Plaster of Paris ($\text{POP}$) is commercially produced by heating:

Plaster of Paris (${\text{CaSO}}_4\cdot \frac{1}{2}{\text{H}}_2\text{O}$) is prepared by heating Gypsum (${\text{CaSO}}_4\cdot 2{\text{H}}_2\text{O}$) to a controlled temperature of approximately $373\text{K}$ ($100^{\circ }\text{C}$).
$${\text{CaSO}}_4\cdot 2{\text{H}}_2\text{O}\stackrel{\Delta }{\to }{\text{CaSO}}_4\cdot \frac{1}{2}{\text{H}}_2\text{O}+1\frac{1}{2}{\text{H}}_2\text{O}$$