For my non-potters out there, this post will introduce a few new words, such as kiln and cone. For other potters and ceramicists, hopefully this discussion on cones will be as helpful for you to read as it was for me to research.
Firing and Cones in Pottery
What transforms pottery from a malleable piece of clay to something food-safe, strong, and durable is the firing process. Firing an item of pottery tends to take a while, as the piece has to be completely dry beforehand. Any moisture left in the clay could cause it to crack, warp, or even explode. In my experience, the drying time can take up to a few days or weeks.
Once the item is dry, we’re ready to fire it. Firing is … essentially baking the clay, to a very high temperature. The kiln is where the clay is fired (think: oven). There are countless types of kilns, since pottery has been around for humankind. But, I’ll go into a discussion of kilns in another post.
Temperature vs. Cone
When you fire clay in a kiln, you need it to reach a certain temperature to ensure the durability of the piece. In pottery, we refer to the temperature of the kiln as “firing to a cone”. From The Pottery Wheel, “Cones are pieces of ceramic that help you gauge whether a kiln has reached sufficient temperature and whether the pottery will have been fired the correct amount. Cones measure ‘heat-work’, which is a combination of the temperature reached, and the time it took to become that hot.”
To clarify, the cones measure the temperature the kiln reached, and also the amount of time it took to get to that temperature, and how long it lasted at that temperature. If this is slightly confusing, don’t worry. I’m still confused too.
Another interesting fact from The Pottery Wheel: “During firing, a piece of pottery undergoes chemical and physical changes. These changes will take place at different times, depending on how quickly the temperature is changing in the kiln. Cones help you gauge when the pottery has undergone the changes needed to have turned into ceramic.”
The name of the cone is visually representative.
I’m going to let this all sink in. In my next post, I’ll discuss more in depth the differences between the cones and how we can use them!
To finish, an short video explanation of cones (that goes a bit more in depth than I did here):
