gsomdahl on mon 8 oct 07
I have several bowls that were wood fired that were quite dry on the
interior. I glazed the interior with an ^06-^05 commercial clear glaze
and re-fired to ^05. This worked well giving me a surface that was
acceptable to the touch. I also tried this with a deep soda fired
bowl that had a dry interior at the bottom. The bowl had a fair amount
of orange peel on the rim descending partway down the interior. When I
re-fired with the ^06-05 glaze it came out fine but two weeks later the
orange peel started breaking down with a white powder forming on the
surface. It's as it the soda is re-forming and migrating to the surface.
My question is: what's going on?
If I re-fire to ^10 what will happen to the ^06-05 glaze? Will it affect
other pieces if the kiln? Is the shard bucket the best place for the bowl?
--
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Lee Love on mon 8 oct 07
On 10/8/07, gsomdahl wrote:
> I have several bowls that were wood fired that were quite dry on the
> orange peel started breaking down with a white powder forming on the
> surface. It's as it the soda is re-forming and migrating to the surface.
> My question is: what's going on?
Maybe. What I do with unglazed pots is put a thin coat of shino
on the inside, leather hard, right after I trim and stamp. Applying
at leatherhard helps insure a thin coat.
--
Lee in Minneapolis, Minnesota USA
"We are not afraid to entrust the American people with unpleasant
facts, foreign ideas, alien philosophies, and competitive values. For
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--JFK
http://mashikopots.blogspot.com/
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Ivor and Olive Lewis on tue 9 oct 07
Dear G. Somdahl,
You tell us...<but two weeks later the
orange peel started breaking down with a white powder forming on the =
surface. It's as if the soda is re-forming and migrating to the surface. =
My question is: what's going on? >>...
It is experiences such as yours that illustrate our ignorance of Basic =
Chemical Science and raise fundamental questions relating to the =
Chemistry of Vapour Glazing. In the absence of basic research we rely on =
those who write books of articles for the Studio Pottery audience for =
information.
Your assumption is possibly a good summarisation of the situation. I can =
think of no better way of explaining your observations without knowing =
the exact composition of your clay.
Refiring work done with clays that mature at Cone 06/05 at cone 10 may =
be a recipe for disaster and the loss of kiln shelves. I would keep your =
specimens and continue to observe them.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
gsomdahl on wed 10 oct 07
Ivor and Olive Lewis wrote:
> Dear G. Somdahl,
>
> You tell us...<> orange peel started breaking down with a white powder forming on the surface. It's as if the soda is re-forming and migrating to the surface. My question is: what's going on? >>...
> ...
>
> Your assumption is possibly a good summarisation of the situation. I can think of no better way of explaining your observations without knowing the exact composition of your clay.
>
The clay is ^10 stoneware.
> Refiring work done with clays that mature at Cone 06/05 at cone 10 may be a recipe for disaster and the loss of kiln shelves. I would keep your specimens and continue to observe them.
>
The work is ^10 fired with a thin ^06-05 glaze brushed on for a second
firing at ^05. Right now the bowl is on my "may fire again when I get
enough" shelf . I know I'll get some re-vaporization of the soda at ^10,
but what I want to know is there likely to be out-gassing from the low
fire glaze or will it just puddle in the bottom of the bowl?
Thanks everyone,
Gene
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