(too'-fah) is a soft, porous, chalk-like material (essentially
limestone). It is formed as underwater springs rich in calcium mix with
lakewater that is rich in carbonates (as in baking soda). A chemical
reaction occurs, resulting in calcium carbonate - limestone. Over
decades to centuries, a tufa "tower" forms underwater. Tufa is
found today in dry lakebeds. The photo at left shows tufa in its
natural state. A saw is used to cut the tufa into a block and a design
is carved into it, in this case, a naja.
After applying a coating of carbon to the design to ease removal of the casting, the tufa is clamped together with a "blank" cover piece as shown in the next two photos...
Scrap silver is then melted down and poured into the mold......