Why think of glazes in terms of their formulae rather than their recipes?

Unit 4 Topic 8
The Unity Formula

Glazes may be very easily compared and manipulated when they are expressed as unity formulae.
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Because the raw materials in recipes may be complex each containing a variety of different oxides, comparing the potential qualities of recipes before firing is very difficult. Two very different looking recipes may, in fact, be glazes which are similar when fired.

This similarity can be revealed by looking at the oxide analyses of the recipes expressed as unity formulae.

Recipe A
NZ Feldspar
Whiting
Wollastonite
Silica
61.40
7.55
8.77
19.26

Unity Formula
KNO
CaO
0.3
0.7
Al2O3
0.4
SiO2
2.6

This is the unity formula for both Recipe A and Recipe B

 

Recipe B
Australian Feldspar
Whiting
Microwhite Clay
Silica
40.21
16.47
10.42
32.89

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