No you don't need a release agent. The clay is sulfur free oild based but for some reason it sometimes reacts with Rebound 25. I can not explain why and it is not just me. Adam has had the same issue so he recommended to me to spray it with a coat of clearcoat and that works just fine. The reaction is not always, I had it happen on a lil spot on one mold and that was it. Adam had it happen I think on his ODST Mold in a spot. Anyway this lil tip is better safe than sorry. I hate having to fix stuff that I can prevent which I do often...lol.
Ithica