![]() ![]() Because plaster of pairs reverts to gypsum with the addition of water and its subsequent setting, plaster of Paris expands on setting. Mixed with water the plaster is spread and finished to a thickness of about 2 to 3 mm and sets in about 1 to 2 hours. This plaster is generally used as a finishing touch to cement and sand plaster undercoat. Besides, the POP plasters have no appreciable chemical action on paint and do not cause alkali attack as in case of lime or cement plasters. POP plaster is comparatively easy to spread and level. On drying out POP forms a sufficiently dense surface to resist normal knocks. The advantage of POP plaster is that it expands very slightly on setting and is not, therefore, likely to cause cracking of surfaces as happens in the case of cement plaster. Following are the Different Uses of Plaster of Paris This will hold the damaged part until it is recovered. ![]() A bandage along with plaster is wrapped around the injured part. It is used to create safety soft bandages. et al’ (Publish in – US National Library of Medicine National Institute of Health), Plaster of Paris is widely used as bone graft substitute and to fill up bones defects. Plaster of Paris is being used from the ancient times in the following fields till date, It was used to create some of the most important artworks of the Renaissance period, including Michelangelo’s Sistine Chapel ceiling, which was painted on a thin layer of wet Plaster of Paris. POP is manufactured as a dry powder and is mixed with water to make a paste when used. Also Read: Gypsum Board: All You Need to Know! Types of Gypsum Board | All you Need to Know When water is added to plaster of paris, it returns to its original hard, rocklike form gypsum containing calcium sulphate and two molecules of water. (Chemical name of POP is calcium Sulphate where Ca is the symbol for calcium and SO 4 is the symbol for sulphate, so CaSO 4 stands for calcium sulphate). The chemical notation of Plaster of Paris is CaSO 4– ½ H 2O. According to ‘ Walter Scarborough et al’ (Author of Building Construction – Principles, Materials, System), when POP is heated to remove 75% of its water, the resulting product is calcium sulphate hemihydrate (Hemi means “half”), referred to as plaster of Paris.
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