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Pyrometric Cones and Kiln Temperature Ranges

peephole To vitrify clay – to change it from clay to stone – it must be heated to a glowing state called incandescence. Many kiln users today rely on their electronic and digital kiln controls, but long before the advent of those conveniences potters learned to measure the temperature inside the kiln by placing small numbered cones in the kiln before firing. Each numbered cone deforms at its own specific temperature, and so the temperature inside the kiln can be determined by seeing which cones deform and when by looking into the inferno through a 1" peep hole like the one in the photo! Although fewer and fewer potters use cones today, the cone number terminology is a popular and convenient shorthand for describing kiln temperatures.
Temperatures shown below encompass only the range commonly used for the substances mentioned in the chart. In fact, cone numbers do continue all the way to 42, an Orton cone that deforms at 3600°F.

Cone
#
Temp
°F
Temp
°C
Incandescence Range   Substance Details
14 2525 1390 Brilliant White High-Fire   P
o
r
c
e
l
a
i
n
End Porcelain
13 2460 1350 Brilliant White High-Fire Porcelain
12 2375 1310 White High-Fire Porcelain
11 2340 1285 White High-Fire S
t
o
n
e
Porcelain,
End High-Fire Stoneware
10 2300 1260 White High-Fire High-Fire Stoneware,
Begin Porcelain (definition)
9 2280 1250 White High-Fire   High-Fire Stoneware
8 2240 1225 White High-Fire Begin High-Fire Stoneware
7 2210 1210 Yellow-White Mid-Fire w
a
r
e
End Mid-Fire Stoneware
6 2175 1190 Yellow-White Mid-Fire Mid-Fire Stoneware
5 2160 1180 Yellow-White Mid-Fire Mid-Fire Stoneware
4 2130 1165 Yellow Mid-Fire E
a
r
t
h
e
n
End Earthenware
3 2095 1145 Yellow Lower
Mid-Fire
Earthenware
2 2080 1135 Yellow Lower
Mid-Fire
Begin Mid-Fire Stoneware (definition)
Earthenware
1 2060 1125 Yellow Lower
Mid-Fire
  Earthenware
There is no "0" (zero) cone.     The "0" prefixes on the cone numbers below are like a minus sign.
01 2030 1110 Yellow Lower
Mid-Fire
  w
a
r
e
Earthenware
02 2000 1095 Yellow-Orange Low-Fire   Earthenware
Glass begins to form within the clay
03 1980 1080 Yellow-Orange Low-Fire   Earthenware
04 1920 1050 Yellow-Orange Low-Fire B
i
s
q
u
e
Earthenware,
End Bisque Firing
05 1880 1030 Orange Low-Fire Earthenware
Bisque Firing
06 1840 1005 Orange Low-Fire Bisque Firing
Begin Earthenware (definition)
07 1785 975 Orange Low-Fire   Bisque Firing
08 1735 945 Red-Orange Low-Fire Begin Bisque Firing
09 1705 930 Red-Orange Low-Fire    
010 1635 890 Red-Orange Low-Fire

W
a
r
m

G
l
a
s
s

End Warm Glass
011 1605 875 Red-Orange Low-Fire Warm Glass
012 1545 840 Red-Orange Low-Fire Warm Glass
End Fuming
013 1485 805 Cherry Red Very
Low-Fire
Warm Glass
FumingEnd Carbon, Burn Out
014 1395 760 Cherry Red Very
Low-Fire
Begin Warm Glass (Slumping & Fusing)
Carbon Burn Out, Fuming
015 1380 750 Cherry Red Very
Low-Fire
  Carbon Burn Out, Fuming
016 1370 740 Dull Red Very
Low-Fire
O
v
e
r
g
l
a
z
e
End Overglaze
Carbon Burn Out, Fuming
017 1330 705 Dull Red Very
Low-Fire
Overglaze, Fuming, Carbon Burn Out
End Water Smoking
018 1260 680 Dull Red Very
Low-Fire
Overglaze
Fuming, Carbon Burn Out & Water Smoking
019 1225 660 Dull Red Very
Low-Fire
Overglaze
Fuming, Carbon Burn Out & Water Smoking
020 1159 625 Dull Dark Red Very
Low-Fire
Overglaze
Fuming, Carbon Burn Out & Water Smoking
021 1110 600 Dull Dark Red Very
Low-Fire
Overglaze
Fuming, Carbon Burn Out & Water Smoking
022 1085°
F
590°
C
Dull Dark Red Very
Low-Fire
Begin Overglaze (China Paints, Decals)
Fuming, Carbon Burn Out & Water Smoking**
are already in progress at this temperature
Cone 022 marks the lowest kiln temperature at which incandescence of the ceramics is visible. ** The early stage stage of bisque-firing or single-firing, below 1200°F, when carbonates, nitrates, sulfates, organic contaminants, and chemically combined water volatize and outgas.
 

Chart conceived, designed, and written by David Gordon
Copyright © 2010 David Gordon. All Rights Reserved

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