iandol on fri 29 nov 02
Hello again,
Well, those glaze tests with high masses of Barium Carbonate have had =
eighty four hours under the Vinegar, longer than RR and JH suggest in =
their article.
A quick spot test suggests that there is no Barium in the vinegar and =
the surfaces of all of the samples are still polished bright, except for =
the ones which were already matt in the "As fired" condition.
I was intrigued by the fact that the base glaze used for the X 4 samples =
tile (25%, 30%, 35%, 40% Barium Carbonate), does not craze on the clay =
which is used for these tests. Furthermore, on the 6*6 tiles the only =
change made was to substitute Barium Carbonate for Kaolin on one axis =
and this has given cracking in all specimens. In strong contrast, the =
108 samples which used kaolin have not crazed. So Barium Carbonate seems =
to have done something to the Coef of Exp because there is extensive =
cracking through every sample.
Hope this information is useful to someone.
Best regards,
Ivor Lewis.
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