Heat treating is sometimes referred to as a science and sometimes a fine art. In the case of blades, I tend to think it's more art. Very basically, when you heat steel up to its critical temperature, which is different for each steel, and then cool it quickly, you harden it. Its hardness is measured on the Rockwell scale, that's what the RC means. In the 60s is chisel-hard, for reference. So when you hear a reference to heating, it's actually the hardening that people are talking about. If someone says that a company doesn't heat their blades well, they're saying that the companies blades are either too hard, or too soft. Again, I'm oversimplifying, but it's a pretty complicated subject. Heat treating is done in a oven, kiln, or a forge(the fire pit you referred to).
Hope this helps.
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Oz
"I didn't think it was THAT sharp!"