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
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!
a “sometimes” jeweler