iandol on wed 12 apr 00
------------------
Wedging Tables and Clay Preparation.
I may be wrong but I get the feeling that there may be some confusion about =
the
processes of preparing clay so that it achieves its optimum plastic =
condition.
Is there some confusion about what may be meant by wedging, spiral wedging,
bullhead wedging, slam wedging and so on?
I always taught that there were two essential processes. The first, called
Wedging precedes the second, which is called Kneading.
Wedging infers that the clay is cut into two pieces which have the shape of
wedge of cheese. The upper one is lifted from the lower one, turned over =
then
slammed or slapped down hard on the wedge which remains on the bench. The =
block
of clay is then rotated about a quarter of a revolution, cut, separated, =
turned
over and slapped down again. This is repeated until the potter is satisfied =
that
there are no more air pockets, twine, sticks, pebbles, all of which are =
picked
out of the clay when they come to the surface.
Kneading follows. Be it bulls head, rams head, spiral or chrysanthemum, the
purpose is to make the now smooth clay uniform in colour, texture, =
plasticity.
Slam wedging used in some localities in Britain. I always called it =
Sunderland
method. Sunderland had a history of glass and clay going back almost fifteen
hundred years. The potter shapes the clay into a rectangular slab which is
brought down half way over the edge of the bench so that it shears into two
pieces. Air pockets rupture with explosive force. Rocks and coarse grog can =
fly
like bullets. The piece in your hands is then brought down with equal force =
onto
the partner on the bench. More explosive violence=21=21 It is the quickest =
and
easiest way if you have strong wrists. Slap and shear twenty times and there=
is
over a million layers formed from the original single piece. Twenty five
repetitions and you have thirty million layers. I think that the compression
waves help to shear cleavage planes in the kaolinite crystals. Complete the
activity with your favourite way of kneading. Perfect clay. I=92m willing to
travel to give demonstrations. Usual scales=3B Ex=92s, perqs and wages.
Now to put the feline in the aviary. How do other people assess if wedged =
and
kneaded clay is in it=92s optimum condition for throwing, for hand building,=
for
thumb pots, for slab rolling. Are there differences? If there are, please
describe them.
Ivor Lewis. Always willing to learn
vince pitelka on thu 13 apr 00
> Wedging infers that the clay is cut into two pieces which have the shape
> of wedge of cheese. The upper one is lifted from the lower one, turned
> over then slammed or slapped down hard on the wedge which remains
> on the bench. The block of clay is then rotated about a quarter of a
> revolution, cut, separated, turned over and slapped down again. This is
> repeated until the potter is satisfied that there are no more air pockets,
> twine, sticks, pebbles, all of which are picked out of the clay when they
> come to the surface.
> Kneading follows. Be it bulls head, rams head, spiral or chrysanthemum,
> the purpose is to make the now smooth clay uniform in colour, texture,
> plasticity.
Ivor -
As I pointed out before, the above may be common terminology outside the US,
but here, wedging refers to the bulls, rams head, sprial, etc. action.
Kneading is something we do to bread dough.
Best wishes -
- Vince
Vince Pitelka
Home - vpitelka@dekalb.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
http://www.craftcenter.tntech.edu/
Percy Toms on sat 15 apr 00
------------------
Ivor Lewis =3Ciandol=40tell.net.au=3E wrote
=3Csnip=3E
=3EI always taught that there were two essential processes. The first,
=3Ecalled
=3EWedging precedes the second, which is called Kneading.
=3Csnip=3E
=3ENow to put the feline in the aviary. How do other people assess
=3Eif wedged and kneaded clay is in it=92s optimum condition for throwing
=3Csnip=3E
Hi, Ivor
Here's my two cents on some if not all your posers
I did my potter training in England. For several years I was a
journeyman thrower at twenty potteries in two western US states
and a Canadian province.
Here's some of what I found:
None knew of the cut and slam wedging method. For them
clay preparation means spiral kneading (also confusingly called
wedging) or a pass or two through a pugmill. No wedging in the
way you define. BTW, a lot of potters use the terms wedging and
kneading synonymously. In England, too.
How did they tell when it was in optimum condition? Well, it's
not as if we're talking the equivalent of haute cuisine here,
Ivor. Think - army canteen. Think - slinging hash. As long as
the clay was throwable, and no bloating or other body problems,
they were in business - and in a hurry.
I did it my way - cut and slam first (which you describe
so well, Ivor - awesome to learn of the millions of layers=21),
then knead. It doesn't just put the clay in good heart - it puts =5Fme=5F in=
good
heart =3Cg=3E Certainly gets my circulation going.
There's also a major safety payoff. Getting set to throw yesterday
I found a small chunk of flaky METAL (not the first) in
my straight-from-the-supplier clay, and only because
my wire caught it.
Until a certain MAJOR clay company wakes up on quality control,
cut and slam wedging is not just clay preparation - it's injury
prevention too=21
Still, a good de-airing pugmill is practically vital in a production
pottery that does not dump - as in discard - tons of perfectly
good scraps and trimmings.
Brace yourself, Ivor... there ARE such places...=3Cscowling=3E
I came across wedging tables so high I once had to stand on two
clay boxes to wedge. The potter at that studio, by the way, had
=5Fprizewinning=5F upper body development... =3Cg=3E
Mostly I stood on one box (I stand 5ft 9ins). So many American
potteries I worked in had clay prep tables that were too high for
good kneading, even for the potters who built them. Why?
=3Cbaffled shrug=3E
=3EAir pockets rupture with explosive force. Rocks and coarse grog
=3Ecan fly like bullets. The piece in your hands is then brought
=3Edown with equal force onto the partner on the bench. More explosive
=3Eviolence=21=21
Is this kinetic poetry or what?=21 =3Cg=3E
An opportunity for peaceful and constructive explosive violence does not =
turn
up every day...=21 Hey - looks like an oxymoron just bit the dust=21
Sunderland slam wedging, here I come..=21 =3Cg=3E
Ned
Helen Bates on tue 18 apr 00
Ivor and Percy and others;
The cut and slam method: something like this was what I was first taught
when working with clay. Make a ball of clay; Cut it on the wire
mounted to the wedging board; slam the first resulting hemisphere cut
side down on the board, the plaster side of a board that was plaster on
one half and wood on the other; slam the second hemisphere, curved
surface down, on top of the first; pick all up and re-make into a ball;
repeat numerous times.
Our clay (I was an Occupational Therapy student at the time) had bits of
grass or other organic junk in it, so the cutting wire caught this and
removed it. After a while we would have a smooth piece of clay to work
with, and it would be air-pocket free as well, since the slamming was
done so the convex surfaces were the ones slammed into contact with each
other, thus making it much less likely that air could be trapped between
them (something like the use of a convex egg-shaped piece of clay thrown
onto the wheel before centering prevents air being trapped between the
clay and the wheelhead)l.
Learning now to work with clay over 35 years later, I do spiral wedging,
as I have recently been taught. We do cut with the wire, usually a
toggle-ended one, but it is more to check for air-pockets than to clean
the clay.
In the past, I had no idea what clay we used. I still have one piece,
coil built to a template, and rather heavy. Not much grog in it. May
have been gray earthenware, given the natural source it seems to have
come from.
Helen
--
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Helen Bates
mailto:nell@reach.net
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