Glaze Application Thickness

cone 10 oxidation

Firing profile

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

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 cones show this as a cone 10 firing.

This glaze, as all the glazes in this family of glazes, with names mashiko_something, are sensitive

to the glaze application thickness. Many different effects are possible, yet the transitions are sufficiently sharp

that it is difficult to reliably get any one of the possible effects on even most of a pot.

                                                                 From thin to thick, these glazes pass through the stages:
glossy nearly transparent dark greenish brown
semi-gloss dark brown with satiny silver texture
satiny to glossy silver ground with matte dimpled oil spots
volcanic gunmetal with both bits of gloss and large bubbles, some broken

These transitions are not discrete, the glaze will pass through a variety of intermediate stages. I have focused on

reliably producing the silvery ground with oil spots form of this glaze. Achieving an application sufficient

to generate oil spots without producing the volcanic frothed bubble look has been difficult. I show the glaze mashiko_Z18_1

in the two states, volcanic mess on the inside of the bowl, and dull silvery ground with dimpled matt oil spots.

These views are the inside and outside of one pot. The thicker inside glaze application is

less than a third thicker than that of the outside of the pot.

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

glaze composition

Emperical Formula mashiko_Z18_1 :

K2O        0.14
Na2O        0.14
Li2O        0.12
CaO        0.20
MgO        0.40

Al2O3        .87
Fe2O3        .22

SiO2        5.4

molecular percent Silica 72 %

bowl is ~ 4 inches in diameter

glaze mashiko_Z18_1

Left inside and Right outside

Remarks

As noted, the inside of this bowl has a somewhat thicker glaze application than the outside, and passed over the threshold
from dimpled with silvery background to volcanic mode with bubbles.

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