Lisa E on tue 28 aug 07
I am currently making square plates using a hump mold (cheap plastic plates
from the dollar store). It seems that the larger plates all warp. BUT they
do not warp when they are drying or even during the bisque firing but when
they are glaze fired.
Is it the glaze OR is there something else I can do to prevent warping? I
am drying my pieces long and even before the first firing. I am rolling the
pieces with my rolling pin in every direction and on both sizes. Should I
be wedging the clay more first? Any suggestions to prevent warping?
Regards,
--
Lisa Elbertsen
www.LisaElbertsen.com
Sunny Daze Design Pottery Studio
SunnyDazeDesign@gmail.com
Squamish, BC Canada
Michael Wendt on thu 30 aug 07
Lisa,
Try this experiment:
Do some of the plates the same way
as a control group and mark them
Do some with 10 wire wedged stack
and slam counts.
Do some with 20 stack and slam
counts and finally, some with 30
stack and slam counts.
Choose the method that gives the
lowest loss rate while still being
within the work level you are willing
to do.
The reason stack and slam works is it
makes the clay uniform in moisture
content and so homogeneous when
dry as well so that there is no hidden
variability in shrinkage later that can
result in the dreaded "clay memory"
people talk about. I personally do
not believe clay has this memory but
warps in response to density variations
that result in variable shrinkage in the
glaze fire.
Try it, you may like it.
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
Lisa wrote:
I am currently making square plates using a hump mold
(cheap plastic plates
from the dollar store). It seems that the larger
plates all warp. BUT they
do not warp when they are drying or even during the
bisque firing but when
they are glaze fired.
Is it the glaze OR is there something else I can do to
prevent warping? I
am drying my pieces long and even before the first
firing. I am rolling the
pieces with my rolling pin in every direction and on
both sizes. Should I
be wedging the clay more first? Any suggestions to
prevent warping?
Regards,
--
Lisa Elbertsen
www.LisaElbertsen.com
Sunny Daze Design Pottery Studio
Nancy on thu 30 aug 07
Lisa
I had the same problem with square plates. I now roll my clay on a
piece of roofing tar paper and muslin. I make sure I turn it at least 4
times...north south east west is how I think of it. I then never pick
the slab up off the paper and let it sit with a board on top of it for a
few hours to overnight. I just throw a garbage bag over the pile of 6-8
slabs.
Then after I've put my designs in, I pick the tar paper up and lay it
over the mold. I too use the plastic plates but I first put a saran
wrap on it (it shrinks as necessary as the piece drys). I throw a bag
over each plate and let it sit on my drying shelf for a few days. Then
I unmold it by placing a drying board on the bottom and flipping. pull
the plate off then the saran wrap and tweek the piece without picking it
up! ...this has eliminated most of my warping. I would send you a
picture but I just sold my last 2 square plates last weekend. I hope
this gives you some ideas to help with your warping.
Nancy
www.hilltoppottery.com
Lisa E wrote:
> I am currently making square plates using a hump mold (cheap plastic plates
> from the dollar store). It seems that the larger plates all warp. BUT they
> do not warp when they are drying or even during the bisque firing but when
> they are glaze fired.
>
> Is it the glaze OR is there something else I can do to prevent warping? I
> am drying my pieces long and even before the first firing. I am rolling the
> pieces with my rolling pin in every direction and on both sizes. Should I
> be wedging the clay more first? Any suggestions to prevent warping?
>
> Regards,
>
> --
> Lisa Elbertsen
> www.LisaElbertsen.com
> Sunny Daze Design Pottery Studio
> SunnyDazeDesign@gmail.com
> Squamish, BC Canada
>
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>
Patty Kaliher on fri 31 aug 07
I attended a porcelain workshop with Patty Wouters from Belgium. I have not
tried this. She throws her plates on the wheel to a finished thickness on
the bottom (no trimmed foot). She bisque fires them on their edges.
Leaned against a piece of furniture against the side of the kiln, three
deep. Says they do not warp or crack. Before firing the glazed plates she
puts a very thick coat of kiln wash on the kiln shelf and then cuts grooves
in the kiln wash so air gets under the plates and they heat and cool evenly.
To prevent S cracks she first wedges a cone up on the wheel, pushes it down
than cuts all the clay off the wheel and puts it back upside down and again
wedges a cone up and down before throwing the plate. She says that this
gets all particles correctly oriented. Normally the bit of clay on the
wheel in the very center is stressed because it does not get oriented in the
way the rest of the clay does during the throwing process.
Just thought I would pass these tips along.
Ron Roy on sat 1 sep 07
Hi Lisa,
When you make slabs the outsides are stretched and the insides are
compressed. If you can find a way to recompress the outside edges when
making the plates you may find it helpful.
RR
>I am currently making square plates using a hump mold (cheap plastic plates
>from the dollar store). It seems that the larger plates all warp. BUT they
>do not warp when they are drying or even during the bisque firing but when
>they are glaze fired.
>
>Is it the glaze OR is there something else I can do to prevent warping? I
>am drying my pieces long and even before the first firing. I am rolling the
>pieces with my rolling pin in every direction and on both sizes. Should I
>be wedging the clay more first? Any suggestions to prevent warping?
>
>Regards,
>
>--
>Lisa Elbertsen
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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