Which oxides values in the unity formula indicate the maturing range of the glaze?

Unit 7 Topic 3
Using Unity Formula

The maturing range of the glaze is determined primarily by the amounts of SiO2 and also of Al2O3 in the glaze in relation to the strength of the oxides in the flux group.
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A comparison between the SiO2 and the Al2O3 values in the unity formula for the glaze, and the range of levels given for these oxides in the limit formula charts, or on the graphs, will give an indication of the maturing range of the glaze.

In the case of Nicki's Blue Celedon the limits graph shows that both the SiO2 and the Al2O3 levels are on the low end of the range for those oxides at C.12.

The low levels of stabiliser & glass-former indicates that the glaze will have a fluid melt at C.12 resulting in a tendency to run on vertical surfaces.

The flux to stabiliser & glass-former (Al2O3 & SiO2) balance is in tipped towards excessive flux content of the glaze. The glaze is not, however, seriously deficient in alumina and silica as a test firing would show.

Nicky's Blue Celedon

Oxide
Mol. Parts
KNO
CaO
MgO
0.30
0.55
0.15
Al2O3
0.31
SiO2
3.20
Al : Si
Expan.
10.32
10.58

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