Sand casting involves making a mold out of foundry sand, which is a
special fine sand mixed with binders to make it hold shape perfectly. The pattern, or
positive -which is always made of a rigid material, like plaster- is placed in a form and
the sand is packed tightly around it.
The pattern must then be removed from the sand, leaving an impression -kind of like a
footprint on the beach. If the piece is to be hollow, a core is cast in sand out of the
mold just formed and then pared down by about ¼ inch all over. This core is then
suspended in the cavity by 'chapelets', which are small metal supports that become part of
the final casting.
Molds for sand casting can be made in one, two or more pieces, and fitted together for
complex shapes by using different welding techniques.
There are many kinds of sands and binders, some of which retain their initial softness,
some that go hard by themselves, and some that harder either by baking or by the
introduction or carbon dioxide gas.
Sand casting is a special method requiring special skills and techniques, getting high
quality and detail levels for any different size pieces.