I have made several resin masters from different "lead molds". Things I learned is make sure you use a waxy release agent like Smooth On's ease Release 2831, lay down a layer of clay or I use play dough to seal any gaps on the " flat" surface - keeps the resin from dribbling out all over the place and making a ton of flash. I use clamps to hold everything tight. I make heads out of resin for tuna, musky and stripers with no failures. There's other resins than the toy stuff from alumilite.