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Problems in 14k gold plating solution

Quickstart:
     Although there are some alternatives, most high purity gold plating is done from a cyanide-based bath whether alkaline, neutral, or acid. Silver plating, however, is done from highly alkaline solutions -- so apart from the usual issues involved in trying to plate alloys, silver is apparently not stable in an acid gold cyanide plating bath.
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Q. Hello,

My shop runs an acid-cyanide gold bath (cobalt hardened) that we are in the process of converting from pure gold to a 14k alloy with silver and copper, and we are experiencing a couple problems along the way.

We are using ACS grade silver potassium cyanide and copper potassium cyanide to make additions to the bath, along with the gold potassium cyanide we have been using to maintain it for years. When we first added the silver and copper salts to the bath, we got a large precipitation of a chalky white particulate, which continues to happen every time we add the silver salt specifically, while the gold and copper salts cause no visible reaction. In addition, we are trying to increase the metal concentration of the solution, which presently is less than 1 gram/Liter total of all 3 metals, however, atomic adsorption analysis has shown that only a portion of the metal added stayed in the solution, but we do not see any metallic fallout from the bath, only the chalky white precipitate mentioned above.

If anybody has any experience or advice on running a bath like this, it would be greatly appreciated!

Morgan Harding
C.E.F/Plating Specialist - Woodstock, IL
March 17. 2026

Q. Hi Ted,
The bath we are using started as a premade one from Technic, a very simple acid gold bath which we've run for several years without problems. Due to the simplicity of the bath we are trying to modify it to plate a 14k alloy.
We use only deionized water for our bath makeups and replenishments, so I feel that chloride contamination is somewhat unlikely but definitely something worth looking into.

This morning, however, after reviewing my literature from NASF on karat gold plating we took a small sample of the bath and raised the pH to 6.0 using potassium hydroxide, and a subsequent addition of silver to the sample caused no precipitation. Literature suggests that this could be due to the increased KOH preventing the formation of cyanogen polymers in the solution (or at least, that's the closest explanation I'm able to come up with at this time), if you have any further thoughts on that I would be happy to hear them.
Thank you!

Morgan Harding [returning]
C.E.F/Plating Specialist - Woodstock, IL
March 17, 2026

! I've done some further reading about copper and silver cyanide salts, and learned that the silver salt does not share the stability of the gold salt below a neutral pH range, which perfectly explains the precipitation of insoluble salts. We've raised our pH to the proper range and that appears to have solved the problem.

Morgan Harding [returning]
humbled - Woodstock, IL
March 19, 2026

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