a I've always heard this and do believe it's founded on fact, but I have some I got from Micro Mark almost 20 years ago and I still use it successfully. It is light blue and a reddish color. The light blue part is a bit stiff but it all blends together fine and of one solid color. It cures in the same time (5 minutes) as it always has and is firm and solid. I use it for "press casting" small parts that only need the molding compound pressed over and around it. Just an FYI