On a twilight zone note, Ty, I have gone to a completely bazaar release agent for my molds - saran wrap!  Sure I get wrinkles, but the insurance of a totally trouble free release is worth the small effort to fill those places and sand them smooth.  Try it, you'll like it.

Thanks Ty, I could not remember the name of the stuff.   We used it years ago to make fiber glass fuselage molds.   I tried some stuff that was supposed to be for molding stuff from the local craft store.  What a waste of money.   Now I need to find Hydrocal locally.    By the way we would seal the surface with Johnson's Paste Wax of all things.   

First time I worked for Boeing, I worked in the Mockup fiberglass shop. They asked for volunteers, because some people have a problem with glass itching (but maybe it was an epoxy allergy?). I didn't really like rivets that much. We used Hydrocal for the basic "plaster" mold, but then usually skimmed it with plaster of paris (POP), which gives a finer surface finish. The Hydrocal usually had some "horse hair" (shredded wood fiber or something) added to strengthen it. I think the Hydrocal shrank less and was supposed to be stronger than POP.

We always used "high temperature epoxy resin". I thought it would be cheaper to use low temp. epoxy resin, and was all set to earn myself a nice bonus by suggesting that as a cost cutting measure. Turned out the high temp stuff was cheaper. We also used Johnson's paste floor wax (usually), perhaps with a spray coat of teflon or silicone or somethin' like that for a parting agent. This was 1965. Looooonnnngggg time ago.... Steve