(a) - Before a work of art can be cast in bronze, it must be in existence in some other material, and it may not be altogether superfluous to describe briefly the various stages an article must pass before it can be introduced to the world as a bronze. The sculptor usually embodies his first idea in a sketch, not, however, in most cases on paper, but in wax or clay. A sculptor's sketch is simply a statuette, very roughly modelled, and usually not more than 5 or 6 in. high. Works of this size do not require any internal framing for their support, and therefore lend themselves readily to any changes of design, even of the most radical description.

The attitude of the figure, the principle, masses of drapery, and, in short, the general arrangement of the composition having been decided on, the next step is the construction of a full-sized framing 'of iron, without which the statue in plastic clay or wax could not stand, but would yield to its own weight, and sink a shapeless lump to the floor. With the assistance of the iron framing, or skeleton, running through every part, it can be preserved for a sufficient time - often for several years - to permit the artist to bring it to that perfection of which he is capable. But even then it is not to be regarded as a complete work; for the plastic material, whatever it may be, is certain to be destroyed by its very plasticity. Therefore, that it may be preserved, it must undergo a transformation which will render it hard and durable. If the statue has been modelled in a certain manner, and with specially prepared clay, the action of Are will produce this result, and then we call it terra-cotta. The only other method of preserving the model is to cast it.

By this means, although the plastic model is destroyed, a facsimile is produced in another and more durable material.

Casting involves 5 processes: -

1. The construction of the hollow mould.

2. The preparation of the fluid material.

3. The casting or pouring into the mould.

4. The solidification in the mould.

5. The liberation of the cast from the mould.

A mould is made over a piece of sculpture by the application of some soft material which has the property of rapidly becoming hard. By this means a concave impression is obtained, from which again, by a similar process, a convex facsimile of the original model may be produced. There are many kinds of moulds used by artists. The sculptor roughly divides all moulds into simple and piece mouldi. A simple mould is made all in one, without any loose parts, like a seal, or a pastrycook's jelly mould. A piece mould, on the contrary, is made of two or more parts, according to the requirements of the work. Moulds are also called open" or "closed." An open mould is one of which one side only receives an impression. Simple moulds are, for instance, usually open moulds, so Also are piece moulds of bas-reliefs or other flat objects. A close mould is almost always a piece mould, it may or may not be a safe mould. A safe mould is made up of ninny separate parts, so constructed as to he easily withdrawn from each other. These moulds can be used many times over without injury either to themselves or to the cast - hence their name " safe." A waste mould is made of one or of many pieces, but it can be used only once; it is destroyed or wasted in the process of casting.

Some open moulds are shown in Fig. 197: A, the cast; 11, the cope or case of mould; C, the loose pieces of mould.

Moulds are made of Terr various materials, according to the objects for which they are constructed. Plaster is the most common, but wax and gelatine are also much 'used by artists. For bronze founding, the foregoing materials are unavailable. The sculptor who would cast in bronze must use a material that will resist the intense heat of the liquid metal. Moulds for metal casting are made of sand and loam, of lulu or patie, or, for small works, of compo.

Supposing an artist has completed a statue, and, having already cast it in plaster, wishes to reproduce it in bronze. If this work is of large dimensions, it is very unlikely that he will have suitable premises for the purpose, for although small works can be cast almost anywhere, no casting on a large scale can be reasonably undertaken unless asuitable foundryis available. Such a foundry should consist of a large and lofty room about 40 ft. long by 24 ft. wide, the larger indeed the better. A row of small furnaces should be built along the wall at one end, and at the other end should be situated the rever-beratory furnace for large work, whilst a very large portion of the floor should be occupied by the " pit." The small furnaces before mentioned are draft furnaces of the ordinary type, and are made to take crucibles up to about 60 lb. capacity. By pouring the contents of several crucibles together, castings of considerable size can be made, even with these small furnaces. Larger quantities than can be conveniently melted in the small furnaces must be treated in the* reverberator, which is occasionally made of very great capacity.

Simple close waste mould.

Simple close waste mould.

Metal Work Brozes 500134

The "pit" is used to bury the moulds previously to casting. This is with a twofold object; partly that the pressure of the earth outside the mould may enable it to resist the pressure of the metal from within; and also in order that the openings through which the metal is poured may be placed at a convenient level, which would not be the case if large moulds rested on the floor of the foundry.

Besides the large and small furnaces and the pit, the artist would also require at least one blacksmiths' forge and a powerful crane, not to mention drying stoves and pugging mills, and store-rooms for various purposes. It is extremely unlikely that the artist will be in possession of such premises and plant. It follows then that he must, as a rule, consign his larger works to one of the commercial foundries for execution. Nor is there any very great hardship in this. It is in such cases only requisite that the great lines and masses should be faithfully reproduced. Any delicacy of touch that might be put into such a work would be useless, because it could not be seen, and, therefore, would not be missed in the casting. It occasionally does happen, however, that such premises are at the artist's disposal, and in this case, the best work is certainly expected of him.