CATGUT.

CATGUT.What is called catgut is made from the inner or lining membrane of the intestines of sheep. These are washed, soaked, scraped, and otherwise prepared, to render them even and clear; they are then soaked in a solution of pearlash to clear them from grease, twisted, exposed to the vapour of sulphur, polished by rubbing, and afterwards stretched and dried. Catgut is used not only for the strings of violins and other musical instruments, but also for what is called “clock-makers’ cord,” that is to say, for the bow by which the drill is turned, and for several other purposes. It is very strong, and does not easily get ragged, as would any hempen cord.

What is called catgut is made from the inner or lining membrane of the intestines of sheep. These are washed, soaked, scraped, and otherwise prepared, to render them even and clear; they are then soaked in a solution of pearlash to clear them from grease, twisted, exposed to the vapour of sulphur, polished by rubbing, and afterwards stretched and dried. Catgut is used not only for the strings of violins and other musical instruments, but also for what is called “clock-makers’ cord,” that is to say, for the bow by which the drill is turned, and for several other purposes. It is very strong, and does not easily get ragged, as would any hempen cord.

PAPER.FIG.1. SECTION OF RAG ENGINE, WITH DOUBLE ROLLER.This important article of civilisation is made from rags of various descriptions and qualities, according to the kind of paper to be made, the finest white paper being made of old clean linen rags, while brown paper is made of all sorts of old rope-yarns, sacking, &c., and some kinds of paper have a considerable amount of straw bleached and worked up in them. The rags are first sorted and cut up into small pieces; they are then beaten on a wire screen to separate all dust, and afterwards put into the washing-machine, through which a stream of water runs, and in which they are kneaded and torn by a broad wheel having iron wedges or knives fastened to its edge (fig. 1) or surface, which work as it is turned against knives of a similar description fastened to the bottom of the cistern. When the rags are thoroughly washed, and at the same time torn to a coarse pulp, it constitutes what the workmen call “half-stuff.” This is mixed with chloride of lime, and the machine again set in motion; this is for the purpose of bleaching the pulp; after this has been effected, more water is turned on, as in the first washing, and all the chloride of lime washed thoroughly away. The pulp is now either put into another machine of the same description which cuts sharper and finer, or else the same machine used at first is so screwed up as to cause the knives to come more closely together; in either case the rate of turning is greatly increased, so that the wheel turns at about 150 revolutions per minute, and completely grinds up the pulp till it is perfectly smooth: at this part of the process some “indigo” or “smalt” is added if the paper is to be of a blueish tint, as in “foolscap” paper. The “stuff” is now run off into a cistern ready for use. Paper is now nearly all made by machinery, in pieces of a certain width, but of an indefinite length, and is cut up into sheets afterwards by a “cutting machine.”FIG.2. PAPER-MAKING MACHINE.These machines (fig. 2) consist essentially of a vat,A, for the pulp, which flows out on to a bed of wire gauze,B B B, covered with felt, and bounded on each side by straps or deckles, and forming a circle or endless band by being stretched over a succession of rollers,C D E F G, which, by turning round continually, move its upper surface onwards and between other cylinders, which press out the superfluous moisture; it is then carried forward till it arrives at several pairs of large hollow cylinders,H H H, heated by means of steam which is passed through them, and which compress and at the same time thoroughly dry the paper, which comes from them as paper perfectly formed, and of any length that may be required. It is then glazed on the surface by the rollersI, and coiled on the cylinderL. Any name, device, or water-mark can be worked in the bed on to which the pulp flows, and which, being repeated at definite distances, appears on each sheet into which the paper is afterwards cut. The apparatus markedKis to conduct to the earth the electricity developed by the friction of the paper against the rollers. Beneath the bed of wire gauze, on which the pulp is laid is a cavity from which the air is pumped, and which causes the air to press upon the surface of the pulp, and force out a great deal of its moisture.FIG.3. SIZING MACHINE.If the paper has to be sized (which is the case in all “hard” papers) it has to pass through a process, the machinery of which is shown infig. 3.Ais a reservoir for size,Ba trough for the paper to dip into,Cthe reel of paper to be sized,Drollers to press out all superfluous size,Ea pulley to keep the paper on the stretch,F F Fa succession of hollow “drums,” to prolong the passage of the paper through the air of the drying-room, which is heated by the furnaceGand the tubesI I.H Hare openings to admit fresh air, andKopenings to allow the exit of the steam from the paper as it dries.Lis a series of rollers to glaze it.FIG.4. CUTTING MACHINE.The “cutting-machine” before referred to is represented atfig. 4.Ais a wheel upon which is fixed a plate with projections and screws for fixing the position of the arm attached to the linkB;Blink connecting the wheelAwith the lever-armG, and capable of adjustment by means of the plate attached to the wheelA, and the screwD;Da screw regulating the position of the rodB;Ethe drum by whose motion the web of the paper is carried forward.FIG.5. HAND PROCESS.But the process, as conducted by hand (fig. 5), will give a much better notion of how paper is formed from the pulp. A reservoir,A, is filled with pulp, which is supplied by a wheel in the boxB, to a strainerC, and passed to a vatD, and a man,E, takes in his hands a mould consisting of a shallow frame of wood of the size the sheet of paper is to be, having a bottom of fine wires laid side by side, and having wires crossing at intervals to keep them firm (the marks of these may be seen in any sheet of laid foolscap paper held up to the light); he dips this mould edgewise into the reservoir, and brings it up horizontally full of pulp; this he gently shakes, to make the pulp lie level and allow all superfluous water to drain through the wires. It is then handed to another manH, who has a sheet of flannel or felt spread out on a tableF G, on which the mould is inverted, and the sheet of pulp left on the flannel, which sucks up more of its moisture; over this is placed another piece of flannel, and then another sheet of pulp on it, and so on to the number of five or six dozenF, then the whole is put into a powerful press, and screwed down till all the water is squeezed out, when they are pretty firm, and are lifted out and hung on lines to dry, after which they are immersed in a cistern filled with thin size made by boiling clippings of skin in water (see “Glue and Size”), and having some alum dissolved in it—they are once more pressed and dried. What is called “hot-pressed” paper is pressed between smooth sheets of pasteboard, having a hot iron plate placed between every three or four dozen sheets of paper; this gives a smooth surface to the paper. The names, dates, and other marks seen on hand-made paper are formed by wires worked into the bottom of the mould, which, projecting, make the pulp thinner in those places. The water-mark of Bank-notes is made in the same way. More than half-a-million sterling is paid annually for duty upon paper—so vast is the consumption!

FIG.1. SECTION OF RAG ENGINE, WITH DOUBLE ROLLER.

This important article of civilisation is made from rags of various descriptions and qualities, according to the kind of paper to be made, the finest white paper being made of old clean linen rags, while brown paper is made of all sorts of old rope-yarns, sacking, &c., and some kinds of paper have a considerable amount of straw bleached and worked up in them. The rags are first sorted and cut up into small pieces; they are then beaten on a wire screen to separate all dust, and afterwards put into the washing-machine, through which a stream of water runs, and in which they are kneaded and torn by a broad wheel having iron wedges or knives fastened to its edge (fig. 1) or surface, which work as it is turned against knives of a similar description fastened to the bottom of the cistern. When the rags are thoroughly washed, and at the same time torn to a coarse pulp, it constitutes what the workmen call “half-stuff.” This is mixed with chloride of lime, and the machine again set in motion; this is for the purpose of bleaching the pulp; after this has been effected, more water is turned on, as in the first washing, and all the chloride of lime washed thoroughly away. The pulp is now either put into another machine of the same description which cuts sharper and finer, or else the same machine used at first is so screwed up as to cause the knives to come more closely together; in either case the rate of turning is greatly increased, so that the wheel turns at about 150 revolutions per minute, and completely grinds up the pulp till it is perfectly smooth: at this part of the process some “indigo” or “smalt” is added if the paper is to be of a blueish tint, as in “foolscap” paper. The “stuff” is now run off into a cistern ready for use. Paper is now nearly all made by machinery, in pieces of a certain width, but of an indefinite length, and is cut up into sheets afterwards by a “cutting machine.”

FIG.2. PAPER-MAKING MACHINE.

These machines (fig. 2) consist essentially of a vat,A, for the pulp, which flows out on to a bed of wire gauze,B B B, covered with felt, and bounded on each side by straps or deckles, and forming a circle or endless band by being stretched over a succession of rollers,C D E F G, which, by turning round continually, move its upper surface onwards and between other cylinders, which press out the superfluous moisture; it is then carried forward till it arrives at several pairs of large hollow cylinders,H H H, heated by means of steam which is passed through them, and which compress and at the same time thoroughly dry the paper, which comes from them as paper perfectly formed, and of any length that may be required. It is then glazed on the surface by the rollersI, and coiled on the cylinderL. Any name, device, or water-mark can be worked in the bed on to which the pulp flows, and which, being repeated at definite distances, appears on each sheet into which the paper is afterwards cut. The apparatus markedKis to conduct to the earth the electricity developed by the friction of the paper against the rollers. Beneath the bed of wire gauze, on which the pulp is laid is a cavity from which the air is pumped, and which causes the air to press upon the surface of the pulp, and force out a great deal of its moisture.

FIG.3. SIZING MACHINE.

If the paper has to be sized (which is the case in all “hard” papers) it has to pass through a process, the machinery of which is shown infig. 3.Ais a reservoir for size,Ba trough for the paper to dip into,Cthe reel of paper to be sized,Drollers to press out all superfluous size,Ea pulley to keep the paper on the stretch,F F Fa succession of hollow “drums,” to prolong the passage of the paper through the air of the drying-room, which is heated by the furnaceGand the tubesI I.H Hare openings to admit fresh air, andKopenings to allow the exit of the steam from the paper as it dries.Lis a series of rollers to glaze it.

FIG.4. CUTTING MACHINE.

The “cutting-machine” before referred to is represented atfig. 4.Ais a wheel upon which is fixed a plate with projections and screws for fixing the position of the arm attached to the linkB;Blink connecting the wheelAwith the lever-armG, and capable of adjustment by means of the plate attached to the wheelA, and the screwD;Da screw regulating the position of the rodB;Ethe drum by whose motion the web of the paper is carried forward.

FIG.5. HAND PROCESS.

But the process, as conducted by hand (fig. 5), will give a much better notion of how paper is formed from the pulp. A reservoir,A, is filled with pulp, which is supplied by a wheel in the boxB, to a strainerC, and passed to a vatD, and a man,E, takes in his hands a mould consisting of a shallow frame of wood of the size the sheet of paper is to be, having a bottom of fine wires laid side by side, and having wires crossing at intervals to keep them firm (the marks of these may be seen in any sheet of laid foolscap paper held up to the light); he dips this mould edgewise into the reservoir, and brings it up horizontally full of pulp; this he gently shakes, to make the pulp lie level and allow all superfluous water to drain through the wires. It is then handed to another manH, who has a sheet of flannel or felt spread out on a tableF G, on which the mould is inverted, and the sheet of pulp left on the flannel, which sucks up more of its moisture; over this is placed another piece of flannel, and then another sheet of pulp on it, and so on to the number of five or six dozenF, then the whole is put into a powerful press, and screwed down till all the water is squeezed out, when they are pretty firm, and are lifted out and hung on lines to dry, after which they are immersed in a cistern filled with thin size made by boiling clippings of skin in water (see “Glue and Size”), and having some alum dissolved in it—they are once more pressed and dried. What is called “hot-pressed” paper is pressed between smooth sheets of pasteboard, having a hot iron plate placed between every three or four dozen sheets of paper; this gives a smooth surface to the paper. The names, dates, and other marks seen on hand-made paper are formed by wires worked into the bottom of the mould, which, projecting, make the pulp thinner in those places. The water-mark of Bank-notes is made in the same way. More than half-a-million sterling is paid annually for duty upon paper—so vast is the consumption!

MALT.Barley is the grain generally chosen for producing malt, although others may be used. It is first soaked in cold water till it is softened; it is then spread out about two feet thick on the floor of the malt-house, where it begins to germinate, in the same manner as if sown in the earth; this is allowed to go on so far only till the first part of the root and stem make their appearance, in the form of a little bud and a fibre. During germination the malt gives out a poisonous gas called “carbonic acid,” and becomes warm, in fact it would become too warm and be injured, but it is kept stirred by means of wooden shovels from time to time, and the temperature ascertained by means of a thermometer. As the process of germination goes on, all the starchy matter naturally contained in the grain becomes changed into sugar, and the malt, when made, has a sweetish taste. As soon as the germination has proceeded to a certain extent it is stopped by drying; for this purpose the malt is put into a kiln and heated almost to scorching—if but slightly, it is called pale malt or “amber,” if more, “brown malt” or roasted malt. Malt, if kept dry, will remain a long time unchanged. It is used for producing beer and vinegar, and for “wash,” from which all the raw spirit used in England is distilled. Whiskey is also distilled in Scotland and Ireland from malt.Malt has the property of converting the starch of barley unmalted into sugar while in contact with it. For example, if barley were ground and boiling water poured on it, it would form a thick sort of paste, which is because it contains starch only; while malt treated in the same way, sinks to the bottom, and leaves a clear limpid “wort,” which can be strained off, because the starch is changed into sugar, which is soluble. Now, if equal parts of malt and ground barley be also treated in the same way, the malt very shortly converts the starch of the barley into sugar, and the result is the same as if all had been malt. This was once a matter of great importance to the brewers, who thereby saved the heavy duty imposed upon malt.

Barley is the grain generally chosen for producing malt, although others may be used. It is first soaked in cold water till it is softened; it is then spread out about two feet thick on the floor of the malt-house, where it begins to germinate, in the same manner as if sown in the earth; this is allowed to go on so far only till the first part of the root and stem make their appearance, in the form of a little bud and a fibre. During germination the malt gives out a poisonous gas called “carbonic acid,” and becomes warm, in fact it would become too warm and be injured, but it is kept stirred by means of wooden shovels from time to time, and the temperature ascertained by means of a thermometer. As the process of germination goes on, all the starchy matter naturally contained in the grain becomes changed into sugar, and the malt, when made, has a sweetish taste. As soon as the germination has proceeded to a certain extent it is stopped by drying; for this purpose the malt is put into a kiln and heated almost to scorching—if but slightly, it is called pale malt or “amber,” if more, “brown malt” or roasted malt. Malt, if kept dry, will remain a long time unchanged. It is used for producing beer and vinegar, and for “wash,” from which all the raw spirit used in England is distilled. Whiskey is also distilled in Scotland and Ireland from malt.

Malt has the property of converting the starch of barley unmalted into sugar while in contact with it. For example, if barley were ground and boiling water poured on it, it would form a thick sort of paste, which is because it contains starch only; while malt treated in the same way, sinks to the bottom, and leaves a clear limpid “wort,” which can be strained off, because the starch is changed into sugar, which is soluble. Now, if equal parts of malt and ground barley be also treated in the same way, the malt very shortly converts the starch of the barley into sugar, and the result is the same as if all had been malt. This was once a matter of great importance to the brewers, who thereby saved the heavy duty imposed upon malt.

CHOCOLATE AND COCOA.CHOCOLATE CRUSHING MACHINE.Chocolate and cocoa are made from the seeds or beans of theTheobroma Cacao. The fruit of this plant somewhat resembles a cucumber, and contains from twenty to thirty seeds; these are dried and packed for the market. They come to this country from the West Indies (Berbice and Demerara). The beans are roasted in an iron cylinder with holes to let out the vapour, &c.; when cool they are deprived of their husks, and then crushed by means of rollers turning on a flat slab, kept warm by stoves or steam. The seeds when crushed on the warm slab become almost liquid, owing to a kind of butter or concrete oil which they contain, and which melts by a gentle heat. When the seeds are rolled by the machine into a smooth paste, this is either put into a mould of tin and formed into squares and various other forms, or left rough as it is scraped from the slab (this is called “rock” cocoa). For chocolate it is mixed with sugar, and either dried and powdered, or made, as the cocoa, into paste. On the Continent it is flavoured with “vanilla.”

CHOCOLATE CRUSHING MACHINE.

Chocolate and cocoa are made from the seeds or beans of theTheobroma Cacao. The fruit of this plant somewhat resembles a cucumber, and contains from twenty to thirty seeds; these are dried and packed for the market. They come to this country from the West Indies (Berbice and Demerara). The beans are roasted in an iron cylinder with holes to let out the vapour, &c.; when cool they are deprived of their husks, and then crushed by means of rollers turning on a flat slab, kept warm by stoves or steam. The seeds when crushed on the warm slab become almost liquid, owing to a kind of butter or concrete oil which they contain, and which melts by a gentle heat. When the seeds are rolled by the machine into a smooth paste, this is either put into a mould of tin and formed into squares and various other forms, or left rough as it is scraped from the slab (this is called “rock” cocoa). For chocolate it is mixed with sugar, and either dried and powdered, or made, as the cocoa, into paste. On the Continent it is flavoured with “vanilla.”

STEEL.BESSEMER’S PROCESS.Steel is usually made by a process called “cementation.” Bars of the best Swedish or Russian iron, about six feet long, are placed in an iron box, the bottom of which is covered with a layer of charcoal powder; over the first row of iron bars some more charcoal is put, and then another row of iron bars, and so on till the box is full, when it is carefully closed and kept at a white heat for four or five days. When cold, the bars are found to be converted into steel, and, being rough and blistered on the surface, are called “blistered steel;” this is broken up, and the bars laid side by side and made hot in a forge, where they are welded together by the blows of a heavy hammer, and drawn or rolled out by machinery into bars of “fine steel.” Steel differs from iron in the closeness of its grain, in being very much “tougher,” and in having that very useful and peculiar property called “temper,” which is the power of hardening when suddenly cooled while red-hot. If a bar of steel as soft as iron be made of a bright red heat, and then suddenly plunged into cold water, it will be found to have become harder than any other metal (so hard, indeed, that it will scratch glass), and is as brittle and readily broken as flint or glass. If now a gentle heat be applied to it, this extreme hardness of temper gives way. For instance, if a piece of bright hard steel is held for a moment in the hollow of a clear fire, a pale straw color appears on its surface, it is now still very hard (but not so hard as before), and is fit for razors, surgeons’ instruments, &c; but if held in the fire a moment or two longer, it becomes of a bright golden yellow, and is fit for penknives, and other cutting instruments; held longer still, it becomes bright blue, and is fit for watch-springs, swords, and other purposes requiring great elasticity but no great hardness; if the heat be carried still further a brown tinge is seen, and it is now rather soft, but greatly harder than iron, and is still elastic; saws, coach-springs, and many other articles are made from steel at this temper. If the heat be carried on to redness, the steel would be quite soft when it had slowly cooled, but if suddenly cooled (as by being plunged into water) the original hard temper comes back again.Steel, like iron, may be cast, and cast-steel is one of its most useful forms, and much resembles “fine steel.” The mode of preparing cast-steel is to melt the “blistered steel” in a crucible, or earthen pot, and then run it into a mould: this forms an “ingot” of steel, which may be afterwards rolled or welded as the case may require.Steel may be drawn into very fine wire, or wrought into the most minute articles, as the springs and other parts of watches. It bears a very fine and bright polish, and does not rust or tarnish so easily as iron. It has lately been proposed to make heavy cannon of cast-steel, which is much tougher than either cast-iron or gun-metal.Fig. 1.Fig. 2.PERPENDICULAR SECTIONS OF CONVERTING VESSEL.FIG.3.OUTSIDE VIEW OF CONVERTING VESSEL.A process has lately been invented by Bessemer to supersede the long and laborious process of “puddling.” It consists essentially of transferring the melted iron into a vessel in which there are tubes inserted at the lower part, and through which air is forced at a great pressure, which bubbles up in streams through the melted metal, and, as it does so, unites with the carbon and sulphur of the iron, converting them into carbonic and sulphurous acids, and at the same time producing an increased heat, which is quite necessary to the success of the process, for as the iron becomes purer it also becomes more difficultly fusible, and would set into a solid mass, but that this greatly increased temperature keeps it fluid. This rising of temperature is similar to what takes place upon blowing a common fire with bellows; for the more air that is admitted to carbon raised to a very high temperature, the more rapidly does it combine with its oxygen, or, in other words, the more rapidly does it burn. So that, in this process of Bessemer’s contriving, the carbon of the iron acts as fuel to keep up the heat necessary to maintain its fusion, and at the same time, by being converted into carbonic acid, escapes in bubbles (like the bubbles which escape from soda-water), and this rapid production of gas in every part of the fused iron also assists in bringing about a thorough stirring-up and mixing together of all its parts. Reference to the accompanying diagrams will illustrate the working of the process. Infigs. 1and2,A Bare lower chambers,Cis the melted iron,Dis an upper chamber for melting scrap-iron, &c.,Einfig. 1andDinfig. 2are openings for the escape of gas and flame,F Fis an air-passage running all round and communicating byGwith the tuyere-holes shown atEinfig. 4,His the fire-brick lining to the furnace, andIthe tapping-hole through which the fluid iron is discharged. Infig. 3,Iis the tapping-hole,Kthe main air-tube leading from the blast-engine,L Lperpendicular tubes (markedGinfigs. 1and2) leading from circular air-passage to tuyere-holes,Mis an opening for the insertion of iron into the upper chamber, opposite to openingDinfig. 2, andNthe tap for regulating the blast;Oindicates the outer casing of wrought iron.When the process is carried only to a certain point, the result is a sort of semi-steel, which the inventor of the process expects will be a very useful article of commerce.FIG.4. HORIZONTAL SECTION OR PLAN OF CONVERTING VESSEL.During the bubbling up of the whole mass of iron and the extreme elevation of temperature caused by the union of the carbon of the impure iron with the oxygen of the air, the oxide of iron as fast as it forms fuses into a sort of glass, and this unites with the earthy matters of the impure iron and floats on the upper part as a flux, thus ridding the cast-iron of all its impurities, with no other fuel than that contained in the iron itself and the air.The accompanying illustration represents a horizontal section or plan of the converting vessel;Athe central chamber,Ba lining of fire-bricks,Cthe main air-tube,Dthe tapping-hole,Ethe tuyere-holes through which the air is forced into the melted iron to be purified,Fis the outside casing of wrought-iron.

BESSEMER’S PROCESS.

Steel is usually made by a process called “cementation.” Bars of the best Swedish or Russian iron, about six feet long, are placed in an iron box, the bottom of which is covered with a layer of charcoal powder; over the first row of iron bars some more charcoal is put, and then another row of iron bars, and so on till the box is full, when it is carefully closed and kept at a white heat for four or five days. When cold, the bars are found to be converted into steel, and, being rough and blistered on the surface, are called “blistered steel;” this is broken up, and the bars laid side by side and made hot in a forge, where they are welded together by the blows of a heavy hammer, and drawn or rolled out by machinery into bars of “fine steel.” Steel differs from iron in the closeness of its grain, in being very much “tougher,” and in having that very useful and peculiar property called “temper,” which is the power of hardening when suddenly cooled while red-hot. If a bar of steel as soft as iron be made of a bright red heat, and then suddenly plunged into cold water, it will be found to have become harder than any other metal (so hard, indeed, that it will scratch glass), and is as brittle and readily broken as flint or glass. If now a gentle heat be applied to it, this extreme hardness of temper gives way. For instance, if a piece of bright hard steel is held for a moment in the hollow of a clear fire, a pale straw color appears on its surface, it is now still very hard (but not so hard as before), and is fit for razors, surgeons’ instruments, &c; but if held in the fire a moment or two longer, it becomes of a bright golden yellow, and is fit for penknives, and other cutting instruments; held longer still, it becomes bright blue, and is fit for watch-springs, swords, and other purposes requiring great elasticity but no great hardness; if the heat be carried still further a brown tinge is seen, and it is now rather soft, but greatly harder than iron, and is still elastic; saws, coach-springs, and many other articles are made from steel at this temper. If the heat be carried on to redness, the steel would be quite soft when it had slowly cooled, but if suddenly cooled (as by being plunged into water) the original hard temper comes back again.

Steel, like iron, may be cast, and cast-steel is one of its most useful forms, and much resembles “fine steel.” The mode of preparing cast-steel is to melt the “blistered steel” in a crucible, or earthen pot, and then run it into a mould: this forms an “ingot” of steel, which may be afterwards rolled or welded as the case may require.

Steel may be drawn into very fine wire, or wrought into the most minute articles, as the springs and other parts of watches. It bears a very fine and bright polish, and does not rust or tarnish so easily as iron. It has lately been proposed to make heavy cannon of cast-steel, which is much tougher than either cast-iron or gun-metal.

Fig. 1.Fig. 2.PERPENDICULAR SECTIONS OF CONVERTING VESSEL.

PERPENDICULAR SECTIONS OF CONVERTING VESSEL.

FIG.3.OUTSIDE VIEW OF CONVERTING VESSEL.

A process has lately been invented by Bessemer to supersede the long and laborious process of “puddling.” It consists essentially of transferring the melted iron into a vessel in which there are tubes inserted at the lower part, and through which air is forced at a great pressure, which bubbles up in streams through the melted metal, and, as it does so, unites with the carbon and sulphur of the iron, converting them into carbonic and sulphurous acids, and at the same time producing an increased heat, which is quite necessary to the success of the process, for as the iron becomes purer it also becomes more difficultly fusible, and would set into a solid mass, but that this greatly increased temperature keeps it fluid. This rising of temperature is similar to what takes place upon blowing a common fire with bellows; for the more air that is admitted to carbon raised to a very high temperature, the more rapidly does it combine with its oxygen, or, in other words, the more rapidly does it burn. So that, in this process of Bessemer’s contriving, the carbon of the iron acts as fuel to keep up the heat necessary to maintain its fusion, and at the same time, by being converted into carbonic acid, escapes in bubbles (like the bubbles which escape from soda-water), and this rapid production of gas in every part of the fused iron also assists in bringing about a thorough stirring-up and mixing together of all its parts. Reference to the accompanying diagrams will illustrate the working of the process. Infigs. 1and2,A Bare lower chambers,Cis the melted iron,Dis an upper chamber for melting scrap-iron, &c.,Einfig. 1andDinfig. 2are openings for the escape of gas and flame,F Fis an air-passage running all round and communicating byGwith the tuyere-holes shown atEinfig. 4,His the fire-brick lining to the furnace, andIthe tapping-hole through which the fluid iron is discharged. Infig. 3,Iis the tapping-hole,Kthe main air-tube leading from the blast-engine,L Lperpendicular tubes (markedGinfigs. 1and2) leading from circular air-passage to tuyere-holes,Mis an opening for the insertion of iron into the upper chamber, opposite to openingDinfig. 2, andNthe tap for regulating the blast;Oindicates the outer casing of wrought iron.

When the process is carried only to a certain point, the result is a sort of semi-steel, which the inventor of the process expects will be a very useful article of commerce.

FIG.4. HORIZONTAL SECTION OR PLAN OF CONVERTING VESSEL.

During the bubbling up of the whole mass of iron and the extreme elevation of temperature caused by the union of the carbon of the impure iron with the oxygen of the air, the oxide of iron as fast as it forms fuses into a sort of glass, and this unites with the earthy matters of the impure iron and floats on the upper part as a flux, thus ridding the cast-iron of all its impurities, with no other fuel than that contained in the iron itself and the air.

The accompanying illustration represents a horizontal section or plan of the converting vessel;Athe central chamber,Ba lining of fire-bricks,Cthe main air-tube,Dthe tapping-hole,Ethe tuyere-holes through which the air is forced into the melted iron to be purified,Fis the outside casing of wrought-iron.

TIN-PLATE, AND GALVANISED IRON.What is usually called tin is, in fact, sheet-iron coated with tin, and of this tin-plate, kettles, saucepans, &c., are made. The art of coating iron plates with tin has been practised in England hardly more than one hundred years. The very best soft iron is used for the purpose of being tinned. It is rolled out into thin plates, which are cut by shears into squares of usually thirteen inches long and ten broad, these plates are dipped into weak acid to clean their surfaces, then rubbed with sand, and finally washed; they are next dipped into melted tallow, which preserves their surfaces bright till they can be used. They are then immersed in melted tin, which has its surface covered with melted tallow, to keep it from being converted into oxide. When the plates have remained for a short time in the tin, they are removed, and the superfluous tin is wiped from the lower edge with a brush made of hemp, and then cleaned from the grease with dry bran. The objects gained by coating iron with tin are, increased beauty of appearance (for when tinned ware is kept bright, it has almost the color of silver), and a protection to keep the surface from rusting, and consequently being corroded into holes.Copper and brass vessels are tinned inside, to prevent the formation of that poisonous substance called verdigris. The mode of tinning them is as follows:—They are cleaned inside by means of vitriol, and then made hot, fine grain-tin and a little rosin being put into them, and turned about and brushed over the surface with a ball of tow: by this means, the tin is equally spread over the inner surface of the vessel.Tin-tacks, buckles, and other small articles, receive a coating of tin by being put into an earthen pot together with some grain-tin and a substance called “sal ammoniac,” and the pot being heated over a fire sufficiently to melt the tin, is then shaken up till the articles inside have received a coating of tin.Iron plates have lately been coated with melted zinc instead of tin, and the surface thus covered enables them to be used for various purposes and in situations where they are exposed to the action of the weather, as on housetops, &c. The plates, thus treated, are called “galvanised iron,” and they are generally used in a corrugated form. They withstand the action of the weather very much better than simple iron plates would, for the latter would be very soon eaten into holes from rusting.

What is usually called tin is, in fact, sheet-iron coated with tin, and of this tin-plate, kettles, saucepans, &c., are made. The art of coating iron plates with tin has been practised in England hardly more than one hundred years. The very best soft iron is used for the purpose of being tinned. It is rolled out into thin plates, which are cut by shears into squares of usually thirteen inches long and ten broad, these plates are dipped into weak acid to clean their surfaces, then rubbed with sand, and finally washed; they are next dipped into melted tallow, which preserves their surfaces bright till they can be used. They are then immersed in melted tin, which has its surface covered with melted tallow, to keep it from being converted into oxide. When the plates have remained for a short time in the tin, they are removed, and the superfluous tin is wiped from the lower edge with a brush made of hemp, and then cleaned from the grease with dry bran. The objects gained by coating iron with tin are, increased beauty of appearance (for when tinned ware is kept bright, it has almost the color of silver), and a protection to keep the surface from rusting, and consequently being corroded into holes.

Copper and brass vessels are tinned inside, to prevent the formation of that poisonous substance called verdigris. The mode of tinning them is as follows:—They are cleaned inside by means of vitriol, and then made hot, fine grain-tin and a little rosin being put into them, and turned about and brushed over the surface with a ball of tow: by this means, the tin is equally spread over the inner surface of the vessel.

Tin-tacks, buckles, and other small articles, receive a coating of tin by being put into an earthen pot together with some grain-tin and a substance called “sal ammoniac,” and the pot being heated over a fire sufficiently to melt the tin, is then shaken up till the articles inside have received a coating of tin.

Iron plates have lately been coated with melted zinc instead of tin, and the surface thus covered enables them to be used for various purposes and in situations where they are exposed to the action of the weather, as on housetops, &c. The plates, thus treated, are called “galvanised iron,” and they are generally used in a corrugated form. They withstand the action of the weather very much better than simple iron plates would, for the latter would be very soon eaten into holes from rusting.

GLASS.This most useful and elegant material—now an article of almost universal application, in various forms—is made on a very large scale by fusing together sea-sand and alkali (either potash, soda, or lime), and, in the case of “crystal,” or “flint-glass,” oxide of lead. The following is about the composition of the chief kinds of glass in use:—FLINT GLASS.PARTS.PLATE GLASS.PARTS.Pure white sea-sand52Pure white sand55Potash14Soda35Oxide of lead34Nitre8Lime2100100CROWN GLASS.PARTS.GREEN BOTTLE GLASS.PARTS.Fine white sand63Sea-sand80Chalk7Salt10Soda30Lime10100100Flint-glass or “crystal” is very heavy, moderately soft (being easily cut with a file), and very bright and white. It is used for all table-glass, as decanters, wine-glasses, &c., and for the drops or lustres of chandeliers. Plate-glass is that kind of glass now in such general use for shop-windows, looking-glasses, &c. It is cast on flat iron tables, and rolled out to the sizes required, then cut and polished by machinery. In the rough state it is called “rough plate,” and is the substance used in the Crystal Palace, and has of late become almost a substitute for ground glass, which is simply ordinary glass ground or roughened on the surface by means of sand, so that it will admit light and yet not allow objects to be seen through it. Crown-glass is the ordinary “window-glass.” It is made in great circular pieces (see “Glass-blowing”), and cut up into the sizes required. Crown or window-glass made some years back, had a disagreeable tinge of green, which has been removed in modern glass by the addition of a minute quantity of oxide of manganese.(‡ Overhead Diagram Of Furnace.)FIG.1.The ingredients to be made into glass (of whatever kind it may be) are thoroughly mixed together and thrown a little at a time into large crucibles or melting-pots placed in a circle (A A,fig. 1) in a furnace resting on buttresses (B B,fig. 1), and heated to whiteness by means of a fire in the centre,C, blown by a blowing machine, the tube of which is seen atD. This furnace is shown in perspective infig. 2. The ingredients melt and sink down into a clear fluid, throwing up a scum, which is removed from time to time. This clear glass in the fused state is now kept at a white heat till all air-bubbles have disappeared; the heat is then lowered to a bright redness, when the glass assumes a consistence and ductility suitable to the purposes of the glass blower.(‡ Exterior View Of Furnace.)FIG.2.Artificial gems are all but varieties of glass. What is called “paste,” “French diamonds,” &c., are glasses of peculiar brilliancy, well cut and polished. Garnets, emeralds, and other precious stones are imitated by coloring the “paste” with various substances, chiefly metallic oxides, as oxide of cobalt, which produces a blue color, oxide of copper a red, and oxide of chromium a green color, &c.Glass is used for a variety of purposes besides the one great purpose of admitting light to houses while air and damp are excluded. It furnishes an immense variety of beautiful and useful articles in the form of drinking-vessels, vases, chandeliers, &c., and to the chemist and manufacturer generally, it is invaluable, for vessels of glass thoroughly resist the action of all acids (with the exception of the hydrofluoric) and nearly every other substance. It stands a considerable heat, and if made equal in substance and rather thin, will not easily crack by sudden alterations of temperature. Without glass, microscopes, telescopes, cameras, barometers and thermometers—upon which some of our best and most useful knowledge and some very beautiful results of chemical action depend—could hardly have been constructed.

This most useful and elegant material—now an article of almost universal application, in various forms—is made on a very large scale by fusing together sea-sand and alkali (either potash, soda, or lime), and, in the case of “crystal,” or “flint-glass,” oxide of lead. The following is about the composition of the chief kinds of glass in use:—

FLINT GLASS.PARTS.PLATE GLASS.PARTS.Pure white sea-sand52Pure white sand55Potash14Soda35Oxide of lead34Nitre8Lime2100100CROWN GLASS.PARTS.GREEN BOTTLE GLASS.PARTS.Fine white sand63Sea-sand80Chalk7Salt10Soda30Lime10100100

Flint-glass or “crystal” is very heavy, moderately soft (being easily cut with a file), and very bright and white. It is used for all table-glass, as decanters, wine-glasses, &c., and for the drops or lustres of chandeliers. Plate-glass is that kind of glass now in such general use for shop-windows, looking-glasses, &c. It is cast on flat iron tables, and rolled out to the sizes required, then cut and polished by machinery. In the rough state it is called “rough plate,” and is the substance used in the Crystal Palace, and has of late become almost a substitute for ground glass, which is simply ordinary glass ground or roughened on the surface by means of sand, so that it will admit light and yet not allow objects to be seen through it. Crown-glass is the ordinary “window-glass.” It is made in great circular pieces (see “Glass-blowing”), and cut up into the sizes required. Crown or window-glass made some years back, had a disagreeable tinge of green, which has been removed in modern glass by the addition of a minute quantity of oxide of manganese.

(‡ Overhead Diagram Of Furnace.)FIG.1.

FIG.1.

The ingredients to be made into glass (of whatever kind it may be) are thoroughly mixed together and thrown a little at a time into large crucibles or melting-pots placed in a circle (A A,fig. 1) in a furnace resting on buttresses (B B,fig. 1), and heated to whiteness by means of a fire in the centre,C, blown by a blowing machine, the tube of which is seen atD. This furnace is shown in perspective infig. 2. The ingredients melt and sink down into a clear fluid, throwing up a scum, which is removed from time to time. This clear glass in the fused state is now kept at a white heat till all air-bubbles have disappeared; the heat is then lowered to a bright redness, when the glass assumes a consistence and ductility suitable to the purposes of the glass blower.

(‡ Exterior View Of Furnace.)FIG.2.

FIG.2.

Artificial gems are all but varieties of glass. What is called “paste,” “French diamonds,” &c., are glasses of peculiar brilliancy, well cut and polished. Garnets, emeralds, and other precious stones are imitated by coloring the “paste” with various substances, chiefly metallic oxides, as oxide of cobalt, which produces a blue color, oxide of copper a red, and oxide of chromium a green color, &c.

Glass is used for a variety of purposes besides the one great purpose of admitting light to houses while air and damp are excluded. It furnishes an immense variety of beautiful and useful articles in the form of drinking-vessels, vases, chandeliers, &c., and to the chemist and manufacturer generally, it is invaluable, for vessels of glass thoroughly resist the action of all acids (with the exception of the hydrofluoric) and nearly every other substance. It stands a considerable heat, and if made equal in substance and rather thin, will not easily crack by sudden alterations of temperature. Without glass, microscopes, telescopes, cameras, barometers and thermometers—upon which some of our best and most useful knowledge and some very beautiful results of chemical action depend—could hardly have been constructed.

SODA-WATER.Soda-water was formerly prepared by the ordinary chemist, but since it has become so general a beverage has been made a separate branch of chemical manufacture. Soda-water consists of a very weak solution of carbonate of soda, holding a large quantity of carbonic acid in solution, for water has the property of absorbing a certain quantity of carbonic acid, and this quantity is increased in proportion to the pressure exerted on the water. This pressure is secured in the first place by machinery, and afterwards maintained by the bottle being closely corked and the cork fastened in by means of wire.FIG.1. SODA-WATER APPARATUS.Infig. 1there is an illustration of the machinery used. It consists of a small vessel holding sulphuric acid, attached to another vessel containing chalk and water kept constantly stirred by a small windlass passing through a hole in the top, and working air-tight. When some of the sulphuric acid is allowed to run into the vessel holding the chalk an effervescence takes place, and a rapid extrication of carbonic acid; this is conducted by a tube to a gas-holder as a store. A tube leads from this gas-holder into a sort of air-pump, and a man, by turning a windlass, not only works this and thereby forces a certain quantity of gas into another vessel of copper (plated with silver inside), but turns this vessel itself rapidly round. In this vessel the solution of carbonate of soda is placed, and is agitated under pressure with the carbonic acid thus forced into it, and which it rapidly absorbs. From this vessel it is drawn off into bottles, which are adroitly corked before much of the carbonic acid can escape, and then wired down, a fresh supply of solution of soda and carbonic acid being constantly introduced. Potash-water and Carrara water are made in the same way, using potash in the former, and chalk in the latter, instead of soda.(‡ Soda-Water Bottle.)FIG.2.The form of a soda-water bottle is shown infig. 2; it is made of very thick glass, that it may resist the outward pressure of the carbonic acid, and so formed that it cannot stand on its bottom, and when laid on its side the bubble of air shall rise up to the middle of the bottle and not to the cork, or else it would escape through the cork before long, however nicely it may be fitted.(‡ Dispensing Bottle.)FIG.3.Fig. 3is a convenient vessel for holding about a quart of soda-water or any other effervescing drink, all of which is not at once required. A tube passes from the top to nearly the bottom of the vessel, and when this is filled with aerated water, the expansive power of the carbonic acid forces the water up this tube and out of the spout when the handle is depressed and the tap opened, and when sufficient is obtained, the tap can be immediately closed.A very convenient apparatus called a “Gasogene” has lately been constructed. It consists of a double vessel, into the upper part of which a solution of any kind—wine and water, or even plain water—is put, to be saturated with carbonic acid or “aerated,” and into the lower one some carbonate of soda and tartaric acid. A tube leads from this lower to the top of the upper vessel, which screws on and off. By shaking the apparatus when thus charged and screwed together, some of the liquid descends through the tube into the lower vessel and moistens the soda and acid, which therefore act on each other, and cause carbonic acid to be disengaged; this, rising up through the tube (which is perforated with small holes at the upper part), disperses itself through the liquid in small bubbles, and causes sufficient pressure to enable the liquid to absorb it, which therefore effervesces when drawn off by the tap and this pressure removed.

Soda-water was formerly prepared by the ordinary chemist, but since it has become so general a beverage has been made a separate branch of chemical manufacture. Soda-water consists of a very weak solution of carbonate of soda, holding a large quantity of carbonic acid in solution, for water has the property of absorbing a certain quantity of carbonic acid, and this quantity is increased in proportion to the pressure exerted on the water. This pressure is secured in the first place by machinery, and afterwards maintained by the bottle being closely corked and the cork fastened in by means of wire.

FIG.1. SODA-WATER APPARATUS.

Infig. 1there is an illustration of the machinery used. It consists of a small vessel holding sulphuric acid, attached to another vessel containing chalk and water kept constantly stirred by a small windlass passing through a hole in the top, and working air-tight. When some of the sulphuric acid is allowed to run into the vessel holding the chalk an effervescence takes place, and a rapid extrication of carbonic acid; this is conducted by a tube to a gas-holder as a store. A tube leads from this gas-holder into a sort of air-pump, and a man, by turning a windlass, not only works this and thereby forces a certain quantity of gas into another vessel of copper (plated with silver inside), but turns this vessel itself rapidly round. In this vessel the solution of carbonate of soda is placed, and is agitated under pressure with the carbonic acid thus forced into it, and which it rapidly absorbs. From this vessel it is drawn off into bottles, which are adroitly corked before much of the carbonic acid can escape, and then wired down, a fresh supply of solution of soda and carbonic acid being constantly introduced. Potash-water and Carrara water are made in the same way, using potash in the former, and chalk in the latter, instead of soda.

(‡ Soda-Water Bottle.)FIG.2.

FIG.2.

The form of a soda-water bottle is shown infig. 2; it is made of very thick glass, that it may resist the outward pressure of the carbonic acid, and so formed that it cannot stand on its bottom, and when laid on its side the bubble of air shall rise up to the middle of the bottle and not to the cork, or else it would escape through the cork before long, however nicely it may be fitted.

(‡ Dispensing Bottle.)FIG.3.

FIG.3.

Fig. 3is a convenient vessel for holding about a quart of soda-water or any other effervescing drink, all of which is not at once required. A tube passes from the top to nearly the bottom of the vessel, and when this is filled with aerated water, the expansive power of the carbonic acid forces the water up this tube and out of the spout when the handle is depressed and the tap opened, and when sufficient is obtained, the tap can be immediately closed.

A very convenient apparatus called a “Gasogene” has lately been constructed. It consists of a double vessel, into the upper part of which a solution of any kind—wine and water, or even plain water—is put, to be saturated with carbonic acid or “aerated,” and into the lower one some carbonate of soda and tartaric acid. A tube leads from this lower to the top of the upper vessel, which screws on and off. By shaking the apparatus when thus charged and screwed together, some of the liquid descends through the tube into the lower vessel and moistens the soda and acid, which therefore act on each other, and cause carbonic acid to be disengaged; this, rising up through the tube (which is perforated with small holes at the upper part), disperses itself through the liquid in small bubbles, and causes sufficient pressure to enable the liquid to absorb it, which therefore effervesces when drawn off by the tap and this pressure removed.

COAL-TAR NAPTHA.This is distilled from the coal-tar produced at the gas-house, the residuum being pitch, and it has a very offensive smell. It is in demand as a solvent for India-rubber, and also for use in lamps so constructed as to require no wick, for naptha is very volatile, and the vapour is burnt as it rises.

This is distilled from the coal-tar produced at the gas-house, the residuum being pitch, and it has a very offensive smell. It is in demand as a solvent for India-rubber, and also for use in lamps so constructed as to require no wick, for naptha is very volatile, and the vapour is burnt as it rises.

WOOD NAPTHA, OR PYROXYLIC SPIRIT.This is often called wood spirit, and is procured from the tar resulting from the distillation of wood for wood vinegar or pyroligneous acid. It is colorless, without the disagreeable odour of coal-tar naptha, and very inflammable, burning without smoke, very much in the manner of spirits of wine. It is used in varnish-making, and also for burning in lamps where heat and not light is required.

This is often called wood spirit, and is procured from the tar resulting from the distillation of wood for wood vinegar or pyroligneous acid. It is colorless, without the disagreeable odour of coal-tar naptha, and very inflammable, burning without smoke, very much in the manner of spirits of wine. It is used in varnish-making, and also for burning in lamps where heat and not light is required.

PRODUCTS OF SKILLED LABOUR.POTTERY.(‡ Pottery Workers.)STAMPERS.FLINT MILL.The art of making vessels of earth is one of the oldest of all arts; the “potter’s wheel” is frequently named in Scripture, and pottery is found in all the remains of ancient nations. Earthenware is made from a mixture of clay and powdered flints; the clay is freed from all its coarser parts by being stirred with water and drawn off after the gross matters have settled; the fluid is then allowed at leisure to let fall the pure clay which was mixed with it, and is then fit for use. The flints are made red-hot, and in that state thrown into cold water, which makes them so brittle that they can be easily broken up by the “stampers,” which are perpendicular pieces of iron made to rise and fall with great force; the flints are then ground in a mill to a powder, which is treated in the same way that the clay was. When these two earths are mixed in proper proportions, and beaten together while moist, they form a substance of the consistence of putty, a lump of which is thrown into the centre of a piece of board turned by means of a wheel and treadle; while turning round, it is moulded by the hands into a rough outline of the vessel required, and afterwards put aside to dry till it becomes of such hardness, that it can be easily turned in a common lathe, and formed into the cup, jug or whatever else it may be intended for. This is then baked in a “kiln” or oven so contrived that it shall make it red-hot, and keep it so for about two days. If it has to be ornamented with a design-such, for instance, as the “willow pattern”—a number of prints on tissue paper of the subject required are kept ready, and one of these is stuck on to the vessel with the printed side next to the clay, and rubbed smoothly on to it; after a little time the paper is washed off with water, and the pattern is left on the vessel. The next process is that of glazing; this is done by dipping the vessel into a mixture generally made of ground flints and oxide of lead made into a thin fluid with water; when the glazing is dry the vessel is once more put into the kiln, and made red-hot, when the glazing-mixture on the surface melts into a smooth glass. Different colours are given to the pattern by mixing certain metallic substances with the ink used in printing. The handles, spouts, and other projecting parts are fixed on after turning, and before the ware is put into the kiln. Many kinds of pottery are not turned at all, but made in a mould by being squeezed forcibly into it; this is the case when the article to be produced is octagonal, or possessed of any form not round, and therefore not to be produced by turning, and when the surface has a pattern or figures standing out in relief. Some of these are made by filling shallow moulds with the clay, and, while moist, affixing them to the surface, but the handles of common ware are made by forcing some of the clay through a hole of the required form, so that it comes out in long strips or ribands, which are cut up into lengths, bent into the proper form, and stuck on to the ware, some softer clay being smeared round the joint—the whole, when baked in the kiln, becoming hard and strong.Earthenware is often made to possess some color throughout, as drab, yellow, brown, or black. These tints are produced by admixture of different kinds of clay and oxides in various proportions, oxide of iron generally giving a red or chocolate color, and oxide of manganese a drab, brown, or black color, according to the proportion used.Figures, busts, and many other articles, both for ornament and utility, are made of porcelain by casting, and are produced by filling hollow casts of plaster of Paris with the materials for porcelain, mixed with water to the consistence of cream—this is called “slip,”—and when the hollow cast is filled the porous plaster absorbs most of the moisture from the portion of liquid “slip” next to it, so that, after a time, what remains fluid being poured out, there is found a coating or lining of porcelain mixture of considerable thickness adhering to the interior of the mould too solid to be poured out; the whole is then set in a warm place to dry, and as the porcelain shrinks as it dries, it separates itself from the mould—which, being made of several pieces fastened together, is taken apart without injuring the cast; after it has thoroughly dried it is baked in a kiln or furnace. This is called “Biscuit porcelain.”

(‡ Pottery Workers.)

STAMPERS.

FLINT MILL.

The art of making vessels of earth is one of the oldest of all arts; the “potter’s wheel” is frequently named in Scripture, and pottery is found in all the remains of ancient nations. Earthenware is made from a mixture of clay and powdered flints; the clay is freed from all its coarser parts by being stirred with water and drawn off after the gross matters have settled; the fluid is then allowed at leisure to let fall the pure clay which was mixed with it, and is then fit for use. The flints are made red-hot, and in that state thrown into cold water, which makes them so brittle that they can be easily broken up by the “stampers,” which are perpendicular pieces of iron made to rise and fall with great force; the flints are then ground in a mill to a powder, which is treated in the same way that the clay was. When these two earths are mixed in proper proportions, and beaten together while moist, they form a substance of the consistence of putty, a lump of which is thrown into the centre of a piece of board turned by means of a wheel and treadle; while turning round, it is moulded by the hands into a rough outline of the vessel required, and afterwards put aside to dry till it becomes of such hardness, that it can be easily turned in a common lathe, and formed into the cup, jug or whatever else it may be intended for. This is then baked in a “kiln” or oven so contrived that it shall make it red-hot, and keep it so for about two days. If it has to be ornamented with a design-such, for instance, as the “willow pattern”—a number of prints on tissue paper of the subject required are kept ready, and one of these is stuck on to the vessel with the printed side next to the clay, and rubbed smoothly on to it; after a little time the paper is washed off with water, and the pattern is left on the vessel. The next process is that of glazing; this is done by dipping the vessel into a mixture generally made of ground flints and oxide of lead made into a thin fluid with water; when the glazing is dry the vessel is once more put into the kiln, and made red-hot, when the glazing-mixture on the surface melts into a smooth glass. Different colours are given to the pattern by mixing certain metallic substances with the ink used in printing. The handles, spouts, and other projecting parts are fixed on after turning, and before the ware is put into the kiln. Many kinds of pottery are not turned at all, but made in a mould by being squeezed forcibly into it; this is the case when the article to be produced is octagonal, or possessed of any form not round, and therefore not to be produced by turning, and when the surface has a pattern or figures standing out in relief. Some of these are made by filling shallow moulds with the clay, and, while moist, affixing them to the surface, but the handles of common ware are made by forcing some of the clay through a hole of the required form, so that it comes out in long strips or ribands, which are cut up into lengths, bent into the proper form, and stuck on to the ware, some softer clay being smeared round the joint—the whole, when baked in the kiln, becoming hard and strong.

Earthenware is often made to possess some color throughout, as drab, yellow, brown, or black. These tints are produced by admixture of different kinds of clay and oxides in various proportions, oxide of iron generally giving a red or chocolate color, and oxide of manganese a drab, brown, or black color, according to the proportion used.

Figures, busts, and many other articles, both for ornament and utility, are made of porcelain by casting, and are produced by filling hollow casts of plaster of Paris with the materials for porcelain, mixed with water to the consistence of cream—this is called “slip,”—and when the hollow cast is filled the porous plaster absorbs most of the moisture from the portion of liquid “slip” next to it, so that, after a time, what remains fluid being poured out, there is found a coating or lining of porcelain mixture of considerable thickness adhering to the interior of the mould too solid to be poured out; the whole is then set in a warm place to dry, and as the porcelain shrinks as it dries, it separates itself from the mould—which, being made of several pieces fastened together, is taken apart without injuring the cast; after it has thoroughly dried it is baked in a kiln or furnace. This is called “Biscuit porcelain.”

BRICKS AND TILES.PUG MILL.STOOL, OR WORKING SHED.BARROW FOR WET BRICKS.BARROW FOR DRY BRICKS.Bricks are made of clay mixed with sand or ashes. The brick-field is first covered with either of these to the depth of an inch or two, and is well dug in and turned about during several weeks; when the bricks are to be made, the mixture is put into a “pug mill;” this is a large tub having an upright iron bar passing up from the bottom, and having several broad iron blades fixed to its sides at the part which is in the tub; at the top there is a cross-bar of wood, to which a horse is harnessed; the horse, when driven round in a circle, turns the upright iron bar and consequently the iron blades. Into this tub the clay and ashes are now put, a little at a time, and as the horse goes round they are thoroughly mixed together; a man takes pieces of this clay of the proper size, and hands them to another who stands before a table in the shed, and has a mould before him; this consists of a piece of wood with sides of the size of the brick, which is always ten inches long, five broad, and three thick, before burning. The sides of this mould can be turned up and down; they are now put up, and the piece of clay forced into the mould and scraped off even at the top, the sides are put down, and the brick placed carefully on a barrow, which when filled is wheeled off by another man, and its contents arranged on the ground in long lines having a small space between each brick, that they may not stick together and the air may dry them. Long rows of these bricks are formed one on the top of the other, for four or five deep, and are changed in their position from time to time till they are quite dry and hard; they are now ready to be burnt. This is done made by placing the bricks in long rows, with narrow spaces between each row which are filled with straw or twigs of wood and cinders (these cinders are got from the ashes when they are sifted before mixing with the clay); the spaces being filled they are covered with other bricks, and then the straw, &c., is lighted. Layer after layer of bricks are next built up around the fire, so that the heat shall be well kept in, and in this way the bricks are gradually baked till they are quite hard and fit for use.BURNING BRICKS.Tiles are the same as bricks, but of a different form, being flat, and having two holes in them to receive nails. These are used to form the roofs of houses, and are nailed on to the rafters, each layer overlapping the one below it, so that the rain falling on the sloping roof shall run from the top to the bottom without coming through.Bricks have lately been made with perforations through them, which is done by having a mould with a number of iron rods projecting from its bottom, so that when the clay is forced on them they pass right through it, and leave holes. The objects gained by this are two; in the first place, the bricks are much lighter, a great advantage in building, and in the second place they do not get so much out of form in burning, as there is no great substance between the holes, and therefore the shrinking takes place more evenly. Most of these bricks are of a light straw color, and are used for facing. They are mixed with a quantity of chalk, which is worked up with the clay, and are not baked at such a heat as would burn it into lime.MIXING CHALK.

PUG MILL.

STOOL, OR WORKING SHED.

BARROW FOR WET BRICKS.BARROW FOR DRY BRICKS.

BARROW FOR WET BRICKS.

BARROW FOR DRY BRICKS.

Bricks are made of clay mixed with sand or ashes. The brick-field is first covered with either of these to the depth of an inch or two, and is well dug in and turned about during several weeks; when the bricks are to be made, the mixture is put into a “pug mill;” this is a large tub having an upright iron bar passing up from the bottom, and having several broad iron blades fixed to its sides at the part which is in the tub; at the top there is a cross-bar of wood, to which a horse is harnessed; the horse, when driven round in a circle, turns the upright iron bar and consequently the iron blades. Into this tub the clay and ashes are now put, a little at a time, and as the horse goes round they are thoroughly mixed together; a man takes pieces of this clay of the proper size, and hands them to another who stands before a table in the shed, and has a mould before him; this consists of a piece of wood with sides of the size of the brick, which is always ten inches long, five broad, and three thick, before burning. The sides of this mould can be turned up and down; they are now put up, and the piece of clay forced into the mould and scraped off even at the top, the sides are put down, and the brick placed carefully on a barrow, which when filled is wheeled off by another man, and its contents arranged on the ground in long lines having a small space between each brick, that they may not stick together and the air may dry them. Long rows of these bricks are formed one on the top of the other, for four or five deep, and are changed in their position from time to time till they are quite dry and hard; they are now ready to be burnt. This is done made by placing the bricks in long rows, with narrow spaces between each row which are filled with straw or twigs of wood and cinders (these cinders are got from the ashes when they are sifted before mixing with the clay); the spaces being filled they are covered with other bricks, and then the straw, &c., is lighted. Layer after layer of bricks are next built up around the fire, so that the heat shall be well kept in, and in this way the bricks are gradually baked till they are quite hard and fit for use.

BURNING BRICKS.

Tiles are the same as bricks, but of a different form, being flat, and having two holes in them to receive nails. These are used to form the roofs of houses, and are nailed on to the rafters, each layer overlapping the one below it, so that the rain falling on the sloping roof shall run from the top to the bottom without coming through.

Bricks have lately been made with perforations through them, which is done by having a mould with a number of iron rods projecting from its bottom, so that when the clay is forced on them they pass right through it, and leave holes. The objects gained by this are two; in the first place, the bricks are much lighter, a great advantage in building, and in the second place they do not get so much out of form in burning, as there is no great substance between the holes, and therefore the shrinking takes place more evenly. Most of these bricks are of a light straw color, and are used for facing. They are mixed with a quantity of chalk, which is worked up with the clay, and are not baked at such a heat as would burn it into lime.

MIXING CHALK.

TOBACCO-PIPES.Tobacco-pipes are made of a fine white clay, found chiefly in the island of Purbeck, and called, from its use, pipe-clay. Dr. Ure gives the following account of the manufacture of tobacco-pipes:—“A child fashions a ball of clay from the heap, rolls it out into a slender cylinder upon a plank, with the palms of his hands, in order to form the stem of the pipe. He sticks a lump at the end of the cylinder, for forming the bowl; which, having done, he lays the piece aside for a day or two to get more consistence. In proportion as he makes these rough figures, he arranges them by dozens on a board, and hands them to the pipe-maker. The pipe is finished by means of a folding brass or iron mould, channelled inside of the shape of the stem and the bowl, and capable of being opened at the two ends. It is formed of two pieces, each hollowed out like a half pipe cut as it were lengthwise, and these two jaws when brought together constitute the exact space for making one pipe; there are small pins in one side of the mould, corresponding to holes in the other, which serve as guides for applying the two together with precision. The workman takes a long iron wire, with its end oiled, and pushes it through the soft clay in the direction of the stem, to form the bore, and he directs the wire by feeling with his left hand the progress of the point. He lays the pipe in the groove of one of the jaws of the mould, with the wire sticking in it, applies the other jaw, brings them smartly together, and unites them by a clamp or vice, which produces the external form; a lever is now brought down, which presses an oiled stopper into the bowl of the pipe while it is in the mould, forcing it sufficiently down to form the cavity, the wire in the meanwhile being thrust backwards and forwards, so as to pierce the tube completely through; the wire must become visible at the bottom of the bowl, otherwise the pipe will be imperfect. The wire is now withdrawn, the jaws of the mould opened, the pipe taken out, and the redundant clay removed with a knife; after drying for a day or two, the pipes are scraped, polished with a piece of hard wood, and, the stems being bent into the desired form, they are carried to the baking kiln, which is capable of firing fifty gross in from eight to twelve hours. A workman and a child can easily make five gross of pipes in a day.”FURNACE.The pipes known as “meerschaum” are cut and shaped out of a natural earth or mineral, found chiefly in the island of Samos; it is not a clay, but consists of silica, magnesia, and lime, and is therefore a kind of magnesian limestone. It is nearly white, very light and porous, is easily cut with a knife, and bears a beautiful polish when saturated with the oil of the tobacco, which at the same time gives to the pipes a rich dark-brown color.The meerschaum pipes sold in London are saturated with wax or grease, to cause them to color more easily, and many are not meerschaum at all, but are made of the dust produced in the cutting and boring of the real meerschaum pipes, mixed up with size; these fictitious pipes are heavier and less porous than the true meerschaum pipes, and neither color so readily nor bear so beautiful a polish; they are, moreover, much more easily broken.

Tobacco-pipes are made of a fine white clay, found chiefly in the island of Purbeck, and called, from its use, pipe-clay. Dr. Ure gives the following account of the manufacture of tobacco-pipes:—“A child fashions a ball of clay from the heap, rolls it out into a slender cylinder upon a plank, with the palms of his hands, in order to form the stem of the pipe. He sticks a lump at the end of the cylinder, for forming the bowl; which, having done, he lays the piece aside for a day or two to get more consistence. In proportion as he makes these rough figures, he arranges them by dozens on a board, and hands them to the pipe-maker. The pipe is finished by means of a folding brass or iron mould, channelled inside of the shape of the stem and the bowl, and capable of being opened at the two ends. It is formed of two pieces, each hollowed out like a half pipe cut as it were lengthwise, and these two jaws when brought together constitute the exact space for making one pipe; there are small pins in one side of the mould, corresponding to holes in the other, which serve as guides for applying the two together with precision. The workman takes a long iron wire, with its end oiled, and pushes it through the soft clay in the direction of the stem, to form the bore, and he directs the wire by feeling with his left hand the progress of the point. He lays the pipe in the groove of one of the jaws of the mould, with the wire sticking in it, applies the other jaw, brings them smartly together, and unites them by a clamp or vice, which produces the external form; a lever is now brought down, which presses an oiled stopper into the bowl of the pipe while it is in the mould, forcing it sufficiently down to form the cavity, the wire in the meanwhile being thrust backwards and forwards, so as to pierce the tube completely through; the wire must become visible at the bottom of the bowl, otherwise the pipe will be imperfect. The wire is now withdrawn, the jaws of the mould opened, the pipe taken out, and the redundant clay removed with a knife; after drying for a day or two, the pipes are scraped, polished with a piece of hard wood, and, the stems being bent into the desired form, they are carried to the baking kiln, which is capable of firing fifty gross in from eight to twelve hours. A workman and a child can easily make five gross of pipes in a day.”

FURNACE.

The pipes known as “meerschaum” are cut and shaped out of a natural earth or mineral, found chiefly in the island of Samos; it is not a clay, but consists of silica, magnesia, and lime, and is therefore a kind of magnesian limestone. It is nearly white, very light and porous, is easily cut with a knife, and bears a beautiful polish when saturated with the oil of the tobacco, which at the same time gives to the pipes a rich dark-brown color.

The meerschaum pipes sold in London are saturated with wax or grease, to cause them to color more easily, and many are not meerschaum at all, but are made of the dust produced in the cutting and boring of the real meerschaum pipes, mixed up with size; these fictitious pipes are heavier and less porous than the true meerschaum pipes, and neither color so readily nor bear so beautiful a polish; they are, moreover, much more easily broken.

Back to Index Next