Calcined gypsum is produced when dihydrate gypsum is fired at the temperature of 800-1100 °C. At this time, a little calcium sulphate is decomposed to generate new phase CaO, which gives calcined gypsum certain hydrating ability. The condensation speed of calcined gypsum is slow. The amount of water demanded in standard consistency is about 25%-30% of its own weight. It has qualified wearing resistance after hardening and can be used for indoor terraces, so it is also called floor gypsum. In addition, there are also medical-used and artificial gypsums. They are widely used in medical treatment (such as setting bones), arts and crafts (gypsum moulds and models etc.) and so on.