Plaster of Paris is a type of plaster made from GYPSUM, a soft mineral composed of calcium sulfate dihydrate. It is also known as gesso, which is a white paint mixture used to coat surfaces before painting. GYPSUM is the main ingredient in Plaster of Paris and is heated to 150-160 degrees Celsius to form a fine powder. When mixed with water, it forms a paste that can be molded into shapes when it hardens. Gesso is a mixture of Plaster of Paris and glue, which is used to create a smooth surface for painting.