Annealing Aluminum with a Blowtorch

[Jughead]

I have always used soap. Simply wet a bar of soap and rub the area you wish to anneal, making sure to leave a thin layer of soap on the surface. Now heat the aluminium from the other side (not the soaped side). Once the soap layer turns black, you are done. When bending/shaping is complete, simply wash off the soapy layer.