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Temperature measurement

The measurement of kiln temperature is of great importance. Usually one or more of four possible methods are used.

The potter can look through the spy hole and assess the colour of the interior of the kiln. This facility in judgement is much to be envied and really only comes with long years of experience. As a guide to this method, the following table may be useful:


Threshold of visible red 475°C
Lowest visible red to dark red 475 - 650°C
Dark red to cherry red 650 - 750°C
Cherry red to bright cherry red 750 - 800°C
Bright cherry red to orange 800 - 900°C
Orange to yellow 900-1100°C
Yellow to light yellow 1100-1300°C
Light yellow to white 1300-1550°C
White to dazzling white 1550°C and higher


Segar cones may by purchased from most stockists of ceramic supplies. They are small clay pyramids designed to melt at predetermined temperatures. A number is cast into the side of each cone indicating the temperature that it will bend to its "end point". Usually three different cones are placed, at an angle from the vertical, in a lump of clay and placed in a convenient position in the kiln. The temperature at any one time can be estimated by looking through the sight hole and observing which cones have started to bend and melt. At any one time, the kiln temperature will be higher than the bent cone but lower than ones still standing.


Cones should be set in a piece of clay at an angle of approximately 8° from the vertical.

012 840oC 1 1125
011 875 2 1135
010 890 3 1145
09 930 4 1165
08 945 5 1180
07 975 6 1190
06 1005 7 1210
05 1030 8 1225
04 1050 9 1250
03 1080 10 1260
02 1095 11 1285
01 1110 12 1310
    13 1350
    14 1390