Jump to content
Sign in to follow this  
Maddriel

Kiln Not Reaching Temp Via Witness Cones

Recommended Posts

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

 

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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! ♥

Share this post


Link to post
Share on other sites

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!  :-)

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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 

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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!

Share this post


Link to post
Share on other sites

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. 

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×

Important Information

By using this site, you agree to our Terms of Use.