High Fire, Mid Fire, Low Fire, Oh My!
- , by Haley Stanaford
- 3 min reading time
There are so many clays and glazes out there and all of them have their own personalities, looks, and firing temperatures. Knowing what temperature you fire to is incredibly important to ensure that your pieces come out the way you want them to, without harming anything else in the kiln.
Temperatures are measured in “cones” which are a unit of measurement but also physical things that will melt in the kiln when the cone’s temperature is met. You can find those here. Cones, as a measurement, are arranged in numerical order, but before cone 1 the numbers add a zero before them and go in reverse order. Think of the zero kind of like a negative. You can see the number laid out on my chart below. Cone 06 is (relatively) cold compared to cone 10. It is also important to note that cone 06 and 6 are not the same thing! 06 is a lower temperature than 6 so always make sure to specify and notice whether your temperature begins with a 0 or not.
You can also see the exact temperatures and cones laid out on a cone chart, like this one from Skutt.
As you can see from the charts, there are three main ranges of temperatures that are used: low fire, mid fire, and high fire.
Low fire refers to cone 06-04 (1828-1945 degrees F). Low fire is a common form of firing.
Earthenware clay bodies are low fire clay bodies and most paint your pottery places utilize low fire in their studio.
Mid fire refers to cones 5 and 6 (2167 and 2232 degrees F) which are typically used in electric kiln fired pottery. Many community studios and schools utilize mid fire in their work.
High fire refers to Cone 10 (2345 degrees F) which can typically only be reached in a gas kiln. Many universities will have cone 10 firing in their studios.
Now with each range of firing, there are clay bodies and glazes to go with that range. It is incredibly important to pick a clay body and glaze that fit your temperature. Cindy Bracker told me an amazing analogy for this. Your foot is a certain size so you want to get that size sock and that size shoe. If you got the wrong sized sock but the right sized shoe your sock wouldn’t fit! If you got the right size sock and the wrong sized shoe your shoe won’t fit! In that same way, you have a certain temperature that you are firing to, so buy the same temperature clay for the firing as well as the same temperature glaze for it so everything will fit together nicely.
When glazes, clay bodies, and temperatures are not a good match, melting, crazing, and bloating can all happen and potentially ruin your pieces, others’ pieces, and or the kiln! Always make sure you are buying and using the proper temperature items in your studio practice!
Haley Stanaford is currently a Post Baccalaureate student in ceramics at the University of Kansas where she is currently taking a Clay and Glaze Formulation taught by Colby Charpentier in addition to her studio practice. She also is a Sales Representative at Bracker’s Good Earth Clays in Lawrence, Kansas.
