Undetermined origin c/o LISTSERV administrator on tue 1 mar 05
About June of last year I made up about 20 kg of porcelain
from a recipe attributed to Tom Turner. I added the dry
ingredients to a large excess of water, mixed well and let
stand for several days. Then I removed the clear water
from the top and poured the slurry into the leg of an old
pair of jeans and hung up outside in the shade to drip-dry.
After about a week the jean material was damp but not
soggy and the clay felt fairly stiff. I inverted the jeans and
peeled the leg off and had a log of porcelain which did
not slump on its own, at all. I picked up the log and
plopped it into a 5 gal bucket which caused the bottom to
spread out some, but did not cover the bottom of the bucket.
I put an air-tight lid on the bucket and forgot about it (heated
studio).
A couple of days ago I removed the lid and the surface felt
a little soft for throwing, but not by too much. I removed the
log to the workbench and sliced it in half with a wire. To my
surprise the core of the log was very, very soft. Not quite a
pour-able slip, but almost. I would have thought that after 7
or 8 months storage in a sealed environment the moisture
would have equalized throughout the mass of clay.
So, my questions are:
1. Is this an anomaly or is this what you have experienced?
2. Does this influence your thoughts on putting pots with handles
in a damp box for a while to let the moisture equilibrate?
In other words, I'm confused.
Earl K...
Bothell, WA, USA
"You may be disappointed if you fail,
but are doomed if you don't try"
Beverly Sills (1929- )
Ron Roy on wed 2 mar 05
Hi Earl,
I'm guessing but I think the log was like that when you took it out of the
sock - sides stiff enough to support but still soft in the middle.
It's one of the pains about porcelain - it does not want to even out like
most stoneware clay.
RR
>So, my questions are:
>1. Is this an anomaly or is this what you have experienced?
>2. Does this influence your thoughts on putting pots with handles
> in a damp box for a while to let the moisture equilibrate?
>
>In other words, I'm confused.
>
>Earl K...
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Daniel Semler on wed 2 mar 05
Hi Earl,
I thought I'd toss in something I noted in my recent (and as yet incomplete)
claybody trials.
I mixed up two bodies, of custer (50), epk (25) and silica (25). I added 2%
macaloid to one (PCB #2). Should throw like a dog I would think, but we'll see.
Both were wet mixed following David Beumee's article, except thatI dried them
hung in canvas. Anyhow PCB #1 (without macaloid) dried to a plastic mass fairly
quickly and not too unevenly. PCB #2 took about another week. Every couple of
days I would take PCB #2 out and look at it and it would feel nice and plastic
on the outside, but wedge it and its soft and squishy on the inside, just like
you describe. I put it back and repeated. It then came around.
I believe something like this may have happened with yours. As you also put
your clay in a sealed bucket I suspect there was little drying of the outside
of the log to encourage migration of water from the centre.
I suspect that this method is inferior to drying in racks (plaster, mesh and
screen, wahtever) in thinnish layers, as the thickness of the clay mass results
in a reasonably large moisture gradient from outside to centre.
Robert Tichane's Claybodies (I think this is the correct reference) talks
about a perhaps related issue in connection with filter presses. It seems that
as pressure is applied the clay platelets line up nice and flat against the
canvas in layers. They then become the filter for the clay/water mass behind
them. It doesn't take much for them to become pretty impervious to water. In
our cases there was no real pressure so I doubt the significance of the
particle orientation, but....... But this explains the desire for a relatively
thin filter cake. I have thought about desiging a thinner flatter canvas bag in
which to dry future bodies but have not yet produced one.
Don't know if any of this is of help ....
Thanx
D
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Steve Mills on thu 3 mar 05
Dear Earl,
The technique you used is the way I make/recycle the clay I use which is
a fine white stoneware.
After I remove it from the *Trouser Leg* I always have to part wedge it
otherwise it stays as you have found; soft in the middle and firm on the
outside.
Porcelain is in my experience even finer and denser than my mix, so your
experience does not surprise me at all.
Steve Mills
Bath
UK
In message , Undetermined origin c/o LISTSERV administrator LISTSERV@LSV.CERAMICS.ORG> writes
>About June of last year I made up about 20 kg of porcelain
>=66rom a recipe attributed to Tom Turner. I added the dry
>ingredients to a large excess of water, mixed well and let
>stand for several days. Then I removed the clear water
>=66rom the top and poured the slurry into the leg of an old
>pair of jeans and hung up outside in the shade to drip-dry.
>
>After about a week the jean material was damp but not
>soggy and the clay felt fairly stiff. I inverted the jeans and
>peeled the leg off and had a log of porcelain which did
>not slump on its own, at all. I picked up the log and
>plopped it into a 5 gal bucket which caused the bottom to
>spread out some, but did not cover the bottom of the bucket.
>I put an air-tight lid on the bucket and forgot about it (heated
>studio).
>
>A couple of days ago I removed the lid and the surface felt
>a little soft for throwing, but not by too much. I removed the
>log to the workbench and sliced it in half with a wire. To my
>surprise the core of the log was very, very soft. Not quite a
>pour-able slip, but almost. I would have thought that after 7
>or 8 months storage in a sealed environment the moisture
>would have equalized throughout the mass of clay.
>
>So, my questions are:
>1. Is this an anomaly or is this what you have experienced?
>2. Does this influence your thoughts on putting pots with handles
> in a damp box for a while to let the moisture equilibrate?
>
>In other words, I'm confused.
>
>Earl K...
>Bothell, WA, USA
>"You may be disappointed if you fail,
>but are doomed if you don't try"
> Beverly Sills (1929- )
--
Steve Mills
Bath
UK
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