The Wrights on thu 28 sep 00
Hi:
I'm not sure, but do Pug Mills de-air? If so, does this eliminate the
need to wedge clay?
Thanks,
Flo
Czola on fri 29 sep 00
Yes, in theory, pug mills with a vacuum seal remove air as well as foreign
matter from reclaimed clay. You should always wedge clay before throwing
with it, for a number of practical and technical reasons. (though if you're
just throwing an itty bitty something, it's not so important)
Wedging will get the clay platelets all going in the right direction
You'll get a feel for the clay, its plasticity, its age, moisture content,
etc
you'll get those last few air bubbles out
it gives you wonderfully strong forearms.
But a pug mill is a fabulous thing, especially in a school setting, where
you're reclaiming tons of clay and don't want to throw with twist ties and
chamis in your clay body.
Cindy Strnad on fri 29 sep 00
Hi, Flo.
Some pug mills de-air. As to whether it eliminates the need to knead, you'll
get mixed reviews on that. I say, yes, unless you're making large ware, in
which case, the pugged clay is unsuitable because of it's shape and will
require kneading to get it into a usable sized and shaped piece. In fact,
some on this list have suggested that most pug mills de-air quite
effeciently by compression alone, and that the vacuum pump may be
superfluous.
Keep in mind, however, that I use a Peter Pugger combination mixer and
de-airing pugger, so my clay is very well mixed before I turn on the pugging
cycle. If you're using batches of clay with differing moisture content, that
makes a difference. They need to be thoroughly mixed, and when you're
working by hand, you do that by wedging.
My definitions, since there's a difference in the ways these words are used:
Wedge
To cut a lump of clay in half, then slam the halves down, one on
top of the other. This cycle is repeated until the clay is well mixed.
Knead
To work the clay in a shell-like spiral patern. This helps to remove
trapped air and to warm and soften the clay into workability.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
www.earthenvesselssd.com
Dave Finkelnburg on fri 29 sep 00
Hi Flo!
First, some pugmills de-air, others do not. It depends on whether the
one you buy has a vacuum pump attached, which is what's required to remove
the air. They cost extra. With the vacuum pump they do a fantastic job of
removing the air!
Second, yes, you can use clay right out of the pugmill. I do. However,
not everyone does.
You have opened a can of worms! :-)
There are those who will take you (and me) to task over using the word
wedging (versus kneading).
There are those who will say the answer to your question about wedging
is, "Absolutely not!."
I am more generous. I'd really say, it depends. :-)
I assume that by wedging you mean you want to make your clay suitable
for throwing by working it by hand to remove trapped air bubbles and make
the moisture in the clay uniform throughout. (In some parts of the world
this process is called kneading.)
Hand wedging or kneading may or may not be necessary after pugmilling,
depending on your clay body and how you will use the clay.
A typical pugmill puts a strong spiral force into the clay. If you use
your clay relatively dry, and take it straight from the mill, and orient the
spiral vertically on the wheel in the same direction as the spiral force you
add while throwing, you can create a strong force for "S"-cracking in the
foot of pieces you throw. Of course, you can do the same thing with spiral
wedging (kneading). Clay containing lots of coarse material such as grog or
fireclay shows this dramatically. For some work you may want to disrupt
this spiral by working the clay by hand in some manner, such as by either
wedging or kneading.
If your store the pugged clay any length of time before use, and the
surface dries out even a bit, then you should either pug it again or wedge
(knead) it enough so the moisture becomes uniform again across the clay.
I might add, good pugmills are expensive. Kneading clay can be good
exercise. Unless you are in such a production situation that you go through
a lot of clay, a pugmill can be an expense that does not pay.
Good potting!
Dave Finkelnburg in Idaho
Flo wrote:>I'm not sure, but do Pug Mills de-air? If so, does this
eliminate the
>need to wedge clay?
Martin Howard on fri 29 sep 00
Flo, YES.
If it is a Venco De-airing Pug Mill.
Other de-airers may also work in much the same way.
I have never wedged any clay since I had my machine.
My thumb joints, ruined by previous wedging and kneading are taking a well
earned rest.
But, when you put the clay on the wheel, cone it up and down three times, as
part of centering, before throwing. Good practice in any case, but if you
have made an air pocket by handling the clay a little clumsily, that process
will get rid of it and make the clay much more amenable for your subsequent
throwing.
Get one, soon.
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
vince pitelka on fri 29 sep 00
> I'm not sure, but do Pug Mills de-air? If so, does this eliminate the
> need to wedge clay?
Flo -
You will get varying opinions on this, but yes, a good vacuum de-airing
pugmill will eliminate the need for wedging. I used one in production for
years, and my wrists are better for it. I bought my clay once a year in
very large quantities, and after sitting for a long time it needed wedging,
and a quick pass through the pugmill really primed it for throwing.
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/
Tommy Humphries on sat 30 sep 00
Some do others don"t remove air, depends on the type you have.
As to eliminating the wedging, this has been a matter of discussion before,
with no clear consensus here. Speaking from my personal experience though,
with proper throwing techniques, you certainly can throw excellent pots
without wedging properly de-aired clay. I use between 500-1200 lb.. of clay
every day and all is straight from the pugmill. All that is ever done prior
to throwing it is to round off the face on the larger balls to ease the
centering a bit. This amount of clay represents anywhere from 150-300 pots a
day, and there is 0-1.5% s-cracking and less than 3% loss overall. All pots
are left to dry upright on boards till dry and dry finished, usually within
3 days. If not wedging created stresses (due to particle mis-alignment) then
this radical handling of ware would result in mass failure of the pots in
the drying stage. THIS IS SIMPLY NOT THE CASE!
For a bit of information on the clay that we use see David Hendlys excellent
article on Blackjack clay Co. , in this months Ceramics Monthly.
Tommy Humphries
(4th. generation potter, in the southern folk potter tradition!)
----- Original Message -----
From: "The Wrights"
To:
Sent: Thursday, September 28, 2000 10:24 PM
Subject: De-Airing Pug Mill
> Hi:
>
> I'm not sure, but do Pug Mills de-air? If so, does this eliminate the
> need to wedge clay?
>
> Thanks,
>
> Flo
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
>
Dave Finkelnburg on sun 1 oct 00
Hi Tommy!
I expected you to respond to this thread! :-)
Thanks to your comments and advice, I am now throwing most of my work
directly out of the pugmill. I am adding water to make the clay a lot
softer now, which really is helping me throw. Bowls and platters really
seem to benefit from the softer clay. I still struggle with taller pieces
with the soft clay, though. They either want to torque or settle down from
their own weight Plenty to work on! :-)
Good potting!
Dave Finkelnburg on a windy day in Idaho watching the clouds
screaming by the hilltop at an amazing speed!
-----Original Message-----
From: Tommy Humphries
To: CLAYART@LSV.CERAMICS.ORG
Date: Saturday, September 30, 2000 8:37 PM
Subject: Re: De-Airing Pug Mill
>Some do others don"t remove air, depends on the type you have.
>
>As to eliminating the wedging, this has been a matter of discussion before,
>with no clear consensus here. Speaking from my personal experience though,
>with proper throwing techniques, you certainly can throw excellent pots
>without wedging properly de-aired clay. I use between 500-1200 lb.. of clay
>every day and all is straight from the pugmill. All that is ever done prior
>to throwing it is to round off the face on the larger balls to ease the
>centering a bit. This amount of clay represents anywhere from 150-300 pots
a
>day, and there is 0-1.5% s-cracking and less than 3% loss overall. All pots
>are left to dry upright on boards till dry and dry finished, usually within
>3 days. If not wedging created stresses (due to particle mis-alignment)
then
>this radical handling of ware would result in mass failure of the pots in
>the drying stage. THIS IS SIMPLY NOT THE CASE!
>
>For a bit of information on the clay that we use see David Hendlys
excellent
>article on Blackjack clay Co. , in this months Ceramics Monthly.
>
>Tommy Humphries
>(4th. generation potter, in the southern folk potter tradition!)
>
>
>----- Original Message -----
>From: "The Wrights"
>To:
>Sent: Thursday, September 28, 2000 10:24 PM
>Subject: De-Airing Pug Mill
>
>
>> Hi:
>>
>> I'm not sure, but do Pug Mills de-air? If so, does this eliminate the
>> need to wedge clay?
>>
>> Thanks,
>>
>> Flo
>>
>>
>___________________________________________________________________________
_
>__
>> Send postings to clayart@lsv.ceramics.org
>>
>> You may look at the archives for the list or change your subscription
>> settings from http://www.ceramics.org/clayart/
>>
>> Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
>>
>
>___________________________________________________________________________
___
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
>
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