desertpotter Posted April 8, 2020 Report Share Posted April 8, 2020 Hi there, I have an older manual kiln with three zones, each controllable by a 1/low to 11/high knob. This kiln is run by an updated kiln controller box, which has only one thermocouple in the middle of the kiln. I always have all three manual knobs set to high during firings, letting the controller box run the firing program. The last cone 5 firing I ran had the top most and bottom most shelves under fire, which I believe might be due to the fact that they were short (1-2 inch posts) shelves and the circulation just wasn’t getting to these areas. My question is - can loading the kiln poorly like this attribute to under firing by that much? Is it a good idea to set the manual knobs on the top and bottom sections of the kiln to high, and leave the middle knob on say, 8 or 9? Hope this makes sense! I will also be keeping my shorter shelves in the middle of the kiln since I now know how badly this can effect the firing. I also had the idea of slowing down the last leg of the firing schedule, which was at a ramp of 120 degrees per hour to maybe 110 to even out the firing. Thanks for any guidance! Link to comment Share on other sites More sharing options...
neilestrick Posted April 8, 2020 Report Share Posted April 8, 2020 Yes, uneven loading can definitely cause pretty big temperature differences. You should load the bottom and top looser, or with taller pieces, and middle tighter with smaller pieces. The middle want to run hot, and the top and bottom run cold due to heat loss out the lid and floor. Leave all the switches on high. Set your last ramp to 108F/hr, as that's the typical setting in controllers, and the rate that is most commonly used for cones. Link to comment Share on other sites More sharing options...
Sorcery Posted April 9, 2020 Report Share Posted April 9, 2020 I never noticed shorter spaces being cooler in my manual kiln. I did notice underfired shelves where one element of 5 was turned off in attempt to "hold" a temperature. Sounds like the elements are going. Sorce Link to comment Share on other sites More sharing options...
neilestrick Posted April 9, 2020 Report Share Posted April 9, 2020 2 hours ago, Sorcery said: I never noticed shorter spaces being cooler in my manual kiln. I did notice underfired shelves where one element of 5 was turned off in attempt to "hold" a temperature. Sounds like the elements are going. Sorce It's not that you can't have shorter spaces in the kiln, it's just when the very top or very bottom are short spaces. Link to comment Share on other sites More sharing options...
Hulk Posted April 9, 2020 Report Share Posted April 9, 2020 Am finding that staggering shelves - I have only half shelves, no full shelves - can be very effective in evening out the heat. My kiln tends to run cool on top; staggered shelves allow ware there to "see" more element, hence hotter. More levels can allow more ware as well - flared pieces, like bowls. Link to comment Share on other sites More sharing options...
MFP Posted April 11, 2020 Report Share Posted April 11, 2020 On 4/8/2020 at 9:42 AM, desertpotter said: Hi there, I have an older manual kiln with three zones, each controllable by a 1/low to 11/high knob. This kiln is run by an updated kiln controller box, which has only one thermocouple in the middle of the kiln. I always have all three manual knobs set to high during firings, letting the controller box run the firing program. The last cone 5 firing I ran had the top most and bottom most shelves under fire, which I believe might be due to the fact that they were short (1-2 inch posts) shelves and the circulation just wasn’t getting to these areas. My question is - can loading the kiln poorly like this attribute to under firing by that much? Is it a good idea to set the manual knobs on the top and bottom sections of the kiln to high, and leave the middle knob on say, 8 or 9? Hope this makes sense! I will also be keeping my shorter shelves in the middle of the kiln since I now know how badly this can effect the firing. I also had the idea of slowing down the last leg of the firing schedule, which was at a ramp of 120 degrees per hour to maybe 110 to even out the firing. Thanks for any guidance! I fixed this same problem by doing three things: 1. I glued one inch of refractory blanket to the outside of the bottom of the kiln. 2. I always put a shelf over the last shelf under the lid. 3. I have a firing schedule where the middle is never turned up onn high. I finish with the bottom on high xz the middle on 5.5 and the top on 6. If anything the top got a bit hot. Hope this helps Link to comment Share on other sites More sharing options...
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