Despite its label's claim of Hard Setting Formula,, this epoxy never DID completely harden for me. I thoroughly mixed up about 2 ounces of it and poured it in a layer about 1/4 thick onto a slick, smooth polyethylene jar lid in order to test its qualities before using it on one of my high-power rocket projects. (For the test, I purposely did NOT want the epoxy to adhere to the surface.) The shot glass I prepared it in DID become scalding hot, though, and the epoxy began to gel in only about 10 minutes--far sooner than the 60 minutes it claims. After a full day, I peeled the disc of epoxy from the slippery plastic and found I could actually bend fully-cured Speed Epoxy II in half, like taffy. Maybe there's some good use for an epoxy that cures so limply, but I can't think of it. I will go back to JB Weld slow cure. IT cures to as hard as a glass marble, and it sticks like a pit bull's teeth to an ankle, on just about anything that's porous or that you can scratch up prior to application.