Gypsum Plaster

Gypsum plaster is a product of the rock gypsum. It is milled and cooked. Most gypsum plaster products have a life ranging from twenty minutes to two and a half hours. It is possible to use accelerators and retardants with the gypsum, to get a desired setting time. The most common finish used with gypsum plaster from the turn of the century to the mid 60's is a sand finish achieved by screening the pit sand before mixing the plaster for consistency. Just about every public building in the united states, built before 1970 has this type of finish.