Letter 22709

Sizing rhodium plated white gold rings.[Canada] 

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I am a repair goldsmith doing trade work for retail jewellers. White gold is popular these days and most white gold rings are rhodiun plated to disguise the yellowish tinge caused by using alloys with a high copper content. My problem is how to deal with rhodium plated white gold rings when I size them. Plating is removed or damaged by soldering and finishing operations, and any material I add is not plated. The issue is how to make the area worked on look like the rest of the ring. I have a pen plater but it doesn't seem to match the original plating in thickness or color (I don't underplate with nickel). There is often a "tide line" where the original plating meets the exposed white gold and the margins of this plating are pitted because it does not polish evenly. Jewellers do not want to pay to strip the old plating and replate the entire piece.

William Russell Powell
R Powell Goldsmith Ltd. - Saskatoon, Saskatchewan, Canada

I earlier today e-mailed you a question about sizing rhodium plated white gold rings and mentioned that a lot of white gold has a yellow tinge because of copper in the alloy. Many manufacturers add copper to nickel based alloy because such alloy is finicky and has an undesirable casting failure rate and often results in a hard brittle metal. It's cheaper to cast yellowish white gold and plate it than to invest in additional casting controls and price casts with an allowance for higher failure rates. I'm not sure whether this information is needed but it answers the question, "Why would anyone add copper to white gold?"

William Russell Powell
R Powell Goldsmith Ltd. - Saskatoon, Saskatchewan, Canada

You are right, you should not use a nickel underplate for rhodium plating over white gold. You are also right that a pen plater is not the right tool for this job. It is better to immerse the entire ring in a rhodium plating bath. It is possible to get great results without removing all the rhodium but it takes some careful polishing and experience. I will be happy to send you an article (which I wrote) on this subject, published last month in AJM magazine, if you contact me directly.

Neil Bell
Red Sky Plating - Albuquerque, NM, USA

Any white gold alloy of 14K is 58.5% gold and gold is a yellow metal so no matter what other metal is in the alloy it will never be as white as platinum let alone rhodium. Some people are quite content with this slightly yellow color and if these people are your customers so much the better. The reason for copper in most alloys of white gold, be it sheet stock, wire, or castings, is to improve malleability. This attribute reduces the chance of the prongs holding stones cracking or ring shanks breaking.

Neil Bell
Red Sky Plating - Albuquerque, NM, USA

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