Lynspots@AOL.COM on thu 7 sep 00
Hi all,
I got this recipe from Mishy Lowe and after storing it for a few months, am
having a problem with it. Mishy says it always stores fine for her, never a
problem. When I went to use it after making it three months or so ago, my one
gallon bucket of glaze was solidified, not hard, but firm enough that I had
to press my fingers hard into the mix to scoop out handfuls of glaze. I then
put the glaze into a five gallon bucket and had to add enough water to almost
fill that bucket before I could thin it enough to dip. Then when fired, the
glaze was little, separated pills of glaze over the test pot.
Here is the recipe as I received it from Mishy:
glaze name: Emerald Green
cone: 5-9
firing type: oxidation or reduction
color: dark green
surface: frosty
recipe:
Gerstley Borate 49
EPK 19
Silica 32
Soda Ash 2
Chrome Oxide 2
Cobalt 1
comments: Emerald Green ^5-9 oxidation or reduction- a darker green sometimes
with a slight dark blue frost.
Note: I always use rain water exclusively for all glazes. The first time I
used the glaze, it was a nice, deep emerald color, covered the pots well with
a splash of a satin off white glaze over which gave a nice contrast. I did
use GB in the original mix, didn't know about the discontinuation until
later. I fire cone 6 oxidation.
Thanks for any help you can give, I really like this glaze and have some
clients interested in it as well.
Lynne Antone
Beaver Creek Arts
Olympia WA USA
Linda Arbuckle on sat 9 sep 00
Your glaze has soda ash as an ingredient. This causes deflocculation.
See Frank Hamer, "A Potters Dictionary" for the long explanation.
Parallel particle orientation (deck of cards) will cause it to settle
like a brick in the bucket. Flocculate (see also in Hamer) with Epsom
Salts or a product called Flocs (from Ceramics supplier) to change
particle orientation to end-to-middle (house of cards). Applies better
when dipping. Doesn't settle into that brick. Notes follow....
Flocculation: perpendicular particle (house of cards) orientation of
ball clay and/or bentonite. Particles "floc" together, sticking together
end-to middle. Thickens the liquid. Good for glazes applied by dipping,
good to thicken glaze for re-glazing or application to over-bisqued
work. Prevents glaze settling into a hard brick in the bottom of the
bucket over time. Materials used to flocculate: Epsom salts (magnesium
sulfate), calcium sulfate.
Deflocculation: parallel (deck of cards) ball clay and/or bentonite clay
particle orientation, slight repulsion between particles. Fluid with
less water. Good for brushing, low-shrinkage slips, casting slips,
making terra sigillata. Causes glazes to settle into a hard, dense mass
in the bottom of the bucket. Can cause "streaming" (last run of glaze
takes off all glaze under) when used for dip application of glaze, can
make sharp edges hard to glaze when dipping. Materials used to
deflocculate: sodium silicate, Darvan, soda ash. Adding too much
deflocculant destroys the effect. Neph sy, some frits and lithium
carbonate used as glaze ingredients will have a deflocculating effect on
glazes. "Soft" water will also deflocculate glazes.
--
Linda Arbuckle, Assoc. Prof.
Univ of FL
School of Art and Art History
P.O. Box 115801, Gainesville, FL 32611-5801
(352) 392-0201 x 219
e-mail: arbuck@ufl.edu
pam pulley on sat 9 sep 00
We use this glaze in our studio all the time. A favorite with students. We
add 2% bentonite. Never had a problem with heavy type of settling you are
getting.
Pam
Mid michigan
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Lynspots@AOL.COM on sun 10 sep 00
Linda, Wow, thanks for all of the info on glazes settling. Pam in Michigan
also suggested adding a bentonite to the glaze for settling.
The odd thing about this glaze is that it didn't settle to the bottom of the
bucket, it all thickened as a mass that I could just push my fingers into, no
water standing at the top at all. It went from 1 gallon to 5 gallons with
enough water added to allow dipping, but terrible results. Tom Buck suggested
either heating the glaze (he says the combo of soda ash and gerstley will
cause this) or, just start over again.
This morning I mixed up a new batch, using Laguna Borate instead of Gerstley
and will fire a test tomorrow. Tom and I agreed that prob one of the reasons
Mishy doesn't have any problems with this glaze is that it is soooo hot where
she lives. 'Course, Pam lives in Michigan, and I think she has me beat for
cold weather. I do have the bucket of first mix in front of my studio heater,
yes, I needed to turn it on today, will see what that does. Also decanted
half a gallon of water off of it today.
Will keep you posted. Thanks for all the advice.
Lynne Antone
Beaver Creek Arts
Olympia WA USA
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