Calcium sulfate is a compound found in nature in both a hydrated form and a dry, crystalline form. It is odorless and is most often found as a white powder, but the color may be different, such as having a yellowish tinge, because of impurities. The various industrial uses of this chemical include as an ingredient in plaster of Paris and quick-setting cement, and as a pigment. The food and pharmaceutical industries use calcium sulfate as a calcium supplement.
When hydrated calcium sulfate is heated, some of its water molecules are lost, making it a hemihydrate. This type of calcium sulfate reacts differently from the hydrated and dry forms, turning into a paste-like substance that dries hard. In this application, it can be used as plaster of Paris for art projects and is also mixed with cement to create quick-drying cement.
Paints need pigments to create colors. Calcium sulfate, without impurities, is a white color that is typically mixed with paints to create white paint. This type of paint is used for art painting and both exterior and interior paints.
The paper industry often makes paper with a coating that either gives the paper extra sheen or extra durability. Calcium sulfate is used as a coating agent for papers and adds thickness and durability, making the paper harder to rip. It does not offer any extra sheen or luster to paper. It is also used a filler, so lesser amounts of other components are used to make the paper.
Fertilizers have additives that help raise or lower the acidity of the fertilizer, which makes it suitable for certain types of plants and environments. As an additive, this ingredient creates an acidic fertilizer. Some plants that do better with this type of fertilizer are azaleas and rhododendrons.
The food and pharmaceutical industries use calcium sulfate as an additive and as a supplement. Many pills that are used as calcium supplements, or foods such as cereals that are enriched with vitamins, use this as a cheaper form of calcium. This reduces the cost, making it easier to produce the product. According to the U.S. Food and Drug Administration (FDA), this is regarded as safe.
In metalworking, fluxes are substances used to reduce or eliminate impurities. They are needed, because most metals in nature have impurities that need to be removed, or the metal cannot be made properly. As a flux, calcium sulfate is used to help remove impurities to create aluminum.