Why does my kiln seem like it underfires the pottery?

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Why does my kiln seem like it underfires the pottery?

If your kiln underfires with no error code:

  1. Cones placed wrongly in cone pack- angle is off.
  2. Small or wrong cones used
  3. Fired to the wrong cone
  4. Firing a Vary Fire program to too low a temp for the rate of climb
  5. TC offset adjustment needs to be set lower
  6. Kiln-sitter (if used) out of adjustment
  7. Kiln-sitter (if used) blobs the cone instead of bends it- replace kiln-sitter tube
  8. Lid/ Hinge out of adjustment- opens a bit in the front when hot.

Additional Actions to Take

  1. Make sure you have programmed the kiln properly and it is supposed to be firing.
  2. Read the Operation instructions.
  3. Do a Program Review as soon as you start firing. (For DynaTrols - see this video)
  1. On the next firing make up "cone packs" for each thermocouple.
  2. Once the cone packs are positioned on shelves and are visible through the peepholes, fire the kiln to the middle cone's number
  3. Start watching cones near the end of firing.
  4. Keep checking the control display to make sure it does not say CPLt.
  5. If the middle cones did not go down together then immediately note the differences in each thermocouple reading from the one thermocouple the same zone as the first cone that went down. Change the final set point of your program to reflect the difference.
  6. If the kiln is firing too hot then lower the final set point.
  7. If the kiln shut itself off before bending the cones properly, reprogram it and then restart it as quickly as possible. Record the temperature at which the kiln shut down. Stop and restart the kiln. Reprogram the same program to one cone number higher. Do these steps quickly. Watch the middle cones again and note at what temperature the cones properly bend. If they bent while you were programming then just offset the temperature by 5 or 6 degrees. Shut the kiln off once you note that temperature.

Use cone packs in all sections (top, center, bottom) of the kiln and keep records of what happens.

  1. Carefully examine thermocouple tip. This is the exposed welded joint at the end of the thermocouple that is not covered up by the ceramic tube.
  2. To do this you will have to remove the thermocouple from its protection tube (if it is a kiln that has one of our protection tubes). You can do this with the kiln disconnected from power.
  3. Look for corrosion - especially if it severe. These thermocouple tips will oxidize and otherwise corrode over time. That is normal. There is some point, however, at which the corrosion affects the ability of the tip to work (thermocouples work by generating a small voltage at the tip caused by two different metals reacting to each other).
  4. Corroded thermocouple tip

  5. Make sure the two wires are securely joined. One of the things that can cause an intermittent problem is a bad weld. If the two wires touch each other (even if they are not welded) they may work temporarily. However, if the weld is not secure then the wires could separate when the kiln heats up and cause an intermittent failure.
  6. If the thermocouple tip looks healthy then test the control board.

Fix lid seal if a bright red glow is visible around the seal when kiln is operating and/or excessive heat loss can be felt around seal.

  1. Rub seal high points down with sandpaper until no more than 1/16 of an inch gap is found at any point along seal.
  2. Check for unevenness in the gap that will cause an excessive heat loss.
  3. Replace lid if it is excessively cracked or worn or has holes in it. Replace lid.
  1. If uneven firing occurs persistently, distribute your load weight more evenly throughout the kiln or to match the firing characteristics of the kiln.
  2. If elements typically fire hot at the top of the kiln put more weight in the top to absorb that heat, and vice versa.
  3. The bottom shelf should be at least 1/2" to 1" above the floor of the kiln.
  4. Badly distributed load weight can also affect the firing rate of the kiln and lead to Error 1.

TIP: The longer square posts can be laid down on their sides to get a perfect amount of space under the bottom shelf.