Firing an electric kiln with a kilnsitter

Before you use you kiln, the first thing you will need to do is adjust your sensing rod in the kiln sitter. Here are some simple adjustment checks for you to make before firing your kiln. Please note you should check this adjustment approximately every 30 firings.

1. TURN ALL SWITCHES OFF
2. INSTALL FIRING GAUGE
3. CHECK POSITION OF RELEASE CLAW AND WEIGHT TRIGGER
    a. With the firing gauge in place, swing the weight up against the guide plate. Pull the claw forward (against the slight play in the swivel/pivot assembly) and check for 1/16 th inch clearance between the inside tip of the claw and the face of the trigger as shown in Figure 2. The set screw on top of the claw should be loosened if the claw position needs to be adjusted. Retighten the set screw.

A new kiln is shipped with the firing gauge in place. Be sure to keep in a safe spot so you can reset the claw as necessary. NEVER FIRE THE KILN WITH THE FIRING GAUGE IN PLACE! If it has been removed, it should now be replaced over the sensing rod and cone supports, see Fig. 1.
   b. When the weight swings forward, the trigger should just clear the tip of the claw, as shown in Fig. 3.

The setscrew in front of the weight is used to raise or lower the trigger, as shown in Fig. 4. The setscrew must be firmly tightened or the force of repeated falling of the weight may cause the trigger to creep out of adjustment.

 4. MAKE SURE THE KILN IS LEVEL. Irregular floors can cause the kiln to be pitched out of level. An unlevel kiln will cause the kilnsitter to malfunction. The kiln must be used on a stand or on top of firebricks. The high heat required to fire porcelain means it must be kept away from combustibles.
5. CHECK THE TRAVEL OF THE SENSING ROD The firing gauge
 shown now be removed. The sensing rod is now free to travel vertically
 within the tube cavity. It should travel freely in the center of the cavity without touching the
 sides at any point, as shown
in Figures 5 and 6


6. IF NECESSARY, the sensing rod may be centered by loosening the two guide plate screws in front of the kilnsitter and moving the guide plate right or left as required, as shown in Figure 7. Be sure the guide plate screws are firmly tightened.

7. BEFORE YOUR FIRST TEST FIRE you will need to kiln wash your shelves as well as the cone supports. Kiln wash can be bought in either a dry form or premixed as a liquid. If using dry mix with a small amount of water and paint a thin coat on the kiln supports and the sensing rod. Allow to completely dry before running the kiln. This will keep cones from sticking during firing, causing an over fire. This step needs to be done before each firing. This should be done lightly; you do not want the kiln wash to accumulate. I kiln wash the shelves just once, mainly since I only fire porcelain. If I was doing glazes, I would have to keep the shelves well coated with kiln wash.
8. NEXT, YOU WILL LOAD the kiln furniture (shelves and posts) in your kiln. Start with either short ½” or 1” posts and place three or four of these on the bottom of your kiln floor. Now place a shelf on top of these posts. If your kiln is large enough you may place three or four more posts on top of the first shelf, then add your 2 nd shelf. Keep a 1” clearance from the top of the kiln.
9. TURN ALL SWITCHES OFF.
10. ON THE OUTSIDE of the kilnsitter raise the weight up against the guide plate. Use your thumb to bring down the claw and hold in place while reaching in to insert the cone between the cone supports and the sensing rod.

The diagrams show a wedge cone. There are also straight bar cones. I prefer the wedge as I can place it on the cone supports so the sensor rod is on a narrower section to slightly lower the temperature if needed.
11. THE LIMIT TIMER is used during the test firing. Turn the timer knob clockwise to number 1 ½ or 2 on the scale. Note if you are test firing to make sure that your kiln reaches a certain cone number, turn the limit timer as far as it will go and make a note of when the kilnsitter goes off. In the future 15 minutes past that time is what you should set your limit timer to prevent over firing. Note not all manual kilns will actually have a limit timer. If your kiln does feature a limit timer you have to use it, as the kiln will not turn on if you have it set to zero.
12. INSET A FINGER into the hole in the weight on the front of the kiln center and press firmly to engage the plunger until you hear it lock.
13. AS A PRACTICE RUN, I believe you should start as you mean to go on! I take a very small stilt or shelf support and prop the lid open before turning the kiln on low. If I actually had items inside the kiln, this would allow moisture to escape from the clay bodies. Even if you own a small kiln, you should prop the lid open for at least the first hour. After one hour I turn the switch to medium and leave it on medium for two hours. Next I will turn it to high until the kilnsitter automatically turns it off. Never leave your kiln running unattended.
14. ALLOW THE KILN to cool completely before opening. This usually takes the same number of hours that it took for your kiln to fire a load. Now it is time to inspect the bent cone in the kilnsitter to make sure you have adjusted all the mechanisms correctly.

In figure 9 you will see that the cone has been bent almost at a 90° angle, this is the correct bend. However if the cone is tightly folded as shown in the overfired illustration, you will need to slow down the rate at which your kiln reaches the cone temperature. Just leave it on low for an extra half-hour, and on medium for a next to our before turning it to high. The opposite problem is under firing in which the cone just barely slumps enough to trigger the kilnsitter. In this case I would try readjusting the weight on the front of the kilnsitter so that the claw has a little bit less clearance. This will result in the cone having to bend in the more correct position before triggering the kiln to turn off. I always run a test fire when I get a new kiln or if I have just replaced the elements in an older kiln. In both of these instances the kiln will run a trifle hot as the elements are at their peak efficiency. So the ramping up time may very well be needed to be slowed down by running the kiln longer at low and medium before turning to high.