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In a 1986 edition
of the British magazine Ceramic Review (#97 - 100) Mike Bailey and
David Hewitt, two potters who work in Wales, published articles
in which they described a method for "Understanding your
Glaze Tests" which involved the technique of plotting the
% molecular parts (or alternatively the % Analysis) for the glaze
on a triaxial graph.
Fig.1
% Molecular Parts Triaxial Graph |
The corners
of the graph (Fig.1) represent
- 100%
of basic(flux) oxides
- 100%
Amphoteric oxides and
- 100%
Aacidic oxides.
By dividing
the three sides into equal parts, 0 to 100%, the percentage
composition of any point within the triangle can be determined.
The X
in Fig.1 plots the position of a glaze with the % molecular
parts of 30% Basic, 40% Amphoteric and 30% Acidic oxides.
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The theory behind
this appraoch to glaze analysis is explained fully in the Ceramic
Review articles which have also been reproduced on the internet
at
- David Hewitt's
Web site http://www.dhpot.demon.co.uk and on the
- IMC Web site
http://digitalfire.com/education/people/hewitt.htm
Matrix
Facility for Displaying a % Molecular Parts Triaxial Graph
Matrix provides
the facility for displaying such a graph in a seperate window. The
design for this facility is taken directly from the articles by
Hewitt and Bailey.
Individual glazes
can be displayed on this graph. Matrix will perform all of the necessary
calculations converting the Seger formula for the glaze into a %
Molecular Parts expression.
Sets of glazes
previously stored in recipe databases on disk can also be displayed.
Matrix will
zoom in on the upper part of the graph providing a more detailed
view where usually most of the action takes place.
This graph may
also be printed to a hard copy.
Eutectics
A fundamental
principal underlying this type of glaze analysis is the concept
of eutectics.
Matrix will
display eutectic patterns on the graph for the K2O, Na2O, ZnO, CaO
and MgO oxides indicating the lowest melting point for these oxides
in conjuction with specific levels of amphoteric and acidic oxides
(e.g. Al2O3 & SiO2).
The theory associated
with interpreting glazes against a background knowledge of these
eutectics is explained in David Hewitt & Bailey articles and
at David Hewitt's web site.
Follow
these links for more information about:
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