Introduction
If you're new to ceramics, kiln cone ratings can seem confusing. Cone 6? Cone 10? What does that even mean, and why can't we just use degrees? This guide explains the cone system clearly so you can shop for a kiln — and talk to your clay supplier — with confidence.
The Cone System Explained
The cone rating system was developed by Edward Orton Jr. in the late 1800s as a standardized way to measure heat-work in a kiln. "Heat-work" is the combination of temperature and time — a kiln that reaches 2300°F slowly does more heat-work than one that spikes to 2300°F quickly.
A pyrometric cone is a small pyramid of ceramic material formulated to bend and melt at a specific heat-work level. When cone 6 bends over, the kiln has done cone 6 work — regardless of whether the actual temperature was exactly 2232°F or a few degrees off.
Common Cone Temperatures
| Cone | Approximate Temp (°F) | Common Use |
|---|---|---|
| Cone 06–04 | 1823–1940°F | Earthenware, bisque firing |
| Cone 6 | 2232°F | Mid-fire stoneware, most studio pottery |
| Cone 10 | 2350°F | High-fire stoneware, reduction firing |
What Cone Do You Need?
The cone you need depends on your clay body and glazes. Most commercially available stoneware and glazes are formulated for cone 6 (also called "mid-fire"). Cone 10 is popular among potters who fire in gas kilns or want certain glaze effects that only develop at higher temperatures.
Check the packaging of your clay and glazes — they'll list the firing range. Your kiln must be rated to reach that cone.
What This Means When Buying a Kiln
When shopping for a kiln, check the maximum cone rating. A kiln rated to cone 6 cannot safely fire cone 10 clay. If you want flexibility, choose a kiln rated to cone 10 — it can also fire at lower cone ranges.
Most kilns in our catalog list both the maximum cone and the approximate max temperature in Fahrenheit so you can cross-reference easily.
A Note on Cone Numbers
Confusingly, cone numbers below zero are written with a leading zero (cone 06, cone 04) and these are lower temperatures than cone 1, 2, 3, etc. Cone 06 is cooler than cone 6. This trips up beginners constantly — just remember: the "0" cones are low fire.
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