I learned something new and very important today while working at Williams-Sonoma: Never cool a hot pan in cold water or on a cold surface.
It causes thermal shock. Because rapidly lowering the temperature of a pan like that causes it to warp. Warping makes it so that the pan won’t sit flat and can “pop” when heated back up. Your best bet is to let the pan cool naturally — such as on the stove top.
(Gosh, I wish I knew that last year! I’ve gone through three jelly roll pans and the latest one is warped!)