Information on Cone Ratings | Big Ceramic Store
We recommend always buying a kiln that is specified for a higher temperature than you plan to fire.
Less than 5% of people with electric kilns actually fire them to Cone 10 but in case you are looking to fire to Cone 10 ALL THE TIME, please read our Tip #106 on TRUE Cone 10 Kilns to help you pick the right kiln.
If you plan to fire mostly to Cone 6 or 8, a regular Cone 10 kiln will be a good fit.
Most people fire Cone 6 in an electric kiln, because Cone 10 is a lot harder on elements and uses more power.
Also remember that you can get excellent Cone 5/6 stoneware and porcelain clay and that there are tons of great glazes available for Cone 5/6 that will deliver stunning results at Cone 6.
If you really want to fire Cone 10 in an electric kiln, we recommend a TRUE Cone 10 kiln.
CONE TEMPERATURE CHART (FOR THOSE OF YOU WHO ARE NOW WONDERING WHAT CONE MEANS!)
Kilns are not fired just to a temperature. They are fired to a "cone" level, which accounts for time as well as temperature. Think of it as heat absorption rather than just temperature.
Cone's come in different numbers, each of which corresponds to a heating rate / temperature combination which will make that cone deform. At the beginning of the firing the cone is standing at an 8 degree angle. A perfectly fire cone will be best to a 90 degree angle. If the cone is bent less, the kiln was under fired. If the cone is bent more, the kiln was over fired.
Notice the way the cones are numbered. The hottest is 10, going downward to 1. Then as it continues to getting cooler it continues at 01, 02, etc. So there is a BIG difference between cone 5 and cone 05!
|Cone number||Orton Cones
Final temp in degrees F at ramp rate of 27 degrees F/hr
Final temp in degrees F at ramp rate of 108 degrees F/hr
Final temp in degrees F at ramp rate of 270 degrees F/hr
In standard firing, cones of the right number are placed around the kiln and are watched. When the cones fall the kiln is turned off. This works the same for gas and electric kilns.
Automatic electric kilns such as the Skutt Kilnmaster series have a thermocouple which continuously measures the temperature, records it over time, and shuts off when the appropriate heat absorption has been met. So if the ramping temperature is fast, the kiln will go to a higher temperature before it turns off than if the ramping temperature is slow (thus allowing the clay to absorb more heat along the way.) The final temperature is most affected by the rate of temperature increase over the last 300 to 400 degrees of firing.
Think of the 0 in a cone number as meaning "minus". So 06 is much cooler than 6 because it is like a "minus 6".