Cones and firing temperature

A cone measures “heat work”, not just temperature

A glaze matures not only at a given temperature but according to how long and how fast it was heated. A pyrometric cone (e.g. Orton) measures exactly that: it bends when the kiln has done enough heat work.

That is why the same cone corresponds to different temperatures: with slow heating a glaze matures at a slightly lower temperature, with fast heating at a slightly higher one. The difference is usually 10–20°C.

That is why the Celadon site gives the cone first, and the temperature as approximate (approx.).

The cones in our catalogue

Cone	approx. °C	Range
010	890	Raku
07	980	Low fire
06	1000	Low fire
05	1050	Low fire
04	1060	Low fire
03	1100	Low fire
4	1190	Mid fire
6	1220	Mid fire
8	1260	Mid–high
10	1310	High fire

Temperatures are rounded from the Chrysanthos catalogue. Watch out: cone 06 (with a zero in front) is low fire, cone 6 is mid fire. The two are often confused.

How to choose a glaze

1. Find out what temperature your clay fires to. The glaze’s range must match the clay’s.
2. Check your kiln. The controller reading and the real heat do not always match — in a new kiln or on a new programme it is worth adding a witness cone.
3. Stay within the glaze’s range. “Cone 06–04” means the glaze matures properly anywhere between the two. Outside the range, colour, surface and food safety can change.
4. Test tile. Try a new glaze on a small tile first, on your clay and in your kiln.

Low, mid or high?

• Low fire (cone 07–03): most Tbilisi studios. Café Color, Café Color G, Superior Glaze, Low Sheen, Antique, Crackle, Fantasy.
• Mid fire (cone 4–8): High Fire Glaze, Matt Glaze H, Pastel Glaze H, Volcano, Supernova.
• High fire (up to cone 10): Stoneware Glaze, Stoneware Exotic.
• Wide range: most Underglaze and One Stroke colours withstand cone 06 to 10 — the exact range depends on the colour.