Martin Howard on wed 4 jul 01
I have been asked by a potting engineer, who makes wheels and all sorts of
useful gadgets for us, a very simple question.
pugger and those from one which does not de-air?>
We assume there is a difference and that the de-airer is best. But is it
really?
So, could a few of you do, with me, a test of a few pots, all the same; one
set from the pugger with de-airing ON and the other with it OFF?
It may be purely the compression which causes the pugger effect, just like
with hand wedging and kneading.
We can so easily believe fairy stories and potters myths!!
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
DEBBYGrant@AOL.COM on wed 4 jul 01
Martin,
This is a very interesting question and I have been thinking about it
for a long time. I have used both a deairing pugmill and a non deairing
one. The pugmill I use in my studio is 25 years old and non-deairing.
When I use it I take a handful of new clay and then a handful of reclaimed
clay and pug everything through 3 times. The result is a very plastic
homogenous body. When I used the deairing pugmill at the school
where I taught I again combined new clay with reclaimed clay but only
pugged it through once. I always felt that the deairing caused the clay
to be much denser and less plastic. I even have friends with a deairing
pugmill who do not turn on the vacuum and continue to pug the way
I do in my studio. I would be very interested in hearing what others think
about this.
Debby Grant in NH
Karen Sullivan on wed 4 jul 01
Debby....
I will go through intense labor to use just mixed...
non-pugged clay...As the open claybody feels livelier,
more generous in it's potential for gesture than does
pugged clay.
bamboo karen
on 7/4/01 6:23 AM, DEBBYGrant@AOL.COM at DEBBYGrant@AOL.COM wrote:
> Martin,
>
> This is a very interesting question and I have been thinking about it
> for a long time. I have used both a deairing pugmill and a non deairing
> one. The pugmill I use in my studio is 25 years old and non-deairing.
> When I use it I take a handful of new clay and then a handful of reclaimed
> clay and pug everything through 3 times. The result is a very plastic
> homogenous body. When I used the deairing pugmill at the school
> where I taught I again combined new clay with reclaimed clay but only
> pugged it through once. I always felt that the deairing caused the clay
> to be much denser and less plastic. I even have friends with a deairing
> pugmill who do not turn on the vacuum and continue to pug the way
> I do in my studio. I would be very interested in hearing what others think
> about this.
>
> Debby Grant in NH
>
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vince pitelka on wed 4 jul 01
> We assume there is a difference and that the de-airer is best. But is it
> really?
> So, could a few of you do, with me, a test of a few pots, all the same;
one
> set from the pugger with de-airing ON and the other with it OFF?
Martin -
This is not an appropriate test, because most deairing pugmills are not
designed to operate efficiently with the vacuum turned off. I have a
homemade Harry Davis deairing mill, and the Craft Center has a Venco
deairing and a Bluebird non-deairing. The Davis and the Venco do not work
especially well with the vacuum turned off, while the Bluebird works great.
The clay it produces is not completely deaired of course, but far more so
than the clay from the first two with the vacuum turned off. It is all in
the design of the barrel, the mixing vanes, and the helixes (if any).
So to do your test properly you really need to work with clay from deairing
and non-deairing mills. I have worked extensively with both, and find that
clay from the non-deairing mill always has to be wedged, while I never have
to wedge the deaired clay. With the exception of porcelain and whiteware, I
think that well-wedged clay from a non-deairing mill works about the same as
non-wedged clay from a deairing mill. I my experience, porcelain and
whiteware bodies always works better when they are deaired.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Tommy Humphries on wed 4 jul 01
I can answer this without any further testing, as it is readily apparent
when the de-airing chamber of a pugmill stops up. When the mill is de-airing
properly the pugs come out smooth and very dense, cut a thin strip and bend
it it bends, pull the ends and it stretches (somewhat).
When the chamber is stopped up or the pump is off the clay comes out of the
mill in a rougher state, and will feel almost "fluffy" cut a thin strip and
bend it it will separate and break, pull the ends and it will tear, with no
predictable pattern.
On the wheel. non de-aired clay straight from the mill will often separate
during a pull, leaving holes in the walls of the pots... is very prone to
s-cracks from delamination ( I have seen s-cracks that crossed the bottoms
and spiraled up the sides!) .
One of the drawbacks with de-aired clay is that it can over stiffen the
clay, clay that is "just right" when put into the mill will lose some water
do the evaporation during the de-airing process, as the water will boil
under the extreme vacuum encountered. Just add a bit extra water and all
will be fine.
If you are running a de-airing pugmill and your clay seems short, but the
gauges say a good vacuum is being achieved, check the plumbing from the pump
to the mill, as sometimes the clay can spit and clog these lines between the
mill and the gauge.
Tommy
----- Original Message -----
From: "Martin Howard"
To:
Sent: Wednesday, July 04, 2001 1:58 AM
Subject: pugging and de-airing
> I have been asked by a potting engineer, who makes wheels and all sorts of
> useful gadgets for us, a very simple question.
>
> > pugger and those from one which does not de-air?>
>
>
KLeSueur@AOL.COM on wed 4 jul 01
My first pugmill was a Bluebird studio non de-airing model. I used it for 10
years and was well satisfied with the clay it put out. But it did need
wedging. I sold it and it is still in use. Now 22 years old. I replaced it
with a Bluebird Powerstar de-airing pugmill. The clay from it is superior to
the non de-airing. It requires no wedging. It took very little time to learn
how to blend scrap and new clay to get the right consistency from the mill.
I recommend de-airing.
Kathi LeSueur
Ron Collins on thu 5 jul 01
I don't pug anything, but have an opinion...before coming here, I used
bagged, purchased very dense clay...have to make my own here, for myself and
students...mix it dry in wide pastic storage containers with a turbo mixer
on a drill, add water, let sit, put in fabric and dry out outside on gravel,
age, wedge and use-no equipment at all.....It's so easy and fun to throw, my
wheel work is so much better with this soft clay, and it shrinks very
little. Even if I had the choice of getting premixed clay, I'd still make
my own after seeing the difference..it's not that much trouble...and I still
wouldn't bother to buy any equipment to make it, as I am a studio, not
production potter....Melinda in Guatemala...
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