What changes to the materials of a recipe would lower the glaze maturing range?

Unit 3 Topic 5
Focus on Raw Materials

The maturing range of a glaze may be lowered by either:

  • increasing the flux content or
  • reducing the amphoteric and glass former

In each of the above alternatives the role of each of the raw materials in the recipe must be considered before changes are made.

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

In the recipe shown above it can be seen that the Feldspar and the Whiting provide flux oxides.

Feldspar and China Clay provide both Al2O3 (stabiiser) and SiO2 (glass-former) oxides.

The material silica in the recipe tops up the SiO2 (glass-former) oxide content of the glaze.


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