What is (and function of) this brittle thin material, if it's broken it'be a bit shiny white flakes, which encloses the wound nichrome wires in a heat element?
Not really, it's really chromium oxide - " When nichrome is heated to high temperatures it develops an outer layer of chromium oxide, unlike other metals which may begin to oxidise when heated in air. This means it is mostly impervious to oxygen and the heating element is therefore protected from oxidation."That's "Oxidized" Nichrome caused by Oxygen in the Air.
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