What the Heck Happened? Silver Black

earthboar jewelry - Monday, March 15, 2010 - 3:01pm

Yesterday I was using silver black to deposit a patina on a cleaned copper jewelry piece. All was going fine and all the sudden the deposited patina started flaking off and the pure copper color was back. What the hay?

Thanks for any help anyone can provide.

Cathy

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Cathy, I'm not familiar with

Rich Waugh - Monday, March 15, 2010 - 5:15pm

Cathy,

I'm not familiar with "silver black" by that name - I suppose it is a proprietary name for an oxidizing patina. That said, the generic chemical for oxidizing silver is liver of sulfur, aka sulfurated potash, aka potassium sulfate. It darkens silver by acting on the copper in the sterling alloy, but the copper is only 7.5% of the alloy so the solution needs to be fairly strong to have the desired effect. When you use that same solution on pure copper it is far too strong and then the copper sulfate scale that is formed flakes off. You need to dilute the solution before using it on pure copper. I'd suggest starting out by trying about a 4:1 dilution in water, and then adjust accordingly.

Rich

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Aha! That sounds about like

earthboar jewelry - Monday, March 15, 2010 - 7:19pm

Aha! That sounds about like it. Silver black is hydrochloric acid. I prefer liver of sulfur as it is much prettier. I won't buy this product again. Anyhow, your explanation fits with the actions of my process.

Thanks Rich, for the help.

Cathy

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Aha! That sounds about like

earthboar jewelry - Monday, March 15, 2010 - 7:19pm

Thanks Rich, for the help.

Cathy

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patination

visitor - Monday, March 15, 2010 - 9:42pm

Hi,
In my experience(40 years), whichever chemical you use, if the solution is too strong, and/or the metal is not clean, it will flake off.
Cindy
www.cynthiaeid.com

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Thanks Cindy. I'm guessing

earthboar jewelry - Sunday, March 28, 2010 - 8:39pm

Thanks Cindy. I'm guessing the solution was too strong. Chemistry is interesting! Cathy

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Black copper

Pete Crowbaby - Wednesday, December 28, 2011 - 4:10am

hi cathy, i have used simple electrolsis to make a black coating on copper with a electrolyte of salt water and a small battery, by making the copper + and tin (lead free solder)-. its experimental. Pete

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