HEIDI WASTWEET

BAS-RELIEF SCULPTURE & LOST WAX CASTING

There are many steps involved in making a bronze sculpture and each artist has their own methods. In these photos the process is illustrated with one of the St. Paul church door panels. Casting bronze is an art in itself and requires specialized equipment and skills. I always rely on a professional art foundry to turn my sculptures into metal

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Each project starts with extensive planning and designing. The base is constructed and the sculpture is built up with oil clay. Sculpting starts with the background images and then forward shapes added. Drapery is laid over the figures and details added. This is about 80 hours of work

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Plaster is poured over the clay sculpture to make a negative mold. Letters are carved in and another plaster cast is made. The positive plaster is worked with steel tools. The plaster holds a much smoother finish than clay. Sharp details are finished up and this is the finished model. A flexible silicone rubber mold is made from the finished plaster

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A thick wax layer is brushed into the rubber mold and the resulting wax model goes to the foundry. At the foundry (Viking Fire Foundry in the photo) wax sprues are attached and the whole thing is incased in layers of ceramic and sand. The mold goes into a furnace which melts out the wax which leaves a cavity inside. (Hence the name "lost wax" or "cire-purdue") Bronze is melted in a furnace

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A crucible lifts liquid metal out of the furnace and poured into the mold through the "cup" opening at the top. Air escapes through the vents and a bed of sand catches any spills. Unused bronze is poured back into billets to be reused later

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The bronze cools in the mold and contracts from the mouth of the cup. When it is cooled the ceramic shell is hammered away to reveal the bronze. There is much clean up work to be done to remove the bits of shell and repair imperfections. This is "chasing" the bronze. The finished bronze is still a very light color and shiny

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The bronze is sandblasted to give it a satin finish and patina (color) applied with liver of sulfur which reacts with the heat of the torch. The highlights are scrubbed back and the surface sealed with carnuba wax. This is the finished sculpture. The panel is mounted in a wooded crate to be shipped to the client in Florida. The doors are prepared ahead of time for the panels to be mounted in with industrial epoxy. Finally the finished doors. From concept to finished doors has been 13 months and countless hours


© Heidi Wastweet 2016