Pyrometric cones measure heatwork — the combined effect of temperature and time — not temperature alone. That's why potters speak in cones: a cone "knows" whether your kiln crept up slowly or raced to peak. Here are the cones you'll use most, with their approximate temperatures.
Open KilnLog — log your cone results →The temperatures below are for a moderate heating rate of about 108 °F (60 °C) per hour over the final stretch (Orton large self-supporting cones). Slower or faster ramps shift these by 10–20 °F.
| Cone | Temp (°F) | Temp (°C) | Typical use |
|---|---|---|---|
| 06 | ~1830 | ~999 | Low bisque; earthenware glaze |
| 04 | ~1940 | ~1060 | Standard bisque; low-fire glaze |
| 5 | ~2167 | ~1186 | Mid-range glaze (low end) |
| 6 | ~2232 | ~1222 | Mid-range stoneware glaze |
| 10 | ~2345 | ~1285 | High-fire stoneware & porcelain |
Numbers are rounded approximations. Always check your specific cone manufacturer's chart for your firing speed.
Your kiln's thermocouple reads the air temperature at a single point and can drift with age. A cone, sitting next to your ware, bends when the clay and glaze have absorbed enough total heat to mature. Two firings that both "hit cone 6" can read different peak temperatures on the pyrometer if one held longer — and the cone is the honest record of what your pots actually experienced.
Match your glaze cone to your clay body's rated maturing range — firing a cone 6 glaze on a cone 10 clay (or vice versa) is a common cause of poor fit and dunting.
Note the "06 vs 6" trap that snares every beginner: cones with a zero in front (06, 04, 02) are the lower temperatures, and the higher the number after the zero, the cooler it is — so 06 is cooler than 04. Once you pass cone 1, bigger numbers mean hotter, so cone 10 is much hotter than cone 6. Witness cones come in self-supporting, large and small (bar) forms; large cones are the standard reference for the temperatures above, and small cones in a kiln-sitter bend at a slightly different rate.
A target cone and the cone your witness pack actually bent to are two different facts. Logging both — firing after firing — is how you learn your kiln's true behaviour and stop guessing.
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