kiln sitter at cone 6 problem
Posted 14 July 2012 - 06:19 AM
Posted 14 July 2012 - 07:51 AM
At ^6 is the cone just mildly bent or does it end up looking like ^04 when it shuts the kiln off.
It is hard to imagine the cone shutting off with a mild bend at one temperature and a v shaped cone at another temperature. Are both cones the same shape unfired or are you using bars in one instance and triangular shapes in another instant. It is strange indeed.
Posted 14 July 2012 - 07:56 AM
Posted 14 July 2012 - 09:20 AM
Posted 14 July 2012 - 10:06 AM
i do use the large shelf cone. i just need to crawl on the floor and blow into the peephole to watch it's progress!!
When the kiln shuts off early with the cone 7 and cone 8 small cones, do they get bent similarly
to the 04 cones at shutoff? And do the cone 7 and cone 8 firings shut off at around the same
time/temp that the cone 6 firing shuts off? What a very curious problem! When you place witness
cones are they all around the kiln, do you see underfiring issues all across your kiln? You mention
needing to be on the floor to watch a cone, could you have a cold spot? If you leave that peephole
open you could theoretically have a cold draft up the front of the kiln.
Posted 14 July 2012 - 10:25 AM
Theoretically, I could have a cold spot (or in this case, a HOT spot) but I just replaced all of my element coils, so I don't think that's the problem.
I only place a witness cone on the bottom shelf - my peephole positions don't make it feasible to place cones on more than one shelf (I can't see them if I do). But I'm happy with the way pieces are firing on all shelves. My upper shelves USED to be cooler than my bottom shelf, but I can tell by the way my glazes fire, since the new elements were installed, that all shelves are basically firing at the same temp -- and if they aren't I don't worry too much -- the pieces are coming out the way I want them to.
In any case, if my upper shelves were firing cooler, that still wouldn't explain why my kiln sitter (which is in the middle to high position) would close down earlier than my bottom cone bends to the proper position.
I thought that after I replaced the elements with new ones the kiln sitter problem would go away...but it behaves exactly the same way as it did before I replaced the elements. My kiln fires much more efficiently though, in a shorter period of time for all cones.
Oh well. I'll just keep crawling on the ground and blowing into my little kiln!
Posted 17 July 2012 - 02:00 PM
I have an old Duncan kiln that works just fine (since I recently replaced all the coils) except the kiln sitter always turns the kiln off way to early when I am firing to cone 6. When I am bisque firing to cone 04, with an 03 small cone in the sitter, it works perfectly. But when firing to cone 6 with a cone 7 or even 8 small cone in the sitter, it turns the kiln off way too early. I've abandoned it when firing to cone 6, and have gotten to know my kiln well enough that I start watching the cones about an hour before I think the #6 cone will bend properly and just keep an eye on it for the last hour. This works fine...but I wish I could get the kiln sitter to work. Any tips? I've tried recalibrating it several times...to no avail. I guess it's just too hot for it to work at cone 6.
Posted 17 July 2012 - 02:04 PM
Posted 17 July 2012 - 02:41 PM
I only place a witness cone on the bottom shelf - my peephole positions don't make it feasible to place cones on more than one shelf (I can't see them if I do).
The bottom shelf is the worst spot for a cone. It's likely to be the coldest place in the kiln. So if cone 8 is shutting off in the sitter, but cone 6 is just bending on the shelf, then the bottom is a cold spot. It has more to do with the way you load the kiln than anything. Keep the bottom looser, with larger pots, and load tighter at the top.
Ultimately, if the pots look good with a 6 or 7 in the sitter, then don't worry about any of this. Most glazes have a broad enough firing range that they will work with a cone or two variation.
Kiln Repair Tech
Owner, Neil Estrick Gallery, LLC
Posted 17 July 2012 - 02:51 PM
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