Calling on Kiln experts

I believe in always doing a 30 minute soak. It gives glazes time to mature and allows the evening out of temperature in the kiln. I always do a thirty minute soak when doing a bisque too. Dropping the temp might extend the life of the elements a little, at my local club (I have my own kiln though) we dropped from cone 8 to cone 6 firings, we also introduced a kiln firers test and certificate :o) and the maintainance bills dropped away significantly. However from cone 6 to cone

5?? Cone 5 is getting fairly low for domestic ware, plus you would have to check out that all the glazes still worked. Cone 51/2 would be worth looking at I guess. I think though that at our local club having the kilns loaded properly, doing soaks and having a kiln firers test are the things that improved results and reduced maintainance bills. A

In most electric kilns, and probably fuel kilns as well, there's at least a one cone variation in different parts. In electric kilns, the cylindrical shape and tendency for heat to rise make the top hotter. Also the cracks where the lid and body of the kiln meet probably contribute to the problem. Some electric kilns try to help the bottom of the kiln by adding a coil in the floor of the kiln. The best workaround is to use a fairly tall stilt for the bottom shelf--I prefer 6 inches as a minimum. If, as you say, it's a new kiln, the elements should not need replacing for at least 50 glazes, and possibly as much as 100 glaze firings at cone 6. Firing down (soaking) may help alleviate the temperature fluctuations. But you can also learn which glazes work best at a solid cone 6 and which (usually glossy) glazes can take a lower temperature. You'll know when to change elements when they start to burn out, or when the length of firing becomes unacceptably long (they lose heating potential as they age). There's one other fix for uneven heating--getting a thicker coil for the cool area, usually from an element company like Duralite or Euclid's. This will add amperage to the kiln load, so may trip the breaker, so should only be used as a last resort. Brad Sondahl

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Annemarie, I have to ask: What is a "kiln firers test and certificate"?

Thanks!

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

an orton vent can even out the temp differences top to bottom pretty well.

Well there were a lot of people miss firing the kilns. They had work resting against elements, glaze on shelves, programmed the controller incorrectly, fired at the wrong temp. You name it any mistake that they could make they made. Many of these people also thought that they new it all so trying to talk to them just was not working. So two of us came up with the idea of a kiln firing test. We sat down one afternoon and wrote this test out then we intoducted the test and procedure. Rather like a drivers licence, everybody had to sit the test (even the test writers :) before we would be allowed to fire the kilns. Then a certificate goes on the wall and only people who have a certificate could fire the kiln. The result of this was that because there was a formal system more people learned to fire the kilns, those who had been firing for a long time had a refresher and stopped making mistakes. There were a couple of older ladies who took offence and left. That was sad. It was necessary though because the club could not have afforded to continue with the huge maintenance bill. I don't seem to have a copy of the test any more though. I am not on the committee now :o)

Some of the questions were something like this.

How do you stack props in the kiln What happens if you use an earthenware glaze in a stoneware firing

I like it! As it now stands the only people allowed to fire kilns, mix glazes, etc. are those given the task to do (members who know what they are doing, hired student help). Of course our standards change every time a new resident artist takes charge so this may be the future for our studio.