Marianne Lombardo on fri 20 dec 02
I read a line or two in a recent message about something else, that
mentioned bowls becoming oval-shaped due to firing too close to the kiln
elements.
I recently had two bowls that were perfectly round after the bisque fire
(^04), but after the glaze firing (^6) came out of the kiln oval-shaped.
Not a true oval, but definitely distorted. I was disappointed because they
were thrown perfectly and dried properly before the bisque firing, and I've
trying to figure out what happened before I make any more.
During the bisque firing the bowls were stacked inside each other. For the
glaze firing I believe I had two bowls on one shelf, each bowl having one
side within maybe 2" of the elements. The opposite (side?) of the bowls
being in the centre of the round shelf . Both sides of the two bowls were
pulled out into a bit of an oval shape.
Would this have been what happened? Why would *both* sides of the bowls
distort?
Marianne Lombardo
Omemee, Ontario, Canada
email: mlombardo@nexicom.net
Ron Roy on mon 23 dec 02
Hi Marianne,
You have to imagine - at the top of the firing - clay is soft - if one side
is heated more than the other - and for a longer time - we can expect
distortion. Fast firing tends to make this happen by the way.
Having said that - if both the inside and outside sides are pulled in then
I have to think there may be another reason. If feet are not trimmed evenly
that will cause distortion - if the foot is only touching the shelf in two
places - when the clay gets soft it will try to flatten out - casing the
rim to distort - if the ware - especially bowls - are on a bent shelf the
same thing will happen.
Hope this helps you figure it out - let me know if it doesn't.
RR
>I read a line or two in a recent message about something else, that
>mentioned bowls becoming oval-shaped due to firing too close to the kiln
>elements.
>
>I recently had two bowls that were perfectly round after the bisque fire
>(^04), but after the glaze firing (^6) came out of the kiln oval-shaped.
>Not a true oval, but definitely distorted. I was disappointed because they
>were thrown perfectly and dried properly before the bisque firing, and I've
>trying to figure out what happened before I make any more.
>
>During the bisque firing the bowls were stacked inside each other. For the
>glaze firing I believe I had two bowls on one shelf, each bowl having one
>side within maybe 2" of the elements. The opposite (side?) of the bowls
>being in the centre of the round shelf . Both sides of the two bowls were
>pulled out into a bit of an oval shape.
>
>Would this have been what happened? Why would *both* sides of the bowls
>distort?
>
>Marianne Lombardo
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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