Clay Sculpture Firing Schedules and Orton Cone Chart

Note - When purchasing clay or glaze, check the temperature requirements and make sure your kiln will fire them correctly, and that its temperature range is compatible with the clay you are using. Always test fire clay/glaze combinations using small test tiles before using glaze on artworks.

Pyrometric Cone Chart (Orton Standard)

When heated at 150 degrees C/hour

Cone No.	Centigrade	Fahrenheit		Cone No.	Centigrade	Fahrenheit
022	600	1112		04	1060	1940
021	614	1137		03 1/2	1080	1976
020	635	1175		03	1101	2014
019	683	1261		02	1120	2048
018	717	1322		01	1137	2079
017	747	1376		1	1154	2109
016	792	1457		2	1162	2124
015	804	1479		3	1168	2134
014	838	1540		4	1186	2167
013	852	1565		5	1196	2185
012	884	1623		6	1222	2232
011	894	1641		7	1240	2264
010	900	1652		8	1263	2305
09	923	1693		9	1280	2336
08	955	1751		10	1305	2381
07	984	1803		11	1315	2399
06	999	1830		12	1326	2419
05	1046	1914		13	1346	2455
	Low-Fire	Mid-Fire		High-Fire	Some Porcelain
	Earthenware	Stoneware		Kaolin (China Clay)

Firing Schedule #1 - Digital Kilns: This Schedule can be followed for kilns with a temperature gauge and timer:

1. 80 degrees an hour to 180; hold for 3-4 hours - this step is critical to keep the clay from exploding once you begin to raise the temperature.
2. 150 degrees an hour to 500; hold for ten minutes.
3. 200 degrees an hour to 1000; hold for ten minutes.
4. 300 degrees an hour to the desired temperature is reached; end of firing.

Firing Schedule #2 - Kiln Sitters: My kiln is an old Gare model kiln with a model K kiln sitter. My method for firing is as follows:

Note - this kiln has an extra ring with its own element (the top section with the extra switch). While this is great for enlarging the firing chamber to fit more artworks, it reduces the firing temperature from cone 10 to cone 8. The first step before firing the sculpture in the kiln is to warm the sculpture to approximately 120 to 200 degrees F to remove all of the water from the clay. The sculpture is placed in a drybox (little or no humidity) consisting of a small heater or several light bulbs (about 15-20 100 watt bulbs) for about 3-5 days. This step is critical to keep the clay from exploding once it is put in the kiln. The sculpture is then placed in the kiln. The bottom switch is turned on with all peep holes open and the lid propped up for two hours.

The next higher switch is turned on and left for an hour. The next higher switch is turned on, the lid closed, and the bottom peep hole is closed. The top peep hole is left open to circulate air properly throughout the kiln and help protect the metal portions (thermocouple, elements, etc) from gasses that can damage them. This is especially important for reduction-type firing,which is caused by a lack of oxygen in the kiln chamber. When firing a sculpture that still has newspaper in it, it is a reduction firing because the burning paper reduces the amount of oxygen in the chamber. The next 3 switches are turned on consecutively each hour until the kiln automatically shuts off. The kiln is left overnight to cool before the lid or peep holes are opened. Opening the kiln too quickly will crack or break the sculptures due to stress from quick temperature changes.

--Orton Cone Charts & Instructions for Firing--

--Before Buying a Kiln--
--Buying a New Kiln--
--Buying / Repairing a Used Kiln--

Clay Pendants & Jewelry by Jen (Coming Soon)

--Reference Materials--

--Clay Medium--
--Clay Finishes--
--Clay Timeline--

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