Editor’s note: We’ve been following Menlo Park artist Terry Guyer as he works on completion of a statue of Nikola Tesla, an artistic journey that is being chronicled photographically by InMenlo photographer Scott R. Kline. Below he recounts what happens during the bronze cast process.
“An original sculpture in clay, plaster, plastic, stone, metal, wood, or virtually anything three-dimensional, is submitted to the foundry for casting.
“The seven-foot Nicola Tesla statue original was sculpted [by Terry Guyer] out of oil-based clay (plasticine) built up over a reinforced foam armature. The 18” Nikola Tesla statue replica original was a very high resolution, rapid prototype — 3D printed in thermo plastic from an aerospace 3D scan of the 7-foot Nikola Tesla clay sculpture.
“A mold release agent is applied to the original sculpture and a silicon rubber mold material is painted directly on the original and built up in layers. The silicon rubber mold is divided and reinforced with plaster so the original can be removed and the exact shape of the original is maintained for the next stage — wax.
“Large and complicated sculptures are cut in pieces, as needed, to make the most accurate molds possible. The full size Nikola Tesla statue was cut into 8 to 10 separate pieces prior to molding.
“The empty mold is clamped together and molten wax is poured, rolled around inside the mold and poured out. This is repeated until the desired thickness of 1/4 to 3/8” is achieved.
“You now have an exact copy of the original sculpture in wax. The same mold can be reused to create additional waxes. The wax is carefully retouched to remove mold marks and any imperfections from the wax application. Additional wax sprues and gates are attached to new wax originals so that the molten bronze can pour into the entire piece and the air can be pushed out, as the spaces are filled.
“The now ready waxes are dipped alternately in a liquid ceramic and silica sand until a durable layer is built up around the wax, both inside and out. This creates a durable high-heat tolerant receptacle for the molten bronze, called a ceramic shell.
“The wax filed ceramic shell is put in a furnace just prior to casting. The furnace completely burns out all traces of the wax and hardens the ceramic shell at the same time.
“The now hollow ceramic shell is pulled out of the furnace, and while still red hot, molten bronze is poured into the voids which once held the wax.
“After cooling, the ceramic shell is broken away revealing a bronze copy of the original sculpture. The, now metal, sprues and gates are cut off, the metal is sand blasted, pieces are welded back together and retouched until it looks just like the original sculpture. It will then receive a heat applied chemical patination coloring, as desired, before installation or shipping off to a gallery.”
The unveiling of the statue will take place on Dec. 7; you can find out more and RSVP at the Tesla statue website.
Photos by Scott R. Kline
Photo captions: (Top) Dorrian Porter originator, organizer, fundraiser, and owner of the Tesla statue project; Tom Schrey, Executive Manager of Artworks Foundry in Berkeley and Terry Guyer, artist and creative production manager.
(Second photo right)Tom Schrey holding the Tesla rapid prototype original, used for making the silicon mold for casting. A sample plaster covered silicon mold is shown on the table below.
(Bottom photo) Ceramic shell of Nikola Tesla statue section (head and neck) being filled with 2000 degree molten bronze.