Chapter   Topic
% Molecular Parts Triaxial Graphs - Overview
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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.

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 and on the
  • IMC Web site

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.


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:


% Analysis Triaxial Graph
Overview | Matrix % Analysis Triaxial Graph | Displaying Oxide Eutectics