Plaster of Paris is stored in moisture-proof containers, because the presence of moisture can cause slow setting of plaster of Paris by bringing about its hydration, which will make it useless after some time. When the dry plaster powder is mixed with water, it rehydrates over time into gypsum.
Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO 4 and related hydrates. In the form of γ- anhydrite (the anhydrous form), it is used as a desiccant. One particular hydrate is better known as plaster of Paris, and another occurs naturally as the mineral gypsum.
- 7778-18-9, (hemihydrate): 10034-76-1, (dihydrate): 10101-41-4
- 1,460 °C (2,660 °F; 1,730 K) (anhydrous)
- 0.26 g/100ml at 25 °C (dihydrate)
Etymology and history. The word gypsum is derived from the Greek word γύψος (gypsos), "plaster". 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.
Feb 27, 2020 · plaster of Paris ( uncountable ) A hemihydrate of calcium sulfate, made by calcining gypsum, that hardens when moistened and allowed to dry; used to make casts, molds and sculpture.
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Plaster of paris, quick-setting gypsum plaster consisting of a fine white powder, which hardens when moistened and allowed to dry. Given that it does not generally shrink or crack when dry, it is an excellent medium for casting molds. Learn more about how plaster of paris is prepared, its uses, and history.
Mar 02, 2019 · For thousands of years, plaster of Paris has been a popular material for artists, decorators and even medical professionals. Named for the gypsum reserves found near Paris in the 17th century, this cheap, easy-to-use medium can be found in everything from leg casts to ancient statues.
Feb 28, 2021 · To make plaster of paris with glue instead of flour, heat 1 cup (240 mL) of water to 100°F (38°C). In a mixing bowl, combine the water with 2 cups (470 mL) of white school glue. The resulting plaster will have a soupy consistency. Use this plaster within 15 minutes and let it set 3 days to completely dry.
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Plaster of Paris is manufactured by heating gypsum at 423K or 150o C/300o F. CaSO4·2H2O + heat → CaSO4·0.5H2O + 1.5H2O (discharged as steam) On heating gypsum at 423 K, it loses water molecules and becomes calcium sulfate hemihydrate. This product is known as the plaster of Paris.
Aug 10, 2019 · The origins of plaster of Paris can be traced to Montmartre in North Paris where it was extensively mined from. It is also known as POP. As described by ‘S.C. Rangwala’ (Author of Engineering Materials book), Plaster of Paris is prepared by heating gypsum crystals at the temperature of 160–170 °C (248–356 °F).
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