Grace Posted July 12, 2012 Report Share Posted July 12, 2012 I'm a newbie to this awesome website - with a question about how long it's taking to fire my large old Duncan Electric Kiln. I bought it 4 years ago, and I have fired it roughly 40 times so far. My father in law made me a pyrometer to put in the middle peep hole, and wired up a controller for me that will let me control my ramp up nice and slow for my bisque firings. When I bisque fire to cone 05, with 4 shelves full with roughly 35-40 bowls and a few plates I start off with a 3 hour soak (under 180 degrees) then go up anywhere from 150 to 250 degrees an hour until I reach 1000, then put the controller to just above the final temp and it s-l-o-w-l-y gets up to temp - usually taking a total of about 12 - 13 hours for the cone sitter to bend and trip, depending on how soon I close the lid (my pieces are small with relatively thin walls, but I usually still have moisture up to around 1300 degrees). After I close the lid the kiln immediately bounces up a few hundred degrees and then it slows down - usually only going up about 100 degrees an hour. According to my Duncan Kiln manual, which only tells me to set low, medium or high at a certain timeframe, the entire process should only take 6 hours. My glaze firings take roughly the same amount of time, even with a faster startup, and half the # of pieces, because by the last 200 degrees it creeps up even slower, which usually bends my small cone in the cone sitter roughly 100 degrees before it should. The witness cones aren't bending, not even my cone 4. Yet, my end results seem okay so far. Questions: 1) I have checked the elements, and all coils are glowing brightly - but could they be less effective because they are so old? I checked with my ceramics supplier, and he would want $400 to drive here and replace all my elements - so that's not an option - because I only paid $400 for the kiln to begin with... 2) Should I consider going up one cone higher so the kiln sitter trips at a slightly higher temperature, or (because my results so far are okay) should I leave well enough alone and just live with the longer firing time and the higher electric bill? I am right in the middle of making 200 bowls for a benefit in September, so am keeping my fingers crossed I can get some good advice from those who have much more experience firing than I have. Thanks. Link to comment Share on other sites More sharing options...
Arnold Howard Posted July 12, 2012 Report Share Posted July 12, 2012 Questions: 1) I have checked the elements, and all coils are glowing brightly - but could they be less effective because they are so old? I checked with my ceramics supplier, and he would want $400 to drive here and replace all my elements - so that's not an option - because I only paid $400 for the kiln to begin with... 2) Should I consider going up one cone higher so the kiln sitter trips at a slightly higher temperature, or (because my results so far are okay) should I leave well enough alone and just live with the longer firing time and the higher electric bill? I am right in the middle of making 200 bowls for a benefit in September, so am keeping my fingers crossed I can get some good advice from those who have much more experience firing than I have. Thanks. Low voltage or worn elements could slow down the firings. However, large kilns fire somewhat slowly, so your kiln may be okay as is. Yes, use a hotter cone in the Kiln Sitter to bend the witness cones on the shelf. Sincerely, Arnold Howard Paragon Industries, L.P., Mesquite, Texas USA ahoward@paragonweb.com / www.paragonweb.com Link to comment Share on other sites More sharing options...
neilestrick Posted July 12, 2012 Report Share Posted July 12, 2012 12-13 hours is not too terribly slow, but without knowing how fast it will go with new elements, we don't know if it's normal or not. You'll need to check the element resistance to know for sure if the elements are wearing out. Duncan no longer makes kilns, but Paragon makes parts for many of the Duncan kilns. Link to comment Share on other sites More sharing options...
Grace Posted July 12, 2012 Author Report Share Posted July 12, 2012 Questions: 1) I have checked the elements, and all coils are glowing brightly - but could they be less effective because they are so old? I checked with my ceramics supplier, and he would want $400 to drive here and replace all my elements - so that's not an option - because I only paid $400 for the kiln to begin with... 2) Should I consider going up one cone higher so the kiln sitter trips at a slightly higher temperature, or (because my results so far are okay) should I leave well enough alone and just live with the longer firing time and the higher electric bill? I am right in the middle of making 200 bowls for a benefit in September, so am keeping my fingers crossed I can get some good advice from those who have much more experience firing than I have. Thanks. Low voltage or worn elements could slow down the firings. However, large kilns fire somewhat slowly, so your kiln may be okay as is. Yes, use a hotter cone in the Kiln Sitter to bend the witness cones on the shelf. Sincerely, Arnold Howard Paragon Industries, L.P., Mesquite, Texas USA ahoward@paragonweb.com / www.paragonweb.com Link to comment Share on other sites More sharing options...
Grace Posted July 12, 2012 Author Report Share Posted July 12, 2012 Thanks - checked voltage - okay - will get cone six cones and see what happens. Link to comment Share on other sites More sharing options...
Grace Posted July 12, 2012 Author Report Share Posted July 12, 2012 12-13 hours is not too terribly slow, but without knowing how fast it will go with new elements, we don't know if it's normal or not. You'll need to check the element resistance to know for sure if the elements are wearing out. Duncan no longer makes kilns, but Paragon makes parts for many of the Duncan kilns. Link to comment Share on other sites More sharing options...
Grace Posted July 12, 2012 Author Report Share Posted July 12, 2012 Just read up on checking element resistance. Article said "Measuring the resistance can be tricky, as you may have to electrically isolate the element to get an accurate reading. Also, making good contact between the element and your ohm meter is critical, otherwise you may get a false indication of infinite resistance (even though the element is fine). " I think I'll have to get my husband, or his electronically inclined father, to test this... Thanks for the advice. Link to comment Share on other sites More sharing options...
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