Hot enough to hurt. not enough to cause any kind of lasting damage. there's a range where the worst that comes of it is a few days of irritation more akin to a rug burn.
Glad to hear it. My head is usually filled with much worse (or better, depending on how you look at it) thoughts more often than not. For instance, I could heat up the pliers' jaws before crushing them down on her clit or maybe I'd use them as an electrode for some e-stim...