HI Dave
I have tried it both ways, go get your self a piece of copper 1.5/ 2mm thick and try to bend it by heating and letting it cool does nothing for it drop it into water and see the difference, have a look on the net with people doing copper work and they tell you to heat it to red heat and drop into water, when we were doing the head gaskets if we did not get it hot enough it still retained the hardness and would not compress.
Graham Russell

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"It's better to be not informed than ill-informed"

The only thing that may be of relevance to thin gasket material is that if allowed to cool slowly, the grain size may become siginificant compared to the thickness. Thin sheet is known to have issues with forming when the grain size is large, but washers don't count as thin in these terms.

cheers
michael

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