How to Down-Fire a Kiln Sitter Equipped Manual Kiln

[George Lewter]

Just because your kiln sitter trips your kiln off, you don't have to crash cool your load of pottery. You can override the kiln sitter, turn the kiln back on, and control the soak and cooling just about as finely as you could want to. It does require a pyrometer and thermocouple to track your progress. You will need to learn to use your kiln dial controls to find balanced settings to hold a temperature in several ranges, and to slowly cool through some limited ranges, as well. The skills are not at all hard to acquire, but you will need to be prepared to check your kiln and make small adjustments every ten to thirty minutes for about four hours at the end of your glaze firing, depending on the cooling schedule you want to follow.

Getting to Know your Kiln Sitter

When your cone softens and releases the sitter's trip arm, the arm swings down in an arc. At the bottom of the arc a small projection near the arm's pivot hits a switch that turns the kiln off. The falling arm has enough force to trip the switch, but just the weight of the arm, if it is not moving, does not exert enough force to trip the switch. We can use this fact to reset the switch "ON" and continue firing the kiln. If you want to do a soak at the temperature where the cone softened, it is necessary to be right there when the kiln sitter trips.

As you see at the right, the trip arm can be lifted upward about 45 degrees, releasing the switch. Now you can push the white power button in, and it will remain depressed with the power ON again. Gently lower the trip arm until the trip lever rests lightly on the recessed switch, without tripping it and shutting the kiln off again.

Most likely your kiln has been at or near it's maximum power level to achive the target cone temperature. If you want to do a soak at this temperature you will have to back off on the power dial(s) until the temperature stops climbing and starts decreasing. Simply adjust up and down in small increments while watching your pyrometer until you are maintaining a steady temperature. It may not be possible to totally stop the rise or fall of the temperature using the dials . . . . You may have to allow a slight rise for a few minutes and adjust for a slight temperature fall for the next few minutes. In other words you may have to hover around your desired temperature rather that resting absolutely on it.

After the soak you may want a controlled temperature descent in certain temperature ranges to develop matte surfaces, variegated surfaces, or to encourage crystal growth in the glaze matrix. You can by adjusting your power level dials, hold and do slow descents through any temperature range. Remember to keep an eye on the maximum time dial, lest it turn your kiln totally off at some unexpected time.

Keep a log of your firings including times, temperatures, rate of temperature change, and dial settings at each kiln check, and you will be able to get tight control over your kiln.

Good luck and good firings!

[Renee Arthur]

If you get a chance could you look at my post in this same category?  It's very similar to this topic but with a different type of kiln/kiln controls.

Thanks so much,

Renee Arthur