Plaster

Description

1) Shortened name for Plaster of Paris which is composed of calcium sulfate hemihydrate. It is also called calcined gypsum.

2) A powder, that forms a pasty mixture with water and dries to a hard impenetrable solid. Clays plasters were used in Egypt since at least 2000 BCE for coating walls and ceilings. Decorative wall paintings with plaster supports were made in Crete as early the 15th century BCE. Plaster is made using several formulations. Most plasters contains calcined Gypsum or Lime as a binder. Many use Sand, Hair, hairhair, or Straw as extenders. Some may contain small amounts of salts (Potassium sulfate) as accelerants. Organic materials (Blood, Glue, Casein) and weak acids (Citric acid, Boric acid) can act as retardants. Plaster is still used as a finish material in wall and ceiling construction. Some examples of plaster types are:

- Lime plaster - contains calcium oxide; used for frescos and wall decoration

- Gypsum plaster - contains calcined and ground gypsum; See also Gypsum cement.

- Plaster of Paris - calcined gypsum; used for molds, sculpture, casts

- Stucco - contains gypsum and sand or chalk; used for walls, ceilings, decoration

Synonyms and Related Terms

plâtre (Fr.); estuque (Port.);

Sources Checked for Data in Record

• R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966

• G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 386

• Ralph Mayer, A Dictionary of Art Terms and Techniques, Harper and Row Publishers, New York, 1969 (also 1945 printing)

• Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996

• Encyclopedia Britannica, http://www.britannica.com Comment: "plaster" Encyclopædia Britannica [Accessed October 31, 2001].

• Art and Architecture Thesaurus Online, http://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000