search  current discussion  categories  glazes - chemistry 

coefficient of expansion.

updated sun 18 jul 99


Mike Bailey on sat 17 jul 99

Dear Greg,
As I understand the situation, a glaze should be under compression
(rather than tension). You ask about the ratio:

In some tests that I did with David Hewitt we found that:

A clay with a glaze whose RTE was 1/3rd that of the clay; shivered

A clay with a glaze whose RTE = the clay; fitted

A clay with a glaze whose RTE was 3 times the clay; crazed.

There seems to be a reasonable 'window' in which to operate!

However, there are many things going on in a glaze that aren't accounted
for in the mathematics. For example, we recently had a discussion on
CLAYART about the colouring oxides - they are great at cutting down on
crazing - an effect out of all proportion to the small change in the RTE
that the calculations would have you believe.


Mike Bailey.

Mike Bailey