I have just made a scuttle panel for my Excelsior from some old aluminium sheet of unknown hardness. A post will follow when I find out how to include pictures in a post. In the process I needed to do some metal bashing and annealed the sheet before starting. Many moons ago, an old toolmaker gave me this tip to gauge the correct temperature.
You firstly smear the area to be annealed with soap, using a dry bar of soap rubbed over the area. Then play a blowlamp over the area until the soap just turns black. Wash off soap and you are ready to bash.