Lili Krakowski on tue 8 jun 10
Long have used sand instead of grog. Actually I buy premixed clay these =
=3D
days, but for sculpture etc add sand.
It is cheap. And, unlike grog, it does not sop up water. Yes,one can =3D
dampen grog before adding it, but why do extra work for something that =3D
costs more? (This is when you edge it in--not, obviously, when mixing =3D
up a batch of clay.)
I go to a large construction supply place and buy a bag of white silica =3D
sand...
Lili Krakowski
Be of good courage
tony clennell on wed 9 jun 10
Lili: There is another good reason not to use grog- lime
contamination. We have found that grog is not a sure bet in the
quality dept. Sometimes bricks from lime kilns are ground up to make
grog. A friend has experienced lime pops from using coarse grog. We
have two quality clay suppliers here in Ontario- Pottery Supply House
and Tucker's. Neither of them use grog in their clays. They use sand
or kyanite. They make and sell a lot of clay and know that grog can
come back to bite them.
cheers,
Tony
On Tue, Jun 8, 2010 at 7:26 PM, Lili Krakowski wr=
ote:
> Long have used sand instead of grog. Actually I buy premixed clay these =
days, but for sculpture etc add sand.
>
> It is cheap. And, unlike grog, it does not sop up water. Yes,one can da=
mpen grog before adding it, but why do extra work for something that costs =
more? (This is when you edge it in--not, obviously, when mixing up a batch=
of clay.)
>
> I go to a large construction supply place and buy a bag of white silica s=
and...
> Lili Krakowski
> Be of good courage
>
--
http://sourcherrypottery.com
http://smokieclennell.blogspot.com
Lee Love on thu 10 jun 10
On Wed, Jun 9, 2010 at 2:40 PM, tony clennell wro=
=3D
te:
> or kyanite. They make and sell a lot of clay and know that grog can
> come back to bite them.
Tony, I use some great fireclay grog Tim Frederich gave me
tfrederich@gmail.com .
They fire the natural fire clay and then size the particles. I
like the variable sized grog the best. It gives some variability to
industrial materials. No problems with lime.
--
Lee, a Mashiko potter in Minneapolis
http://mingeisota.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
Hank Murrow on thu 10 jun 10
--Apple-Mail-1--583446079
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain;
charset=3Dus-ascii
On Jun 10, 2010, at 4:03 PM, Eric Hansen wrote:
> Tony: "sand or kyanite" - question: does using kyanite change the =3D
firing
> range? It is a local product here -
Dear Eric;
I use 1/3 Kyanite in my Tea body to increase the refractory quality and =3D
give the body some tooth. Depending on what tooth you need, use 35 or 48 =
=3D
mesh Kyanite. Kyanite is 70% Alumina.
The rest is a splash of feldspar, 1/3 ball clay, and 1/3 kaolin. plus 1% =
=3D
Vee Gum T added to the hot water before mixing. mix until smooth and add =
=3D
the plastic materials first, Kyanite last. I dry this body out in =3D
polyester bags which yields a very workable body despite its =3D
constituents.
Cheers, Hank
--Apple-Mail-1--583446079
Content-Transfer-Encoding: 7bit
Content-Type: text/plain;
charset=3Dus-ascii
The Tea body.......
--Apple-Mail-1--583446079--
Ron Roy on thu 10 jun 10
Tuckers does use grog - Mulcoa - be careful with sand - it adds quartz and
quartz goes through a sudden reduction in size at 573C and is the leading
cause of bisque dunting.
RR
On Wed, Jun 9, 2010 at 3:40 PM, tony clennell wrot=
e:
> Lili: There is another good reason not to use grog- lime
> contamination. We have found that grog is not a sure bet in the
> quality dept. Sometimes bricks from lime kilns are ground up to make
> grog. A friend has experienced lime pops from using coarse grog. We
> have two quality clay suppliers here in Ontario- Pottery Supply House
> and Tucker's. Neither of them use grog in their clays. They use sand
> or kyanite. They make and sell a lot of clay and know that grog can
> come back to bite them.
> cheers,
> Tony
>
> On Tue, Jun 8, 2010 at 7:26 PM, Lili Krakowski
> wrote:
> > Long have used sand instead of grog. Actually I buy premixed clay thes=
e
> days, but for sculpture etc add sand.
> >
> > It is cheap. And, unlike grog, it does not sop up water. Yes,one can
> dampen grog before adding it, but why do extra work for something that co=
sts
> more? (This is when you edge it in--not, obviously, when mixing up a bat=
ch
> of clay.)
> >
> > I go to a large construction supply place and buy a bag of white silica
> sand...
> > Lili Krakowski
> > Be of good courage
> >
>
>
>
> --
> http://sourcherrypottery.com
> http://smokieclennell.blogspot.com
>
--
Ron Roy
15084 Little Lake Road
Brighton, Ontario, Canada
K0K 1H0
Lee Love on thu 10 jun 10
On Thu, Jun 10, 2010 at 6:07 PM, Eric Hansen
wrote:
> Lee: How do they make it? Trade secret? Is there an easy way >to make you=
=3D
own in limited quantities?
Tim says the clay is put on a slab and fired in the kiln. Then it is
sieved to size. I like the unsieved grog because it gives mixed
particle size. The clay, all by itself, fires to cone 9.
--
Lee, a Mashiko potter in Minneapolis
http://mingeisota.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 thu 10 jun 10
Lee: How do they make it? Trade secret? Is there an easy way to make you ow=
=3D
n
in limited quantities?
h a n s e n
On Thu, Jun 10, 2010 at 1:14 AM, Lee Love wrote:
> On Wed, Jun 9, 2010 at 2:40 PM, tony clennell
> wrote:
>
> > or kyanite. They make and sell a lot of clay and know that grog can
> > come back to bite them.
>
> Tony, I use some great fireclay grog Tim Frederich gave me
> tfrederich@gmail.com .
>
> They fire the natural fire clay and then size the particles. I
> like the variable sized grog the best. It gives some variability to
> industrial materials. No problems with lime.
>
> --
> Lee, a Mashiko potter in Minneapolis
> http://mingeisota.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 thu 10 jun 10
Tony: "sand or kyanite" - question: does using kyanite change the firing
range? It is a local product here -
h a n s e n
On Wed, Jun 9, 2010 at 3:40 PM, tony clennell wrot=
e:
> Lili: There is another good reason not to use grog- lime
> contamination. We have found that grog is not a sure bet in the
> quality dept. Sometimes bricks from lime kilns are ground up to make
> grog. A friend has experienced lime pops from using coarse grog. We
> have two quality clay suppliers here in Ontario- Pottery Supply House
> and Tucker's. Neither of them use grog in their clays. They use sand
> or kyanite. They make and sell a lot of clay and know that grog can
> come back to bite them.
> cheers,
> Tony
>
> On Tue, Jun 8, 2010 at 7:26 PM, Lili Krakowski
> wrote:
> > Long have used sand instead of grog. Actually I buy premixed clay thes=
e
> days, but for sculpture etc add sand.
> >
> > It is cheap. And, unlike grog, it does not sop up water. Yes,one can
> dampen grog before adding it, but why do extra work for something that co=
sts
> more? (This is when you edge it in--not, obviously, when mixing up a bat=
ch
> of clay.)
> >
> > I go to a large construction supply place and buy a bag of white silica
> sand...
> > Lili Krakowski
> > Be of good courage
> >
>
>
>
> --
> http://sourcherrypottery.com
> http://smokieclennell.blogspot.com
>
Vince Pitelka on fri 11 jun 10
Ron Roy wrote:
"Tuckers does use grog - Mulcoa - be careful with sand - it adds quartz and
quartz goes through a sudden reduction in size at 573C and is the leading
cause of bisque dunting."
Hi Ron -
I wish I understood more of the mechanics of this situation. Of the
claybodies containing sand or grog that we make up at the Craft Center, the
most reliable has been the Mackenzie body, which contains 15% fine silica
sand. We have very little problem with that body dunting, and curiously, w=
e
seem to have more dunting problems in bodies containing grog. That probabl=
y
depends on which grog we are using. I am away from the Craft Center for th=
e
summer, so I do not know what grog we are using currently, but I could find
out. I have always been concerned about the problem you mention above, and
had assumed that grog is usually a better choice than sand for adding grit
to a claybody. In my sixteen years at the Craft Center that Mackenzie body
has remained pretty reliable and consistent, even with periodic changes in
sand suppliers.
The recipe for the Mackenzie C-10 Stoneware is:
Fire clay - 30.8
Goldart - 30.8
OM-4 - 15.4
Fine silica sand - 15.4
G-200 - 7.6
Total - 100
Thanks -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Ron Roy on fri 11 jun 10
Hi Vince,
Well fine sand is easier on clay than the bigger stuff to that helps -
but it may be as simple as how fast a kiln is cooling - I wonder how
well that body would work in a thin walled electric kiln?
I mixed Hoppers porcelain when he lived here in Ontario years ago and
it had 10% fine silica sand - and some of the bodies that Tuckers
sells has fine silica (110M) in them and they have not been a problem.
It seems clear to me that mesh size is an important factor and my
remark is meant to warn those who start adding say building sand into
clay bodies - be careful and know what to watch for.
More on the Mackenzie body when you return in the fall - the
dilatometer will tell us lots.
RR
Quoting Vince Pitelka :
> Ron Roy wrote:
> "Tuckers does use grog - Mulcoa - be careful with sand - it adds quartz a=
nd
> quartz goes through a sudden reduction in size at 573C and is the leading
> cause of bisque dunting."
>
> Hi Ron -
> I wish I understood more of the mechanics of this situation. Of the
> claybodies containing sand or grog that we make up at the Craft Center, t=
he
> most reliable has been the Mackenzie body, which contains 15% fine silica
> sand. We have very little problem with that body dunting, and curiously,=
we
> seem to have more dunting problems in bodies containing grog. That proba=
bly
> depends on which grog we are using. I am away from the Craft Center for =
the
> summer, so I do not know what grog we are using currently, but I could fi=
nd
> out. I have always been concerned about the problem you mention above, a=
nd
> had assumed that grog is usually a better choice than sand for adding gri=
t
> to a claybody. In my sixteen years at the Craft Center that Mackenzie bo=
dy
> has remained pretty reliable and consistent, even with periodic changes i=
n
> sand suppliers.
>
> The recipe for the Mackenzie C-10 Stoneware is:
> Fire clay - 30.8
> Goldart - 30.8
> OM-4 - 15.4
> Fine silica sand - 15.4
> G-200 - 7.6
> Total - 100
>
> Thanks -
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
>
Joseph Herbert on sat 12 jun 10
Vince was writing about the mechanics of dunting. I have only experienced
dunting once. It may give some insight.
I had bought a wheel and was throwing in the kitchenette of a motel in
Palacios, Texas. This remote place did have a "Greenware Lady" who dealt i=
n
slip casting and various kinds of decorative activity. I contracted with
her to fire my wonderful (eye-of-the-beholder) pots so I could transport
them back to Dallas for high fire. In each firing, there was at least one
pot that experienced dunting.
I was throwing stoneware bowls that were fairly large (for me) and that had
rather thick bottoms and foot rings. I gave them to the firer in bone dry
(for the Texas Gulf Coast) condition.
She would stack the pieces one on the other and fire. No shelves, just a
stack. She then fired using her normal methods. I got Dunting!
My eventual analysis of this is as follows: Her firing pattern was
developed and suited her ware that was all one thickness. Any slip case
piece will have a uniform thickness everywhere. My pieces varied greatly in
thickness. The rims of the bowls were too thin, the bases too thick. When
fired by her pattern with rapid cooling, that her thin, single thickness
pieces could easily stand, my pieces cracked across the foot ring.
How so? The contraction of the rims of the bowls during the quartz
transformation made the upper parts of the bowls smaller. The thicker foot
ring, protected from cooling inside the stack of pottery remained
un-transformed and larger. The contraction of the upper part of the bowl
was sufficient to pull apart the foot ring. The reduction in size would be
equivalent to internal crowbars prying upward all around the foot ring. An=
y
stress riser in the foot initiates the crack that goes across the foot ring
and relieves the stress.
My dunting story. Not before, not since. The bottoms are a little thinner=
,
the lips a little thicker, but the firing makes the difference. Not
stacked, distributed on shelves, relatively slow cooling.
Joe
Joseph Herbert
Training Developer
Neon-Cat on sat 12 jun 10
Bet you didn't know that you can make kyanite right in your kiln.
Take some pyrophyllite and heat it, it dehydrates at low temperature
(100 C plus) and turns into kyanite:
Al2Si4O10(OH)2 ---> Al2SiO5 + 3SiO2 + H2O
1 pyrophyllite yields 1 kyanite plus 3 quartz + water (vapor)
In clay bodies made up of materials that contain even small amounts of
water in their crystalline structure, melting increases somewhat
and/or begins slightly earlier. The term for this is "dehydration
melting".
Kyanite has a high melting point -- 1820 C (3308 F).
Marian
Neon-Cat
Paul Herman on sat 12 jun 10
Hi Joe,
It sounds to me like you are right on for the reasons you got dunting,
and if you were throwing in the kitchenette of a motel in
Palacios, Texas then I think you are a real trouper.
Here, I still bisque fire plates and bowls in stacks, but place dry
wads or chips between each piece, allowing the heating (and especially
the cooling) to circulate in there between the pots by convection. I
haven't had a bisque dunt in years. It's good to make every effort to
heat and cool pots as evenly as possible.
Good bisquings to all,
Paul Herman
Great Basin Pottery
Doyle, California US
www.greatbasinpottery.com/
On Jun 11, 2010, at 11:02 PM, Joseph Herbert wrote:
just a
stack. She then fired using her normal methods. I got Dunting!>
> My dunting story. Not before, not since. The bottoms are a little
> thinner,
> the lips a little thicker, but the firing makes the difference. Not
> stacked, distributed on shelves, relatively slow cooling.
>
> Joe
>
> Joseph Herbert
> Training Developer
| |
|
