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Q&As since 1989


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Ancient Japanese gold, silver and mercury plating on bronze

Hello all. Aside from building many types of models for the Goverment and Aerospace industry we do a fair amount of antique restorations. A common procedure years ago especially with the Japanese was to mix mercury and gold or silver powder to a paste, brush it on most commonly bronze brass or silver bake it in a oven or kiln and the mercury would evaparate from the powdered metal and adhere to the bronze. We have tried mixing powdered gold and silver with mercury but it doesn't seem to mix. We need to utilize this process to do certain restorations. Could there be a additional ingredient to help it mix and what kind of heat do you think would work. We use a well ventilated oven for our experiments. Any help would be appreciated, regards Bill

Bill Di Noia
many finishes are used in our facility - Hicksville, New York
February 4, 2008

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Are you sure there is not a blanket prohibition of this process? Letter 13037 says it is illegal but offers no substantiation. Deliberately evaporating mercury to the atmosphere may be a problem though. So much so that, in some threads a year back or so, we were unable to find a single place in the whole USA offering to fix gold jewelry that has suffered mercury damage -- despite there apparently being millions of such pieces. letter 13044 includes an entry saying that the dangers are overstated. Sorry that I see no reference in our archives on how to actually achieve the decorative effect, but hopefully someone will chime in.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 6, 2008

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Bill
Take a look at 47587
If you have an old (Edo) piece please don't destroy its value just to make it look pretty.
There is a simple trick to amalgamating gold for fire gilding but Ted is quite right, if not illegal where you are, it will be heavily controlled. Your oven may be ventilated, but where does the vent go?

Geoff Smith
Hampshire, England
February 12, 2008

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Oppi Untracht's book on Jewelry Concepts and Technology [affil link on Amazon] may be good starting point (very good description of process).Process is very dangerous !Hope it helps and good luck!

Somewhat less dangerous variant of that process is so called combined gilding: dissolve 60 parts of potassium cyanide and 10 parts gold cyanide in 1000 parts water, then add 10 parts mercury cyanide, use coal anode, 3,5-5 v, after gilding mercury must be evaporated by heat (cca 400 C), you need powerfull ventilation system! Maybe it is illegal! According to Diebeners Werkstattrezepte fuer Gold und Silberschmiede,Stuttgart 1982 (Gold and Silversmith Handbook) Hope it helps and good luck!

Goran Budija
- Cerovski vrh Croatia
February 13, 2008