Copper is awesome. It carries electricity through our world, and it makes many things blue, like octopus blood and turquoise stones. We’ve been making stuff out of copper for, oh, something like 10,000 years. Yep. Really.
No surprise that we magpie humans first used copper for jewelry (ooh, shiny, pretty!), and we are still using it, a lot of it, in making jewelry today. Even when metal isn’t copper colored, it can still be mostly copper, like brass, bronze, and nickel silver (which, confusingly, contains no silver).
Most of the time, copper is a tremendously pliant and forgiving player in the jewelry studio, but occasionally it “misbehaves” and ends up in places we don’t want it to be. Sometimes… we pull a piece of silver or brass out of the pickle, and it’s… gah! it’s PINK!! Do not despair, chemistry is the cause, and chemistry will come to the rescue!
So, the thing about copper flashing – the thin layer of copper on the surface of sterling silver or brass that pickling sometimes produces – is that it has two causes, and one solution (there’s a pun in “solution”… we’ll get to that shortly). The most common pickle is sodium bisulfate dissolved in water. After you solder something, this handy acid cleans the piece by eating the crusty flux and oxides off the surface.
Cause # 1 – Iron in the Pickle:
In the case of sterling silver, copper flashing happens when iron is introduced into the pickle pot. This causes the copper in the pickle to plate out of the solution onto whatever objects are steeping in the liquid. For this post, I wrapped the chain above in a bit of iron binding wire and a few seconds in the pickle produced this spectacular result.
CLASSIC JEWELRY MYTH: “Pickle that has been contaminated with iron/steel is ruined forever and must be thrown away.” FALSE!
FACT: This contamination is TEMPORARY. Simply remove the offending iron/steel tweezers, binding wire, etc. and the pickle will return to it’s former more benign state. The only time the pickle is ruined is if you cannot remove all the iron/steel (i.e. tiny particles of steel wool remain in the pot). Even if the pickle has eaten through the enamel on a metal pickle pot, exposing the iron/steel underneath, you can transfer the pickle to a different pot and it will be fine. You’ll need a new pot, but not new pickle solution.
Cause # 2 – Zinc in the Alloy:
Copper flashing on brass happens not because copper is plating from the pickle onto the brass, but because the pickle is revealing the copper in the alloy. Brass is actually composed mostly of copper. The other main ingredient in the mix is zinc (a grey metal…go figure). The pickle acid likes to pull the zinc off the brass surface, leaving the copper behind. Sometimes the whole piece of brass will be completely pink, sometimes there will be just some areas that are pink and other areas will still be yellow brass (like the picture above).
SOLUTION – Etch the Copper Off with SUPER PICKLE:
In a small plastic container, mix equal parts of:
- warm pickle solution (scoop a little bit out of your pickle pot*)
- hydrogen peroxide (regular ol’ 3% stuff from the drug store)
I used about 1/8 cup of each. A few tablespoons will do if that’s enough to cover your piece of metal. Don’t mix more than you need because the solution doesn’t keep. It loses its efficacy within the hour.
Use PLASTIC tongs (or wood, or copper, NO iron or steel!) to drop your metal piece into the Super Pickle.
The results can be pretty dramatic…
The pictures above and below are greenish because the pickle solution is a greenish blue. The bubbles – vigorously obscuring the view in the images above, and behaving more decorously in the images below – are indications that the Super Pickle is working, stripping the copper off the surface of the metal.
Remove your piece as soon as the copper is all gone. Rinse it well.
Once the copper is gone from the surface of your piece, you will notice that the surface is also much less shiny and smooth than it was originally. This is because the etching action of the Super Pickle has begun to bite into the metal under the copper flashing. The longer the metal sits in the Super Pickle, the more the surface is etched, hence the instruction to remove the metal as soon as the Super Pickle’s work is done.
If you want the metal to be shiny again, you’ll need to polish it.
Bonus awesomeness? After you are finished with your Super Pickle, pour it back into your pickle pot. No muss. No waste. The hydrogen peroxide breaks down very quickly into water and oxygen, so all you are putting back into your pickle pot is a bit of diluted pickle. Since water evaporates from pickle pretty quickly when it’s warm, you have to add water to the pot every now and then anyway, so the spent Super Pickle helps keep the regular pickle solution at the right strength.
May the force of Super Pickle be with you,
* For my regular pickle solution, I mix about 2oz (roughly 2 Tablespoons) of granular sodium bisulfate with about 1 quart (~1 liter) of water. Always add acid granules to water, not the other way around! This solution is not as strong as that recommended on the Sparex can, but then I’m not trying to sell you more Sparex (I don’t follow the “repeat” part of the instructions on shampoo bottles either). My solution strength works fine. I find if the solution is TOO strong, it doesn’t work as well. More is not always better. I buy my sodium bisulfate at a pool and spa store that sells it as dry acid to lower the pH of hot tubs.
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