Earl Brunner on thu 1 dec 05
The following glaze is from "Ceramics Handbooks: Glazes Cone 6" by Michael
Bailey
It is described as a cone 6-7 glaze. The problem is that, using my
chemicals, (including Gerstley Borate), the glaze runs excessively at a
solid cone 6. I really like the texture and the crystal development of the
glaze and the colors from Iron, cobalt and copper. I'm not sure, what to do
to stiffen up the glaze, increase the silica? Increase the alumina? I'm
using GlazeChem for software, in the program's limit formula for a satin
matt, it looks a little short of silica. I'm not sure though if the problem
is the variableness of the chemicals, or in the actual formula. I need to
change something though.
GA23 Satin Matt Base
Base
Na2O 0.21
K2O 0.06
MgO 0.03
CaO 0.39
Li2O 0.22
CoO 0.02
CuO 0.06
Neutral
Al2O3 0.38
B2O3 0.12
Acid
SiO2 1.97
TiO2 0.21
Fe2O3 0.05
Alumina:Silica ratio is 1.00:5.15
Neutral:Acid ratio is 1.00:4.48
Alk:Neut:Acid ratio is 1.00:0.50:2.24
Earl Brunner
Las Vegas, NV
Daniel Semler on fri 2 dec 05
Hi Earl,
I don't have the book, and so can't see what the raw materials are which can
be informative of course, but I would tend to approach this by reducing the
fluxes rather than altering the silica alumina ratio. Altering the alumina
silica ratio, a direct affect of adding more of either, will likely affect the
surface texture. It is possible that too radical a change in the fluxing may
reduce the crystal formation if the glaze gets too stiff, but a blend might
find you a compromise you like.
That said, alumina would certainly stiffen it up, just not sure what impact
the amount required would have on the crystal formation you like so much. It
will also become matter (not a physics joke). Of course now thinking a little,
a simple way to stiffen it up would be to add a little silica and a little
alumina, keeping the Si Al ratio the same.
It may be worthwhile to get rid of the GB and sub a frit while your at it. It
may take a shot or two to get it right (due to variations in GB from formulae)
but in the end the glaze would be more predictable.
If you want to shoot me the recipe I could play with it a little and see what
else occurs to me.
Thanx
D
Craig Martell on fri 2 dec 05
Earl was asking:
> I'm not sure, what to do to stiffen up the glaze, increase the
> silica? Increase the alumina?
Hello Earl:
If you want to keep the glaze close to what you're getting now, try raising
both the alumina and silica. The glaze could use more silica anyway. Use
your software to keep the silica/alumina ratio the same while bring the
alumina and silica up in incremental steps. Should work ok.
regards, Craig Martell Hopewell, Oregon
Maurice Weitman on fri 2 dec 05
Hi, Earl,
I played some with this glaze a while back. It's a variant of a Val
Cushing glaze he calls VC Pam Fredericks, and he lists its firing
range as c6 - c9.
I reformulated it to use F3134 instead of GB, and can try to dig up
the recipe for you if you want. I don't have my notes handy, but I
do recall that I preferred the MC6G matt bases for their more
cooperative nature.
I also found Pete Pinnel's Strontium matt base glazes to be better
behaving, although they should be used only for non-food surfaces.
In general, though, it would be Alumina, not Silica that will stiffen
the glaze, but there are other factors you might consider.
You don't mention what type of body you're using. If it's a
fluxy/porcelaneous body, that would contribute to the glaze running.
Glaze thickness might be an issue for you to address. You don't
mention how or how much glaze you applied.
Aside from the frustration due to the variability of GB (and I would
encourage you to use something else), I think this is a great
opportunity for you to do line blend tests.
Have fun!
Regards,
Maurice, in sunny Fairfax, California, the morning after our first
significant rain/wind storm, where I was privileged to watch the
ephemeral creek across the street come to life yesterday morning; an
actual wall of water moved slowly before my eyes to create our winter
gem.
Ever wonder what 2000 looks like?
At 9:25 PM -0800 on 12/1/05, Earl Brunner wrote:
>The following glaze is from "Ceramics Handbooks: Glazes Cone 6" by Michael
>Bailey
>
>It is described as a cone 6-7 glaze. The problem is that, using my
>chemicals, (including Gerstley Borate), the glaze runs excessively at a
>solid cone 6. I really like the texture and the crystal development of the
>glaze and the colors from Iron, cobalt and copper. I'm not sure, what to do
>to stiffen up the glaze, increase the silica? Increase the alumina? I'm
>using GlazeChem for software, in the program's limit formula for a satin
>matt, it looks a little short of silica. I'm not sure though if the problem
>is the variableness of the chemicals, or in the actual formula. I need to
>change something though.
Steve Slatin on fri 2 dec 05
Earl --
Read with caution; I'm only a beginning experimenter myself.
Your silica concentration is a little low, which may cause various
problems. Increasing silica alone, though, tends to make glazes
runnier, so that's not a good direction to take (at least not
alone).
Your alumina is a second issue -- jacking up the alumina will
stiffen a glaze, but (1) your alumina concentration is pretty
high already, and (2) I have a not-sufficiently-tested theory
that adding alumina reduces crystallization. If you like that
about the glaze, adding more alumina doesn't hold out too
much hope. It'll make the glaze less of what you find
attractive in it.
You have high concentrations of two melters that would
be fairly easy to tinker with, though -- lithium and boron. Lithium
has an extremely low COE. It is sometimes added to a
glaze just as a corrective to fit problems. Your COE is
moderate as is, so if the glaze fit is good, I'd prefer
not to mess with the Li. This saves you having to change
everything else to get back where you want to be.
Boron makes up about a quarter of Gerstley Borate, a material
with known irregularities in production ... you never know exactly
how much boron it's putting into the mix and boron lowers the
mix's melting temperature ... it's the most likely ingredient to
not be real close to what Bailey was using in his workshop
when he made up his batch of the glaze ...
so ....
If you're getting a too-runny result, and that's the only thing
that needs to be fixed, why not start with reducing the GB?
It should fix that one problem fairly readily. And the lithium
will remain in the mix, so the glaze won't change in COE
too much, and it'll only lower the Ca a bit so it'll probably
still have the texture you want.
Usual disclaimers apply, best wishes -- Steve Slatin
Earl Brunner wrote:
The following glaze is from "Ceramics Handbooks: Glazes Cone 6" by Michael
Bailey
It is described as a cone 6-7 glaze. The problem is that, using my
chemicals, (including Gerstley Borate), the glaze runs excessively at a
solid cone 6. I really like the texture and the crystal development of the
glaze and the colors from Iron, cobalt and copper. I'm not sure, what to do
to stiffen up the glaze, increase the silica? Increase the alumina? I'm
using GlazeChem for software, in the program's limit formula for a satin
matt, it looks a little short of silica. I'm not sure though if the problem
is the variableness of the chemicals, or in the actual formula. I need to
change something though.
GA23 Satin Matt Base
Base
Na2O 0.21
K2O 0.06
MgO 0.03
CaO 0.39
Li2O 0.22
CoO 0.02
CuO 0.06
Neutral
Al2O3 0.38
B2O3 0.12
Acid
SiO2 1.97
TiO2 0.21
Fe2O3 0.05
Alumina:Silica ratio is 1.00:5.15
Neutral:Acid ratio is 1.00:4.48
Alk:Neut:Acid ratio is 1.00:0.50:2.24
Earl Brunner
Las Vegas, NV
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John Hesselberth on fri 2 dec 05
On Friday, December 2, 2005, at 12:25 AM, Earl Brunner wrote:
> . I'm not sure, what to do
> to stiffen up the glaze, increase the silica? Increase the alumina?
> I'm
> using GlazeChem for software, in the program's limit formula for a
> satin
> matt, it looks a little short of silica. I'm not sure though if the
> problem
> is the variableness of the chemicals, or in the actual formula. I
> need to
> change something though.
>
Hi Earl,
I can only guess here because this is a rather unusual glaze. I think
it is best to look at this one by examining both the unity formula and
the ingredients. When I saw how much lithium it has in it I went to
Bailey's book to find our how that was sourced--6.2 % Lithium
Carbonate. Over the years we have seen several reports of how high
levels of lithium sourced from the carbonate can cause high levels of
variability on the same pot--specifically reports of both crazing and
shivering on the same piece. So I might speculate that the glaze is so
variable on the pot that you are getting areas that are overfluxed and
others that are underfluxed. You probably want to retain the high
levels of alkalis, though, as that may well be giving you the color
response you like. So the first thing I would try is to hold the same
unity formula and source most of the lithium from spodumene instead of
lithium carbonate. See if that makes it behave better. If that doesn't
work, but the glaze still looks the same to you, I would start adding
clay to stiffen it up.
I'll be interested to see what others recommend because, as I noted up
front, I am purely speculating here.
Regards,
John
Ron Roy on sat 3 dec 05
Hi Earl,
Increasing the Alumina is the usual way to correct running - but you want
to keep the ratio of silica to alumina the same - so you increase the clay
- then add silica to get the ratio right.
If you care to send me the original and yours with your materials I can
check it to see if you are subbing in the righ amounts - or if the original
will run.
RR
>The following glaze is from "Ceramics Handbooks: Glazes Cone 6" by Michael
>Bailey
>
>It is described as a cone 6-7 glaze. The problem is that, using my
>chemicals, (including Gerstley Borate), the glaze runs excessively at a
>solid cone 6. I really like the texture and the crystal development of the
>glaze and the colors from Iron, cobalt and copper. I'm not sure, what to do
>to stiffen up the glaze, increase the silica? Increase the alumina? I'm
>using GlazeChem for software, in the program's limit formula for a satin
>matt, it looks a little short of silica. I'm not sure though if the problem
>is the variableness of the chemicals, or in the actual formula. I need to
>change something though.
>
>
>
>GA23 Satin Matt Base
>
>Base
>
>Na2O 0.21
>
> K2O 0.06
>
> MgO 0.03
>
> CaO 0.39
>
>Li2O 0.22
>
> CoO 0.02
>
> CuO 0.06
>
>
>
>Neutral
>
>Al2O3 0.38
>
>B2O3 0.12
>
>
>
>Acid
>
>SiO2 1.97
>
>TiO2 0.21
>
>Fe2O3 0.05
>Alumina:Silica ratio is 1.00:5.15
>
>Neutral:Acid ratio is 1.00:4.48
>
>Alk:Neut:Acid ratio is 1.00:0.50:2.24
>Earl Brunner
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ivor and Olive Lewis on sat 3 dec 05
Dear Earl Brunner,
I think the question is, "Why is this glaze behaving as though it were =
made to mature at cone 2?'
Another question would be "How reliable is your heat monitoring system. =
Is there even heat distribution and is this effect is widespread or is =
it localised in the kiln? "
These will lead to a range of answers to correct the situation to your =
satisfaction.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Paul Gerhold on sun 4 dec 05
Earl,
This looks like one of those fussy glazes that will be really sensitive to
changing the amounts of silica or alumina. When you talk crystals you are
talking low alumina and therefore a glaze with a desire to run.
I don't know how you fire or if you are using this glaze in conjunction with
other glazes but you may just want to experiment with lowering your firing
temp. Many glazes have a broad firing range and could still work with this
one. Some of the crystal glazes I have played with will lose the crystal effect
if they don't run slightly-if that is the case you will have to use a soft
biscuit under the piece and then grind the foot.
Other than the above my best guess would be to reduce the lithium.
Good luck- if you really want this glaze I think you could be in for a lot
of experimentation.
Paul-who finds glaze calculation to be pretty useless when dealing with more
esoteric surface effects.
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