Candling is holding a kiln at a low temperature, below the boiling point of water, for several hours at the start of a firing, so any moisture left in the clay leaves slowly instead of turning to steam and cracking the work.
What Is Candling?
The term comes from the days when potters warmed a kiln with a small flame like a candle before the real firing began. In an electric kiln it is usually a programmed hold somewhere between about 80 and 95 °C, or a very slow first ramp, often left overnight.
Candling is most useful for thick pieces, sculpture, work that was finished in a hurry, and loads where you can’t be sure every piece is bone dry. Ceramic Arts Network points out that it is water, not trapped air, that causes kiln explosions, so giving that water time to escape is the real protection.
It doesn’t replace proper drying. A piece that is soaking wet will still struggle, and candling adds hours and electricity to every firing. Many studios candle the bisque by default anyway, because one explosion can damage everyone else’s work in the load. If you fire with a studio, tell them when a piece is thick or was finished recently so they can plan the load around it.
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.