when i took off my head instead of a gasket there was a copper plate gasket thing not a gasket and i was wondering what this is and what it does and if it is reusable with a new top end
that would be hardening it, you dont want that. The heating up part is correct tho, you just let it cool down in the air (no assistance). This will make it soft again and will conform to the mating surfaces when torqued down.