Plaster

A mixture of lime, sand and water. When used for sculpture, plaster can be used to make mould-making and casts or initial small-scale or full-scale models. Plaster of Paris (also called gesso) is made by heating gypsum and then crushing it to a fine powder, which when mixed with water, sets to a hard brittle solid. It is relatively cheap, fine-textured, easily mixed and quick-setting. Ideal mould-making material, it flows easily into gaps and during the process of drying expands slightly, forcing the plaster into the finer details of the mould.