analysis (UPA) used their trusty calculators to quickly
determine the UMF or the UPA of the glaze. If the mol-
ecular system was used - the question arose - did the
composition of the satin or matt glaze that was tested,
fall within the established range? If not - what mat-
erials were below or above, the established guidelines?
A similar decision was made by those who used the UPA
system. (See John Reeves’ text for Book One, A Potter’:
Way to Understand Glazes). Knowledgeable adjustments
could be made at this point.

N.B. If these skills are not part of your background,
understand at least the variety and proportions of ele-
ments that each material brings to the glaze structure.

1.€. Composition of Dolomite
54.8% CaQ (calcium)
44.0% MgO (magnesium)
trace amounts of Al,0. and Fe,0.
(alumina and iron)
Composition of Bell Ball Dark Clay
53.08% 310, (silica)
30. 38% A1,0.(alumina)
.36% MgO (magnesium)
.o1% Fe,0,(iron)
1.01% trace elements
With some understanding about what was actually in the
glaze, the students then proceeded with a series of

tests which challenged them to learn how to alter or
manipulate the glaze.

AREAS OF INVESTIGATION

If the glaze was clear, by altering the proportions of
the materials in the recipe or by adding one more mat-
erial, the students attempted to produce a satin or matt
glaze. If the glaze was matt, they altered it to fire
to a satin and clear glaze. If the glaze was satin or
waxy, they attempted to move it to a clear and to a matt

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