Question

If we heat gypsum at 100 ° then POP is formed and if this POP is kept in water or in moisture it gets converted into gypsum again. So my question is why we can not make POP from gypsum again?

Answer 1

After wetting or moisturizing POP plaster of Paris gets converted into Gypsym Ca SO4.2 H2O...  It gets set in an hour or so.  When it dries we get a solid sculpture like substance now.  It gets hardened.
The original powder state of POP may not be obtained as it is.

I did not understand the question fully...  POP is made from Gypsum only.  There is little chance that we cannot make POP from it..

Answer 2

Answer:

After wetting or moisturizing POP gets converted into Gypsum (Ca SO4.2 H2O). It gets set in an hour or so.  When it dries we get a solid sculpture like substance now.  It gets hardened.

The original powder state of POP may not be obtained.