A containing negative mould, used in sculpture for casting metals. It consists of either earth clay and sand or plaster of Paris mixed with clay, pulverized plaster, asbestos fibres and glue size when mixed up for the lost-wax process. Also sometimes called casing.<br><br>A thick jacket of refractory material built around a wax model which forms the mold in lost-wax casting. It can be made of plaster or clay mixed with grog, applied in layers, with the finest and softest layers painted or gently worked over the wax model, and the outer layers reinforced with wire.Also see mortar and pestle.