Why is the temperature maintained around 393 K during the preparation of plaster of paris ?

Explanation

Plaster of Paris is prepared by heating gypsum to 393 K
`2Ca underset("Gypsum")(SO_(4) . 2H_(2))O overset(393 K)(to) 2 underset("Plaster of Paris")(CaSO_(4).1//2 H_(2))O + 3 H_(2)O`
If the temperature is raised above 393 K , plaster of paris is further dehydrated to form anhydrous calcium sulphate which is also called dead burnt plaster since it loses the properties of setting with water
`2underset("Plaster of Paris") (CaSO_(4).1//2 H_(2)) O overset( gt 393 K)(to) underset("Dead burnt plaster")(2CaSO_(4)) + H_(2)O`