Pottery Cones Explained: 06 vs 6 vs 10

Why is cone 06 cooler than cone 6? Here's the cone system in plain English — and the two rules that keep your clay, glaze, and kiln in agreement.

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Few things confuse new potters more than cone numbers. Why is cone 06 cooler than cone 6? Why do glazes, clay, and kilns all get labeled with them? Once the system clicks, buying and firing get a lot less intimidating. Here's the short version.

A cone measures heat work, not just temperature

A pyrometric cone is a small pyramid of ceramic material engineered to soften and bend when it has absorbed a specific amount of heat work — the combination of how hot the kiln got and how long it stayed there. That's why potters trust cones over a thermometer alone: two firings can hit the same peak temperature but do different amounts of work on the clay. The cone tells you the work actually got done.

The numbering that trips everyone up

Cones run in a sequence from coolest to hottest. The catch is that the low end uses a "0" prefix, and within those, a bigger number is cooler. So the order from coolest to hottest goes:

The takeaway: 06 is not the same as 6, and 06 is much cooler than 6. Once you pass 01, the prefix drops and bigger simply means hotter.

Cone	Approx. temperature	Typical use
06	~1830°F / 999°C	Bisque, low-fire glaze
04	~1940°F / 1060°C	Bisque, low-fire clay & glaze
6	~2230°F / 1222°C	Mid-fire glaze — the studio standard
10	~2345°F / 1285°C	High-fire stoneware & porcelain

Temperatures are approximate — the exact bending point shifts a little with how fast the kiln climbs.

What the ranges mean in practice

• Bisque firing (cone 06–04). The first firing that turns fragile greenware into durable, porous bisque ready to glaze.
• Mid-fire (cone 5–6). The most popular range for studios today — durable results, a huge glaze selection, and less energy than high-fire.
• High-fire (cone 9–10). Traditional stoneware and porcelain, prized for strength and classic surfaces, often in gas reduction.

Why this matters when you buy a kiln

Two rules save a lot of grief. First, match your clay, glaze, and firing to the same cone — a cone 6 glaze on cone 10 clay fired to cone 06 will disappoint. Second, buy a kiln rated a cone or two above what you fire. If you fire to cone 6, a kiln rated to cone 10 has headroom, so it isn't maxing out every firing — which means longer element life and more consistent results. A kiln that has to strain to reach your cone will wear out faster.