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Can't get rid of solder line on fine jewelry

Greetings,
I am a professional jeweller and gemologist base in Zanzibar, Tanzania... I work only in platinum and palladium base 18k white gold... recently I have seen a small solder problem in two of my pieces. The point where I solder seems to show a line in the rings even after polishing and rhodium plating.. The plating is done perfectly and so is the polishing, and I have begun to suspect that the solder I have newly alloyed isn't the right mixture thus being softer than the gold and wearing off... Can you please help as I haven't had such a problem before... My usual solder is an alloy of gold , palladium and cadmium.

Anwar Elias
professional jeweller - Zanzibar, Tanzania
August 19, 2011

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Well its hard to say without seeing them but it sort of sounds like a polishing problem. The solder that you are using is probably harder or softer than your base material. If you are using buffing wheels or a magnetic centrifugal polisher the polishing erodes the softer material faster than the harder material. This will leave a very slight ridge between the hard and soft areas. Of course that ridge is merely superimposed on the surface after playing with rhodium. Also the rhodium plating slightly smooths and brightens the finish which makes the little ledge stand out even worse. The only way to get around it is with hand polishing with fine cloth like crocus.

Rod Henrickson
gunsmith - Edmonton, Alberta, Canada
August 22, 2011