Just the heat of the normal curing process. One mold this has happened on is a figet spinner. I put “extra” deep pour resin in it. Normally I use 7050 clear thin-cast. Do you think it had more heat because the mold wasn’t thick? I also had this happen to a clock, so also a thin mold. And to some smaller but deep animal molds.

150 ml. This is the deep pour for tables 1 1/2 gallon. That IS the same as the smaller 3/4 gallon bottle of deep pour, isn’t it?

I have just been using alcohol up until now. I read on your site earlier this week to wash them with soapy water and treat them with the release. I hadn’t been using it because (I now know) I was using it wrong and would end up with white spots. I will definitely treat the molds with the “perfume method” from now on.