Burn-Out/Patch
The piece, now coated in raw ceramic shell, is fired in a kiln. This cures the shell and eliminates the wax, leaving a cavity in its place. (Thus the term “Lost Wax” or “Cire Perdue” casting). The kiln is fired with natural gas from three blowers. A cage is loaded with the shells which are placed upside down so the wax can flow down through the exposed opening in the cup. The kiln is preheated to ~1500 degrees farenheit and then the floor of the kiln is lowered to accept the cage. The cage is placed on the floor and then quickly raised back up so the wax begins to melt as fast as possible.

Once the wax has melted into the water basin below the kiln the ceramic continues to be fired and cured for an additional 2 hours. This is done at a consistent temperature so that the ceramic can cure and that all residual carbon material from the wax will burn out of the shell cavity. When the shell has completely cured it will appear bright white and will “ping” like other fired ceramics.

The burned out shells are allowed to cool fully. Then we use a patch material made from similar materials to the shell itself to patch the expansion holes we drilled so that no bronze can leak from them during the pour. This patch material will harden and cure during the preheat of the mold before the pour. The cup opening is left completely open except for a thin layer of aluminum foil which will keep debris out of the shell. The fired shells are then staged until they our poured during our regular Saturday afternoon pours.