Folks, I use Rio Grande’s white bronze in my bronze casting and I find if I pickle it that it leaves a copper coating on everything. Sometimes this is good, particularly if I want a copper surface color, but most times I would like to remove it.
Any ideas? How can I fix my casting, rather than sanding the piece to get the copper off? Thanks for your advice and help.
William
Hi William,
A 50/50 ratio of warm/hot clean pickle and hydrogen peroxide should remove the copper. It works quickly when hot, but don’t bring the solution to a boil. Keep a close eye for if you keep your work in the solution too long it’ll begin to etch and not in any good or predictable way. If it doesn’t seem to be working you can add a little more hydrogen peroxide. The solution has no shelf life. It can be poured back into your pickle pot when done.
Hope this helps,
Pam
Do you use the commonly available 3% hydrogen peroxide or a higher volume cosmetics grade clear developer?
Common 3% hydrogen peroxide from the grocery or pharmacy.
I had the same issue and got this recipe from someone else and it works really really well.
And to add to the above comments. Often the cause of pickle solution copper platting is putting iron or steel into your pickle. Be sure the tongs or tweezers you put into your pickle are non ferrous
Although iron/steel will cause your used pickle to become a plating solution, copper alloys such as brass and bronze will almost always develop a mottled copper layer. It can happen when the metal is being heated or put into the pickle, no iron or steel required.
Those more knowledgeable than I could explain why this happens. Is it similar to depletion guilding except it’s raising the copper to the surface?
Thank you, Pam, for your answer. I tried it and the peroxide mix does clean the metal in an interesting way. I work with different bronze and brass, and yes, I often see a copper layer even without iron contamination. I’m sure this will help me remove the copper and improve my work.
Adding peroxide is definitely one of the best solutions. For other bronzes and brasses I have found that if the pickle/peroxide doesn’t get it all, that scrubbing with Bar Keepers friend or Penny Brite (which contains citric acid and is a decent pickle) often helps to get the rest. Also, a run through the tumbler with a semi-rough cutting media can finish it off. I have found that an extra long time in a hot citric acid/water or vinegar/saltwater pickle has helped with the stubborn copper oxidation when working with Nickel Silver.
I have tried any number of things and to see what works best, not everything works great every time in my opinion. It usually depends on the alloy.