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Very thin casting


#1

I’ve been asked to make a mold, and reproduce by casting, a charm
made of 16ga sterling wire, hammered flat.

Measured at various places around the piece, it averages about 0.6mm
thick by 1.1mm wide. I managed to make a silicone rubber mold of it
and I can get waxes from it. But I have to shoot the wax at 20lbs
pressure with the mold quite warm in order to get it to fill.

Is this thing too thin to cast in sterling?

Kathy Johnson
Feathered Gems Jewelry


#2

just cast at a higher temp…I cast filigree with wires in it about
0.5x1 mm and a frame in 18 guage. I do vacuum casting, and have to
compensate more with temp than with centrifugal. I cast at a
kiln/mold temp of 1150 deg. F, and my silver a little hotter too. you
may not need to compensate that much if it’s a solid piece as opposed
to wires, however.

btw. be careful not to put too much pressure on the rubber mold when
you fill it…just keep even pressure. If you put too much pressure
on it, it is harder to get a proper fill.

Jeanne

PS. I just thought I’d show you how fine you can cast. This is a new
design in filigree using wire dimensions like I told you. Full size
on this image is 200%.

http://www.jeannius.com/links.jpg


#3

Make sure you have plenty of air vents cut into the mold and you
should have no problem casting it. The thickness of a lot of filigree
mtgs. doesn’t exceed that by much. Good luck.


#4

I’m sitting here looking at two small sterling pendants I cast a
couple of years ago. They are both thin pierced Celtic designs, one a
"lunette" and the other an open Celtic cross. They both measure 0.63
mm in thickness. I also have before me a commercially cast Masonic
symbol, which in the thin places is 0.62mm thick. In other areas, it
is 0.95 mm thick, and has a small “diamond” set (not glued) in the
piece. It came from the center of a buff-top stone in a Masonic ring.
This may be of white gold, I’m not sure.

An old friend helped me with my thin castings. First, the mold. It
was made conventionally, with nothing special done except more vents
than normal. To inject, we didn’t deliberately heat the mold, but
thinking back, it usually took 2 or 3 tries before I got a good
injection, which heated the mold. I injected at about 15 or 16 pounds
pressure, which is not far off your 20 pounds. There were a LOT of
vents cut into the mold, some blind, and some into the cavity. There
were still some losses, but they were in a reasonable range, about
10-per-cent failure rate.

When I sprued up the tree of about 25 pieces, each one was
separately vented to a common vent structure. Then the entire "tree"
was enclosed in a cage of the same plastic/wax vent material used in
the inside of some flasks. This in turn, even though it had no
direct connection to the tree, was heavily vented to the outside of
the flask.

I cast hot, at about 1100-degrees-Fahrenheit. After the first
experimental flasks, I got a near 100-percent casting rate on several
more flasks. The button and vents weighed considerably more than the
handfull of finished pieces!

If you had to make the model thicker, I would suggest spray painting
the back with several light coats of high-temperature engine/manifold
paint from the auto parts store. It is removeable chemically.

So 0.60 mm might be a little thin, but certainly within the possible
range. Good Luck!

Marrin Fleet
a “sometimes” jeweler


#5
Is this thing too thin to cast in sterling? 

If you can shoot wax, you can cast it. Getting a wax is usually the
hard part. Hot metal flows more readily than wax.

An expert casting company might be more efficient than you, for a
difficult project. It depends on how many reject waxes you can stand
to pull!

M’lou Brubaker, Jeweler
www.craftswomen.com


#6

Hello Kathy,

I,ve performed castings from a musquito with succes and Wings of a
butterfly.

Your problem will be the relative soft consistency of sterling
silver for small items. Age hardening will improve the casting but
still.

Anyway, it can be done. Find a company who can deal this type of
castings and the can produce you as many as you like.

Have fun and enjoy
Pedro


#7

Kathy

I’ve had absolutely fabulous success in sterling casting even thinner
pieces, but I’ve used the HiDef system in place of wax. You can get
the HiDef from Stuller, Gesswein, etc, and it uses light-curing
polymer in place of wax, so the detail and thickness is preserved
much better. It’s easier to use than wax, esp. if you are pushing 20
psi to get an even fill.

Kinda expensive in the initial cash outlay, it paid for itself
quickly, and you should be able to even reproduce filigree with it. I
torch cast, so have to almost superheat the metal with lots of super
flux, a bit of S-88 alloy from United (to reduce firescale), and a
higher flask temperature than most would use. Proper spruing in
critical too.

Read the instructions with it carefully though, don’t deviate too
much to start, and it’s a great tool for what you are trying to do, I
highly recommend it for centrifugal casting thin pieces.

Tim Dwornick
Hastings, NE
www.warpedmetal.com