FOUNDRY of Statues

FOUNDRY of Statues. The casting of statues depends on the due preparation of the pit, the core, the wax, the outer mould, the inferior furnace to melt off the wax, and the upper to fuse the metal. The pit is a hole dug in a dry place something deeper than the intended figure, and made according to the prominence of certain parts thereof. The inside of the pit is commonly lined with stone or brick; or when the figure is very large, they sometimes work on the ground, and raise a proper fence to resist the impulsion of the melted metal.

The inner mould, or core, is a rude mass to which is given the intended attitude and contours. It is raised on an iron grate, strong enough to sustain it, and is strengthened within by several bars of iron. It is generally made either of potters clay, mixed with hair and horse dung; or of plaster of Paris mixed with brick dust. The use of the core is to support the wax, the shell, and lessen the weight of the metal. The iron bars and the core are taken out of the brass figure through an aperture left in it for that purpose, which is soldered up afterwards. It is necessary to leave some of the iron bars of the core, that contribute to the steadiness of the projecting part, within the brass figure.

The wax is a representation of the intended statue. If it be a piece of sculpture, the wax should be all of the sculptor's own hand, who usually forms it on the core: Though it may be wrought separately in cavities, moulded on a model, and afterwards arranged on the

ribs of iron over the grate; filling the vacant space in the middle with liquid plaster and brick dust, whereby the inner core is proportioned as the sculptor carries on the wax.

When the wax, which is the intended thickness of the metal, is finished, they fill small waxen tubes perpendicular to it from top to bottom, to serve both as canals for the conveyance of the metal to all parts of the work; and as vent holes, to give passage to the air, which would otherwise occasion great disorder when the hot metal came to encompass it.

The work being brought thus far, must be covered with its shell, which is a kind of crust laid over the wax, and which being of a soft matter, easily receives the impression of every part, which is afterwards communicated to the metal upon its taking the place of the wax, between the shell and the mould. The matter of this outer mould is varied according as different layers are applied. The first is generally a composition of clay, and old white crucibles well ground and sifted, and mixed up with water to the consistence of a colour fit for painting: accordingly they apply it with a pencil, laying it seven or eight times over, and letting it dry between whiles. For the second impression they add horse dung and natural earth to the former composition. The third impression is only horse dung and earth. Lastly, The shell is finished by laying on several more impressions of this last matter, made very thick with the hand.

The shell, thus finished, is secured by several iron girdles, bound round it, at about half a foot distance from each other, and fastened at the bottom to the grate under the statue, and at top to a circle of iron where they all terminate.

If the statue be so big that it would not be easy to move the moulds with safety, they must be wrought on the spot where it is to be cast. This is performed two ways: in the first, a square hole is dug under ground, much bigger than the mould to be made therein, and its inside lined with walls of free-stone or brick. At the bottom is made a hole of the same materials, with a kind of furnace, having its aperture outwards: in this is a fire made to dry the mould, and afterwards melt the wax. Over this furnace is placed the grate, and upon this the mould, &c. formed as above. Lastly, At one of the edges of the square pit, is made another large furnace to melt the metal. In the other way, it is sufficient to work the mould above ground, but with the like precaution of a furnace and grate underneath. When finished, four walls are to be run around it, and by the side thereof a massive made for a melting furnace. For the rest, the method is the same in both. The mould being finished, and enclosed as described, whether under ground or above it, a moderate fire is lighted in the furnace under it, and the whole covered with planks, that the wax may melt gently down, and run out at pipes contrived for that purpose, at the foot of the mould, which are afterwards exactly closed with earth, so soon as the wax is carried off. This done, the hole is filled up with bricks thrown in at random, and the fire in the furnace augmented, till such time as both the bricks and mould become red hot. After this, the fire being extinguished, and every thing cold again, they

Foundery. they take out the bricks, and fill up their place with earth moistened, and a little beaten at the top of the mould, in order to make it the more firm and steady. These preparatory measures being duly taken, there remains nothing but to melt the metal, and run it into the mould. This is the office of the furnace above described, which is commonly made in the form of an oven with three apertures, one to put in the wood, another for a vent, and a third to run the metal out at. From this last aperture, which is kept very close while the metal is in fusion, a small tube is laid, whereby the melted metal is conveyed into a large earthen bason, over the mould, into the bottom of which all the big branches of the jets, or casts, which are to convey the metal into all the parts of the mould, are inserted.

These casts or jets are all terminated with a kind of plugs, which are kept close, that, upon opening the furnace, the brass, which gushes out with violence, may not enter any of them, till the bason be full enough of matter to run into them all at once. Upon which occasion they pull out the plugs, which are long iron rods with a head at one end, capable of filling the whole diameter of each tube. The whole of the furnace is opened with a long piece of iron fitted at the end of each pole, and the mould filled in an instant. This completes the work in relation to the casting part; the rest being the sculptor's or carver's business, who, taking the figure out of the mould and earth wherewith it is encompassed, saws off the jets with which it appears covered over, and repairs it with chisels, gravers, panchons, &c.

Foundery of Bells. The metal, it is to be observed, is different for bells from what it is for statues; there being no tin in the statue metal; but there is a fifth, and sometimes more, in the bell metal.

The dimensions of the core and the wax, for bells, if a chime of bells especially, are not left to chance, but must be measured on a scale, or diapason, which gives the height, aperture, and thickness, necessary for the several tones required.

It is on the wax that the several mouldings and other ornaments and inscriptions, to be represented in relief on the outside of the bell, are formed. The clapper or tongue is not properly part of the bell, but is furnished from other hands. In Europe, it is usually of iron, with a large knob at the extreme; and is suspended in the middle of the bell. In China, it is only a huge wooden mallet, struck by force of arm against the bell; whence they can have but little of that consonancy so much admired in some of our chimes of bells. The Chinese have an extraordinary way of increasing the sound of their bells, viz. by leaving a hole under the cannon; which our bell-founders would reckon a defect.

The proportions of our bells differ very much from those of the Chinese. In ours, the modern proportions are, to make the diameter 15 times the thickness of the brim, and the height 12 times. The parts of a bell are, 1. The sounding bow, terminated by an inferior circle, which grows thinner and thinner. 2. The brim or that part of a bell whereon the clapper strikes, and which is thicker than the rest. 3. The outward

sinking of the middle of the bell, or the point under Foundery. which it grows wider to the brim. 4. The waist or furniture, and the part that grows wider and thicker quite to the brim. 5. The upper vase, or that part which is above the waist. 6. The pallet which supports the staple of the clapper within. 7. The bent and hollowed branches of metal uniting with the cannons, to receive the iron keys, whereby the bell is hung up to the beam, which is its support and counterpoise when rung out.

The business of bell foundery is reducible to three particulars. 1. The proportion of a bell. 2. The forming of the mould. And, 3. The melting of the metal. There are two kinds of proportions, viz. the simple and the relative; the former are those proportions only that are between the several parts of a bell to render it sonorous; the relative proportions establish a requisite harmony between several bells.

The method of forming the profile of a bell, previous to its being cast, in which the proportion of the several parts may be seen, is as follows: the thickness of the brim, $C\_1$ (Plate CCXXIII.) is the foundation of every other measure, and is divided into three equal parts. First, draw the line $HD$, which represents the diameter of the bell; bisect it in $F$, and erect the perpendicular $Ff$; let $DF$ and $HF$ be also bisected in $E$ and $G$, and two other perpendiculars $Ee$, $Gg$, be erected at $E$ and $G$: $GE$ will be the diameter of the top or upper vase, i. e. the diameter of the top will be half that of the bell; and it will, therefore, be the diameter of a bell which will sound an octave to the other. Divide the diameter of the bell or the line $HD$ into 15 equal parts, and one of these will give $C\_1$ the thickness of the brim; divide again each of these 15 equal parts into three other equal parts, and then form a scale. From this scale take $\backslash frac\{1\}\{2\}$ of the larger divisions or $\backslash frac\{1\}\{3\}$ of the whole scale in the compass, and setting one leg in $D$ describe an arc to cut the line $Ee$ in $N$; draw $ND$, and divide this line into 12 equal parts; at the point 1 erect the perpendicular $1C\; =\; 10$, and $C\_1$ will be the thickness of the brim $=\; \backslash frac\{1\}\{15\}$ of the diameter: draw the line $CD$; bisect $DN$; and at the point of bisection erect the perpendicular $6K\; =\; 1\backslash frac\{1\}\{2\}$ of the larger divisions on the scale. With an opening of the compass equal to twice the length of the scale or 30 brims, setting one leg in $N$, describe an arc of a circle, and with the same leg in $K$ and the same opening describe another arc to intersect the former: on this point of intersection as a centre, and with a radius equal to 30 brims, describe the arc $NK$; in $6K$ produced take $KB\; =\; \backslash frac\{1\}\{2\}$ of the larger measure of the scale or $\backslash frac\{1\}\{3\}$ of the brim, and on the same centre with the radius 30 brims describe an arc $AB$ parallel to $NK$. For the arc $BC$, take 12 divisions of the scale or 12 brims in the compass; find a centre, and from that centre, with this opening, describe the arc $BC$, in the same manner as $NK$ or $AB$ were described. There are various ways of describing the arc $Kp$; some describe it on a centre at the distance of nine brims from the points $p$ and $K$; others, as it is done in the figure, on a centre at the distance only of seven brims from those points. But it is necessary first to find the point $p$, and to determine the rounding of the

Foundry. the bell $p\; r$. For this purpose, on the point $C$ as a centre, and with the radius $C\; r$, describe the arc $r\; p\; n$; bisect the part $r,\; 2$ of the line $D\; n$, and erecting the perpendicular $p\; m$, this perpendicular will cut the arc $r\; p\; n$ in $m$, which terminates the rounding $r\; p$. Some founders make the bendings $K$ a third of a brim lower than the middle of the line $D\; N$; others make the part $C\; r\; D$ more acute, and instead of making $C\; r$ perpendicular to $D\; N$ at $r$, draw it $\backslash frac\{1\}\{3\}$th of a brim higher, making it still equal to one brim; so that the line $r\; D$ is longer than the brim $C\; r$. In order to trace out the top part $N\; a$, take in the compass eight divisions of the scale or eight brims, and on the points $N$ and $D$ as centres, describe arcs to intersect each other in $8$: on this point $S$, with a radius of eight brims, describe the arc $N\; b$; this arc will be the exterior curve of the top or crown: on the same point $S$ as a centre, and with a radius equal to $7\backslash frac\{1\}\{3\}$ brims, describe the arc $A\; c$, and this will be the interior curve of the crown, and its whole thickness will be one-third of the brim. As the point $S$ does not fall in the axis of the bell, a centre $M$ may be found in the axis, by describing, with the interval of eight brims on the centres $D$ and $H$, arcs which will intersect in $M$; and this point may be made the centre of the inner and outer curves of the crown as before. The thickness of the cap which strengthens the crown at $Q$ is about one-third of the thickness of the brim; and the hollow branches or ears about one-sixth of the diameter of the bell. The height of the bell in proportion to its diameter as $12$ to $15$, or in the proportion of the fundamental sound to its third major: whence it follows, that the sound of a bell is principally composed of the sound of its extremity or brim as a fundamental, of the sound of the crown which is an octave to it, and of that of the height which is a third.

The particulars necessary for making the mould of a bell are, 1. The earth: the most cohesive is the best; it must be well ground and sifted, to prevent any chinks. 2. Brick stone; which must be used for the mine, mould, or core, and for the furnace. 3. Horse dung, hair, and hemp, mixed with the earth, to render the cement more binding. 4. The wax for inscriptions, coats of arms, &c. 5. The tallow equally mixed with the wax, in order to put a slight lay of it upon the outer mould, before any letters are applied to it. 6. The coals to dry the mould.

For making the mould, they have a scaffold consisting of four boards ranged upon tressels. Upon this they carry the earth, grossly diluted, to mix it with horse dung, beating the whole with a large spatula.

The compasses of construction is the chief instrument for making the mould, which consist of two different legs joined by a third piece. And last of all the founders shelves, on which are the engravings of the letters, cartridges, coats of arms, &c.

They first dig a hole of a sufficient depth to contain the mould of the bell, together with the case or cannon, under ground; and about six inches lower than the terrepain, where the work is performed. The hole must be wide enough for a free passage between the mould and walls of the hole, or between one mould and another, when several bells are to be cast. At

the centre of the hole is a stake erected, that is strongly fastened in the ground. This supports an iron peg, on which the pivot of the second branch of the compasses turns. The stake is encompassed with a solid brick-work, perfectly round, about half a foot high, and of the proposed bell's diameter. This they call a millstone. The parts of the moulds are, the core, the model of the bell, and the shell. When the outer surface of the core is formed, they begin to raise the core, which is made of bricks that are laid in courses of equal height upon a lay of plain earth. At the laying of each brick, they bring near it the branch of the compasses on which the curve of the core is shaped, so as that there may remain between it and the curve the distance of a line, to be afterwards filled up with layers of cement. The work is continued to the top, only leaving an opening for the coals to bake the core. This work is covered with a layer of cement, made of earth and horse dung; on which they move the compasses of construction, to make it of an even smoothness everywhere.

The first layer being finished, they put the fire to the core, by filling it half with coals, through an opening that is kept shut, during the baking, with a cake of earth that has been separately baked. The first fire consumes the stake, and the fire is left in the core half, or sometimes a whole day: the first layer being thoroughly dry, they cover it with a second, third, and fourth; each being smoothed by the board of the compasses, and thoroughly dried before they proceed to another.

The core being completed, they take the compasses to pieces, with intent to cut off the thickness of the model, and the compasses are immediately put in their place to begin a second piece of the mould. It consists of a mixture of earth and hair, applied with the hand on the core, in several cakes that close together. This work is finished by several layers of a thinner cement of the same matter, smoothed by the compasses, and thoroughly dried before another is laid on. The first layer of the model is a mixture of wax and grease spread over the whole. After which are applied the inscriptions, coats of arms, &c. besmeared with a pencil dipped in a vessel of wax in a chafing dish: this is done for every letter. Before the shell is begun, the compasses are taken to pieces, to cut off all the wood that fills the place of the thickness to be given to the shell.

The first layer is the same earth with the rest, sifted very fine: while it is tempering in water, it is mixed with cows hair to make it cohere. The whole being a thin cullis, is gently poured on the model, that fills exactly all the sinuities of the figures, &c. and this is repeated till the whole is two lines thick over the model. When this layer is thoroughly dried, they cover it with a second of the same matter, but somewhat thicker; when this second layer becomes of some consistence, they apply the compasses again, and light a fire in the core, so as to melt off the wax of the inscriptions, &c.

After this, they go on with other layers of the shell, by means of the compasses. Here they add to the cows hair a quantity of hemp, spread upon the layers, and afterwards smoothed by the board of the compasses.

Foundry. passes. The thickness of the shell comes to four or five inches lower than the millstone before observed, and surrounds it quite close, which prevents the extravasation of the metal. The wax should be taken out before the melting of the metal.

The ear of the bell requires a separate work, which is done during the drying of the several incrustations of the cement. It has seven rings: the seventh is called the bridge, and unites the others, being a perpendicular support to strengthen the curves. It has an aperture at the top, to admit a large iron peg, bent at the bottom; and this is introduced into two holes in the beam, fastened with two strong iron keys. There are models made of the rings, with masses of beaten earth, that are dried in the fire in order to have the hollow of them. Those rings are gently pressed upon a layer of earth and cow hair, one half of its depth; and then taken out, without breaking the mould. This operation is repeated 12 times for 12 half moulds, that two and two united may make the hollows of the six rings: the same they do for the hollow of the bridge, and bake them all to unite them together.

Upon the open place left for the coals to be put in are placed the rings that constitute the ear. They first put into this open place the iron ring to support the clapper of the bell; then they make a round cake of clay, to fill up the diameter of the thickness of the core. This cake, after baking, is clapt upon the opening, and soldered with a thin mortar spread over it, which binds the cover close to the core.

The hollow of the model is filled with an earth, sufficiently moist to fix on the place, which is strewed at several times upon the cover of the core; and they beat it gently with a pestle, to a proper height; and a workman smooths the earth at top with a wooden trowel dipped in water.

Upon this cover, to be taken off afterwards, they assemble the hollows of the rings. When every thing is in its proper place, they strengthen the outside of the hollows with mortar, in order to bind them with the bridge, and keep them steady at the bottom, by means of a cake of the same mortar, which fills up the whole aperture of the shell. This they let dry, that it may be removed without breaking. To make room for the metal, they pull off the hollows of the rings, through which the metal is to pass, before it enters into the vacuity of the mould. The shell being unloaded of its ear, they range under the millstone five or six pieces of wood, about two feet long, and thick enough to reach almost the lower part of the shell; between these and the mould, they drive in wooden wedges with a mallet, to shake the shell of the model whereon it rests, so as to be pulled up and got out of the pit.

When this and the wax are removed, they break the model and the layer of earth, through which the metal must run, from the hollow of the rings, between the shell and the core. They smoke the inside of the shell, by burning straw under it, that helps to smooth the surface of the bell. Then they put the shell in the place, so as to leave the same interval between that and the core; and before the hollows of the rings or the cap are put on again, they add two vents, that are united to the rings, and to each other, by a mass of baked cement. After which they put on this mass of

the cap, the rings, and the vent, over the shell, and solder it with thin cement, which is dried gradually by covering it with burning coals. Then they fill up the pit with earth, beating it strongly all the time round the mould.

The furnace has a place for the fire, and another for the metal. The fire-place has a large chimney with a spacious ash-hole. The furnace which contains the metal is vaulted, whose bottom is made of earth, rammed down; the rest is built with brick. It has four apertures; the first, through which the flame vibrates; the second is closed with a stopple that is opened for the metal to run; the others are to separate the dross or scoriae of the metal by wooden rakes: through these last apertures passes the thick smoke. The ground of the furnace is built sloping, for the metal to run down.

FOUNDERY of Great Guns and Mortar Pieces. The method of casting these pieces is little different from that of bells; they are run massy, without any core, being determined by the hollow of the shell; and they are afterwards bored with a steel trepan, that is worked either by horses or a water-mill.

For the metal, parts, proportions, &c. of these pieces, see GUNNERY.