If the epoxy is cold before mixing it will set up slower, I just use my heat gun to wam the bottle a little until it flows good, then I mix the two and it will set in normal times and dry, tack free in double the stated set-up time. When ever you use an evaporative thinner, it will slow dry times because you loose too much heat while the stuff evaporates. Heating epoxy after it's mixed doesn't really speed up curing for some strange reason.