Plaster of Paris - is also referred to as Gypsum plaster. When plaster is heated to 150c, calcium sulphate hemihyrate ( CaS04-1/2H2O) is foremed, something wihich is in essence plaster powder. A Chemical reaction occurs though when this powder is added to warm water, and a hard, solid substance is one again formed. Plaster of Paris is widely used for so many craft projects. It can be used for mold making, mask making and ceramic figurnes. Mix it with water, mold and once cured you can paint it with acrylic paint.