Computer programmes such as MATRIX calculate the coefficient of
expansion for a glaze using the expansion
factors for each oxide and the values for that oxide in the
unity formula for the glaze. The individual oxide expansions are
then totalled to find the coefficient of expansion for the whole
glaze.
These calculations
are performed automatically in computer programmes so that you can
instantly see the new expansion factor for a glaze as you make changes
to either the recipe or the unity formula.
A unity formula
or a recipe may be manipulated to lower the coefficient of expansion
using the 'no crazing' benchmark for the clay body as a guide. Even
without such a benchmark a series of glazes (line blended) with gradually
lowering expansions can be created for testing to eradicate crazing.
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