Rounding dies for 8" air tank

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I've seen a video from a local shop north of Waterloo, Iowa that was doing copper based sheets. They had flames directed at the piece to do this process. I assume this was to make the shaping better (soften the material) as well as anneal work hardened material during the spinning.
So I thought back to a video I saw earlier this year from a Youtube channel I watch, the guy adds humor to his metal working;

This is part 1, and clearly he has not read any manuals on this. There is a part 2 as well;