Firing Chart

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Pyrometric Cone Chart (Orton Standard)

When heated at 150 degrees Centigrade / hour

Cone Number	Centigrade	Cone Number	Centigrade
022	600	04 Low Fire	1060
021	614	03 1/2 Low Fire	1080
020	635	03 Low Fire	1101
019	683	02 Low Fire	1120
018	717	01 Low Fire	1137
017	747	1 Low Fire	1154
016	792	2 Low Fire	1162
015	804	3 Low Fire	1168
014	838	4 Mid Fire	1186
013	852	5 Mid Fire	1196
012	884	6 Mid Fire	1222
011	894	7 Mid Fire	1240
010	900	8 High Fire	1263
09	923	9 High Fire	1280
08 Low Fire	955	10 High Fire	1305
07 Low Fire	984	11 High Fire	1315
06 Low Fire	999	12 Some Porcelain	1326
05 Low Fire	1046	13 Some Porcelain	1346

Orton makes cones from cone 022 up to cone 42. Cone 022 is the lowest melting cone and requires the least amount of heat to deform or bend. During firing, a cone softens and melts as it is heated. Cones used on the kiln shelf bend due to the effects of gravity pulling the tip down. This bending indicates the cone and the ware have received a specific amount of heat. It typically takes 15 to 22 minutes for cones to bend fully once they start bending. Each higher cone number requires more heat to bend. A cone 01 needs less heat treatment than cone 1 and cone 020 needs less than 019.

It is important not to confuse the lower maturing cones and bars, whose numbers begin with an 0, with the higher cones and bars not containing this prefix.

Although cones do not actually measure temperature, cone bending behavior and temperature are related. Generally, the faster the firing, the higher the temperature required to bend the cone and the slower the firing, the lower the temperature required to bend the cone. The 6 o'clock position (90 angular degrees) is considered the end point of cone bending.

Typical uses for cone numbers are as follows:

NUMBER: 022 TO 011 - Used in firing of overglaze decorations, lusters, enamels, and decals and for glass fusing, slumping, and decorating. The temperature equivalent range is approximately 560 to 850C.

NUMBER: 010 TO 3 - Made as a regular series (red, iron-containing cones) and as an Iron Free series for use in reducing atmospheres. These cones are used in the firing of craft and art bodies, for wall tile, glazes, and some structural clay products. The temperature equivalent range is approximately 890 to 1170C.

NUMBER: 4 TO 12 - Used in firing porcelain, floor tile, china, stoneware, structural clay products and some refractory materials. The temperature equivalent range is approximately 1180 to 1340C.

NUMBER: 13 TO 42 - Used for firing industrial products up to 2015C.

Reference: Sheffied Pottery