Noel, or others: Can you explain a little about sand casting.
I have been experimenting, but with methods, not materials. I use a
sand casting kit bought from Indian Jewelry Supply. It includes a big
can of treated sand that is pretty sticky. Also a crucible, “parting
powder” (talc, or something like it), boric acid as flux, and a steel
two-part frame with a pouring spout opening. Rio also sells a kit, a
"Delft casting kit" with similar sand and a tiny round mold that I
find nearly useless.
You pack sand into one side of the mold and press your model into
it. The model must be able to stand up to having the sand hammered
down on it, and must have no undercuts. It can be a twig or other
natural object, a metal model, a baked polymer clay model, etc. One
student cast Barbie shoes. The model is pushed in halfway; the sand
is dusted with powder, then the other half of the frame added and
filled with sand. The more firmly the sand is packed, the better the
detail of the result. I use a hammer to compress the sand.
The frame is opened and the model carefully removed. A sprue opening
is carved in both sides of the sand along with vent openings from
extremities of the cavity to the sides of the frame. The frame is
bound together with binding wire, set upright, and molten metal is
I have learned that the larger the sprue, the greater the chance of
success. I have had good results from pre-heating the whole mold to
300-400 degrees to slow the solidification of the silver. Higher and
the sand begins to burn. I have even filled the mold successfully in
a centrigugal casting machine, but I cannot promise that if you try
it, the sand will not fly all over (along with the silver, of
The sand exposed to the hot silver has to be scraped off and thrown
away, but the rest is re-usable.
This method will not work very well for some large models, small or
thin models or areas of models, but then, if it doesn’t work, you
re-cast the silver and all you’ve lost is a few minutes. And it does
not harm the model, which is great.