Glaze Technical Page

Crazing

To illustrate the effect of adding a little extra silica to a typical stoneware glaze (Temmoku in this case)

Original Recipe

A variation made by adding 5% extra Silica

Now check out the impact on the expansion coefficient, it has gone down with the addition of only 5% extra silica. The silica to alumina ratio has gone up a little which may lead to a little shinier glaze, in this case since it'is presumably already shiny and this effect is may be unnoticeable.