The Casting Process
For the last 21 years, Zenos has cast all his bronzes at Laran Bronze Foundry. (www.laranbronze.com) Owned by Lawrence Welker III, his wife Diane and his brother Randy, Laran Bronze is a full service sculpture foundry located in the former Sun Ship Building in Chester, Pennsylvania.
In a building formerly devoted to manufacturing oil tankers for World War II and constructing ships, the Honor Guard sculpture was transformed into bronze.
After a final visit for review of the sculptures by AFMF President General Grillo and Executive Director Pete Lindquist, and upon approval of the eight-foot high clay models by the Board, Laran Bronze began the long process of casting the sculpture in bronze using the lost wax process. First, foundry workers painted a mold made of rubber over the entire surface of the clay figures, flags and battle streamers.
When dry and while still in place on the clay figures, the rubber mold was divided using metal seams, called shims. This created smaller, more easily handled segments of the sculpture. A plaster “mother mold”, applied over the rubber molds, held and supported them.
When the plaster was dry, both the plaster and rubber mold sections were taken apart, and the clay was returned to the studio to be rolled down and used to create another sculpture in the future.
After the clay was removed and the interiors of the molds were cleaned, the molds were put back together and wax casts of the sculpture were made in each mold.
When the wax was cool and hard, the molds were taken apart again and the waxes were released. Waxes are intended to be exact copies of their clay counterparts.
Sculptors work on the wax pieces to refresh and refine the details and remove seams created by the molds, a process that can take weeks. When the sculptors were finished working on the wax models of the Honor Guard sculpture, wax straws, called sprues, were attached to these casts.
The completed waxes were then encased in ceramic shell by immersing the wax into investment liquid several times. On the first immersion, a fine powder was applied. Course ceramic sand was applied on the second immersion. The process was repeated, increasing the coarseness of the material each time to create a ceramic shell. Each new layer dried before the next layer was applied.
In the part of the process known as burn-out, the ceramic shell was placed in a kiln and fired. As the ceramic shell bakes, the wax melted and was lost from the shell, giving the process its name.
The ceramic shell was then taken out of the kiln, and molten bronze, heated to 2100 degrees Fahrenheit, was poured into it. The cast cooled for several hours.
When cool, the shell was broken away with hammers to reveal the bronze cast. Fragments of ceramic shell were sand blasted away and the sculpture was reviewed. All the individual parts of the sculpture cast into bronze were welded together. All indications of welding, including seams and spots, were ground away with metal tools. Zenos “chased” (hand carved) the bronze to restore details.
Upon completion of this process, the sculptures were reviewed by General Grillo, Pete Lindquist and several Honor Guard specialists before the patina (surface coloring) was applied.
A great deal of consideration was given to the choice of patina. Zenos felt that the traditional brown patina would not compliment the stainless steel and stone in the area. He thought that a blue-gray patina would resonate better with these materials and, as blue is the color of the Air Force uniforms, it would be an appropriate fit. Zenos wanted to distinguish the Air Force Memorial Honor Guard sculpture by this color and keep it from being dismissed as just another constellation of brown bronze figures.
He shared his ideas with architect James Ingo Freed who first leaned toward the traditional brown bronze, but reconsidered and changed his opinion in time. The Air Force Association felt that the blue-gray patina was a good choice, and so did the U. S. Commission of Fine Arts. The Board approved the patina and the process of surface coloring was started.
The bronzes were heated with blow-torches, and chemicals were applied with brushes to achieve surface coloring. In order to make the blue surface color stand, chemicals that comprise this patina must be separated from the bronze itself by a first patina of black on the bronze. After the black patina was created, chemicals that form the blue patina were applied. A sealing wax which also contained elements that support the blue-gray patina was put on the surface of the bronze to seal it.