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Joseph F

Upcoming 300th Firing - Kiln Repairs

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I use an Omega 1/4" diameter Type K, in their High Temperature super Omegeclad protecting tube.  Go to www.omega.com, go to temperature than to thermocouple, go to product finder and look at (*) QXL.  The one I use is KQXL-14G-7 @$35.00  The -7 is custom and 7 inches long. Standard lenths are 6 ",12",18" I get way over 150 firings, and when they fail it is immediate because of the small gauge wire in the protecting tube.

David

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Well I fired yesterday and opened my kiln today. I over-fired by a full cone. I just did my usual cone 6 schedule with a 10 minute hold. Either my hold of 10 minutes was too much or I need to adjust TCs. In the past that worked fine, but I have been working on old elements and old TCs.

I am going to fire to cone 6 tonight again with shelves and some old pots I don't care about just to fill the kiln with mass. I will do no hold and no slow cool just to see how much exact heatwork my cones got, will that give me a good idea of how much to adjust my TCs?

At least it was nice and evenly overfired hah.

Edited by Joseph F

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Before adjusting anything, do a straight cone 6 without a hold, using cones, to see where you're at. Adjust from there.

In my experience, new thermocouples tend to fire hotter. It's not necessarily that you're over-firing, but rather that you were firing hotter than you were used to on the old thermocouples. The decline is gradual and you sometimes make adjustments as you go, then when you get the new TC's it jumps back to how it was at the start before the adjustments.

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@GEP, @neilestrick

Okay. I should have been more clear upfront.

I always fire with cone packs anytime I adjust my schedule.

Here are some pictures:

Old cones with same schedule before my elements started firing uneven, three shelves usually : 

59f0fc0001ede_oldcones(Copy).jpg.f0fcb96204193aa56bac14d26eb360d5.jpg

New cones with same shelf setup and same firing schedule:

59f0fc47b41ea_newcones(Copy).jpg.80e1969085715eb08ef3098e4fbd6ff4.jpg

Yes these are pats and not self supporting. I make sure they are all pretty much exactly the same angle when I put them in. I do about 50 of these at a time with them on a table all lined up so I can look down the rows of them.

5 is in the front, 6 middle, 7 back.

I already have loaded up 3 more shelves with some test pots and test tiles of my usual glazes with cone packs again.

I am about to fire the following schedule:

150F/h to 220F
400F/h to 2032F
108F/h to Other: Cone 6 (no holds)
175F/h to 1700F. ( no holds)

A pretty common schedule I used to fire all the time. I know this is reliable as I used it when I was beginner because I read the 175F thing from you Neil.

Do you think this will work for testing my TCs? I am willing to do whatever you think I should do. I figured this is simple schedule.

Thanks for your help!

Edited by Joseph F
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2 hours ago, neilestrick said:

Yes, test with that. But if you want the full effect of slow cooling go all the way to 1500.

Will do.

Firing going now. I will post cones tomorrow.

Edited by Joseph F

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Okay. Cones out. I opened a little early because I wanted to know! Here are the results. The cones in the front are the new cones(from last nights adjusted firing), the cones in the back are the cones from the previous firing. 

Results look pretty close to the same. Bottom looks less over-fired and the middle looks more. I am guessing this is due to the mass in each area or something. But overall still overfired on every shelf. 

What should I do!? Adjust TCs or cone offset?

59f1feeb03eeb_IMG_20171026_112413(Copy).jpg.88716c56fa05f52858b86ebea069b8a3.jpg

Edited by Joseph F

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Maybe adjust both. The middle is running a little hotter than the top and bottom, so you could adjust the TC there by 5 degrees to start. Then do a cone offset so the whole thing runs a few degrees cooler, maybe 10 degrees.

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I only have two TCs! It is just a small easy 18 with one in each section. I know the middle always runs a little hotter than the other areas. I usually make up for this with taller things in the middle or doing a stagger stack of half selves. That being said I will just do the offset as I should have explained that earlier. Sorry about the confusion.

I will adjust and fire again tonight. I am going to replicate same shelf placement again. Not going to stagger stack the middle yet. I would rather get it as close as possible with the full shelves.

Thanks for your help Neil. 

 

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Neil is the kiln expert but isn't that cone 7 tip touching? Just going by my experiences 10F degrees wouldn't be enough to bring it down enough so it's cone 6 tip touching. Are you aiming for higher than ^6? Maybe I'm missing something here. Also, if your middle is firing hotter I find you actually need to put shorter pots there so the shelves are closer together thereby creating more mass, results in slower heating up therefore not as overfired. Be interesting to see with your little kiln if 10F does it.

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Just the tip and only for a minute.

I used to prod cones into lumps of clay. Somebody taught me to sit the cones on a flat surface and jam two clay sausages either side so the bottom of the cone is flush with the kiln shelf. Feels slightly more accurate way to get the right angle.

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I would rather be on the cool side of cone 6 than a hotter side. My current glazes like the cooler side of 6 better.

As far as the shelves. I always though taller meant more even distribution between the top and bottom TCs. But the more mass makes sense. I usually stagger stack to avoid all this anyways. But lately I have been using full shelves to get more stuff in there.

 

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7 minutes ago, High Bridge Pottery said:

Just the tip and only for a minute.

I used to prod cones into lumps of clay. Somebody taught me to sit the cones on a flat surface and jam two clay sausages either side so the bottom of the cone is flush with the kiln shelf. Feels slightly more accurate way to get the right angle.

This is a good idea. I will do this next time I make those packs.

 

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Joe make sure that the height of the cone is set to 2" above the clay pack and is at the proper angle.  An easy way to get the 2 " is that the crossbar of the Orton symbol is exactley 2 " to the tip of the cone and will be at the top of the clay pack.  

David

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Thanks for the tips David. I usually get the self supporting kind, but my supplier was out and I didn't feel like ordering them. 

I am not to worried about the cone packs being off. I can tell my glazes are overfired, so I know the cone packs are reading close to accurate. There is a noticeable difference in fluidity between my pots from before and after.

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I made sure of that part. Neil confirmed touching tube. I unscrewed the holding screws and pushed until I heard. "Tink!" So I know they are touching. Firing going. Other: Cone 6. No hold!

I won't be home until late tomorrow, have class, so I won't get to update everyone's massive anticipation until then. :D

Thanks for everyone's help.

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3 hours ago, Min said:

Neil is the kiln expert but isn't that cone 7 tip touching? Just going by my experiences 10F degrees wouldn't be enough to bring it down enough so it's cone 6 tip touching. Are you aiming for higher than ^6? Maybe I'm missing something here. Also, if your middle is firing hotter I find you actually need to put shorter pots there so the shelves are closer together thereby creating more mass, results in slower heating up therefore not as overfired. Be interesting to see with your little kiln if 10F does it.

Yes, you're right. I wasn't looking clearly and in a rush. So yes, more than 10 degrees. It'll take some testing, though, I wouldn't drop it 100 degrees all at once.

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5 minutes ago, neilestrick said:

Yes, you're right. I wasn't looking clearly and in a rush. So yes, more than 10 degrees. It'll take some testing, though, I wouldn't drop it 100 degrees all at once.

Too late. I already set CNOS to 9099.  :ph34r:

In reality I did set it to 15 degrees cooler. Like I said I would rather be on the cooler side of 6 than hotter. My main glaze is better when it hits a cool cone 6. 

I already had a CNOS on there of 9030. Apparently I had an over firing issue before that I had forgot about. I started going through my emails with L&L and he instructed me to adjust it to 9030. After we did the same stuff we did here. I can't believe I didn't remember this in the first place. 

 So I moved it further down to 9045. I don't know what the deal is but my kiln seems to like being hot. I am going to get some self supported cones next time I take a trip to my clay supplier just to check all this again. Either way firing is going now. So we will see if 15 is good enough or not. Dun dun dunnnnnnn..... thanks again.

 

Edited by Joseph F

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7 hours ago, David Woodin said:

Since your T/C's were in protecting tubes than all that black stuff must still be in the tubes.  I would remove the protecting tube and shake it out to be certain.

David

Somewhere in this topic there is a video of that!

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19 hours ago, High Bridge Pottery said:

Just the tip and only for a minute.

I used to prod cones into lumps of clay. Somebody taught me to sit the cones on a flat surface and jam two clay sausages either side so the bottom of the cone is flush with the kiln shelf. Feels slightly more accurate way to get the right angle.

And quicker to make?

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