Cast


Gypsum is a common mineral made up of hydrated calcium sulfate (CaSO4•2H2O), its characteristic color is white, with an earthy or compact appearance and it is usually soft enough to be scratched with a fingernail. Crystallized gypsum has white or colorless crystals, solid or laminated. Gypsum is a type of sedimentary rock formed by the precipitation of calcium sulfate in seawater. It originates in volcanic areas due to the action of sulfuric acid on minerals with calcium content; it is also found in many clays as a product of the reaction of limestone with sulfuric acid. This mineral can be found in all parts of the world; some of the best deposits are in France, Switzerland, the United States and Mexico.

Calcium sulfate dihydrate is known as “natural plaster”, “gypsum stone” or “gypsum”. This compound has been used since ancient times; the Egyptians used it for mortar and stucco in the pyramids of Giza, the temples of Karnak and the tomb of Tutankhamun. Other uses are as a fertilizer in dry and alkaline soils, as a bed in the polishing of glass plates and as a base in pigments for paints; It is also used in Portland cement.

Industrially, dihydrated gypsum is heated, losing part of the water and turning into a semi-hydrated fine powder, known as gypsum or plaster of Paris or «baked plaster«. This, when mixed with water, makes a paste that hardens forming molds. It mainly has medical use since it serves as a bandage on a part of the body to keep it immobilized. It can also be used as a construction material, to make molds in the manufacture of sculptures and statues, ceramics, dental plaques, among others.