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Cone Breaking During Firing?


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#1 KristaPiper

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Posted 12 September 2013 - 08:33 AM

My cones are breaking during firing - they aren't breaking all the way through - at least not yet. 

 

The first 8 or so firings with the kiln were fine - no breaking of the cones. Then it started last week the bisque fired cone had a small break in it - nothing major. the glaze one had a bigger break in it and now the bisque from yesterday has an even bigger break.  I thought it might be the supports and sticking to the supports so I flipped them over assuming that nothing had been sticking to that side yet so it might fix it.. but it didn't. So I am planning on getting new supports. 

 

As I have been googling around like crazy the only other thing I can find is it might need a new sensing rod/tube.  From what I can find the rod is supposed to move freely in the tube - I am not sure I know what their definition of "freely" is . The rod moves up and down just fine - it moves to the left side just fine - the right side it doesn't seem to want to hang out... but overall it is in the center of the tube and when it goes up and down it is in the center.  Could I need a new tube?  I have never replaced the tube/sensing rod so I have no idea. It is a used skutt 1027, I thought she said that it had been replaced recently.. I know the elements are new in it. 

 

I am just not 100% sure what it could be. I figured I would start with the support rods and get new ones of those... but I am a little hesitate to do a glaze firing and have the cone break and then ruin that firing. I have a festival coming up that I really can't waste pieces on with having them not firing properly :(  If anyone has had this issue or has experience with this and has some advice that would be amazing! 

 

Thank you so much!

 

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#2 Wyndham

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Posted 12 September 2013 - 08:40 AM

Easier and cheaper to get another box of cones. They may have been stressed or cracked a bit and you can't see that.. Get another bisk & glaze box and try that first.

Wyndham



#3 minspargal

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Posted 12 September 2013 - 08:41 AM

You might try slightly sanding your supports to make them feel smooth, it they feel rough to the touch.   Make your you don't load any thing near your cone holders that might lean on the rods during a firing.



#4 KristaPiper

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Posted 12 September 2013 - 08:42 AM

I read about that... they might have hairline cracks and stuff that aren't visible.  I might have just gotten lucky and picked a good cone out of the boxes for the first couple of firings.  I figure I might do another bisque firing before a glaze one to make sure it is fixed. I would rather the bisque not get 100% to temp then the glaze.  Thank you!



#5 neilestrick

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Posted 12 September 2013 - 08:44 AM

I often see cones break instead of bend, and have never worried about it. Try smoothing out your cone supports with some fine 220 grit black sandpaper. Your sensing rod should move freely up and down, but not really side to side much. The rod should be straight, and should not taper to the end. No need to replace the whole tube unless it's broken.


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#6 KristaPiper

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Posted 12 September 2013 - 08:45 AM

They are rough.  I try not to put anything to close to them and make sure a shelf is never aligned right with it.  If I can I usually have a shelf a couple inches above it and a couple inches below it so that it has plenty of clearance. Normally I am able to stagger my shelves, but I have been doing a lot of bigger pieces that require the use of almost the entire shelf so I haven't been able to stagger them like normal.  I don't know if that would play into it or not. 



#7 Arnold Howard

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Posted 12 September 2013 - 09:42 AM

My cones are breaking during firing - they aren't breaking all the way through - at least not yet. 

Do you have a downdraft vent mounted under the kiln? I have heard of cones that broke due to vibration from the vent motor.

 

Orton says the side of the cone that has the stamped number should go toward the bottom when inserted on the cone supports. Placing that side down very slightly lessens the chance of breakage.

 

Sincerely,

 

Arnold Howard

Paragon Industries, L.P., Mesquite, Texas USA

ahoward@paragonweb.com / www.paragonweb.com



#8 JBaymore

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Posted 12 September 2013 - 10:58 AM

Have the cones been stored in an area that gets damp (leakage or VERY high humidity for extended periods)?

 

best,

 

.......................john


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#9 dave the potter

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Posted 12 September 2013 - 11:33 AM

I have always coated the cone supports and rod with a thin layer of kiln wash to make sure nothing gets stuck. I also use bars instead of cones to get the most accurate firing.



#10 neilestrick

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Posted 12 September 2013 - 04:30 PM

Staggering shelves will not affect anything. It's not necessary.


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