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Depletion gilding on sterling silver not working?

I’m trying to depletion gild a cast piece of sterling silver for enameling and I’m running into issues. As I understand it, depletion gilding involves heating up the sterling silver until some oxidation appears, quenching the piece in pickle, rinsing in water, drying it off, and then repeating this six or seven-ish times. I learned that the oxidation should be less and less each time I heat it, as the copper is removed and a coat of fine silver covers the piece. (If this is inaccurate, please correct me!)

I tried this on a piece of sterling silver and it worked just fine. However, when I ordered some sterling silver cast rings and tried to heat them up, the oxides would appear briefly, seem to disappear back into the metal almost immediately, and then reappear in the same amount every time I fired it again. The metal gets a bit more white and a tiny bit more matte after a while, but the oxidation keeps coming back—I’ve tried heating and quenching it more than fifteen times in a row. I tried another cast ring from a different company and had the same issue.

Am I doing it wrong? Does it have something to do with working with a cast piece? (I’m not sure whether the first piece I tried, the one that worked, was cast or not.) Or—and this is my working theory—is it possible that these sterling silver alloys are similar to Argentium (although it’s not described as such) and so include germanium or another anti-oxidation agent, and that that’s why depletion gilding isn’t working? (And if I am working with an alloy that contains germanium or something similar, am I pretty much fighting a losing battle when it comes to enameling it?) Or is it something else altogether?

Any help would be appreciated!

Interesting! I also wonder if it was plated with something, but then my understanding of such plating is that it burns off really easily so it seems like that should be long gone if it was ever there.

Unfortunately the only part of this I can address is to say that both Argentium and plain old sterling even without the depletion gilding absolutely can be enameled! Somewhere back in the archives there’s a thread on enameling Argentium, and there was one artist in particular who did it often and very well. With the plain sterling you may run into issues with firescale and making sure you use eutectic solder for any joints is critical, but it can be done. Good luck on the rest of your mystery, I hope you can make it work!

I wonder if maybe your cast alloys have some zinc in them?

A small technical point:
‘Depletion gilding’ is bringing out the gold in a gold alloy (by depleting the non-gold elements from the surface). When the process is done on a silver alloy, it’s called ‘blanching’. :wink:

Janet in Jerusalem

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