Which materials should be changed to reduce the amphoteric and acid content of the glaze?

Unit 3 Topic 7
Focus on Raw Materials

Decreasing clay and silica might lower the maturing range of the glaze.

Feldspar also contains R2O3 and RO2 oxides but reducing that material would also take out some of the most powerful flux oxides (K2O, Na2O).

In practice both an increase in flux together with a decrease in the amphoteric and acid oxides might be adopted to lower the maturing temperature of the glaze.

Recipe Quantity
Flux
Amphoteric
Acid
Feldspar
40
provides---> K2O, Na2O, CaO Al2O3 SiO2
Whiting
30
provides---> CaO --------- -------
China Clay
20
provides---> ------ Al2O3 SiO2
Silica
10
provides---> ------ --------- SiO2

To raise the maturing temperature of a glaze the reverse of the methods mentioned in this discussion could be tried.

Note: Raising or lowering the maturing range of a glaze using these
methods may alter it's textural quality if the material changes are too great.

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