, &c. Intensities of attraction 1 i i TB- -sV ^V *V -&V "rr TOTT* &c. Suppose the molecules to be of the same density, but at different distances apart, as represented in the upper line. At the distance of 1-millionth of an inch we get an intensity of attraction represented by 1. At 2-millionths of an inch the force of attraction is only one- fourth. Now, the idea is this, that the mechanical properties of matter, such as porosity, tenacity, hardness, brittleness, plasticity, elasticity, &c., depend upon variations in the attractive force of the molecules according to the distances apart of such molecules. Thus, if the molecules of clay require to be 5-millionths of an inch apart in order to produce plasticity, the intensity of attraction between them will be represented by ^Vth ; but if such clay be passed through the fire, and the molecules, in consequence of the escape of water, be brought nearer together, and rigidly fixed at 4-millionths of an inch asunder, the force of attraction will then be yVth. Now, the method of arranging the particles of clay at that precise distance that shall impart plasticity, is one of Nature's secrets that we have not yet succeeded in penetrating. It may be that the circum- stances under which clay is formed and deposited, or the time that has elapsed since its formation, or the pressure of the superposed layers, may have so arranged the particles as to enable them to become plastic when the proper proportion of water is added. It may be that a certain state of disintegration is required on the part of the alumina and the silica, so that their proximate elements shall be neither too fine nor too coarse ; or it may be that the silica, in combining with the alumina, separates the atoms of the latter to pre- cisely those distances required for the development of the property ; APPENDIX. 249 or, lastly, the presence of a small portion of animal or other organic matter in clay may have something to do with this remarkable pro* perty. An extensive series of experiments, by Delesse,* show the presence of animal matter in quartz and various rocks, where its presence had not previously been suspected ; and this may have as important an effect in modifying the properties of a mineral as the presence of minute portions of bodies, formerly entered as impurities, has in producing pseudo morphous crystals. Still, the question recurs, Why is not a clay artificially formed from pure materials plastic ? The answer is, that we do not know all the conditions of plasticity. We do know the conditions under which some mechanical properties exist sfldh as the hardness of steel, the brittleness of unannealed glass and can confer or remove such pro- perties at pleasure. But with respect to plasticity, we can only confer a factitious property of this kind on mineral substances by taking advantage of another property which it somewhat resembles, namely, viscosity or viscidity. Viscosity differs in plasticity in this, that the viscous body does not retain the form impressed upon it when the force is removed, as a plastic body does. The materials of the old soft porcelain of Sevres had no plasticity ; but this property was con- ferred by means of soft soap and parchment size.f Without speculating further on the nature of plasticity, I may remark that in the ancient philosophy the word was one of power. Derived from the Greek ir\aaai iv, or rrXaTTfiv, " to form," or " to create," it not only included the arts of modelling in clay, but also sculpture and painting, and, by a refinement of language, poetry and music. Plato and Aristotle even supposed that a plastic virtue resided in the earth, or did so originally, by virtue of which it put forth plants, &c. ; and that animals and men were but effects of this plastic power. They did not suppose the world to have been made with labour and difficulty, as an architect builds a house ; but that a certain " efficient nature" (natura effecirix) inherent and residing in matter itself, disposed and tempered it, and from it constructed the * " De I'azote et des matures organiques dans 1'ecorce terrestre." Annettes des Xinet, xviii., 1860. t Brongniart ("Des Arts Ceramiques ") says that the old porcelaines tendres were formed of 22 per cent, of fused nitre, 60 of Fontainebleau sand, 7-2 of salt, 3-6 of alum, 3-6 of soda, and 3-6 of gypsum. These materials were fritted and ground, and 75 parts taken, to which were added white chalk 1 7 parts, marl 8. This mixture was ground, sifted very fine, and made up into a paste with l-8th soft soap and size, or, at a later period, with gum tragacaath. M3 250 APPENDIX. whole world. Aristotle distinctly recognises mind as the principal and directing cause, and natura as a subservient or executive instru- ment. Even in later times men have contended for the existence of a plastic nature, or incorporeal substance endowed with a vegetative life ; but not with sensation or thought, penetrating the whole uni- verse, and producing those phenomena of matter which could not be solved by mechanical laws. The learned Cudworth supports this view,* and the discussions into which it led him and other metaphy- sicians form a curious chapter in the history of the human mind. In England we do not now retain the term plasticity, except as a phy- sical property of matter ; f but in Germany it has still an extensive figurative meaning. The word plastisch still means bildend or schopferisch (i.e. " creative") ; and it is still applied not only to sculp- ture, but also to painting, poetry, and music. A German well under- stands the expression " plastische Gedanken," or " plastic thoughts." Before concluding, I would refer to another property of clay, which seems to me as wonderful as its plasticity ; namely, its odour when breathed on, or when a shower of rain first begins to wet a dry clayey ioil. This odour is commonly referred to alumina, and yet, strange to say, pure alumina gives off no odour when breathed on or wetted. The fact is, the peculiar odour referred to belongs only to impure clays, and chiefly to those that contain oxide of iron. This was pointed out by Brongniart as far back as ]8].6,| who also remarked that minerals which do not contain alumina, such as pulverised chal- cedony, possess this remarkable property. I have found that a pure kaolin, ground up in a mortar with a small quantity of water, emits a slight odour, which, however, becomes much more sensible if a little sesquioxide of iron be added. Smooth quartz pebbles when rubbed together give an electric spark, and a fetid odour. It is commonly supposed that sea-side pebbles alone possess this property ; but the odour belongs equally to those found among gravel overlying the chalk, and in ploughed lands where the surface is exposed to all the vicissitudes of the weather. It is quite possible that the odour of these pebbles may hereafter be traced to the presence of organic matter ; but I cannot resist the reproduction here of a suggestive hint given me by my friend Professor Bloxam, See " The True Intellectual System of the Universe," by Ralph Cuclworth, D.D., 1678. A reprint has been published by Tegg, in which see Vol. I., p. 226, et teq. j Dr. Johnson defines plastic as " having the power to give form. J " Dictionnaire des Sciences Naturelles," art. Argile. APPENDIX. 251 who is reminded by the spark and odour from these pebbles of the presence of ozone. What, again, is the cause of the odour in the narrow parts of stone buildings, not of new buildings alone, but of old ones, as in the stair- cases of old cathedrals ? I do not attempt to reply to these questions. It requires some amount of knowledge and experience to put them but how much more to answer them ! ON DRYING BRICKS. (Extracted from Noble's " Professional Practice of Architects" p. 143.) " The observations by Richard Neve, above a century since, upon sfock bricks, will illustrate the subject : ' When the hack is as high as they think fit, they cover them with straw till they are dry enough to burn, ' &c., &c. He proceeds : f A brickmaker being sent to Rum- ford, in Essex, went to work unadvisedly, and laid them abroad in a place to dry ; but the sun, about ten o'clock, began to shine very hot, and the whole quantity of bricks burst to pieces, so that he was forced to go to work again : and then, before the sun shone too hot, he thatched or covered them over with straw till the next morning, when removing it, they did very well when set on the hack ; and when burnt, were curious red bricks, which would ring when hit with any hard thing.' " ON THE USE OF COAL DUST IN MAKING CLAMP BRICKS. (Extracted from Noble's " Professional Practice of Architects" p. 153.) " Natives should be employed (in making bricks in Wales} in the manufacture, in preference to London hands, as the former use coal dust in preparing the earth, and not breeze (ashes), as about London ; and provided an undue portion of coal is used, a whole clamp would be destroyed, of which there was an instance at Lampeter (Cardigan- shire). An Islington brickmaker was sent to Wales, and as he was too conceited to make inquiries, or to receive information, set light to a clamp he had prepared with coal, being 70,700 ; and in a very short time the whole kiln was in one general blaze. The man being alarmed, took to his heels, and, unlike Lot's wife, he turned not back, neither looked behind him. Even from the heights leading to Landovery the reflection was quite enough for him ; nor did he stop 252 APPENDIX. till he reached London, being, as he said, 'afeared' they would catch him and put him in prison ! " BRICKMAKING AT GREAT GRIMSBY, LINCOLNSHIRE. Large quantities of bricks have been made during the last few years at Great Grimsby, for the Dock Company, from the Humber silt. These bricks are remarkable for their colour, which varies in the same brick from dark purple to dirty white, passing through various shades of blue, red, and yellow, in the space ot two or three inches. The silt, when first dug out of the bed of the Humber, is of a dark blue colour, which soon, from exposure to the air, changes to a brown. The bricks made for the Dock Company were burnt in close clamps fired with layers of small coal, but without coal-dust or ashes being mixed with the clay as in London brickmaking. With the first clamps there was much waste, the cfuantity of fuel being excessive, and the bricks were cracked and made brittle in conse- quence ; but the experience obtained by the first trials has led to the production of a sound well-burnt brick, with, however, the peculiar colour above mentioned. Considerable quantities of bricks have been lately made for sale at Great Grimsby, and burnt in clamps with flues, as in kiln burning, which method appears to be attended with less waste than close clamping. The slack or small coal used for fuel may cost from 2s. fid. to 4#. per 1,000 bricks. The cost of clay getting, tempering, moulding, and drying, is about 8s. Qd. per 1,000. The moulds used are of wood, plated with iron. The process employed is that known as slop-moulding. Kilns as well as clamps are used in this part of Lincolnshire, their construction being similar to that of the kilns in general use in the Midland Counties. BRICKMAKING IN SUFFOLK. Two kinds of bricks are made in Suffolk, viz., reds and whites. The latter are much esteemed for their shape and colour, and large quan- tities are annually sent to London, for facing buildings of a superior class. APPENDIX. 253 Clay. The supplies of brick-earth are chiefly derived from the plasao clays lying above the chalk, although the blue clay is occasion- ally used. The clays in most parts are too strong to be used as they rise, and have consequently to be mixed with a white loam or a milder earth. Tempering. The clay is turned over in February and March, and in some parts of Suffolk it is passed through the wash-mill, but this is not generally the case. Tempering is generally performed by spade labour, but the pug-mill is sometimes used, although not commonly, for white bricks ; it is, however, used for all other white ware. Moulding. The bricJc mould is of wood, shod with iron; the dimen- sions vary slightly according to the nature of the clay, but are usually as follows : 9f ths long by 4y-fths wide and 3 deep. There is no hollow formed in the bottom of the brick for the mortar joint. Brass moulds are unknown. Sea sand is used in the process of moulding, for sanding the mould and the table. The strike is used for taking off the superfluous clay from the mould. The use of the plane is not known. Drying. The bricks are not dried on flats as in the Midland Coun- ties, but are taken directly from the moulding stool to the hacks. Sheds are used in some yards, and drying houses with flued floors are used in winter for pantiles and kiln tiles, but not for bricks. The length of a hack is about 70 yards, and each moulder will keep four hacks going. The time required for drying in the hacks of course varies according to the weather, but may be stated on an average at about eighteen days for red bricks. White bricks dry somewhat quicker. The contraction of the clay in drying amounts to about f in. in the length of a brick, and, if properly burnt, the shrinkage in the kiln is imperceptible. The weight of a brick, when first moulded, is about 8 Ibs. ; when dried, about 7 Ibs. ; and when burnt, about 6 Ibs. ; but much depends upon the nature of the earth. Burning. The construction of the kiln is quite different from that of the kilns used in other parts of England, having two arched 254 APPENDIX. furnaces running its whole length underneath the floor, which is formed of a kind of lattice work, through the openings of which the heat ascends from the furnaces below. The cost of erecting a kiln to burn 50,000 whites is about 145. A kiln to burn 35,000 reds costs about 100. The bricks are commonly set in the kiln in bolts two bricks long by ten on ; but some brickmakers prefer to cross them in the alternate courses, in order to admit the heat more freely. The fuel used is coal, and the quantity consumed is about half a ton per 1,000 for white, and 7 cwt. per 1,000 for red, bricks. The time of burning is about 60 hours for white, and 40 hours for red, bricks ; white bricks requiring a greater heat than the red ones to bring them to their proper colour. The coal costs from 15s. to 16s. per ton. Cost of Manufacture* The selling prices vary from 1 10s. to 2 per 1,000 for reds, and from 2 2s. to 3 per 1,000 for whites. Of red bricks two qualities only are distinguished, viz., out- side and inside ; of white, four qualities are distinguished, viz., best, 2nd, 3rd, and murrays. The price of the ordinary red brick is about 1 10s. per 1,000, and the cost may be thus divided : s. d. Clay digging, per 1,000 026 Tempering, ditto 010 Moulding, ditto 050 Drying, ditto 006 Barrowing from hacks and setting kiln ditto .010 Burning, ditto . . . . . .013 Drawing kiln, ditto 008 Stacking, ditto 003 Cost of labour per 1,000 12 2 Coals, about 060 Duty 6 1 Rent, tools, contingencies, and profit . . 5 8 Selling price at the yard, about 1 10 These estimates belong to the date of the First Edition of this work. APPENDIX. 255 White bricks are made in many parts of England, but the Suffolk whites have the pre-eminence over all others. The white bricks made near Lincoln are remarkable for swelling when laid in work, which causes them to throw off the mortar joints, and renders it impossible to make use of them in good work. The clay from which these bricks are made extends from the Witham northwards as far as the Humber, and, so far as we are aware, possesses the same property throughout this distance, the bricks made from it at various points between the Witham and the Humber having the common defect of swelling after burning. A curious specimen of this may be seen in a large chimney at Saxilby, which has a complete twist, from the irregular swelling of the brick- work. The peculiar property of swelling after burning is not confined to the Lincolnshire white clay. The author was informed some years ago, by Mr. Vignoles, C.E., that some of the bricks made on the Midland Counties Line of Railway, between Rugby and Derby, had the same defect. For the above particulars respecting the Lincolnshire white bricks we are indebted to Mr. William Kirk, of Sleaford. ON THE MAKING AND BURNING OF DRAIN TILES. Extracts from a communication by Mr. Law Hodges, published in the Journal of the Royal Agricultural Society of England, Vol. V. Part II.: "Reflecting on these obstacles to universal drainage, where required, I conferred with Mr. John Hatcher (brick and tile maker, and potter, Benenden, Kent), on the possibility of erecting a kiln of common clay that would be effectual for burning these tiles, and of cheap construction and the result was the building one in my brickyard in July last, and the constant use of it until the wet weather at the commencement of this winter compelled its discon- tinuance, but not until it had burnt nearly 80,000 excellent tiles ; and in the ensuing spring it will be again in regular use. "I shall now proceed to take in order the six points enumerated under the 9th head of the Prize Essays for 1845, as printed in the last volume of the Royal Agricultural Society's Journal, viz. : APPENDIX. lbt Mode of working clay according to its quality, " 2nd. Machine for making tiles. " 3rd. Sheds for drying tiles. " 4th. Construction of kilns. " 5th. Cost of forming the establishment. " 6th. Cost of tiles when ready for sale. " 1st Point. Working the clay. " All clay intended for working next season must be dug in the winter, and the earlier the better, so as to expose it as much as pos- sible to frost and snow. Care must be taken, if there are small stones in it, to dig it in small pits, and cast out the stones as much as possible, and also to well mix the top and bottom of the bed of clay together. It is almost impossible to give minute directions as to mixing clay with loam, or with marl when necessary, for the better working it afterwards, as the difference of the clays in purity and tenacity is such as to require distinct management in this respect in various localities ; but all the clay dug for tile-making will require to be wheeled to the place where the pug-mill is to work it ; it must be there well turned and mixed in the spring, and properly wetted, and finally spatted down and smoothed by the spade, and the whole heap well covered with litter to keep it moist and fit for use through the ensuing season of tile-making. " 2nd Point. Machine for making tiles. " For the reasons already alluded to, I prefer Hatcher's machine- Its simplicity of construction, and the small amount of hand labour required to work it, would alone recommend it ; for one man and three boys will turn out nearly 11,000 pipe tiles of 1 in. bore in a day of ten hours, and so in proportion for pipes of a larger diameter ; but it has the great advantage of being movable, and those who work it draw it along the shed in which the tiles are deposited for drying, previously to their being burnt : thus each tile is handled only once, for it is taken off the machine by the little boys who stand on each side, and at once placed in the rows on either side of the drying shed, thus rendering the use of shelves in the sheds wholly unnecessary, for the tiles soon acquire a solidity to bear row upon row of tiles, till they reach the roof of the sheds on either side ; and they dry without warping or losing their shape in any way. " The price of this machine is 25, and it may be proper to add, that the machine makes the very best roofing tiles that can be made, and at less than half the price of those made by hand, as well as APPENDIX. 257 being much lighter, and closer, and straighter, in consequence of the pressure through the die. " It is necessary, in order to ensure the due mixing of the clay, as well as to form it into the exact shape to fill the cylinders of the machine, to have a pug-mill. Messrs. Cottam and Hailen make these also, and charge 10 for them. This mill must be worked by a horse ; in general one day's work at the mill will furnish rather more prepared clay than the machine will turn into tiles in two days " 3rd Point. Sheds for drying. " The sheds necessary for this system of tile-making will be of a temporary kind : strong hurdles pitched firmly in the ground in two parallel straight lines, 7 ft. apart, will form the sides of the sheds, and the roof will be formed also of hurdles placed endways and tied together at the top, as well as to the upper slit of the hurdle, with strong tarred twine, forming the ridge of the roof exactly over the middle of the shed. They must then be lightly thatched with straw or heath, and the sharpness of this roof will effectually protect the tiles from rain. Two of these sheds, each 110 ft. long, will keep one of the kilns hereafter described in full work. " N.B. These sheds should be so built as to have one end close to the pug-mill and the clay-heap, only leaving just room for the horse to work the mill, and the other end near the kiln. Attention to this matter saves future labour, and therefore money. " 4th Point. Construction of kilns. " The form of the clay kiln is circular, 11 ft. in diameter, and 7 ft. high. It is wholly built of damp earth, rammed firmly together, and plastered inside and out with loam. The earth to form the walls '.s dug out round the base, leaving a circular trench about 4 ft. wide and as many deep, into which the fire-holes of the kiln open. If wood be the fuel used, three fire-holes are sufficient ; if coal, four will be needed. About 1,200 common bricks are wanted to build these fire-holes and flues; if coal is used, rather fewer bricks will be wanted, but then some iron bars are necessary six bars to each fire- liole. " The earthen walls are 4 ft. thick at the floor of the kiln, are 7 ft. high, and tapering to the thickness of 2 ft. at the top ; this will determine the slope of the exterior face of the kiln. The inside of the wall is carried up perpendicularly, and the loam plastering inside becomes, after the first burning, like a brick wall. The kiln may be safely erected in March, or whenever the danger of injury 258 APPENDIX. Fig. 1. Plan of Kiln at A B, Jig. 3. Fig. 2. P/aw o/ Top of Kiln. APPENDIX. Fig. 3. from frost is over. After the summer use of it, it must be protected by faggots or litter against the wet and the frost of winter. " A kiln of these dimensions will contain 47,000 1-in. bore pipe tiles. 32,500 \\ 20,000 If 12,000 2J and the last-mentioned size will hold the same number of the inch pipes inside of them, making therefore 24,000 of both sizes. In good 26C APPENDIX. Fig *. \ weather this kiln can be filled, burnt, and discharged once every fort- night ; and fifteen kilns may be obtained in a good season, producing 705,000 1-in. pipe tiles. Or 487,500 1J- Or 300,000 If and so on in proportion for other sizes. " N.B. If a kiln of larger diameter be built, there must be more fire-holes, and additional shed room. APPENDIX. 261 " 5th Point. Cost of forming the establishment. The price charged by Messrs. Cottam and Hallen for th machine, with its complement of dies, is 25 Price of pug-mill 10 Cost of erecting kiln 5 Cost of sheds, straw 10 50 (The latter item presumes that the farmer has hurdles of his own.) " 6th Point. Cost of tiles when ready for sale. " As this must necessarily vary with the cost of the fuel, rate of wages, easy or difficult clay for working, or other local peculiarities, I can only give the cost of tiles as I have ascertained it here accord- ing to our charges for fuel, wages, &c., &c. Our clay is strong, and has a mixture of stones in it, but the machine is adapted for working any clay when properly prepared. " It requires 2 tons 5 cwt. of good coals to burn the above kiln full of tiles. Coals are charged here at 1 &s. per ton, or 1,000 brush faggots will effect the same purpose, and cost the same money ; of course some clays require more burning than others ; the stronger the clay the less fuel required. " The cost of making, the sale prices, and number of each sort that, a waggon with four horses will carry, are as follows : Cost. Sale Price. Waggon t. d. s. holds 1-in. pipe tiles 4 9 per 1,000 12 8,000 1J 60 14 7,tOO 1| 80 16 5,000 2f 10 20 3,500 2 12 24 3,000 Elliptical tiles 24") Soles 10 } ' ' 2 ' " All these. tiles exceed a foot in length when burnt. " The cost price alone of making draining tiles will be the charge to every person making his own tiles for his own use. If he sell them, a higher price must, of course, be demanded to allow for scxne profit, for credit more or less long, for bad debts, goods unsold, &c. &c. ; but he who makes his own saves all expense of carriage, and, as his outlay will not exceed 50, the interest on that sum is too trifling to be regarded, and he has no additional rent to pay; and after he has made as many tiles as he wants, his machine and pug-mill will be as good as ever, with reasonable care, and will fetch their value." APPENDIX II. THE SCIENCE OP BRICKMAKING. IT has been said by the author of this volume, in his preface, *-hat the science of brickmaking has yet to be formed and written. This is no doubt in one sense true, though it must be remarked that, inasmuch as the art of the brickmaker is to be viewed in its chemical and physical relations as only the humblest branch of that of the potter or porcelain manufacturer, the saying so is not to dis- credit the vast and wide-spread importance of exact knowledge to the brickmaker, nor of the value of his universally-diffused and indis- pensable art. The manufacture of pottery, in all its branches, having been the subject of lengthened and important scientific labours at the hands of successive able men of science, amongst whom are Reaumur, Bottcher, Brongniart, Malaguti, and Salvetat, as well as of the tentative and technological labours of innumerable manufacturers, amongst whom Cookworthy, Chaffers, Wall, Wedgwood, Minton, and others stand pre-eminent, in England alone, it cannot be said that pottery in general is devoid of a formed and established science, though very much remains to be discovered over its wide domain of theory and practice. This being so, and very much of the science of the porcelain manufactory being directly applicable and available in the brick-field (if indeed the brickmaker himself possess the requisite foundation in general scientific education, especially in chemistry and physics), it is only true in one sense that no science of brickmaking yet exists, namely, in the sense that the knowledge we already possess of the science of the ceramic arts has not yet been systematised and applied in a special manner to the brickmaker's art. To attempt to supply this want in the present little volume is impossible. Three such volumes would scarcely afford sufficient space to treat of the science of brickmaking in a systematic and complete manner. APPENDIX. 263 Still it seems undesirable that in an elementary outline of this art so little should have been given in the original text, even as a sketch, of some salient points which such science presents. We shall attempt this, however incompletely. The brickmaker deals with natural clays only, the constitution of which, when more or less ascertained in respect to his object, he may modify by the addition of other mineral bodies, such as sand, ashes, &c., or by the mechanical extraction of naturally-mixed matter, as sand, pebbles, pyrites, &c., and whose physical qualities he may alter by mechanical means grinding, " slip-washing," &c. The choice of a clay that shall answer well for the brickmaker's use cannot be made before trial, by any amount of examination, unless we also possess a chemical analysis of the natural material. Aided by that, it is quite possible upon tempering a ball of the clay, observ- ing its plasticity and body, and then wetting further a little bit, and rubbing it between the thumb and the forefinger, to tell with a great degree of certainty whether it will make good brick or not ; either alone or, as is almost always the case, mixed (and so altered) either with more sand or more tough clay, and occasionally with coarsely- ground coal, or breeze, or ashes, &c. Clays are essentially chemical compounds, and this is true, whether they be or be not always mere mud from disintegrated rocks, as some geologists have probably erroneously supposed. They are in fact true hydrates, and have the general constitution (SO-}- A1 2 3 ) + H U ; the last or accidental base or bases being usually cal- cium, magnesium, manganese, or iron, or more than one of these ; and they may be divided into four great classes. Pure aluminous clays and pure magnesian clays, both hydrated : these are rare, the latter especially so when indurated, constituting meerschaum; and we may pass them without further notice here. They belong, not to the brickmaker, but to the porcelain-maker. More widely spread for our use, we have the ferruginous clays, which have generally this combination (Si + (A1 2 Os + Fe 2 O 3 ) Fe -f N -f K 0) + H O ; and the calcareous clays (Si O + (A1 2 3 + Fe 2 3 ) + (Ca O + C 2 + Mg O + C O 2 ) Fe + N + K 0) + H O. Either of these may be mixed with more or less siliceous sand, and when this is in considerable proportion the clay is a loam. At a red heat they lose most of their combined water, losing more sr less hygroscopic water at 212; and at a bright yellow or white 264 APPENDIX. heat, or rather below it, they bake into pottery or brick. And while many of the clays rich in alumina, silica, and iron do not fuse, or but very slowly, at the melting-point of cast-iron, most of the cal- careous clays melt at or below this temperature, or at least agglu- tinate, assuming the vitreous texture if the heat be long continued. The following table contains the analysis of ten natural clays, which gives a pretty clear notion of their usual range of constitu- tion : No. 1 is a fuller's earth, analysed by Dr. Thomas Thomson. No. 2. A sandy clay, known as the " ball-clay " of the Potteries, and used for salt-glazed ware , analysed by Cowper. No. 3. An ash-white pipe-clay. No. 4. A grey-blue clay. No. 5. A red-brown Glasgow clay. No. 6. A yellow midland counties clay, used for brick and for Buckingham pottery. (All these analysed by Cowper, Phil. Mag, xxxi. p. 435.) No. 7. A marly English clay ; analysed, with the following, by Berthier. No. 8. A marl from Vitry, Department of Marne ; used in Paris foundries. No. 9. A German clay (Loess of the Rhine), used at Bonn ; analysed by Kjenulf. No. 10. A loam, analysed by Dr. Uie. APPENDIX. 265 1 CO CO co o V r^-l I 1 r-l op o -o O5 cb * " ' b CO i I ei 05 05 O C-1 O r-l O 00 ip o . co co b J3 -co b i XH CD CN CO TH .05 . .t^ .rH rH 4H 'A. IO * oo CO CO o i i i i cb CO CO co s o o CO "? "^ *? O fn * * O * C^ i CO CO cb CO CO o ^t" f tools, 161; cost of water, 159; cost of wood, 159 ; illustrations of London brickmaking, 164. London brickmaking : bats, 156 ; place bricks, 156 ; turnovers, 153 ; burrs, 156; clinkers, 153; cutters, 155 ; grizzeles, 156 ; malms, 155 ; paviours, 156 ; pickings, 156 ; second?, 156 ; shuffs, 156 ; grey stocks, 156 ; rough stocks, 156. London tile making described, 167; block board described, 175 ; build- ings, 170; clay getting, 183 ; kiln, 183; kilning, 186; illustrations to, described, 186 ; moulding, 184 ; moulding-shed, 173 ; pantile table. 174; place grounds, 187; plant, 170; roll described, 177; sling, description of, 170 ; slinging, 184 ; splayer, 180; tempering, 184; thwacker, 183; thwacking, 185; thwacking frame, 180; thwacking knife, 183 ; thwacking stool, 183 ; washing-off frame, 178 ; wash- ing-off table, 177 ; weathering, 183. Marls, 14. Minton's encaustic tile manufactory described, 191. Moulding, process of, 28. Moulding table, 29. INDEX. 275 N T orton coal, analysis uf, 117. Nottingham, brickmaking at, 55 ; process of, 80 ; illustrations of, described, 92 ; batting, 82 ; cost of buildings, 88; burning described, 84; colour, 58; brick-earth, 57; cost of ditto, 87 ; brick-moulds, 70 ; bricks, number made per day, 84 ; size of bricks, 84; brick-yard, general arrangements, 59 ; clapper described, 73; clay digging, 80; clay mill described, 62 ; dressing- bench, 73 ; dressing described, 82 ; drying process, 81 ; flats described, 71 ; fuel for the kilns, 86 ; hovel described, 61, 72 ; kiln, 75 ; setting the kiln, 84 ; cost of setting and drawing kiln, 86 ; cost of labour, 90; cost of land, 87 ; machinery for pressing bricks, 74 ; cost of machinery, 88 ; cost of manufacture, 87 ; moulding de- scribed, 80 ; moulding sand, 68 ; moulding table, 68 ; plane de- scribed, 71; polished bricks, 83; pressed bricks, 83 ; tempering de- scribed, 67, 80; cost of tools," 90; wash mill described, 66. Oates's brickmaking machines, 196 ; cost of, 204; rate of production, 204. Ornamental brickwork, examples of, 6. Pallet moulding described, 29. Paving tiles, 42. Pressed bricks, defects of, 33. Prosser's method of making bricks, 32. Pug-mill described, 27. Red bricks, 21. Refractory clays, composition of, 15. Roofing tiles, 42. Sand, object of using, 122. Silica, use of, in brickmaking, 14. Slip kiln, 32 n. Slop moulding described, 28. Soil, term described, 27 n. Staffordshire brickmaking described, 95, 97 ; buildings described, 97 ; burning, 99; clay, described, 95; cost of manufacture, 101 ; drying, 99 ; firing, 109 ; illustrations, 102 ; moulding, 98, 103 j oven described, 100 ; plant described, 97; rate of production, 97 ; rental, 101 ; specific gravity of the bricks, when raw, dried, and burned, 99 ; tempering, 97 ; weight of the bricks, 99 ; arrangements of yard, 118. Staffordshire tile making, 105 ; class of tiles made, 95 ; drain tiles, 108 ; drying, 107 ; manner of drying, 111; firing, 113; illustra- tions to, described, 111 ; machines for making, 108 ; moulding, 107 ; moulding bench described, 111; pug-mill described. 106; setting described, 108; tempering, 106; weathering, 106. Stourbridge clay, 151. Striking the clay, 28. Suffolk, brickmaking in, 252 ; burn- ing, 253 ; clay, 253 ; dr .ing, 253 ; cost of manufacture, 254 ; mould- ing, 253 ; cost of plant, 254 ; tem- pering, 253. Table of analysis of different kinds of clay, 13 n. ; of analysis of Norton' coal, 117; of analysis of Staffordshire clays, 115; of the colour of Staffordshire clays, 116; of the cost of 1,000 bricks, "London make, 162 ; of the cost of London- made pantiles per 1,000, 187; of the cost and profit on 1,000 Not- tingham-made bricks, 91 ; of the cost and selling price of Stafford quarries, dust bricks, and roof tiles, 111 ; of the fusibility of Staffordshire clays, 116; of the price of fire-bricks of various manufactures, 18 ; showing the proportion of bases contained in Staffordshire clays, 116 ; of the relative value of different qualities of bricks Nottingham make, 91 ; of the selling price of London- made tiles, 187 ; of space required for each moulding-stool by either process, 37 ; of loss of weight in drying and burning, 99; of the strength of hand and machine- made bricks, 11. Taxes upon bricks, 6 ; repeal of the, 8. Tempering, 25 ; process described, Terra-cotta, early use of, 5. Minton's, 193 ; Roman 276 INDEX. process described, 193 , modern process described, 194. Tile-burning, 44, 255. Tile-kilns, construction of, 183, 189, 257 ; in Holland, 63. Tile-making in England, 42; in Holland, 52 ; in Staffordshire, 105 ; in London, 167. Tile-making machines, Ainslie's, 109; Hatcher's, 256; Page's, 233; White- head's, 234. Tile-moulding, 184. Tileries, London, 167 ; Staffordshire, 105. Tiles, encaustic, manufacture of, 189. Tiles, manufacture of, 42 ; schedule of duties on, 7 ; cost of manufac- ture, 186 ; manufacture of, in ^ Holland, 52. Tower of Babel, burnt bricks used in building, 1. Unsoiling, 22. Utrecht, principal seat of tile mar.u- facture in Holland, 54. Ventilating bricks, 35. Washing described, 24. Weathering, process of, 22. White bricks, 21. Whitehead's brickmaking machine 216 ; brick-pressing machine, 226 ; clay crushing and grinding mill, 212 ; perforated pug-mill, 214 ; tile-making machine, 234. Wilson's dry-clay brick machine 232. 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