old hands that ever wrought a siphon in lead know the melt point of lead, and how to detect it before it happens..
an IR temp reader is a handy, but costly thing.
but, temperature crayons are (not) cheap.
Mecanics use them up to 580 centigrade.
the idiocy of this is that a blackboard chalk.. a colored chalk, (the blue chalk crayon most used by old style plumbers) will turn white gray at 290 or so.. (the green and red ones, them all change to a markedly different hue around there) and is what anybody can get.
Oh, white chalk turn yellowish.
for HOTTER, you would need the mecanics temperature finder grease crayons.
JT, old type tinker.
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