How do I easily oxidize brass?

October 3, 2008 12:16 PM

What is the best way to oxidize brass chain?

I have 100ft of shiny, raw brass chain that I want to have a uniform, oxidized/antiqued finish. What is the best way to accomplish this?

(I've successfully finished foot-long sections using vinegar fumes, but I have neither the time nor inclination to repeat that process a hundred times!)

posted by logic vs love to media & arts (5 comments total)

There are commercial products available. If you know any jewelers they might help you as they often put antique pieces on jewelry. They often use liver of sulfur, though, which does not do so well on brass, so that may be a dead end.
posted by TedW at 12:34 PM on October 3, 2008

If it has not been lacquered, it will oxidize to a dull finish fairly quickly. Most of the brass nowadays is varnished to preserve a shiny finish. You would have to remove the varnish first.
posted by francesca too at 2:01 PM on October 3, 2008

Here are some Patina Formulas for your perusal.
posted by Floydd at 2:03 PM on October 3, 2008 [1 favorite has favorites]

A suggestion from this page:
"Soak your brass part in CLOROX Toilet Bowl Cleaner. It ages the brass without giving it the overall brownish patina, but does dull the brightness and tone down the brassy color, after about three days at room temperature. Since brass is an alloy, the color change may be slower or faster depending upon the proportions of metals in the alloy."
posted by Floydd at 2:08 PM on October 3, 2008

if the brass is, indeed, not coated, you can wrap the chain tightly around a bar (or some other piece) of stainless steel (ie. greater than 12% chromium content), tight enough so that each link of the chain is in electrical contact with the steel. then dunk the whole thing into a bucket of salt water.

the resulting electrochemical reaction should fairly rapidly corrode (read: oxidize) the brass, as long as the type of steel you use is lower (more noble, less active) on the galvanic series than the type of brass you have. exhaust pipe from a car parts store would work, that should be SAE 304 grade steel which beats (near as i can tell) any type of brass. a piece of titanium or silver would work, also, or depending on the exact composition of the brass, maybe copper would work too.

what you'd be doing here is making the brass into a sacrificial anode where the brass oxidizes and essentially prevents the steel from corroding. you might want to bubble some air through the water and/or stir it well, as this will keep enough oxygen in the water so that the thin passivation layer of native chromium oxide on the surface of the steel doesn't get depleted. otherwise the reaction will run in reverse.

i have no idea how long this will take (not long, i'd think, if all you want is a patina) but if it's going too slow, you can unwrap the chain from the steel, and use some wires to connect the chain and steel to opposite terminals of a battery. it's friday night and i'm too tired to think about what the right polarity should be but it would certainly drive the reaction faster.
posted by sergeant sandwich at 8:03 PM on October 3, 2008