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glaze test for oil spot, cone 6 ox.

updated fri 14 jun 02


Alisa Liskin Clausen on thu 13 jun 02

Glaze tested on white midrange stoneware fired in electric oxidation to =

Source: Clayart
Credited to:

Firing ramp:
100c p/h to 600c (212f - 1112f)
150c p/h to 1100c (330f - 2012f)=20
100c p/h to 1220c (212f - 2228f)
cool down max. per hour to 900c (1652f)
hold for one hour at 900c
shut off kiln

4.91 EPK
78.86 Feldspar
5.48 Whiting
10.75 Gerstely Borate

Note: All raw materials are measured up or down to the nearest whole =
decimal. =20
Colorants or additives to a 100 gram test batch are measured in precent =
to the 100 gram test batch.

Substitutions: Frit 623 for Gerstely Borate

Results: A black, glossy, smooth glaze, but no oil spotting. Maybe on a =
larger test surface, some oil spotting would occur.
Note: Mary Barringer's Metallic Black (archives) is a thickly coating =
metallic black glaze that has oil spots. I did not know
that is what the blue irredescent spots and streaks are called when I =
first tested it. It has proven to be a good glaze through several =
firings on larger

Regards from Alisa in Denmark =20

Jim V Brooks on thu 13 jun 02

the colorant was left of this recipe.