Melted large Orton pyrometric cones 5, 6 and 7. Cone pack is pictured after being removed from the kiln.
Pyrometric cones are designed to melt at certain temperatures in a kiln. They measure “heat work” during a firing, or time plus temperature. A digital pyrometer can give an accurate temperature, but pyrometric cones are useful for determining how the firing went for your ceramic ware, and they can be useful for noting if you have different temperature zones in your kiln. The rate of the firing, or the speed at which the temperature climbs per hour, can determine when the cone bends.
Generally, a cone accurately measures the temperature when it has bent to approximately “9pm” on the left side.
Pyrometric cones can be purchased at ceramic suppliers, or in the US shop Orton Cones at Blick.
Most kilns now have temperature sensors, but you can also purchase high-temperature thermocouple sensors that can be moved from kiln to kiln. Shop High Temperature thermocouple at Amazon.
Below is a chart of temperature equivalents for cones. This chart is for large cones, and the temperature rate measures the last 90 to 120 minutes of firing.
Orton Pyrometric Cone Chart in Fahrenheit and Celsius
| Cone number | 60°C/hour | 108°F/hour | 150°C/hour | 270°F/hour |
|---|---|---|---|---|
| 019 | 676°C | 1249°F | 693°C | 1279°F |
| 018 | 712°C | 1314°F | 732°C | 1350°F |
| 017 | 736°C | 1357°F | 761°C | 1402°F |
| 016 | 769°C | 1416°F | 794°C | 1461°F |
| 015 | 788°C | 1450°F | 816°C | 1501°F |
| 014 | 807°C | 1485°F | 836°C | 1537°F |
| 013 | 837°C | 1539°F | 859°C | 1578°F |
| 012 | 858°C | 1576°F | 880°C | 1616°F |
| 011 | 873°C | 1603°F | 892°C | 1638°F |
| 010 | 898°C | 1648°F | 913°C | 1675°F |
| 09 | 917°C | 1683°F | 928°C | 1702°F |
| 08 | 942°C | 1728°F | 954°C | 1749°F |
| 07 | 973°C | 1783°F | 985°C | 1805°F |
| 06 | 995°C | 1823°F | 1011°C | 1852°F |
| 05 | 1030°C | 1886°F | 1046°C | 1915°F |
| 04 | 1060°C | 1940°F | 1070°C | 1958°F |
| 03 | 1086°C | 1987°F | 1101°C | 2014°F |
| 02 | 1101°C | 2014°F | 1120°C | 2048°F |
| 01 | 1117°C | 2043°F | 1137°C | 2079°F |
| 1 | 1136°C | 2077°F | 1154°C | 2109°F |
| 2 | 1142°C | 2088°F | 1162°C | 2124°F |
| 3 | 1152°C | 2106°F | 1168°C | 2134°F |
| 4 | 1160°C | 2120°F | 1181°C | 2158°F |
| 5 | 1184°C | 2163°F | 1205°C | 2201°F |
| 6 | 1220°C | 2228°F | 1241°C | 2266°F |
| 7 | 1237°C | 2259°F | 1255°C | 2291°F |
| 8 | 1247°C | 2277°F | 1269°C | 2316°F |
| 9 | 1257°C | 2295°F | 1278°C | 2332°F |
| 10 | 1282°C | 2340°F | 1303°C | 2377°F |
| 11 | 1293°C | 2359°F | 1312°C | 2394°F |
| 12 | 1304°C | 2379°F | 1324°C | 2415°F |
