I've never applied PVA mold release directly to plaster. My initial feeling is that it might be too porous. You should probably put a few layers of wax and shine it up before applying the PVA. Perhaps do a test run on a separate piece of plaster to see if that's enough to get a clean release for the glass. Good luck, and keep us posted. (and don't forget the gloves when using the acetone)

Ross

> Actually, the wax worked really well, and hatches turned out great. But It
> leaves behind that waxy built up. And when I get around to sealing with
> silicone it wont stick properly. I will try the Acetone trick, Thanks for
> the info.

> BTW Ross I was going to ask you about PVA release for my seats. When I
> finish creating the positive molds, made out of plaster. I mixed up a
> whole bunch of plaster paris and sat in it last night, Worked out quite
> well i might add. can I apply the PVA directly to the mold or do I have to
> make it shiny ( epoxy the mold?). I've never used the stuff.

> Derek