What results from excessive amphoteric oxides?

Unit 2 Topic 5
The Glaze Triangle
Excessive amphoteric causes a glaze to stiffen and tend towards opacity again giving texture to its surface.

These glazes are commonly called alumina matts as Al2O3 is the primary amphoteric oxide present in all glazes.

Glazes overloaded with Al2O3 can be very stiff and stable sometimes with pinhole defects. The suspended alumina forms crystals producing soft to dry surfaces depending on the amount in excess.

Too much alumina can inhibit the melting of a glaze to the extent that a poor quality matt glaze results which is prone to discolouration.

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