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First Use of Pyrometer for Bisque Firing (Manual Kiln)


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#1 SunsetBay

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Posted 06 November 2012 - 12:37 PM

I have a manual Skutt kiln and just installed a pyrometer and used it for the first time for a bisque firing--mainly out of curiosity, just to see what my kiln is doing and make sure it is doing what it is supposed to be doing (I'll be more concerned with glaze firings, as I'm just starting to make my own glazes; so far, with commercial glazes, everything has been firing just fine). Problem is, I can't figure out, looking at what I recorded, what it means. I used 03, 04, and 05 cones, with an 03 junior cone in the kiln-sitter (my kiln seems to want a kiln-sitter one one cone higher than my goal of ^04 for bisque and ^6 for glaze). I follow the Skutt manual firing schedule: approx. 3 hours on low, approx. 3 hours on medium, then shut the lid all the way and turn the switches to high until the kiln shuts itself off. This time I tried to remember to run out hourly (I was only partly successful in terms of regularity!) to check the pyrometer. Here are my results:

10:30am: turn kiln on low
11:20am: 230 degrees F
12:40pm: 411 degrees F
1:45pm: turn kiln to medium, temp 507 degrees F
2:45pm: 730 degrees F
3:40pm: 857 degrees F
5:00pm: turn kiln to high (lost track of time!), temp 990 degrees F
6:10pm: 1762 degrees F
6:38pm: 1911 degrees F
Looks like the kiln shut off at about 6:45, but I wasn't there to check the temp
7:01pm: kiln off, temp 1838 degrees F
7:31pm: 1576 degrees F
8:00pm: 1372 degrees F
8:30pm: 1199 degrees F
9:00pm: 1058 degrees F
9:30pm: 932 degrees F
After which I got tired and decided to stop checking.

I'm wondering if someone can decipher all this for me. Is that seemingly slow rise to a sudden jump in speed to high normal? Will that cooling rate be too fast for a good glaze firing (though it will likely be different when it starts cooling from the much higher ^6 temps.

Just trying to understand. Any help will be welcome! Thanks!

#2 neilestrick

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Posted 06 November 2012 - 01:32 PM

Check it against the next firing, but it's probably all fine. The temperature drops really fast when the kiln is off. That rate will be different depending on how much ware is in the kiln.
Neil Estrick
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Owner, Neil Estrick Gallery, LLC
www.neilestrickgallery.com

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#3 buckbuck

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Posted 11 November 2012 - 10:07 PM

I had the same kind of results on my Cress manual. I used a pyrometer the first couple loads of bisque and glaze. The long ramp up seems to lead to a fairly quick cone bend at full temp. Results were good. Stopped using the meter. I go with 4 hours on low, 4 hours on medium then max till the kiln sitter does its thing. For bisque I do let it candle an extra hour or two. The cooling time until its safe to open is the hard part. Anxious to see the results!

#4 SunsetBay

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Posted 11 November 2012 - 10:50 PM

Thanks for the responses. Unfortunately, it will be a while before I can mix my new glazes and do a firing, but when I do, I'll try to record the same kind of temp info and see what it looks like. I wonder if it makes sense to try to do two identical (well, as close as possible) versions of each test tile, and do two glaze firings--one the usual way, and one trying to slow down the cooling phase. Am I over-thinking things?




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