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major over fire in Skutt kiln.


char wheat

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My Skutt kiln has been in storage for the last 6 years because we were living in an apartment and I had no way to work in clay there.  A year ago we bought a house with a back yard shed just  big enough for me to make it into a studio.   A couple of weeks ago my son brought the Skutt kiln home and set it up on the patio.  I had enough pieces ready to fire.  I loaded the kiln and set it for a cone  5,  medium speed and a 10 minute hold. The last time I went out and checked the kiln it was at 1675 F degrees. Everything was doing fine and the rate of climbing degrees seemed to be right on schedule.  This morning when the kiln was opened. We found a not so pretty site.  The top shelf had sagged in the middle which allowed pieces to go to the middle as well and to join up with other  pieces.  The next shelf down had the cone 5   orten cone pack.  The cone five orten  cone had melted down into a puddle. completely flat.  As we unloaded the kiln we found two more kiln shelves that were really sagging in the middle. The kiln also has several messages flashing on the screen,  error 6,  error 17, and the word fail, along with  another number and letter one.  All  four of the kiln shelves were badly warped. The kiln had seriously overly fired.  Most of the pieces were attached to other pieces, some possibly can be salvaged but most were a lost cause. Is there anyway to salvaged the warped shelves? I know I should have checked on it more often and kept checking through the night. But I fell asleep in the recliner and didn't wake up until after the kiln had stopped rising in temp and was in fact going down.    It was then around 400 degrees. Still too hot to open.  I had an appointment to get a surgical implant in my back so it wasn't until later in  the evening before we could open the kiln. Any advice on how to save the kiln shelves and \or why the kiln over  fired this time.  This kiln has been a very reliable kiln before it was put into storage.  I did vacuum the kiln before firing.  I left the peeps out and cracked the lid for the first 300 degrees. I then put in 3 of the peeps and closed the kiln lid leaving one peep open for the rest of the firing.  .   Any ideas for why this happened and/or how to fix it. would be very appreciated. Thank you all.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             

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This is a really horrible learning situation!

An independant timer which shuts power to kiln About 15 to 30mins after estimated finish time really worth the investment.

Nor much in way of warped shhelces can be salvaged. Hopefully elmements not destroed too

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1 hour ago, char wheat said:

had enough pieces ready to fire.  I loaded the kiln and set it for a cone  5,  medium speed and a 10 minute hold.

Sounds like it has an automatic controller which should have a setpoint and safety setting as well. Neither can be exceeded. Which control do you have? This should be rare as even if the programming was bad it should hit the safety limit. Now as to how hot, your best evidence is your cone 5 mostly melted. Cones are made of glaze and about four to five cones beneath their melting point which would put your firing guess at about cone eight to nine. Shelves are no longer good, and at cone nine I wouldn’t think they should Not warp actually so that is a bit of a mystery.

Fail can indicate bad thermocouple, any chance failed shelf landing on thermocouple didn’t cause the whole thing?

Which control do you have? Kiln model?

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It would be very unusual for the controller to be the cause of the problem, however it is possible. First double check the firing program and make sure you didn't program it incorrectly.  Error 6 shouldn't result in an over-firing, since if the TC leads were reversed then the error code would show up within the first few minutes of the firing as the temperature readout went down instead of up. There is no error 17. And I've never seen a controller display more than one error code, so that's odd, too. It's also possible that you had sticky relays or a bad thermocouple or thermocouple connection that caused the over-firing. A flickering TC input can do all sorts of goofy things to the controller as it attempts to function with a jumpy input. I suppose it also could have been the perfect storm of more than one issue.

The shelves are scrap. You can't un-warp them. You should also inspect the bricks and elements for damage.

What model kiln is it?

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Now I thought (The shelves are scrap. You can't un-warp them) maybe in one of those old star treks. Scotty said warp drive-so just maybe and its long shot maybe they could straighten out during a warp drive event . If you have some navy contacts some submaraines can also have warp drives

Just spit balling here

You may also have some 1st class yard art as well.

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I wonder if you may have inadvertently set the hold to 10 hours not minutes and such a long hold at such a high temp created the error conditions. I did that once and had to just turn the kiln off instead of a controlled cool down when I saw it come up with 20:00 instead of 20  but was standing there waiting for it to complete and start cool down.

So sorry this happened to you. Can't tell you how many times over the past dozen years I have been tempted to just go to bed when I started the kiln so late in the day and it was scheduled to end in the middle of the night. I have thought about using the alarm but I have been known to sleep through alarms unless they are around the time I am used to getting up anyway. The one thing that has always kept me honest is as an IT boss for the past 30 years I have always preached to anyone that would listen that your hard drive will fail and the only question is when. Everything breaks eventually.

Good luck with the repairs. I hope at the end of the day its just the shelves. This post will help to continue to be vigilant and always be in front of that kiln until flashing complete and dropping temp.   

edit: full disclosure, I might have used an alarm in the early years just can't remember but not since I slept through my alarm several times for early fishing trips. Getting old changes stuff like that :-)

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