Emily Pearlman on wed 11 may 05
Thanks to all who have answered . I've learned a lot.
We seem to have solved our immediate problem and all kilns are
operating. I did not give enough info in my first post. One kiln was
firing and we got a fil message. Within an our and other kiln, which
was being loaded gave the same fail message and later that day a 3rd
kiln was unable to get beyond 1300 degrees in many hours. We freaked
out. Our first kiln person suggesed we try the 443 reset code, which
we did to find out which TC had burned out which we did, on the 2 kilns
with the fail message. Apparently we did not reset it back to 3 TC's
after they were changed. We decided to change all the TC's on all the
kilns as all the kilns had about the same # of firings and some looked
about to go. The Kiln that did not go higher that 1300 degrees needed a
new key pad.
But i still have more questions.
When new TC's are put in (we used ones that we got from Cone Art) do
they need to be calibrated to each other, even if they are put in at
the same time? Dont they come calibrated?
One of our kilns is taking much longer to fire to bisque temp. For a
year it has taken 12-13 hours and mow it seems to take 15.5-16.5 hours.
This is with the same program. (it a program we put in the vary fire
method to meet our needs of firing wet bisque and it works
beautifully). What would make it take longer with new TC's ?
Calibration? Or what? I guess they are not like elements which speed
up firings when they are new. Does the distance from the kiln wall
that the TCs are placed make a difference? Even if that difference is
1/4"?
We also have other problems.
One of our members makes large pots with fill up most of the kiln, so
there are no shelves in the kiln during his firings. He has tried both
cone fired programs and vary fired programs to cone 5 and 6. The
witness cones are slightly bent at cone 6, but the pots are greatly
over fired with running glazes and blisters. Needless to say, he fired
them with no problem in manual controlled kiln. Any suggestions on
how to solve this?
I have another problem. I started out using the slow glaze to cone 6
and the pots were cold ( I felt they fired to fast) So I developed my
own program for the vary fire method. it works beautifully to the top
temp of 2232 degrees (which my kiln says is cone 6. However all the
witness cones i put in the kiln (cones 6,7,8,9,) are totally melted.
Everyone always says trust the cones. But i am definitely not going to
cone 9. I fired these glazes for 20 years to cone 6 in a manual
controlled kiln. Oh, I put a cone 9 in the sitter to allow the
controller to turn off the kiln. Its usually bent, but not enough to
turn off the kiln. Does anyone have a clue to what is going on?
I'm very grateful for the information and help that I've gotten from
all of you over the years and hope that you can explain to us what is
going on. While i am happy that I can now get good results from my
firings, I'm the kid of person who always wants to know why?
Thanks!!
Emily
http://www.eppottery.com
Arnold Howard on wed 11 may 05
From: "Emily Pearlman"
> When new TC's are put in (we used ones that we got from Cone Art) do
> they need to be calibrated to each other, even if they are put in at
> the same time? Dont they come calibrated?
It is normal for thermocouples to vary by a few degrees from each other.
Calibrate them by firing the kiln with witness cones in each kiln section.
Make adjustments to the controller to even out the bending of the cones.
> One of our kilns is taking much longer to fire to bisque temp. For a
> year it has taken 12-13 hours and mow it seems to take 15.5-16.5 hours.
> This is with the same program. (it a program we put in the vary fire
> method to meet our needs of firing wet bisque and it works
> beautifully). What would make it take longer with new TC's ?
The extra firing time may be due to firing an uneven load.
Does the distance from the kiln wall
> that the TCs are placed make a difference? Even if that difference is
> 1/4"?
The distance that the thermocouple extends into the firing chamber is very
important. If the thermocouple is not far enough into the chamber, it will
over-fire the kiln to an extent. It is also important to keep shelves and
ware no closer than 1" from the thermocouple. They, too, can affect the
temperature that the thermocouple registers.
> One of our members makes large pots with fill up most of the kiln, so
> there are no shelves in the kiln during his firings. He has tried both
> cone fired programs and vary fired programs to cone 5 and 6. The
> witness cones are slightly bent at cone 6, but the pots are greatly
> over fired with running glazes and blisters. Needless to say, he fired
> them with no problem in manual controlled kiln. Any suggestions on
> how to solve this?
The area where the cones were placed may be cooler than the rest of the
kiln.
> Everyone always says trust the cones. But i am definitely not going to
> cone 9. I fired these glazes for 20 years to cone 6 in a manual
> controlled kiln. Oh, I put a cone 9 in the sitter to allow the
> controller to turn off the kiln. Its usually bent, but not enough to
> turn off the kiln. Does anyone have a clue to what is going on?
Rather than being concerned about a particular cone number, I would use
whatever cone produces the best results with your ware.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
arnoldhoward@att.net / www.paragonweb.com
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