Copyright The Columbia University PressThe Columbia Encyclopedia, 6th ed. The Columbia University Press
plaster casting, as a sculpture process, is of three kinds. One employs a waste mold, another a piece mold (both plaster of paris), and the third a gelatin mold; all reproduce the original clay or wax model executed by the sculptor. The waste mold is chipped away (wasted) to free the hardened cast, which was poured in as liquid plaster. The gelatin mold, being pliable, may with care be sprung from the cast and removed intact and used for replicas. The piece mold also may be used again, being so divided as to be readily drawn away from the undercutting of the cast without damage to either. Plaster casts are used not only for the creation of new sculptures, but also for the numerous replicas of famous marble or stone statues. The ancient Egyptians used models of plaster taken directly from the human body. The Romans cast in plaster many thousands of copies of Greek statues. In another sense of the term, plaster casting refers to the surgical technique of encasing in a plaster-of-Paris cast any part of the body in which bones are broken so that the bones may set smoothly without interference by motion, jarring, or physical shock.