A tour of the foundry process
I. Molding
1. A rubber mold is created by applying several
layers of rubber on a sculpture in various consistencies, which capture exact
detail and maintain form.
2. A "mother mold," made from plaster, is
applied on top of the rubber mold in such a way that can it can be pulled apart
upon drying. The "mother mold" is used to maintain the overall shape of the
rubber mold after the rubber mold is cut apart.
3. The rubber mold is cut apart on registration
seams which were set during the process of applying the rubber. The rubber mold
is then pulled off the sculpture and cleaned.
II. Wax
1. The mold is reassembled, heated, and several
coats of hot wax are poured into the mold. After completely cooling, the mold is
removed from the now hollow wax copy of the original sculpture.
2. A wax artist then touches up the wax copy,
taking out any seams or defects which may have occurred during the pouring
process.
3. The wax artist then engineers a sprew system
of wax bars to the wax copy complete with a wax cone on the bottom. Correct
engineering of the sprew system has a large impact on the quality of the bronze
casting later on.
III. Slurry
1. A ceramic mold is created by layering many
layers of a liquid mixture called slurry, and sand over the wax copy and sprew
system. The first few layers require using a very fine sand to capture fine
details. Course sand is then used to create strength in the ceramic mold.
2. With the ceramic mold completely dry, a hole
is cut out of the cone section of the sprew system. This becomes the funnel for
when the bronze is poured into the ceramic mold.
3. The wax is melted out of the ceramic mold in
a specially designed furnace which allows the wax to drip out into a catch
basin.
IV. Casting
1. Each mold, now called a shell, is again
reheated to about 1800 degrees F. At the same time bronze is melted and heated
to 2100 degrees F in a caldron.
2. Using heat resistant suits and gloves, the
shells are removed from the furnace and are hung on racks while two other people
pour the bronze into the shells.
3. After the bronze cools down, the shell is
removed with chipping hammers and with sandblasting.
V. Metal
1. The now bronzed sprew system is removed from
the piece with a torch.
2. One sculpture may consist of many parts which
were cut apart during the rubber molding and/or wax processes. The different
parts go to a metal artist who then welds the sculpture back together and with
grinders, sanders, and chisels retextures the sculpture to make it resemble the
original sculpture.
3. The sculpture is sand blasted, checked, and
touched up as many times as it takes to meet the artist's approval.
VI. Patina
1. The patina artist applies color to a bronze
piece according to the artist's instruction. Using a large blow torch, brushes,
scrubbers, and a great deal of experience, a veteran patina artist can create an
unlimited variety of color schemes.
2. The piece can then be sealed with clear wax
then buffed.
3. The piece may then be based on wood or stone
for display.
