Ivor and Olive Lewis on sat 4 oct 08
Dear John Rodgers,
Since you are firing on circular shelves I will assume you have a
circular kiln.
You do not say if the warp is on one side of the rim or whether it is
a multiple wave around the circumference.
My suggestion, if the warp is located as a dip on one side only would
be that heating is uneven. One edge of the rim may be nearer the
elements of the kiln and is overheating in relationship to the other
side.
There is always the possibility that bricks may have separated
allowing a slight draught. A chill of only a few degrees might prevent
the high side from settling as the rest of the clay matured.
Another point, you not say how high these plates are. I would allow
no more than half an inch head room from the rim to the shelf above.
A ploy I learned a long time ago when working to the limits of the
kiln was to place baffles around pieces to assist in getting even
heating.
I am sure a simple answer will come from someone.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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