Sink Firing – Our kiln pictured at left was designed and built by myself following the style of a large graduate kiln at the College of Ceramics at Alfred University. This popular kiln was known as the Big Motha out of respect for its considerable size and occasionally obstinate qualities. Since it takes all day to load this kiln – the shuttle car style allows the shelving to remain in place with the car pulled into comfortably heated space. The interior stacking area of the kiln is six feet long & high and 2.5 feet wide.
This sizable space is adequate to stack approximately fifty 16 inch diameter sinks with additional smaller ware stacked between each sink. Stacked with smaller cups and mugs the kiln will accommodate as many as 2000 pieces stacked with only the tiniest space between each piece.
Firing sinks takes considerable care because these larger pieces are prone to uneven heating and cooling which will produce stress fractures and even steam driven explosions if one is not very attentive. The typical glaze schedule starts in the late afternoon and continues through the night with the kiln reaching full heat late the following afternoon.
Final glaze temperature is about 1270 degree centigrade – what is referred to as Cone 10 in reference to pyrometric cones that are used to gauge glaze melt.
The average firing cycle of both bisque and glaze consume approximately 250 gallons of propane which is supplied from an external 1000 gallon tank.
The atmosphere while firing is given much consideration as the percentage of oxygen and carbon during the firing determines the final glaze color. Managing and adjusting for proper reduction is a dynamic process that is never precisely controlled.
— Dan Weaver