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gail's transparent glaze/slip question

updated wed 19 aug 09


lili krakowski on tue 18 aug 09

Gail writes (I edited):
My clear liner glaze over a piece slipped before the
bisque, [becomes]cloudy where thick--... I mixed 3
new 'clear' glazes Only one gave a really
clear cover--Kate the Younger from Lana Wilson's book. The others
were cloudy colored slip look[ed] pastel--or changed=3D20
color completely. The really clear (Kate) was very high gloss and it
did the most amazing thing to the slip: I had covered the piece (bowl
and platter) with an iron slip--painted on in 3 coats, in 3 different
directions. Under 'Kate' the iron slip became bright yellow and dark
brown streaks-- none of the other
clear glazes showed the brush strokes. This striation did not occur
with the clear glazes that became cloudy.=3D20


It would be helpful if you gave us the recipes of your glazes and of =3D
your slip.

Glazes belong in families. To the best of my knowledge most clear c.6 =3D
glazes arecalcium borate ones. That would mean that a glaze containing =3D
any of like ten frits all could be "exactly" the same. And if they =3D
contain colemanite, or Gerstley Borate, or one of the substitutes now =3D
made by several manufactuers--all calcium borate. These glazes tend to =3D
opalesce. In my (always limited) experience opalesce more often over =3D
iron. (One of the gurus can tell what causes the opalescing process . =3D2=

The body can contribute to the opalescing as can the composition of the =3D

I know how phony this will sound; but the slips did not change color. =3D
Could you peel the glaze and the interface back there is would be as you =
applied it. We do not see the color of glazes the way we see the color =3D
of walls. We are looking into and/or through a glass. If I looked at =3D
one of my pale blue denim shirts through sunglasses, or through a red or =
yellow bicycle reflector the color would not be pale blue, but the shirt =
remains so. It also is possible that Kate dissolves some of the iron in =
your slip and in the firing disperses it through itself. Leading to a =3D
pale yellow where there is little, darker where there is more dispersed; =
and/or that you now are looking through pale yellow "glass" at thicker =3D
and thinner slip layers below.

And a guess ventured till you give us the recipes. You say Kate is very =
high gloss. I gather as distinguished from the others. Which suggests =3D
that Kate is a bit, maybe a good bit, maturer than the others, which may =
make it "attack" the slip and clay underneath more, which may create a =3D
different (my guess is deeper) interface than the other glazes do.

Lili Krakowski
Be of good courage