This continues our report from 7/28/08 on the foundry bell creations …
Once the stylus tools have been used to mark designs into the sand, the cope and drag sand blocks are put back together. Now, negative space exists where the aluminum pattern was. Removing the snap-flask reveals the cube of sand, with spru holes through the top. A metal sleeve providing extra support during the pour is fitted around the sand cube.
In the foreground, bronze ingots glint in the sun while the propane-fired furnace melts others inside a silicon-carbide crucible vessel. While bronze as a material (comprised primarily of copper alloys) melts at 1700F, this furnace heats the metal all the way to 2200F, enabling the bronze to maintain its liquid state long enough to do successive pours.
Thus, a series of sand blocks in sleeves are laid across the deck of the Foundry Apse, awaiting the pour.
While two artists balance and pour the crucible of molten metal using foundry tongs, others stand ready to pitch sand onto any stray pools of bronze.
The melted metal enters the spru hole and follows a channel to the cavities formed by the aluminum patterns. In only a few minutes the metal cools back to solid state and soon enough the bells can be broken out of the sand molds.
This report continues on 8/1/08.