Sumi von Dassow on thu 1 apr 10
Lou
I'm far from a shino expert but I've used Diana Pancioli's cone 6 shino
(firing at cone 7) on clays from porcelain to b-mix to buff stoneware.
On porcelain and B-mix it carbon traps if it's in the right place in my
kiln; on iron-bearing bodies it tends to go gold instead of
getting black carbon trapping if it's fired right. When I add 6% redart
to the recipe, as in the Malcolm Davis recipe, it tends to go
gold instead of black on white clays, too, though it will trap carbon in
places if the reduction is heavy enough. So my experience
leads me to believe that iron tends to react with the soda ash to create
a gold color, which I liken to the color of a pot fumed with
ferric chloride in a raku firing. I have used Malcolm's recipe at cone
7, also, and it produced black and gold on porcelain and white
stoneware (B-mix), and gold on iron-bearing stonewares.
Sumi
> Does anyone have any explanations for these questions?
>
> Is it true that shinos trap carbon more effectively on porcelain than on
> stoneware? If so,why?
>
> My limited experience with stoneware is that with Malcolm Davis's shino, =
it
> is a solid brown and traps no carbon at all. I assume it is the iron cont=
ent
> in the clay that makes this happen. But some stoneware may work ok. I wou=
ld
> like to know.
>
> Thanks.
>
> Lou Raye
>
>
> Lou Raye Nichol
> Carbon Trapped Porcelain
> 919-303-5848
> www.louraye.com
> pots@louraye.com
>
>
>
--
Sumi von Dassow
www.herwheel.com
sumi@herwheel.com
Lou Raye Nichol on thu 1 apr 10
Does anyone have any explanations for these questions?
Is it true that shinos trap carbon more effectively on porcelain than on
stoneware? If so,why?
My limited experience with stoneware is that with Malcolm Davis's shino, it
is a solid brown and traps no carbon at all. I assume it is the iron conten=
t
in the clay that makes this happen. But some stoneware may work ok. I would
like to know.
Thanks.
Lou Raye
Lou Raye Nichol
Carbon Trapped Porcelain
919-303-5848
www.louraye.com
pots@louraye.com
Lee Love on sun 4 apr 10
Carbon trapping seems to be related to high amounts of solubles in the
glaze, early reduction and fast drying after glaze application. The
fast drying pulls the solubles out of the clay and deposits them in
the glaze.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
David Finkelnburg on sun 4 apr 10
Lou Raye,
I hope someone else has posted this already. Any clay body/glaze
composition can trap carbon. It just takes the right conditions. As an
example, right now I am holding a stoneware drinking vessel (I dare not cal=
l
it anything else without committing for cultural trespass...). This cup
with no handle is glazed with a pale blue celadon and on one side, both
inside and out, it is black black...from carbon trapping. Lee Burningham's
students used to routinely carbon trap on Laguna's stoneware called Soldate
60, using two different versions of Malcolm Davis Shinos.
Basically, carbon trapping is the condensation of carbon atoms from
reduced fuel onto the pot--which occurs because the pot is cooler than the
oxygen-starved flame that's reducing the fuel--*before* the glaze melts
enough to seal over and "trap" the carbon. Therefore any glaze that melts
enough to seal in the trapped carbon and prevent it from being burned off
when oxygen may invade the kiln during the cooling cycle is capable of
carbon trapping. The clay and glaze combination, however, may not reveal
the carbon to best advantage like American Shino on porcelain does.
Also, because glaze melts in part because of how it interacts with the
clay it is applied to, the temperature at which the glaze seals over may be
different for a given stoneware than for a porcelain. Thus it may be that
in one firing getting both porcelain and stoneware to trap carbon the same
from the same glaze may be challenging.
Iron in American Shino serves mainly to provide color and
visual interest away from areas of trapped carbon.
Good potting!
Dave Finkelnburg
http://www.mattanddavesclays.com
> Is it true that shinos trap carbon more effectively on porcelain than on
> stoneware? If so,why?
>
> My limited experience with stoneware is that with Malcolm Davis's shino,
it
> is a solid brown and traps no carbon at all. I assume it is the iron
content
> in the clay that makes this happen. But some stoneware may work ok. I
would
> like to know.
> Lou Raye
Lee Love on mon 5 apr 10
Japan was incredibly humid, especially during rainy season. We
always made use of the sun and wind when we could.
Another way to fast dry, is putting the work out in the sun,
where the wind can catch the work.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
Lee Love on mon 5 apr 10
On Mon, Apr 5, 2010 at 11:06 AM, David Finkelnburg
wrote:
> =3DA0=3DA0=3DA0 It is difficult to load immediately and fire a pot glazed=
with =3D
an
> American Shino.
Got it. You haven't tried fast drying so you have no
empirical data.. I do this safely all the time.
If your kiln won't work, simply set your oven to 200*F
and stick your pots in. If you have a pyrometer on your electic
kiln, that will work too.
Try it!
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
David Finkelnburg on mon 5 apr 10
Lee,
I understand you have not observed carbon trapping by Japanese Shino
glazes. That is not the intent with those glazes. Any glaze which melts
can trap carbon.
It is difficult to load immediately and fire a pot glazed with an
American Shino. The high clay level in the glaze causes the glaze to dry
with difficulty. It tends to suffer steam expansion in the kiln that blows
bits of the wet glaze all over. :-( If you candle long enough you can
dry the moisture out of the wet glaze. One will see a different pattern du=
=3D
e
to soluble accumulation on the surface than drying somewhere else. It's
location and air movement, though, that makes the difference, not length of
drying time.
Dave
On Mon, Apr 5, 2010 at 9:31 AM, Lee Love wrote:
> David,
>
> Try this to test: glaze a bunch of pots with a carbon trap
> glaze.. Let them try slowely for several days. Glaze another set
> of pots and put them in the kiln, right before starting it up to fire.
>
> You can also resist over the glaze to slow drying and keep
> solubles from getting to the surface of the glaze.
>
> Japanese shinos do not carbon trap.
>
> --
> Lee, a Mashiko potter in Minneapolis
> http://mashikopots.blogspot.com/
>
> =3D93Observe the wonders as they occur around you. Don't claim them. Feel
> the artistry moving through and be silent.=3D94 --Rumi
>
Lee Love on mon 5 apr 10
David,
Try this to test: glaze a bunch of pots with a carbon trap
glaze.. Let them try slowely for several days. Glaze another set
of pots and put them in the kiln, right before starting it up to fire.
You can also resist over the glaze to slow drying and keep
solubles from getting to the surface of the glaze.
Japanese shinos do not carbon trap.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
David Finkelnburg on mon 5 apr 10
Lee,
What you have written below is partly true, yet to me seems only
incidental to, not the cause of, carbon trapping. American Shino glazes,
which seem to be descendants of the work of Virginia Wirt, do use soluble
sodium and where the sodium dries on the surface it does trap carbon very
effectively. Early reduction, however, is simply required because high
sodium glazes melt early and the carbon needs to be made and deposited on
the ware before that melting occurs. Wirt, btw, also used spodumene
(lithium-rich feldspar) which also melts at a relatively low temperature,
thus needing early reduction.
Fast drying is irrelevant. The solubles are contributed by the glaze,
not the clay. American Shinos typically take much more time to dry than
most glazes. In the dry climate here in Idaho they still take up to 24
hours to dry because they contain so much clay. What is important is, as
you note, the solubles get to the glaze surface. Wrapping the pot
irregularly lets the solubles deposit on the surface in irregular patterns.
Application of wax stops surface soluble deposition entirely where the wax
is applied--thus painting with wax is a method of decorating on damp Am.
Shino glaze. Irregular air flow can cause more solubles to deposit on one
side than the other of a pot. The techniques used to achieve variation in
carbon trapping are many!
While Am. Shino uses lots of solubles, it is still possible to carbon
trap with any glaze. It's just usually not done...at least, not on
purpose. :-)
All the best,
Dave Finkelnburg
On Sun, Apr 4, 2010 at 8:15 PM, Lee Love wrote:
> Carbon trapping seems to be related to high amounts of solubles in the
> glaze, early reduction and fast drying after glaze application. The
> fast drying pulls the solubles out of the clay and deposits them in
> the glaze.
>
>
>
> --
> Lee, a Mashiko potter in Minneapolis
> http://mashikopots.blogspot.com/
>
> =3D93Observe the wonders as they occur around you. Don't claim them. Feel
> the artistry moving through and be silent.=3D94 --Rumi
>
Eric Hansen on mon 5 apr 10
Lou: You've posted an interesting question - true Mino/Seto Japanese shino
isn't really a carbon trap glaze. The glaze which originated in the U.S.A.
as "University Carbon Trap" later became known as "shino" (I won't mention
any names as to who did this) but often we now call it "American Shino" or
so on and so forth. This American formula does tend to trap carbon - but
then also carbon is excessively introduced into the clay body (viz OM4) and
the reduction firing procedure is managed in such a manner that not all of
the carbon can out-gas before the glaze is cooled capturing the smokiness.
having just driven through Eastern Kentucky on I-64 you can find quite a fe=
w
heavy carbon bearing Kentucky ball clays at the various road-cuts & if you
can get some that might work. Normally the bagged and processed clays are
rated lower in carbon. As far as porcelain trapping carbon better, that
might depend on whether the clays used have carbon in them. Some porcelain
recipes will have none. h a n s e n
On Thu, Apr 1, 2010 at 6:36 PM, Lou Raye Nichol <
louraye@businesscoachinstitute.com> wrote:
> Does anyone have any explanations for these questions?
>
> Is it true that shinos trap carbon more effectively on porcelain than on
> stoneware? If so,why?
>
> My limited experience with stoneware is that with Malcolm Davis's shino, =
it
> is a solid brown and traps no carbon at all. I assume it is the iron
> content
> in the clay that makes this happen. But some stoneware may work ok. I wou=
ld
> like to know.
>
> Thanks.
>
> Lou Raye
>
>
> Lou Raye Nichol
> Carbon Trapped Porcelain
> 919-303-5848
> www.louraye.com
> pots@louraye.com
>
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