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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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#11 123pop

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Posted 28 August 2014 - 05:05 AM

Help  I have a Cress kiln sitter and glaze fired for the 7th time.  I knew it shut off about a half hour early but thought it knows what it is doing.  Well everything is way underfired and the cone had broken into two pieces ...no bend at all.  I never really looked into the box of cone 6 cones until now and  I found 5 more that are broken in the Orton box. I bought these new about a year ago.  I never dropped or roughly handled the box.  Would you trust this box of cones....??

I was just building up some confidence in pottery and now this. I had some really weird surfaces.  Some crawling, layered glazes with under layer peeling away and of course just plain old dry sandy surfaces.  I am going to try to refire.  Some ideas on methods??



#12 Mark C.

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Posted 28 August 2014 - 10:29 AM

I have had broken cones . I tend not to worry about it. The supports and rod are fine.

The only thing that will affect your cones is getting them wet or damp or exteme humitity.

Cones do not go bad over time.

You could put a dab of kiln wash on supports to smooth the edge out.

Mark


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#13 Marcia Selsor

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Posted 28 August 2014 - 11:17 AM

I have had cracked cones on occasion and never worried about it. As long as they haven't fallen that is good. Make sure the lever on the outside of the setter is properly adjusted so that it shuts off before a break turns into a complete split. Sometimes those weights in the lever slip after time. Just adjust by loosening the set screw and placing the weight in proper alignment with the rod on the cone where you want it to drop the weight and shut off. Retighten set screw.

#14 oldlady

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Posted 28 August 2014 - 01:21 PM

is the diameter of the sensing rod too thin from being used for many firings?  if it is a used kiln, you have no idea how many times that rod has been in there.  replacing the rod won't hurt.  


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#15 123pop

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Posted 28 August 2014 - 04:14 PM

Thanks for the replies but I don't quite understand what you are saying.  The kiln sitter bar cone did not bend at all.  it was perfectly broken in two pieces. And still in the kiln sitter.  And everything is underfired.   I have stored the box in the garage which it has been humid here in TN. 

Talked to Orton and they said a good test for cone stability is to hold it with thumb and index finger of each hand and tug lightly.  Sure enough about 8 more broke.  The rest seemed solid.  Good to know.  I think I'm going to refire the whole load since anything I touched up with glaze show crazing pattern through the glaze even if I couldn't see it.

 

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