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Am I Screwed?


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Ok, fired my first load in a new kiln and screwed it up. I have a Skutt 1027 and on my test load had it programmed for med speed cone 5 with a 20 minute hold. Cone 5 fully bent but 6 didn't even slightly bend. On a different kiln in my old studio we got a dead on 5 with 6 half bent with that program. It was like it didn't hold. Test tiles (in an empty kiln) did come out pretty much as I expected and looked fine. Still I figured I didn't get my hold and I want that for the heat work to even out the glazes. I reviewed the manual and erroneously concluded that I should have entered 20.00 instead of 0.20 so I made the adjustment and fired my first load. Well it hit temp while I was out of the studio and by the time I got back it had begun a 20 hour hold and had completed 47 minutes of that. The only way I could see to stop it was to stop the kiln.

 

So I now have what I assume with heat work a cone 7 firing with no controlled cooling. It dropped from 2170 to 1600 in about 2 hours and now has tapered off and cooling slower. Normally I think it ramps down in a controlled fashion to 1200.

 

Any input on what that extra heat work and faster cooling will do to my ware. Its porcelain and this was a Xmas load with almost everything in AMACO firebrick red with various accent glazes. My shop made glazes seemed to interact with the red in past loads so I try to run this glaze mostly by itself.

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Sorry to hear of your screw up.

 

I think the fast cool down is going to have an effect on how the iron red glaze turns out. If it's not too late I would enter a cool down ramp now to match what your previous successful ramp was. It's likely you will get more brown than red otherwise. If it's already thru that ramping down segments then you could try a strike firing after.

 

Since you only added 27 minutes to your test load hold time I would be optimistic that the glaze shouldn't have run much. No idea if you will get bloating with the clay but hopefully there is some allowance for overfiring.

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Is it an iron red for sure? Not stain? Depends on what pot forms you have as to how fast you can re-fire. Hope you get lucky and they are red. If the glaze is an iron red what you are trying to do is just recreate the time spent from approx 1300F - 1800F (those temps are ballpark). Crap shoot without testing first. Too many variables to guess at.

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In the initial firing: 1900-1980F is the prime colorant/crystalline temp range. In a strike fire (reheat after glaze), the common temp range to "alter" color is 1350F on the low side, up to 1450F on the high side. Strike firing is a common practice for crystalline glazes. The amount of titanium in the glaze plays a major role in how colors develop in a strike fire.

 

Nerd

 

Strike fire

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I'm so interested to hear what comes out of this kiln!

 

I can never resist a quick peek and the first few times I had Firebrick on the top shelf I was FURIOUS that it fired brown. I would close it back up and just fume for hours, thinking I applied it too thin. Well, the red appears as it cools. It literally goes from a dark brown with almost no red, to a deep cherry.

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Hey guys, all is well. Glaze stayed put with no runs, fired deep red as expected without any glaze flaws developing. I'm a happy potter as I've got three back to back Xmas shows starting Saturday and could ill afford to lose a load.

 

The cones by the way fired deadon 6 with the 7 slightly bent so the 47 minute hold at cone 5 registered a tad over a full cone of heat work. That surprises me as I expected to see the 7 at least half bent if not all the way which would have left me wondering if it approached 8. 

 

When I compare this firing to a cone 5 with 20 minute hold and controlled ramp cool down I can see no real difference. So the extra 20 minutes does not really seem to hurt or benifit with this particular glaze and the entire load was firebrick red. I guess I stayed in the parameters and all and all a pretty sturdy glaze.

 

Thanks for all the input and encouragement everyone, really appreciated and you all made me relax a bit about it and just wait and see b4 getting too bummed.  

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