Maddriel Posted August 8, 2015 Report Share Posted August 8, 2015 Hello All! I am having an issue with my kiln and I would love some sage advice. I haven't always used witnes cones (I know, I know) but I started noticing that my clay body was not reaching vitrification despite my kiln reporting a successful firing. I use Standard 266 Dark Brown so it's obvious to see when the color has not deepened enough. My first thought was the thermocouple and I replaced that but I am still having the issue. According to the witness cones I have been using for the past five firings the kiln has been firing 2 cones low. (all bisque to 04 since I don't trust this kiln with glaze right now). I have been programming the kiln to fire higher, if I program to 02 It will reach a soft 04. I don't really know if there was a gradual slide for a while and then a big dip, or if it was all gradual and I just didn't catch it. My kiln tech advised me to get new elements, but this seems counter-intuitive to me. If the problem were the elements, then wouldn't I just get an error message because the kiln could not reach temperature? Instead the display reports a completed firing, but the witness cones disagree. Any thoughts or ideas would be greatly appreciated! Olympic Electric Kiln Model 2318HE 240 volts 8400 watts 34 amps Phase 1 Link to comment Share on other sites More sharing options...
Marcia Selsor Posted August 8, 2015 Report Share Posted August 8, 2015 are you soaking the kiln at the desired temperature? For witness cones to melt , they need some headwork as in soaking. If the temperature rises too quickly for the cones to melt, the controller will report the temperature but not the desire result from headwork. Marcia Link to comment Share on other sites More sharing options...
Cavy Fire Studios Posted August 8, 2015 Report Share Posted August 8, 2015 Holy yikes, two cones low?!! That is insane, lady. Though...I think replacing the elements might not be a bad idea, just in case. My Fred was having such a hard time reaching temperature and that was his exact problem--though he has a manual sitter and not a digital controller. Good luck, buddy! ♥ Link to comment Share on other sites More sharing options...
Maddriel Posted August 8, 2015 Author Report Share Posted August 8, 2015 Marcia, For my glaze firings I fire to cone 5 and program in a 15 minute soak, for bisque I do not program a soak. Even with the soak, the clay is not vitrified. I hate to raise the cone in the program in a glaze firing because my clay is very susceptible to bloating above cone 5. Cavy, Mine is Betsy! :-) Link to comment Share on other sites More sharing options...
Marcia Selsor Posted August 8, 2015 Report Share Posted August 8, 2015 One of my controllers seems off from the cones. Do you think yours might be mis-reading? I just adjust my settings and fire hotter or cooler for however the controller is misbehaving. I trust the cones more than the readings.What do the witness cones do in the ^5 glaze? Marcia Link to comment Share on other sites More sharing options...
David Woodin Posted August 9, 2015 Report Share Posted August 9, 2015 Marcia, For my glaze firings I fire to cone 5 and program in a 15 minute soak, for bisque I do not program a soak. Even with the soak, the clay is not vitrified. I hate to raise the cone in the program in a glaze firing because my clay is very susceptible to bloating above cone 5. Cavy, Mine is Betsy! :-) Check to see if you have an offset programmed for the thermocouple, go to the options sections and get to TCOS a 90 before the number will raise the firing temperature OO will decrease the firing temperature. You shouldn't need to soak for 15 minutes. David Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted August 9, 2015 Report Share Posted August 9, 2015 Are you programing in a cone firing or using a cone firing mode. I am not sure how the cone modes work but as the elements degrade could that change the firing if it works more with a time on rather than top temperature? Just a thought. It's a tough question. Link to comment Share on other sites More sharing options...
oldlady Posted August 9, 2015 Report Share Posted August 9, 2015 tomorrow is a business day and you will be able to CALL olympic. do not bother sending emails to any company, they are all ignored. the source is the best place to get an answer that will make sense. ask a technician about everything, write out questions first, make sure of the answers and write them down, too. Link to comment Share on other sites More sharing options...
Diz Posted August 9, 2015 Report Share Posted August 9, 2015 Another thing to check is your electric service - our local art center moved and our trusted kiln was not not firing correctly in the new location. We adjusted the offsets with little improvement. When new elements were suggested, we double checked the elements and electric service in order to have the proper elements. It happened that the kiln room was wired to 208 while the former building and kiln had been wired to 240. Correct elements for 208v and problem solved. Link to comment Share on other sites More sharing options...
Maddriel Posted August 10, 2015 Author Report Share Posted August 10, 2015 Thanks all! When I get in to the studio tomorrow I will check the kiln for any present offset settings, then I will call Olympic for advice. It still seems counter-intuitive to me to have to use some sort of off set programming... It is like you are making up for the failing of the kiln, better to solve the root problem? Anyway, in the long and the short, this kiln cost me $75 and a weekend of camping. It has lasted over 40 firings strong. If Olympic can't help me, then I will find another option! Thanks to all who chipped in! Link to comment Share on other sites More sharing options...
bciskepottery Posted August 10, 2015 Report Share Posted August 10, 2015 An offset is not making up for the failing of the kiln. Some kilns have thermocouples that are enclosed in a ceramic sheath; others do not use a sheath. If you kiln has a sheath over the thermocouple, you need to program an offset to make up for the difference in temperature readings because the thermocouple is enclosed. Kiln makers started using sheaths to protect the delicate ends of the thermocouples from being knocked when loading/unloading, leading to failure and misreading of temperatures. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted August 10, 2015 Report Share Posted August 10, 2015 Thanks all! When I get in to the studio tomorrow I will check the kiln for any present offset settings, then I will call Olympic for advice. It still seems counter-intuitive to me to have to use some sort of off set programming... It is like you are making up for the failing of the kiln, better to solve the root problem? Anyway, in the long and the short, this kiln cost me $75 and a weekend of camping. It has lasted over 40 firings strong. If Olympic can't help me, then I will find another option! Thanks to all who chipped in! If it is second,third hand and you have done that many firings I would take a good look at the elements. Try and get a multimeter and test their resistance values, see how close they are to new ones. The company should know if they need replacing. Not the easiest to get an accurate resistance reading on an element. If you had that many good firings with a slow, only now noticeable change it could well be them. Link to comment Share on other sites More sharing options...
neilestrick Posted August 10, 2015 Report Share Posted August 10, 2015 I would start by replacing the thermocouple. They drift as they age. It's not an element issue, because like you said it would just take longer to get to temp, not fire low. If it's still firing low with the new thermocouple, then you need to either program a thermocouple offset, which will affect all temperatures, or a cone offset which will only affect that cone. Link to comment Share on other sites More sharing options...
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