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Avoiding scratches on silver jewellery?


#1

Dear Colleagues,

How to avoid scratches on silver jewellery? Silver jewellery is
produced using lost wax casting process. Alloys used for making are
Legor AG115M.

Thanking all,


#2
Alloys used for making are Legor AG115M. 

Pardon my ignorance, but what is that? I thought most trace elements
used for silver are either copper or a combination of copper and
germanium. That being said, if you’re creating a sterling silver
(.925) with an alloy to help harden the silver, then after casting,
the only thing that might protect the surface from scratches would be
to work harden it. Tumbling is an excellent way to burnish and work
harden after casting. The longer you tumble, the deeper into the
surface the hardening will move. Though I believe there is some
limit, I just don’t know what that is.

Dependent upon your tumbling medium, you could also lose fine
details during the tumbling process. Start with plastic or rice, then
move to ceramic, then lastly to steel shot. I’d tumble for about 4
hours in each medium, checking after every couple of hours. And no
steel shot on pieces with high, sharp detail. You may need more
tumbling time but you don’t want to totally destroy the detail of
your cast. Better to take your time. You can always tumble some more
but once a piece is ruined, it’s ruined.

Just passing on what I’ve gleaned from the internet, my experience
and others. I’m no expert and someone else may have a different
opinion.

Michele


#3

Dear Michele,

I thank you for your response.

AG115M is the alloy from legor which is mixed with silver to give
sterling silver. The sterling silver is cast & the jobs are then
processed using centrifugal disc finishers. The process involved is
wet grinding using cermamic cones & pyramids. corn cobs, & walnut
shell susequently. The problem with this is the prong get damaged.
We have now started using age hardening process for hardening the
pieces for avoiding the scratches. We are also planning to coat it
with polymer based liquid to avoid the tarnish & scratches.

Warm regards
Umesh.
The higher time consumption in production is a concern.


#4
AG115M is the alloy from legor which is mixed with silver to give
sterling silver. The sterling silver is cast & the jobs are then
processed using centrifugal disc finishers. The process involved
is wet grinding using cermamic cones & pyramids. corn cobs, &
walnut shell susequently. The problem with this is the prong get
damaged. We have now started using age hardening process for
hardening the pieces for avoiding the scratches. We are also
planning to coat it with polymer based liquid to avoid the tarnish
& scratches. 

Umesh - I would offer the following comments from experience -

The centrifugal disc finishers are really tough on silver. If you
have small easily bendable parts such as prongs, the force of the
disc finishers will distort them when used in batch. They are also
hard on fabricated work with fine silver bezels.

These are the ways that I would suggest around the problem - if you
must use disc finishers for silver, you need to fixture your pieces
so they don’t impinge on each other or the sides of the container. Or
you can run very small batches to avoid impingement. An easier answer
would be to use a large vibratory tumbler. The vibratory tumblers are
gentle on sterling, and I’ve never seen them damage a prong. For cast
pieces, I’d use two step process - medium and then fine abrasive.
While I know the vibratory tumblers take longer - in the range of 4
hours each cycle, you can put an enormous amount of work in a large
vibratory tumbler. Disc finishers require much smaller batches and
when you figure the unloading and cleaning time for small batches in
the disc finisher, the time shouldn’t be such a concern. You also
avoid the ongoing maintenance of disc finishing - all the cleaning
to avoid getting bits of media stuck under the spinning disc.

I don’t have a problem with steel in a rotary tumbler damaging
parts. Or in a properly loaded vibratory tumbler either.

As to hardening the silver to avoid damage - a research project that
I worked on with Gary Dawson and others for the Santa Fe Symposium a
couple of years back showed only minimal surface depth hardening. Not
enough to help prongs. If you are using one of the new-tech
sterlings, it is possible to increase hardness well beyond regular
cast material, but not enough to help prongs in a disc finisher. I
would be interested in your experience in age hardening - are you
using heat or what?

An alternate finishing method for you might be to try the new dry
medias from Diamond Pacific. My experience is that they finish
beautifully in a Vibra-sonic machine and not in other devices. The
run times are significant - measured in days. Their dry media with
50,000 diamond does work well for cleaning everything in a retail
environment - jewelry set with everything - opals, amber, pearls -
but run singly in a machine for 20 minutes - to remove light tarnish
and clean. Again, impingement is a problem - thus the advice to run
one at a time at take-in. This could be a quick finish for problem
pieces in a production environment.

Judy Hoch


#5

Once again pardon my ignorance… But what is legor? I don’t know
that word.

Regardless, if you’ve got prongs that are losing their shape or
becoming damaged, you could try protecting them with some E600. I’ve
done that on small pieces that are sharp or easily breakable that I
don’t want the media to knock down during tumbling. I tried rubber
cement to add a protective coat but it comes off too easily. The E600
sticks until I’m ready to take it off and it forms a sort of bubble
around the sections I want protected. After tumbling, those areas are
hand polished with my flexshaft or just by hand.

As always, care is needed and some things just can’t be rushed.

Michele


#6

Hi Michele, To answer your question the LegorGroup is an Italian
company with branches around the world. We have 3 divisions, Alloys,
Plating, and Tools and Equipment. The USA branch is in NYC where I
work in Sales. Our website is http://www.ganoksin.com/gnkurl/ep7z8h

We have developed some new nanoceramic coatings which you can find on
our website and are being sold by ourselves and Rio Grande.I hope
that helps, and feel free to contact me for any other info.

Cliff Durlacher
Legor Sales


#7
But what is legor? I don't know that word. 

A company name. It should have been capitalized. Legor

Al Balmer
Pine City, NY