David Hewitt on wed 26 feb 97
I was very interested to read of Gavin's contribution and the reference
to using Ceramic Phase Diagrams.
Mike Bailey and I have been using this approach for many years now and
find it most useful in determining in which direction to adjust a glaze
recipe according to what one requires, shiny, alumina matt etc.. Most of
our work is at cone 8 or 9, but we are about to embark on a test series
for cone 6 glazes - without borax and with borax - in order to
illustrate the difference with cone 6 recipes and the effect of borax on
the triaxial phase diagrams.
I would be interested in hearing from anyone also interested in this
approach.
In message , Gavin Stairs writes
>
>From my slight understanding of how glazes work, it seems to me that the
>best bet to reduce the maturation temperature of a glaze without altering
>it's esthetic characteristics (leaving aside the question of oxidation vs.
>reduction) is to use a larger number of fluxes. The glaze program will help
>you to do this, but it won't tell you what the new melting temperature will
>be. The only way to do this more systematically (that I know of) is to go
>to the ACA Ceramic Phase diagrams for the mixtures in question, and try to
>understand the position of the high cone glaze relative to adjacent
>eutectics, and then to try to find a lower temp arrangement with similar
>structure. This is a lot of work, and you need to know how close to
>equilibrium the original was, and so forth.
>
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP6 1DQ, UK. Tel:- 01633 420647
URL http://digitalfire.com/education/hewitt.htm
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