Ray Bogle on mon 7 dec 09
Hi Folks,
I do predominitely thrown raku work but have begun working with some
stoneware slabs and to my dismay I'm having a terrible time keeping them
flat during the cone 6 firing. I make them with a slab roller and then
dry them slowly between sheets of drywall so they stay flat during the
drying. They also stay flat during the bisque firing. BUT.....when I
fire them to cone 6, they do all sorts of things. They twist, they
curl, corners curl up....all this happens with the slab laying on a
perfectly flat kiln shelf! I've fired a single slab and layed slabs on
top of each other for a small amount of weight on the lowest slab and
even the lowere slab can get tweaked??
So someone fill me in.....what do I need to be doing to keep slabs flat
during the cone 6 firing?? BTW, these slabs do not have an glaze on
them, just plain old clay.
Ray
>
L TURNER on mon 7 dec 09
Ray,
How big, how thick, and do they sit flat on the kiln shelf?
Regards,
L. Turner
On
Vince Pitelka on mon 7 dec 09
Ray Bogle wrote:
"I do predominately thrown raku work but have begun working with some
stoneware slabs and to my dismay I'm having a terrible time keeping them
flat during the cone 6 firing. I make them with a slab roller and then dry
them slowly between sheets of drywall so they stay flat during the drying.
They also stay flat during the bisque firing. BUT.....when I fire them to
cone 6, they do all sorts of things. They twist, they curl, corners curl
up....all this happens with the slab laying on a perfectly flat kiln shelf!=
"
Ray -
How do you roll your slabs? Do you cross roll from both sides, either in
your slab-roller or with a rolling pin after the slab roller? The exact
symptoms you describe can be caused by clay memory and grain structure in
the slabs. Unless you can neutralize or minimize that memory and grain
structure you will have the kind of troubles you describe.
I only rarely work with flat slabs that are not part of a 3-D piece, but I
have not had problems with them warping during the firing as long as the
grain structure is minimized and the slabs are evenly supported in drying
and firing. I roll slabs in a Brent SR-20 slab-roller, which only rolls
from one side. Once the initial slab is rolled, I cross-roll it in multipl=
e
directions with a rolling pin, flip it over, and do the same on the other
side. That pretty much eliminates the grain structure and minimizes the
resulting clay memory.
Hope that helps.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
marci and rex on mon 7 dec 09
At 02:10 PM 12/7/2009, Ray Bogle wrote:
>So someone fill me in.....what do I need to be doing to keep slabs flat
>during the cone 6 firing?? BTW, these slabs do not have an glaze on
>them, just plain old clay.
I dont know if this will help with your clay .. but
with the cone 6 porcelain I do, I find I have better luck if
I roll it in different directions..
Roll, flip over and roll in another direction , flip, roll
in another direction ...
Then , when I lay the pieces out to dry , I press
them down with my hands ....
marci
Mayssan Farra on tue 8 dec 09
Hello Ray:
It all depends on your clay, method of rolling and such.
But I can tell you about my slabs: I stretch/ compress the clay by throwin=
g it on a flat surface a few times in different directions, then I will giv=
e it a few passes with the slab roller also in different directions and ups=
ide down as I lower the rollers until I reach my desired height, 1/4" -1/2"=
depending on how big the slab is. I sometimes apply additions and things t=
o the top to make it a flat tray so drying , once stiff, is always on newsp=
apers on a wire shelf covered with plastic from the top inside my humid cab=
inet ( it really is a mini green house:). I don't have any warping problems=
as long as I follow this. I do glaze the topside of these trays/decorated =
flat slabs.
Mayssan, in Charleston WV where winter is in full swing.
Mayssan Shora Farra
http://www.clayvillepottery.com
http://clayette.blogspot.com
From: Ray Bogle working with some
> stoneware slabs and to my dismay I'm having a terrible time keeping them
> flat during the cone 6 firing.
Ray Bogle on tue 8 dec 09
Thanks Mayssan and the others that repsonded.......
I see a common theme (much of which I was not doing) of rotating the
slab, rolling smoothly, and ensuring the slab is even. I'll give these
a techniques a try and I suspect that my next batch of slabs will be
much flatter than the last batch of curved, crooked, and warped pieces
of clay :)
Thanks,
Ray
www.madewithclay.com
Mayssan Farra wrote:
> Hello Ray:
>
> It all depends on your clay, method of rolling and such.
>
> But I can tell you about my slabs: I stretch/ compress the clay by throw=
ing it on a flat surface a few times in different directions, then I will g=
ive it a few passes with the slab roller also in different directions and u=
pside down as I lower the rollers until I reach my desired height, 1/4" -1/=
2" depending on how big the slab is. I sometimes apply additions and things=
to the top to make it a flat tray so drying , once stiff, is always on new=
spapers on a wire shelf covered with plastic from the top inside my humid c=
abinet ( it really is a mini green house:). I don't have any warping proble=
ms as long as I follow this. I do glaze the topside of these trays/decorate=
d flat slabs.
>
>
> Mayssan, in Charleston WV where winter is in full swing.
>
>
> Mayssan Shora Farra
>
> http://www.clayvillepottery.com
>
> http://clayette.blogspot.com
>
>
>
>
> From: Ray Bogle working with some
>
>> stoneware slabs and to my dismay I'm having a terrible time keeping them
>> flat during the cone 6 firing.
>>
>
>
>
>
>
>
Chris Campbell on tue 8 dec 09
Elizabeth Priddy came up with a
fool proof method of keeping any
slab/tile flat as a pancake.
Roll out slab
Roll in opposite direction
Cut to size
Place on paper, then on a board
Drop board from waist height
once or twice
Leave the tiles alone til hard
Yes, leave them alone!
No drywall, no plastic ... you can
leave them out in the sun.
No warping at all unless you move
them around.
Chris Campbell - in North Carolina
Chris Campbell Pottery LLC
Designs in Colored Porcelain
www.ccpottery.com
http://neriagechris.blogspot.com/
Creative Ways With Colored Clays
PRE-NCECA WEEKEND WORKSHOP
March 26, 27 & 28, 2010
Clay Art Center
40 Beech Street
Port Chester, NY 10573
914.937.2047 x222
http://www.clayartcenter.org
SUMMER WORKSHOP
August 15-21, 2010
Touchstone Center for Crafts
1049 Wharton Furnace Road
Farmington PA 15437
1.800.721.0177
http://www.touchstonecrafts.com
gayle bair on tue 8 dec 09
I might add to the line "Drop board from waist high once or =3D
twice"..........."On a clay-free surface"
You drop that on a floor or surface that has clay dust and you are going =
=3D
to kick up a cloud of clay.
Doing it outside might be a good idea.
I have also tapped (hard) the bottom of the board for pieces that are =3D
not very thick.
Gayle Bair
Bainbridge Island WA
Tucson AZ
gayle@claybair.com
www.claybair.com
On Dec 8, 2009, at 7:38 AM, Chris Campbell wrote:
> Elizabeth Priddy came up with a
> fool proof method of keeping any
> slab/tile flat as a pancake.
>=3D20
> Roll out slab
> Roll in opposite direction
> Cut to size
> Place on paper, then on a board
> Drop board from waist height
> once or twice
> Leave the tiles alone til hard
> Yes, leave them alone!
> No drywall, no plastic ... you can
> leave them out in the sun.
> No warping at all unless you move
> them around.
>=3D20
> Chris Campbell - in North Carolina
>=3D20
>=3D20
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