FOUNDING is the art of casting or forming of melted metal an infinite variety of articles to any given pattern or design ; and the place or building where the art is carried on is called a foundry. Foundries are, however, dis tinguished either by the metals they work or the articles they fabricate, such as brass foundries and iron foundries, bell and type foundries. As the methods of casting in one kind of metallic substance are very similar to those employed in others, we shall therefore describe at some length the art of founding as it is practised by the brass founders, and more briefly whatever is i peculiar in the processes adopted in the other branches of the art.
The operations of the brass founder are not limited to that peculiar yellow compound of copper and zinc, strictly termed brass, but to every variety of the alloys of copper, with tin and zinc in every proportion, according to the pur poses for which the article is required, or according to the motive of economy or profit of the manufacturer. Founders in brass require an exact model in wood, or otherwise, of the article to be founded ; and this is most frequently made in two parts, exactly joined together, and fitted by small pins, and the casting, in such a case, is performed by two operations, that is, one half at one time, and one half at another, and in the manner following ; viz. the founder provides himself with a yellowish sharp sand, which is required to be well washed, to free it from all earthy and other particles. This sand is prepared for use by a process called tewing, which consists in working up the sand in a moist state, over a board about one foot square, which is placed over a box to receive what may fall over in the tewing. A roller about two feet long and two inches in diameter is employed in rolling the sand about until it is brought into that state which is deemed for its business ; a long-bladed knife is also required to cut it in pieces. With the roller and the knife, the tewing is finished for use by being alternately rolled and cut. When the sand is so far prepared, the moulder provides himself with a table or board, which, in size, must be regulated by the castings about to be performed on it. The edges of the table or board are surrounded by a ledge, in order to support the tewed stuff; the table, so previously prepared, is filled up with the sand as high as the top of the ledge, which is in a moderately moistened state, and which must be pressed •closely down upon the table in every part. When the operation has so far advanced, the models must be all examined, to see that they are in a state to come nicely out of the mould, and if not found so, they must be cleaned or altered till the founder is satisfied with them. All models require the greatest accuracy in their making, or it will be vain to suppose any thing good can be performed by the founder. When the models are in a proper state to be founded, one half, generally longitudinally, is taken first, and this is applied on the mould, and pressed down mto the tewed stuff or sand, so as completely to leave its form indented on it, which must be very carefully looked to, and examined minutely, to see that there are no small holes, as every part in the indented sand must be a perfect cameo of the models submitted and pressed into it. If it should not be found perfect, new sand must be added, and the model re indented and pressed into it, till it leaves its impression in a state proper to receive the metal. In the same manner, other models intended to be founded on the same table must be prepared and indented into the sand. When the table is completely ready for the metal it is carried away to the melter, who himself examines its state, and also the cameos, and who lays along the middle of the mould the half of a small wire of brass, which he presses into the sand, so as to form a small channel for the melted brass to flow in, and which he terms the master jet or canal. It is so disposed as to meet the ledge on one side, and far enough to reach the last pattern on the other ; from this is made several lesser jets or branches, extending themselves to each pattern on the table, by which means the fluid metal is conveyed to all the different indented impres sions required to be cast on the table. When the work is so far forwarded it is deemed ready for the foundry ; but previously to this, the whole is sprinkled over with mill dust, and when it is so sprinkled the table is placed in an oven of moderate temperature till it gets dry, or in a state which is deemed proper to receive the melted brass. The first table being thus far completed, it is either turned upside down, and the moulds or patterns taken out, or the moulder begins to prepare another table exactly similar to the one he has just com pleted, in which he indents and presses the other half of the mould ; or he turns the table already finished, containing the first half of the patterns, upside down ; previously, however, to doing this, it will be necessary for him to loosen the pattern, which is fixed in the sand, a little all round, with any small instrument that will open away the sand from its edges, in order to its coming out of the table more easily. This economy in founding, of making one
half of each pattern to be cast answer the purpose of the whole pattern, is a very common practice in brass founding, and enables the manufacturer to sell his goods at a much cheaper rate than he would otherwise be enabled to do if he was obliged to have a full pattern of all goods to be founded. When he has loosened the sand from about the pattern, and taken it out of the first table, the work is proceeded in of preparing the counterpart or other half of the mould with the same pattern, or otherwise, and in a frame exactly corresponding with the former, excepting only that it is prepared with small pins to enter holes which are made in the first half of the model, to secure them together. When this counterpart table has been finished, and all the patterns indented in the sand, it is carried to the melter, who, after enlarging the principal jet of the counterpart, and making the cross jets to the various patterns, and sprinkling them as before with mill dust, it is set in the oven to be sufficiently dried to receive the liquid metal. When both parts are sufficiently dry, they are joined together by the pins, and to prevent these from being forced open by the pressure of the liquid metal, the tables are further secured by screwed bolts or wedges. The furnace for melting is somewhat similar to a smith's forge, with a chimney over it, and a pair of large bellows ; the hearth is of masonry or brickwork, secured by an outer rim of iron. The fire-place, which is in the centre, is a cavity of 12 to 18 inches square, and reaching down to the floor of the foun dry. The lowest part of this cavity constitutes the ash-pit and air-chamber, and is divided from the upper portion by an iron grating; on this the fuel is deposited, in the centre of which is placed a covered crucible, containing the metal under fusion, which is accelerated by keeping the fuel in which it is completely imbedded in vivid combustion by the continued action of the bellows. When the fusion is perfect the crucible is withdrawn from the fire by the caster, with a pair of long tongs adapted to gripe it firmly, and with which he pours into the master jet of each mould until they are filled. As soon as this is done water is sprinkled over the tables to cool and fix the metal ; after which the tables are unfastened, and the new castings taken out, to be finished by filing, scouring, burnishing, turning, &c. as the work may require. The sand is now taken out of the frames, to be worked up again for the next casting: by repeated use the sand becomes black, by the charcoal collected from the foundry, which does not, however, unfit it for further employment. To reduce the expense and weight of casting large masses in solid metal, recourse is often had to forming them hollow, which process is distinguished by the term core casting, as it is necessary to have a core or heart of nearly the shape of the external form of the pattern. This core is usually made of clay, mixed and kneaded with crucible dust, and is suspended by wires in its place, with a space around it to receive the metal ; in small articles, however, it is usual to fill up the space by coating the core to that extent with wax, which melts as the metal flows to supply its place. When the pattern is of a complicated form, and a difficulty arises in getting out the core, it is usually separated into several pieces, which are joined together after being cast. In many of the Birmingham manufactures the cores occupy so much of the pattern, that the metal left is not thicker than a shilling. The business of a brass founder, contrary to that of an iron founder, extends to the finishing of the articles he casts; and not only to this, but to the manufacture of brass goods that are not cast or founded at all, being made entirely from wrought or rolled metal. A large proportion of the Bir mingham manufacture of cabinet brass work is formed out of sheet metal, by pressure between dies after the manner of coining : such goods are in con sequence cheaply made, and frequently are impressed with very tasteful and elaborate designs. The castings, when taken out of the sand, have first to be cleaned up and completed, as they are seldom free from defects ; the cores are filed off, and the small cavities filled up with metal or solder; they are after wards finished, according to the nature of the article, by filing, turning, nishing, and lackering. The superior kinds of brass work are gilded, which preserves them better than tacker, and constitutes the article called or molu.