FOUNDERY 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 (lug in a dry place, something deeper than the intended fi gure, and made according to the promi nence 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 impul sion of the melted metal.
The inner mould, or core, is a rude mass, to which is given the intended at titude 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 potter's 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 in tended statue. if it be a piece of sculp ture, the wax should be all of the sculp tor's own band who usually forms it on the core ; though it may be wrought se parately. 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 ca nals 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 broughtthus far, must be covered with its shell, which is a kind of crust laid over the wax, and which, be ing of a soft matter, easily receives the impression olevery part, which is after wards 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 consist ence of a colour fit for painting : accord ingly 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 gists 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 the 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 safe ty, 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 under neath. 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 Loth. The mould being finished, and in closed 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 ran dom, and the fire in the furnace augment ed, till such time as both the bricks and mould become red hot. After this, the fire being extinguished, and every thing cold again, they take out the bricks, and fill up their place with earth, moistened and a little beaten, to 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, an other 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 basin 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, ure inserted.