demould after a night 
when plaster is a little wet, put foam on the bottom. the foam distorted. 
wood glue with water 
make gelflex
make clay wall 
gelflex
brush wood glue(thin by water) 2 layers
brush vegetable oil to help separate
heat gelflex and make clay wall
plater dig in water for hours, then do not need brush glue and oil
I use filer to fix the plaster and filter will dissolve in water. plaster can fix plaster
if use clay(not fired) to make mould, just brush oil.
