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Ok, to answer a few of your questions
let's follow a few pieces in finishing. This may be of more interest
to students than customers, and of course, fellow Ganoskin members!
These are three 4x6 inch casting trees
of fish, lighthouses, sailboats and propellers. Each tree is
330-360 grams of silver. Rather than quench them in cold water
to break away the investment quickly, I let them cool overnight
and break away the investment by hand. It is my belief that this
results in a denser crystallized piece of jewelry. As the crystals
are allowed to cool, they shrink back into position tightly packed
rather than being shocked into cooling oversized and not allowed
to settle. I believe this is one of the contributing factors
to brittle jewelry. Sharp students or experienced casters are
already smiling as they know I mixed up the weights on the tree
on the left and the middle. One has a button too large and the
one in the middle is too small. I'm not as sharp at midnight
as I am at 7AM with half a pot of coffee!
Here the trees have been further cleaned
in a hot ultra-sonic bath. It gets most of the investment off,
but not all. It could be cleaned further with a high pressure
jet. At this stage, I prefer the magnetic disc finisher to get
all the nooks and crannies.
Our test subjects. These have been tooth
brush cleaned of all eye visible investment. The scratch over
the side fin and some surface imperfections, will almost disappear.
5.9gms
This is 200gms of stainless steel pins.
A fraction of a millimeter thick. They can stick into you like
a needle. A magnetic disc is under the bowl and spins. This in
turn causes the pins to swirl in the water striking the jewelry.
This makes tiny pock marks that pack in and smooth the finish
without removing metal. I prefer to finish as much as possible
by burnishing rather than removing metal. Hand finishing a piece
from start to finish can remove 10-20% of the metal. Burnishing
removes 1-2% but takes a lot longer.
Loaded with pins, jewelry, water and
burnishing compound. I also like to add a little baking soda
as it keeps the pins clean.
These guys are swimming upstream and
being bombarded with stainless steel pins.
 
After one hour of magnetic centrifugal
finishing at 1,800rpms
1-4mm ceramic media
 
After two hours of ceramic centrifugal
wet finishing at 360rpms. You can see we are getting more shiny
without losing detail.
1-3mm porcelain
 
After two hours of porcelain wet centrifugal
finishing at 300rpms even more shiny and the little scratch behind
the eye over the fin is still visible. I did that while breaking
away the investment with an awl in the beginning.
This is after 48 hours of DRY tumbling
in fine walnut shells! Much jewelry is sold and considered finished
at this stage.
So far, for the two pieces we have only
lost 1/10th of one gram in metal weight. They have been work
hardened to resist scratching on the surface and hardened within.
They have withstood 53 hours of tumbling and wet centrifugal
finishing. Any weak pieces have showed up and parts broken off.
Now, for the hand finishing which involves
various grades of impregnated polishing discs, rubber wheels,
rouge compound buff and a final Picasso blue wax. It was here
I had to remove the scratch as the tumbling does not really remove
so much as displace. The only way to remove the scratch was by
removing metal. I could have tried a carbide burnisher that would
have moved the edges in, but it shows up more under high polish.
 
It is too polished now to see any detail
as it acts like a mirror. On the left you can see my reflection
with the camera and the leaves of trees in the background. On
the right are several trees behind me and the clouds! I am obviously
outside to take this under natural daylight on a cloudy day.
We lost 7/10ths of a gram in the final
15 minutes of hand finishing! So we started out with 5.9gms of
Argentium 935 silver and ended with 5.1gms. 8/10ths of a gram
disappeared into microscopic silver dust! Another reason USA
labor requires a strong ventilation system and wearing a respirator.
Do note that with the tumbling the fins had no loss of detail
and very little rounding of the edges.
If it were only these two pieces for
a customer, I could have done them from start to finish in less
than an hour or two. Maybe lost another gram in metal. The three
trees had over 200 pieces and most can be finished now in a few
minutes. And 200 grams of metal gets passed along to the customer
rather than in my filters, buffs and lungs. If you are just learning,
after a few hours of hand buffing with your Dremel or Foredom
without a mask, your can feel it in your lungs. It can take several
days to clear. Get the best filter mask you can find. It is your
most important piece of equipment.
This was a 4x6 14kt gold tree, #146 rich
gold from Stuller. 420gms yielding 204gms of clipped jewelry
and 216gms of sprues and button. After polishing maybe 180gms
of finished jewelry. I hope! Gold comes out in the most fantastic
soft natural gold color imaginable. Almost ready to wear. Most
people want it brightly polished!
A tour of the lost
wax casting process |
