How to Fire a Pottery Bisque Firing in a Gas Kiln

This video discusses the process of bisque firing stoneware. I don't keep a firing schedule for bisque firings but here's an approximation. All the work I fired in this kiln was bone dry. In programmable kilns it is possible to dry work out by holding the kiln at a low temperature for a long time ( this is called candling), but I choose to only fire dry work. Candling for long periods in a non- programmable gas kiln is arduous and impractical. I candle slowly to 200 degrees Fahrenheit and hold that temperature for about an hour. I then climb slowly to 300 over the next hour. I then fire to 900 over the next 2 hours. By this time the kiln would usually need turning up again, but I don't - instead I use the slowing rate of climb to my advantage to move through quartz inversion slowly, ending at roughly 1200 degrees. During this stage a crystalline change happens within the silica in the clay. A rapid ~2 % expansion results, and if pieces move too quickly through this temperature range cracks can occur. After this stage, the firing can progress much more quickly and the kiln reaches cone 08 about an hour later. Most of my bisque firings last between 6 and 10 hours. Though bisquing is not always necessary for the production of glazed stoneware pots, it's commonly done. Here's a few reasons why: if a pot were going to fail due to a crack because of improper drying, compression, air inclusion (though I find pots with bubbles often do survive) or whatever else, they will most likely do so in bisque. These pots can now be "weeded out" before glazing and glaze firing. An explosion in a glaze firing can ruin a whole firing with little fragments stuck in every open glazed vessel. A higher percentage of good pots per glaze firing means a lower firing cost per pot and is a far better return on your time investment spent glazing, wiping, decorating, kiln stacking etc. Bisquing also makes pots stronger. This makes them easier to handle while glazing, decorating and loading into the glaze kiln. It also reduces the probability of glaze defects during glaze firing. Bisquing is relatively efficient. Because you can so densely stack a bisque kiln. You can sometimes get twice or three times as much ware in the kiln as you could during a glaze firing. Because bisque firings are to a low temperature, (cone 08), they are also short and consume little fuel.
Though Bisquing is common, many potters choose to raw glaze and once fire their work. This was done widely throughout most of ceramic history, and is a viable and practical practice today for those who are brave and determined enough to perfect the process.