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Cone Temperature Chart    Buy Cones  More Cone Tips


The middle self-supporting cone is perfectly fired.  The left is over-fired, the right is under-fired.

For ceramics, kilns are not fired just to a temperature.  They are fired to a "cone" level, which accounts for time as well as temperature.  Think of it as heat absorption rather than just temperature.

Cone's come in different numbers, each of which corresponds to a heating-rate/temperature-combination which will make that cone deform.  At the beginning of the firing the cone is standing at an 8 degree angle.  A perfectly fire cone will be bent to a 90 degree angle.  If the cone is bent less, the kiln was under fired.  If the cone is bent more, the kiln was over fired.

Notice the way the cones are numbered.  The hottest is 10, going downward to 1.  Then as it continues to getting cooler it continues at 01, 02, etc.  So there is a BIG difference between cone 5 and cone 05!

Cone number Orton Cones
Final temp  in degrees F at ramp rate of 27 degrees F/hr
Orton Cones
Final temp  in degrees F at ramp rate of 108 degrees F/hr
Orton Cones
Final temp  in degrees F at ramp rate of 270 degrees F/hr
Type of work done at these temps In standard firing, cones of the correct number are placed around the kiln and are watched.  When the cones fall the kiln is turned off.  This works the same for gas and electric kilns.

Electric kilns with electronic controllers (such as the Skutt KilnMaster series) have a thermocouple which continuously measures the temperature, records it over time, and shuts off the kiln when the appropriate heat absorption has been met.  So if the ramping temperature is fast, the kiln will go to a higher temperature before it turns off than if the ramping temperature is slow (thus allowing the clay to absorb more heat along the way.)  The final temperature is most affected by the rate of temperature increase over the last 300 to 400 degrees of firing.

Note:  Think of the 0 in a cone number as meaning "minus".  So 06 is much cooler than 6 because it is like a "minus 6".

 

Typcically it takes 15-25 minutes for a cone to bend once it starts.  This depends on the cone number.  The cone bends slowly at first but once it reaches the half way point it bends quickly.  When the cone tip reaches a point level with the base, it is considered properly fired.  

If a cone is soaked at a temperature near its equivalent temperature, it will continue to mature, form glass and bend. The time for the cone to bend depends on several factors and as a general rule, a 1 to 2 hour soak is sufficient to deform the next higher cone number. A soak of 4 to 6 hours will be required to deform two higher (hotter) cones.

 

 

 

10 2284 2345 2381 High Fire Ceramics
9 2235 2300 2336
8 2212 2273 2320
7 2194 2262 2295 Mid Fire Ceramics (Cone 5-6 most common)
6 2165 2232 2269
5 2118 2167 2205
4 2086 2142 2161
3 2039 2106 2138
2 2034 2088 2127
1 2028 2079 2109 Low Fire Ceramics (06-04 most common)
01 1999 2046 2080
02 1972 2016 2052
03 1960 1987 2019
04 1915 1945 1971
05 1870 1888 1911
06 1798 1828 1855
07 1764 1789 1809
08 1692 1728 1753
09 1665 1688 1706
010 1636 1657 1679 Glass Firing
011 1575 1607 1641
012 1549 1582 1620
013 1485 1539 1582
014 1395 1485 1540
015 1382 1456 1504
016 1368 1422 1465
017 1301 1360 1405 Overglaze / China Painting
018 1267 1319 1353
019 1213 1252 1283
020 1159 1180
021 1112 1143
022 1087 1094
 

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