Alyssa Ettinger on sat 29 apr 06
i'm having a hard time with a set of plates i'm designing. cone 6 porcelain,
been trying to do once-fire (which i'm not married to)...
making hand-made plates that started as rolled slabs with
decorations/indentations made on/in them, then laid out into a plaster mold
the shape of a plate and pressing into plate with my hands.
there's a lot of warpage in drying, but i'm getting better at getting them
out of the mold in time to let them dry more evening. it's the rims...
they're sumping down, collapsing. some have turned my name plates into
complete pancakes.
is the rim too wide in comparison to the center? or something else all-together?
alyssa
in williamsburg brooklyn, land of the stray tabby cat
www.alyssaettinger.com
Barbara Lewis on sun 30 apr 06
Alyssa: I think the problem is that you need to build memory into the clay.
Try laying the slab on the plaster form, compressing the piece into the form
with a rubber rib, and THEN putting your design on the piece. Just as idea.
Barbara
----- Original Message -----
From: "Alyssa Ettinger"
To:
Sent: Saturday, April 29, 2006 11:29 PM
Subject: slumping/collapsing rims on plates
> i'm having a hard time with a set of plates i'm designing. cone 6
> porcelain,
> been trying to do once-fire (which i'm not married to)...
>
> making hand-made plates that started as rolled slabs with
> decorations/indentations made on/in them, then laid out into a plaster
> mold
> the shape of a plate and pressing into plate with my hands.
>
> there's a lot of warpage in drying, but i'm getting better at getting them
> out of the mold in time to let them dry more evening. it's the rims...
> they're sumping down, collapsing. some have turned my name plates into
> complete pancakes.
>
> is the rim too wide in comparison to the center? or something else
> all-together?
>
> alyssa
> in williamsburg brooklyn, land of the stray tabby cat
>
>
> www.alyssaettinger.com
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
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>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
William & Susan Schran User on sun 30 apr 06
On 4/29/06 11:29 PM, "Alyssa Ettinger" wrote:
> it's the rims...
> they're sumping down, collapsing. some have turned my name plates into
> complete pancakes.
>
> is the rim too wide in comparison to the center? or something else
> all-together?
I would think any clay, when taken to a temperature of vitrification,
becomes proto-plastic, and if thin and a sufficient mass is horizontal or
only slightly angled (your rims), it would collapse under it's own weight.
The remedy would be support under the rim or a rim that is not so wide, if
you continue to use the same clay and firing temperature.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
Michael Wendt on sun 30 apr 06
Alyssa,
In the March-April issue of Pottery Making Illustrated
is an article about the stack and slam wire wedging
method. This method can be used to great benefit
with tile and slab made items because it structures
the clay to be uniform in moisture.
If otherwise not distorted by uneven drying, clay
items made this way do not warp because they are
utterly uniform in moisture.
One added advantage to this method is you can raise
the firing temperature of a clay body by adding by
weight a certain percentage of a higher firing clay
body in the
classic line blend technique and eliminate the slumping
if it is due to pyroplastic behavior.
Two funny notes:
The editors inadvertently added 1973 to my email
address
at the end of the article. It should read:
wendtpot@lewiston.com
and they saved space in the construction directions for
the wedging table by telling people to "weld" the frame
to the table. I've tried this myself a number of times
but the wooden tables always catch fire, so I recommend
that you bolt the frame to the table for better results
;-)
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
Alyssa wrote:
i'm having a hard time with a set of plates i'm
designing. cone 6 porcelain,
been trying to do once-fire (which i'm not married
to)...
making hand-made plates that started as rolled slabs
with
decorations/indentations made on/in them, then laid out
into a plaster mold
the shape of a plate and pressing into plate with my
hands.
there's a lot of warpage in drying, but i'm getting
better at getting them
out of the mold in time to let them dry more evening.
it's the rims...
they're slumping down, collapsing. some have turned my
name plates into
complete pancakes.
is the rim too wide in comparison to the center? or
something else all-together?
alyssa
Alyssa Ettinger on sun 30 apr 06
first, please excuse my typos in the first post; it was the middle of the
night.
the idea of putting the design in after the clay is places in the mold is a
great one, but the designs are rolled into the slabs with a rolling pin.
the idea that they're slumping because of their own weight seems pretty dead
on, and i'm wondering what would happen if i change the size of the rims.
make them far narrower.
Susan Nebeker on mon 1 may 06
Alyssa,
I had the very same experience while making a set of plates for my 1st daughter's wedding gift. These slab built plates were allowed to do most of their drying still in their molds, so there was no question of them being handled too soon.
The wide rims all collapsed in the glaze fire and were flat as pancakes. Arghh!
Our next daughter's wedding plates were also slab built, this time with small rims.
They were perfect, no problem. I'll never use those wide rimmed mold forms again.
BTW, I took a chisel and a mallet and split all those collapsed rimmed plates and they work very nicely in the border of a small flower bed. Very cool save.....
HTH,
Susan Nebeker
Pollywog Pottery
Canby, Oregon
Alyssa Ettinger wrote:
first, please excuse my typos in the first post; it was the middle of the
night.
the idea of putting the design in after the clay is places in the mold is a
great one, but the designs are rolled into the slabs with a rolling pin.
the idea that they're slumping because of their own weight seems pretty dead
on, and i'm wondering what would happen if i change the size of the rims.
make them far narrower.
______________________________________________________________________________
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.
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