Casting is one of the more complicated techniques used in sculpturing. First the artist builds an armature - which is a framework of skeleton used to support a sculpture. They then add clay to it to create the form. Afterwards, they add a thick layer of wax to the armature. Clay, sand, and ground-up pieces of old molds cover the wax surface which becomes the mold. Once cooled and hard, small holes are drilled to the bottom which is put into an oven so the wax may melt through the holes, leaving a hollow space. Once cooled, molten metal (usually the alloy, bronze) is poured in, cooled, and removed. This method is typically used in order to make exact copies of it.