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Sizing rhodium plated white gold rings.
Ed. note; This is an interesting thread, and only one of many. Before you get too confused, you might want to start with our FAQ on Rhodium Plating and White Gold to get an overall understanding :-)
+++I am a repair goldsmith doing trade work for retail jewelers. White gold is popular these days and most white gold rings are rhodium 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. Jewelers do not want to pay to strip the old plating and replate the entire piece.
William Russell Powellgoldsmith - Saskatoon, Saskatchewan, Canada
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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 (returning)goldsmith - Saskatoon, Saskatchewan, Canada
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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.
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.
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Neil Bell |
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January 6, 2010
Regarding your query regarding the repairing or resizing of a ring, you have to take special care about the finishing of the work done. You have to finish up the resizing very well without any pits and you have to polish all the ring shank very well. To do this operation, You must use a very fine abrasive paper to smooth out the rhodium plating existing before the using of the torch for resizing. Then, a very good polish first with tripoli and then with a fine polishing agent, like Magic Blue Polish using a soft cotton polishing mop. Now comes the crucial point: there should be a divine cleaning of the job done otherwise the rhodium plating would become dull or stained. The item to be plated must be electrocleaned well and then soaked in distilled water to clear off any impurities. After all this, place the ring in a Rhodium Bath and give it a 15 to 20 second bath, please be sure that the bath is warm at least 100 degrees F. Take it off the Rhodium and soak it again in distilled water and dry with a soft tissue. Now the ring repaired should look as new.
Joseph Tanti- Valletta, Malta
November 10, 2010
When I got my rings sized about 11 months ago, 5 months later they turned black and you could see were they had done the sizing so I took it back and it has done it again? Why does this happen it has only been 6 months again. The rings are White Gold 18ct. I have other White gold and this has not happened with them and they have been sized.
Rebecca Kirkworried mum - Auckland, New Zealand