9. When the subject is a bas-relief, or any other one-sided figure of a similar kind, the mould can be withdrawn without injury, in a single piece; but if it is a statue, or any other figure of like form, it is necessary to divide the mould into several pieces, in order to a safe removal. These pieces again united constitute a perfect mould. While the artist is forming the mould on the face of a living person, the latter breathes through tubes inserted into the nostrils.
10. In taking casts from such a mould, the internal surface is oiled to prevent adhesion, and then plaster mixed with water is poured into it through a small orifice. The mould is afterwards turned in every direction, that the plaster may cover every part of the surface; and when a sufficiency of it has been distributed to produce the requisite strength, and the plaster has acquired the proper solidity, the several pieces are removed from the cast, which, of course, is an exact resemblance of the subject on which the mould was formed.
11. Superfluous portions of the material, produced by the seams in the mould, are removed with suitable instruments, and applications of fresh plaster are made, where necessary to repair blemishes. The cast is finished by dipping it in a varnish made of soap, white wax, and water, and afterwards rubbing it with soft linen. The polish produced in this manner, approaches that of marble.
12. The durability of plaster casts, exposed to the weather, is greatly increased by saturating them with linseed oil combined with wax or rosin. They are made to resemble bronze by the application of a soap composed of linseed oil and soda, and colored with the sulphate of copper and iron.
13. Moulds are, also, formed of a warm solution of glue, which hardens upon cooling, and such are called elastic moulds. This material is sometimes preferred on account of its more easy separation from irregular surfaces. For small and delicate impressions in bas-relief, melted sulphur is sometimes employed; also a strong solution of isinglass in proof spirits. All three of the substances last mentioned yield sharper impressions than plaster of Paris.
14. Statues designed to occupy situations in which they may be exposed to the weather and mechanical violence, are often made of bronze cast in moulds. The external portions of the mould are made on the pattern, out of plaster, brick-dust, and water. The mould is then covered on the inside with a coating of clay as thick as the bronze is intended to be, and the several pieces are afterwards put together, or closed. The internal cavity is next filled with a composition like that on the other side of the clay.
15. When this has been done, the several pieces forming the outside of the mould are separated, and the clay carefully removed. These having been again united, and the core or internal portion of the mould secured in its true position, the whole is bound with iron hoops, and thoroughly dried. The melted bronze is poured into the cavity formed by the removal of the clay, through an aperture made for the purpose. The cast is afterwards rendered smooth by mechanical means.
16. It is conjectured with much reason, that sculpture was one of the arts practised before the deluge, and that it was transmitted to posterity by the survivors of that catastrophe. The first images were probably made for the purpose of perpetuating the memory of the dead; but, in process of time, they became objects of adoration. As the Chaldeans were unquestionably the first idolators after the flood, so are they supposed to have been the first who made progress in sculpture.
17. The first notice of this art in the Mosaic writings, is found in the passage relative to the teraphim, or idols, which Rachel, the wife of Jacob, carried clandestinely from her father's house; and the first persons mentioned in the Bible, as artists, are Aholiab and Bezaleel, who formed the cherubim which covered the mercy-seat, together with some other furniture of the tabernacle, and the sculptured ornaments of the garments of the high-priest.
18. From the same authority, we learn that the nations expelled from Canaan, by the Jewish people, were not ignorant of sculpture and painting; for Moses repeatedly commands the latter to destroy the pictures and molten images which might be discovered in their progress through the land. The Israelites crossed the river Jordan about 1500 years before the commencement of our era.