Norm on wed 1 apr 98
Hey Folks,
I have the recipe for a base ^6 ox glaze and want to know how to make it
a tenmoku. A black that breaks brown. Or Dark brown that breaks a
lighter brown. Here is the Base:
Flint - 20
Wollastonite - 20
EPK Kaolin - 20
Frit 3134 - 20
Custer Felpspar - 20
Would appreciate any suggestions or other additions for textures and
colors.
Thanks! Norm! 8^o
John Post on thu 2 apr 98
Norm,
Here are a couple of glazes that might be what you are looking for. The
first one is Gibby's Wild Rose Temoku. There was a great deal of
discussion about this glaze earlier this year on clayart. The second one
is a revised version that has increased silica to make the glaze more
durable. The results that these glazes give is largely dependent on your
claybody and firing schedule. The colors range from metallic/sparkly to
deep rusts and reds where the glazes break over edges. I'm not trying to
drudge up the former discussion about the expansion of these glazes, I'm
just passing them on. I personally have been having much success with the
second one over and under other cone 6 glazes.
I realize that I haven't yet directly answered your query about what to add
to your glaze. I have noticed that many cone 6 oxidation tenmoku type
glazes have red iron in amounts of 8-15%, bone ash 8-10% and sometimes
lithium carbonate and spodumene. You could try adding some of these things
to your base or just try altering some of these glazes until they work for
you.
Good luck
John Post
rp1mrvl@moa.net
Sterling Heights, Michigan USA
+++++++++++++++++++++++++++++++++++++
+++ Gibby's Wild Rose Tenmoku +++
+++++++++++++++++++++++++++++++++++++
***Note- the silica and alumina levels are not within the
expected/acceptable/safe limit formula range for a cone 6-7 glaze.
Date: 01/08/98
Cone: 6-7
Firing: 8-9 hours to cone 6, then a 1.5 to 2 hour soak on medium.
Lithium carbonate 95 9.5% Hazard!
Bone ash 95 9.5% Hazard!
Nepheline syenite 556.6 55.7%
EPK 158.4 15.8% Hazard!
Red iron oxide 95 9.5%
-------- ------
1000 100 %
===========================
Chemical Analysis
===========================
Na2O 0.27 Al2O3 0.54 SiO2 1.96
K2O 0.08 P2O5 0.08
MgO 0.00 Fe2O3 0.17
CaO 0.28
Li2O 0.37
Alumina:Silica ratio is 1.00 : 3.63
Neutral:Acid ratio is 1.00 : 4.10
Alkali:Neutral:Acid ratio is 1.00 : 0.54 : 2.22
Expansion coefficient: 91.3 x 10e-7 per degree C
Oxides causing abnormal expansion effects: Li2O
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++ Post's Variation of Gibby's Wild Rose Tenmoku +++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++
***Note - the alumina is a tad high according to the limit formula range,
but lithium is a strong flux. This glaze is quite glossy and not at all
matt which one might think if looking at the alumina level. This glaze has
passed a 3 day soaking in vinegar without any visible changes in appearance
or texture etc...
Range: 6-7
Firing type: Oxidation
Glaze type: Stoneware
Surface: Gloss
Date: 01/08/98
Firing: 8-9 hours to cone 6, then a 1.5 to 2 hour soak on medium.
Spodumene 2160 27 %
Frit 3110 2176 27.2%
EPK 1464 18.3% Hazard!
Bone ash 632 7.9% Hazard!
Lithium carbonate 272 3.4% Hazard!
Red iron oxide 632 7.9%
Flint 664 8.3% Hazard!
-------- ------
8000 100 %
===========================
Chemical Analysis
===========================
Na2O 0.23 Al2O3 0.54 SiO2 3.02
K2O 0.02 B2O3 0.03 P2O5 0.08
CaO 0.37 Fe2O3 0.17
Li2O 0.38
Alumina:Silica ratio is 1.00 : 5.62
Neutral:Acid ratio is 1.00 : 5.72
Alkali:Neutral:Acid ratio is 1.00 : 0.57 : 3.27
Expansion coefficient: 74.7 x 10e-7 per degree C
Oxides causing abnormal expansion effects: Li2O B2O3
>----------------------------Original message----------------------------
>Hey Folks,
>
>I have the recipe for a base ^6 ox glaze and want to know how to make it
>a tenmoku. A black that breaks brown. Or Dark brown that breaks a
>lighter brown. Here is the Base:
>
>Flint - 20
>Wollastonite - 20
>EPK Kaolin - 20
>Frit 3134 - 20
>Custer Felpspar - 20
>
>Would appreciate any suggestions or other additions for textures and
>colors.
>
>Thanks! Norm! 8^o
>
>
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