I think they're using something other than a polymer to seal this since flask temperatures for casting are between 850ºF and 1200ºF. I've been looking online at other types of seals and there are some made from ceramic paper like this
http://www.gasketsinc.com/product/g83-ceramic-paper-2300degf1260degc/1809I was just hoping somebody might know the exact material used for these jewelry vacuum casters. It looks like red rings, but that doesn't say much besides color.
I did however find some plans for making a vulcanizer and it uses red silicone to insulate the coils from the wooden blocks used to build the press. I just don't know if red silicone is the way to go.
