Hi aspen
To produce a bronze finish on yellow brass :mix equal parts of nitric acid , sulphuric acid and water.THE NITRIC ACID AND WATER MUST BE MIXED FIRST AND THE SULPHURIC ACID ADDED VERY SLOWLY.

Dip the brass part in BOILING water for a moment, then into the acid , then quickly back into the boiling water, then rinse thoroughly in clean water. Dry the part in sawdust.

A WORD OF CAUTION DO THIS OUTSIDE, HAVE A BUCKET OF LIME OR SODA WATER, TO USE TO WASH DOWN ANY ACCIDENTAL ACID SPLASHES. ALSO WEAR EYE PROTECTION AND RUBBER GLOVES. THIS IS A VERY HOT ACID MIXTURE ALSO KEEP THE KIDS AWAY WHILE YOU ARE WORKING WITH THIS PROJECT.

Try a brass piece to see if this is the finish you want.

Good luck and PLEASE be careful

bill

aspen
One more thing when mixing acid ALWAYS add the acid to the water slowly ( stronger (acid) is always added to the weaker (water)).
bill

This post will likely earn me a reputation as the "resident safety grump," but it could save your vision, and your skin, so I will proceed. Concentrated acids are best handled by those with recent experience, along with formal training, in an academic or industrial environment where there exists "institutional memory." Concentrated acids are unforgiving. If you work outdoors, wearing a long apron of acid resistant material, with a full length face mask, 16" high rubber boots, and long rubber gloves, you will likely avoid injury. I would use a plastic bucket, cut down so that it is wider than high, for holding the acid mixture. The same bucket could be used for neutralizing the acid solution when the procedure is completed. Neutralizing concentrated acids should be done slowly and with caution. There will be heat generated, & this must be allowed to dissipate.

Will the above acid dip work if the yellow brass has a coating of protective lacquer?

Would it be best first to treat the piece with naval jelly or paint remover to get rid of the coating?

Once such a coating is removed, the brass should slowly tarnich in air to a bronzy look.

Hi aspen;
A very big A-MEN to what Eric posted. I guess that my past years of working around acids makes me complacent as to the safety.

Yes spam all finish, oil, and grease must be romoved before acid treatment.Yes the brass will turn brown in time.

aspin: There is a very good hardware catalog " LEE Valley". They have all kinds of brass and black iron hardware. There web site is "www.leevalley.com ". It may be cheaper to buy new hardware than to buy the material for the acid bath. I don't know if you have access to a supplier for the acid and what the cost would run. If you got all new hardware it would match in color.

It runs in my mind, that at one time we used Sodium Hypochlorite (bleach) to darken brass, but I am not sure. Old age you know.

take care bill