FOUNDERY, or Foundry, the art of melting and casting all sorts of metal, such as brass, iron, &c. See Brass-making, and Iron-making; also the article Furnace. Fovndery of Small Works, or Casting in Sand. The sand commonly used for casting small works is at first of a pretty soft, yellowish, and clammy nature; but it being necessary to strew charcoal dust in the mould, it at length becomes of a quite black colour. The sand is worked over and over, on a board, with a roller and a sort of knife; and is placed over a trough to receive it, after it has by these means been sufficiently prepared.

This being done, the workmen take a wooden board of a length and breadth proportional to the things to be cast, and putting a ledge round it, they fill it with sand a little moistened, to make it duly cohere. They then take either wood or metal models of what they intend to cast, and apply them to the mould, and press them into the sand so as to leave their impression there. Along the middle of the mould is laid half a small brass cylinder, as the chief canal for the metal to run through, when melted, into the models or patterns; and from this chief canal are placed several others, which extend collaterally to each model or pattern placed in the frame. After this frame is finished, they take out the patterns, by first loosening them all round, that the sand may not give way; then they proceed to work the other half of the mould with the same patterns in just such another frame, only that it has pins, which, entering into holes corresponding to it in the other, make the two cavities of the pattern fall exactly on each other.

The frame, thus moulded, is carried to the melter, who, after extending the chief canal of the counterpart, and adding the cross canals to the several models in both, and strewing mill dust over them, dries them in a kind of oven prepared for the purpose. Both parts of the mould being dry, they are joined together by means of the pins; and to prevent them giving way, by reason of the melted metal passing through the chief cylindrical canal, they are screwed or wedged up like a kind of press.

Whilst the moulds are thus preparing, the metal is fusing in a crucible of a size proportional to the quantity of metal intended to be cast. When the moulds have cooled, the frames are unscrewed or unweuged, and the cast work taken out of the sand, which sand is worked over again for other casting.

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 dug in a dry place, something deeper than the intended figure, and made according to the prominence of certain parts of it. The inside of the pit is commonly lined with stone or brick; but 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 grating 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 and 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, which 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 from the hand of the sculptor himself, 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 grating, filling the vacant space in the middle with liquid plaster and brick dust, by which means the inner core is proportioned as the sculptor carries on the wax. When the wax, which is of the intended thickness of the meta), is finished, small waxen tubes perpendicular to it from top to bottom are filled, 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; and it is applied with a pencil, by means of which it is laid on seven or eight times successively. For the second impression horse dung and natural earth are added to the former composition; but for the third impression only horse dung and earth are used. 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 girths bound round it, at about half a foot distant from each other, and fastened at the bottom to the grating under the statue, and at top to a circle of iron where they all terminate.

If the statue be so large that it would not be easy to move the moulds with safety, these must be wrought on the spot where it is to be cast. This is performed in two ways. In the first place, a square hole is dug in the ground, much larger than the mould to be made therein, and its inside is lined with walls of freestone or brick. At the bottom is made a hole of the same materials, with a kind of furnace, having its aperture outwards; and in this is a fire made, to dry the mould, and afterwards melt the wax. Over this furnace is placed the grating, and upon this the mould, 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 precaution of a furnace and grating underneath. When finished, four walls are run around it, and by its side a melting furnace is prepared. For the rest, the method is the same in both cases. The mould being finished, and enclosed as described, whether below ground or above it, a moderate [7:9:792]fire is lighted in the furnace under it, and the whole co vered 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, as soon as the wax is all carried off. When this is done, the whole is filled up with bricks thrown in at random, and the fire in the furnace augmented, until both the bricks and mould become red hot. The fire is then extinguished, and every thing being cold again, the bricks are taken out, and their place filled up with earth, moistened, and beaten a little at the top of the mould, in order to render it the firmer. These preparatory measures being duly taken, there remains nothing but to melt the metal, and run it into the mould. This is done by means 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 whilst the metal is in fusion, a small tube is laid, by which the molten metal is conveyed into a large earthen basin, over the mould, into the bottom of which all the large branches of the jets or casts, which are to convey the metal into the different parts of the mould, are inserted.

These casts or jets are all terminated with a kind of plugs, which are kept close, so that, upon opening the furnace, the brass, which rushes 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 then 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 is the sculptor’s or carver’s business, who, taking the figure out of the mould and earth with which it is encompassed, saws off the jets with which it appears covered over, and finishes it with chisels, gravers, puncheons, and other instruments.

Foundery of 'Betis. The metal for casting bells, it is to be observed, is different from that employed for casting statues; there being no tin in the statue metal, whereas in the bell metal there is a fifth, and sometimes more.

The dimensions of the core and the wax for bells, especially a chime, are not left to chance, but must be measured upon a scale, or diapason, which gives the height, the aperture, and the 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 bf the bell, but is furnished from other hands. In Europe it is usually of iron, with a large knob at the extremity; and is suspended in the middle of the bell. In China it is only a huge wooden mallet, struck by the hand against the bell; and hence they can have but little of that consonance so much admired in some of our chimes of bells. The Chinese have a method of increasing the sound of their bells, by leaving a hole under the cannon; but this 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 fifteen times the thickness of the brim, and the height twelve times. The parts of a bell are, first, the sounding bow, terminated by an inferior circle, which grows thinner and thinner; secondly, the brim, or that part of a bell whereon the clapper strikes, and which is thicker than the rest; thirdly, the outward sinking of the middle of the bell, or the point under which it grows wider to the brim; fourthly, the waist or furniture, and the part that grows wider end thicker quite to the brim; fifthly, the upper vase, or that part which is above the waist; sixthly, the pallet, which supports the staple of the clapper within; and, seventhly, the bent and hollowed branches of metal uniting with the cannons, to receive the iron keys, by which the bell is hung up to the beam, and which forms its support and counterpoise when rung out.

Without entering into the details of the operations, we may state, that the business of bell foundery is reducible to three heads; first, the proportion of a bell; secondly, the forming,of the mould; and, thirdly, the melting of the metal.

Foundeky of Great Guns and Mortar Pieces. See Cannon-Making. Letter Foundeky, or Casting of Printing Letters. See Printing arid Type-Making.