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Gypsum plaster, [12] also known as plaster of Paris, [13] is a white powder consisting of calcium sulfate hemihydrate. The natural form of the compound is the mineral bassanite . [ 14 ] [ 15 ]
The word gypsum is derived from the Greek word γύψος (gypsos), "plaster". [9] Because the quarries of the Montmartre district of Paris have long furnished burnt gypsum (calcined gypsum) used for various purposes, this dehydrated gypsum became known as plaster of Paris. Upon adding water, after a few dozen minutes, plaster of Paris becomes ...
It is chiefly made of plaster of Paris (powdered gypsum), with a little cement, glycerin, and dextrin, mixed with water until it is about as thick as molasses. When staff is cast in molds, it can form any shape. To strengthen it, coarse cloth or bagging, or fibers of hemp or jute, are put into the molds before casting. It becomes hard enough in ...
With judicious heating, gypsum converts to the partially dehydrated mineral called bassanite or plaster of Paris. This material has the formula CaSO 4 ·(nH 2 O), where 0.5 ≤ n ≤ 0.8. [8] Temperatures between 100 and 150 °C (212–302 °F) are required to drive off the water within its structure.
The plaster is modified with the addition of animal glues such as isinglass or hide glue. 'Marezzo scagliola' is worked with the pigmented batches of plaster in a liquid state and relies mainly on the use of Keene's cement, a unique gypsum plaster product in which plaster of Paris was steeped in alum or borate, then burned in a kiln and ground ...
France's main Jewish students union has plastered walls around Paris with posters bearing the faces of French citizens believed to be held hostage by Hamas in their war with Israel. Very little is ...