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Babs

What Happened?

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Babs    385

Relatively recently I was firing  to C6 when an element was ruined by some glaze dropping onto it, flaking glaze syndrome, however as I was on a tight schedule and with optimism unfounded, I continued to fire, thinking that at some time before the exhibition this kiln would reach the temp. required. I fired for a night and a day and a night, old kiln, no computer controls, remember them??, and then tired and with temp at 1070 Celsius, I turned it off.

Rang hte other people in ex. to relate that my work would be quite diminished in number..  Isolated, new element some days/weeks away.

Opened the kiln to beautifully matured glazes!

I remember reading an article "Guan but not forgotten" where the potter related that he was firing stoneware glazes at around C6

What is going on, Heatwork?

Should I try to repeat this??  

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Biglou13    202

C6 is 1185 Celsius (ish)

 

My vote is for heat work.

 

I've been studying bizen pottery ......long firing cycles. Lower temps yet higher temp maturity. So yes it is highly probable heat work is maturing you glazes and clay.

 

Did you have any witness cones in firing? Is your clay also maturing/vitrifying?

 

Some times you get extraordinary responses from unusual situations.

 

My 2 cent vote is for yes try and repeat it.

And fix flaky glaze.

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JBaymore    1,432

Ceramic materials react to a combination of the application of heat energy over a certain amount of time.  Cones measure this combination at the location of the cone.  Pyrometers only measure instataneous temperature at the location of the probe.  The impact of the time and heat energy factor at the elevated end of the cycle is the significant part of this equation, so your described scenario is perfect for showing this impact.

 

So your results are likely the impact of the heatwork as biglou says. 

 

But there may be other factors at work here also.  You are saying "beautifully matured glazes".  Like most studio potters I am assuming that you are saying this simply because "they look good" when you opened the kiln.  I'm also going to bet that maybe you have never stopped a kiln firing of these particular glazes a bit short of your desired end point in the past.  I wonder if you had done so.... if they would not visually look about the same as what you saw here.  Maybe the glazes have a bit wider range than you think they do for a certain visual effect.

 

best,

 

.....................john

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neilestrick    1,381

I would not try to repeat it again. You're wasting a ton of electricity firing that long. Chances are the heat work was in your favor, but it's an awful long time to fire to get to cone 6. If you did in fact reach cone 6 (which I don't think you did since the sitter (assuming there is one on the kiln) didn't shut off the kiln), reaching it slowly probably helped your glazes look better. The best way to mimic that in a much less wasteful manner is to fire to cone 4 and hold temp until cone 6 is reached. However that's incredibly difficult to do with a manual kiln.

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Babs    385

Thanks everyone.

I glaze fire to c03 and c5/6

I have placed a pot with the above mentioned glaze in the lower firing by mistake and did not get this result ie dull unfinished look.

Yes I did write beautiful... my relief at having soome pots was in that subjective description!

The cost factor would not allow me to repeat this with this glaze but, if say, I did this with a C9/10 glaze and as John adviced slow down thelast part of the firing then I would be tempted, had a couple of glazes from that range in the past which I would like to still go to.

Never got to C6 , 1080Deg Celsius top temp but don't know cone   C6 in sitter. still doing its thing.  going up 10 degs an hour for a lifetime it felt.

Yes the gods were with me or at least pitied my bleary state.

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JBaymore    1,432

I have placed a pot with the above mentioned glaze in the lower firing by mistake and did not get this result ie dull unfinished look.

At cone 03 you would never see such close maturity.... but if you stopped at maybe cone 4 or 5 ...... you might see the results you saw.

 

best,

 

.....................john

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Babs    385

Thanks for the clarity John.

Have a few cool spots where I place wider fired glazed ware. My onglaze brush marks really do not integrate in to the glaze in these spots and the glaze looks a bit stiff so i figure that this glaze needs the C6 temp. in my long firing ordeal there were pots whose glaze did not make it, and so were refired.

What do you think would happen to my mid range clay if I were to subject it to the long firing needed to mature a C9 glaze?

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neilestrick    1,381

What do you think would happen to my mid range clay if I were to subject it to the long firing needed to mature a C9 glaze?

 

Cone 9 is cone 9, no matter how you got there. Your cone 6 clay would be over fired, and likely slump or bloat or both.

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