Fiberglass and polyester resins will only fully cure if NOT exposed to open air. ... Not sure if this is the same as aluminite as I have yet to work with it.
Polyester and vinylester resins
will fully cure when exposed to open air -- it just takes longer. Fiberglass workers take advantage of that property by doing thick layups in multiple layers. They wait until the previous layer cures (but the surface is still tacky) before applying the next one. That way, each layer bonds chemically with the previous one. For the last layer, they'll either add wax to the resin, or spray PVA on top to form an air barrier. That lets the top cure without being sticky. The polymer should be hard enough to work in about a day, but really continues curing for at least a week.
I demold my polyester resin blanks when they are still warm and tacky. Then I wrap each casting in wax paper until it cools. The surface is typically hard by then. If not, I just put it someplace warm for an hour or two.
Alumilite cures much quicker than PR, with a dry (not tacky) surface. It is still flexible at that point, however, and continues to harden over time. According to Alumilite Corp, multiple pours of Alumilite will chemically bond, even though the surface is hard to the touch.
I hope that helps,
Eric
