I’ve been building a brass box that has an etched pattern on the
surface. Both the etching (with Ferric Chloride) and soldering ends
up producing both brown and red stains on the brass. Both I have
trouble getting off. In the past I’ve just sanded it off. But since
this surface is etched I don’t want to lose or soften my surface
I’m hoping someone can tell me what the red and brown stains are and
the best way to remove them or prevent them.