The character of work is influenced by the nature of the material in which the sculptor carves; the harder the stone the more difficult to give it the pliant forms of life. It is remarkable that the most ancient and perfect Egyptian statues should have been formed of very hard stones; and, as the ancient Egyptians were not acquainted with steel, they must have been dependent upon bronze, of various degrees of hardness, for their cutting tools. These works are remarkable for their excellence, both of form and proportion, and in the finish given to the details of feature, the dress, and the ornaments.
Assyrian sculpture was in softer stones, limestones and alabaster; only small objects, such as seals, being worked in hard stones.
Greek and Roman sculptors made many statues and bas-reliefs in hard stones, such as basalt, granite, and porphyry. The extreme difficulty of such work may be understood when it is seen that the ordinary method of the chisel and mallet, in the most skillful hands, would be quite unavailing in this hard material. The treadle-wheel, the drill, and the file, are brought to aid the chisel, and even these require the use of emery upon the wheel of the lapidary, in the manner in which the hardest stones are cut.
Clay modeled and dried in the sun, or hardened by the fire, was naturally one of the early forms in which sculpture was developed. At once ready to hand, and easily modeled, it was adopted for the same reasons that made clay convenient for the ordinary vessels of every-day use. We find countless numbers of these baked, or sun-dried clay figures. They have escaped destruction because of the little value of the material and because they resist decay. The Egyptians and Assyrians applied a vitreous glaze to terra-cotta objects, which made them more decorative and more durable.
Terra-cotta was chosen by many sculptors to preserve the spirit and freedom of the original. Although some shrinking under the action of the fire must be allowed for, yet what is well baked is certain to possess the excellence of the fresh clay. It escapes the chances of over-finish, which too often befalls marble and bronze.
Another form of sculpture to be noticed is called chryselephantine, on account of the combined use of gold and ivory; the nude parts of the figure being of ivory, probably with color applied to the features and the drapery of gold. The statue was substantially but roughly made in marble, with wood, perhaps, upon it; the ivory being laid on in thick pieces.
Statues of wood, of various kinds, were made by the most ancient sculptors. Many small figures in wood, the work of the Egyptian carvers, are to be seen in the museums, and the mummy cases show the practice of carving the head, while the trunk is left only partly shaped out of the block.
Bronze was one of the most important forms of ancient statuary. It must be remembered that bronze is an entirely different alloy from brass, the former being an alloy of copper and tin, while brass is of copper and zinc. Small proportions of gold, silver, lead, and iron, were mixed with the bronze by ancient metal-workers to give various colors to their work; thus a blush of shame was produced by allowing the iron in the bronze to rust. Plutarch mentions a face which was pale, the sculptor having mixed silver with the bronze.
The primitive bronze-workers, before they arrived at the knowledge of casting, began by hammering solid metals into shapes. The toreutic art, although not definitely known at present, was probably that of hammering, punching, and chiseling plates of metal, either separately or with a view of fixing them upon stone or wood. Both the solid hammered work and the hollow-plate work is mentioned by the authorities. The hollow statues were built up in pieces, fastened together with nails, rivets, and dove-tails, and it is not improbable that some system of welding was practiced.
The casting of metals in moulds must have followed the discovery that they could be melted. As the sculptor improved in his art of modeling he would be able to make better moulds. He would soon observe that the solid statue was not only very costly, but so very heavy that the whole figure would collapse from sheer weight.