often used interchangeably with gypsum
plaster) is a versatile interior building material made primarily from calcined
gypsum, sand, and water.
Composition & Chemistry The core of gypsum mortar is the
mineral Gypsum (CaSO4 .2H2O). To make mortar:
Calcination: The raw gypsum is heated to about 150°C,
removing most of its water to create Plaster of Paris (CaSO4 . 0.5H2O).
Rehydration: When you mix this powder with water and
sand, it "rehydrates," growing needle-like crystals that interlock to
form a solid, hard mass.
