This summer I took a class in lost wax bronze casting at the Indianapolis Art Center. Class began on June 7 and convened every Thursday thereafter. Glenn Evans was the instructor. Since our class was attended only by Otto and myself, we got combined with the mold making class taught by Bernie Carreno. So we had the benefit of learning from two great instructors.
The first step was to cast wax into the silicone mold. I was somewhat ahead of the curve because I brought my own silicone molds to class. I elected to cast two of my sculptures, the Dragon Crest and the Luna Draco. These are very easy pieces to do as both are relief sculptures that hang flat on a wall.
The next step was to mount the wax cast onto a stick of wax with a cone of wax on the top forming the pour spout (see photo).
A ceramic suspended mixture called slurry is made by combining a special liquid with a powdery silicate flour and other chemicals. The slurry has a thick viscosity comparable to a heavy oil or a thin cake batter. Every evening as class began we stirred the slurry with the aid of an old drill press. Once the slurry was sufficiently stirred we would then proceed to dip the wax sculptures into the slurry. We had to dip the wax a total of nine times waiting between each dip a full day to allow for drying.
The slurry dries to a hard shell. The top of the shell pour spout is cut off and the steel hook used to hang the wax is removed. All of the wax inside of the ceramic shell must be melted out and a cutting torch was used to remove the central wax stick. The ceramic shell is then put into an oven to finish melting the remainder of wax out of the shell. Once free of the wax the shell is baked in a ceramic kiln for 12 hours.
Finally the day of the pour the shells are ready to receive the hot molten bronze. Working with molten bronze is a very dangerous task and must be done with extreme caution. An accidental spill could result in severe burns or death. The bronze melts at about 1800° F and the furnace continues to heat the bronze to about 2200° F in preparation for the pour.
Using special tools the graphite crucible containing the molten bronze is lifted out of the furnace. Two people using a shank lift the crucible and pours the bronze down into the ceramic shell spout. Within approximately 5 minutes the metal re-solidifies and slowly begins to cool. Once the bronze has cooled, the ceramic shell must be broken and chipped away from the sculpture.
The veins or gates from the pour spout to the sculpture must be cut away and the task of finishing the bronze sculpture begins. I would recommend this class for any artist or serious collector. Once you see what it takes to produce a bronze sculpture you will never again question the price of that sculpture. Not only does the raw bronze cost about $6.00 per pound but there is a lot of skilled labor and additional material costs to take a sculpture and create a silcone mold, complete the wax prep work and slurry. To fully understand the combination of artistic creativity with the complexity, cost, and time of bronzing gives one a whole new appreciation for these beautiful works of art.
