Doctor Evil wrote:
"GB" wrote...
"Chris Bacon" wrote...
(annealing copper)
That's interesting. Never tried this before. What do you mean by redness?
Copper tube is naturally an orange colour, so it's not particularly
obvious (to me).

You heat the pipe with a powerfukl blowtorch (best use two) until "cherry
red" and then quench it in water. It has to be cooled immediately.

Hi Doctor Evil, if you quench the tube straight away, it makes it easier
to clean off the black oxide, however the annealing effect will happen
anyway if you just let the tube cool. This is much slower, though.
Quenching of steel, for instance, is a different matter.