Anthony G Allison on sat 17 jan 98
Hello Everyone,
I would like to hear how others deal with the problem of the lip of a
platter cupping upward as it dries. I've been working on solving this for
some time and it would be neat to hear how others handle it. Thanks,
Tony Allison
Craig Martell on sun 18 jan 98
At 09:51 AM 1/17/98 EST, Tony wrote:
>----------------------------Original message----------------------------
>I would like to hear how others deal with the problem of the lip of a
>platter cupping upward as it dries. I've been working on solving this for
>some time and it would be neat to hear how others handle it.
Hi:
I think that there are several things that can be done to lessen this
problem, but I don't think it can be eliminated entirely.
One thing that helps a lot is throwing the lips out horizontally instead of
throwing them upwards and then settling them down with your hands, or a rib.
I usually throw the rims out at a 30-35 degree angle and then drop them some
more with a rib. I usually push them down a bit more than I want in the
finished piece because they are going to rise come hell or high water. The
wider the rim, the more it will rise.
Throw the rims a bit thicker than you want them to be and turn away the
excess later. This keeps the rims from drying too quick, which will bring
them up. I also cover the rims and let the pieces dry from the bottom as
much as possible. You can also put the platter back on the wheel when just
past cheese hard and settle the rim down again if it has come up too much.
I don't like to do this if I can aviod it, but it works, and sometimes it's
necessary.
Some people throw platters on large plaster bats which helps them dry more
evenly and helps keep the rims down.
Tom Coleman uses a technique of compressing the very edge of the rim. You
place one hand underneath to support the rim and press down on the upper
side a bit and make a small concave depression. This extends in no more than
one quarter inch or so. I've tried this and it works, but does not totally
eliminate the problem.
regards, Craig Martell-Oregon
Grimmer on sun 18 jan 98
Tony,
I find that I usually have to put my platters back on the wheel and
push the rim back down with a wet sponge. Be sure that you don't
attempt this after the clay is too stiff! Another thing that helps is
using plaster bats for platters so the bottom dries with the rim.
Also, leave the platter upside down to dry after trimming.
Hope this helps
steve grimmer
marion illinois
Anthony G Allison wrote:
>
> ----------------------------Original message----------------------------
> Hello Everyone,
>
> I would like to hear how others deal with the problem of the lip of a
> platter cupping upward as it dries. I've been working on solving this for
> some time and it would be neat to hear how others handle it. Thanks,
>
> Tony Allison
Paul Jay on sun 18 jan 98
TONY
I try to dry mine upside down untill almost dry, or dry right side up with a
thin peice of plasterboard on top that completyl covers the platter.
Anthony G Allison wrote:
> ----------------------------Original message----------------------------
> Hello Everyone,
>
> I would like to hear how others deal with the problem of the lip of a
> platter cupping upward as it dries. I've been working on solving this for
> some time and it would be neat to hear how others handle it. Thanks,
>
> Tony Allison
Jim and Judith Enright on sun 18 jan 98
Hi, Tony -- I always flip the platter over as soon as the clay stiffens up
enough, and let it dry bottom-side up. I do this with most of my work,
aamof.
-- Judith Enright @ Black Leopard Clayware
shelford on mon 19 jan 98
Hi Tony -
The only reliable way I've managed is to throw the lip or rim as near
horizontal as possible, throwing dry enough that it doesn't flop. It will
cup a bit, but only enough to be attractive. If you wanted REALLY flat you
might as well make a slab piece. Or, of course, keep more clay underneath
and trim it afterwards, but that isn't as time- or clay-efficient, and it
usually lacks the grace of a rim that's thrown outward.
I was struggling to get the rim as near flat as possible for a dinner set
once, and the customer came in and announced that the ones she really liked
were the ones that cupped. So I worry less.
I'll be interested in seeing other's experience.
- Veronica
>----------------------------Original message----------------------------
>Hello Everyone,
>
>I would like to hear how others deal with the problem of the lip of a
>platter cupping upward as it dries. I've been working on solving this for
>some time and it would be neat to hear how others handle it. Thanks,
>
>Tony Allison
>
>
___________________________________________
Veronica Shelford
e-mail: shelford@island.net
s-mail: P.O. Box 6-15
Thetis Island, BC V0R 2Y0
Tel: (250) 246-1509
Anthony G Allison on mon 19 jan 98
Yep, I tried the cover idea also. This seems to work the best on smaller
plates-(under 12" in dia) especially when you stack about 5-6.
Tony
At 11:20 AM 1/18/98 EST, you wrote:
>----------------------------Original message----------------------------
>TONY
>I try to dry mine upside down untill almost dry, or dry right side up with a
>thin peice of plasterboard on top that completyl covers the platter.
>
>Anthony G Allison wrote:
>
>> ----------------------------Original message----------------------------
>> Hello Everyone,
>>
>> I would like to hear how others deal with the problem of the lip of a
>> platter cupping upward as it dries. I've been working on solving this for
>> some time and it would be neat to hear how others handle it. Thanks,
>>
>> Tony Allison
>
John Hesselberth on mon 19 jan 98
>----------------------------Original message----------------------------
>At 09:51 AM 1/17/98 EST, Tony wrote:
>>----------------------------Original message----------------------------
>>I would like to hear how others deal with the problem of the lip of a
>>platter cupping upward as it dries. I've been working on solving this for
>>some time and it would be neat to hear how others handle it.
>
The basic problem with lips of plates cupping up is development of
non-uniform stress from one of several sources. The most likely are 1)
non uniform drying (the clay on the top surface is drying more rapidly
and therefore shrinking while the clay on the bottom surface is still wet
enough to stretch or 2) you are introducing stress by lifting the plate
by its rim when it is too soft. Clay has a memory and can remember that
upward force as it continues drying. A couple of the first responders
suggested how to get more uniform drying. The additive point I would
make is don't ever get a plate of a batt by lifting the rim. Run your
wire between the plate and the batt, put another bat on top of it and
gently flip it over. Then, slowly and uniformly around the
circumference, work the original batt loose.
This subject is part of the broader subject of cracking and warping. I
recently wrote, and Clay Times published, a 2 part article on the
subject. See Clay Times Nov/Dec '97 and Jan/Feb '98 issues or visit my
web site (www.frogpondpottery.com) for a more complete discussion of the
subject and some further references.
John Hesselberth
Frog Pond Pottery
Pocopson, PA USA
EMail: john@frogpondpottery.com
visit my web site at http://www.frogpondpottery.com
Mike Wright on mon 19 jan 98
At 09:51 AM 1/17/98 EST, you wrote:
>----------------------------Original message----------------------------
>Hello Everyone,
>
>I would like to hear how others deal with the problem of the lip of a
>platter cupping upward as it dries. I've been working on solving this for
>some time and it would be neat to hear how others handle it. Thanks,
This probably depends upon the clay you're using, humidity levels, etc.,
etc. But anyway, I let them dry quite slowly, usually under wraps (loose
ones), sometimes shut in a somewhat airless cabinet for a couple of days.
(This is all post-trimming).
Mike Wright
Poverty Ridge Pottery
Ackworth, Iowa
Rick Sherman on mon 19 jan 98
>----------------------------Original message--------------------------
>I would like to hear how others deal with the problem of the lip of a
>platter cupping upward as it dries. I've been working on solving this for some
--------------------------------reply--------------------------------
You have already received some good suggestions. I find a lot depends
on the clay. Rims don't cup up as much with a heavily grogged clay.
With the clay I use, a fine white body, it is necessary to push the
rims down to the horizontal during the drying process. Turning a large
platter over during drying causes the rim to crack. Another trick is to
put a 3/4" to 1" thin bat on top of the rim during drying.
I also find rims turn up less if platters are allowed to dry slowly
under a plastic dropcloth.
Rather than use plaster bats which are heavy and take up a lot of
space, I lift platters off the throwing bat ASAP and put them on 3 or 4
wood lath strips so they dry evenly.
With my old stoneware clay, rims that cupped up in drying did drop back
somewhat when fired to ^11.
RS
San Jose, CA
Vince Pitelka on tue 20 jan 98
>This probably depends upon the clay you're using, humidity levels, etc.,
>etc. But anyway, I let them dry quite slowly, usually under wraps (loose
>ones), sometimes shut in a somewhat airless cabinet for a couple of days.
>(This is all post-trimming).
This has been discussed recently, but is worth mentioning again. Slow
drying after trimming is of course important. But the most important stage
in preventing the problem of platter rims "cupping" upwards is BEFORE
triming. Assuming that the plate or platter has been thrown with a thick
bottom to allow trimming, if it is allowed to stiffen to trimming stage in
the open air, water is evaporating from both sides of the thinner rim, and
only from the top of the thick bottom, thus the rim shrinks and warps
upwards. As someone already mentioned, the rim often settles back down in
high-firing, but I have found that this is occasionally accompanied by
cracking around the circumference where the base meets the upwards curve of
the rim. This can all be avoided by slow-drying after throwing before
trimming. When I throw a batch of platters put in a damp box, or I cover
them with a RAISED layer of plastic sheeting, so that air can circulate
around them within the enclosed atmosphere. A few days in either situation
and they are usually ready for trimming. It takes some space, but if you
make lots of platters it is worth it.
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Lili Krakowski on wed 21 jan 98
As I missed original query I am not quite sure what the problem is:
several possible solutions:
1. Put the pot back on the wheel when it has set up somewhat--with
your rib, push the rim down beyond the point you "dared" push it
originally.
2. Put the whole thing in a damp box improvised somehow, and use
newspaper under the pot. the idea here is to speed up the
drying/shrinkage
of the bottom (wicking effect) on the body of the pot, so the rim does not
dry faster, which is the cause of the problem
3. Use resist on the rim asap.
4. Read Cardew. My Pioneer Pottery is not on hand, but I do seem
to recall he discusses the problem of shrinkage (it is shrinkage in drying
which causes the "rising of the rim."
On Sat, 17 Jan 1998, Anthony G Allison wrote:
> ----------------------------Original message----------------------------
> Hello Everyone,
>
> I would like to hear how others deal with the problem of the lip of a
> platter cupping upward as it dries. I've been working on solving this for
> some time and it would be neat to hear how others handle it. Thanks,
>
> Tony Allison
>
Lili Krakowski
Jennifer Boyer on wed 21 jan 98
Hi Tony,
Get yourself a roll of plastic wrap and cut a length long enough to wrap
around the rim of the platter, leaving most of the middle exposed to the
air. I usually cover my rims when the platters have dried a little and the
rims aren't sticky. Covering the rim allows the middle to lose it's
moisture at more or less the same rate as the rim. I use this technique for
all my wide forms, as my studio is warm and everything dries very fast. The
wrap gets easier to handle after it has gotten a nice coating of clay dust.
This technique is a little bit of a pain, but I like it better then
flipping the platter over, as some have suggested. If you do this too
early, the middle sags, and if you do it too late the rim is brittle and
can't take the stress. My theory about why platter rims cup when the rim
dries first is that the bottom of the platter isn't shrinking with the
rim, so the rim is forced to curl inward. The bottom eventually catches up,
and pulls inwardas it shrinks, but the rim is already dry and can't settle
back down. Now that would be very Zen: sitting all day watching your
platter shrink....
Take Care
Jennifer
>----------------------------Original message----------------------------
>Hello Everyone,
>
>I would like to hear how others deal with the problem of the lip of a
>platter cupping upward as it dries. I've been working on solving this for
>some time and it would be neat to hear how others handle it. Thanks,
>
>Tony Allison
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jennifer Boyer
Thistle Hill Pottery
Montpelier, Vt. 05602
jboyer@plainfield.bypass.com
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