by Janet Alexander
Testing can be done by using a pyrometer (which is how I used to adjust my kiln’s temperature before there were controllers) or by using kiln pyrometric cones. The pyrometric cones are supposed to bend when heated to a specific temperature for a certain amount of time. That means that pyrometric cones give a temperature equivalent; they are not simple temperature-measuring devices. According to a pyrometric cone manufacturer, cones have over 20 variables that can affect the cone’s bending, including the cone's composition, particle size of raw materials, type of forming process, moisture during forming, density of the cone, geometry of the cone, setting height, and angle and the heating rate. Atmosphere also affects bending behavior. Wow, that’s a lot of variables! So, let’s look at testing with a pyrometer or a kiln test kit.
I used the kiln test kit sold by the PMC Connection. According to experts, the average kiln controller is accurate to ±10°F (±5.5°C) so keep this in mind while testing. Additionally, run the test several times but move the thermocouple to different areas of your kiln. Place it towards the back, near the front, off to each side, and etc. Test at different temperatures. I conducted tests at 1110˚F, 1200˚F, 1290˚F, 1470˚F, 1560˚F, and 1650˚F. I found that both readouts were within a few degrees of each other until the temperature got up to 1650˚F. Then they were off by 10˚F! So, I added another thermocouple from my casting kiln. All three read different degrees but were within the accuracy range.
Now I know why my PMC3 clay had a crystalline look to it when I fired it at 1650˚F; it was getting too hot! So, now I lower the temperature of my kiln by a few degrees when setting it at 1650˚F.
The Test Kit Includes:
- Sensor reader (tester)
- 9V Battery
- K-type thermocouple TP-02A
- K-type thermocouple TP-03
Caution: Don’t insert it past larger ceramic end or the wires will burn!
The sensor reader can read in Fahrenheit (F) or Centigrade (C). Turn it on by sliding the button from the center (off position) to the F (if measuring in Fahrenheit).