I assume that is what he was talking about.
Sorry to veer off topic, but if you are making molds for masks, and you want to avoid the toxic funk, I suggest you try making your molds out of hydrocal FGR and a fiberglass matting that is designed to break down its bonds in gypsum such as Aqua-Veil. You can make molds that are a half to 3/4 inch thick and they hold up pretty well. I wouldn't use it for large production runs, but it is what I use to make silicone masks for my haunt. Bob Gorman the guy who makes the costumes for Gwar told me about it. That is how he makes all the slip cast molds for the Gwar costumes.