Page:An Elementary History of Art.djvu/195

 Processes. 1 65 Coins and Medals. — Gold, silver, copper, bronze, and oc- casionally other metals or combinations of metals are used. We may now briefly describe the various Processes employed in the different kinds of sculpture. For Statues, Groups, and high or low Reliefs in marble, the sculptor first " sketches " his design on a small scale in clay or wax. He next makes a model of the re- quired size, having the object to be represented before him. The clay is kept moist whilst it is being worked, and when the model is completed is allowed to harden. A cast is then taken of the model by throwing over it a mixture of liquefied plaster of Paris. When the plaster- mould so obtained is hardened, the clay inside is picked out, and an exact impression of the model remains. This mould is then brushed over with some kind of varnish and filled with fresh plaster, and as soon as it is set the mould is removed with chisels, and a complete fac simile of the model is produced. With this before him the artist begins to work in the marble. The cast and the marble are placed on two blocks, called scale-stools, exactly alike ; a vertical rod with a sliding needle attached — so adapted by a movable joint as to be set at any angle and then fastened — is then fixed to the block on which the cast stands, and the needle is adjusted until it touches a certain point of the cast. The rod is then removed to the block on which the rough marble stands, and the marble is cut away until the needle touches it as it did the model. A mark is made on the two corresponding points of the model and block. This operation, which is called pointing, is repeated until all the different surfaces of the future work from the outside of the marble are ascertained, when