Mark Bittman is here to help with any chocolate tempering you may have to do over the holidays . . .
I had no idea temperature was that critical in melting chocolate: First, bring it to 115 F, then seed it down to 91 F. At 88 F, it's too cool and needs to be heated again.
What surprises me is the tiny tolerance of the temperature measurements that is implied by this procedure. If 91 F is correct and 88 F is too cool, the tolerance must be in the vicinity of +/- 1 F or better. In other words, 91 F means 91.0 F! I have no hope of reading that on my conventional analog thermometer, and I'm a little skeptical that even the digital thermometers made for the kitchen are that good. (I would have guessed the temperature gradient in the double boiler would be at least a few degrees.) No wonder I've had so much trouble in the past.