I meant to share this trick earlier because I thought it was so cool when Joan showed it to me during Mayhem. Sadly I forgot about it until I offered to bring my resin copy of Vixen to the show this weekend.
The idea is to create a mock-up of the inner mold pieces in plasteline. By sculpting the piece as it would look if you used a particular set of mold lines, it’s possible to see if the piece will pull properly. This is even more effective if the resin and clay are placed in the freezer so the clay hardens a bit, since that mimics the rigid quality of the plaster mold piece.
And if you forget that you placed the horse in the freezer back in, oh, say… MAY… well, then you can test whether or not it hurts resin or plasteline to stay frozen for long periods. (Apparently it doesn’t.)
Edit: Joan tells me that mocking up the pieces this way was an idea that came from Barry at Laf’n Bear. Barry was also the person who first used Legos to box molds, so he’s really an innovative guy!