iandol on tue 19 jun 01
Dear Forest,
Thank you for putting that point forward. I follow the same procedure =
that you have learned. It is a good precaution to adopt.
Your Teacher is correct in the sense that this pool of water keeps the =
clay at the centre of the base soft for an excessive time. Therefore, as =
the walls press inwards when they dry the soft clay responds by becoming =
thicker, but of a smaller diameter. Then when it dries the differences =
in stress between the outer and inner clay increases disproportionately. =
The additional stress provides energy which moves the clay, but there =
must be an entity from which the crack can initiate. If the material had =
a perfectly uniform structure it would not fracture.
Best regards,
Ivor
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