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glaze tests ^6

updated thu 9 nov 00


Cindy Strnad on wed 8 nov 00

Hi, Everybody

I just pulled a few glaze tests from the kiln and thought I'd take a =
break and tell you all about them.

I fired these glazes on my usual brown ^6 clay body to ^5 at slow speed =
with a 45 minute hold to bring them near ^6. I substituted some =
ingredients for ingredients I had on hand. I realize this doesn't make =
the chances of ending up with the same glaze as the author all that =
good, but I didn't have a lot of pre-conceived ideas of what I wanted, =
anyhow. Just exploring. The glazes are written with the materials I =

First was Dale Huffman's Saturated Iron Oxide from Stephen's Pottery =
site at

Saturated Iron Oxide ^6 oxidation

Gerstley Borate 29
Flint 20
Custer Spar 14
Talc 45
Red Iron Oxide 25

I know, I know--the defunct G. Borate plays an important part in this =
glaze. But I wanted to try Stephen's copper penny look that uses this =
glaze in combination with Gibby's Wild Rose Tenmoku.=20

First, you dip the piece in Wild Rose, then apply a thin coat of SIO. =
The result is a lovely, shimmery piece that glints in the sunlight =
though it looks fairly unremarkable indoors. I'm sure it's quite toxic =
because of all the lithium in Wild Rose, so I used only the SIO on the =
inside of my tea bowl. Here's the recipe for Gibby's Wild Rose in case =
anyone wants to try it.

By itself, SIO is a nice iron red glaze that tends to go greenish where =

Gibby's Wild Rose ^6 oxidation

Lithium 10
Bone Ash 10
Nepheline Syenite 62 =20
EPK 18
Red Iron Oxide 10

This glaze is very pretty on its own, but it does tend to shiver for me. =
I'll have to keep this new piece for a while to see if the SIO fixes =
that, but it was really singing to me when I pulled it hot from the kiln =
this morning.

Not for food use.

Zakin Satin White ^6 oxidation

Custer Spar 18
Soda Frit 20 (I used 3110, as it had the most sodium of =
anything I had on hand.)
Spodumene 14
Kaolin 10
Dolomite 14
Zircopax 24

The Zakin recipe called for soda spar, but all Zakin's recipes seem to =
call for soda spar, and I live in Custer, for Pete's sake. Still, the =
recipe didn't turn out exactly satin, and maybe that's the reason, =
though I doubt it. It was more of a stony matte with lots and lots of =
frothy little pinholes.

The thing I really wanted this glaze for was white accents on dark =
glazes, and it worked fine for that when used with the Volcanic Blue =
glaze that follows. With a 500 gram batch, I probably have all of this =
glaze I'll ever need.

Volcanic Blue ^6 oxidation

Pumice 40
Whiting 20
Barium Carbonate 5
OM #4 Ball Clay 20
Flint 15

Cobalt Carbonate 1%

This turned out a lovely smooth medium-dark blue glaze with a satin =
finish. I wanted something like the sky I saw on my way home from Rapid =
City on Monday night. It was stormy, but the moon shone bright through =
the clouds and lit them up with an incredible slate blue color. I think =
a bit of iron might do the trick.

I'm not sure if this small amount of Barium takes this glaze out of the =
running for food use. It would have to be tested, I'm sure.

The Zakin White splashed on over this glaze did give a very convincing =
imitation of the moon color, though, so I think there's promise.

I tried Tony Hansen's Matte again, and this time I fired the kiln down =
until it reached 1400 degrees F. The first test was a mixture of matte =
and glossy, which I did find attractive though it wasn't what I'd =
expected. This time, the glaze came out smoothly matte all over. Very =

Tony Hansen's Matte ^6 oxidation

Wollastonite 27
Frit 3124 36
EPK 35
Flint 5

I added 1% Cobalt Carbonate for a nice medium blue. A bit too nice, =
actually, and next time I'm going to try a bit of rutile with that to =
tone things down slightly.

Last time, I added 2% and 4% cobalt carbonate, and the two testers were =
indistinguishable dark navy blue.

Stony Matte ^6 oxidation

Bone Ash 7
Nepheline Syenite 25
Magnesium Carbonate 3
Wollastonite 15
Barium Carbonate 30
EPK 15
Whiting 5

I added 1% cobalt carbonate.

This recipe has an interesting story. The first time I tried it, I'd =
been unable to get Strontium Carbonate from my supplier, so I just used =
barium instead. I know there's a conversion factor, but I ignored it. I =
wanted this as an ornamental glaze only, anyhow, and didn't feel like =
digging for the information.

Obviously, this glaze is not meant for food, or even for holding water. =
It's just a "pretty-pretty".

It appears now that I've also added the Whiting on a whim, as the recipe =
I have in Insight calls for 5% tin, and not 5% whiting. Anyway, =
I liked the results I got from the recipe before, so I just remade it =
the way I did the first time.

First time, I used 3% copper oxide for a very nice stony green. The blue =
I got this time was too pretty. I'm going to try it again, with some =
rutile or some iron. The neat stony texture of the glaze is just fine, =
though. I plan to use it on the outside of some extruded vases I've been =
experimenting with.

And now some glazes sent in by Will Edwards:

Rosenrot Revised ^6 oxidation

Frit 3134 15
Nepheline Syenite 15
Flint 37
Whiting 16
EPK 15
Strontium Carbonate 2
Tin Oxide 6
Chromium Oxide 0 .45

Yes, I did finally get some Strontium, so I used that. And I made my =
usual 500 gram batch, so the Chromium Oxide came to 2.25 grams, and I =
weighed out the last gram and divided it into 4 parts because for all I =
know, it might be important in this glaze despite my usual practice of =
rounding everything. I've never made a chrome tin pink glaze before.

This one turned out a lavender that looks better indoors than out in the =
sun. Pretty, not my favorite color, but there's nothing wrong with it.

Matte Base ^6 oxidation

Custer Spar 30 (called for G-200)
EPK 30
Whiting 20
Frit 3134 20

12% RIO and 6% Rutile

Will said this would make a variegated brown similar to mountain rock =
with mottled coloration. That's a good description, except the rocks =
around here are granite--different mountains.=20

Anyway, it's a beautiful matte glaze, and I'm looking forward to trying =
some other colors with it. I think it may be just a touch dryer in feel =
than Tony Hansen's matte glaze (above).

Waxy 3134-2 Williams ^6 oxidation

Frit 3134 31
Custer Spar 9 (soda spar called for)
Talc 9
EPK 16
Flint 26
Strontium Carbonate 2

For Stormy Lavender Blue, add: 1.75% Cobalt Carbonate and 1.75% =
Manganese Carbonate.=20

(I ended up with a figure of 8.75 grams of each colorant after my =
calculations for a 500 gram batch, and just added 9 grams of each, so my =
tester may be a touch darker than it should be.)

Anyway, it came out really cool. The blue is very much like my own =
favorite blue glaze, but where the glaze is a bit thicker, it's, well, =
Stormy Lavender Gray--and on a dark-colored clay. I didn't really expect =
to see any purple because of my clay color, so that's a nice surprise. =
Again, you don't see it in the sunlight--only indoors. I didn't get a =
waxy surface, but rather a soft gloss.

Thanks for all the neat glazes, Will.

Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730