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fw: glaze spalling with bottle blue

updated fri 3 dec 10

 

Edouard Bastarache on thu 2 dec 10


Shivering is a glaze defect in which slivers or flakes of glaze detach
themselves from a pot. When shivering occurs, it is most frequently seen on
thin rims and edges.
Reasons for Shivering
Shivering is usually due to the exact opposite situation that causes
crazing. The glaze coat is too large for the pot.

Imagine a small table covered by a larger piece of fabric. If the fabric wa=
s
not allowed to overlap the edges of the table, it will buckle, wrinkle, and
fold. The same thing can happen to a glaze as it cools, if its coefficient
of expansion is too small in relationship to the coefficient of expansion o=
f
the clay body. However, since the glaze is much more brittle than fabric, i=
t
will shiver.

Another possible reason for shivering is over-reduction, especially of red
clay bodies that are more susceptible to carbon coring. Gis,

Edouard Bastarache
Spertesperantisto

Sorel-Tracy
Quebec

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