are you refering to polystyrene. yes they use foamed polystyrene pellets (styrofoam is the trademarked name) and introduce a large amount of steam to their surface. within a mold they will expand when introduced to steam and expand to the point of saturation filling the mold completely. the surface is just as those foam products that are in items that are boxed new from the store, not that good as compared to a foam cut with hot wire cutter. it will work just won't be pretty. becareful though acetone, crazy glue, and some paints will melt it like there's no tomorrow.
