Dai Scott on sun 9 feb 03
Someone 'way back suggested putting a piece of paper over the rime of a bowl
before removing it from the wheel, and I find that works really well. The
paper (I just use a piece of newspaper larger than the bowl---doesn't have
to be a circle of paper) clings to the damp rim, making a seal; V-shaped
bowls are particularly easy to remove from the wheel using the four-finger
method, and when you lift it to your ware board, the paper keeps the rim
from flexing. After removing the paper (I usually wait a while, while I'm
throwing other pots), a quick, gentle sponging gets rid of any "scuffing"
caused by removing the paper.
Dai in Armstrong, BC
Peter Jorna on sun 9 feb 03
Is there any method i am missing to prevent the warping of large 16+ =
inches diameter ,6-8" high V-shaped bowls from warping in the glaze =
firing, been throwing for about 7 years, but this seems to be allusive, =
i cool slowly, try to sagger them with mugs , bisque 'em high only going =
to ^6/7 in the glaze
they go in round and come out oval, tried different glazes, maybe it's =
my clay? considering giving up on throwing this form
but not yet.... maybe the next one.....
debbie in nova scotia
=20
Lily Krakowski on sun 9 feb 03
Warpage of course can depend on the clay. You knew that. So you HAVE
gotten in as many bodies as you can and tried your bowls with those clays?
Good. I know you did....Just checking...
Ok. Now. Hold up your hands palm to palm. Heels of hands touching. Lean
your palms and fingers outward to imitate your bowls. Ok? Look at your
hands. Do you see how gradually it all thins out? From the thick solid
part of your wrists through the heel of your hand, gradually into your palm
and then an even thinner profile to your finger tips?
Where a lot--don't know about your case-- of bowl warpage begins is in the
heel of the hand part. It gets thrown too thin, it is overtrimmed, the foot
is too small if there is a footrim. Focus on making the thinning into the
sides of the bowls GRADUAL, smooth, leaving a lot of support. (If pots
could sue, a lot of warped ones would be suing for "non-support". )
I was fortunate enough to take a class with Norah Braden years and years
ago. She emphasized that a pot should grow like a tree--from thick solid
roots up to delicate branches. And she imitated this, stretching her arms
up. As she was a short stocky woman this had a very dear quality to it. It
made one think of a solid British oak...
Peter Jorna writes:
> Is there any method i am missing to prevent the warping of large 16+ inches diameter ,6-8" high V-shaped bowls from warping in the glaze firing, been throwing for about 7 years, but this seems to be allusive, i cool slowly, try to sagger them with mugs , bisque 'em high only going to ^6/7 in the glaze
> they go in round and come out oval, tried different glazes, maybe it's my clay? considering giving up on throwing this form
> but not yet.... maybe the next one.....
>
> debbie in nova scotia
>
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
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Lili Krakowski
P.O. Box #1
Constableville, N.Y.
(315) 942-5916/ 397-2389
Be of good courage....
Bryan on sun 9 feb 03
----- Original Message -----
From: "Lily Krakowski"
> Where a lot--don't know about your case-- of bowl warpage begins is in
the
> heel of the hand part. It gets thrown too thin, it is overtrimmed,
the foot
> is too small if there is a footrim. Focus on making the thinning into
the
> sides of the bowls GRADUAL, smooth, leaving a lot of support. (If
pots
> could sue, a lot of warped ones would be suing for "non-support". )
>
Trimming can cause the lower walls to be uneven in thickness, especially
if the rim is not parallel to the foot, or the bowl is not centered for
trimming in the area where most of the clay is removed.
And some times they just warp, or so it seems.
Bryan Johnson
claybair on sun 9 feb 03
Hi Debbie,
I had the same experience with smaller bowls.
I traced it back to how I was removing them
from the bat after throwing them. I did this by watching
my process carefully. I was looking for any time
the bowl was oval.
After running a wire under them
I slid them off the bat onto a board.
Sometimes the bowl would warp slightly.
I would tap the board or use my fingers to get it
back to round.... BUT the clay remembered
my insensitive treatment and rewarded me with
oval bowls.
Various ways I have dealt with it:
Carefully run my wire under the bowl.
Let the bowl set up a while before removing it
from the bat.
Wet the board so the bottom doesn't catch when
sliding onto it.
I hope this helps.
Gayle Bair
Bainbridge Island, WA
http://claybair.com
-----Original Message-----
From: Debbie
Is there any method i am missing to prevent the warping of large 16+ inches
diameter ,6-8" high V-shaped bowls from warping in the glaze firing, been
throwing for about 7 years, but this seems to be allusive, i cool slowly,
try to sagger them with mugs , bisque 'em high only going to ^6/7 in the
glaze
they go in round and come out oval, tried different glazes, maybe it's my
clay? considering giving up on throwing this form
but not yet.... maybe the next one.....
debbie in nova scotia
Mary O'Connell on sun 9 feb 03
The v-shaped bowl is tricky to throw. Before I flair the walls out I =
usually will wait until I have the walls thinned as much as I want =
taking into account how much I want to flair the bowl as the walls will =
automatically thin at this point because the clay has to cover more =
surface area. At the end flair the walls with a rib/no water when no =
more thinning is necessary. All material has memory including clay, =
compression is a good idea. You might check your wall thickness and =
make sure you are not going too thin. Sometimes my students don't =
realize that there is thin and then there is too thin for certain shapes =
and effects. Good luck with this form it can be beautiful.
Regards,
Mary O'Connell
Marry Lukeman on sun 9 feb 03
Another solution
Take advantage of the warp and extend it to make a new form.
Lukeman Studios
London Ont Canada
>
> From: claybair
> Date: Sun, 9 Feb 2003 10:13:50 -0800
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Re: V-shaped bowls
>
> Hi Debbie,
>
> I had the same experience with smaller bowls.
> I traced it back to how I was removing them
> from the bat after throwing them. I did this by watching
> my process carefully. I was looking for any time
> the bowl was oval.
> After running a wire under them
> I slid them off the bat onto a board.
> Sometimes the bowl would warp slightly.
> I would tap the board or use my fingers to get it
> back to round.... BUT the clay remembered
> my insensitive treatment and rewarded me with
> oval bowls.
> Various ways I have dealt with it:
> Carefully run my wire under the bowl.
> Let the bowl set up a while before removing it
> from the bat.
> Wet the board so the bottom doesn't catch when
> sliding onto it.
>
> I hope this helps.
>
> Gayle Bair
> Bainbridge Island, WA
> http://claybair.com
>
> -----Original Message-----
> From: Debbie
>
> Is there any method i am missing to prevent the warping of large 16+ inches
> diameter ,6-8" high V-shaped bowls from warping in the glaze firing, been
> throwing for about 7 years, but this seems to be allusive, i cool slowly,
> try to sagger them with mugs , bisque 'em high only going to ^6/7 in the
> glaze
> they go in round and come out oval, tried different glazes, maybe it's my
> clay? considering giving up on throwing this form
> but not yet.... maybe the next one.....
>
> debbie in nova scotia
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
Vicki Hardin on sun 9 feb 03
One thing that we have done is to cover the bowl with a thin piece of plastic
from the dry cleaners and make a "seal". This creates and air bubble and
prevents warping. Or atleast in my opinion it does. Sometimes warping can
come from how the bowl is cut from the bat. I cut the bowl from the bat
while it is turning just slightly. This seems to be better than doing it
while it is stationary.
Best Wishes
Vicki Hardin
http://vickihardin.com
http://ClayArtWebGuide.com
iandol on mon 10 feb 03
Dear Lily Krakowski,=20
I think many of us know the principle you are describing and it is a =
good method of preventing slumping because you minimise the mass above =
the point of weakness.
But that hardly explains what was causing these bowls to go oval.
Best regards,
Ivor Lewis
Russel Fouts on mon 10 feb 03
Vicki,
>> One thing that we have done is to cover the bowl with a thin piece of plastic from the dry cleaners and make a "seal". This creates and air bubble and prevents warping. Or atleast in my opinion it does. <<
Newspaper works as well for this. Lay the newspaper over the open end
then wet your finger and run it around the rim over the paper, makes a
good seal.
In school, we almost never used bats, even for largish open forms. This
method lets you lift them right off the wheelhead.
This also makes for a lot of excitement when the paper "pops" and the
bowl folds and slips between your hands splatting onto the kick surface
of your wheel and you have to clean it up. ;-) But that doesn't happen
too often, at least not to "real" potters. ;-)
Ru
--
Russel Fouts
Mes Potes & Mes Pots
Brussels, Belgium
Tel: +32 2 223 02 75
Mobile: +32 476 55 38 75
Http://www.mypots.com
Home of "The Potters Portal"
Over 1800 Pottery Links!
Updated frequently
"Is the Hokey Pokey really what it's all about?"
deborah jorna on tue 11 feb 03
yes, thankyou ivor, came accross the uneven drying early on and remedied =
that, i don't find the idea of a thick base as aesthethically pleasing =
as a bowl with even thickness throughout, but if it means stopping the =
warping...it may be in my processing , i don't trim these large bowls =
after they are thrown, they are thrown 'dry', finished at the same =
timeand then left on the bat to set up.perhaps i can keep bowl of even =
thickness-about 3 nickles -from warping ,with more grog in my clay,
thank you again for the help
debbie jorna
who will soon have to start filling her wholesale orders(ugh!) instead =
of playing in the clay=20
----- Original Message -----=20
From: iandol=20
To: jorna@NS.SYMPATICO.CA=20
Cc: Clayart@LSV.CERAMICS.ORG=20
Sent: Monday, February 10, 2003 1:13 AM
Subject: : V-shaped bowls
Given that the thickness of the clay is constant across the diameter =
then this may be a drying problem. One side drying faster than the other =
will set up stress in the clay and this stress will resolve itself as =
motion when the clay becomes pyroplastic.
You might think about your processing with this idea in mind.
Best regards,
Ivor Lewis
iandol on thu 13 feb 03
Dear Lili,
I can hear you loud and clear.
The Bowl is a difficult structure to comprehend because it is the
antithesis of its reflection, the Dome. And we potters rarely think to
throw a Dome. Some do, but there are emotional difficulties for
novices in coping with the idea of throwing upside down.
I still think M. Cardew gives us the clearest insights into Bowl
Making using conventional throwing techniques. His method is fast and
the clay never has a chance to tire.
Good to hear from you.
Best regards,
Ivor Lewis
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