G1214Z1 is a cone 6 calcia matte glaze, it has very high melt fluidity, enabling a fine-grained crystalline matte surface to develop during cooling. A potter was steered to this recipe after finding that G2934 magnesia matte fired too variegated when stained blue. However, this failed a leaching test. So, she simply increased the SiO2 in the formula (as shown in this Insight-live screenshot of doing the chemistry). SiO2 is the glass that makes up the lion's share of all glazes, but in mattes it is minimized in favor of Al2O3 (which often comes at a cost of susceptibility to leaching). The new recipe passed the GLLE test for leaching and even enabled reducing the cobalt percentage! Notice there is a cost: She had to compromise the degree of matteness somewhat to get the more durable product (the Si:Al ratio is a factor in the degree of matteness).
| Recipes |
G1214Z1 - Cone 6 Silky CaO matte base glaze
This glaze was born as a demonstration of how to use chemistry to convert a glossy cone 6 glaze into a matte. |
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