Bruce Girrell on wed 21 oct 09
Yellow Salt is a glaze that we have started using recently. The recipe that=
=3D
we use does not call for acid:
Neph sy 60.5
Dolomite 20.1
Zircopax 15.3
OM4 4.1
Add
RIO 1.0
Bentonite 4.0
This is almost the same as the recipe posted by Veena Raghavan. I would gue=
=3D
ss that either recipe will be just as good as the other.
We have fired the glaze from ^10 to ^12. It is a pleasing light yellow wher=
=3D
e thicker and breaks a complementary brown where thinner. It seems to play =
=3D
well with other glazes. We have had particularly good results with Yellow S=
=3D
alt layered over a saturated iron glaze (Black Teadust), which creates some=
=3D
what of a leopard spot effect. With excessive reduction it turned out white=
=3D
. With an oxidizing soak at the end of the firing (we use 20-30 minutes) it=
=3D
turns out its characteristic light yellow. I suspect that it would work we=
=3D
ll in oxidation, but have not tried it.
Note how little clay there is in this recipe. Glazes with little clay will =
=3D
tend to settle quickly in the bucket. I suspect that the reasoning behind t=
=3D
he HCl was to (oh, god, here we go again) flocculate the available clays to=
=3D
help with the settling problem. I mixed in some CMC and it helped a lot.
The glaze is low on silica. Si:Al is 4.85. But it is satin/matte to begin w=
=3D
ith and contains no metals other than iron, so etching and leaching shouldn=
=3D
't really be issues. Still, we use it only on exteriors.
Bruce and Lynne Girrell=3D
Veena Raghavan on wed 21 oct 09
Thanks, Brucem for the additional information on the Yellow Salt glaze. the
combo you described sound very interesting. As to the Muriatic Acid, I
don't like to use acid, so will try something else.
Veena
In a message dated 10/21/2009 9:34:58 AM Eastern Daylight Time,
bigirrell@MICROLINETC.COM writes:
>
> Yellow Salt is a glaze that we have started using recently. The recipe
> that we use does not call for acid:
>
> Neph sy 60.5
> Dolomite 20.1
> Zircopax 15.3
> OM4 4.1
>
> Add
> RIO 1.0
> Bentonite 4.0
>
> This is almost the same as the recipe posted by Veena Raghavan. I would
> guess that either recipe will be just as good as the other.
>
> We have fired the glaze from ^10 to ^12. It is a pleasing light yellow
> where thicker and breaks a complementary brown where thinner. It seems to=
play
> well with other glazes. We have had particularly good results with Yellow
> Salt layered over a saturated iron glaze (Black Teadust), which creates
> somewhat of a leopard spot effect. With excessive reduction it turned out
> white. With an oxidizing soak at the end of the firing (we use 20-30 minu=
tes)
> it turns out its characteristic light yellow. I suspect that it would wor=
k
> well in oxidation, but have not tried it.
>
> Note how little clay there is in this recipe. Glazes with little clay wil=
l
> tend to settle quickly in the bucket. I suspect that the reasoning behind
> the HCl was to (oh, god, here we go again) flocculate the available clays
> to help with the settling problem. I mixed in some CMC and it helped a lo=
t.
>
> The glaze is low on silica. Si:Al is 4.85. But it is satin/matte to begin
> with and contains no metals other than iron, so etching and leaching
> shouldn't really be issues. Still, we use it only on exteriors.
>
> Bruce and Lynne Girrell=3D
VeenaRaghavan@cs.com
Karin Givon on wed 21 oct 09
I've done Yellow Salt in oxidation and it was quite thick ( on
purpose) and absolutely Gorgeous! I did it on a cut out of Bison,
white bison being magical. And it was. Lots of my cone 10 reduction
glazes are lovely in oxidation! who knew? It's a whole amazing world
out there.
Karin
DancingDragonPottery.net
On Oct 21, 2009, at 5:43 AM, Bruce Girrell wrote:
Yellow Salt is a glaze that we have started using recently. The
recipe that we use does not call for acid:
Neph sy 60.5
Dolomite 20.1
Zircopax 15.3
OM4 4.1
Add
RIO 1.0
Bentonite 4.0
This is almost the same as the recipe posted by Veena Raghavan. I
would guess that either recipe will be just as good as the other.
We have fired the glaze from ^10 to ^12. It is a pleasing light
yellow where thicker and breaks a complementary brown where thinner.
It seems to play well with other glazes. We have had particularly
good results with Yellow Salt layered over a saturated iron glaze
(Black Teadust), which creates somewhat of a leopard spot effect.
With excessive reduction it turned out white. With an oxidizing soak
at the end of the firing (we use 20-30 minutes) it turns out its
characteristic light yellow. I suspect that it would work well in
oxidation, but have not tried it.
Note how little clay there is in this recipe. Glazes with little clay
will tend to settle quickly in the bucket. I suspect that the
reasoning behind the HCl was to (oh, god, here we go again)
flocculate the available clays to help with the settling problem. I
mixed in some CMC and it helped a lot.
The glaze is low on silica. Si:Al is 4.85. But it is satin/matte to
begin with and contains no metals other than iron, so etching and
leaching shouldn't really be issues. Still, we use it only on exteriors.
Bruce and Lynne Girrell
Neon-Cat on wed 21 oct 09
Bruce Girrell wrote: "oh, god, here we go again" (re: flocculation, clay, H=
Cl).
Hey, I'm not on any war path. It is complicated, OK? And we are now way bey=
ond 1987 and simple pH dependence and into an age where it is understood an=
d demonstrated that flocculation is dependent on the concentration and type=
of salts (electrolytes) available and the pH affecting the aqueous solutio=
n and all in that solution, the acids and clays (by type of clay) included.=
And other things, too.
Did you know even bubbles in a glaze can have a charge? In an HCl-treated s=
olution sometimes kaolin will form edge-to-face flocculation with bubbles. =
Add bentonite to that and the effect is ruined.
How about we be potters and stick with "if it works, use it" or "if it work=
s, don't mess with it".
It might be nice down this road of clay life to include with glaze recipes =
the flocculant known by someone to have worked well with the glaze if the g=
laze stores and works best when flocculated. Our glazes contain so many typ=
es of ingredients (salts/electrolytes) they will each respond differently t=
o different flocculants and deflocculants. There is not a one-size-fits all=
flocculant or deflocculant. Like you all say: "Your mileage may vary".
When reading literature it is often good to remember that for some applicat=
ions when flocculation is talked about they mean flocculation to the point =
of settling out. They want that. We want a glaze to be only slightly floccu=
lated for what we do; working at that tipping point is often problematic.
The beauty and magic in what we do is unique and marvelous to us as potters=
and something to rejoice in doing and sharing.
Peace?
Marian
Neon-Cat
Steve Slatin on thu 22 oct 09
Dave --
Let me get on my soapbox here (you have
only yourself to blame for this one)
and point out that the reason why
it APPEARS that this is a very low
silica glaze is because of the way that
you evaluate it.
Most potters evaluate glazes using
unity-over-fluxes.=3DA0 This is fine as
long as you use identical (or near-
identical) concentrations of fluxes
in your glazes.=3DA0 Of course this is
hardly ever the case, and this is why
unity glaze analysis constantly gives
results that aren't helpful.
Evaluate the molar concentration of
silica, though, and you see something=3D20
quite different.=3DA0 Yellow salt has
59.7 % silica.=3DA0 This compares with
Turner's Beauty, 57.1%; Anderson Ranch
Red, 63.7%; Touchstone Rd, 62.5% and many,
many others.=3DA0 (Rarely do you see a=3D20
silica molar concentration at 80% for
a cone 10 glaze, and the lowest I've ever
seen for a cone ten was just over 50%.
High 50's to mid-70's is the sweet spot
for cone 10.=3DA0 OTOH, 50% is just about
right for most 04 - 06 glazes.)
So specifically why does the yellow
salt recipe look flaky?=3DA0 Well, it's the
high concentration of flux.=3DA0 And why
is there a high concentration of flux?
To glassify the highly refractory high
concentration of zirconium in the glaze.
It still generally doesn't 'melt' as=3D20
such, but the glass is fluxy enough to=3D20
suspend all of it, and hold it in the
matrix.=3DA0=3D20
=3DA0
Steve Slatin --=3D20
--- On Wed, 10/21/09, David Hendley wrote:
> From: David Hendley
> Subject: Re: Yellow salt - was: muriatic acid
> To: Clayart@LSV.CERAMICS.ORG
> Date: Wednesday, October 21, 2009, 4:13 PM
> I have been using "Yellow Salt"
> recently. I'm puzzled with
> the name, that there is no salt involved and it is never
> more
> than the slightest hint of yellow, but it is an interesting
> glaze.
>=3D20
> I also noticed how little silica is in the formula. Usually
> such
> a silica-deficient glaze would tend to be very matt, prone
> to
> running if overfired the slightest bit, and be very crazed.
> This
> glaze has none of these problems.
> My un-scientific, but years-of-experience theory is that
> the off-the-charts, abnormally high, amount of
> zirconium-silica
> opacifier in the recipe has a strong effect on the final
> formula
> and fired result.
> This is a case where a glaze calculation program, which
> ignores glaze additives, can provide a result that does
> not
> accurately reflect what is really happening.
>=3D20
> David Hendley
> david@farmpots.com
> http://www.farmpots.com
>=3D20
>=3D20
> ----- Original Message -----
> Yellow Salt is a glaze that we have started using recently.
> The recipe that
> we use does not call for acid:
>=3D20
> Note how little clay there is in this recipe. Glazes with
> little clay will
> tend to settle quickly in the bucket. I suspect that the
> reasoning behind
> the HCl was to (oh, god, here we go again) flocculate the
> available clays to
> help with the settling problem. I mixed in some CMC and it
> helped a lot.
>=3D20
> The glaze is low on silica. Si:Al is 4.85. But it is
> satin/matte to begin
> with and contains no metals other than iron, so etching and
> leaching
> shouldn't really be issues. Still, we use it only on
> exteriors.
>=3D20
> Bruce and Lynne Girrell=3D3D
>=3D20
=3D0A=3D0A=3D0A
John Hesselberth on thu 22 oct 09
On Oct 22, 2009, at 6:40 PM, Steve Slatin wrote:
> (Rarely do you see a
> silica molar concentration at 80% for
> a cone 10 glaze, and the lowest I've ever
> seen for a cone ten was just over 50%.
> High 50's to mid-70's is the sweet spot
> for cone 10. OTOH, 50% is just about
> right for most 04 - 06 glazes.)
Hi Steve,
You and I have a fundamental disagreement here. The difference between
stable glazes at the various temperatures is primarily the type of
fluxes--not the amount of silica and alumina. Earthenware glazes have
more alkalis and/or boron and high fire glazes have more alkaline
earths and little or no boron or zinc. Both, if they are stable,
have similar levels of silica and alumina. Unity formulas show that
very nicely, but if you would rather think in mole % that will work
too. One method is not better than the other. Now I agree that the
literature is full of lower temperature glazes that fit your criteria,
but test them for stability and you will find a lot of garbage.
Think of it this way. Glazes have to perform at room temperature. They
don't really care what temperature they were fired to. They just care
about their composition and whether or not they were fully melted so
they could form a "good glass". If their silica and alumina levels are
too low they will not have been able to form a good glass.
Regards,
John
Steve Slatin on fri 23 oct 09
John --
There are two different issues here -- one is
what are the characteristics of a stable glaze
(about which you know much more than I do)
and, two, what manner of analysis makes it
easiest to understand what's going on in
a glaze.
I suspect that the concept of a limit formula
to determine the characteristics of a stable
glaze is not wrong as such, but using the
unity formula consistently shows results=3D20
that are 'out of range' for known stable=3D20
glazes, and sometimes glazes within
range that are not stable.
My point on this is while unity may show one
glaze to have a Si ratio of 2 -- generally
conceded to be too low for a 'good' glass --
it may have perfectly sufficient Silica in
the mix, but a very high concentration of
fluxes (either because of the fluxes chosen
or because of the level of anti-fluxing
agents in the glaze).
My focus is not on the formulation of safe
glazes as such, but on alternatives to the
unity analysis that may give more comprehensible
results.
Best -- Steve Slatin =3D20
--- On Thu, 10/22/09, John Hesselberth wrote:
> On Oct 22, 2009, at 6:40 PM, Steve
> Slatin wrote:
>=3D20
> > (Rarely do you see a
> > silica molar concentration at 80% for
> > a cone 10 glaze, and the lowest I've ever
> > seen for a cone ten was just over 50%.
> > High 50's to mid-70's is the sweet spot
> > for cone 10.=3DA0 OTOH, 50% is just about
> > right for most 04 - 06 glazes.)
>=3D20
> Hi Steve,
>=3D20
> You and I have a fundamental disagreement here. The
> difference between
> stable glazes at the various temperatures is primarily the
> type of
> fluxes--not the amount of silica and alumina. Earthenware
> glazes have
> more alkalis and/or boron and high fire glazes have more
> alkaline
> earths and little or no boron or zinc.=3DA0 Both, if they
> are stable,
> have similar levels of silica and alumina. Unity formulas
> show that
> very nicely, but if you would rather think in mole % that
> will work
> too.=3DA0 One method is not better than the other. Now I
> agree that the
> literature is full of lower temperature glazes that fit
> your criteria,
> but test them for stability and you will find a lot of
> garbage.
>=3D20
> Think of it this way. Glazes have to perform at room
> temperature. They
> don't really care what temperature they were fired to. They
> just care
> about their composition and whether or not they were fully
> melted so
> they could form a "good glass". If their silica and alumina
> levels are
> too low they will not have been able to form a good glass.
>=3D20
> Regards,
>=3D20
> John
> =3D0A=3D0A=3D0A
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