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[Issue #7]


                H i g h l i g h t s

Jewelry Manufacturing Methods and Techniques

        December 1, 1997 Issue #7

Highlights Editor:
~ Dr. E Aspler <@Service> newsgroup modarator:
~ Peter Rowe

Introducing Highlights
^^^^^^^^^^^^^^^^^^^^^^^^^^^^From: Peter Rowe

Attached are a number of recent messages sent to the usenet
newsgroup, This group is a moderated
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Peter Rowe


“Tumbling Questions”
~ (Exquzmwa)
~ (Ron Charlotte)

“Mass finishing”
~ (Byzantia)
~ (JoyReside)
~ “R. Arney”
~ (Charlie Fred)
~ Jan McClellan

“Channel-set size limit?”
~ (Dave Thompson)

“Gold Tarnishing”
~ (LeeCo11)
~ “Susan and Lane”
~ John Christensen
~ Brett Gober

“Restoring a Pearl’s Finish”
~ “DeMarco”

// – H-E-L-P --//

Orchid Highlights

Tumbling Questions
From: (Exquzmwa)

I just wanted to send a quick message with the solution that I
came up with in case it will help someone else with a similar

At any rate, I still don’t have the formula for calculating the
correct tumbling speed. If anyone knows what it is I’d sure
appreciate it. That’d be faster than trial and error in the
future :wink:

For the tumbling grit, I mixed in chunks of concrete leftover from
some work I did this summer. The concrete worked perfect. It
removed the sharp edges from the red granite, but didn’t remove
the “rough” look the rocks had. This made them safe for my fish,
and yet with the rough look they still have a more natual look
than river rocks would have in emulating the lake I created my
tank to replicate. Curtis

From: (Ron Charlotte)

I’m not clear as to what formula you want… If you mean the
relationship between motor speed and pully speed, it’s:

(motor pully diameter / arbor pully diameter) x motor speed =
arbor rpm.

I’m not sure what, if any, specific speed is desired in a
tumbler, I know that its a slow one. I hope that this is of some
use. Ron Charlotte – Gainesville, FL

Mass finishing
From: (Byzantia)

  I am totally new to mass finishing.>snip<  I have ordered
the tumbler, steel media, and burnishing liquid.>snip< I am
working with sterling raw castings and maybe some gold. Do I
need a final buff? 

Uh oh, I think what you bought IS the final step. Going from raw
castings to high polish requires some intermediate action. I use
plastic media impregnated with abrasives in a mini-sonic tumbler.
Rio Grande’s grey pyramids (for hard metals or fast cutting)
first, to round the square edges of fabricated sterling (4 hours
or so). Then I patina and use a less abrasive plastic media to
knock the dark off of the high spots (overnight). Then into a
rolling tumbler with stainless shot and a little Dawn dishwashing
liquid (1 hr or more) to bring up the shine. Dana Carlson

From: (JoyReside)

If you are doingraw castings, you might want to prerun your
pieces in a tumbling media like Rio’s aqua pyrimids with a
prefinish deburring liquid. If you go straight to the steel
media, you might polish a shine but unless your castings are
absolutly perfect, all you will do is shine an imperfect casting.
A deburring compound will remove rough edges if run for a couple
of hours. Watch your pieces very carefully if you have detail, the
media will remove detail if left in to long. Good luck. Joy

From: “R. Arney”

Alright Mike. I’ve given those I know have al ot more expertise in
this matter a chance to respond, but perhaps they are out to
lunch. Though I suspect they wait with gritted teeth and baited
breath to learn just what type of tumbler and burnishing liquid
you have ordered. If you have gone with a conventional rotary
tumbler with a rubber boot, you could be in deep doo doo, for
during the tumbling process the sulpher (whatcha- ma-call its) can
be released from the rubber and oxidize your work and bathe you in
disapointment. There are ways around this, but darned if I
remember the prescription. Maybe my inept response will drag out
a better from those in the know. Anyway, after my first worst
experience I went with a 4# vibrosonic with a plastic barrel.

One thing I will tell you, and in no uncertain terms, encourage
you to do: If you did indeed order the “steel” shot, as opposed to
the “stainless steel” shot, The instant you finish a run, separate
the work from the shot, set the work aside. It is done. Attend to
your shot. Dunp it into a large sieve. Flush it with lots of hot
running water. Shake off the excess hot water. Dump the shot on
the thickest, dry, Terry Cloth Statler Hilton towel you can find.
Spread out the shot on the towel. Take another towel and dry, dry,
dry. When it is dry, put it on another dry towel. Spread it out
again and dry it with a hair dryer. Throughout this process roll
the shot around with the hand not holding the hair dryer until
everything is hot and dry. Then put the shot in a container larger
enough to comfortably hold it and toss in a couple of ‘silica
jell’ packets. Sporting goods stores sometimes sell them, for
bowling ball bags or shoes. Sometimes you can get the from
pharmicists. But in any case, do Not allow any chance of a single
speck of rust to form on even one piece of shot. It can ruin your
whole day dude. Keep it clean. Keep it covered. Keep it dry. Ron

From: (Charlie Fred)

Ron - I don’t know about your experience in rubber barrels, but so
far I have seen no ill effects from this. My buddy & I run steel
shot in a six sided rubber lined barrel. The barrel runs at a
fairly fast speed, so it only takes about 1 to 2 hours to bright
burnish silver. Perhaps the short exposure to the rubber prevents
any sulphur tarnish. We use a soap powder (sorry, I don’t know
exactly what it is).

As far as taking care of the steel shot is concerned, you are
right about the careful washing after each use. But you are taking
a lot of extra care in drying the shot. Secret is to NOT dry it -
put it in a wide mouth plastic bottle and cover it with
antifreeze. That prevents rust. Charlie

From: Jan McClellan

I missed the original post, but I have been tumbling with a
small black rubber tumber and stainless steel shot for 2 or 3
years and haven’t had any trouble. I fill the tumber about 2/3
full with water, shot, jewelry and a detergent mix that looks like
corn meal, and tumble overnight. everything comes out nice and
shiny. I hand prepolish the jewelry (both silver and gold) so
that all the scratches are out and its pretty near finished.
Usually I don’t have to polish on the wheel at all (unless I mess
up when setting the stone.) Is the secret in the detergent mix? I
hope not because my store where I got it went out of business and
I’m about out. Jan McClellan

Channel-set size limit?
From: (Dave Thompson)

I have a quick question for the goldsmiths on this list: how
small (in diameter) can stones be when channel set and still
look OK? I guess an alternative way of asking this question is:
what size stones are normally used for channel-setting? For
example, if the ridge of metal holding the stones in needs to be
0.5mm wide on each side, then you would not be able to see 1mm
stones, and even 2mm rounds would end up looking like 1x2mm
rectangles. Please include an email to me in response, I do not
always get a chance to read the newsgroup every day. Thanks, Dave.

Gold Tarnishing
From: (LeeCo11)

Hoping someone out there might be able to help me. I have a
caster who is using a greenish colored yellow gold. The castings
have a tendancy to weigh more than the calculated weight (from the
wax weight) but most annoying is that the gold is turning color.
Its embarrassing when customers complain and the tarnish is not
just where the piece touches the skin but even on top well away
from the skin. There is no discoloration on the wearers skin. It
even happens on pieces in the showcase. Basically, my question is
What would be in the alloy to make it turn and weigh more. Being
a greenish-yellow it has a high silver content and fine silver
shouldn’t tarnish. The caster buys the alloy prepared and mixes
it with the gold himself. Any help would be appreciated. Thanks
in advance Lee

From: “Susan and Lane”

Darn good question! I’ve always found greens to be very stable,
easy to work and relatively crack-free. Have you had one assayed
for content of materials besides gold and silver? Perhaps he got a
bad batch of alloy? Maybe he calculated wrong, though I doubt that
would make your metal turn color…Has he mixed the batch
thoroughly? (I had that problem a few weeks ago myself—a chunk
of undissolved 24k in the middle of a piece of 18k wire—very
embarassing) Investigate. It has to be solveable. lane

From: John Christensen

Lee, As to the weight issue, I am not sure, unless his
calculations are off in mixing the alloy. My thoughts would be
that he is using more gold than alloy for the proper mix there.
Have you tested it with an accurate gold tester?

The greenish, high silver alloys, will tarnish more because of the
silver. I HAVE seen the black oxidation on fine silver too, even
in the showcase. Again, test the metal, but I would recommend the
reddish yellow rather than a bright yellow. I use the reddish
yellow from Stuller Settings (g.7, reddish-yellow). It isn’t
really what you would cal red, but it has a higher copper content
than the popular greenish mix, resists scratching (and tarnishing)
a lot more, and is much more rigid. I have also found that when
sizing, a high temp welding solder will still be a little chip in
your piece when the shank is melting on some of the high silver

E! me if I can be of more help, John


Hello! I’d bet your friend is casting too hot. I would bet he is
boiling off the gold during melt. Test a piece for content. Use a
scratch test and acid. AND… test the gold grain BEFORE
casting… could be the refiner is hanging it on ya! Casting is a
science! I’ve been doing it 25 years or over…many wild things
go on that amatures can never imagine! Good Luck!

From: Brett Gober

Calculating finished weight from wax weight seldom gives you an
exact weight. If you know the exact S.G. of the wax and the alloy
then you can come close, but the density of the casting will
affect the weight. For fun you could check the S.G. of the casting
and compare that to the S.G. of the alloy and determine the
relative density of the casting. I would look closely at every
step in processing after casting. If you have any porosity at all
(even though you can’t see it, it’s there), then you can get
chemicals absorbed in the metal that will leach out over time.
Pickle, polishing compounds, cleaners, and even rust in your
steamer could be the culprit. What does the discoloration look
like? Are there any enclosed areas on the pieces where chemicals
could hide? What cleaner do you use?

It’s possible that if the caster alloys at the time of casting
that he is not getting a good mix of alloy and gold. If he is
torch melting then he is likely getting a good mix, if he uses a
machine like a Memco, Neutec, etc where the melt is enclosed in a
chamber then it is harder to stir it.

Scientifically speaking, gold boils at 2807C, silver boils at
2212C, and copper boils at 2567C. So even if you could produce
2807C of heat the Ag and Cu would be long gone (along with the
crucible). Brett

Restoring a Pearl’s Finish
From: “DeMarco”

I’m new to this group, so I hope my question is relevant and
hasn’t been asked a zillion times. I have a cultured pearl ring I
am quite fond of. It is one pearl flanked on each side by a tiny
diamond and set in 10K gold. The finish of the pearl has worn off
in places and looks dull. Is there anything I can do to restore
the luster? Is there a finish I could apply myself, or is this
something a jeweler should do?


End of Highlights Digest

// – H-E-L-P – //