I’m hoping someone really knowledgeable will weigh in on this, but
for now here’s my suggestion.
Is the brown a real smutty sludgey layer? If it is, it’s that same
coat I get when etching brass in Ferric Chloride. You need a
chemical method of removal, rather than mechanical, to save your
texture. Use a good copper cleaner, like Penny Brite, or a homemade
vinegar /salt / flour solution (like Alma suggested here on Orchid,
the other day when I posted about running out of Penny Brite.). It
will take the brown right off. Then RINSE immediately and rub down
with dish soap: for some reason a new layer of brown (and some new,
prettier, but still unwanted colors) re-forms if you don’t wash it
well. I usually finish it off with a soak in water with a scoop of
baking soda dissolved in it. I was told this would neutralize any
ferric chloride lingering in the crevices. I soak overnight or a at
least a few hours.
(If anyone knows more about when and how long this should be done,
let me know too. I’m just doing what I was told.)
There’s 2 possibilities for the red stains you’re talking about.
One: if you’re soldering YELLOW brass, some of the copper in the
alloy migrates and makes those marks, which can look a lot like
little squiggles or lines, and seem to be fractionally below the
level of the surrounding brass. You cannot sand those out: they seem
to go deep inside. I have never been able to get rid of them, just
try to hide them with the patina. Use red brass whenever possible:
it doesn’t do that. Sometimes you’re stuck if using tubing, rod, or
machined shapes; they seem to be made only in yellow brass, which,
yellow brass multiple times or with high heat makes it worse.
TWO : If the red is more of a rosy flush, then what you have is
copper plating on top of the brass. If it’s on a large flat area,
sanding it off is still faster. Otherwise, use the Hydogen Peroxide
Pickle recipe in the Archives. It’s also listed on the Reactive
Metals website. Do this only after all soldering is complete. It is
stinky. It will also etch the surface lightly and leave it looking a
little grainy, or like you could see the crystal structure of the
brass. Which you then have to… sand off. But at least heavy
sanding will not be necessary. The red staining is worse if you
pickle the piece; you can wash it instead. But it will turn red from
the heat alone, too.
If you are going to have a patina in the low recessed etched areas,
then don’t worry about the copper stain in there. Most patinas will
work much better on the copper plate anyway: so use it to your
advantage. After the patina it won’t even look like copper in the
recesses. Just polish the high parts to look like the original brass
color.
Good luck…
Lin
It