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I wish I got my pyrometer a day earlier. I don't like the way this kiln sitter cone looks at all. It was a bisque fire to cone 04 but the cone looks a bit crispy. Usually they just bend but the color doesn't change much. This one is burnt black. (see pic). I can tell that the hazelnut stoneware did not fire to full temp because it's still too red as it should be but it may be bisque higher than I'd like. I had four types of clay in there. Jack Troy Wood fire Porcelain, Jack Troy Wood fire stoneware, Cone 6 Porcelain and cone 6 Hazelnut Stoneware. I have other previously fired bisque pieces downstairs, maybe I'll give them a tap with a screwdriver and see if they sound the same. What could happen if the pieces were bisqued to too high a temp? 

-Mary

cone.JPG

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Wow, I just had the same bisque firing problem, and I am wondering what might have caused this to happen? Anyone else out there have any ideas? My Kiln Sitter has been working fine. I'm firing to cone 05, and the cone doesn't look crispy, it just looks melted, see the pictures. I also provided a picture of what the cone for my last firing looked like. The other question I have is that the pieces from this firing came out tan/brown, not red/orange like typical bisque, so it seems clear to me they have gone past the point of bisque for Raku? 

Terry

 

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Hi Terry, 

Sorry to see this happened to you too. I assumed the cone for some reason got stuck to the metal supports of the kiln sitter preventing the top bar from dropping properly and shutting off the kiln at the right time. I have since read that you should coat those supports with kiln wash to prevent this, so I have done that and am now moving ahead with the glaze firing fingers crossed that the pieces come out ok. Forever the optimist! LOL. Also now I have a Pyrometer to keep track of the temp in my kiln so I can shut it down myself if the kiln sitter fails to do so at the correct temp.

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Yeah, weird problem, never had this happen to me. Thanks for the info about the cone getting stuck, not sure how that would happen, kinda makes sense, but I'm also wondering if there was just some kind of issue with the cone itself? Like a "bad/defective" cone? Never really heard of that either, but I guess it might be possible. I have a Pyrometer, might be time to mount it on my electric kiln when I do my bisque firings, or, just do a test fire to see if there are any problems with the kiln sitter.

Cheers, 

Terry

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Just a heads up... When I got my Pyrometer it said not to mount on kiln as that gets hot and would affect the reading. Mount on nearby surface away from the kiln. I got an analog one so I just sit it on a table next tot he kiln and put the thermocouple part through the peephole. That seams to have worked out well as I was not looking forward to a complicated installation process.

Edited by GreyBird

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Thanks for the replies, the cones have never gotten wet. I found this info at the Orton Cone website:

When a Kiln-Sitter® cone or bar does not bend or melts into a blob, the problem is generally related to the Kiln-Sitter®.  The cone will melt as the kiln is heated, but it bends due to the sensing rod’s downward pressure. If the firing continues too long, the cone will fully melt into a blob.  Some reasons for sensing rod failure include improper adjustment of the Kiln-Sitter®, a bent or corroded sensing rod or Kiln-Sitter® assembly or an object inside or outside the kiln interfering with the sensing rod’s movement. To help prevent these problems, the Kiln-Sitter® should be periodically tested, checked and adjusted using the firing gauge supplied with the device.

I'm going to check out my Kiln sitter and do a test firing.

Cheers, 

Terry

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Mine was a brand new box of cones so hadn't gotten wet either. My kiln sitter rod seams to be moving up and down freely so I don't think that is the issue. I got the kiln from a woman in her 70's 20 years ago and she had been a potter her who'll life so the original firing gauge that probably came with the kiln sitter is long gone. Thanks to google I can probably find out what they are talking about though. Terry, if you find anything would you post it? Would be good to know that everything is working properly :)

Thanks!
best,
-Mary

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Hi Mary, 

More info: In the Skutt Manual it says the sensing rod may be the issue. It says continued operation at high fire temperatures will eventually cause the end of the rod to deteriorate or bend. And that this will affect the adjustment of the trigger and claw. If the the rod is bent it must be replaced. I fire to cone 05 most of the time.

I took the sensing rod out of kiln sitter and, of course it has a slight bend to it. I ordered a new sensing rod online just to play things safe and will put the new one in when I get it and do a test firing.

That's all for now, 

Terry

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As Maraku has suggested, is it possible to get a bad batch of cones from the factory?  Never heard of that before but it sounds a bit too coincidental that it is happening to two people at once?   No doubt Edward Orton would be rolling over in his grave to contemplate such a thing...  wonder how Hermann Seger would be reacting?...  

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you can get a gauge which you use adjust how the rod is positioned in relation to cone, and the angle that the shut off "flap" sits to the vertical

as stated above, the rod changed, gets thinner with firings and can affect the dropping mechanism, resulting in overcooked cones.

a shelf position right next to sitter can stuf it up as well.

 

a "sticky drop flap" or incorrectly angled flap with all the above can cause a sitter to malfunction.

worth getting a gauge

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53 minutes ago, curt said:

As Maraku has suggested, is it possible to get a bad batch of cones from the factory?  Never heard of that before but it sounds a bit too coincidental that it is happening to two people at once?   No doubt Edward Orton would be rolling over in his grave to contemplate such a thing...  wonder how Hermann Seger would be reacting?...  

Hi Curt, I don't think it was a bad batch of cones because my cone was a different type than Terry's. Mine was a triangular shape and Terry's was a rod shape so I assume they were different batches. Also I have used other cones from the same box without incident.

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I think a test cone in the fire (large cone) would tell you what temp you really got to. Next time put one in on shelve next to kiln setter. That way you know what temp it went to and how to proceed. Either with a setter adjustment or something else.test cones are always a good idea .They take the guess work out .

Edited by Mark C.
Pres and GreyBird like this

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WOW, I am so glad I got that pyrometer! Ceramic Arts Daily sent out an article called "Techniques and Tricks for electric kiln" which of course I read right away. It noted a firing schedule and explained how to do a controlled cool down even with the manual kiln sitter. Very exciting since I didn't know that could be done... but of course it can, right?!

The schedule is:

1st Segment:     50°F/hour to 220°F
2nd Segment:   250°F/hour to 2167°F
3rd Segment:   150°F/hour to 1500°F

Pre-Pyrometer I would turn all switches to low for three hours, then all to med for 3 hours then all to high until kiln sitter turns off kiln. Witness cones told me I was reaching correct temp.

This morning I started firing at 5am with a room temp of 65°. I am monitoring and noting temps every hour via pyrometer. After one hour with all switches on low the temp in the kiln is 600°! Yikes. There are four switches so I turned, counting from bottom up, 2nd and 4th switches off to slow things down a bit. It's good to know what's going on in there! :)

In case anyone is interested in the controlled cool down part of the article, it says: Allow the kiln sitter to turn off the kiln and leave it off for about 20 minutes. Then use a combination of med and low switches to create gentle heating as the kiln cools. Shoot for 1 to 2 hours on Med. Then 1 to 2 hours on Low. Try for 125° to 175° per hour.

 

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Check the kiln/setter to see that it is level, and the setter is perpendicular to the floor. I had a setter that was attached over two kiln sections. If one of the kiln sections was slightly out of line it would cause the bar of the setter not to drop thus not shutting down the kiln.

 

At the same time, I would shift over to bars next time you order cones. Bars are much more consistent in the way you put them in, as they are same thickness across.

 

best,

Pres

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Just fired a load today. First load with the pyrometer. Such a huge difference. I controlled the rise of the temp with the four front kiln dials. I logged the temp every hour, and I used a bar cone 7 which turned the cone off at exactly 2200°. Well, it's analog but it looked to be 2200° :) Took 12 hours to fire. 

Also good to note... dabbing kiln wash on the kiln sitter rods seamed to have done the trick. 

 

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well cones reflect heatwork done.

pyrometers measure temp at a specific spot in kiln.

firing schedule will affect both

test cones on each shelf paint a better pic.

could be a life time of study when you add how your glazes perform.......and the rest

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Well, the learning curve on this stuff is "expletive" brutal. This whole kiln load was a bust. The problem is now I don't know if it was the botched bisque firing or the new firing schedule, or both. I do know the kiln fired to cone 6 because the witness cones were perfect with the 7 cone still standing and the 5 & 6 cones bent over. The stoneware clay body looked way too dark like it was "over cooked".  The glazes had all sorts of issues.... crawling, pitting, running... color was off all around. Just awful. As I. unloaded the kiln I wavered between utter disappointment and excitement to start again and get it all right. The biggest thing I learned here is you have to really enjoy the process. If you live for the results you will never make it through the learning curve! LOL.

Can someone tell me if this firing schedule looks out right? It did take 12 hours total to fire which seamed very long in comparison to what I've done in the past:

1st Segment:     50°F/hour to 220°F
2nd Segment:   250°F/hour to 2167°F
3rd Segment:   150°F/hour to 1500°F

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