Originally Posted by TwoCables
Heads are made out of a petroleum product, and so heat makes the heads act a little bit like shrinkwrap. As Bob Gatzen says, petroleum products shrink when heated. So, getting them warm (not hot) around the edge when they are evenly tensioned down very hard will seat the head instantly. It will not harm the head nor the shell because you're not using anywhere near enough heat to do any damage, especially if you're using the low setting on a hair dryer, or if you're using the high setting and going around the circumference of the head rather fast, like 2-3 lugs per second on a 10-lug drum. Going that fast 2-4 times around the head will be perfect and will only get the head warm, not hot and therefore it's harmless.
Besides, humidity is far more harmful to wood than heat. The air coming out of a hair dryer is only as humid as the air that it's pulling in through the intake side.
Gatzen ought to know what he's taking about. Still seems a bit unnatural, since the normal process for a drum head would be to stretch, not shrink. Could be innovation to take advantage of, though. I will try this on my next head change and see how it goes.