Alisa Liskin Clausen on fri 14 jun 02
Subject: Glaze test for Oil Spot, cone 6 ox.
Glaze tested on white midrange stoneware fired in electric oxidation to
1220c.
Source: Clayart
Credited to:
Firing ramp:
100c p/h to 600c (212f - 1112f)
150c p/h to 1100c (330f - 2012f)
100c p/h to 1220c (212f - 2228f)
cool down max. per hour to 900c (1652f)
hold for one hour at 900c
shut off kiln
Recipe:
4.91 EPK
78.86 Feldspar
5.48 Whiting
10.75 Gerstely Borate
ADD
4.13 Cu. carb,
4.13 Manganese diox.
2.07 Cobalt ox.
Note: All raw materials are measured up or down to the nearest whole
decimal.
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
pieces.
Regards from Alisa in Denmark
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Ron Roy on thu 20 jun 02
Here is the same glaze using f3134 instesd of GB - if anyone feels like
testing it let me know if it needs some adjusting.
G200 spar - 70.5
F3134 - 13.0
Dolomite 2.5
Whiting - 3.5
EPK - 10.5
Total 100.0
Without the colouring oxides it could be a stable glaze - maybe - there is
an awful pile of alumina and silica in it for a cone 6 glaze so I am
thinking it may not melt well enough - without the colours to be stable -
I'd sure like to know how it tests out with 5% copper carb at a lab.
If you are going to put it where it will be in contact with food at least
to the lemon test - I'd like to know if it changes colour - that is a lot
of copper, cobalt and manganase - I sat it's going to change colour in use.
RR
>Source: Clayart
>Credited to:
>
>Firing ramp:
>100c p/h to 600c (212f - 1112f)
>150c p/h to 1100c (330f - 2012f)
>100c p/h to 1220c (212f - 2228f)
>cool down max. per hour to 900c (1652f)
>hold for one hour at 900c
>shut off kiln
>
>Recipe:
>4.91 EPK
>78.86 Feldspar
>5.48 Whiting
>10.75 Gerstely Borate
>
>ADD
>4.13 Cu. carb,
>4.13 Manganese diox.
>2.07 Cobalt ox.
>
>Note: All raw materials are measured up or down to the nearest whole
>decimal.
>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
>pieces.
>
>Regards from Alisa in Denmark
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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