A material used in architectural ornamentation, art and medicine. Made of calcium sulfate hemihydrate, it hardens and sets when moistened and dried. In architecture, it is used in interiors to construct false ceilings or ornamentations on cornices and ceilings. In art, it is frequently used to cast moulds and is sometimes used as the primary material in sculpture. It is also one of the ingredients in gesso, a popular material for decorative surface painting.