Back to Ganoksin | FAQ | Contact

Recycling soldered silver


#1

G’day. Even the best of jewellers make scrap; I make heaps! But
with an oxygen torch, a flat crucible, and a small rod or ingot
mould, one can easily recycle it. But it isn’t a good thing to
recycle sterling which has been soldered; it contains zinc and
doesn’t make good wire or sheet when subsequently rolled or
drawn. I save all my spoilt, soldered projects (Sometimes
there’s far too many!) and finally melt and cast them into a
small thin ingot. I suspend this with a bit of silver wire in a
glass vessel containing cyanide solution, and pass a 6 volt
current through it via a bit of stainless steel as a positive
electrode. (anode) The ingot gets eaten away and deposits on the
stainless as a fine, grey granular deposit, easily scraped off. I
dry this off on blotting paper, put it in a crucible, sprinkle
powdered flux over it, and melt it with a slightly reducing
flame. I cast this as a rod or flat ingot, and roll or draw it as
needful. It is actually fine silver. To prove or disprove that
all the copper had gone, I dissolved a little bit in conc nitric
acid, then added ammonia until the precipitate redissolved and
there was a slight excess of ammonia. If there had been any
copper in the recycled silver, the liquid would have shown a blue
tint. It didn’t. (other chemists in Orchid will doubtless verify
that this is correct) I couldn’t test for zinc, but can only
assume that if there’s no copper, then the zinc has gone too.
{Not Necessarily correct, however!) Anyway, it makes excellent
fine wire, whereas recycled sterling wire containing solder gets
nasty little ‘jags’ in it due to the zinc boiling and making tiny
bubbles. OK: so no sensible jeweller making items for sale for a
living would bother with this- heshe could earn far more in the
time than heshe could save. But it is a viable proposition for
amateurs.

    /\      John Burgess
   / /
  / /      Johnb@ts.co.nz    
 / /__|\
(_______) And don't do anything I wouldn't.