surface. Again, a variety of systems were used and it
was necessary to investigate in the text books, the
funetions and/or qualities that the materials bring to
a glaze.

TYPES OF MATT GLAZES

Those using clear and satin glazes also attempted
to develop matt surfaces by:
a) increasing the proportion of silica until they
achieved a silica matt glaze;

b) increasing the proportion of alumina (in the clay
content of the glaze formula) until they achieved an
alumina or clay matt surface;

c) increasing the fluxing portion of the formula to
oe a flux matt surface (i.e. dolomite, whiting,
etc.

This was done by adding a series of 5% increments to
the base glaze of 100 gms. until the glaze surface
became matt. Results were sometimes achieved with
five to ten per cent additions, but the majority
required fifteen to forty per cent additions. The
clay or alumina matt was the easiest to achieve, but
the surface quality variations of the flux or silica
matt tests made this experiment worthwhile.

With reference to obtaining silica, clay and flux matt
glazes if 15 necessary to understand that silica,
kaolins, ball clays and many of the fluxing materials,
on their own, do not meZé or form a glass at the
temperatures at which most potters work.

John Reeve states it well in his book on glazes.
"There 7s an ideal proportion between silica and the
fluxing materials which causes the lowest temperature
melt. This point of balance is called the eutectic.
Less flux, than the eutectic in the mixture causes
less melt. More flux than the eutectic in the mix-
ture doea not cause more melt. The flux in excess of
the eutectic does not enter into the glass making, but
lies within the glass inertly, acting more as a re-
fractory (resistant to heat) than flux, thus causing

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