From Clay to Bronze
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Creating one-of-a-kind bronze sculpture in the studio and foundry of
Georgia Gerber
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Step 1:
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Georgia sculpts in water-based clay. |
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| Step 2: |
The finished sculpture is
sectioned into castable sized pieces with thin metal shims. |
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| Step 3: |
An investment, made of
sand, plaster and vermiculite is applied to each section to a thickness
of about five inches |
| Step 4: |
Each section is removed and
cleaned. There is now a negative imprint of each section of
the sculpture captured in plaster. |
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| Step 5: |
A 1/4 inch thickness of wax
is pressed against the negative imprint. |
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| Step 6: |
A "plumbing"
network of wax (sprues and gates) is connected to the wax. |
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| Step 7: |
The entire section piece,
with the pressed wax and sprue system attached, is encased in a larger
cylinder of plaster--with part of the plumbing system protruding out the
top |
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| Step 8: |
The cylinder is placed upside
down in a large kiln and heated with propane to 1000 degrees F for about
48 hours, which evacuates the wax (hence, the "lost wax"
method). This leaves a void inside the a cylinder wherever
there was wax. The negative plaster imprint imbedded inside the
cylinder now has a 1/4 inch void adjacent to it's surface, connected to
the voids left by the melted plumbing network. Since this network
originally protruded out the top of the cylinder there is now a hole
that provides access to all voided spaces in the cylinder. |
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| Step 9: |
The cylinders are placed
right side up in a pit and surrounded by sand to re-enforce the molds as
the molten metal is poured in. |
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| Step 10: |
Bronze ingot are melted in a
furnace to about 2,000 degrees F and poured into the hole in the top of
the cylinder. The molten metal flows through the plumbing system
and fills the 1/4 inch space against the negative plaster imprint,
taking on the positive form. As it cools, the metal maintains this
positive form and so replicates that section of the original
sculpture. |
| Step 11: |
After cooling, the cylinders
are broken open and the raw castings cleaned. The plumbing
system--now replicated in bronze--is cut off to be recycled in the next
melt. |
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| Step 12: |
The individual cast sections
are welded together, like pieces of a puzzle, to form the bronze replica
of the original clay. |
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| Step 13: |
All welding lines and other
flaws are tooled by skilled artisans to make a seamless bronze
sculpture. |
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| Step 14: |
The final step is the
application of patina chemical--usually to a heated bronze--to get the
coloration desired. Finally a number of coats of wax are applied
to seal and protect the finish. |
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Located on Whidbey Island