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


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