PLASTER encyclopedia topics

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.

The Columbia Electronic Encyclopedia Copyright © 2004.
Licensed from Columbia University Press

casting, plaster

casting, plaster: see plaster casting.

The Columbia Electronic Encyclopedia Copyright © 2004.
Licensed from Columbia University Press

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plaster of paris

Quick-setting gypsum plaster consisting of a fine white powder, calcium sulfate hemihydrate, which hardens when moistened and allowed to dry. It is made by heating gypsum to 250–360°F (120–180°C). Used since ancient times, plaster of paris is so called because of its preparation from the abundant gypsum found in Paris. It is used to make molds and casts for ceramics and sculptures, to precast and hold ornamental plasterwork on ceilings and cornices, and for orthopedic bandages (casts). In medieval and Renaissance times, gesso (plaster of paris mixed with glue) was applied to wood panels, plaster, stone, or canvas to provide the ground for tempera and oil painting.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.