LaReneM on tue 28 apr 98
I asked a question late last week about a problem I was having with my pieces
suddenly and loudly cracking after they come out of the glaze fire. Thanks to
Diana Pancioli of Eastern Michigan University, I now know that this is
dunting.
I had seen the recent thread on dunting but didn't see a definition of what
dunting was in those posts, so didn't pay much attention. I even tried
looking it up in a few books but I couldn't find a definition there either.
In any case, now I know!
Diana had several suggestions but what worked for me was to slow the glaze
fire down. I have started using witness cones again, and those showed that I
was not over-firing so that was eliminated as a possible problem. It also
seems to happen most often in partial loads, which makes sense as the kiln
would heat up more quickly with less mass to heat. So it was a good if
expensive lesson to learn about doing partial loads.
Thanks, Diana, for revisiting an old thread for me!
Cheers,
Kathy
Midland, Michigan
Nils Lou on wed 29 apr 98
Dunting is not caused by rapid firing. It is usually a result of UNEVEN
cooling. If you fire to maturity at 300 degrees rise per hour you can cool
at the same rate or even faster. If you have a slow cooldown and then a
rapid increase dunting may occur. If you want to experiment, fire to
whatever cone you normally fire to and then open all ports and damper. At
red heat (1200 F or so) open the door. No dunting will likely occur. It is
the uneven cooling that causes dunting. By uneven I mean ANY temporary
rise in temp in the cooling cycle. If it cools at a steady, even rate
there will be no dunting. Nils
On Tue, 28 Apr 1998, LaReneM wrote:
> ----------------------------Original message----------------------------
> I asked a question late last week about a problem I was having with my pieces
> suddenly and loudly cracking after they come out of the glaze fire. Thanks to
> Diana Pancioli of Eastern Michigan University, I now know that this is
> dunting.
> I had seen the recent thread on dunting but didn't see a definition of what
> dunting was in those posts, so didn't pay much attention. I even tried
> looking it up in a few books but I couldn't find a definition there either.
> In any case, now I know!
>
> Diana had several suggestions but what worked for me was to slow the glaze
> fire down. I have started using witness cones again, and those showed that I
> was not over-firing so that was eliminated as a possible problem. It also
> seems to happen most often in partial loads, which makes sense as the kiln
> would heat up more quickly with less mass to heat. So it was a good if
> expensive lesson to learn about doing partial loads.
>
> Thanks, Diana, for revisiting an old thread for me!
>
> Cheers,
> Kathy
> Midland, Michigan
>
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