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Using Vent Caused Underfiring ?

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Oh, believe me, that is not something I will be messing with on my own.  I have discussed both the bisque and glaze schedule I have been using a with a Skutt tec several times and he has not suggested calibrating the TC . He wants me to replace the TC and see what that does.

Sounds like the calibration is something I can check by going through the menu of options where I checked the amps and volts, I will look at what other assessment option keys I have there.  Very much electricity/computer and I am way over my head.

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The Skutt Tech is correct in asking you to start with a new thermocouple.  One of your problems will be to determine what the actual temperature is.  Technicians have the means to determine this, a brand new thermocouple takes care of one variable.  It will be interesting to see if there are any offsets applied to thermocouple or cone heatwork.  I have never found the controller itself more than +,- 2 deg F which is well within spec's. Too bad you are not closer to the west, this is a very interesting problem.  Another question, do you use self standing cones to check heat work?  Making your own cone packs is okay if you read the fine print on how to set them, correct angle and depth. Self standing cones are always repeatable.  Is the thermocouple an 8 gauge type K  that is in a ceramic protecting tube?  

David

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I always use Self supporting cones.  the TC is in a 2 part ceramic tube, it is the one the nearest Skutt dealer sells for this kiln. I have a new TC ordered, should have it first of the week. I'm headed to the studio to unload the test refire of the bisque, using the firing schedule I have always used, with the vent on. we'll see what those cones look like,, then make a plan.

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I always use Self supporting cones.  the TC is in a 2 part ceramic tube, it is the one the nearest Skutt dealer sells for this kiln.

 

Do you mean the ceramic 'beads' that slide over the two wires of the thermocouple from the open end, or a fully enclosed protection tube?

 

TC (bottom) or the protection tube (top) also? :

 

post-6933-0-59268200-1431635170_thumb.jpg

post-6933-0-59268200-1431635170_thumb.jpg

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I neglected to ask you what controller you have.  If it is the wall mount and old you may not have any options that allow you to review the offsets for T/C and cone and then that is why Skutt says you need new controller.

David

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OK, I just unloaded the re fired bisque.  With the vent running, and the following firing rates,

100*/hr to 200* no hold

150*/hr to 600) hold 30 min

200*/hr to 1650* hold 1 hour

100*/hr to 1920* hold 1 hour

I got hot cone 03. middle was maybe an 02, I didn't have those cones to put in. Exactly what Neil said I would get, .

With this same firing rate and no vent, I have been getting 05-04 for 3 years or more.  WHY did the vent make it fire hotter?

 

David it is on the side of the kiln, kiln is 7 years old. The TC doesn't look like either of those pics.  has the tip showing with a 2 part ceramic tube covering the rest of it.

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Before the vent you had stagnent air now you have some air movement.  If you want to continue to use your program, change the last hold time to 15 minutes with vent on.  This doesn't explain why the cone fire mode didn't work all though you could add some hold time to it, like 10 minutes.  There maybe something the Skutt tech can see from this latest information.  It looks like the T/C is reading correct but there may be a problem with the cone 04 offset if the number starts with 9 it is negative, if it start with 0 it is positive.

David

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