plaster of Paris

Any of a group of gypsum cements, essentially hemihydrated calcium sulfate, CaSO₄· ¹/₂ H₂O, a white powder that forms a paste when it is mixed with water and then hardens into a solid, used in making casts, molds, and sculpture.

[Middle English, after Paris²France.]

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

plaster of Paris

1. a white powder that sets to a hard solid when mixed with water, used for making sculptures and casts, as an additive for lime plasters, and for making casts for setting broken limbs. It is usually the hemihydrate of calcium sulphate, 2CaSO4.H2O

2. the hard plaster produced when this powder is mixed with water: a fully hydrated form of calcium sulphate

Sometimes shortened to: plaster

[C15: from Medieval Latin plastrum parisiense, originally made from the gypsum of Paris]

Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014

plas′ter of Par′is

(or par′is),

calcined gypsum in white, powdery form, used as a base for gypsum plasters, as an additive of lime plasters, and as a material for fine and ornamental casts.

[1375–1425; so called because prepared from the gypsum of Paris, France]

plas·ter of Paris

(plăs′tər)

A form of calcium phosphate derived from the mineral gypsum. It is mixed with water to make casts and molds.

The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

plaster of Paris

- So called because it is prepared from the gypsum of Paris, France.

plaster of Paris

n → gesso