How to Down-Fire a Manual Kiln with a Dawson Kiln Sitter

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.

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 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!

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Comment by john autry on November 14, 2013 at 9:19am

Most glaze recipes that I find nowadays, include info on "holding". WILL most recipes work without the complexities of non-linear firing? I have a kiln with a kiln sitter, no pyrometer and thermocouple  at this point. Today's formulas have me a bit confused. What are the risks of firing "programmable" formulas  in a non-programmable kiln, when you are not there to monitor the progress? thanks, john

Comment by Trevor Sansom on December 8, 2011 at 2:56pm

My electricity provider has recently supplied an energy monitor which on a cigarette packet sized display unit shows the amount of power being used in the household. As my kiln is in a shed at the end of my garden the chance to monitor it from my armchair is most welcome.

For a bisque firing I fire as normal until 600 deg C and then set my kiln controller to maximum power ,the thermostat to 1040 deg C and set controller to CUT OFF. By checking the power consumption it is quite obvious when the kiln cuts-off. I can then go and turn the mains supply off to the shed at my convenience.

Glaze firing is further enhanced. As usual to 600 deg C. Max power, 1235 deg C but set to SOAK. The power consumption now needs to be monitored with a little more dillegence. Once 1235 is reached the power fluctuates up and down as the thermostat cycles to soak. I leave soaking for 30 to 40 minutes. Into shed reset thermostat to 1040 deg C and return to armchair. When kiln temp down to 1040 deg C power consumption will shoot up to maintain the soak. After 40 minutes at 1040 I revisit the shed and switch off kiln.

This not only allows me to stay indoors on wet and cold winter evening but enables me to detect when the soak temperatures are reached with much greater accuracy.I hope that this may be useful to others and would be interested if others can see ways of using the monitor more effectively.

Trevor Sansom

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