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Firing Disaster? Fired For 20 Hours - 9 Hour Soak?


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Ugh, just UGH!

I had a huge load to fire for a very important community project.

Using a Cone 4-6 stoneware and Cone 4-6 glaze.

Normally I fire to cone 5 and let it soak for 5 minutes.

The kiln was almost to temp when I left for work this morning. (yes, I know, never leave a kiln, but I couldn't be late to work and the basement is all concrete and it was supposedly almost done)

It should have been cool and ready to unload when I got home.

instead, at the top of the stairs, I heard it. "cu-lick"

"Rats.  I thought to myself, I must have a rat in the basement, I would LOVE to have a rant in my basement because if that's not what it was... CU-LICK."

Yes, my 10.5 hour firing went 20 hours.

It appeared to be stuck at 2112 degrees.  All three segment lights were lit.

I don't know if a relay went out, if an element broke or what, but it appears to not have reached cone and just held shy of cone 5 for 9+ hours.

What's killing me right now is wondering how bad it is inside.  Are the pieces ruined, stuck to the shelf or in a gooey puddle at the bottom (that's probably not likely)

This was the ONE time I didn't use witness cones because the thing was jammed so full I didn't have the space.

The thing is still WAY too hot to consider even taking a quick peek.

For the next several hours, I have nothing to do but obsess because this was a VERY important load (yeah, because that's how it happens) If in fact they aren't ruined and I can get them out by 4:00 AM, there is hope.

So let's play a game...

So Brain Trust.  If in fact this was a 9 hour soak below the cone I was firing to,  how bad is it likely to be?

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Many decades ago on another planet I was around a runaway electric fire-The kiln was not mine but it got way hot as the sitter misfuntioned-The pots all ran and the whole mess of glaze soaked into the floor. After a good long cool down the fellow inloaded it threw all the contents away including shelves and since the floor was a glaze mess so he  took the kiln apart flipped the floor rebuilt the kiln and it worked great for many years.

This was really a huge disaster and in the long run it only most likely only shortened the element life a tad.

I had a one in the 70's stick during a bisque and it went to cone 2-8?? no harm just really hard pots headed for the trash can.

Sounds like yours will not be as bad.Let us know when you peek.


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"If a cone is soaked at a temperature near

its equivalent temperature, it will

continue to mature, form glass and bend.

The time for the cone to bend depends

on several factors and as a general rule, a

1 to 2 hour soak is sufficient to deform

the next higher cone number. A soak of

4 to 6 hours will be required to deform

two higher (hotter) cones."



You might already be doing this math but it's something I can share. I've unfortunately had to do the math and it's not much fun waiting for a kiln to cool knowing something is very wrong.


Here's hoping you can share some happy accidents!

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Thanks everyone (even if it's not good news)

I'm going to try to sleep for a couple of hours, then get up, crack the lid and see at least what the top shelf looks like.

It's a small kiln (a Paragon TNF) so it won't stay hot for days.  I usually cools fairly quickly and I've had no trouble with crazing or pinging.

I used all my crazy, gooey, highly reactive glazes on this one too...


I'm still holding out hope for a miracle that these are "happy accidents" that can still be used for the intended project (i'ts super important and means a lot to a lot of people)  a little weird is OK.

In the absence of a miracle, I'd like the kiln to not be badly damaged.

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SOunds like you need to link a timer to your kiln and set it for a little longer than you know it wil take to fire the load.. You will of course know this from your firing log!

Good luck, lets hope it is just a shelf grind and re kiln wash jobbie. Go out and buy a timer and get it installed to automatically turn off electricity to your kiln for, "I never, but I have just" scenarios in the future.

Post pics to scare us out of our lethargy or complacency..


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Awwww CelticRose, I'am ver curious what you'll find inside your kiln. You could be our "how-not-to-do-it" example. I will cross my fingers that you still can use everything that's inside, but I really don't know what happens when you fire that long. Let's wait and see.

I think you need a hug!



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It is probably little consolation, but in a bisque firing last year I had a pot blow up on the top shelf.  A small shard wedged itself just under the cone of the kiln sitter preventing the shut-off bar from dropping when the cone sagged. I was there watching this happen...and I still over-fired the headed-for-the-dumpster batch.  When these things happen, you just have to chalk it up to learning-experience and move on.


I'm with the rest here, keeping my fingers crossed for you,


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I had one relay fuse on for 12 extra hours before, had 6 out of 10 elements on. I think the kiln must have stuck around 1100 degC for those 12 hours as it was that temp when I found it. I was firing to 1260 so it held much lower than the top temp.


Glaze actually came out really nice but it was only a transparent that turned slightly matt. Maybe it will be a happy error.

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I had ONE chance to get these out where they were going this morning.

I woke up every hour on the hour to lift the kiln lid a bit then it to allow heat to escape but not allow cold air in. (yeah, I know fast cooling is bad, but I was already facing the worst and this was important, oh so important)

AT 3:30 AM, I was able to open it.

I got lucky,  damn lucky.  Beyond damn lucky. 

This was part of a huge community art project where we hide themed art for the public to find on Chinese New Year.  It's normally just glass art, but this year other art forms were added including pottery


This is why it was so important; the drop was this morning and this was the final load.

The glaze colors are off from the over firing, but no one will know.

Only three pieces did any minor shelf sticking but those were with my super squirrelly glaze.

Here's a quick photo as I was heading out the door at 0' Dark Stupid


To see why this was so important, you can read the comments here.



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The controller was hitting 2111-2112 when I got home and that's about where it was when I left in the morning, so not "quite" a cone 5 soak.

and I don't recommend it...  (I swear that incident took years off my life)

I'll do some diagnostics this weekend and will take the earlier advice to add a shutoff timer. 

Monkeyshines Karma...  had to be....  couldn't disappoint the community.

If you are on twitter and search the hashtag #monkeyshines you'll see how happy our community is.

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It was the cone 5 program, with a 5 minute hold (the hold time I prefer over 9.5 hours)

I did have a shelf fall and crack a brick during loading so it's possible that messed up an element.

When I finally get some sleep and am no longer a danger to myself and others, I'm going to check the wiring to the relays and the elements.

If nothing looks fried/broken/weird, I'll do a fast test fire, pop the lid and see if all of the elements are the same color red then go from there.

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