Witness Cones always indicate one cone hotter than Bartlett Controller V6-CF

Has anyone compared their computerized Kiln Controller and thermocouple cone with Witness Cones?

Witness Cones in our computer-controlled kiln always indicate the firing is exactly one cone higher than what we program into the kiln controller, regardless of what cone we choose. This is without the addition of a hold at the peak temperature or a slow-cool. Is this a design error or a longstanding potter's tradition I'm not familiar with?

We first noticed this when we bought the Cress-R23 kiln two years ago. This kiln uses a slightly customized V6-CF Bartlett computerized Kiln Controller. A Witness Cone placed next to the open peephole fires close to the cone we had programmed, as it must be cooler there. But a Witness Cone placed anywhere else in the kiln is exactly one cone higher than expected.

We spoke to Cress and to Bartlett. Art Maldanato, the engineer at Cress, said this is "normal" while Bartlett techs were mystified. I asked them if this could be an "look-up indexing error" in the EPROM program, but they said their EPROM program doesn't use a look-up index. Bartlett said they have an newer version of the software they could flash our EPROM with if we send them the controller card.

It's not hard to work around. We choose ^05 to fire bisque, ^07 for low-fire, and ^5 to fire a Cone 6.

Has anyone else compared their computerized Kiln Controller and thermocouple with Witness Cones. Is this actually the normal way kilns work?

We have a thermocouple temperature offset option, but the temperature difference between each cone obviously ranges from 9 degrees F to 93 degrees F. We could also reprogram the peak temperature for each cone to the cone below, but it's easier just to choose one cone lower for each firing.

The generic version of the Bartlett V6-CF

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We have a inexperienced people firing the kiln so one reason I bought the Cress E-23 is because programming the controller to cone fire is as easy as using a microwave oven.

The Bartlett computer monitoring the thermocouple is incredibly accurate, just one cone too high - and always exactly one cone too high, regardless of whether we fired Fast, Med-Fast, Medium, Med-Slow, or Slow. It's easy to accommodate, just strange.

We have Orton Witness Cones for ^016, ^06, ^04, ^5, ^6, and ^7 and have repeatedly tried each of them.

To fire each Witness Cone simply program the controller for the next cooler cone and the Witness Cone looks picture perfect where the point of the Witness Cone just barely touches the shelf.

The Cress E23 fires evenly as well, so we can place the Witness Cone anywhere in the kiln - except right next to the open peep-hole where it fires cooler due to the lack of heat radiation where the wall is missing.

I suspect if we finally send the controller card back to Bartlett to be flashed with the updated version of the programming this quirk will be missing. As you can see below, the CPU is just a 4" x 5" circuit board.

The perfect Witness Cone

The Witness Cone 7 was fired with the Cone 6 program - which gives us a perfect Cone 7.

Every type of Witness Cone we have fires to the correct amount of doneness, but only if we choose the next lower cone program. So we choose Cone 017 to fire a 016 Witness Cone, and a Cone 05 for a perfect 04 Witness Cone.

It's not sensible, and I'm now sure it's an error in the program, but we have to teach people that a quirk of this kiln is they have to select the next lower cone to achieve the firing you want.

This is the actual front of the Cress E-23. The F-or-C button contains a large number of options, such as Pre-Heats, it can allow the Ramp/Hold button to select the Slow-Cooling option or your own program, as well as all the stuff we don't use like delays, thermocouple offsets, reprogramming the temperature for each cone fire, changing between Celsius and Farenheit, and a RESET option that sets everything back to factory options.

The kiln puts out 50% more power than our prior kiln of the same size (which required an electrician to put in the 36 amp 220 volt outlet) and the kiln is remarkably easy to use and accurate, so long as you remember to fire one cone lower than the one you actually want.

http://www.cressmfg.com/pdf/E%20MANUAL%20FOR%20ALL%20OF%20THE%20E%2...

If you look closely at the lid above my partner's right shoulder, you'll see we had to assemble a tin sheet cap which extends over the electronics as the kiln is outdoors.

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