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^9 ox. teadust glaze test results - long

updated mon 5 feb 01


Bret Hinsch on sat 3 feb 01

Lately I・ve been studying a long article by Wu Peng-fei in the summer and
fall 2000 issues of the Taiwanese magazine :Taoyi; (Ceramic Art). Wu
gives very detailed information about making traditional Chinese teadust
glazes. The article includes color photographs of about 250 tiles showing a
huge range of teadust-type glazes. Using this treasure trove I recreated
some of these glazes at cone 9 oxidation with excellent results. I thought
that I・d share this information, since I know not many of you can read the
original article in Chinese, and there・s unlikely to be anything this
detailed about teadusts anywhere else. I found that teadusts are as easy as
they are beautiful. It・s a rare chance to create an authentic-looking
imperial Chinese glaze in oxidation.

Wu gives 25 different basic formulas for oxidation teadusts. Here are three
examples that I tested with great results.

Teadust #1
KNaO 0.15
CaO 0.55
MgO 0.3
Al203 0.25
SiO2 2.5

Teadust #8
KNaO 0.2
CaO 0.62
MgO 0.18
Al2O3 0.3
SiO2 3.0

Teadust #16
KNaO 0.3
CaO 0.5
MgO 0.2
Al2O3 0.35
SiO2 3.5

To each of these basic formulas, you need to add between 6-12% Fe2O3 and
1-2% NiO for color. I tried the entire range and consistently got the best
results with 10% RIO and 2% NiO.

In addition, Wu says that you can add an opacifier such as Sn (1-10%), Ti
(3-10%), or Zr (5-10%) to bring out more color.

Wu says that 1-5% bone ash will prevent the growth of micro-crystals on
cooling and bring out a bit of pale red in the glaze. He says that 3% bone
ash in a teadust can produce traditional Chinese crabshell or rice straw

Wu notes that 0.3-1% CoO can also bring out some extra color.

In addition, he ran a series of tests with various feldspars. He found
significant variation when he made the same recipe with different feldspars.

The secret ingredient to these teadusts is nickel oxide. Without it, these
glazes are just ordinary temmokus. But with 2% nickel, they develop
beautiful yellows and greens.

I recreated these three formulas with excellent results as follows.

Teadust #1 (^9 oxidation)

Potash feldspar 35
Dolomite 24
Whiting 5
Kaolin 9
Silica 27
Titanium dioxide 1
RIO 10
NiO 2

Teadust #8 (^9 oxidation)

Potash feldspar 41
Dolomite 13
Whiting 12
Kaolin 7
Silica 26
Titanium dioxide 1
RIO 10
NiO 2

Teadust #16 (^9 oxidation)

Potash feldspar 56
Dolomite 13
Whiting 7
Kaolin 2
Silica 22
Titanium dioxide 1
RIO 10
NiO 2

I really love these glazes. Have fun testing!

Bret in Taipei
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Joan Ashworth on sun 4 feb 01

All that research, final discoveries, tests, experiments, recipes, hints
and help - thank you very much. I will experiment to see how they work on
the edge of Africa.....

Joan Ashworth
deep in the Durban, South Africa, sauna