I have a number of varigated glazes with patterns in sharply contrasting colors, which I named calico for the fabric. One such Cooper_404_3 is shown below:
As with the other glazes in this series these glazes contain 1.5 % Nickle oxide.
I am curious as to the extent of the region in which these calico glazes occur.
My first foray is an investigation of glazes with similar alkali metal:alumina ratio, similar silica:alumina ratio, and higher alumina.
The alkali:alumina ratio of my existing glazes is near 1, as these glazes also have alkali:alumina ratio near 1 with higher alumina,
they will have less of some other bases.
Of the 5 glazes tested, the two glazes with lower Zinc showed almost none of the multicolored pattern.
Here I show the pictures of the glazes with patterns reminiscent of cooper_404_3. These glazes all had high ZnO.
The picture on the right is a close up.
The nickel blue is intense, one wonders if that color is attainable in a stable glaze.
Notice the bits of an amber transparent full gloss phase.
The dunting is likely attributable to high silica and alumina as a lower silica lower alumina version of this glaze has no dunting problem.
The picture on the right is a close up.
This glaze as cooper_404_1ZnPSiU above has a fully connected phase of transparent glossy amber out of which emerges a matt microcrystalline phase.
The base gloss phase is more visible in this glaze, than in the above.
Lithium replaces most of the potassia and soda in the above glaze, alumina and silica are nearly identical in these two glazes.
The result is a glaze in which the multicolored contrasting colored pattern is much diminished, though not gone.