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.

[@arenasartgalleryl]

Thanks for the good bisque firing info.

[@marcisaacs9407]

Great presentation 🙏

[@kencoxdesign]

I've got a gas kiln I made out of an old clothes dryer drum with ceramic fiber insulation and a single weed burner that I use for both bisque and glaze. I was seeing substantial soot if I candled with the gas, so switched to drying my pieces in an electric oven at 190F for an hour or so while I'm setting up the kiln. My firing schedule is way more aggressive with cone 05 in about 60 minutes. Once the cone falls I pull out the weed burner plug up the chimney and fire hole and let it all cool for about 8 hours before venting the lid for another hour to get rid of the last of the heat.
I'm firing wild clay that's been spiked with ample mullite and kyanite for raku so it seems to not mind the accelerated ramp up to 1900F. I use BBQ propane tanks which are about $20 USD to refill and get 3 or 4 firings out of each one, so $5-$7 per firing. For raku, it's the same except I pop the kiln at 05 and set stuff on fire with the glowing pots.

[@liamg1995]

That sounds like a neat process! I'm happy that you have found something that works so well for you. I love wild clays and I have found them to be more resilient in so many ways when compared to commercial clays. the dry strength is often crazy good. there is a clay that is local to me that is so strong when dry, that I can stand on a greenware flowerpot turned upside down without it cracking! happy potting!

[@gato_fofo]

TOP!🇧🇷

[@lisalovelylpa]

Why not a pyrometer for bisque firing ? I would think that’s when you have to monitor the temperature change more closely ?
Great video.

[@liamg1995]

There is certainly nothing wrong with using a pyrometer! I just don't find them necessary. After a while you get to judge temperature fairly accurately by eye and your senses, and only rely on the cone for the indication of the final temperature. Happy bisquing!

[@wendydee3007]

Good video. Can you estimate the cost for a firing? I'm trying to work out whether to get a gas or electric kiln. Thank you :o)

[@liamg1995]

Hi Wendy! I estimate that a firing to cone 10 in this kiln costs between 10 and 20 dollars depending on the price of propane. A bisque is a big less. A 100 lb tank costs about $65 to fill here these days. I also have a downdraft kiln that is slightly more efficient.

[@wendydee3007]

@@liamg1995 Thank you :o)

[@ionelima9637]

Qual o nome desse massarico

[@user-wr8vz6bp4d]

What type of brick is this?

[@gato_fofo]

Tijolo refratário, também pode utilizar manta cerâmica 50mm, 128kg/m3 para até 1400 graus Celsius, um pouco mais caro mas, com resultado rápido e fantástico. Fiz um forno para Raku usando um tambor de 200L. Abraço!