Eric B on sun 6 jul 03
does anyone know, either from experience or "study," for how long a time the
molecular-allignment in clay that wedging causes (making it seemingly softer
and easier to throw) lasts? for example, if i weigh and wedge up a palate of
5lb balls of stoneware clay body one day AND cover/seal it very well with
plastic (to impede evaporation from outer layers of the balls), how many hours/days
to i have before i'll have to re-wedge it before throwing? or do the clay
platelets remain "aligned" indefinitely?
i know there are other benefits of wedging too, e.g., moisture homogeneity ,
elimination of air pockets, etc., but for purposes of my question it is the
"molecular alignment of the clay platelet molecules" that i'm interested in.
thanks all.
eric
Spun Mud
Earl Brunner on mon 7 jul 03
Eric, I'm not sure that "alignment of particles" is a significant factor
to worry about. But it is easily tested. Wedge up a bunch of balls and
use them over several days to make similar pots. Compare the results.
But another question, if you are intending to align the particles with
your wedging for some benefit, do you keep track of the alignment of the
balls? In other words, "if" wedging aligns the particles in one
direction, do you keep that alignment when you place the ball on the
wheel?
Now that I've written all of that, in re-reading your message, I wonder
if you are not using the wrong terminology to describe what you are
talking about? It's true that clay at rest can be stiff until wedged
and that wedging seems to "soften up" the clay (I notice this
particularly with Coleman Porcelain) But I'm not sure that this
behavior has anything to do with alignment of particles from wedging. I
can get the same results from slamming the bag of clay on the floor a
couple of times. And as far as I know, slamming the bag on the floor
isn't the same as wedging or at least doesn't align the particles the
same way.
I think it might have more to do with the kinds of things we see going
on with thixotropic clay than particle alignment.
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Eric B
Sent: Sunday, July 06, 2003 4:28 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: longevity of wedging benefits
does anyone know, either from experience or "study," for how long a time
the
molecular-allignment in clay that wedging causes (making it seemingly
softer
and easier to throw) lasts? for example, if i weigh and wedge up a
palate of
5lb balls of stoneware clay body one day AND cover/seal it very well
with
plastic (to impede evaporation from outer layers of the balls), how many
hours/days
to i have before i'll have to re-wedge it before throwing? or do the
clay
platelets remain "aligned" indefinitely?
i know there are other benefits of wedging too, e.g., moisture
homogeneity ,
elimination of air pockets, etc., but for purposes of my question it is
the
"molecular alignment of the clay platelet molecules" that i'm interested
in.
thanks all.
eric
Spun Mud
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Dave Finkelnburg on mon 7 jul 03
Dear Eric,
You have asked a great question. I, too, have wondered how long the
benefits of wedging/kneading of clay last.
It is important first, though, to point out that the "molecular
alignment of the clay platelet molecules" is a pure myth, something that
never has happened and never will happen with clay. Clay particles are just
way, way too small for manual or mechanical manipulation of the clay to ever
get them lined up parallel to each other.
The benefits you observe from kneading clay are simply two. First, you
do make, as you mention, the moisture distribution even throughout. That's
key to preventing cracking in the thrown ware. Second, I believe, though I
cannot prove, that you overcome the tendency of the clay to be thixotropic
and "set" over time.
I live and work in a relatively dry climate. I worry most about the
weighed clay balls drying on the surface and use that as a gauge of how long
to leave them be.
Good potting!
Dave Finkelnburg in Idaho where we've just spent the evening having
a wonderful family dinner on the patio under the spruce tree that is, at the
moment, doubling as a bird high rise. The frequently patronized hummingbird
feeder hangs from a lower branch, beneath the nesting house finches who are
feeding young a scant story up and who are in turn beneath a Northern oriole
nest that's a few feet below the penthouse apartment occupied by a noisy
family of Western kingbirds, one of whom has fledged enough to hop onto
another limb and begs for food from its parents there...
----- Original Message -----
From: "Eric B"
> does anyone know, either from experience or "study," for how long a time
the
> molecular-allignment in clay that wedging causes (making it seemingly
softer
> and easier to throw) lasts? for example, if i weigh and wedge up a palate
of
> 5lb balls of stoneware clay body one day AND cover/seal it very well with
> plastic (to impede evaporation from outer layers of the balls), how many
hours/days
> to i have before i'll have to re-wedge it before throwing? or do the clay
> platelets remain "aligned" indefinitely?
>
> i know there are other benefits of wedging too, e.g., moisture homogeneity
,
> elimination of air pockets, etc., but for purposes of my question it is
the
> "molecular alignment of the clay platelet molecules" that i'm interested
in.
Earl Brunner on mon 7 jul 03
Dave, for the sake of argument, I'll accept that particle alignment
doesn't take place as is often described. However particle alignment as
it has been described I believe is an attempt to explain observed
behavior of clay. I know that I originally accepted this explanation
based in part on the chapters in Glen Nelson's book and Daniel Rhodes
books where they talked about the formation of clay and from their
descriptions of its characteristics (extremely small platelets). So if
what we are describing isn't particle alignment, what is it?
When clay is wedged using the spiral method, I typically end up with a
cone shaped piece of clay. If I let that cone dry until it is between
leather hard and dry, I can break it up and it will break along the
lines of the spiral wedge. If we are not talking about particle
alignment, then what explains the phenomenon? There is also the "twist"
that develops in a thrown cylinder; the phenomenon of teapot spouts that
"unwind" during firing and end up sideways. If I accept that it isn't
actually electron microscopic sized particles "aligning", then what
exactly is it?
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Dave
Finkelnburg
Sent: Monday, July 07, 2003 12:52 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: longevity of wedging benefits
Dear Eric,
You have asked a great question. I, too, have wondered how long the
benefits of wedging/kneading of clay last.
It is important first, though, to point out that the "molecular
alignment of the clay platelet molecules" is a pure myth, something that
never has happened and never will happen with clay. Clay particles are
just
way, way too small for manual or mechanical manipulation of the clay to
ever
get them lined up parallel to each other.
The benefits you observe from kneading clay are simply two. First,
you
do make, as you mention, the moisture distribution even throughout.
That's
key to preventing cracking in the thrown ware. Second, I believe,
though I
cannot prove, that you overcome the tendency of the clay to be
thixotropic
and "set" over time.
I live and work in a relatively dry climate. I worry most about the
weighed clay balls drying on the surface and use that as a gauge of how
long
to leave them be.
Good potting!
Eric B on mon 7 jul 03
i confess to not know much at all about the molecular alignment of clay, but
i am still convinced that "something" happens to the clay after wedging that
makes it seem softer and easier to throw. so . . . whatever that phenomenon is
(i'm sure that most throwers out there agree with me that it happens), does
anyone know how long it retains that beneficial property without being
re-wedged?
thanks for your responses.
eric
iandol on tue 8 jul 03
Dear Eric B,
Provide me with illustrations of aligned particles in plastic clay and I =
may be able to answer your question.
Logically, if it is a case that particles are aligned by the processes =
you use to wedge or knead your clay and you let it rest undisturbed then =
they will remain aligned for eons of time.
The big problem here is not that material clay moves but that water =
migrates from places of high concentration to places of low =
concentration. This changes the pace at which the plastic clay can move =
for a given application of force. You get a hard shell next to the =
porous covering due to diffusion and the interior remains soft. Before =
the clay can be used it has to be homogenised. This may be difficult if =
it has lost a lot of water. Then it needs reclaiming.
Best regards,
Ivor Lewis. Redhill, South Australia.
=20
pdp1@EARTHLINK.NET on tue 8 jul 03
----- Original Message -----
From: "Janet Kaiser"
> Sorry, I misread the subject line first glance, Eric:
thought it was the
> "longevity of wedding benefits"! I should get accustomed
to using my
> reading glasses and not just hang them round my neck each
day... :-)
Hi Janet,
I think the transposition is no mere accident of vision, but
rather that Weddings and Wedging do in fact bear some
curious resemblences or co-respondances to eachother.
Or will, if either last
long enough, or even if they don't, and so it behooves any
aspirant couple, or
Thrower as may be, who may
wish 'longevity' to their Wedding, or rather, their
Marriage, or their pliant responsive Clay, to understand the
benifits of happy
thixotropias and prothixotropomorphic attentions,
ministerings and their subsequent rewards.
Or that there may be many 'particles' as need to be aligned,
sometimes more than others, sometimes much 'more', and
'particles' as need to
have those influences brought to their medium in which they
are suspended, as let them do so, let them 'align', for
matters to be right with themselves, and eachother, for the
tasks of throwing or Marriage.
...either way,
...yes?
Yours,
Phil
lasvegas
Lee Love on tue 8 jul 03
----- Original Message -----
From: "Eric B"
> (i'm sure that most throwers out there agree with me that it happens), does
> anyone know how long it retains that beneficial property without being
> re-wedged?
If you've ever wedge clay, put it in a plastic bag and let it sit a day, it is
obvious that the uniformity of moisture in the clay is lost. If you unwrap the
clay the next day, there is moisture on the outside of the clay.
At the workshop where I studied, the shokunin (craftsmen) always only
wedged or de-air pugged the clay just before they used it.
Of course, clay might be "ruff wedged" ahead of time, but the final
wedging was always done just before use.
The head thrower often skipped wedging, except to shape a cone for hump
throwing, after the pug came out of the de-airing pug mill. But all us
deshis/apprentices were expected to wedge before we threw, as a part of our
"education."
--
Lee Love In Mashiko, Japan
"Concerning all acts of initiative (and creation),there is one elementary truth
the ignorance of which kills countless ideas and splendid plans: that the
moment one definitely commits oneself, then providence moves too. A whole stream
of events issues from the decision, raising in one's favor all manner of
unforeseen incidents, meetings and material assistance, which no man could have
dreamt would have come his way." --W.H. Murry
Janet Kaiser on tue 8 jul 03
Sorry, I misread the subject line first glance, Eric: thought it was the
"longevity of wedding benefits"! I should get accustomed to using my
reading glasses and not just hang them round my neck each day... :-)
It is my understanding (always dodgy) that the required *additional
softness* you refer to in newly-wedged clay which is pre-formed into balls
before throwing, has more to do with water distribution and thixotropy than
anything else. One theory does indeed associate thrixotrophy with the
lamellar alignment of clay platelets you describe, but it is not the only
theory which has been suggested nor is it accepted by everyone.
The even distribution water through kneading/wedging is the most important
aspect of the process, which also allows the potter to judge the state of
the clay, inc. plasticity etc. of each batch of clay immediately prior to
throwing. That was highly variable in the days when clay was prepared
on-site and not delivered in neat plastic bags, so it was useful to know
the "feel" before a throwing session commenced.
The phenomena is not of long duration, which is why wedging, weighing &
balling (is that a word?) is done immediately prior to throwing and not
days beforehand. The process has little to do with the softness of the clay
which is dependent on water content. If that were the case potters would
spend a day/week wedging, weighing, etc. and the next day/week throwing,
which is probably what you had in mind when you asked the question?
You can of course make all the balls and cover them with plastic or wet
newsprint until you need them. As long as they don't dry out too much, they
will still remain usable although a quick "wheel wedge" of each ball may
help. I mentioned your question to Russel before Avril picked him up this
morning... He said that someone mentioned a demo about wheel wedging with
two different coloured clays and a number of cross-sections to show the
effectiveness of coning up and down a couple of times before throwing.
Maybe when he is back in Brussels he will chip in here.
I know quite a few throwers who do that anyway, especially when starting
their day and getting the feel for the clay before starting a long session.
Although I have not answered your question, I hope it helps anyway!
Sincerely
Janet Kaiser - up before my breakfast this morning! Russel should be home
now... And I have almost finished the new exhibition. Got a party of 16 US
tourists calling in tomorrow, so see what they think of all the colour!
*** IN REPLY TO THE FOLLOWING MAIL:
>does anyone know, either from experience or "study," for how long a time
the
>molecular-allignment in clay that wedging causes (making it seemingly
softer
>and easier to throw) lasts?
*** THE MAIL FROM Eric B ENDS HERE ***
**********************************************************************
TRUTH is too precious to tell every fool who asks for it...
****** This post was sent to you today by Janet Kaiser *******
The Chapel of Art / Capel Celfyddyd
8 Marine Crescent, Criccieth LL52 0EA, Wales, UK
Tel: ++44 (01766) 523570 URL: http://www.the-coa.org.uk
**********************************************************************
Ron Roy on wed 9 jul 03
Hi Eric,
I usualy wedge just before throwing but - as Lee mentions - half wedge the
day before works well.
I have also seen bubbles on clay that has been wedged the day before. When
you wedge clay you entrain oxygen and that can wake up the bacteria and in
some cases enough gases are produced to be noticable.
RR
>does anyone know, either from experience or "study," for how long a time the
>molecular-allignment in clay that wedging causes (making it seemingly softer
>and easier to throw) lasts? for example, if i weigh and wedge up a palate of
>5lb balls of stoneware clay body one day AND cover/seal it very well with
>plastic (to impede evaporation from outer layers of the balls), how many
>hours/days
>to i have before i'll have to re-wedge it before throwing? or do the clay
>platelets remain "aligned" indefinitely?
>
>i know there are other benefits of wedging too, e.g., moisture homogeneity ,
>elimination of air pockets, etc., but for purposes of my question it is the
>"molecular alignment of the clay platelet molecules" that i'm interested in.
>
>thanks all.
>
>eric
>Spun Mud
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on wed 9 jul 03
Hi Dave,
I disagree - and I think it is demonstrate - particle arrangement is
possible and understanding as much as we can about it will help us solve
shrinkage and cracking problems.
There is quite a bit on the subject in Ceramic Science for the Potter by
Lawrence and West. It has been reprinted by Gentle Breeze publishing
(Axner.)
To give you some idea - these heading from the index.
Particle orientation:
Caused by extrusion
Caused by slip casting
Caused by throwing
Differential drying shrinkage caused by
Differential firing shrinkage caused by
Effect of.
Just what you need to know in a dry climate - and even in a wet one.
RR
> It is important first, though, to point out that the "molecular
>alignment of the clay platelet molecules" is a pure myth, something that
>never has happened and never will happen with clay. Clay particles are just
>way, way too small for manual or mechanical manipulation of the clay to ever
>get them lined up parallel to each other.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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