BLEACHING.

BLEACHING.BLEACHING WORKS.SINGEING APPARATUS.DRYING APPARATUS.The chief object of bleaching is to get rid of the natural coloring matter which always tinges cotton, silk, &c., as produced from the raw material, and also to get rid of any greasy matters, or stains from accidental causes. Cotton is not only required to be bleached when intended to remain white, but also before dyeing or printing, the colors being thereby rendered more uniform and brilliant. The oldest method of bleaching consisted in simply exposing the goods, moistened with water, to the action of light and air, by spreading them out on the grass, and hence the term “grass-bleached;” but this is by far too tedious a process for the present day, when the manufacture is so great and the consumption so rapid.The process of bleaching cotton goods consists in boiling them first in water, then in a mixture of lime and water, and then in a solution of soda, soaking them in a solution of chloride of lime, afterwards in water acidulated with sulphuric acid, and finally in pure water. Linens are chiefly bleached by repeated boilings in solutions of potash or pearlash, and afterwards in chloride of lime; wool by soaking in warm water, exposing it to the vapour of sulphur, and finally washing in a solution of soft soap.Before being printed, it is necessary that all the loose fibres should be removed from the surface of the goods. This is effected by “singeing,” which is done by causing the goods to pass over a red-hot roller, setting fire to the fine fibres projecting from the surface only, but with a motion too rapid to allow the fabric to be scorched. This process, and also the apparatus by which the articles are dried after bleaching, are shown in the accompanying illustrations. The latter consists of a series of hollow rollers heated by steam, over which the goods to be dried are passed, a current of air being admitted to carry off the vapour.

BLEACHING WORKS.

SINGEING APPARATUS.

DRYING APPARATUS.

The chief object of bleaching is to get rid of the natural coloring matter which always tinges cotton, silk, &c., as produced from the raw material, and also to get rid of any greasy matters, or stains from accidental causes. Cotton is not only required to be bleached when intended to remain white, but also before dyeing or printing, the colors being thereby rendered more uniform and brilliant. The oldest method of bleaching consisted in simply exposing the goods, moistened with water, to the action of light and air, by spreading them out on the grass, and hence the term “grass-bleached;” but this is by far too tedious a process for the present day, when the manufacture is so great and the consumption so rapid.

The process of bleaching cotton goods consists in boiling them first in water, then in a mixture of lime and water, and then in a solution of soda, soaking them in a solution of chloride of lime, afterwards in water acidulated with sulphuric acid, and finally in pure water. Linens are chiefly bleached by repeated boilings in solutions of potash or pearlash, and afterwards in chloride of lime; wool by soaking in warm water, exposing it to the vapour of sulphur, and finally washing in a solution of soft soap.

Before being printed, it is necessary that all the loose fibres should be removed from the surface of the goods. This is effected by “singeing,” which is done by causing the goods to pass over a red-hot roller, setting fire to the fine fibres projecting from the surface only, but with a motion too rapid to allow the fabric to be scorched. This process, and also the apparatus by which the articles are dried after bleaching, are shown in the accompanying illustrations. The latter consists of a series of hollow rollers heated by steam, over which the goods to be dried are passed, a current of air being admitted to carry off the vapour.

CALICO-PRINTING.CALICO-PRINTING WORKS.(‡ Printing Schematic.)FIG.1.AGEING PROCESS.Calico-printing is executed either by hand (with wooden blocks having the pattern engraved—projecting—on their surfaces) or by means of machinery. Printing by hand-blocks is a tedious operation, and is now almost superseded by the cylinder. The hand process is very similar to that made use of in paper-staining (whichsee). Cylinder-printing is a much more rapid process, conducted by means of a brass cylinder with the pattern engraved on its surface, which is made to revolve against another cylinder covered with flannel, and charged with color from a trough into which its lower part is dipped. The calico is passed over a large cylinder made to revolve in contact with that on which the pattern is engraved, and which is charged with color from the one below it.Fig. 1shows this arrangement,abeing the large cylinder with the calico round it,bthe engraved cylinder,cthe color cylinder, anddthe color trough. As the engraved cylinder revolves, it prints the pattern at each revolution, and this is repeated again and again, to the whole length of the piece of calico. In some machines there are several engraved cylinders, each printing its own color, and so arranged that the colors shall fit into the parts of the design requiring them, the whole making up the complete pattern.DRYING ROOM.Before being printed, the calico is prepared by being passed through a preparation, called a mordant, capable of fixing the colors, and preventing them being washed out, and several of these are used, according to the colors required. The colors are thickened with paste, so as to prevent them from running into each other when printed. Muslins, chintzes, &c., are printed in a similar manner to calicoes.When the pieces of calico come from the printing cylinders, they are made to pass upwards through holes in the ceiling to a room above, where they pass over surfaces of iron heated by steam, so as to thoroughly dry them; they then descend through the floor into the printing room, where they are packed. The process called “ageing” consists in exposing the calicoes to the air for a certain time, to take off the harshness and stiffness peculiar to new goods.In some cases the colors themselves are not printed on the goods, the mordants being used instead, and the whole piece is then boiled in a vat of dye-stuff, which, however, only adheres to the parts printed with the mordant, all the rest being easily got rid of by simple washing.

CALICO-PRINTING WORKS.

(‡ Printing Schematic.)FIG.1.

FIG.1.

AGEING PROCESS.

Calico-printing is executed either by hand (with wooden blocks having the pattern engraved—projecting—on their surfaces) or by means of machinery. Printing by hand-blocks is a tedious operation, and is now almost superseded by the cylinder. The hand process is very similar to that made use of in paper-staining (whichsee). Cylinder-printing is a much more rapid process, conducted by means of a brass cylinder with the pattern engraved on its surface, which is made to revolve against another cylinder covered with flannel, and charged with color from a trough into which its lower part is dipped. The calico is passed over a large cylinder made to revolve in contact with that on which the pattern is engraved, and which is charged with color from the one below it.Fig. 1shows this arrangement,abeing the large cylinder with the calico round it,bthe engraved cylinder,cthe color cylinder, anddthe color trough. As the engraved cylinder revolves, it prints the pattern at each revolution, and this is repeated again and again, to the whole length of the piece of calico. In some machines there are several engraved cylinders, each printing its own color, and so arranged that the colors shall fit into the parts of the design requiring them, the whole making up the complete pattern.

DRYING ROOM.

Before being printed, the calico is prepared by being passed through a preparation, called a mordant, capable of fixing the colors, and preventing them being washed out, and several of these are used, according to the colors required. The colors are thickened with paste, so as to prevent them from running into each other when printed. Muslins, chintzes, &c., are printed in a similar manner to calicoes.

When the pieces of calico come from the printing cylinders, they are made to pass upwards through holes in the ceiling to a room above, where they pass over surfaces of iron heated by steam, so as to thoroughly dry them; they then descend through the floor into the printing room, where they are packed. The process called “ageing” consists in exposing the calicoes to the air for a certain time, to take off the harshness and stiffness peculiar to new goods.

In some cases the colors themselves are not printed on the goods, the mordants being used instead, and the whole piece is then boiled in a vat of dye-stuff, which, however, only adheres to the parts printed with the mordant, all the rest being easily got rid of by simple washing.

DYEING.(‡ Dyeing Process.)The art of dyeing does not simply consist in coloring the different substances; if this were the case, the color would be washed out as easily as imparted. Nearly all the colors used in dyeing being of vegetable origin, it is necessary to apply some substances to the fabrics to be dyed which shall fix the colors in the grain. Of these (called “mordants”) the chief are acetate of alumina, acetate of iron, and chloride of tin (substances well known to chemists), which have the property of making the coloring matter insoluble, so that it cannot be washed out.There are various ways of dyeing. If the fabric has to be dyed all one color, it is dipped in the mordant, dried, and afterwards boiled in a solution of the dye-stuff. If a colored ground with white figures is required, then the figures are printed on it with what is called a “resist,” that is, some substance thickened with gum, paste, or pipe-clay, which will resist the action of the mordant and dye-stuff, so that when the fabric is afterwards rinsed these figures remain white. If the ground is to be white and the pattern dyed on it, then this is printed with the mordant and the color adheres only to the parts printed, although the whole be boiled with the dye-stuff, what little may adhere to the ground being easily washed out in the rinsing. Sometimes the kind of mordant used determines the color of the dye; for instance, madder will dye red with the chloride of tin, and black with the acetate of iron. If we now suppose a piece of cloth to be printed in lines of acetate of iron, and figures of chloride of tin, when the whole is boiled in the madder vat, the cloth comes out with black lines and red figures on a white ground.Another point to be considered is the kind of stuff to be dyed, whether cotton, silk, or woollen, or a mixture of either, for what will take one kind of dye will not always take another, and advantage is taken of this to dye two colors at once, or part white and part colored. A table-cover, for instance, woven with worsted and cotton, can be boiled in various kinds of dye, and produce white and blue, or white and red, for that dye is selected which will attach itself only to one kind of fabric, and leave the other.SCOURING.Many other chemical qualities of the substances used as dyes, and of the substances to be dyed, are also taken into consideration. One of the chief of these is shown in dyeing with indigo. This substance (a vegetable extract) as brought to England is quite insoluble in water and unfit for use as a dye; but it is made soluble, and at the same time almost colorless, by mixing with lime, sulphate of iron, and water. These substances deprive it of its oxygen, and the straw-colored solution is then used for dyeing, the substances boiled in it attaining—as the indigo regains its oxygen on exposure to the air—a deep blue color.With dyeing is often associated the art of “scouring,” for a knowledge of the properties of the dye-stuffs used enables the workman to discriminate between what will brighten and what would injure the goods to be cleaned.

(‡ Dyeing Process.)

The art of dyeing does not simply consist in coloring the different substances; if this were the case, the color would be washed out as easily as imparted. Nearly all the colors used in dyeing being of vegetable origin, it is necessary to apply some substances to the fabrics to be dyed which shall fix the colors in the grain. Of these (called “mordants”) the chief are acetate of alumina, acetate of iron, and chloride of tin (substances well known to chemists), which have the property of making the coloring matter insoluble, so that it cannot be washed out.

There are various ways of dyeing. If the fabric has to be dyed all one color, it is dipped in the mordant, dried, and afterwards boiled in a solution of the dye-stuff. If a colored ground with white figures is required, then the figures are printed on it with what is called a “resist,” that is, some substance thickened with gum, paste, or pipe-clay, which will resist the action of the mordant and dye-stuff, so that when the fabric is afterwards rinsed these figures remain white. If the ground is to be white and the pattern dyed on it, then this is printed with the mordant and the color adheres only to the parts printed, although the whole be boiled with the dye-stuff, what little may adhere to the ground being easily washed out in the rinsing. Sometimes the kind of mordant used determines the color of the dye; for instance, madder will dye red with the chloride of tin, and black with the acetate of iron. If we now suppose a piece of cloth to be printed in lines of acetate of iron, and figures of chloride of tin, when the whole is boiled in the madder vat, the cloth comes out with black lines and red figures on a white ground.

Another point to be considered is the kind of stuff to be dyed, whether cotton, silk, or woollen, or a mixture of either, for what will take one kind of dye will not always take another, and advantage is taken of this to dye two colors at once, or part white and part colored. A table-cover, for instance, woven with worsted and cotton, can be boiled in various kinds of dye, and produce white and blue, or white and red, for that dye is selected which will attach itself only to one kind of fabric, and leave the other.

SCOURING.

Many other chemical qualities of the substances used as dyes, and of the substances to be dyed, are also taken into consideration. One of the chief of these is shown in dyeing with indigo. This substance (a vegetable extract) as brought to England is quite insoluble in water and unfit for use as a dye; but it is made soluble, and at the same time almost colorless, by mixing with lime, sulphate of iron, and water. These substances deprive it of its oxygen, and the straw-colored solution is then used for dyeing, the substances boiled in it attaining—as the indigo regains its oxygen on exposure to the air—a deep blue color.

With dyeing is often associated the art of “scouring,” for a knowledge of the properties of the dye-stuffs used enables the workman to discriminate between what will brighten and what would injure the goods to be cleaned.

CALENDERING.The process of calendering is resorted to for producing a fine smooth surface on calicoes and other goods, and for rendering them sufficiently even to be printed upon (see “Calico-printing”). The calendering machine consists of a set of five rollers, constructed to revolve at unequal rates, so that the one which turns upon the face of the calico not only rolls it between itself and its fellow, but—turning faster—rubsit and gives a gloss to the surface similar to the effect which would be produced if the goods were laid on a table, and the roller rubbed over them instead of being rolled. These rollers are very curiously constructed. They are made by packing many hundreds of round pieces of pasteboard—having each a square hole in the centre, and several smaller circular ones in the margin—on to a central bar of iron, with similar bars through the smaller holes, until a sufficient number have been added to produce the length of roller required. Nuts are then fitted to the ends of the smaller iron bars, and these being screwed tightly, compress the whole into so solid a mass, that it can be turned in a lathe to a perfectly smooth surface, which is (unlike wood) not liable to crack, and, being slightly elastic, does not crush the goods, as metal rollers would.

The process of calendering is resorted to for producing a fine smooth surface on calicoes and other goods, and for rendering them sufficiently even to be printed upon (see “Calico-printing”). The calendering machine consists of a set of five rollers, constructed to revolve at unequal rates, so that the one which turns upon the face of the calico not only rolls it between itself and its fellow, but—turning faster—rubsit and gives a gloss to the surface similar to the effect which would be produced if the goods were laid on a table, and the roller rubbed over them instead of being rolled. These rollers are very curiously constructed. They are made by packing many hundreds of round pieces of pasteboard—having each a square hole in the centre, and several smaller circular ones in the margin—on to a central bar of iron, with similar bars through the smaller holes, until a sufficient number have been added to produce the length of roller required. Nuts are then fitted to the ends of the smaller iron bars, and these being screwed tightly, compress the whole into so solid a mass, that it can be turned in a lathe to a perfectly smooth surface, which is (unlike wood) not liable to crack, and, being slightly elastic, does not crush the goods, as metal rollers would.

BREAD MAKING.This process is much the same whatever kind of meal or flour may be used, whether wheaten, barley, &c. A certain portion of the flour is mixed with warm water (in which a little salt is generally dissolved), some yeast or “barm” (the froth from the fermentation of beer) is added, and the whole worked together to a pasty consistence, this is put into a pan to keep warm, and is called “the sponge;” besides flour and water nearly every baker mixes his sponge with a certain proportion of potatoes boiled to a “squash,” and passed through a sieve to separate the rinds. In an hour or so it swells up to double its original size, from the fermentation which is going on producing a kind of gas called “carbonic acid,” which being formed in every part of the “sponge,” inflates it to a great extent. After a time it sinks down (most of the gas escaping), and begins to rise again; it is then mixed with the remainder of the flour (and some water if necessary), and the whole thoroughly kneaded together with the hands till it is all of an equal consistence—this should be neither too stiff, nor so soft as to stick to the hands. It is now to be cut up and weighed out into pieces to form each loaf. The oven in which the bread is baked is made of “fire-brick,” and so embedded in earth or brickwork that when heated it shall not readily cool; this is heated with coal or wood till it is nearly red-hot and the loaves are put in and left till baked.

This process is much the same whatever kind of meal or flour may be used, whether wheaten, barley, &c. A certain portion of the flour is mixed with warm water (in which a little salt is generally dissolved), some yeast or “barm” (the froth from the fermentation of beer) is added, and the whole worked together to a pasty consistence, this is put into a pan to keep warm, and is called “the sponge;” besides flour and water nearly every baker mixes his sponge with a certain proportion of potatoes boiled to a “squash,” and passed through a sieve to separate the rinds. In an hour or so it swells up to double its original size, from the fermentation which is going on producing a kind of gas called “carbonic acid,” which being formed in every part of the “sponge,” inflates it to a great extent. After a time it sinks down (most of the gas escaping), and begins to rise again; it is then mixed with the remainder of the flour (and some water if necessary), and the whole thoroughly kneaded together with the hands till it is all of an equal consistence—this should be neither too stiff, nor so soft as to stick to the hands. It is now to be cut up and weighed out into pieces to form each loaf. The oven in which the bread is baked is made of “fire-brick,” and so embedded in earth or brickwork that when heated it shall not readily cool; this is heated with coal or wood till it is nearly red-hot and the loaves are put in and left till baked.

SUGAR REFINING.When brown or raw sugar is refined it forms the white crystalline product known as loaf sugar. The process involves many ingenious arrangements in its detail, but the essential object to be obtained is the separation of all coloring matter from the raw material without producing any more by the process, which is a greater difficulty than would at first appear, for all solutions of sugar evaporated in the open air become to a great extent colored, and the longer the exposure, and the higher the temperature, the worse the product; a substance forming called “caramel,” which discolors it.(‡ Conical Pot.)FIG.1.(‡ Filling Conical Pots.)FIG.2.The brown sugar is first mixed with a very small quantity of boiling water, just sufficient to form a thick pasty mass, which is put into conical pots (figs. 1 and 2), and allowed to drain, the small quantity of water washes out only the brown part, and leaves the crystals pretty white; they are then dissolved in water, mixed with some bone-black and bullock’s blood; the bone-black is the charcoal from burnt bones, and has the power of taking away the color of most vegetable solutions, the bullock’s blood is used as affording a cheap kind of albumen, which when the solution of sugar is boiled coagulates and entangles all the floating matters so that they may be removed by filtration.VACUUM-PAN.(‡ Sugar Lathe.)FIG.3.The liquid is boiled for a time, and then put into a cistern excluded from the light, having holes at the bottom into which long tubes of thick twilled cotton are fastened, through which the solution runs as bright as water; they all hang down into another cistern below, also kept from the light, from which it is pumped up into the evaporating apparatus—a copper vessel entirely air-tight, heated by steam and having a powerful air-pump attached to it by which all the vapour and air are removed as the syrup becomes hot; this is called a “vacuum pan” (seeengraving), and by this the syrup is condensed to the proper consistence, and is put into moulds of the shape the loaf is to be, having holes at the lower part which are plugged up, the syrup as it cools forming a solid mass of crystals; these moulds are arranged in rows over a channel leading to a proper receptacle, the plugs are taken out from the holes at the bottom of each and some pure concentrated syrup is poured on to the upper part; this slowly descending filters through the sugar, carrying with it any “caramel” that may have formed, finally escapes at the hole, and runs into the cistern; this completely whitens the sugar, and gives it a brighter and coarser grain. The loaves are then taken from the moulds, dried in an oven at a gentle heat, and finally packed in paper for sale. If the pointed ends are discolored or ragged the loaf is put into a lathe (fig. 3)and the end turned to a proper figure or cut off.

When brown or raw sugar is refined it forms the white crystalline product known as loaf sugar. The process involves many ingenious arrangements in its detail, but the essential object to be obtained is the separation of all coloring matter from the raw material without producing any more by the process, which is a greater difficulty than would at first appear, for all solutions of sugar evaporated in the open air become to a great extent colored, and the longer the exposure, and the higher the temperature, the worse the product; a substance forming called “caramel,” which discolors it.

(‡ Conical Pot.)FIG.1.

FIG.1.

(‡ Filling Conical Pots.)FIG.2.

FIG.2.

The brown sugar is first mixed with a very small quantity of boiling water, just sufficient to form a thick pasty mass, which is put into conical pots (figs. 1 and 2), and allowed to drain, the small quantity of water washes out only the brown part, and leaves the crystals pretty white; they are then dissolved in water, mixed with some bone-black and bullock’s blood; the bone-black is the charcoal from burnt bones, and has the power of taking away the color of most vegetable solutions, the bullock’s blood is used as affording a cheap kind of albumen, which when the solution of sugar is boiled coagulates and entangles all the floating matters so that they may be removed by filtration.

VACUUM-PAN.

(‡ Sugar Lathe.)FIG.3.

FIG.3.

The liquid is boiled for a time, and then put into a cistern excluded from the light, having holes at the bottom into which long tubes of thick twilled cotton are fastened, through which the solution runs as bright as water; they all hang down into another cistern below, also kept from the light, from which it is pumped up into the evaporating apparatus—a copper vessel entirely air-tight, heated by steam and having a powerful air-pump attached to it by which all the vapour and air are removed as the syrup becomes hot; this is called a “vacuum pan” (seeengraving), and by this the syrup is condensed to the proper consistence, and is put into moulds of the shape the loaf is to be, having holes at the lower part which are plugged up, the syrup as it cools forming a solid mass of crystals; these moulds are arranged in rows over a channel leading to a proper receptacle, the plugs are taken out from the holes at the bottom of each and some pure concentrated syrup is poured on to the upper part; this slowly descending filters through the sugar, carrying with it any “caramel” that may have formed, finally escapes at the hole, and runs into the cistern; this completely whitens the sugar, and gives it a brighter and coarser grain. The loaves are then taken from the moulds, dried in an oven at a gentle heat, and finally packed in paper for sale. If the pointed ends are discolored or ragged the loaf is put into a lathe (fig. 3)and the end turned to a proper figure or cut off.

BREWING.THE VATS.Beer is made by pouring boiling water upon ground malt, and after a time drawing it off, which is repeated until all its soluble parts are removed and dissolved in the water; the liquor resulting is called “sweet wort,” which is then boiled with a certain proportion of hops (the dried “stobules” or flowers of the hop plant), and the liquor allowed to cool.FERMENTING ROOM.ENGINE ROOM.It is then mixed with a small quantity of “yest,” which is the scum thrown off by a former brewing, and the whole is allowed to ferment till nearly all the sweet sugary matter which was got from the malt is converted into spirit, it is then put into casks and allowed to ferment slowly, in which process it throws off more yest, which is collected, as seen in the cut, for the next brewing. It is then bunged up in the barrels and kept for a time, when it is fit for use.MASH TUN.BOILER.In large breweries machinery of various kinds is employed, such as pumps for pumping up water, taps for drawing it off machinery for stirring up the mash in the “mash tun,” and also the hops in the boiler, to prevent them burning at the bottom of it. The “cooling floor” is a contrivance for cooling the wort, consisting of a series of pipes which pass in a serpentine manner through it, and through which cold water is made to flow. The kind of beer, whether ale or porter, chiefly depends upon the kind of malt used; for ale, very pale malt, called “amber,” while for porter, burnt malt is employed, and hence the color of these two descriptions of beer. If the fermentation is not carried far enough the beer will be too sweet, and if too far it will be sour.COOLING FLOOR.

THE VATS.

Beer is made by pouring boiling water upon ground malt, and after a time drawing it off, which is repeated until all its soluble parts are removed and dissolved in the water; the liquor resulting is called “sweet wort,” which is then boiled with a certain proportion of hops (the dried “stobules” or flowers of the hop plant), and the liquor allowed to cool.

FERMENTING ROOM.

ENGINE ROOM.

It is then mixed with a small quantity of “yest,” which is the scum thrown off by a former brewing, and the whole is allowed to ferment till nearly all the sweet sugary matter which was got from the malt is converted into spirit, it is then put into casks and allowed to ferment slowly, in which process it throws off more yest, which is collected, as seen in the cut, for the next brewing. It is then bunged up in the barrels and kept for a time, when it is fit for use.

MASH TUN.

BOILER.

In large breweries machinery of various kinds is employed, such as pumps for pumping up water, taps for drawing it off machinery for stirring up the mash in the “mash tun,” and also the hops in the boiler, to prevent them burning at the bottom of it. The “cooling floor” is a contrivance for cooling the wort, consisting of a series of pipes which pass in a serpentine manner through it, and through which cold water is made to flow. The kind of beer, whether ale or porter, chiefly depends upon the kind of malt used; for ale, very pale malt, called “amber,” while for porter, burnt malt is employed, and hence the color of these two descriptions of beer. If the fermentation is not carried far enough the beer will be too sweet, and if too far it will be sour.

COOLING FLOOR.

DISTILLATION.(‡ Distillery.)The process of distilling consists in converting the fluid to be distilled into vapour, and condensing it into a fluid in another vessel. By this process the more volatile parts of any fluid are separated from the rest; for example, if brandy be distilled, the spirit or alcohol it contains will be converted into vapour and will condense in the receiver comparatively pure (see “Alcohol”), leaving behind in the still the water, coloring matter, &c., so that the spirit is colorless, although the brandy may have been quite brown. Also, if common water be distilled, pure water will pass over, and the earthy matters which the water had contained will be left behind (for all ordinary water contains considerable quantities of earthy matters, dissolved out from the earth over which it flows). The vessels used for distilling are very various in their forms, to suit the different fluids, both as to quantity and quality (see “Still”). There is a contrivance lately used for distilling spirit from the fermented wash containing it, by which it is allowed to flow into an apartment full of double floors, a few inches above each other, the upper ones being made of thin copper perforated all over with minute holes, and on which the wash is allowed to flow to the depth of about an inch. Into the space between the upper and lower parts of each floor steam is admitted, which, rising through the little holes, is condensed by the wash, giving out its heat to the spirit contained therein, and causing it to be converted into vapour, which passes off from the spaces between the floors to a condensing apparatus with which they all communicate.

(‡ Distillery.)

The process of distilling consists in converting the fluid to be distilled into vapour, and condensing it into a fluid in another vessel. By this process the more volatile parts of any fluid are separated from the rest; for example, if brandy be distilled, the spirit or alcohol it contains will be converted into vapour and will condense in the receiver comparatively pure (see “Alcohol”), leaving behind in the still the water, coloring matter, &c., so that the spirit is colorless, although the brandy may have been quite brown. Also, if common water be distilled, pure water will pass over, and the earthy matters which the water had contained will be left behind (for all ordinary water contains considerable quantities of earthy matters, dissolved out from the earth over which it flows). The vessels used for distilling are very various in their forms, to suit the different fluids, both as to quantity and quality (see “Still”). There is a contrivance lately used for distilling spirit from the fermented wash containing it, by which it is allowed to flow into an apartment full of double floors, a few inches above each other, the upper ones being made of thin copper perforated all over with minute holes, and on which the wash is allowed to flow to the depth of about an inch. Into the space between the upper and lower parts of each floor steam is admitted, which, rising through the little holes, is condensed by the wash, giving out its heat to the spirit contained therein, and causing it to be converted into vapour, which passes off from the spaces between the floors to a condensing apparatus with which they all communicate.

GILDING.Gilding consists in covering the surfaces of various articles with a thin layer of gold, and may be divided into two kinds, quite different processes and practised by different artisans. The first is “oil-gilding,” which is a mechanical application of gold-leaf to some adhesive surface, the second is “water-gilding,” and is a chemical process.In oil-gilding, where frames, &c., are to be covered with gold-leaf, the first thing necessary is to obtain a smooth even surface on which it will lie, but as carved frames are expensive, ornaments of a kind of putty are fixed to the frame, and coated with whiting and size. The gold-leaf is made to adhere easily to this clammy surface, by simply damping it, and pressing the gold on by means of a piece of cotton wool, afterwards gently brushing it into all the markings. Wood and other articles to be gilt are coated with “gold-size,”—a sort of varnish—and when this is nearly dried, so as to be what is called “tackey,” it will hold the gold in the same way. When lettering is to be done in gold, the painted or varnished surface is first brushed over with whiting, which prevents the gold adhering where it is not wanted, the writing is then executed in gold-size, and the gold-leaf applied by pressing the book on to the surface, and finishing off with cotton wool, which rubs off all the superfluous gold-leaf and smooths it on the surface.Water-gilding (a process, however, in which no water is used) consists in covering the surface of metal with a thin coating of gold; the best metal for water-gilding is either brass, or a mixture of brass and copper. A mixture of gold and mercury, in the proportion of one part of gold to eight of mercury, is made hot over a fire till they have united; it is then put into a bag of chamois-leather, and the superfluous mercury pressed out. What remains is called an “amalgam;” it is soft, and of a greasy nature, so that it can be smeared over any surface with the fingers. The articles to be gilt are made perfectly clean on the surface, and a liquid made by dissolving mercury in nitric acid (aqua-fortis) is brushed over them by means of a brush made of fine brass wire, called a “scratch-brush.” The mercury immediately adheres to the surface of the metal, making it look like silver, when this is done, a little of the amalgam is rubbed on, and the article evenly covered with it. It is now heated in a charcoal fire till all the mercury evaporates, and the brass is left with a coating of gold, which is very dull but may be burnished with a steel burnisher and made bright if necessary. In former times articles were inlaid with thin plates of gold, which were placed in hollows made with a graver and melted in, a little borax being applied between.When a solution of “chloride of gold” is mixed with ether, the ether takes the gold away from the solution, and may be poured off the top charged with it. This solution, if applied to polished steel by means of a camel-hair pencil, rapidly evaporates, leaving a film of gold adhering to the steel, which, when burnished with any hard substance, has a very elegant appearance. In this way any ornamental design in gold may be produced, but it is not very durable.The gilt ornaments, scrolls, and mottoes on sword-blades, &c., are sometimes done in this way.“Gilding refined gold” would appear a great absurdity, but something very like it is often practised in the process called “coloring,” used by jewellers. This is however never applied to “refined gold” but to gold that is not quite so good in color as it should be. It is boiled in a liquid containing chemical substances capable of dissolving the alloy from the surface of the article and depositing a thin coating of pure gold, giving it the appearance of being made of better gold than it really is. This is in truth a species of electro-plating, but was in use very many years before the electro-depositing process had been discovered.

Gilding consists in covering the surfaces of various articles with a thin layer of gold, and may be divided into two kinds, quite different processes and practised by different artisans. The first is “oil-gilding,” which is a mechanical application of gold-leaf to some adhesive surface, the second is “water-gilding,” and is a chemical process.

In oil-gilding, where frames, &c., are to be covered with gold-leaf, the first thing necessary is to obtain a smooth even surface on which it will lie, but as carved frames are expensive, ornaments of a kind of putty are fixed to the frame, and coated with whiting and size. The gold-leaf is made to adhere easily to this clammy surface, by simply damping it, and pressing the gold on by means of a piece of cotton wool, afterwards gently brushing it into all the markings. Wood and other articles to be gilt are coated with “gold-size,”—a sort of varnish—and when this is nearly dried, so as to be what is called “tackey,” it will hold the gold in the same way. When lettering is to be done in gold, the painted or varnished surface is first brushed over with whiting, which prevents the gold adhering where it is not wanted, the writing is then executed in gold-size, and the gold-leaf applied by pressing the book on to the surface, and finishing off with cotton wool, which rubs off all the superfluous gold-leaf and smooths it on the surface.

Water-gilding (a process, however, in which no water is used) consists in covering the surface of metal with a thin coating of gold; the best metal for water-gilding is either brass, or a mixture of brass and copper. A mixture of gold and mercury, in the proportion of one part of gold to eight of mercury, is made hot over a fire till they have united; it is then put into a bag of chamois-leather, and the superfluous mercury pressed out. What remains is called an “amalgam;” it is soft, and of a greasy nature, so that it can be smeared over any surface with the fingers. The articles to be gilt are made perfectly clean on the surface, and a liquid made by dissolving mercury in nitric acid (aqua-fortis) is brushed over them by means of a brush made of fine brass wire, called a “scratch-brush.” The mercury immediately adheres to the surface of the metal, making it look like silver, when this is done, a little of the amalgam is rubbed on, and the article evenly covered with it. It is now heated in a charcoal fire till all the mercury evaporates, and the brass is left with a coating of gold, which is very dull but may be burnished with a steel burnisher and made bright if necessary. In former times articles were inlaid with thin plates of gold, which were placed in hollows made with a graver and melted in, a little borax being applied between.

When a solution of “chloride of gold” is mixed with ether, the ether takes the gold away from the solution, and may be poured off the top charged with it. This solution, if applied to polished steel by means of a camel-hair pencil, rapidly evaporates, leaving a film of gold adhering to the steel, which, when burnished with any hard substance, has a very elegant appearance. In this way any ornamental design in gold may be produced, but it is not very durable.The gilt ornaments, scrolls, and mottoes on sword-blades, &c., are sometimes done in this way.

“Gilding refined gold” would appear a great absurdity, but something very like it is often practised in the process called “coloring,” used by jewellers. This is however never applied to “refined gold” but to gold that is not quite so good in color as it should be. It is boiled in a liquid containing chemical substances capable of dissolving the alloy from the surface of the article and depositing a thin coating of pure gold, giving it the appearance of being made of better gold than it really is. This is in truth a species of electro-plating, but was in use very many years before the electro-depositing process had been discovered.

SILVERING LOOKING-GLASSES.Although this process is called “silvering,” yet no silver is used; the substance at the back of the glass is a mixture of tin and mercury, called an “amalgam,”—indeed, the term “amalgam” applies to all mixtures of mercury with other metals. The process is as follows:—A sheet of “tin-foil” (tin rolled out to about the thickness of paper) the size of the glass to be silvered is placed on a perfectly level table, covered with cloth; upon the tin-foil some mercury is poured, and spread evenly and quickly over the surface with a hare’s foot. The plate of glass is in the meanwhile to be made perfectly clean and dry—not the slightest speck or smear must remain. A sheet of tissue paper, also clean and dry, is laid over the surface of the mercury, the plate of glass is placed on the paper and made to correspond with the mercurialised tin-foil beneath. Weights are now placed on the plate of glass to keep it firmly down, and the sheet of paper is drawn out steadily and slowly; as it passes over the surface of the mercury it brings away all film or dust, and the surface being left perfectly bright, adheres so firmly to the dry glass that it is not easily removed. A great difficulty is to prevent air-bubbles from finding their way between the glass and mercury. The table is now raised slightly at one end, and the superfluous mercury allowed to drain off. After a few hours the tin-foil will be found to be completely united all through with the mercury, and will be so brittle that it can be scraped off in powder from the glass. Great care and practice are required to silver large plates, but any one by a few trials may succeed perfectly with a piece of glass a few inches square. Glass globes are silvered inside by shaking in them a mixture of mercury and tin filings until it adheres to the surface of the glass, which must first be made perfectly dry and warm.

Although this process is called “silvering,” yet no silver is used; the substance at the back of the glass is a mixture of tin and mercury, called an “amalgam,”—indeed, the term “amalgam” applies to all mixtures of mercury with other metals. The process is as follows:—A sheet of “tin-foil” (tin rolled out to about the thickness of paper) the size of the glass to be silvered is placed on a perfectly level table, covered with cloth; upon the tin-foil some mercury is poured, and spread evenly and quickly over the surface with a hare’s foot. The plate of glass is in the meanwhile to be made perfectly clean and dry—not the slightest speck or smear must remain. A sheet of tissue paper, also clean and dry, is laid over the surface of the mercury, the plate of glass is placed on the paper and made to correspond with the mercurialised tin-foil beneath. Weights are now placed on the plate of glass to keep it firmly down, and the sheet of paper is drawn out steadily and slowly; as it passes over the surface of the mercury it brings away all film or dust, and the surface being left perfectly bright, adheres so firmly to the dry glass that it is not easily removed. A great difficulty is to prevent air-bubbles from finding their way between the glass and mercury. The table is now raised slightly at one end, and the superfluous mercury allowed to drain off. After a few hours the tin-foil will be found to be completely united all through with the mercury, and will be so brittle that it can be scraped off in powder from the glass. Great care and practice are required to silver large plates, but any one by a few trials may succeed perfectly with a piece of glass a few inches square. Glass globes are silvered inside by shaking in them a mixture of mercury and tin filings until it adheres to the surface of the glass, which must first be made perfectly dry and warm.

SILVER PLATING.Plated goods consist of metallic articles coated with a thin plate of silver; the metal is made of a mixture of brass and copper, which is cast into flat slabs or ingots about an inch-and-a-half thick, the surface on one or both sides is filed flat and smooth, and a plate of silver of about the thirtieth part of an inch thick, but a little smaller than the metal, is applied smoothly to it, the edges are covered all round with borax ground fine with water and the plates tied tightly together with wire. The whole is then put into a furnace and closely watched till the silver begins to melt, when it is at once taken out and allowed to cool; by this mode of treatment the silver adheres so firmly to the metal that they become as one piece. It is then passed between steel rollers and rolled out to the required substance, the silver and metal both becoming thinner in about the same proportion, so that on a plate of metal, of whatever thickness, the silver is somewhere about a fortieth or forty-fifth part of its thickness; these plates of metal coated with silver are worked by stamping, punching, or passing between rollers the edges of which have mouldings, curves, &c., cut on them, and the parts of each article when moulded are afterwards soldered together so as to form what is intended. Wires of various forms are plated in the same way and afterwards drawn out by means of draw-plates (see “Wire-drawing”). Electro-plating has to a great extent superseded this process (see “Electro-plating”).

Plated goods consist of metallic articles coated with a thin plate of silver; the metal is made of a mixture of brass and copper, which is cast into flat slabs or ingots about an inch-and-a-half thick, the surface on one or both sides is filed flat and smooth, and a plate of silver of about the thirtieth part of an inch thick, but a little smaller than the metal, is applied smoothly to it, the edges are covered all round with borax ground fine with water and the plates tied tightly together with wire. The whole is then put into a furnace and closely watched till the silver begins to melt, when it is at once taken out and allowed to cool; by this mode of treatment the silver adheres so firmly to the metal that they become as one piece. It is then passed between steel rollers and rolled out to the required substance, the silver and metal both becoming thinner in about the same proportion, so that on a plate of metal, of whatever thickness, the silver is somewhere about a fortieth or forty-fifth part of its thickness; these plates of metal coated with silver are worked by stamping, punching, or passing between rollers the edges of which have mouldings, curves, &c., cut on them, and the parts of each article when moulded are afterwards soldered together so as to form what is intended. Wires of various forms are plated in the same way and afterwards drawn out by means of draw-plates (see “Wire-drawing”). Electro-plating has to a great extent superseded this process (see “Electro-plating”).

ELECTRO-PLATING AND DEPOSITION OF METALS.(‡ Electro-Plating Process.)This art has for its objects the coating of metallic articles with other metals of more value, beauty, or durability, such as gold, silver, or copper, by means of electricity, and the formation (by the same means) of other articles by the deposition of metals, from liquids containing them, upon moulds or engraved surfaces capable of modelling them. When the deposit forms a coating intended to be permanent, and which adheres to the article so as to be incapable of removal, it is called “electro-plating,” but when a fac-simile of any surface is required, or a cast of a mould which may be removed, forms the object to be produced, it is called “electrotyping” or “electro-depositing.”(‡ Electro-Plating Experiment.)FIG.1.GILDING RINGS.By way of experiment, procure two vessels,AandB,fig. 1, in one of them,A, put some dilute sulphuric acid and two plates, one of zinc,Z, the other of copper,c, these must not touch each other, but may be separated about half an inch by two or three pieces of wood or cork, and bound round with string; each of these plates must have a piece of wire fastened by soldering to their upper parts. In the vesselBput some solution of sulphate of copper and a small quantity of dilute sulphuric acid, and attach another copper plate to the wire which comes from the copper plate in the acid; this second copper plate is to be immersed in the solution of sulphate of copper, and to the wire from the zinc plate is to be fixed the object to be coated with copper.If a medallion or other object is plaster, it should be soaked in very hot wax and then brushed over with blacklead until the surface is perfectly blackened and bright; the wire should be bound all round the margin and soldered (as it were) with melted wax to the medallion, taking care that this wax also is well coated with blacklead. If the object be now immersed in the sulphate of copper solution and kept at a short distance from the plate (it must not touch it), a coating of copper will soon cover the surface and form a perfect cast, which when of sufficient thickness may be removed by filing the edge all round (if instead of the plaster cast a copper coin or other copper object be used, the blackleading is not required, but the surface must be first made clean and bright). With the same arrangement, but using instead of the sulphate of copper a solution made by dissolving cyanide of silver in a solution of cyanide of potassium, a coating of silver will be deposited, and the same of gold (if cyanide of gold be used), but these coatings will not adhere. If it be intended that the coatings shall adhere, to plate the article with silver or gold, it should be first thoroughly cleaned, then brushed over with a solution of nitrate of mercury, washed in clean water, and put into the gold or silver solution; the nitrate of mercury will cover the copper article with a thin coating of mercury, which will be taken up as the gold or silver is deposited, and this coating will adhere, the article being thus “electro plated.” As in using the solution of sulphate of copper, a copper plate was immersed in the solution and united by the wire to the copper plate in the vesselA, so in using the solution of cyanide of silver, a silver plate must be used, and in the gold solution a gold plate, these plates being dissolved as the metal is deposited, the liquid remaining pretty much the same and serving for future operations. The gold and silver thus deposited are dull, but may be burnished with a steel burnisher, all over or in parts as the design may require. In manufacturing, these processes are much modified, and powerful galvanic batteries or electro-magnets used; in the latter case the electro-magnetic machine is often driven by a steam-engine and the troughs of depositing liquids contain often many dozens of articles, which are all receiving a coating at once.

(‡ Electro-Plating Process.)

This art has for its objects the coating of metallic articles with other metals of more value, beauty, or durability, such as gold, silver, or copper, by means of electricity, and the formation (by the same means) of other articles by the deposition of metals, from liquids containing them, upon moulds or engraved surfaces capable of modelling them. When the deposit forms a coating intended to be permanent, and which adheres to the article so as to be incapable of removal, it is called “electro-plating,” but when a fac-simile of any surface is required, or a cast of a mould which may be removed, forms the object to be produced, it is called “electrotyping” or “electro-depositing.”

(‡ Electro-Plating Experiment.)FIG.1.

FIG.1.

GILDING RINGS.

By way of experiment, procure two vessels,AandB,fig. 1, in one of them,A, put some dilute sulphuric acid and two plates, one of zinc,Z, the other of copper,c, these must not touch each other, but may be separated about half an inch by two or three pieces of wood or cork, and bound round with string; each of these plates must have a piece of wire fastened by soldering to their upper parts. In the vesselBput some solution of sulphate of copper and a small quantity of dilute sulphuric acid, and attach another copper plate to the wire which comes from the copper plate in the acid; this second copper plate is to be immersed in the solution of sulphate of copper, and to the wire from the zinc plate is to be fixed the object to be coated with copper.If a medallion or other object is plaster, it should be soaked in very hot wax and then brushed over with blacklead until the surface is perfectly blackened and bright; the wire should be bound all round the margin and soldered (as it were) with melted wax to the medallion, taking care that this wax also is well coated with blacklead. If the object be now immersed in the sulphate of copper solution and kept at a short distance from the plate (it must not touch it), a coating of copper will soon cover the surface and form a perfect cast, which when of sufficient thickness may be removed by filing the edge all round (if instead of the plaster cast a copper coin or other copper object be used, the blackleading is not required, but the surface must be first made clean and bright). With the same arrangement, but using instead of the sulphate of copper a solution made by dissolving cyanide of silver in a solution of cyanide of potassium, a coating of silver will be deposited, and the same of gold (if cyanide of gold be used), but these coatings will not adhere. If it be intended that the coatings shall adhere, to plate the article with silver or gold, it should be first thoroughly cleaned, then brushed over with a solution of nitrate of mercury, washed in clean water, and put into the gold or silver solution; the nitrate of mercury will cover the copper article with a thin coating of mercury, which will be taken up as the gold or silver is deposited, and this coating will adhere, the article being thus “electro plated.” As in using the solution of sulphate of copper, a copper plate was immersed in the solution and united by the wire to the copper plate in the vesselA, so in using the solution of cyanide of silver, a silver plate must be used, and in the gold solution a gold plate, these plates being dissolved as the metal is deposited, the liquid remaining pretty much the same and serving for future operations. The gold and silver thus deposited are dull, but may be burnished with a steel burnisher, all over or in parts as the design may require. In manufacturing, these processes are much modified, and powerful galvanic batteries or electro-magnets used; in the latter case the electro-magnetic machine is often driven by a steam-engine and the troughs of depositing liquids contain often many dozens of articles, which are all receiving a coating at once.

SOLDERING AND BRAZING.The art of uniting metals by another metal or alloy, is called soldering (which includes “hard and soft soldering,” and “brazing”). If any metal be applied in a melted state to the surface of a piece of cold metal, under ordinary circumstances it will not adhere, but runs off in globules, this is owing to the surface being covered with “oxide” or rust, but if the surface be scraped or filed bright and some substance applied which will defend it from the air, and at the same time become fluid at the heat of the melted metal, then it will adhere. For this purpose borax is used in hard soldering and brazing, that is in soldering with metals which require a considerable amount of heat to melt them; and sal ammoniac, rosin, oil, &c., in cases of soldering with “soft solder,” or solder that will readily melt. This soft solder is made of a mixture of lead and tin, and if required to melt very easily (as in soldering pewter), then some “bismuth” is added. Bismuth itself does not melt more readily than lead, but it has the property of causing other metals to melt more readily.If the edges of two pieces of tin, for example, have to be soldered together, an iron with a wooden handle and a piece of copper joined to the other end is used. This is made red-hot, and the pieces of tin being placed smoothly together and their edges sprinkled with rosin or sal ammoniac, the hot iron (first touched on a piece of rosin to clean it) is then applied to the joint, a piece of soft solder being applied at the same time, and as this melts it is drawn in a melted state by means of the hot iron (to which it adheres) down the joint. An excellent substance for soldering: all sorts of small work, such as pieces of brass, copper, or tin, is chloride of zinc-this may easily be made by putting pieces of zinc into spirit of salt, (hydrochloric acid), and allowing them to remain as long as any effervescence continues; this solution may be kept in a bottle and applied to any edge to be soldered, by means of a small brush or feather. When iron and copper have to be “brazed,” the joints are made bright, and then coated with borax ground into a paste with water. A mixture of brass and zinc (called spelter) in small grains is sprinkled on the joint and it is then put into the hollow of a bright fire which is urged by bellows till the spelter melts. Silver is joined by hard or “silver” solder, which is a mixture of silver, zinc, and copper, and the fusion is generally effected by a blow-pipe, (see “Blow-pipe”); gold is soldered by a mixture of gold and copper. Leaden pipes are joined by having the ends to be united scraped bright and introduced a short way one within the other, some melted solder is then poured from a small iron ladle on the joint at the same time that it is rubbed round with a piece of folded cloth greased on the surface. Joints in cisterns, etc., are generally made by scraping the edges clean with a steel scraper, and applying some lamp-black and size by means of a brush to the parts beyond, leaving a bright space of an inch or so on each side of the joint, a ladle of melted solder is then gradually poured on the joint and rubbed down with a piece of greased cloth, the lamp-black and size preventing the solder adhering to any part but that left bright, and in this way a straight neat joint is produced.

The art of uniting metals by another metal or alloy, is called soldering (which includes “hard and soft soldering,” and “brazing”). If any metal be applied in a melted state to the surface of a piece of cold metal, under ordinary circumstances it will not adhere, but runs off in globules, this is owing to the surface being covered with “oxide” or rust, but if the surface be scraped or filed bright and some substance applied which will defend it from the air, and at the same time become fluid at the heat of the melted metal, then it will adhere. For this purpose borax is used in hard soldering and brazing, that is in soldering with metals which require a considerable amount of heat to melt them; and sal ammoniac, rosin, oil, &c., in cases of soldering with “soft solder,” or solder that will readily melt. This soft solder is made of a mixture of lead and tin, and if required to melt very easily (as in soldering pewter), then some “bismuth” is added. Bismuth itself does not melt more readily than lead, but it has the property of causing other metals to melt more readily.

If the edges of two pieces of tin, for example, have to be soldered together, an iron with a wooden handle and a piece of copper joined to the other end is used. This is made red-hot, and the pieces of tin being placed smoothly together and their edges sprinkled with rosin or sal ammoniac, the hot iron (first touched on a piece of rosin to clean it) is then applied to the joint, a piece of soft solder being applied at the same time, and as this melts it is drawn in a melted state by means of the hot iron (to which it adheres) down the joint. An excellent substance for soldering: all sorts of small work, such as pieces of brass, copper, or tin, is chloride of zinc-this may easily be made by putting pieces of zinc into spirit of salt, (hydrochloric acid), and allowing them to remain as long as any effervescence continues; this solution may be kept in a bottle and applied to any edge to be soldered, by means of a small brush or feather. When iron and copper have to be “brazed,” the joints are made bright, and then coated with borax ground into a paste with water. A mixture of brass and zinc (called spelter) in small grains is sprinkled on the joint and it is then put into the hollow of a bright fire which is urged by bellows till the spelter melts. Silver is joined by hard or “silver” solder, which is a mixture of silver, zinc, and copper, and the fusion is generally effected by a blow-pipe, (see “Blow-pipe”); gold is soldered by a mixture of gold and copper. Leaden pipes are joined by having the ends to be united scraped bright and introduced a short way one within the other, some melted solder is then poured from a small iron ladle on the joint at the same time that it is rubbed round with a piece of folded cloth greased on the surface. Joints in cisterns, etc., are generally made by scraping the edges clean with a steel scraper, and applying some lamp-black and size by means of a brush to the parts beyond, leaving a bright space of an inch or so on each side of the joint, a ladle of melted solder is then gradually poured on the joint and rubbed down with a piece of greased cloth, the lamp-black and size preventing the solder adhering to any part but that left bright, and in this way a straight neat joint is produced.

THE SMELTING OF METALS.All metals are got from the earth where they exist in the form of “ores” (in reality metals combined with other matters), and “smelting” is the process of getting rid of these other matters, the chief of which are sulphur and oxygen. The ores when dug from the mine are generally stamped into powder, then “roasted,” that is, made hot and kept so for some time to drive off water, sulphur, or arsenic, which would prevent the “fluxes” acting properly. The fluxes are substances which will mix with, melt, and separate the matters to be got rid of, the chief being charcoal, coke, and limestone. The ore is then mixed with the flux and the whole raised to a great heat; as the metal is separated it melts, runs to the bottom of the “smelting furnace” and is drawn off into moulds made of sand; it is thus cast into short thick bars called “pigs,” so we hear of pig-iron, pig-lead, &c. Iron is smelted from “ironstone,” which is mixed with coke and limestone. The heat required to smelt iron is so very great, that a steam-engine is now always employed to blow the furnace (before the invention of the steam-engine, water-mills were used for the same purpose). The smelting is conducted in what is called a blast furnace. When the metal has all been “reduced” or smelted, and run down to the bottom of the furnace, a hole is made, out of which it runs into the moulds; this is called “tapping the furnace.”Smelting is often confounded with melting, as the names are somewhat alike, but the processes are entirely different; in melting, the metal is simply liquified, in smelting the metal has to be produced from ores which often have no appearance of containing any, as in the case of iron-stone, which looks like brown clay. By way of experiment let the reader take a small portion of “litharge,” which is a reddish powder, mix it with a drop of oil into a thick paste and place it on the end of a flat piece of charcoal or wood, and direct the flame of a candle upon it by means of a blow-pipe; a slight hissing noise will be heard, and in a moment or two a small, bright globule of lead will make its appearance.

All metals are got from the earth where they exist in the form of “ores” (in reality metals combined with other matters), and “smelting” is the process of getting rid of these other matters, the chief of which are sulphur and oxygen. The ores when dug from the mine are generally stamped into powder, then “roasted,” that is, made hot and kept so for some time to drive off water, sulphur, or arsenic, which would prevent the “fluxes” acting properly. The fluxes are substances which will mix with, melt, and separate the matters to be got rid of, the chief being charcoal, coke, and limestone. The ore is then mixed with the flux and the whole raised to a great heat; as the metal is separated it melts, runs to the bottom of the “smelting furnace” and is drawn off into moulds made of sand; it is thus cast into short thick bars called “pigs,” so we hear of pig-iron, pig-lead, &c. Iron is smelted from “ironstone,” which is mixed with coke and limestone. The heat required to smelt iron is so very great, that a steam-engine is now always employed to blow the furnace (before the invention of the steam-engine, water-mills were used for the same purpose). The smelting is conducted in what is called a blast furnace. When the metal has all been “reduced” or smelted, and run down to the bottom of the furnace, a hole is made, out of which it runs into the moulds; this is called “tapping the furnace.”

Smelting is often confounded with melting, as the names are somewhat alike, but the processes are entirely different; in melting, the metal is simply liquified, in smelting the metal has to be produced from ores which often have no appearance of containing any, as in the case of iron-stone, which looks like brown clay. By way of experiment let the reader take a small portion of “litharge,” which is a reddish powder, mix it with a drop of oil into a thick paste and place it on the end of a flat piece of charcoal or wood, and direct the flame of a candle upon it by means of a blow-pipe; a slight hissing noise will be heard, and in a moment or two a small, bright globule of lead will make its appearance.

FOUNDING.GENERAL FOUNDRY, WOOLWICH ARSENAL.Founding is the art of casting metals into various forms by means of moulds. The products of smelting are of a coarse kind, and have to be remelted before the process of casting or founding begins. Before any article can be cast in metal, a pattern must be formed in wood, clay, or other suitable substance. The floor of the foundry is made up of sand and powdered charcoal to the depth of several feet, serving to imbed the moulds which are used, and in several places deep pits full of the same material are formed for large castings; an iron frame, corresponding to another like it, and capable of being united to it by pins and sockets, is used to contain the moulding sand and pattern.GUN FOUNDRY, WOOLWICH ARSENAL.Let it be supposed, for simplicity, that a cannon ball has to be cast, one of the frames is filled with moulding sand moist enough to bear a good impression, and a cannon ball pressed half-way in; the surface is now dusted over with red ochre (to keep the upper half from sticking to it), and the other frame applied and united with the lower one, this is now filled with the sand and beaten or trodden down firmly. On separating the two and removing the pattern, there is an impression of half a ball in each half of the mould, and when these are again put together there is a hollow corresponding to the pattern used. There are, however, two things more to be attended to, one is to have an opening for the melted metal to be poured in, the other an opening for the air to escape, and this is effected by attaching to the pattern two pieces of wood or iron which project upwards through the upper half of the mould, and when this is carefully lifted up two holes appear which on being united to the lower half lead into the round hollow. When the moulds are ready they are put into a room heated by means of stoves, and thoroughly dried. They are then buried in the floor of the foundry, leaving the holes for pouring the metal exposed, channels being formed in the sand, so that when the furnace is “tapped” the melted metal may flow down these and fill the moulds. Some forms are so complicated that the moulds have to be made in several pieces, and the ingenuity of the founder is taxed to the utmost to produce those required.

GENERAL FOUNDRY, WOOLWICH ARSENAL.

Founding is the art of casting metals into various forms by means of moulds. The products of smelting are of a coarse kind, and have to be remelted before the process of casting or founding begins. Before any article can be cast in metal, a pattern must be formed in wood, clay, or other suitable substance. The floor of the foundry is made up of sand and powdered charcoal to the depth of several feet, serving to imbed the moulds which are used, and in several places deep pits full of the same material are formed for large castings; an iron frame, corresponding to another like it, and capable of being united to it by pins and sockets, is used to contain the moulding sand and pattern.

GUN FOUNDRY, WOOLWICH ARSENAL.

Let it be supposed, for simplicity, that a cannon ball has to be cast, one of the frames is filled with moulding sand moist enough to bear a good impression, and a cannon ball pressed half-way in; the surface is now dusted over with red ochre (to keep the upper half from sticking to it), and the other frame applied and united with the lower one, this is now filled with the sand and beaten or trodden down firmly. On separating the two and removing the pattern, there is an impression of half a ball in each half of the mould, and when these are again put together there is a hollow corresponding to the pattern used. There are, however, two things more to be attended to, one is to have an opening for the melted metal to be poured in, the other an opening for the air to escape, and this is effected by attaching to the pattern two pieces of wood or iron which project upwards through the upper half of the mould, and when this is carefully lifted up two holes appear which on being united to the lower half lead into the round hollow. When the moulds are ready they are put into a room heated by means of stoves, and thoroughly dried. They are then buried in the floor of the foundry, leaving the holes for pouring the metal exposed, channels being formed in the sand, so that when the furnace is “tapped” the melted metal may flow down these and fill the moulds. Some forms are so complicated that the moulds have to be made in several pieces, and the ingenuity of the founder is taxed to the utmost to produce those required.

GLASS BLOWING AND CASTING.CASTING PLATE GLASS.(‡ Collecting Glass With A Puntil.)FIG.1.(‡ Beginning Glass Form.)FIG.3.(‡ Glass Globe With Hole At End.)FIG.4.(‡ Blowing On The Puntil.)FIG.2.Glass-blowing requires great practice and manual dexterity, for the material used being red-hot cannot be touched with the hands, and has to be very rapidly worked, or it becomes cooled and hard; to any one unused to work with it, it is the most unmanageable material conceivable, but by practice the glass-blower contrives to produce almost any form required, and of a size quite astonishing—as, for instance, the globular bottles seen in druggists’ windows, which often hold twelve gallons, also glass shades, which are of an uniform thickness, and two or three feet high. This is all done by means of a hollow rod of iron called a “puntil,” on the one end of which a mass of molten glass is collected (fig. 1), and the workman blows into the other, at the same time turning the tube rapidly round in his hands (fig. 2). When the kind of glass called “crown-glass” has to be made, the end of the iron tube is put into the pot of melted glass, and turned round till a ball of it is collected about the size of one’s head, the workman then blows in at the other end, still turning the rod in his hands; it has now the appearance presented atfig. 3. An iron rod is stuck on to the side of the globe opposite to the “puntil,” which is then pulled suddenly away, leaving a round hole. The globe of glass is again made red-hot, and spun round rapidly, the hole increasing in size until it resemblesfig. 4. By continuing the rapid twirling of the rod, the hole opens wider and wider till at last one broad sheet is produced; it is then separated from the rod by putting a drop of cold water at its junction with the glass, which causes it to crack across at that part. It is now about six feet in diameter, perfectly round and flat, and when cold it is cut into halves and packed with straw in a “crate” for carriage. The knot of glass often seen in kitchen or stable windows, is the part in the centre of the glass where the iron rod has joined it, and is called the “punty.”(‡ Elongated Blow Glass.)FIG.5.(‡ Grinding The Plate Glass.)FIG.6.(‡ Polishing The Plate Glass.)FIG.7.Sheet-glass is commenced in the same way as crown, but instead of a hole being made the blowing is continued till a great round ball is formed, the rod and this ball are then swung round at arm’s length—a hole being sunk in the ground for the purpose—which causes the globe to become elongated, as infig. 5. It is then laid upon an iron table, and rapidly slit up, the compressed air escaping from within opening it out into a broad sheet, which is instantly cut square while yet soft.PLATE GLASS CASTING.BRINGING OUT THE POT.(‡ Blowing Glass Into Form.)FIG.8.Plate glass is cast by pouring it from a large pot on to a flat iron table with a ridge all round it, and on which an iron roller is so placed that when the molten glass flows on the table it passes over and flattens it out to the required thinness, which is regulated by elevating or depressing the ridges at the sides of the table, made moveable for that purpose (the process is illustrated by the cut at theheadof this article). When cold, the surface of the plate is ground perfectly flat and even by means of emery-powder (fig. 6), and then polished with a cloth rubber charged with a fine red oxide of iron called “crocus” (fig. 7). The grinding and polishing are both performed by steam machinery.Bottles, and such like articles are either simply blown into the form required, or into moulds made to close upon the ball of soft glass, and again open when the required form has been given (fig. 8).Many articles of glass are cast, or “struck-up” by compression in a mould, and are often made to resemble cut-glass articles, but they are much inferior in appearance. The best articles of glass are first blown, and afterwards cut and polished (see “Glass-cutting”). Of whatever kind the article of glass may be, it is so brittle that the slightest blow would break it, a bad quality which is got rid of by a process called “annealing.” This consists in placing it while quite hot on the floor of an oven, which is allowed to cool very gradually indeed. This slow cooling takes off the brittleness; and articles of glass well annealed, will scarcely break with boiling water, and are very much tougher than others.

CASTING PLATE GLASS.

(‡ Collecting Glass With A Puntil.)FIG.1.(‡ Beginning Glass Form.)FIG.3.(‡ Glass Globe With Hole At End.)FIG.4.

(‡ Collecting Glass With A Puntil.)FIG.1.

FIG.1.

(‡ Beginning Glass Form.)FIG.3.

FIG.3.

(‡ Glass Globe With Hole At End.)FIG.4.

FIG.4.

(‡ Blowing On The Puntil.)FIG.2.

FIG.2.

Glass-blowing requires great practice and manual dexterity, for the material used being red-hot cannot be touched with the hands, and has to be very rapidly worked, or it becomes cooled and hard; to any one unused to work with it, it is the most unmanageable material conceivable, but by practice the glass-blower contrives to produce almost any form required, and of a size quite astonishing—as, for instance, the globular bottles seen in druggists’ windows, which often hold twelve gallons, also glass shades, which are of an uniform thickness, and two or three feet high. This is all done by means of a hollow rod of iron called a “puntil,” on the one end of which a mass of molten glass is collected (fig. 1), and the workman blows into the other, at the same time turning the tube rapidly round in his hands (fig. 2). When the kind of glass called “crown-glass” has to be made, the end of the iron tube is put into the pot of melted glass, and turned round till a ball of it is collected about the size of one’s head, the workman then blows in at the other end, still turning the rod in his hands; it has now the appearance presented atfig. 3. An iron rod is stuck on to the side of the globe opposite to the “puntil,” which is then pulled suddenly away, leaving a round hole. The globe of glass is again made red-hot, and spun round rapidly, the hole increasing in size until it resemblesfig. 4. By continuing the rapid twirling of the rod, the hole opens wider and wider till at last one broad sheet is produced; it is then separated from the rod by putting a drop of cold water at its junction with the glass, which causes it to crack across at that part. It is now about six feet in diameter, perfectly round and flat, and when cold it is cut into halves and packed with straw in a “crate” for carriage. The knot of glass often seen in kitchen or stable windows, is the part in the centre of the glass where the iron rod has joined it, and is called the “punty.”

(‡ Elongated Blow Glass.)FIG.5.(‡ Grinding The Plate Glass.)FIG.6.(‡ Polishing The Plate Glass.)FIG.7.

(‡ Elongated Blow Glass.)FIG.5.

FIG.5.

(‡ Grinding The Plate Glass.)FIG.6.

FIG.6.

(‡ Polishing The Plate Glass.)FIG.7.

FIG.7.

Sheet-glass is commenced in the same way as crown, but instead of a hole being made the blowing is continued till a great round ball is formed, the rod and this ball are then swung round at arm’s length—a hole being sunk in the ground for the purpose—which causes the globe to become elongated, as infig. 5. It is then laid upon an iron table, and rapidly slit up, the compressed air escaping from within opening it out into a broad sheet, which is instantly cut square while yet soft.

PLATE GLASS CASTING.BRINGING OUT THE POT.(‡ Blowing Glass Into Form.)FIG.8.

PLATE GLASS CASTING.BRINGING OUT THE POT.

(‡ Blowing Glass Into Form.)FIG.8.

FIG.8.

Plate glass is cast by pouring it from a large pot on to a flat iron table with a ridge all round it, and on which an iron roller is so placed that when the molten glass flows on the table it passes over and flattens it out to the required thinness, which is regulated by elevating or depressing the ridges at the sides of the table, made moveable for that purpose (the process is illustrated by the cut at theheadof this article). When cold, the surface of the plate is ground perfectly flat and even by means of emery-powder (fig. 6), and then polished with a cloth rubber charged with a fine red oxide of iron called “crocus” (fig. 7). The grinding and polishing are both performed by steam machinery.

Bottles, and such like articles are either simply blown into the form required, or into moulds made to close upon the ball of soft glass, and again open when the required form has been given (fig. 8).

Many articles of glass are cast, or “struck-up” by compression in a mould, and are often made to resemble cut-glass articles, but they are much inferior in appearance. The best articles of glass are first blown, and afterwards cut and polished (see “Glass-cutting”). Of whatever kind the article of glass may be, it is so brittle that the slightest blow would break it, a bad quality which is got rid of by a process called “annealing.” This consists in placing it while quite hot on the floor of an oven, which is allowed to cool very gradually indeed. This slow cooling takes off the brittleness; and articles of glass well annealed, will scarcely break with boiling water, and are very much tougher than others.

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