clayshapes Posted July 14, 2012 Report Share Posted July 14, 2012 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. Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 14, 2012 Report Share Posted July 14, 2012 It doesn't sound like you need to recalibrate the setter, rod, and lever if they are working fine at the lower temps. 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. Marcia Link to comment Share on other sites More sharing options...
clayshapes Posted July 14, 2012 Author Report Share Posted July 14, 2012 Thanks Marcia -- I use triangles, and they are bent approximately the same each time, no matter what cone I am using. Very frustrating and mysterious! Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 14, 2012 Report Share Posted July 14, 2012 I don't have a clue but you are wise to use the witness cones as your firing guide. Marcia Link to comment Share on other sites More sharing options...
clayshapes Posted July 14, 2012 Author Report Share Posted July 14, 2012 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!! Link to comment Share on other sites More sharing options...
LilyT Posted July 14, 2012 Report Share Posted July 14, 2012 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. Link to comment Share on other sites More sharing options...
clayshapes Posted July 14, 2012 Author Report Share Posted July 14, 2012 Thanks Lily for your comments. I leave my peepholes closed, and only open them to see the cones a couple times during the last hour or so of firing. 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! Link to comment Share on other sites More sharing options...
Grace Posted July 17, 2012 Report Share Posted July 17, 2012 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. Link to comment Share on other sites More sharing options...
Grace Posted July 17, 2012 Report Share Posted July 17, 2012 I have the exact same problem with my old Duncan kiln - trips too early when doing cone 5 glazing - last time even my cone 4 witness cone didn't bent at all - yet the small cone in the cone sitter definitely bent - and everything that I fired seemed to come out okay... If you ever find a cure for this hiccup please let me know. Thx. Link to comment Share on other sites More sharing options...
neilestrick Posted July 17, 2012 Report Share Posted July 17, 2012 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. Link to comment Share on other sites More sharing options...
clayshapes Posted July 17, 2012 Author Report Share Posted July 17, 2012 Well the pots in my kiln DON'T look good! They are definitely under fired. The glazes aren't matured when the kiln sitter trips the kiln off. Link to comment Share on other sites More sharing options...
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