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Post by annette on Aug 10, 2018 1:33:00 GMT -6
Hi - I have been doing crystalline for a while but the last few firings have been massive disasters. It seems like everything is sticking to the kilns shelves now matter how careful i am - even the kiln props !! now I have changed the thermocouple thinking i may have an issue and did a firing today and the same result - the kiln is "konking" out at 1227 where as it used to do 1280 relatively easy, i did let it drop from there to crystal growth range and continued the firing. I am about to do a firing with just witness cones to see what they say (yes i know i should always use them!) . It is a SKUTT KM818 - 240 volt. I have new elements on the way from the US as initially I thought it was that - but the everything sticking is weird and making me think I may be over firing and the thermocouple is not reading properly. Oh yes and i re-kiln washed every time and used fresh kiln wash in the next attempt (not that the age of it should matter i would think).
I have not changed glazes nor clay bodies.
Any help advice welcome - it is very weird and very distressing I am losing so much ware.
Addition - I have just done more diagnostics on the kiln - and it looks like to get to 1226 - it took 11 hours which is 2 hours over the schedule i had programmed so I suspect that the last 2 hours have crept up very slowly so the heat work - whilst despite not getting to a high temp has caused the issues and indeed I need new elements. So I have not done a firing with just witness cones as I figure if my analysis is correct it would be simply a waste of power :-(
Comments please even if to tell me I have been really stupid !! |
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Post by adammacmillan on Aug 10, 2018 13:46:11 GMT -6
Are you using a platinum (type R or S) thermocouple? If so, those are very accurate and don’t age much. If it’s a type K, that may be part of the problem, but it sounds like you are on to it with the elements. Pictures of results would help
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joerg
New Member
website: www.crystalsforever.com
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Post by joerg on Aug 10, 2018 16:17:24 GMT -6
Hi - I have been doing crystalline for a while but the last few firings have been massive disasters. It seems like everything is sticking to the kilns shelves now matter how careful i am - even the kiln props !! now I have changed the thermocouple thinking i may have an issue and did a firing today and the same result - the kiln is "konking" out at 1227 where as it used to do 1280 relatively easy, i did let it drop from there to crystal growth range and continued the firing. I am about to do a firing with just witness cones to see what they say (yes i know i should always use them!) . It is a SKUTT KM818 - 240 volt. I have new elements on the way from the US as initially I thought it was that - but the everything sticking is weird and making me think I may be over firing and the thermocouple is not reading properly. Oh yes and i re-kiln washed every time and used fresh kiln wash in the next attempt (not that the age of it should matter i would think).
I have not changed glazes nor clay bodies.
Any help advice welcome - it is very weird and very distressing I am losing so much ware.
Addition - I have just done more diagnostics on the kiln - and it looks like to get to 1226 - it took 11 hours which is 2 hours over the schedule i had programmed so I suspect that the last 2 hours have crept up very slowly so the heat work - whilst despite not getting to a high temp has caused the issues and indeed I need new elements. So I have not done a firing with just witness cones as I figure if my analysis is correct it would be simply a waste of power :-(
Comments please even if to tell me I have been really stupid !! |
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joerg
New Member
website: www.crystalsforever.com
Posts: 49
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Post by joerg on Aug 10, 2018 16:20:38 GMT -6
Hi Annette!that looks like a failure of one or two of your heating elements...fire the kiln empty to some 200° ... and you easily note by the color.... Hi - I have been doing crystalline for a while but the last few firings have been massive disasters. It seems like everything is sticking to the kilns shelves now matter how careful i am - even the kiln props !! now I have changed the thermocouple thinking i may have an issue and did a firing today and the same result - the kiln is "konking" out at 1227 where as it used to do 1280 relatively easy, i did let it drop from there to crystal growth range and continued the firing. I am about to do a firing with just witness cones to see what they say (yes i know i should always use them!) . It is a SKUTT KM818 - 240 volt. I have new elements on the way from the US as initially I thought it was that - but the everything sticking is weird and making me think I may be over firing and the thermocouple is not reading properly. Oh yes and i re-kiln washed every time and used fresh kiln wash in the next attempt (not that the age of it should matter i would think).
I have not changed glazes nor clay bodies.
Any help advice welcome - it is very weird and very distressing I am losing so much ware.
Addition - I have just done more diagnostics on the kiln - and it looks like to get to 1226 - it took 11 hours which is 2 hours over the schedule i had programmed so I suspect that the last 2 hours have crept up very slowly so the heat work - whilst despite not getting to a high temp has caused the issues and indeed I need new elements. So I have not done a firing with just witness cones as I figure if my analysis is correct it would be simply a waste of power :-(
Comments please even if to tell me I have been really stupid !!
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Post by annette on Aug 10, 2018 16:32:43 GMT -6
Hi - I just had a long conversation with Perry at Skutt kilns - he thinks it the elements have worn and the new ones will help so I will wait. The kiln would of sat at 1220 for a number of hours and he believes all that heatwork will have caused the issues with the ware and the shelves and props.
One element out I would not have made it to 1220 was his advice - the unusual thing is that the elements went so quickly .............
So I wait for the new elements to arrive and pray to the kiln gods this was the issue
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Post by bill2015 on Aug 11, 2018 8:19:46 GMT -6
Annette, It appears you have found the issue - elements worn down struggling to make programmed temperature and with the slower heat rise, the more heat work taking place and most likely over firing. Now might be a good time to get into the witness cone habit, a "cone pack" of 3 cones: guide, firing and guard cone - 9, 10, 11. Use self supporting cones, a bit more expensive but less trouble setting them. As was suggested, spending the money and getting a type "S" thermocouple to replace the current type "K". Type "K" are economical but inaccurate above 2000F/1093C and like elements, they wear out rather quickly. The type "S" will last a very long time.
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Post by tileman2 on Aug 11, 2018 11:35:13 GMT -6
Type S indeed. Price a set of APM elements, and save up for them for the next change out. I average 400 firings with them (cone 6).
Tom
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Post by adammacmillan on Aug 13, 2018 6:44:36 GMT -6
Type S indeed. Price a set of APM elements, and save up for them for the next change out. I average 400 firings with them (cone 6). Tom I second the APMs. Over 200 cone 11+ fires and still no change in firing time. |
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joerg
New Member
website: www.crystalsforever.com
Posts: 49
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Post by joerg on Aug 13, 2018 15:32:53 GMT -6
"S" thermocouples are nice....then agin...I have 4 kilns and 4 "S" thermocouples, 3 electrical, one battery driven ... I tried to compare the exactness, letting 2 run at the same time in one kiln... they vary between 15 and 30 (!!!) degrees C at top temp., that's a hell of a lot (and which one is the correct heat  ) any proposal? |
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Post by tileman2 on Aug 13, 2018 16:20:35 GMT -6
Joerg:
I would think cones would pick up 30C difference, pending peak temp. I have a hand held type K probe I use to calibrate measuring from 1000 to 1100C. Between the hand held probe and cones: I do a TC ( thermocouple) offset accordingly. I also have four kilns: and each have 15-40F degree TC offset.
Tom
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joerg
New Member
website: www.crystalsforever.com
Posts: 49
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Post by joerg on Aug 16, 2018 15:13:40 GMT -6
thanks tileman... best way to know your kilns is to work with cones... always :-)
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) any proposal? 