I had burn-through and notable discoloration when learning to anneal aluminum with soot method. If I focused heat on the soot and tried to “make” it burn off, bad things happened.
Slowing to to make sure the entire area/panel was fully heat soaked before trying to burn off the soot made it work much better. After the panel was complete hot, the soot burned off easily and quickly under the flame.
An easy way to tell what I was doing was wrong or right was that an inadequately heated panel was cool enough to handle almost immediately after I did it. But Without quenching with water or compressed air to cool it, an adequately heated panel was HOT!!! when I finished burning off the soot. Way too hot to handle, even with gloves.
Fwiw- I learned it was just caramelizing sugar with a torch when doing crème brûlée. You heat the entire area of sugar before heating any specific portion to the level of melt & caramelization. Then you can quickly easily melt/collapse the sugar to the desire color with only a minor additional amount of focused flame. It kind of collapses all by itself (just like the soot will on aluminum) If you rush it and try to force the sugar to caramelize by focusing heat, all you’ll do is scorch the sugar and ruin the product. Not cool…
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