Calico with higher alumina

firing to cone 10 in oxidation

slow downfire at 50 deg F an hour in the interval 1850 deg F to 1700 deg F

slow downfire at 25 deg F an hour in the interval 1700 deg F to 1650 deg F

One hour hold at 1650 deg F



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.

full view

glaze cooper_404_3 bowl 3 inches in diameter

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.



glaze cooper_404_1ZnPSiU

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.



glaze cooper_404_10_0

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.



glaze cooper_404_10_1

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.

full view



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