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Elise

Kiln questions/Cones snapping during firing again

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I had this issue late last year but had a few successful firings since then, so I thought I had resolved this but now my cones are snapping during firing, instead of bending. It happens sometime after I switch gauges from medium to high. It’s happened in three bisque firings in a row.

I used three different boxes of cones for each firing, I feel eliminating the chance that the issue is with the cones themselves.  Cones 04 and 05 were used. 

I have an old L&L Econo Kiln, manual. This is my first kiln and I am very green but I’m learning. 

Does anyone have any suggestions for how to fix this?

Also, I am wondering if there is supposed to be a plug for outlet #2? See photo please 

TIA 

3FC2BFB6-53DF-459E-9CD9-92E6F0D3153D.jpeg

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1 minute ago, neilestrick said:

How many sections/rings does your kiln have?

Please post a picture of the entire kiln, and a pic of your broken cones.

It has 3 rings. 

Here are the broken cones and I am not home currently but I have some photos in my phone of the kiln, give me a few minutes to find them. 

9A3A9644-D9E0-43FB-8CBC-D4C516AFF095.jpeg

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It has 2 rings, so 2 jumper cords. They probably just built the control boxes with 3 plugs as the standard, and used them on all 2 and 3 section kilns. As long as you're using the correct plugs and switches.

When you said they cones were snapping, I was expecting to see them at least partially bent before breaking, but yours appear to have broken before they ever got soft. There must be some adjustment out of whack in your sitter. Is the rod that sits on top of the cone resting lightly on the cone, or do you have to force the cone into place between the rod and bottom rests? If you have to force it at all, then chances are the rod is bent and should be replaced.

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AHA! If you're doing it like you show in the video, you're using 2 cones. They come hooked together in pairs, and you have to snap them apart and just use one. When you put in in the sitter, have the rod resting on the spine, with the little number facing toward the opposite wall.

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Oh! That is definitely useful information but that was a box a new cones that I haven’t used yet, Cone 6. The others, the ones that broke in firing,  were already snapped apart, Cones 05 and 04. I just used the cone 6’s for example. But I definitely didn’t know that I needed to break these ones apart when I do use them. So thank you!!

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The cones 04 and 05 that I have (multiple boxes) were all given to me with the kiln. Do you think it’s possible that all of those boxes are just defective, perhaps they got too damp or something? 

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2 hours ago, Elise said:

The cones 04 and 05 that I have (multiple boxes) were all given to me with the kiln. Do you think it’s possible that all of those boxes are just defective, perhaps they got too damp or something? 

That's quite possible. Your sitter rod appears to be in great condition, so I'd try the new cones and see how it goes.

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8 hours ago, Mark C. said:

They they ever get wet??

I’m really not sure since they were given to me with the kiln. I will try the new cones in a firing today, hopefully it works 

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On 9/15/2019 at 6:48 PM, neilestrick said:

That's quite possible. Your sitter rod appears to be in great condition, so I'd try the new cones and see how it goes.

I did another firing with a brand new cone 05. It snapped as well. Just like the others. :(

So I don’t think it’s a cone issue.  Such a bummer. 

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@Elise Try putting a small amount of kiln wash on the bars that the cones rests on. Just enough to make a barrier between the cone and the bars. I wonder if the cone is sticking to the metal, and snapping as it heats and expands.

Does the kiln turn off when the cone breaks? How hot is it getting?

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16 minutes ago, neilestrick said:

@Elise Try putting a small amount of kiln wash on the bars that the cones rests on. Just enough to make a barrier between the cone and the bars. I wonder if the cone is sticking to the metal, and snapping as it heats and expands.

Does the kiln turn off when the cone breaks? How hot is it getting?

That is a great thought because there is usually a small amount of the cone stuck to the metal of the bottom two holders that I’ve had to scrape off, see photo. I couldn’t get my camera to focus properly but you can see the brown of the cone on the silver metal. I will apply some kiln wash now. 

The kiln does turn off when the cone breaks. I am not sure how hot it’s getting but it always happens after I turn the gauges from medium to high. 

8AF3BB72-79BA-4ED0-9858-1B492321C82D.jpeg

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Are you lifting the shut-off weight, and holding it in place while you put the cone on the sitter,  or are you placing the cone first, then lifting the weight ?  (Placing cone first would require forcing the outer end of the rod upward to get the weight behind it - which might put enough stress on the cone to cause a small crack before the firing even starts.)

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2 hours ago, Rockhopper said:

Are you lifting the shut-off weight, and holding it in place while you put the cone on the sitter,  or are you placing the cone first, then lifting the weight ?  (Placing cone first would require forcing the outer end of the rod upward to get the weight behind it - which might put enough stress on the cone to cause a small crack before the firing even starts.)

I am lifting the shut off rod and holding it in place while I place the cone.

 

I used kiln wash on the posts, and before I could move from medium to high, the kiln was already off. I lifted the lid and the cone was not in the sitter, but on the floor of the shelf immediately below... I don't understand how this happened. I know I placed the cone correctly.

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Hi Elise,

"Cone packs" on each shelf may give you an idea how much variance there is in peak temperature. I'm finding that the top level runs cool; adjusting the load (how much ware, and shapes...) and staggering shelves helps a lot.

More to your point, if you can see a cone through the peep (does your kiln have peeps?), reset your sitter button and monitor until the cone sags, then shut off.  Be (absolutely, 100%) sure to get and wear kiln glasses to protect your eyes before ever looking into a glowing kiln.

If you don't have guide and guard cones to make up a full cone pack, just set your target cones up where you can clearly see them through the peeps. I paint an iron oxide stripe on - bit easier to see.

I set cones in a strip of clay and block up at least one set right in front of a peep.

Pyrometer could be helpful - I depend on mine quite a bit! 

Edited by Hulk
+r

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I'm really stumped. The only reason a cone should break is if there was some pressure put on it. Just to be sure you're doing it correctly:

1. Lift the weight

2. Push down the claw, which raises the sitter rod and holds the weight in place

3. Place the cone

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How fast are you firing?

Also, do you have a kiln sitter firing gauge? Looks like this. Probably isn't the issue but it is a good idea to check the sitter once in a while. Instructions here on how to do it. image.png.72e9cba3a26e0f6fc389ced6354e4e15.png 

Video on using a kiln sitter here. It's from Skutt but the use of a sitter is the same regardless of what make kiln it is on.

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