I like the flame idea. If you use propane the temp maxes near 2000 Degrees C, but with the Mumbles fuel additive I don't think the temp will rise as much as the flame! If you're concerned about changing the steel hardness, just consider this, keeping the temp under 500 degrees F will only make the steel stronger by tempering it and getting up higher (over 1400 degrees F) will change the hardness depending on how quickly you cool it. So if you want a hook you can sharpen to cut like glass cook it till it glows and cool with cold water. It will make it brittle though so a big fish may snap your hook, as it will no longer flex. Have you tried soaking in Lye? Don't know how long it will take, I'm sure it will eat the thread, feathers, and hairs off. It won't hurt the metal, but wear gloves as it will eat you too. If you have a septic tank disregard this approach.