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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 ...
While working in Haarlem at the military hospital in 1851, Mathijsen first used plaster of Paris as a bandage. [1] Until then a Belgian method was used with starch that took up to a day to dry and harden. [1] Across the street he watched workers repairing cracks in the church with strips of jute dunked in plaster of Paris.
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 ]
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.
Gypsum mortar, also called plaster of Paris, was used in the construction of many ancient structures. It is made from gypsum, which requires a lower firing temperature. It is therefore easier to make than lime mortar and sets up much faster, which may be a reason it was used as the typical mortar in ancient, brick arch and vault construction.
Fiorelli is best known for his plaster casts (calchi), produced by a process named after him: the Fiorelli process. He realized that where a corpse or other organic material had been buried in ash, it had rotted over time, leaving a cavity. Whenever an excavator discovered such a cavity, plaster of Paris was poured in and left to harden. The ...
Before Haussmann, most buildings in Paris were made of brick or wood and covered with plaster. Haussmann required that the buildings along the new boulevards be either built or faced with cut stone, usually the local cream-colored Lutetian limestone , which gave more harmony to the appearance of the boulevards.
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 ...