When it comes to firing ceramics, different types of clays and glazes are rated for different temperatures. A kiln firing chart, also known as a cone firing chart, is a useful tool for understanding the effects of temperature on different types of clays and glazes, as well as determining what firing schedule setpoints should be used depending on the cone rating of the media you’re firing.
What Temperature Is Pottery Fired At? Understanding Different Types of Ceramics
What temperature is pottery fired at? Well, that depends. There a three main types of clay that are used to make pottery: earthenware, stoneware, and porcelain. Each of these has different temperature requirements, as well as different properties once fired.
Earthenware clay is the most common type of clay used in ceramic firing today. Earthenware is softer than the other types of clay, making it easier to work with and more forgiving. Earthenware also has the lowest firing temperature requirements, which is why it was the first type of clay used to make pottery during the early stages of kiln history.
Since earthenware is fired at lower temperatures, it typically remains porous, relatively soft (you can scratch it with a knife!), and still absorbs water. Glazes are often required to make earthenware harder and watertight.
Stoneware is a “mid-range” or “high fire” clay that requires higher firing temperatures and a longer firing schedule than earthenware. Once it has been fired, stoneware is hard, dense, and rocklike – hence the name!
Stoneware reaches maturity between 2000° F and 2400° F – hotter than lava!
Stoneware is typically fired between Cone 2 all the way up to Cone 12, with Cones 7 and 10 being the most common for mid-range stoneware and high fire stoneware, respectively.
Since stoneware is fired at higher temperatures, it has time to fully vitrify, or form a glassy, nonporous bond on its surface. Finished stoneware is durable, hard, and nonporous. Unlike earthenware, stoneware is waterproof once fired even without the use of glazes.
Originating in China in 1600 BC, porcelain is a “high fire” clay that produces extremely hard, shiny, often white or translucent ceramics. Also known as kaolin clay (named after Kao-ling hill in China, where it was mined for centuries), raw porcelain is extremely dense and difficult to work. Often, porcelain is mixed with other types of clay to improve its workability.
Porcelain typically reaches maturity between 2381° F and 2455° F – however, pure kaolin reaches maturity at 3272° F!
Porcelain clay is fired between Cone 10 and Cone 13.
Once fired, porcelain is extremely hard and fully vitrified, making it watertight and non-absorbent. Porcelain is noted for its distinct white color.
Understanding Firing Cone Ratings
As we mentioned earlier, different ceramic materials and glazes have a cone rating. Firing cones, or pyrometric cones, are a simple pyrometric device that indicate kiln temperature. Firing cones melt when exposed to a certain temperature for a prolonged period of time. Different ceramics and glazes are given a cone rating to indicate the temperatures at which they’ll reach maturity.
Firing cones range from 022 to 14, with 022 being the lowest temperature and 14 being the highest. As you’ll see on the kiln firing chart below, when a firing cone rating has a ‘0’ in front of it, a lower number indicates a higher fire temperature.
However, for firing cones without a ‘0’ in front of their rating, higher numbers indicate higher firing temperatures.
Kiln Firing Chart [Infographic]
In the kiln firing chart below, you’ll be able to see which temperatures correspond with various cone ratings and materials. The color gradient indicates the incandescence of the kiln at various temperatures, and the column to right indicates how the physical properties of ceramic changes at each temperature.
Reach the Right Setpoints on Your Kiln Firing Chart with Ease and Precision
The TAP and TAP II Controllers by SDS Industries are the most advanced, precise, and easy-to-use pottery kiln controllers on the market today. With responsive touchscreen controls, an intuitive graphical UI, and integration with the TAP Kiln Controller Mobile App, TAP Kiln Controllers can pair with any relay-controlled kiln or oven to allow you to easily manage and execute your kiln firing schedules.
We invite you to explore our selection of digital kiln controller, standalones, and conversion kits on our online store. You can also purchase TAP Digital Controllers or TAP-Controlled Kilns and Heat Treat Ovens through one of the following distributors:
- Hot Shot Oven & Kiln
- Mobile Glassblowing Studios, LLC
- Jen-Ken Kilns
- Kiln Frog
- Sheffield Pottery
- Delphi Glass