When I'm at work and have time to kill - which is most of my shift - and I'm not on the boards here or window-shopping (drooling, really) on the magic/card sites, I'm playing solitaire or practicing magic. Usually solitaire. I work at a rather elaborate desk, constructed out of a heavy, composite-stone material. It tends to be cool to the touch, even when it's warm inside.
Often, something comes up and I have to leave my desk for a few moments. Usually when I return, I look at the cards and they're bowed up and away from the table at the sides. Doesn't matter what cards, most decks do this. If there's a stack of cards, then the top one or two cards will bow; three in some cases. Aristocrats, Arcanes, Sentinels, even the venerated Tally Ho is no match for the cool stone desk.
However, when I leave a stack of Streamlines on the desk, they remain flatter than an ironing board, no matter how long they're left.
Go figure.