On Wednesday, July 20, 2016 at 5:04:24 PM UTC-7, MOP CAP wrote:
Nobody has asked "what cast iron?"
If it's a frying pan, it's already got a heavily-oxidized surface which
is fairly impervious to ordinary stuff unless it's removed abrasively.
Clean cast iron rusts just by thinking about it.
UNIFORM 'rust' is hard to obtain by any means except heat-treating, which
usually gives a black oxide layer, not 'rust' colored.
If you only want _a_ color... try a gun blue treatment (on freshly-
cleaned and never-touched metal). If you want 'red rust' for some yard
ornament or such, you're pretty much on your own.
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