What Does Cone 6 Mean? Understanding Pottery Firing, Kilns, and Temperature
Updated: Sep 16
Cone 6 is a measure of heatwork used in ceramic firing, not simply a temperature. It tells a potter that the kiln has delivered a particular combination of temperature and time, allowing compatible clay bodies and glazes to mature properly.
At Throw Clay LA, Cone 6 is our primary firing range. Understanding what that means begins with pyrometric cones, the small ceramic indicators potters use to measure what actually happens inside a kiln.
Three Electric Kilns Bailey replacing electric kiln elements. 40 Cubic Foot Geil Gas Kiln
Kiln Firing
Firing transforms dried clay into ceramic through a series of permanent physical and chemical changes. Depending on the clay body and firing range, pottery kilns can reach temperatures well above 2,000°F.
But temperature alone doesn’t tell the whole story. How quickly the kiln heats and how long the work is exposed to heat also affect how clay and glazes mature. Potters refer to this combination of temperature and time as heatwork, which is why ceramic firing is measured with pyrometric cones rather than temperature alone.
What Is a Pyrometric Cone?
A cone is a small pyramid-shaped piece of specially formulated ceramic material.
It isn't part of your pottery.
Instead, it's placed inside the kiln as a witness to how much heat the pottery actually receives.
As the kiln heats, the cone slowly begins to soften. When enough total heat has been absorbed, it bends over. That bend tells the potter that the firing reached the desired amount of "heat work." Want to learn more about cones? The Orton Ceramic Foundation has an excellent explanation of pyrometric cones and how they're used in pottery firing.
Why Not Just Use Temperature?
A kiln isn't judged only by its highest temperature. Time matters just as much as temperature. A slower firing can mature clay at a slightly lower peak temperature than a very fast firing. Cones account for both temperature and time, making them a much more accurate measurement than temperature alone.
What Does Cone 6 Mean?
The cone system provides a standardized way to describe the amount of heatwork needed for a clay body or glaze to mature. Cone 6 falls within the mid-fire range and is widely used for stoneware and functional ceramics.
In general, pottery falls into three broad firing ranges:
Low-fire (Cone 06–04): Approximately 1,830–1,945°F. Low-fire pottery is often brightly colored and more porous, making it popular for decorative work, children's projects, and some functional ceramics.
Mid-fire (Cone 5–6): Approximately 2,165–2,230°F. This range produces strong, durable pottery while offering an exceptional selection of glaze colors and finishes. It has become the standard for many teaching studios and ceramic artists.
High-fire (Cone 9–10): Approximately 2,300–2,380°F. High-fire stoneware and porcelain are extremely durable and are often fired in gas kilns, where the amount of oxygen inside the kiln can be carefully controlled. This process, called reduction firing, can produce rich, earthy colors and unique glaze effects that are difficult to achieve in an electric kiln.
Cone 6 sits at the upper end of the mid-fire range and allows many stoneware clay bodies and glazes to reach maturity while producing durable functional ceramics.
Clay vitrifies, becoming strong and long-lasting.
Most Cone 6 glazes fully mature, creating smooth, glass-like surfaces.
Properly glazed pieces are generally food safe and waterproof.
A wide range of glaze colors and effects can be achieved consistently.
That's why many community studios—including Throw Clay LA—fire primarily to Cone 6. It provides reliable, functional pottery while giving artists tremendous creative freedom with glazes and surface finishes.
Greenware drying before firing. Freshly made pottery must dry completely before it can safely go int Bisque-fired pottery. After the first firing, the clay is permanently transformed into ceramic and i Finished pottery after the glaze firing. The second firing melts the glaze into a durable, glass-lik
The journey from clay to finished pottery. Freshly made pieces (left) dry completely before their first firing. After the bisque firing (center), they're ready for glaze. Following the final glaze firing (right), they're transformed into durable, functional ceramics.
Where Cone 6 Fits in the Firing Process
Most functional pottery is fired at least twice. The first, or bisque, firing converts dry clay into a porous ceramic form that is strong enough to handle and glaze. After glazing, the pottery returns to the kiln for a glaze firing, where both the clay body and glaze mature at their intended firing range.
At Throw Clay LA, most student work is glaze fired to Cone 6. For a closer look at what happens during each firing, read our guide to bisque and glaze firing.
Electric Kilns Compared to Gas Kilns
Electric and gas kilns can both fire pottery to Cone 6, but they provide different firing environments.
Electric kilns generate heat through electric elements and generally maintain an oxidizing atmosphere, where oxygen remains available throughout the firing. This makes them highly controllable and well suited to consistent, repeatable firings.
Gas kilns use burners to generate heat, giving the kiln operator greater control over the atmosphere inside the kiln. By adjusting the balance of fuel and oxygen, a gas kiln can be fired in oxidation or reduction. Reduction changes the way certain materials in clay and glazes respond, sometimes producing colors and surfaces that differ substantially from those produced in oxidation.
At Throw Clay LA, we use both electric and gas kilns. Most student work is fired electrically, while our gas kiln gives members and more experienced students opportunities to explore different firing atmospheres and ceramic surfaces.
Why We Use Cone 6
Cone 6 gives us a useful combination of durability, glaze variety and consistency. At this firing range, compatible stoneware clay bodies can vitrify sufficiently for functional pottery, while a broad range of glazes can mature and develop their intended surfaces.
At Throw Clay LA, most work is fired to Cone 6. Maintaining a consistent firing range also allows us to manage the many different clay bodies and glazes moving through a community studio while giving potters considerable room to experiment with form, surface and glaze.
Why Understanding Cone 6 Matters
At Throw Clay LA, our studio technicians handle the firings. Students don't need to know how to program a kiln or determine when a firing is complete, but understanding Cone 6 becomes increasingly useful as their experience grows.
Members choose among different clay bodies, experiment with glazes and explore more independently. Because the studio fires primarily to Cone 6, clay and glaze materials used in the studio must be compatible with that firing range. Understanding cones helps potters make informed choices about materials and troubleshoot results involving glaze color, surface, clay maturity and the fit between clay and glaze.
Cone terminology is also a common language among potters. A glaze described as Cone 6 or a clay body formulated for Cone 10 immediately communicates something important about how that material is intended to be fired.
You may never fire a kiln yourself, but understanding heatwork and cones gives you a better understanding of what happens to your work inside one.
About Throw Clay LA
Whether you’re curious to try pottery for the first time or ready to develop your skills, Throw Clay LA offers one-time pottery experiences, six-week Build Skills courses, and six-week Refine & Explore courses in wheel throwing and handbuilding at our studio in Downtown Los Angeles.
We also offer pottery workshops and private pottery events for groups, while studio memberships provide experienced potters with dedicated space and time to pursue their own work, along with access to studio equipment, glazes, firing services and free weekly Member Clinics.
