Mid fire means firing pottery to about cone 5 to 6, roughly 1200 to 1225 °C. It is now the most common range for stoneware and porcelain in electric kilns, giving durable ware with less energy and kiln wear than cone 10.
What Is Mid Fire?
Over the past few decades, clay and glaze makers have developed stoneware, porcelain and glazes that mature at cone 6 rather than cone 10. Orton lists cone 6 at about 1222 °C when the final heating is 60 °C an hour, compared with about 1285 °C for cone 10.
Firing lower saves electricity, shortens firings, and extends the life of electric kiln elements, which is why most community studios and home potters now work at mid fire. Mid-fire clays become dense and strong, and glazes can be durable and food safe when formulated and fired correctly.
Many popular commercial glaze ranges are made for cone 5 to 6, and published glaze recipes for the range are widely shared. The key is matching clay, glaze and firing: a cone 10 clay fired at cone 6 stays porous, and a low-fire clay fired to cone 6 can melt.
When you buy clay for a studio that fires to mid fire, look for cone 5 to 6 on the bag and check the absorption figure on the data sheet.
This pottery glossary entry from Le Studio Art Space is general educational content. Always follow the clay, glaze and kiln makers’ data for your own materials and equipment.