In the past few decades calcium sulfate based building products have become materials of choice for various interior construction purposes, The basis of gypsum technology is the ability of gypsum to transform into various calcium sulfates (hemihydrale, anhydrite) when being heated. When hemihydrate or anhydrite is mixed with water calcium sulfale dihydrate is formed again due to re-hydralion. During re-hydration of hemihydrate, the following exothermic reaction occurs: