multicolored glazes with spots

These spotted glazes are near neighbors of satIron_ZG_1O_0

The surface of this glaze is covered in metallic micro crystals.

full view

bowl is ~3 inches in diameter

Glaze satIron_ZG_1O_0PAl

This glaze has multicolored regions, black leopard spots, and no metallic micro crystals.

The heavily glazed bottom of the pot is nearly black. The glaze application was thicker at the bottom of the pot, though it also flowed.

satIron_ZG_1O_0PAl contains more more alumina, and more MgO.

full view

bowl is ~3 inches in diameter

Glaze satIron_ZG_1S_1

This glaze also has a few multicolored regions, including black, and even a few metallic micro-crystals.

It contains more Phosphorus.

full view

bowl is ~3 inches in diameter

Glaze satIron_ZG_1O_1Q_1PFe

This glaze also has few multicolored regions, including black, and no metallic micro crystals.

Some alkali metal is replaced by MgO; additionally, this glaze contains less Alumina and more Fe2O3.

full view

bowl is ~5 inches in diameter

The design is created by adhering a mask and then applying the main glaze. After drying, the entire pot is
coated in wax, then the mask is removed and the open area filled in with a second glaze.

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 2300 deg F with a hold of 20 minutes at 2300 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

Initial glaze

Empirical Formula satIron_ZG_1O_0 :

K2O        .25
Na2O        .24
Li2O        .24
CaO        .17
MgO        .1

Al2O3        .52
Fe2O3        .21

SiO2        3.2
P2O5        .05

molecular percent Silica 64%

Glaze with increased alumina and MgO

Empirical Formula glaze satIron_ZG_1O_0PAl :

K2O        .23
Na2O        .23
Li2O        .26
CaO        .14
MgO        .14

Al2O3        .6
Fe2O3        .24

SiO2        3.2
P2O5        0.03

molecular percent Silica 63%

Glaze with increased P2O5

Empirical Formula glaze satIron_ZG_1S_1 :

K2O        .16
Na2O        .40
Li2O        .21
CaO        .14
MgO        .09

Al2O3        .52
Fe2O3        .2

SiO2        3.2
P2O5        0.12

molecular percent Silica 64%

Glaze with decreased alkali metal, increased MgO, Fe2O3:

Empirical Formula Glaze satIron_ZG_1O_1Q_1PFe

K2O        .24
Na2O        .22
Li2O        .24
CaO        .16
MgO        .14

Al2O3        .47
Fe2O3        .3

SiO2        3.2
P2O5        0.04

molecular percent Silica

Remarks

These spotted glazes are near neighbors of a metallic microcrystalline glaze.

The rate of movement of the components in a glaze determines the size of growing crystals by limiting the number
of arriving particles. That is, the liquid matrix composition influences the migration rate of glaze components.
Therefore, a more viscous glaze generally results in smaller crystals.

Change the composition of the glaze, and the relative proportion of the various colored regions changes.
Each component has its own distinct migration rate, which is differentially affected by the
compositional change in the glaze.

These glazes are near relatives of the glaze satIron_ZG_1O_0, having high alkali metals, high iron and containing phosphorus.
Each has somewhat higher viscosity than satIron_ZG_1O_0, as shown by the waxy matte surface of these glazes.

The near neighbor glazes of a crystal growing glaze, are likely to manifest related,
though less flamboyant, artifacts of phase separation.

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