According to Dawa, this stuff, though it is so light you could easily think that bucket was empty, is very expensive. It is mixed with the fortran (which has a liquid consistency---at least it did the time we were shown how to use it) to create a more viscous media to work with, allowing for creation of hollow spaces within large molds....this is all hearsay...I've never tried to use any of this...but am eager to learn!