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^10 oxidation glaze test results (way long)

updated mon 31 mar 97


Sam Cuttell on sun 9 mar 97

The following are glazes I have taken from Clayart and
fired to ^10 ox on Plainsman H550 clay (old batch).
I fired at 50% over night, up to 75% in the morning for
4 hours, then high till ^10 was almost touching. No
soak. Kiln kept closed tight for 16 hours - then
unloaded (I think that covers everything). Oh, and
^11 in sitter.

Please note that comments are _my_ observations of the
tests and as such, are very subjective.

Many thanks to those that submitted these glazes to the
group at large!!

Temple White

35 Custer Spart
19.7 Dolomite
2.6 Whiting
22.7 EPK
20 Flint
Suspender recommended.
Tested 97-1-16

White satin opaque glaze. Nice texture. Crazed like mad.

Nagamoto Teat (redux)

52 G-200 (it just said feldspar, so I picked one!)
21 Barium Carb (I subbed 15.75 Strontium)
10 EPK
9 Whiting
8 Zinc Oxide
3 Copper Carb
Tested 97-3-8

Ran off pot where thick. Open crystalline areas (read non-functional
surface). Matte black breaking to pale green where thin.

^6-7 Red/Pink ox or red
Now maybe I should have noted the 6-7 part before firing (duh)

21 Gerstley Borate
16 Neph Sy
11 EPK
20 Whiting
32 Silica
5 Tin oxide
.15 Chrome ox
Tested 97-3-8

Of course, it ran (thumping forehead with heel of hand). BUT!! got
pink/red where it pooled!!! Can one of the glaze gurus please reformulate
for ^10 for me? I would be most appreciative!!!!!

Peacock Blue 9-10

45.45 Neph Sy
7.09 Talc
10.09 Dolomite
8.09 Whiting
29.27 Flint
4 Rutile
.5 Cobalt Carb (I have silicate)
4 Milled Illmenite
Tested 97-3-8

Ran right off the test tile! To me, looks like a rutile redux
blue (which I adore!). Breaks tan. Gloss. No overlap marks.
However, the tile is *still* singing to me 12 hours after
unloading :(

Iron Blue Water 9-10

35 Custer
17 Ball Clay
12 Whiting
19 Flint
7 Dolomite
.5 Cobalt Carb (sil)
2 Iron Chromate (ite?)
Tested 97-3-8

Gloss. No runs. Deep olive green. Overlaps are very forgiving.
No depth to the glaze.

Spodumene 9-11

30 Custer
25 EPK
22 Dolomite
20 Spodumene
3 Whiting
10 Superpax
Tested 97-3-8
Suspender recommended.

Despite being in hottest part of the kiln, looks underfired. Lots
of pitting. Off-white. *Almost* completely matte. Way too dry
for functional IMHO.

Oatmeal 9-10

31.5 Custer
28.1 Gerstley Borate
20 EPK
16.8 Talc
15.5 Superpax
.68 Lithium
Tested 97-3-8

Exactly as described - lovely oatmeal. No glaze movement. Cream/tan
with specks. Satin gloss. Does not show overlaps. Can't wait to
make up a big batch of this glaze!!

I of Toad (green textured matte)

40 F-4 Spar
20 EPK
20 Talc
20 Dolomite
1 Cobalt ox
1 Chrome ox
1 Granular rutile
Tested 97-3-8

"Sang" to me as I unloaded - and for several hours afterwards.
Deep turquoise green satin. Very opaque. No texture - but some
pitting. Might be useful for sculpture.

Waxy Turquoise Green ox or redux 10

19.8 Flint
40.59 Custer
4.95 EPK
14.85 Talc
11.88 Gerstley Borate
6.93 Dolomite
.5 Chrome ox
.5 cobalt ox
Tested 97-3-8

(Applied a bit on the thick side). No running. Exactly as described -
satin finish. Intense opaque colour. Ugly green where thin. This
glaze sings for hours!!

E. Henderson Teal Blue Green Turquoise

39.05 Pot Spar
12.92 Dolomite
5.79 Gerstley Borate
2.36 Mag. Carb
1.13 Zinc ox
9.42 EPK
29.33 Flint
.5 Cobalt ox
.5 Chrome ox
Suspender recommended
Tested 97-3-8

Similar to "Floating Blue". Blue-turquoise mottled gloss. Quite
beautiful. Overlaps don't show. No runs. Great opaque coverage.
Nice depth to glaze. Will do a small bucket and try marketing
some pieces with this glaze!

Grass Green

27.8 Whiting
11.1 EPK
27.8 Custer
33.3 Flint
3.3 Chrome ox
1.1 Cobalt ox
"Must be fire hot!"
Tested 97-3-8

Green-teal medium gloss. Better where thicker. Very
intense colour - but no depth.

So folks, there you have it. Hope these comments are helpful.
Right now, my wrists need a break!!!

sam - alias the cat lady
Melbourne, Ontario, CANADA

Look for me at NCECA - I should be easy to spot. I wear long,
colourful skirts....
and, oh yeah; I have purple hair.

June Perry on mon 10 mar 97

Dear Sam:

Thanks for posting you glaze test results. I used the Temple White for years
in cone 10 reduction. It worked best for me Cone 10 around 3 to 5 O'clock. It
crazed on porcelain and I got delayed crazing on my stoneware body at the
time "Rod's Bod".
At the temperature I fired it was a nice looking satin matt.
You may want to try making another batch and subbing dolomite for the whiting
and using a very fine mesh silica or amorphous silica. By loweringthe calcium
and upping the magnesium and changing the silica you can slightly alter the
co-efficient of expansion and maybe ease the crazing a bit. Sometimes adding
2% lithium carbonate helps a bit as well.

June on tue 11 mar 97

Another possible source of crazing in Temple White is applying it too thick.
I decided to thicken my glaze coat recently and experienced crazing for the
first time. I've gone back to glazing thinner.
Jennifer in Vermont
Thistle Hill Pottery
Montpelier, VT