Mary Klotz on thu 12 feb 98
In The Best of Pottery, 1996, I'm finding several glazes that pull into tiny
mosaic shapes. Some are sharp edged, like Stephen Fabrico's black expansion
glaze, but some are rounded edged as though the glaze had evenly crawled, as
seen in Hoshiro Ikeda's "oracle" glazes. a "lichen" glaze on a piece by Bacia
Edelman is similar.
I am aware of a couple low fire commercial special effect white glazes that do
this, but am looking for formulations at cone 6 for these sorts of effects.
I also am drawn to the surface of the eutectic slips (Harvey Sadow).
I have not found any formulas in the multitude of books I've been studying;
could the effect be a function of firing the pot to its clay's maturity, then
refiring with a lower temp maturing glaze to encourage crawling?
Any insight appreciated, and tested formulas will put you on the list of
prospective saints.
Mary
foresthrt@aol.com
John Post on fri 13 feb 98
>----------------------------Original message----------------------------
.... I'm finding several glazes that pull into tiny
>mosaic shapes. Some are sharp edged...but some are rounded edged as
though the glaze had evenly crawled... am looking for formulations at cone
6 for these sorts of effects.
>could the effect be a function of firing the pot to its clay's maturity, then
>refiring with a lower temp maturing glaze to encourage crawling?
>
Mary,
Here's some recipes for a couple of crawling glazes. The high magnesium
content of the glazes is what encourages the crawling action. The first
one crawls into rounded bumps. Someone on the list sent it to me. The
only problem that I have with this glaze (and I use the word glaze loosely
in this case) is that after you dip your pieces into the glaze it tends to
flake off before and sometimes during the firing. I usually brush Amaco
Velvet Underglazes on the pots first and then dip them in glaze. The glaze
application should be thick to encourage the crawling...
++++++++++++++++++++++++
+++ Beady Eyes 2 +++
++++++++++++++++++++++++
Range: 6-8
Firing type: Ox. or Red.
Glaze type: Stoneware
Testing: Tested
Date: 03/16/97
Custer feldspar 2000 25 %
Whiting 480 6 %
Magnesium carb 2800 35 %
Kentucky OM #4 800 10 %
Flint 640 8 %
Frit 3134 1280 16 %
-------- ------
8000 100 %
Notes:
This is not really a glaze, it is too high in secondary fluxes.
It has a snake - alligator like crawling texture. This looks good
over a black slip or over some velvet underglazes.
===========================
Chemical Analysis
===========================
Na2O 0.07 Al2O3 0.12 SiO2 1.12
K2O 0.05 B2O3 0.09 TiO2 0.00
MgO 0.67 Fe2O3 0.00
CaO 0.21
Alumina:Silica ratio is 1.00 : 9.09
Neutral:Acid ratio is 1.00 : 5.19
Alkali:Neutral:Acid ratio is 1.00 : 0.22 : 1.12
Expansion coefficient: 67.2 x 10e-7 per degree C
Oxides causing abnormal expansion effects: B2O3
This one is from Lana Wilson's book (I haven't tried it)...
Bell Lichen Glaze ^6
Magnesium Carbonate 32.98
Talc 8.51
Soda Spar 31.92
Frit P-54 6.38
Kaolin 20.21
add: Zinc Oxide 6.38
Mason stains that work well with the above glaze are...
#6319 10%
#6020 10%
#6129 10%
happy testing,
John Post
jp6mchp@moa.net
Sterling Heights, Michigan
douglas gray on fri 13 feb 98
I was fortunate to catch Ikeda's workshop in Houston a couple of years ago where
he gave out the following recipe for his crackle glaze. Ends up, he is one of
those "simple mix" glazers. The common ingrediant in all of his crackle glazes
is Magnesium Carbonate. He simply substitutes the feldspars out to raise or
lower the melting point.
for c08 crackle
50% Magnesium Carb.
50% Gerstley Borate
for c6 crackle
50% Magnesium Carb
50% Neph SY
for c10 crackle
50% Magnesium Carb
50% Custer Feldspar
I have only worked with the cone 10 version in reduction, but I expect similar
result at the other temperatures as well. In a line blend test, an increase of
Magnesium carb. results in a dry, more brittle surface, where a decrease leads
to a more glassy and smooth surface. I also tried the following color
additions: cobalt gave blue (naturally), iron gave yellow to brown, and copper
had little or no effect (maybe not enough glass former to keep it from fuming?)
Another possible treatment is to fire the crackle glaze on at a high temperature
and then re-glaze and refire the same pice at a lower temp. If the clay and the
crackle glaze have not vitrified, the surface should absorb enough glaze to get
additional color.
As with everything, testing seems to be the key to a chieving just the right
results for you. Happy testing
doug
In message Mary Klotz writes:
> ----------------------------Original message----------------------------
> In The Best of Pottery, 1996, I'm finding several glazes that pull into tiny
> mosaic shapes. Some are sharp edged, like Stephen Fabrico's black expansion
> glaze, but some are rounded edged as though the glaze had evenly crawled, as
> seen in Hoshiro Ikeda's "oracle" glazes. a "lichen" glaze on a piece by
> Bacia
> Edelman is similar.
> I am aware of a couple low fire commercial special effect white glazes that
> do
> this, but am looking for formulations at cone 6 for these sorts of effects.
> I also am drawn to the surface of the eutectic slips (Harvey Sadow).
> I have not found any formulas in the multitude of books I've been studying;
> could the effect be a function of firing the pot to its clay's maturity, then
> refiring with a lower temp maturing glaze to encourage crawling?
>
> Any insight appreciated, and tested formulas will put you on the list of
> prospective saints.
>
> Mary
============================================================================ =)
Douglas E. Gray, Assistant Professor of Art
P.O. Box 100547
Department of Fine Arts and Mass Communication
Francis Marion Univeristy
Florence, South Carolina 29501-0547
dgray@fmarion.edu
803/661-1535
Sandra K. Tesar on fri 13 feb 98
Mary
Have you tried Spectrum glazes - ^5-6 they seem capable of that - the
first time I used one I over glazed an edge, it dripped and pooled into
little Chicklets....
_____________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com
Or call Juno at (800) 654-JUNO [654-5866]
| |
|
