SunsetBay Posted January 27, 2012 Report Share Posted January 27, 2012 I'm somewhat of a newbie, and I'm confused by Richard Zakin's (Electric Kiln Ceramics) glaze firing schedule. First of all, he has you close the kiln door after only half an hour on low--I can't do this, because I don't have a venting system. I've been closing when I turn the kiln up to high, as per my Skutt manual, but I'm going to try closing when I turn the kiln switches to medium, as suggested by some others. Second, he advocates keeping the kiln on low for 9 hours, putting it on medium for half an hour, and then switching to high. I've never heard of that kind of schedule. 9 hours on low? Maybe if the pieces aren't bone dry... But then only a half-hour on medium? Does anyone else have any insight on this? I'm firing to cones 5 or 6. The kiln is manual, not programmable. I should add that so far I've been using the schedule suggested in my Skutt manual (3 hours on low, 3 hours on medium, then close the lid and turn to high) and my pieces have been turning out fine, or so they seem. I'm just curious about other firing schedules. Thanks! Link to comment Share on other sites More sharing options...
LawPots Posted January 27, 2012 Report Share Posted January 27, 2012 I would also be curious about Zatkin's firing schedule. I've tested my kiln with a pyrometer (a somewhat cheap one that can't handle temperatures over 800F), and I know that with the lid closed and the top peep hole open, the temperature in my kiln stablizes at about after about 2 hours with the lid closed on low (technically, 1 on my Cress) at about 670. So, what's the thinking behind a very long lower temperature soak at the beginning of the cycle? Link to comment Share on other sites More sharing options...
Lucille Oka Posted January 27, 2012 Report Share Posted January 27, 2012 SunsetBay- you have the kiln manufacturer's manual I commend you for reading and following it. If you have good firings you have the best information possible. Lawpots- you have found the best method for your firings it is good that you have. Do you have your manual? If not, try to get one. You will find in ceramics a lot of opinions and they often agree and often vary. Whenever you need information about your kiln or you find discrepant information about firing your kiln, your manufacturer's operation manual or a direct call to the manufacturer will be your most reliable source for information. Link to comment Share on other sites More sharing options...
Denice Posted January 28, 2012 Report Share Posted January 28, 2012 As you do more firing and different types of firings you'll figure out the changes you need to make for that particular load. For heavy wall sculptural work and packed loads I will turn on the bottom low over night and slow down the whole process. I have to much work in it to rush and take a chance on the pieces not getting fired completely or correctly. Denice Link to comment Share on other sites More sharing options...
TJR Posted January 28, 2012 Report Share Posted January 28, 2012 I have until recently worked in a cooperative studio with 24 members . Most fire to Cone 6. No one fires on low for 9 hours. If you had thick sculptural pieces, you could fire overnight with one element on low and the top spy hole open. We fire 2 hours on low.With top spy open and lid down. One to 2 hours on medium, for one to 2 hours. Usually one hour.Spy holes plugged. Then all switches on high. Usually takes 6-8 hours for a bisque, longer for Cone 6. TJR. Link to comment Share on other sites More sharing options...
SunsetBay Posted January 28, 2012 Author Report Share Posted January 28, 2012 Thanks, everyone! I guess if what I'm doing (which is what the manufacturer suggests) is working, I should probably stick with that! I was thinking of trying Zakin's suggestion of an hour on low after the kiln shuts off, but now that I think about it, that wouldn't seem to make any sense to me. Once the kiln-sitter shuts the kiln off, doesn't it take a kiln more than an hour to cool down to the "low" level anyway? I'm just curious. Link to comment Share on other sites More sharing options...
bciskepottery Posted January 28, 2012 Report Share Posted January 28, 2012 Zakin, from what I understand, believed a slow firing up (hence 9 hours at low) and slow firing down (turning back on low an hour after hitting peak temperature) made for more interesting glazes and promoted crystal formation. Many electric kiln books and ^6 glaze books now recommend a firing down/hold in the range of 1500F to 1750F to develop/promote crystals. Link to comment Share on other sites More sharing options...
LawPots Posted January 29, 2012 Report Share Posted January 29, 2012 Zakin, from what I understand, believed a slow firing up (hence 9 hours at low) and slow firing down (turning back on low an hour after hitting peak temperature) made for more interesting glazes and promoted crystal formation. Many electric kiln books and ^6 glaze books now recommend a firing down/hold in the range of 1500F to 1750F to develop/promote crystals. At best i am an enthusiastic amateur. I had good luck in my second glaze firing using the firemate and a slower beginning (two hours with the lid open on low, two hours with the lid closed on low, and then using the firemate to automatically raise the temperature). This is not exactly what the latest manual for the cress firemate recommends, but then, the manual I found is for a multispeed firemate, and my used one seems to have only one setting. I still soaked at a medium temperature after the kiln sitter shut it off for an hour, but only because cone six hadn't fallen. So far I've only fired to glaze temperatures twice, so I'm still trying to figure my kiln out. I really appreciate this insight into Zakin, because the other references I've found start slow, but never quite that slow, and I've wondered what he wanted to accomplish. Chemically, I didn't think much happened at the lower temperatures to a cone 6 glaze. But, if he saw something happening, it might be worth a try, especially if I try one of his glazes. Link to comment Share on other sites More sharing options...
SunsetBay Posted January 31, 2012 Author Report Share Posted January 31, 2012 Zakin, from what I understand, believed a slow firing up (hence 9 hours at low) and slow firing down (turning back on low an hour after hitting peak temperature) made for more interesting glazes and promoted crystal formation. Many electric kiln books and ^6 glaze books now recommend a firing down/hold in the range of 1500F to 1750F to develop/promote crystals. From the book: "Ceramists experienced in firing in the electric kiln generally prefer a long slow 'stewing' kind of firing process, however. They feel that a long slow temperature rise is best. This is important because a slow cooling encourages crystal formation in a glaze while it is cooling." Okay, I'm not understanding what a long slow temperature RISE has to do with a slow cooling. On firing down, he says, "Electric kilns (especially thin-walled, poorly insulated electric kilns) have a tendency to lose heat quickly. By firing down, you slow the loss of heat in the firing chamber." He promotes firing down by "Instead of turning off the current completely after the cone has fallen, keep the current on but on a low heat setting." So my kiln REALLY drops to "low" in less than an hour? That seems awfully fast to me, especially considering how long it takes before the kiln can be opened and finally unloaded. Just wondering. Trying to understand my kiln. Thinking of getting a pyrometer! Link to comment Share on other sites More sharing options...
bciskepottery Posted February 1, 2012 Report Share Posted February 1, 2012 Your kiln does not drop from high to low temperature in one hour. By turning the settings to low after reaching peak temperature, you are countering the rate of heat loss associated with cooling. Zakin does this by turning the temperature from high to low; others achieve it by turning kiln off and then restarting it again at a specific temperature. By holding the temperature steady (also called soaking) or slowing the rate of cooling, you allow the glaze to form crystals because you are giving the glaze more time to cool and interact. Low/medium/high are not specific temperatures; they adjust the rate at which the elements heat up the kiln by controlling the flow of electricity through the elements which, in turn, heats the bricks, shelves, and wares inside the kiln. Link to comment Share on other sites More sharing options...
SunsetBay Posted February 1, 2012 Author Report Share Posted February 1, 2012 Your kiln does not drop from high to low temperature in one hour. By turning the settings to low after reaching peak temperature, you are countering the rate of heat loss associated with cooling. Zakin does this by turning the temperature from high to low; others achieve it by turning kiln off and then restarting it again at a specific temperature. By holding the temperature steady (also called soaking) or slowing the rate of cooling, you allow the glaze to form crystals because you are giving the glaze more time to cool and interact. Low/medium/high are not specific temperatures; they adjust the rate at which the elements heat up the kiln by controlling the flow of electricity through the elements which, in turn, heats the bricks, shelves, and wares inside the kiln. Thank you! That makes bucketloads of sense (and does kind of make me want to smack my forehead and say, "Duh!")! :-) I really appreciate the clear explanation. I'm going to try my first soak this evening. Fingers crossed. -------------------------------------------------------------------- EDIT: Okay, I tried a soak. I also altered the firing schedule (still within Skutt manual parameters). Instead of 3 hours on low, 3 hours on medium, close kiln and turn on high until kiln-sitter shuts things off, I did 2 hours on low, 2 hours on medium, close kiln and turn on high, add 1 hour soak on low after kiln-sitter shuts off. Results were not so good. I have quite a bit of pinholing on a number of the pieces, and small "pockmarks" of what looks like crawling. I will refire those pieces and see what happens. I don't know why the different schedule might have caused this different result and I'd love some ideas about it, but it does look like I should go back to the schedule that has been working for me... Link to comment Share on other sites More sharing options...
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