dianamp@COMCAST.NET on tue 16 nov 10
Hi Clayart:
While our Fake Ash formula at cone 6 Reduction works very well
sometimes, at other times it forms little blister/pimples.
I haven't been able to figure out why it does so when it does blister.
Does anyone have a clue? More or less reduction? Needs rescreening? . . . .
Thanks again.
Diana Pancioli
Vince Pitelka on tue 16 nov 10
Diana Pancioli wrote:
"While our Fake Ash formula at cone 6 Reduction works very well =3D
sometimes, at other times it forms little blister/pimples. I haven't =3D
been able to figure out why it does so when it does blister. Does =3D
anyone have a clue? More or less reduction? Needs rescreening? . . . ."
Hi Diana -=3D20
This is just a guess. Fake ash glazes usually run in order to get the =3D
ash effect, and thus are usually pretty heavily fluxed. Glazes with =3D
higher concentrations of fluxes tend to boil or bubble more, especially =3D
in a reduction atmosphere. Are you doing an oxidation cleanup at the =3D
end? This almost always gives brighter colors and less glaze flaws. In =
=3D
an earlier message about a different glaze issue, Ron Roy recommended a =3D
soak 100 degrees Fahrenheit below maturation temperature at the end of =3D
the firing, and I would recommend the same thing, making sure that the =3D
kiln is oxidizing. The best way to do this is with a pyrometer. Don't =3D
expect the actual temperature reading on the pyrometer to be very =3D
accurate at that temperature, but you can use it to watch the kiln drop =3D
100 degrees, and then adjust the burners to hold it there in an =3D
oxidation atmosphere for at least half an hour. That should help heal =3D
the glaze acne. =3D20
Hope this helps. Please let us know one way or the other.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu=3D20
http://iweb.tntech.edu/wpitelka
=3D20
Dan Hill on wed 17 nov 10
Diana Wrote
While our Fake Ash formula at cone 6 Reduction works very well
sometimes, at other times it forms little blister/pimples.
I haven't been able to figure out why it does so when it does blister.
Does anyone have a clue? More or less reduction? Needs rescreening? . . . =
.
I have tested that glaze and have been successful with it on Porcelain and
with my reclaim which is a combo of porc and stoneware which I add abit of
fireclay and red art to. The fake ash glaze does not work on mid white
stoneware which is a Tuckers claybody. It blisters badly, so I would agree
with Ron that the claybody is gassing off at ^6 and causing the problem.
Ron, I have the same problem with some other glazes on the same claybody
soda fired to ^6 in reduction . Is there an ingredeint in mid-white that ma=
y
be causing the blisters or could it be the combination of Soda firing and
temp. that is causing the claybody to be over fired and starting to break
down?
Dan Hill
Hill Pottery
^6 soda fired Porc. and Stoneware
Bob Johnson on wed 17 nov 10
Ron: I have found Andie's Golden Fake Ash (recipe below) to be quite =3D
reliable at cone 6, in either oxidation or reduction. It also works well =
=3D
with Val Cushing's G-4 Ash--which uses actual wood ash which is somewhat =
=3D
runnier.=3D20
ANDIE'S GOLDEN FAKE ASH
Redart 27
Dolomite 24
O.M. #4 20
Strontium 12
Gerstley borate 10
Bone ash 5
Lithium 2
I have seen some other recipes that look quite similar, including =3D
Pancioli's Fake Ash and Faux Ash (the latter was in Clay Times, May/June =
=3D
2006).
I'll be interested to know what you find out, Ron.
Best,
Bob
Southern Oregon
Ron Roy on wed 17 nov 10
Hi Dan,
There is nothing particularly different about mid white - It's made up
with the same materials as many of Tuckers other clay bodies.
Can you send me the batch number of your midwhite - I can look up the
test results and see if there is a clue there but I can tell you the
test results are in a normal range for all batches over the last 10
years.
I think you use one of their porcelains and I would think there would
be blistering with that kind of body more - because it is closer to
vitrification.
Could it be that your bisque firing is not getting all the organics
burned out - do you bisque in your gas kiln? Are you sure there is no
reduction during that firing? There is Hawthorn fire clay in that body
- which means there are specks of iron - if they get reduces during a
bisque firing - because of a reducing atmosphere and/or because there
is not enough oxygen present to support combustion of organics in the
body then - those reduced iron specks will become a strong flux and
over flux the clay around them.
I'm just saying that can be a problem sometimes.
I am working on trying to reformulate an ash glaze for someone now. I
see that the glaze is over fluxed - way short of silica - glazes like
that can be prone to problems.
If anyone has a fake cone 6 ash glaze - I would like to see as many as
possible - I will promise to publish what I find out to anyone who can
help with this.
Dan - what does your glaze look like when it's right?
RR
Quoting Dan Hill :
> Diana Wrote
>
> While our Fake Ash formula at cone 6 Reduction works very well
> sometimes, at other times it forms little blister/pimples.
>
> I haven't been able to figure out why it does so when it does blister.
> Does anyone have a clue? More or less reduction? Needs rescreening? . . .=
.
>
> I have tested that glaze and have been successful with it on Porcelain an=
d
> with my reclaim which is a combo of porc and stoneware which I add abit o=
f
> fireclay and red art to. The fake ash glaze does not work on mid white
> stoneware which is a Tuckers claybody. It blisters badly, so I would agre=
e
> with Ron that the claybody is gassing off at ^6 and causing the problem.
>
> Ron, I have the same problem with some other glazes on the same claybody
> soda fired to ^6 in reduction . Is there an ingredeint in mid-white that =
may
> be causing the blisters or could it be the combination of Soda firing and
> temp. that is causing the claybody to be over fired and starting to break
> down?
>
> Dan Hill
> Hill Pottery
> ^6 soda fired Porc. and Stoneware
>
Ron Roy on thu 18 nov 10
Thanks Bob,
I have some tests out there now and will generate some more when I see
the results - Have you ever had any pin holes or blistering?
RR
Quoting Bob Johnson :
> Ron: I have found Andie's Golden Fake Ash (recipe below) to be quite
> reliable at cone 6, in either oxidation or reduction. It also works
> well with Val Cushing's G-4 Ash--which uses actual wood ash which is
> somewhat runnier.
>
> ANDIE'S GOLDEN FAKE ASH
> Redart 27
> Dolomite 24
> O.M. #4 20
> Strontium 12
> Gerstley borate 10
> Bone ash 5
> Lithium 2
>
> I have seen some other recipes that look quite similar, including
> Pancioli's Fake Ash and Faux Ash (the latter was in Clay Times,
> May/June 2006).
>
> I'll be interested to know what you find out, Ron.
>
> Best,
> Bob
> Southern Oregon
>
>
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