cheaper gypsum

Is Gypsum A Pop? Plaster of Paris, commonly known as POP, is basically dehydrated gypsum, or Calcium Sulphate, available in powdered form. Is pop and gypsum the same? Difference between Gypsum and Plaster of Paris (PoP) Plaster of Paris is made from Gypsum. Gypsum contains calcium sulfate dihydrate (CaSO4·2H2O) and plaster of Paris contains calcium