mattness in the glaze, or crystallizing out of the glaz
and causing opaque crystal formation on the surface.
This is a commonly induced characteristic of glazes
and produces what is called a fluxr-matt glaze.

A similar situation can exist if excess silica is put
into the glaze. If there are insufficient fluxing
materials for it to combine with, its refractory nature
will result in unmelted particles lying inertly in the
glaze, resulting in a etlica matt surface. Kaolins

and ball clays bring a high proportion of silica and
alumina to the mixture (80%-90% of the material is Si0,
and Al 203).

SUBSTITUTION

The formula was then further investigated by straight
substitution of materials. If G-200 was used in the
basic formula, then the glaze was retested using the
same amount of as many feldspars as were available in

the sodium (example: nepheline syenite , potassium

(example: K-200) and calcium range (example: Cornwall
ncaa

Clay substitutions involved the use of kaolins, ball
clays, albany, barnard, red art and local clays. The
full range of puxtag materials was also substituted.
Once again, many different and potential tests
appeared from this series of tests.

ADDITIONS

If the basic formula, for example, contained within

its hundred per cent 172 dolomite, additions of various
fluxes (example: barium, whiting. wollastonite, etc.)
in 5% increments, (up to 20% or more) transformed the
base into other workable glazes.

The opacifying materials such as tin,Opax, Superpax,
Zircopax and titanium were tested. The composition of
the basic glaze seemed to control which of the opacifying
agents produced the most satisfactory result. No single
material surfaces as "the winner".

Line blends of single colouring oxide additions were

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