There are many steps involved in making a bronze and each artist has their own methods. In these photos the process is illustrated with the University of Washington's Medal of Honor Monument. The sand casting was done at the Caldwell Studio with many thanks to the expertise of Judith & Daniel.
The project starts with a concept and sketch. Since this is going to be a large piece, an 8" maquette is made. The actual size model is built up with clay. A form surrounds the clay to contain the poured plaster mold. Steel tools are used to carve text into that negative mold.
Plaster is poured over the negative to produced a positive model. The positive plaster is finished with steel tools. The plaster holds a much finer finish than clay. The finished plaster is coated with graphite. Contained with a wood frame, wet casting sand is packed around the plaster sculpture.
Wood frame removed, the cured sand mold is hoisted off the plaster. When cured, the green sand turns dark grey. The first half of the mold is cleaned up and coated with graphite. A foam layer is laid in the cavity of the sand. The thickness of the foam determines the thickness of the bronze.
The wood form is put back on and fresh sand packed in. The fine sand has been pre-mixed with binder agents. The foam is removed, vents and channels carved in, and both sides bolted together. Bronze was poured into the cavity and when cooled, the sand mold is hammered off to reveal the casting.
The next step is to grind off the channels and flashing around the edges. Sand blasting reveals the bright bare bronze. A patina is applied to bring out the contours of the sculpture and sealed with wax. Lastly, the bronze is mounted into the pre-cut pre-installed rock.