newps Posted January 15, 2019 Report Share Posted January 15, 2019 Hi All, I have taken up pottery since taking early retirement, and noticed that my mothers old kiln for china paining should fire to 1300 and also that many potters seem to use the Cromartie Hobycraft 40. My kiln a Cromartie KLN40 is the predecessor to those but sadly the kiln instructions have been lost over the years. Dad used to do the firing, but he died over 25 years ago. I have consulted Cromartie but the controller instructions they supplied were for a controller that had a "Soak timer", which mine doesn't, and they have no guidance on how to use the rotary switch on the kiln body. Can anyone offer guidance. The photo shows the controller I have Link to comment Share on other sites More sharing options...
Chilly Posted January 15, 2019 Report Share Posted January 15, 2019 Hi @newps Welcome to the forum. It's weird, it looks much more modern than the controller that came on my old kiln, yet it has less "features". Is that all there is? Is there a kiln-sitter on the actual kiln? Something with a rod that goes inside the kiln, like this photo? I'm not going to be much help, but I'm sure the rest of the gang will chime in soon. Did your dad have a firing notebook that could give you any clues? Ahh, just re-read, and you said "rotary switch". Can you take a photo of that and post it? Link to comment Share on other sites More sharing options...
newps Posted January 15, 2019 Author Report Share Posted January 15, 2019 Hi, There is no kiln sitter, its very basic. This is the rotary switch I described. We think the kiln is probably over 30 years old but hasn't done many firings. I am not aware of Dad doing any logs of firings. I did a test firing over the weekend but unfortunately my lack of knowledge on cones caused a problem. I had ordered some 08 and some 10 cones I put one of each in and over about 8 hours cranked the temperature up to 1300 on the controller. I opened the kiln when it had closed to find 2 totally melted cones. I didn't realise that pushing a cone about 100C above its temperature would totally melt it, nor did I realise that a 10 cone should be pink. My suppliers had sent 08 and 010 cones. All credit to the Tech support at Orton for rapidly explaining what had happened and why they spotted I didnt have the 10 cone I was wanting to use for the max temperature Link to comment Share on other sites More sharing options...
Stephen Posted January 16, 2019 Report Share Posted January 16, 2019 ya know I might be misunderstanding you but you would not put in cones like that. The 0 anything would just melt and have to be scraped off your shelf. Don't get the cone 10 melt though as 1300c is cone 10 if you have one speed that runs in the 270 per hour ramp range. The whole point though of the cones is to visually nail where the kiln fired to. We use a 3-cone pack (often on several shelves. We fire mid so for bisque the pack has an 05 04 03 and we are looking for a full bend on 05 and a half bend on 04, 03 unaffected. For glaze we have a 5, 6 and 7. We fire to cone 5 with another cone of heat work for 20 minute soak so we are looking for a full bend of 5, half bend of 6 and no effect on 7. Print out a cone chart to get a feel. If you are low firing (most bisque 04 and glaze 06- bisque is usually hotter on low fire) and mid fire is 5-7 with an 06-04 bisque. Most people seem to recommend firing your electric kiln 2 cones below its max rating. Firing at max will wear out the bricks and elements much faster. If you only have the cones and an one switch to hit temp then I would use a log and find that spot for each cone you want and record the time (hours to reach) then fashion a pack with one cone below, one cone exact and one cone above and put these packs on a top shelf, middle shelf and bottom shelf. Start a log and check your cones religiously after each firing and note the element wear and time adjustment needed for the next firing. At some point (with an old kiln that might be sooner than later) you will need a set of elements because the kiln will not hit temp no matter how long you run it. If you don't keep track of this stuff then you will start having bad glaze loads when the elements wear out. I see a 'full' on the knob so I think you have more control than you think by working through those clicks at different times in your firing to affect the ramp speed. Link to comment Share on other sites More sharing options...
newps Posted January 21, 2019 Author Report Share Posted January 21, 2019 I appreciate the comments. The kiln was originally bought for china painting which I believe were fired at about 850C. For some time mum had wanted to get rid of the kiln as she couldn't use it To my knowledge Dad only ever used the dial on the controller which may be why some of the painting had a better finish than others. I had been told it couldn't fire pots however seeing its max temperature was 1300C made me think it might do pots and as I couldn't find anyone interested in buying china painting kilns. The idea of the 10 cone and pushing the kiln to its upper limit was to see if it could reach pot firing and glazing temperatures. I have learnt the hard way that if you go too far beyond a cones temperature they melt to a horrible mess, but based on that I can assume (based on advice from Orton) that the kiln reaches at least 1042C Since starting this thread I have had to sort through a load of financial papers for my mum and hidden in the middle of them I found the original instructions - its a Cromartie Kiln C740 Soak/Cut off non-indicating controller. Thanks to all for the feedback Link to comment Share on other sites More sharing options...
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