John Rodgers on thu 2 oct 08
Hopefully one of our gurus can help me here,
The rim warping has been one of the banes of my existence in pottery,
and I have never been able to fully resolve the issue. I make a fairly
large dinner plate/charger - 14 inch dia with a rim approx. 1-1/2 inch
wide for decoration purposes. The rim is carefully angled up and
material at the edge is approx 1/8th in when dry. It thickens quickly
for strength and support from the edge inward towards where the foot
ring is located. This adds extra strength for the cantilever effect of a
rim sticking out in the air with no support.
The charger/plate actually has two foot rings - one smaller on towards
the center of the plate, and a larger one near the outer diameter.
These plate foot rings are ground to perfection on a big sanding sheet I
have set up, so they are in perfect alignment with each other. Theya re
then placedon a perfectly flat round shelf, which has been coated with
loose alumina, to allow for easy movement of the clay as it shrinks. The
clear space between shelves is 3 inches, and there is one plate per
shelf. They are glaze fired to Cone 5, computer controlled firing, and
allowed full cool down to room temp before opening the kiln. Two out of
three plates will have a warped rim. Not terribly so, but not as near
perfection as I would like. I don't feel I can get top dollar for them
with the rims as they are.
I know factory plates are pretty much ALL made from hydraulically
pressing fairly dry clay, and consequently the clay is far more dense
than clay in my plates thrown on a wheel. This will make a difference.
But is there anything else I can do to help prevent/reduce this warpage
- keep it from happening?
I'm using C5 Laguna B-mix.
Thanks,
Regards,
John Rodgers
Chelsea, AL
gayle bair on thu 2 oct 08
John,
From my experience with B-Mix the fastest way to resolve the issue
is ...... use another claybody!!!!
I successfully resolved the issue of join cracks but not the large
platter rim slumping in firing issue.
I also had platter dunting issues with the B-mix which I mostly
resolved with kyanite on the shelving.
The only suggestions I might offer is to try a thicker rim and dry
ever so slowly in a tub with a lid.
If you find a solution do share it!
Gayle Bair
Bainbridge Island WA
Tucson AZ
gayle@claybair.com
www.claybair.com
On Oct 2, 2008, at 7:07 AM, John Rodgers wrote:
> Hopefully one of our gurus can help me here,
>
> The rim warping has been one of the banes of my existence in
> pottery,
> and I have never been able to fully resolve the issue. I make a fairly
> large dinner plate/charger - 14 inch dia with a rim approx. 1-1/2 inch
> wide for decoration purposes. The rim is carefully angled up and
> material at the edge is approx 1/8th in when dry. It thickens quickly
> for strength and support from the edge inward towards where the foot
> ring is located. This adds extra strength for the cantilever effect
> of a
> rim sticking out in the air with no support.
> The charger/plate actually has two foot rings - one smaller on towards
> the center of the plate, and a larger one near the outer diameter.
>
> These plate foot rings are ground to perfection on a big sanding
> sheet I
> have set up, so they are in perfect alignment with each other. Theya
> re
> then placedon a perfectly flat round shelf, which has been coated with
> loose alumina, to allow for easy movement of the clay as it shrinks.
> The
> clear space between shelves is 3 inches, and there is one plate per
> shelf. They are glaze fired to Cone 5, computer controlled firing, and
> allowed full cool down to room temp before opening the kiln. Two out
> of
> three plates will have a warped rim. Not terribly so, but not as near
> perfection as I would like. I don't feel I can get top dollar for them
> with the rims as they are.
>
> I know factory plates are pretty much ALL made from hydraulically
> pressing fairly dry clay, and consequently the clay is far more dense
> than clay in my plates thrown on a wheel. This will make a difference.
> But is there anything else I can do to help prevent/reduce this
> warpage
> - keep it from happening?
>
> I'm using C5 Laguna B-mix.
>
> Thanks,
>
> Regards,
>
> John Rodgers
> Chelsea, AL
David Beumee on thu 2 oct 08
=C2=A0=C2=A0
John,
=C2=A0I submit that your biggest problem is using a clay body with the very=
high ball clay percentage contained in a B-Mix type. A body with more dive=
rse constituents, say a combination of Helmer, Tile 6,=C2=A0EPK and OH #1 b=
all clay,=C2=A0and=C2=A0perhaps=C2=A0a=C2=A0percentage=C2=A0of=C2=A0Molochi=
te=C2=A0grog, I believe would serve you much better and solve the warping p=
roblem. If you're interested in making your own white stoneware body, plea=
se contact me off list and I'll email you my research.
David Beumee
www.davidbeumee.com
-------------- Original message from John Rodgers : ---=
-----------=20
> Hopefully one of our gurus can help me here,=20
>=20=20
> The rim warping has been one of the banes of my existence in pottery,=
=20
> and I have never been able to fully resolve the issue. I make a fairly=20
> large dinner plate/charger - 14 inch dia with a rim approx. 1-1/2 inch=20
> wide for decoration purposes. The rim is carefully angled up and=20
> material at the edge is approx 1/8th in when dry. It thickens quickly=20
> for strength and support from the edge inward towards where the foot=20
> ring is located. This adds extra strength for the cantilever effect of a=
=20
> rim sticking out in the air with no support.=20
> The charger/plate actually has two foot rings - one smaller on towards=20
> the center of the plate, and a larger one near the outer diameter.=20
>=20=20
> These plate foot rings are ground to perfection on a big sanding sheet I=
=20
> have set up, so they are in perfect alignment with each other. Theya re=
=20
> then placedon a perfectly flat round shelf, which has been coated with=20
> loose alumina, to allow for easy movement of the clay as it shrinks. The=
=20
> clear space between shelves is 3 inches, and there is one plate per=20
> shelf. They are glaze fired to Cone 5, computer controlled firing, and=20
> allowed full cool down to room temp before opening the kiln. Two out of=
=20
> three plates will have a warped rim. Not terribly so, but not as near=20
> perfection as I would like. I don't feel I can get top dollar for them=20
> with the rims as they are.=20
>=20=20
> I know factory plates are pretty much ALL made from hydraulically=20
> pressing fairly dry clay, and consequently the clay is far more dense=20
> than clay in my plates thrown on a wheel. This will make a difference.=20
> But is there anything else I can do to help prevent/reduce this warpage=
=20
> - keep it from happening?=20
>=20=20
> I'm using C5 Laguna B-mix.=20
>=20=20
> Thanks,=20
>=20=20
> Regards,=20
>=20=20
> John Rodgers=20
> Chelsea, AL=20=20
Karin Givon on thu 2 oct 08
Hey John, about your warped plates....I throw bowls (to cut) with
really thin rims, and the thinnest ones sometimes warp. I find if I
make the rims a little wider, and just a touch ( with your chamois)
thicker, it helps a lot.
The price we pay for doing fine work, yah?
The great lovely breadbowl guys don't warp, do they.
Well, there ya go.
That b-mix. like throwing cream cheese.
onward through the fog
Karin
DancingDragonPottery.net
Nevada City, CA
On Oct 2, 2008, at 7:07 AM, John Rodgers wrote:
Hopefully one of our gurus can help me here,
The rim warping has been one of the banes of my existence in pottery,
and I have never been able to fully resolve the issue. I make a fairly
large dinner plate/charger - 14 inch dia with a rim approx. 1-1/2 inch
wide for decoration purposes. The rim is carefully angled up and
material at the edge is approx 1/8th in when dry. It thickens quickly
for strength and support from the edge inward towards where the foot
ring is located. This adds extra strength for the cantilever effect of a
rim sticking out in the air with no support.
The charger/plate actually has two foot rings - one smaller on towards
the center of the plate, and a larger one near the outer diameter.
These plate foot rings are ground to perfection on a big sanding sheet I
have set up, so they are in perfect alignment with each other. Theya re
then placedon a perfectly flat round shelf, which has been coated with
loose alumina, to allow for easy movement of the clay as it shrinks. The
clear space between shelves is 3 inches, and there is one plate per
shelf. They are glaze fired to Cone 5, computer controlled firing, and
allowed full cool down to room temp before opening the kiln. Two out of
three plates will have a warped rim. Not terribly so, but not as near
perfection as I would like. I don't feel I can get top dollar for them
with the rims as they are.
I know factory plates are pretty much ALL made from hydraulically
pressing fairly dry clay, and consequently the clay is far more dense
than clay in my plates thrown on a wheel. This will make a difference.
But is there anything else I can do to help prevent/reduce this warpage
- keep it from happening?
I'm using C5 Laguna B-mix.
Thanks,
Regards,
John Rodgers
Chelsea, AL
Overall's on fri 3 oct 08
John,
The easiest thing I could
recommend is to surround
the plate with kiln posts
laying down.=A0 Or cut up
soft firebrick in long narrow
rectangles about the height
of your plates/chargers.
Leave a slight gap in between
or drill holes in the IFB for
even heat distribution.
Not too close as their primary
purpose is to protect the
exposed rim from the pull
of the elements heat
which may be causing the
slight warpage.
Kim Overall
Texas Potters(c)2008
Texas Potters and Sculptors(c)
http://www.kimoverall.com
"In God We Trust"
Michael Wendt on fri 3 oct 08
John,
How do you prepare your clay?
Do you wedge or pug?
If you wedge, is it ram's horn or kneading?
I find that stack and slam wire wedging totally
eliminates uneven moisture in clay. I believe
uneven moisture is the cause of most warping
since moisture differentials shrink at different
rates both drying and later firing.
Additionally, saggaring can help solve warping
that is due to uneven temperature distribution.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave.
Lewiston, Id 83501
U.S.A.
208-746-3724
wendtpot@lewiston.com
http://www.wendtpottery.com
http://UniquePorcelainDesigns.com
John wrote:
I know factory plates are pretty much ALL made from
hydraulically
pressing fairly dry clay, and consequently the clay is
far more dense
than clay in my plates thrown on a wheel. This will
make a difference.
But is there anything else I can do to help
prevent/reduce this warpage
- keep it from happening?
I'm using C5 Laguna B-mix.
Thanks,
Regards,
John Rodgers
gayle bair on fri 3 oct 08
Hi Kim,
Achhh.... I did that with a plate.
It was the last piece to go into the kiln.
It was also 1 am.
The rim was too large and was touching the other kiln shelf.
In my 1am wisdom I decided to elevate the plate.
I placed the plate on 2 kiln posts (laying down) instead of 3. I think
there wasn't room for 3.
I spent several hours working on that plate which came out beautiful
except that it is warped!
Never underestimate B-Mix's sense of humor or my miss-estimation of my
cognitive skills at 1am.
BTW Your suggestion is a good one unless the plate is glazed on both
sides.
Best regards,
Gayle Bair
Bainbridge Island WA
Tucson AZ
gayle@claybair.com
www.claybair.com
On Oct 3, 2008, at 7:42 AM, Overall's wrote:
> John,
>
> The easiest thing I could
> recommend is to surround
> the plate with kiln posts
> laying down. Or cut up
> soft firebrick in long narrow
> rectangles about the height
> of your plates/chargers.
> Leave a slight gap in between
> or drill holes in the IFB for
> even heat distribution.
snip>
Bonita Cohn on sat 4 oct 08
I took classes with Richard Shaw years ago. He fires porcelain. thin. the way he keeps his plates from warping is to create a rack for each plate.
a circular, 1-2" high wide-as-the-plate-cylinder that the plate sits upon.
Takes teamwork, tho.
First the rack is placed on the kiln shelf -- 2 people carry it when wet!!! 2 hands, one on each of the 4 directions....
Then place the plate on it.
then fire together in each firing. you would have to keep the underside where they touch free of glaze.
perfect porcelain neriage plates.
I wish I had bought one when they were $200 -- in the 70's!
like $2000 in today's money.
Now its 10 times or more than that, if even available...
The only thing more difficult than b-mix is porcelain.
Bonnie Staffel on sat 4 oct 08
Hi John,
Don't know if this would help, but perhaps you are either drying your =
rims
too fast with perhaps a direction of air flow that would quietly tend to =
dry
one part of the rim before the other. The other suggestions is if you =
are
firing too fast as well. Perhaps the heat is getting to the rims before =
the
center thus creating stress. I wax my rims with water wax as soon as my
plates are thrown. This allows the center to dry before the rim in my =
studio
conditions.
Have you placed a level instrument on your shelves as well to make sure =
that
they are not even slightly warped?=20
Try these suggestions unless you feel you are not having troubles for =
these
reasons.
Bonnie Staffel
http://webpages.charter.net/bstaffel/
http://vasefinder.com/bstaffelgallery1.html
DVD Throwing with Coils and Slabs
DVD Introduction to Wheel Work
Charter Member Potters Council
Ron Roy on sun 5 oct 08
Hi John,
Sounds like the clay is getting qiute soft - perhaps a more refractory clay
is the answer.
I have made lots of plates with extended rims - cone 10 porcelain -
engineered the rim so it fell to almost flat during firing.
Your problem seems different in that you are getting more fall on one side?
Is it the side closest to elements or burners? Hard to solve in a square
kiln - easier to do in a round kiln.
I'd mix in some more refractory clay for those big chargers. It would help
if you tested the B mix for absorbency - then as you add in other clay you
would know when to stop.
RR
>Hopefully one of our gurus can help me here,
>
>The rim warping has been one of the banes of my existence in pottery,
>and I have never been able to fully resolve the issue. I make a fairly
>large dinner plate/charger - 14 inch dia with a rim approx. 1-1/2 inch
>wide for decoration purposes. The rim is carefully angled up and
>material at the edge is approx 1/8th in when dry. It thickens quickly
>for strength and support from the edge inward towards where the foot
>ring is located. This adds extra strength for the cantilever effect of a
>rim sticking out in the air with no support.
>The charger/plate actually has two foot rings - one smaller on towards
>the center of the plate, and a larger one near the outer diameter.
>
>These plate foot rings are ground to perfection on a big sanding sheet I
>have set up, so they are in perfect alignment with each other. Theya re
>then placedon a perfectly flat round shelf, which has been coated with
>loose alumina, to allow for easy movement of the clay as it shrinks. The
>clear space between shelves is 3 inches, and there is one plate per
>shelf. They are glaze fired to Cone 5, computer controlled firing, and
>allowed full cool down to room temp before opening the kiln. Two out of
>three plates will have a warped rim. Not terribly so, but not as near
>perfection as I would like. I don't feel I can get top dollar for them
>with the rims as they are.
>
>I know factory plates are pretty much ALL made from hydraulically
>pressing fairly dry clay, and consequently the clay is far more dense
>than clay in my plates thrown on a wheel. This will make a difference.
>But is there anything else I can do to help prevent/reduce this warpage
>- keep it from happening?
>
>I'm using C5 Laguna B-mix.
>
>Thanks,
>
>Regards,
>
>John Rodgers
>Chelsea, AL
Ron Roy
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Lee Love on sun 5 oct 08
If you are sanding the foot to level them, you might have different
compression in the different sections of the foot. You CAN compress
clay in the green state. One of my jobs as an apprentice, was to
inspect all the assembled work. If we saw any cracks in the joints,
we compressed them with a Popsicle or bamboo stick. We did a second
check after the bisque, and burnished any cracks that appeared then.
This eliminated all cracks in mug handles or teapot parts.
Also, if you have warpage in the drying, but move the pot back to
symmetry, the clay will often seek the pre-adjusted state. Clay has
memory.
It also seems to be a problem with high shrinkage cone six bodies.
--
Lee Love in Minneapolis
http://heartclay.blogspot.com/
http://mashikopots.blogspot.com/
http://claycraft.blogspot.com/
"Let the beauty we love be what we do.
There are hundreds of ways to kneel and kiss the ground." --Rumi
Victoria E. Hamilton on sun 5 oct 08
Bonnie -
Do you wax both the tops and bottoms of your rims?
Thanks.
Vicki Hamilton
Millennia Antica Pottery
Seattle, WA
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Bonnie Staffel
Sent: Saturday, October 04, 2008 6:38 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Quest: How to avoid warped plate rims
Hi John,
Don't know if this would help, but perhaps you are either drying your rims
too fast with perhaps a direction of air flow that would quietly tend to dry
one part of the rim before the other. The other suggestions is if you are
firing too fast as well. Perhaps the heat is getting to the rims before the
center thus creating stress. I wax my rims with water wax as soon as my
plates are thrown. This allows the center to dry before the rim in my studio
conditions.
Have you placed a level instrument on your shelves as well to make sure that
they are not even slightly warped?
Try these suggestions unless you feel you are not having troubles for these
reasons.
Bonnie Staffel
http://webpages.charter.net/bstaffel/
http://vasefinder.com/bstaffelgallery1.html
DVD Throwing with Coils and Slabs
DVD Introduction to Wheel Work
Charter Member Potters Council
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