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glaze test for purple opal, cone 6, oxidation

updated sat 29 may 04


Alisa Clausen on fri 28 may 04

Glaze test for Purple Opal, cone 6, oxidation.

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)
5 min. soak
cool down max. to 800c
Hold 1 hour
Shut off kiln

14 Gerstely Borate also tested with Frit J
30 Spodumene
5 Kaolin
7 Dolomite
13 Talc
20 Silica
6 Rutile

1.0 Manganese Dioxide

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 percent =
to the 100 gram test batch.

A yellow brown glaze.
No surface or color difference with G.B. or Frit J.
I realize that I have tested this recipe with Colemanite as well.
Non of my tests have yielded any opalescence or blues.

For Blue ADD
1-2% Cobalt oxide
4-6% Copper Carb.

A darker version of the above, with no visible difference in the G.B. or =
Frit J tests.

Regards from Alisa in Denmark

Mayssan Shora Farra on fri 28 may 04

Hello Alisa:

I have a recipe called the same , same igredients , alittle different

15 G.B., 34 Spodumene, 6 Kaoline, 8 Dolomite, 15 Talc, 22 flint, + 6 Rutile

It does give a hony brown color by itself.

But when it was given to me it was to be dipped on the top third of the pot
OVER other glazes (so far it worked with every glaze I have) and that is
when you see the opalesence and the runs and blues.

It is one of my favorite glazes as an accent. it also is great on the
inside of shallow bowls (always over other glazes). but I dont' use it on
inside of functional anymore since I have not had time to test it's
stability, especially since it would be different according to which
glaze/glazes are under it.

Thank you for all the practical information you post.