Right, you wouldn't want to try to heat chemistry from room temp to working temp using the pig pads, but they're very effective at maintaining the temperature of tempering baths. I heat distilled water in the microwave for the E6 chems and tap water for the tempering baths, and maintain the temps of both with the pad. I imagine it would work as well for keeping lith printing trays at or close to the proper temp.
K
"I've seen those, and they are good for small adjustments, say if you're at 60 degree room temperature and want to heat it to 70. But I also hear that they are not good if you have to heat up chemistry a lot. So it works for some situations, and not for others."