"slight frosting"

[LugerVern]

Ever clean a rusty bore using chemicals?
It will be free of rust but look just like frost on a window pane in the winter.
I think that is where it came from originally but, I see it used to describe exterior finishes also, it comes down to "rust" or pitting.


It might also describe the feel of frost as you run your fingers over it, but I never thought of it that way.

just a WAG

Vern