Exactly what you do not want when making a mold. We were trying to figure out how to make some new plugs from one of our successful molds, and figured we would do it like we may end up doing the car- Foam that is sanded and finished with epoxy. That didn't end up happening. This picture is what happens when expanding foam cures in a mold with no release agent- It had been sanded, and we didn't realize it when we went to put in the foam. Oops.