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clayart digest - 15 nov 2007 to 16 nov 2007 (#2007-305)

updated mon 19 nov 07


Snail Scott on sat 17 nov 07

On Nov 16, 2007, at 11:00 PM, Automatic digest processor wrote:

> Date: Fri, 16 Nov 2007 15:22:18 -0500
> From: Jackie Shaw
> Subject: Clear, matte glazes
> Hi All,
> I am a novice at glaze mixing, but have mixed several successful glazes
> from recipes (MC6G and others). I would like a CLEAR, buttery or satin
> matte glaze, ^6, for use on stoneware...

Satin or matte glazes will never be truly clear. That's because of
the matte-ness itself. It is caused by tiny crystals which form in the
glaze as it cools. The effect is a bit like a sandblasted sheet of
glass -
it's still the same mixture as it was when it was clear, but the
passage of light is disrupted by the texture and and the glaze looks
less transparent. The more matte it is, the less clear it will be; no
around that.

> Can the base glaze of ANY recipe be used as a clear glaze? Or might
> some
> of the basic ingredients--or combinations of them-- make it opaque?

Depends on the recipe. No everyone designs a glaze to be clear if
used without any additives, and materials which make it not-clear may
be included in the recipe because they also act as fluxes, for instance.
What makes something a 'base' glaze is that the person who created
the recipe uses it with various additives to get differing results. It
never have been their intention that the 'base' recipe result in a clear
glaze, though that is often the case.


Ivor and Olive Lewis on sun 18 nov 07

Dear Snail Scott,

I agree with your summation of the principles associated with a Base =

In a practical sense, Magnesium and Calcium oxides in small quantities =
that would not destroy transparency or create surface texture do have =
significant and beneficial effects. Their major influence, as a "flux" =
seems to be to alter the viscosity, which they decrease and surface =
tension, which they enhance, of a silicate melt,

If Jackie Shaw can find a balance between the two extremes using Talc =
and Wollastonite as additives to one of the transparent glazes given in =

Best regards,

Ivor Lewis.
South Australia.