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Precious metal recovery


#1

Tip for those who want to find out how much gold is being lost from
their bench work, clothing, shoes and other means.

When I was much younger , my parents had started a jewelry factory
that only manufactured 14k and 18k Jewelry for resale in Europe… At
one point, we wanted to find out how much gold was being lost in
various areas of the shop. The first are we concentrated on was the
jewelers work benches.

To set up the test, we Weighed all gold and stones that went out for
each job and inventoried the total weight given to each jeweler. No
one knew we were running this test as gold loss can also be atributed
to small amounts of daily theft as well as general filling , sawing
and stonesetting. Benches were designated only to be used for specific
gold… in other words, we had benches set up for 14k work and 18k
work.

At the end of one week, we tallied the returns of gold dust,finished
pieces and left over sheet stock or casting sprues form each
jeweler.Polishing was also inventoried before and after so that we got
accurate loss factors for that operation and also told us exactly how
much gold of each karat was in the polishing dust… This is then
useful info when you send dust out for refining.

The result of the first week was a sizable amount of gold being lost
at the bench . For the second week, we repeated the same experiment
with no one knowing about it and had the same problem with gold loss.

We then had a meeting with the 4 jewelers and told them what we had
been doing and the resulting high gold loss… Lo and behold… The
following week, there was no loss at all !!!

We thought everything was fine until we received a report back from
our refiner in switzerland who gave us a return sheet that told us
everything in the gold dust that was recovered… This report then
told us that metals that we did not use were being introduced at some
level of the bench work.When all the refiners info was talied up, our
gold content from refining matched our in house report, however, the
total of all the metals told us that the gold refined was actually
closer to 10 k than 14 or 18k as it should be since we only made 14k
and 18k. This alerted us that now, we had some individual(s) who were
adding filings to their gold dust that was brass oriented when we
were not looking. At that time, cheap security camera’s were not
available, so over the weekend, we had a window put in that was a
oneway mirror… that week , we caught 2 jewelers filing brass rod
into the gold and checking their weights against The original amounts
on their work sheets… hence, the " no Loss" situation. Now, we all
know that there should be some minor loss in clothing and shoes so
having a no loss situation was what set us looking for answers…as
well as the refining report. We also found that the stonesetter was
actually replacing a few small diamonds in rings with synthetics…
and we thought that it was the diamond dealer who was selling us
occasionaly bad color diamonds which was not the case as we saw the
stonesetter replace the stones. These people were then replaced and
all shop employess were informed that we ran continuous testing on
all work in progress and our loss factor in gold went down
tremendously.So did the stone setting problem .

We then bought all new work aprons (white ) for the workers and
weighed each one before giving it out to the employee on a very
acurate scale. At the end of 2 weeks , we took those aprons and
weighed them… Bingo ! There was gold to be recovered in them as
well. Next, we installed a simple vacuum cleaner system close to the
exit door so that employees had to vacuum their shoes and clothing
before leaving… The result of all this was a loss factor of aprox.
2 grams out of 1000 grams used.This was probably on the floor and in
the wooden desks.

We had been using a different refiner in Thailand for recovering the
polishing sweeps and gold from the aprons… But his figures were
always about 50 % of what should have been recovered… we sent the
next batch to Switzerland and recovered 98 % … big difference but it
cost a lot to do that, so my father made a deal with the owner of the
gold refinery in switzerland and I was sent there to learn gold
refining at their factory.But that… is another story for another
time… I can say that the swiss refiner controlled all his workers
using the most up to date methods for tracking all metals refined …
and no losses were tolerated.

My suggestion for those who have bench workers is to instal a small
dust colector under each bench set up so that when you do filling or
any work that generates dust … it is automatically collected by the
dust collector… then, at the end of the day, the employee will then
remove the hose section attached to the bench and vaccum his clothing
shoes and all around the bench corners , table top and floor near his
area. This will give you maximum recovery of all metals

Hopefully this longwinded story will be helpful to those who need it.

Daniel Grandi We do casting, finishing in gold, silver,
brass/bronze and pewter for people in the trade.