Gypsum plaster

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A type of plaster composed of Calcium sulfate, hemihydrate. Gypsum plaster has been used since antiquity. It is prepared by heating gypsum (calcium sulfate dihydrate) to partially remove the chemically bound water, thus producing calcium sulfate hemihydrate. When gypsum plaster is mixed with water, it converts to the hydrated calcium sulfate which rapidly sets to an impenetrable solid. It generates heat with setting and may expand slightly. Gypsum plaster is commonly called plaster of Paris. It is used for molds, sculptures and castings. See Plaster of Paris.

Synonyms and Related Terms

plaster; plaster of Paris; gypsum cement; calcium sulfate hemihydrate; plâtre de gypse (Fr.)

Additional Information

E.Sayre, "Deterioration and Restoration of Plaster, Concrete and Mortar" in Preservation and Conservation: Principles and Practice, S.Timmons (ed.), Preservation Press, Washington DC, 1976.

Sources Checked for Data in Record

  • Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996
  • Website address 1 Comment: National Park Service Briefs at

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