Firing

cone 10 oxidation

One glaze seen in two different firings. The two firings:

Firing profile One

Up Fire profile

150 deg F an hour to 250 deg F

400 deg F an hour to 2050 deg F

120 deg F an hour to 2250 deg F

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

Down Fire Profile

Two hour hold at 1900 deg F

A half hour hold at 1750 deg F

A three hour hold at 1700 deg F

A one half hour hold at 1650 deg F

Firing profile Two

Up Fire profile

150 deg F an hour to 250 deg F

400 deg F an hour to 2050 deg F

120 deg F an hour to 2270 deg F

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

Down Fire Profile

A half hour hold at 1750 deg F

A three hour hold at 1700 deg F

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

A one hour hold at 1650 deg F

The extra 3 hour hold at 1900 deg F of the first firing is the primary difference between these two firings.
Diverse crystals grow in saturated iron glazes, each with its own principle temperature for initial formation and
growth. As these crystals compete for components in the glaze, the formation early of one crystal may preclude the
latter formation of a competitor.

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

Each plate has a leaf image produced by embedding a leaf in the wet glaze, waxing, folowed by removal of the leaf
then staining the print with a thinned contrast glaze.

The plate in the second firing shows a more varied pattern of micro-crystalline growth.

glaze composition

Emperical Formula satIron_ZG_0:

K2O        0.1
Na2O        0.49
Li2O        0.19
CaO        0.16
MgO        0.06

Al2O3        .59
Fe2O3        .2

SiO2        3.14
P2O5        .04

molecular percent Silica 63 %

The plates are ~ 9 inches in diameter.

plate with firing One

plate with firing Two