KEMPB on fri 20 sep 96
I have a student who is working with a sculptural body made up of
stoneware clay 3, fine grog 2, ciment fondu 1. It works well, sets up in a
couple of hours and has the advantage that you can come back to it
months later, dampen it, and add more wet mixture to it. Even very thick
pieces fire very well. When dry it can be worked with rasps, grinders etc
and so far the student has been applying a surface finish of a combination
of waxes.
Now for the problem. Whenever she tries glazing, no matter how thickly
the glaze is applied, when the piece comes out of the kiln the glaze has
soaked right into the body and has virtually disappeared. She has tried
"sealing" the body with slips but this has not really helped. The body is
obviously not vitrified. She has done tests with many variations of the
base formula but all her porosity tests are round the 18 - 25% mark.
We could fire higher but because we work a Cone 7 system this means
she will have to wait until she has a complete kiln load and time wise this
is a problem. Does anyone have any suggestions as to how she might
improve the vitrification at Cone 7.
She is considering adding (a) granite dust (b) silica (c) soda feldspar
(d) nepheline syenite (e) substituting some stoneware clay with
earthenware clay
Any suggestions ??????
Brian Kemp. Singapore
kempb@nievax.nie.ac.sg
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