[c_morrison]

I am an artist working with polyester, epoxy, and urethane resins- I have chemistry knowledge, but not enough to solve my problem- what chemicals could I safely mix with these types of resins (and catalyst) to form a colored precipitate within the castings?  I have done twenty different castings, but sort of "blindly" mixing them (which I have proved very dangerous)- they are beautiful, but I am not sure if they are stable.  They have been cured for over a year.  Anyways, if anyone could help me if they have any expertice in this area or anywhere I could find info that would be great!