Hoping someone can help with this, I used some por-a-mold thixatropic from Dick Blick to mold a helmet, and had a couple of issues with it. Firstly, it took ages to cure in a couple of spots on the inside of the mold, it was tacky for a while. Secondly, now that I've started pulling casts from it, they have what I would estimate to be around a 4% shrinkage on them.
Is this normal for this silicone, or did I get a bad batch? As it is I'm considering just tossing the mold and starting again with something else anyway, any recommendations?