Kiln Calibration

[Diane Puckett]

I have an L&L Easy Fire 23T with 3" brick. A glaze firing about 2 weeks ago was set for fast glaze cone 6 with a 15 minute hold and controlled cool. Cone 7 was more than touching. Last night, with a similar load of pots, I ran it at fast glaze cone 5 with a 15 minute hold and controlled cool. Cone 5 was just touching. I anticipated cone 6 being down, but it barely moved. This is so confusing. Does anyone ever really get their kiln calibrated to temperature, or is that just a fantasy? Does it even matter as long as the glazes look okay and the kiln reaches an acceptable cone? I understand the difference between heat work and temperature, but this whole lack of calibration is annoying. For what it is worth, I did take the Kiln Goddess out of the window and sit her on top of the kiln last night, so perhaps she is just messing with me.

[Frederik-W]

Apologies for telling you things you might know already, but this is the way I understand it:

 

For calibrating we usually need to get some correlation between your controller settings and what results you actually get with cones.

The thermometer/thermocouple is the only sensor that provides feedback to the controller. So the electric controller switches the element on and off to maintain a pre-programmed temperature or rate/ramp (degrees/hr) based only on the temp feedback.

It does not directly measure heat work (as with cones). It can do some calculations, based on temp & time, to calculate the approximate heat work or cone, but I'm not sure if yours does.

To check the kiln you manually calculate the cone results based on what the ramp/rate is during e.g. the last 15mins of approaching the set temperature.

To help with this get a temperature datalogger to measure & log the temperatures you get during firing.

(You will need to insert its probe into the kiln somewhere).

There are tables that tell you what the cone results should be for certain final rates.

e.g. if you approach final temp slowly (or with a soak period) you will get a higher temp cone and if you approach it fast a lower temp cone.

Your calculation should match more or less what you get, unless your temperature probe is wrong. (Or it measures some part of the kiln which is not representative)

As you will know there are other things that can influence your results, e.g. the size of the load (because it will be slower to heat) and the temperature differences between top/bottom, also if you have bung holes open or closed.

 

PS:

I have checked the adverts for your "DynaTrol" controller and it seems to do some calculations for heat-work:

"Electronic Control Matches Pyrometric Cone Performance"

"This feature..[patented].. adjusts the final temperature reached in an Easy-Fire profile based on the speed of the actual firing.

It results in accurate automatic control of heat-work in ceramic firing".

So if this is so good, I wonder why do you not get accurate results ?

[Claypple]

I have an L&L Easy Fire 23T with 3" brick. A glaze firing about 2 weeks ago was set for fast glaze cone 6 with a 15 minute hold and controlled cool. Cone 7 was more than touching. Last night, with a similar load of pots, I ran it at fast glaze cone 5 with a 15 minute hold and controlled cool. Cone 5 was just touching. I anticipated cone 6 being down, but it barely moved. This is so confusing. Does anyone ever really get their kiln calibrated to temperature, or is that just a fantasy? Does it even matter as long as the glazes look okay and the kiln reaches an acceptable cone? I understand the difference between heat work and temperature, but this whole lack of calibration is annoying. For what it is worth, I did take the Kiln Goddess out of the window and sit her on top of the kiln last night, so perhaps she is just messing with me.

 

 

1) How old is your kiln? How many firing have you done so far?

2) When you started it, did you check "Review Prog"? It shows you what temperature it is going to fire to.

[perkolator]

how are you programming the kiln? with "Cone Fire" or manually programmed? If it's Cone Fire and the temps are off, I cannot help here since I never use it -- but if you're firing manually, simply do a few firings with cones inside to get an idea of how your kiln acts when set to a specific temp, with a specific type of work...then simply adjust your temps accordingly. For example, a ^04 firing set at 1941* only gets a ^04 to be barely tipping, then you know you need to set your temp slightly higher (like maybe 1955*) -- of course all this truly depends on what type of work/quantity/volume inside the kiln since the heat work will change depending on the stack. Good luck!

[neilestrick]

I have found that the same hold time doesn't always give the same results at all cones. 15 minutes won't always give one more cone. It could also be that cone 5 or cone 6 is not calibrated.