Charlie Cummings on thu 5 oct 06
I had a similar experience with a poorly designed gas kiln. We had
to blast the pots with the kiln's oversized burners to get the
temperature to rise. The Shino pots that boiled seemed to be in
parts of the kiln that got very hot with very heavy reduction.
Charlie Cummings
At 11:45 AM 10/5/2006, you wrote:
>We have noticed on many occasions that, in our wood kiln, a glaze like
>Shino Pearl becomes bubbly when overfired, say to cone 11 or more. At
>first we thought this looked underfired, but it has happened so many
>times in the HOT spots in our wood kiln, that we are positive it is OVER
>fired. We've seen similar results with other shino glazes too, but
>Shino Pearl does this the most, so it may provide a clue. Other glossy
>glazes, like celadons, do not boil, and just get a bit runny. So we do
>not think this is the clay. Of course we try *not* to overfire, but the
>kiln sometimes fires unevenly, usually in the back where we cannot
>observe the cones.
>
>Can anyone tell us what might be happening in a shino that would cause
>out gassing at temperatures above cone 11?
>
>TIA
>
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Charlie Cummings Clay Studio & Gallery
4130 South Clinton Street
Fort Wayne, IN 46806
Charlie@claylink.com
260-458-9160
www.claylink.com
Paul Herman on thu 5 oct 06
Matt,
We once experienced bubbly shinos on the floor area of the anagama.
Lots of ugly blisters.
I suspect it's not overfiring in your case, because having seen
shinos that got extra hot, there were never blisters as far as I can
remember.
Our bubbles were in an area of the kiln that didn't get a strong
enough reduction atmosphere in that particular firing. There was a
coal pile just in front of the bubbly area, and I think it blocked
the heat from reaching that section of floor.
The only explanation I could come up with is decomposition of iron
oxide, the same phenomenon that gives oil spot glazes their spots.
In subsequent firings, we are careful to keep that coal pile burnt
down, and plenty of flame running along the floor. The problem hasn't
appeared again.
Good luck,
Paul Herman
Great Basin Pottery
Doyle, California US
http://greatbasinpottery.com
On Oct 5, 2006, at 8:45 AM, Matt MacIntire wrote:
> Can anyone tell us what might be happening in a shino that would cause
> out gassing at temperatures above cone 11?
>
> TIA
>
Matt MacIntire on thu 5 oct 06
We have noticed on many occasions that, in our wood kiln, a glaze like
Shino Pearl becomes bubbly when overfired, say to cone 11 or more. At
first we thought this looked underfired, but it has happened so many
times in the HOT spots in our wood kiln, that we are positive it is OVER
fired. We've seen similar results with other shino glazes too, but
Shino Pearl does this the most, so it may provide a clue. Other glossy
glazes, like celadons, do not boil, and just get a bit runny. So we do
not think this is the clay. Of course we try *not* to overfire, but the
kiln sometimes fires unevenly, usually in the back where we cannot
observe the cones.
Can anyone tell us what might be happening in a shino that would cause
out gassing at temperatures above cone 11?
TIA
Lee Love on fri 6 oct 06
On 10/6/06, Matt MacIntire wrote:
>
> Can anyone tell us what might be happening in a shino that would cause
> out gassing at temperatures above cone 11?
Try adding kaolin.
--
Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
"When we all do better. We ALL do better." -Paul Wellstone
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