For those of you heating your epoxy, be very careful you don't heat it up too much. The curing process of epoxy is exothermal, meaning it generates heat all by itself. We generally do not notice it because we typically only mix up small batches. We also spread it out soon after the epoxy is mixed, so the heat has plenty of surface area to dissipate.

However, I had once mixed up epoxy in a Kodak film canister 1/2 full, let it sit a few minutes while I prepare the balsa airframe, and to my surprise, saw smoke starting to come out of the film canister. I quickly held my breath and hauled the smoking epoxy outside the house. In less than 5 minutes, I watched the epoxy melt the canister into a puddle of goo.

Once cured, epoxy is fairly harmless, but the fumes from curing epoxy is hazardous. The smoke from burning epoxy, such as what I saw, is extremely toxic. I've since quit using film canisters. I now use these little clear plastic bowls from fruit jelly snacks. These are bowl shaped and so offer the epoxy much great surface area to dissipate heat. Heating the already spread out epoxy with a heat gun is okay, but if it is my lungs and those of my family, I wouldn't take the chance of heating epoxy in microwave, based on my experience.

Use the right tool for the job. If you're laminating with fiberglass, use finishing epoxy. Whatever you do, watch the temp on that epoxy cup!