Potters talk about firing to "Cone 10" or "Cone 06". This is our shorthand for saying we fire to a certain temperature. Pyrometric cones are little pieces of ceramic material that are sold to potters to tell us the temperature conditions in our kilns. We normally place a set of three or four cones (a "cone pack") near a peep-hole in the kiln and watch them in the later stages of the firing process. The first of those cones is one that melts or bends at a temperature a little below where we want to fire, the second is chosen to match the temperature we want and the third bends only if we got the kiln too hot. Most potters place several cone packs throughout their kiln so they can know how uniform the firing is and make necessary adjustments as the firing proceeds. We find cones to be more reliable and generally less expensive than trying to use thermocouples which have relatively short life in a kiln environment. Cones are also better indicators of what the clay and glaze is actually experiencing in that they are sensitive to a combination of temperature and rate of temperature rise. Cones are numbered in an unusual way starting with an "0" (we say oh, not zero) in front of the number and counting down; when 01 is reached then you start over and count up without the "0". Hence cones that represent increasing temperatures (and the temperature in degrees Fahrenheit that they correspond to in parentheses) would be: 022 (1110) ... 010 (1640) ...06 (1820) ... 01 (2080) ... 6 (2230) ... 10 (2380). Ask a potter what cone they fire to and you've passed the first test of "potter talk". At Frog Pond Pottery, I normally bisque fire to cone 06 and glaze fire to cone 6 which is considered the low end of the stoneware temperature range. In general earthenware is fired to cone 06 to cone 01; stoneware is fired to cone 6 to cone 10 or 11; porcelain is fired to cone 6 to cone 12.

© Frog Pond Pottery 2012