Lesley Alexander on thu 15 feb 01
Dear List Members:
I recall someone writing in their pugmill produced short clay, so
they mixed it 50/50 with fresh. (Couldn't locate the reference in the
archives). I've tried that, and even after a week or more still have
very short pug clay. (sob). Does my old bluebird make a clay short? Do
pugmills in general do that? What experiences have others had with this?
Thanks for your thoughts.... Best wishes, from snowy (well, we can see
it on the mountains) Southern California.
Earl Brunner on fri 16 feb 01
Is it a short pugmill? If you put a board out there where the clay
comes out of the pugmill you should be able to get fairly long pieces of
clay. But if you don't support it they probably are breaking off in
short pieces.
JUST KIDDING!! Is your pugmill a deairing one?
Lesley Alexander wrote:
> Dear List Members:
> I recall someone writing in their pugmill produced short clay, so
> they mixed it 50/50 with fresh. (Couldn't locate the reference in the
> archives). I've tried that, and even after a week or more still have
> very short pug clay. (sob). Does my old bluebird make a clay short? Do
> pugmills in general do that? What experiences have others had with this?
> Thanks for your thoughts.... Best wishes, from snowy (well, we can see
> it on the mountains) Southern California.
>
> ______________________________________________________________________________
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--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
Martin Howard on fri 16 feb 01
No problem here mixing reclaim and fresh clay.
If I pug just reclaim, then it does seem to be rather tired and I do not get
as good results.
But, experts, WHY?
What is the science of short or tired clay?
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
tomsawyer on sat 17 feb 01
I have a Peter Pugger and have found that if my scraps completely dry before
mixing and pugging, the clay tends to be short. I read somewhere that the
addition of vinegar helps aging and that de-airing is particularly good. I
now use both techniques and leave in the pugger for about 24 hours; it is my
impression that the clay is more plastic.
Tom Sawyer
tsawyer@cfl.rr.com
Ceramic Design Group on sat 17 feb 01
on 2/15/01 8:41 PM, Lesley Alexander at celadon@SILCOM.COM wrote:
> Dear List Members:
> I recall someone writing in their pugmill produced short clay, so
> they mixed it 50/50 with fresh. (Couldn't locate the reference in the
> archives). I've tried that, and even after a week or more still have
> very short pug clay. (sob). Does my old bluebird make a clay short? Do
> pugmills in general do that? What experiences have others had with this?
> Thanks for your thoughts....
If your clay is just been mixed or you receive a fresh batch of premade clay
from your supplier, chances are that more than likely it will be short.
Industrial clay producers usually have a pugmill with two separate barrels.
These are connected by the vacuum chamber and then clay enters it after it
has passed through the screens. They also use much larger vacuum pumps
pulling huge vacuum and the clay is very well de-aired by this process.
Studio pugmills have an inline vacuum arrangement (except for the Van Ho)
and the deairing is accomplished through a small slot in the vacuum chamber.
The clay is deaired, but not as dense as what you receive from your
supplier.
We use a Bluebird Powerstar for all our clays, throwing consistency as well
as press consistency. The clay is well deaired for both processes. We mix in
boxed clay with our press scraps and it works fine. If we mix a fresh batch
of clay from dry materials, whether it is pugged or wedged right afterwards
it is still short. Read Dr. Lawrence's "Ceramic Science for the Potter" in
which he accurately talks about the water hull concept, a key to aging clay.
And, the water is also a key to getting really good clay. For instance, if
you mix your clay as a slurry, sieve it, and then filter press it before
pugging it, this will be the best clay you have ever used. Its because each
clay particle is surrounded by water.
Best
Jonathan
Jonathan Kaplan, president
Ceramic Design Group
PO Box 775112
Steamboat Springs CO 80477
voice and fax 970 879-9139
jdkaplan@cmn.net
info@ceramicdesigngroup.net
Plant Location:
1280 13th Street Unit 13
Steamboat Springs CO 80487
(please use this address for all deliveries via UPS, comman carrier, Fed Ex,
etc.)
"Custom design and manufacturing for the ceramic arts, giftware and pottery
industries. Molds, models, and tooling for slip casting, jiggering and
hydraulic pressing. Consultation on technical issues such as clay bodies
glazes, and kilns."
vince pitelka on sun 18 feb 01
> I have a Peter Pugger and have found that if my scraps completely dry
before
> mixing and pugging, the clay tends to be short. I read somewhere that the
> addition of vinegar helps aging and that de-airing is particularly good. I
> now use both techniques and leave in the pugger for about 24 hours; it is
my
> impression that the clay is more plastic.
Tom -
Anything slightly acidic will flocculate the clay, causing the particles to
attract one another, giving a more plastic clay. That is one of the things
that happens when clay ages - the organic activity produces acidic
byproducts, which flocculate the clay. The problem with vinegar is that it
will evaporate fairly quickly, but of course the clay is aging and wetting
at the same time which will improve plasticity. I prefer to use epsom
salts, 1/3 of 1% of the dry materials weight. Dissovle in hot water and
then add to the water for slaking down the dry scraps. This is a good
practice when mixing claybodies from dry materials, because it cannot hurt
anything, and if there is any chance of alkaline content from tapwater or
else dissolved from fluxes in the clay, the epsom salts will neutralize the
alkalinity and save you from having a seriously short clay. Many are the
claybodies which were discarded as unworkable when the only problem was a
slight alkalinity, easily remedied by a squirt or two of saturated epsom
salt solution wedged into the clay.
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/
Lili Krakowski on mon 19 feb 01
What can happen--I do not know, do not suggest--it is your problem is
that when you throw --as happens to us all--a lot of the finer particles
go into your slip bucket. You then dump the slip out (God forbid! Tell
me you don't!) or dry it out and use it on its own. Essentially,
simply--the slop may contain the finer more plastic particles.
Or why I tell students to take their "throwing water" out of the slop
pail, dilute it to ueability.
Reunite the slop with the clay you are processing. Experiment with drying
the slop then reuniting a cup full of slop with the approximate thickness
of commercial mayo or condensed soup as it comes out ot the can, with
maybe 4 cups of your clay. Wedge it up by hand and see how it feels. Go
from there.
Lili Krakowski
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