its a plastic. its just mixed with air -- foam -- to give it a better structure. take a lighter to some, at a distance mind you, go slow, and it'll melt down

its a plastic. its just mixed with air -- foam -- to give it a better structure. take a lighter to some, at a distance mind you, go slow, and it'll melt down into a plastic-y resin. used to do that all the time to make terrain for tabletop gaming.