For Brass, I've tried liver of Sulfur, and several Selenium salt or
acid compounds from hobby stores, which give varying shades of very
non-uniform brown or mottled black finish.

Gun blueing is a stronger Selenium compound, and unless wiped and
removed very quickly, produces a nasty black smut. Start over.

Some practice will yield not a bad finish on small parts, but on
a sheet like that?

I suspect that a combo of heat, perhaps molten blueing salts,
and/or fumes of something might just work ok on a very
diligently cleaned surface, but no guarantees. I've seen some
really nice looking Chelsea clock dials (blackened brass), but
can't come close to replicating it myself.. / mark


Roger Jensen wrote:

I need to turn a bit of copper foil black. I have less than 1 square foot to
treat. Paint isn't an option. Anyone know of a good way to do this? Google
search wasn't real productive. I am wondering if any of the Birchwood gun
stuff would work?? I tried using a sulphur paste, it tarnished it, but not
black...

Thanks,

rog