search  current discussion  categories  glazes - cone 4-7 

cone6 white glaze (white paint)

updated wed 30 apr 97


Sylvia See on mon 14 apr 97

Hi Dan;
Here is the best white glaze I have for cone 6, it was given to me by Tony
Hansen, and read the text file for variations. I had wonderful results with
this glaze, but I should add that I had problems until I started using
distilled water. Our water has so many chemicals added that I was having a
heck of a time with recipes Tony had that worked for him. They now work for
me as well.
I used this recipe with all the mason stains, and mixed a little thinner,
did alot of airbrushing, with stains in the glaze. I used the superpax
percentage at the bottom, of page.
Sylvia See Claresholm, Alberta
DATE: 12/10/92
CODE #: 1213G
Base glaze adjustable cone 3-8, ultra-clear glossy and stony matte for use
with stains

More information available from Tony Hansen, IMC, 134 Upland Drive,
Medicine Hat, Alberta T1A 3N7 FAX 403-527-7441. Fired samples of all
variations location ref# 352, 461, 648

WOLLASTONITE....... 23.0
FERRO FRIT 3134.... 30.2
KAOLIN............. 24.9
FLINT.............. 14.6

The above is a sample recipe of one glaze from a series done as a follow-up
to previous work (series #1064). The initial objective was to produce a
glossy transparent for cone 5 which would not have a cloudiness at thick
areas. However, as development proceeded, I undertook adjustments to make
it work with all fifty stains I have. Then I did work to adjust its melting
temperature, to reduce expansion to prevent crazing on porcelain, and
finally to adjust it to produce a matte. Although each variation might
simply appear as a different glaze recipe, the common formula roots, and
unified development make them all one family.

Many comments below assume you have the ability to work at the oxide level
with INSIGHT and that you have read the book "The Magic of Fire".

While the formula is key, probably any materials local to your area would
work as well. However, in the interests of reliability, I recommend the use
of a Frit instead of Gerstley Borate to supply B2O3. The formula of each
constituent material can be deduced from the above detailed report. Be sure
to do calculations to compensate for any chemical differences between your
materials and those used here.

Ferro Frit 3134 - This is a common frit available in my area, however two
others, #3195 and #3124 also work well, even with a simple recipe level
swap. However, the validity of any comments herein assume an oxide level

Wollastonite - This was used as a source of CaO because it loses no weight
during melting, and thus is not subject to variation in LOI as are whiting
and dolomite. This also supplies SiO2, minimizing the need for flint and it
is an all-around better material.

Kaolin - I used a moderate plasticity kaolin as the key source of Al2O3
and adjusted things to be sure adequate kaolin is present to maintain good
slurry suspension. I avoided ball clay and bentonite to source Al2O3
because they would add unwanted iron and possible speck.

Flint - 300 mesh material used.

Custer Feldspar - This feldspar was readily available to me. When
selecting a feldspar, stay away from the high-soda materials.

The recipe as shown above melts to a clear gloss from cone 5-7. To move it
downward to cone 2, move Al2O3 to .25 and the B2O3 to .3. The SiO2 can be
moved up slightly to maintain glaze fit for these lower temperatures.
However, the lower Al2O3 can result in the development of some cloudiness.
For cone 8, use .35 Al2O3 and 3.5 SiO2.

The recipe as shown above will fit most stoneware bodies, however the more
porcelainous and the lower the temperature, the more likely crazing will
be. For lower temperatures, use extra B2O3 and SiO2 to lower expansion, at
higher temperatures plenty of extra SiO2 can be tolerated. For alumina
matte versions, the high Al2O3 will lower expansion, and if crazing occurs,
extra SiO2 and Al2O3 in ratio can be added, or the calcium matte can be
used. A somewhat higher SiO2:Al2O3 ratio can be tolerated if necessary. As
of Dec/92, I have not measured the co-efficient of thermal expansion on a
dilatometer, but this will be done early in 1993.

The initial impetus for the development of this glaze was to get a one
whose chemistry was compatible with as many types of stains as possible,
especially with the rather temperamental chrome-tin pinks and maroons. In
its above form, this base works with 50 colors I have tried, and with most
produces vibrant results. I did my testing and actual stain work by
painting a pure stain-water mix onto the body, and applying the transparent
glaze over this. One note about chrome-tin stains: keep a minimum 3:1 ratio
of CaO:B2O3, 15% CaO, and don t use any MgO.

This recipe is balanced according to normal limit formulas, although the
CaO is quite high. As is, I suspect no danger of leaching, and as of Dec/92
I have not done actual tests to determine leaching of any of the metallic

I have tested this system with varying amounts of every oxide and
throughout a range of temperatures. The only aspects of volatility noted
are the tendency of the ultra-clear to form cloudy areas of opacity.
However, for colors and whites, this will not be a concern.

As of Dec/92, I have not done strength tests, but I am planning to do
tensile strength tests of various clay-glaze combinations in the new year.
At that time I will update this report with my findings.

The above recipe, as shown, is a perfect ultra-clear glossy fires at cone

Wollastonite has been used to source CaO instead of whiting or dolomite to
eliminate the bubbles that appeared in earlier versions. These were
associated with the release of carbonates that occurs when these materials

I interpreted the cloudy areas of opacity that nagged thicker sections on
early versions of the glaze as crystallization during freezing. It appears
that the key to keeping this to a minimum is keeping the Al2O3 above about
27. Leaving the Al2O3 at .25
and increasing SiO2 made the problem even worse. Moving Al2O3 all the way
to .5 will produce a very nice crystal matte.

To produce a matte, I tried adding ultra-fine calcined alumina to move
Al2O3 to .5, but the alumina did not dissolve in the melt. It appears it
would need considerable milling to do so. To produce a silky gloss, I found
..2 B2O3, .4 Al2O3 and 2.4 SiO2 worked well. A beautiful stony matte
resulted from .2 B2O3, .5 Al2O3, and 2.4 SiO2. The following recipe shows
an example:

FERRO FRIT 3134. 21.00
KAOLIN.......... 39.00
FLINT........... 3.50

An alternative way to producing a matte was a calcium saturation. This
worked with .9 CaO, .17 B2O3, .43 Al2O3 and 2.0 SiO2. A sample of this
variation is as follows:

FERRO FRIT 3134. 21.10
KAOLIN.......... 45.01

This recipe system is still in a state of flux, and in the next few months
I will have much more information on it.

The system contains plenty of kaolin, so you could employ ball clay to
source Al2O3. This would increase glaze plasticity and shrinkage for use as
a slip on leather hard ware. To reduce glaze shrinkage, use a mix of
calcined and raw kaolin to complete
the kaolin complement.

I have used two moderately expensive materials, frit and wollastonite.
However, this was done for good reason. I have minimized the amount of
frit. In some cases, you might like to substitute in gerstley borate to
supply B2O3, but make sure it is 200 mesh (pass some through a 200 mesh
screen to check).

I have tried a number of opacifiers, and there is no problem in producing a
"toilet bowl white". Such a glaze is desirable for overglaze stain work,
and the stain colors feather very nicely at their edges.

10% tin oxide: Works well but very sensitive to minute amounts of chrome in
body or nearby ware which turn introduce a pinkish hue.
20% Zircopax: Excellent intense white
10% Titanium: Opaque but pinholed and yellowish
15% Superpax: Perfect white
5% Zinc: Melts more, small dimples in surface and no opacity
5% Titanium: Yellowish with just a few crystals, but not opaque

The golden years have come at last, I cannot see, I cannot pee,
I cannot chew, I cannot screw. My memory shrinks, my hearing stinks.
No sense of smell, I look like hell. My body drooping, got trouble pooping.
The golden years have come at last, The golden years can kiss my Ass.