Erratic in Line Blend

I show two line blends with the left end a textured, high CaO glaze, the right end a low CaO, high alkali metal saturated iron glaze.

Both Left end glazes are derived from glazes given as oxide weight percent by Nigel Wood in his book "Chinese Glazes".

A smooth transition between the ends of a line blend is unlikely if the ends are sufficiently disparate, as with our current examples.
A jump, a change in properties, is expected somewhere in the line from the discordant properties
of the two ends.

An "erratic" is the occurance of something belonging to neither end of the line blend, a jump on both sides. Continuity of
properties is missing in both directions.

Here I show two line blends in which crystals are seen in neither end, yet are visible in a middle tile.

Line Blend One

The Left end glaze is yuan_LSi, the Right end glaze is satIron_ZG_0

full view

Tile 4 with crystals enlarged

Line Blend Two

The Left end glaze is jingdezhen, the Right end glaze is satIron_ZG_0

full view

Tile 4 with crystals enlarged

oxidation firing to cone 10 in an electric kiln

Firing profiles

Up Fire profile

150 deg F an hour to 250 deg F

400 deg F an hour to 1800 deg F

300 deg F an hour to 2050 deg F

120 deg F an hour to 2310 deg F with a hold of 20 minutes at 2310 deg F

Down Fire Profile

300 deg F an hour to 1750 deg F then a half hour hold at 1750 deg F

300 deg F an hour to 1700 deg F then a Three hour hold at 1700 deg F

25 deg F an hour to 1650 deg F then a one hour hold at 1650 deg F

Clay body is a grolleg porcelain from Tacoma Clay Art Center.

glaze compositions

Left end glazes

Empirical Formula yuan_LSi :

K2O        0.28
Na2O        0.09
CaO        0.55
MgO        0.08

Al2O3        0.77
Fe2O3        0.01

SiO2        4.68
TiO2        0.02

molecular percent Silica 72%

Empirical Formula jingdezhen :

K2O        0.11
Na2O        0.01
CaO        0.76
MgO        0.12

Al2O3        0.61
Fe2O3        0.02

SiO2        4.54
TiO2        0.02

molecular percent Silica 73%

Right end glaze

Empirical Formula satIron_ZG_0 :

K2O        0.10
Na2O        0.49
Li2O        0.19
CaO        0.16
MgO        0.06

Al2O3        0.59
Fe2O3        0.20

SiO2        3.14
P2O5        0.04

molecular percent Silica 63%

Remarks

An erratic in a line blend is an anomaly, something unexpected, unconnected to anything seen in the two end member glazes.
A line blend crossing between unrelated glazes passes through the null region belonging to the region of influence of
neither glaze. With luck, one of the tiles of the line blend lands in this null region dominated by neither and will be
an erratic.

The "region of influence" of a glaze is comprised of glazes sufficiently close in empirical formula to bear
it a family resemblance .

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