Mud Hen on thu 31 jan 02
The school I am at has a pug mill which either doesn't seem to work properly
or it really isn't worth the time to operate. It has not been operating for
years. When it was started up recently, the process was really slow and the
clay going through it was really wet. Therefore it came out too wet.
Therefore I am thinking this whole process is not worth my time.
However, I am still left with the problem of what to do with all of this
recyclable clay, but how to recycle the clay in an effcient manner.
sorry to be so long winded,
mudhen
L. P. Skeen on thu 31 jan 02
With pugmills other than the Peter Pugger, you must first dry out the clay
to throwing consistency before putting it in the mill. If you didn't do
that, you got mush. Try drying it more on plaster before pugging.
L
----- Original Message -----
From: "Mud Hen"
To:
Sent: Thursday, January 31, 2002 9:17 PM
Subject: pug mill question
> The school I am at has a pug mill which either doesn't seem to work
properly
> or it really isn't worth the time to operate. It has not been operating
for
> years. When it was started up recently, the process was really slow and
the
> clay going through it was really wet. Therefore it came out too wet.
> Therefore I am thinking this whole process is not worth my time.
>
> However, I am still left with the problem of what to do with all of this
> recyclable clay, but how to recycle the clay in an effcient manner.
>
> sorry to be so long winded,
> mudhen
>
>
____________________________________________________________________________
__
> 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.
>
Tommy Humphries on thu 31 jan 02
of course the process was slow if the clay going in was too wet... unless
the mill was a pugger/mixer the pugmill will not act as an efficient mixer.
Only introduce clay that has stiffened enough that it is not sticky. Too
soft clay will just sit in the mill and spin.
Properly used a pugmill is the greatest time & energy saver in the shop,
learn to use it right, and you will be one happy potter!
Tommy
----- Original Message -----
From: "Mud Hen"
To:
Sent: Thursday, January 31, 2002 8:17 PM
Subject: pug mill question
> The school I am at has a pug mill which either doesn't seem to work
properly
> or it really isn't worth the time to operate. It has not been operating
for
> years. When it was started up recently, the process was really slow and
the
> clay going through it was really wet. Therefore it came out too wet.
> Therefore I am thinking this whole process is not worth my time.
>
> However, I am still left with the problem of what to do with all of this
> recyclable clay, but how to recycle the clay in an effcient manner.
>
> sorry to be so long winded,
> mudhen
>
>
____________________________________________________________________________
__
> 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.
>
vince pitelka on fri 1 feb 02
> The school I am at has a pug mill which either doesn't seem to work
properly
> or it really isn't worth the time to operate. It has not been operating
for
> years. When it was started up recently, the process was really slow and
the
> clay going through it was really wet. Therefore it came out too wet.
> Therefore I am thinking this whole process is not worth my time.
Is this a re-post of a question from yesterday? I did not see the question,
but I saw an answer which seemed to address the above question. As was said
yesterday, pugmills do not work well with very wet clay. They need for the
clay to be normal plastic consistency in order to stick to the barrel and
the blades, in order to generate the friction to push the clay forward
through the barrel.
So no wonder the pugmill was slow and the clay coming out the end was too
wet. It is probably a perfectly good pugmill, but you need to stiffen the
recycle to plastic consistency BEFORE putting it through the pugmill.
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/
Martin Howard on fri 1 feb 02
My Dutch visitor, Cor, is an engineer.
My pug mill was going so slow, even after my version of cleaning.
He did a thorough job on it. Completely cleaned the barrel and the screen.
That is the secret.
If you leave any semi-hardened clay in the barrel it will immediately clog
the screen again and cause slow pugging.
So, get cleaning and have a machine which works as well as it did when you
first had it!
Martin Howard
Webbs Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
01371 850 423
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
Updated 27th January 2002
iandol on sun 3 feb 02
Dear Vince Pitelka <>
You say <order to stick to the barrel and the blades, in order to generate the =
friction to push the clay forward through the barrel.>>
As I understand it, the plastic stuff does not stick to the blades but =
slides easily across the polished steel. The flights push it forward =
making room for what comes in from behind. It's the soft wet stuff that =
causes the problems. It exudes backwards between the edge of the auger =
blades and the barrel. Ideally, there should be a minimum clearance =
between the flights and the barrel. This is important since it leaves a =
layer of unmoved clay which acts to protect the barrel from wear and =
extends the life of the machine. Problems happen as the flights wear and =
this clearance develops into a wide gap. It is not a difficult task for =
a good welding engineer to build up the edges of the flights with =
Stellite when they wear and to put a facing coat of Colmonoy "Sweat on =
Paste" on the leading face of the flights to prevent wear when a lot of =
heavily grogged clay is being processed.
Some people ill treat their pug mills by trying to use the hopper =
plunger as a way of forcing clay into the machine when it is fully =
loaded in the mistaken belief that this will accelerate production. =
When flights are tuned to the rate of rotation they drag clay into the =
barrel almost as fast as you can drop it into the machine. I have seen =
examples where the lever has been bent like a banana through such strong =
arm tactics.
All the best,
Ivor Lewis. Redhill, South Australia
vince pitelka on mon 4 feb 02
Ivor wrote:
"As I understand it, the plastic stuff does not stick to the blades but
slides easily across the polished steel. The flights push it forward making
room for what comes in from behind. It's the soft wet stuff that causes the
problems. It exudes backwards between the edge of the auger blades and the
barrel."
The clay certainly polishes the blades, but it is essential that the clay
tries to stick to the blades, as that provides the necessary friction to
move the clay through the mill. And of course it is absolutely essential
that the clay stick to the barrel, or else it would just turn as one big
slug."
You wrote:
"Ideally, there should be a minimum clearance between the flights and the
barrel. This is important since it leaves a layer of unmoved clay which acts
to protect the barrel from wear and extends the life of the machine.
Problems happen as the flights wear and this clearance develops into a wide
gap."
It is true that there should be clearance, but the primary reason is to
improve the performance of the mill. The clearance allows a layer of clay
to stick to the barrel, but the primary effect is that the stuck clay trys
to keep the mass of clay from rotating, while the blades are forcing the
clay to rotate and move. The end result is very thorough pugging. The
blades push the clay forwards through the mill, but they also push it
outwards towards the barrel, so that this layer of clay is constantly
moving. So it is not just a stationary layer of clay against the barrel.
Some people building homemade mills have designed them with almost no
clearance, and these mills do not work nearly as well. Harry Davis writes
about how this clearance is essential to guarantee proper functioning of the
mill.
As you point out, soft clay just slips past the blades without moving
forwards, but it also does not stick to the barrel, and thus there is little
forward movement.
You wrote:
"Some people ill treat their pug mills by trying to use the hopper plunger
as a way of forcing clay into the machine when it is fully loaded in the
mistaken belief that this will accelerate production. When flights are tuned
to the rate of rotation they drag clay into the barrel almost as fast as you
can drop it into the machine. I have seen examples where the lever has been
bent like a banana through such strong arm tactics."
In the best possible circumstances, with clay of the proper consistency, it
is rarely necessary to use the hopper plunger, as you point out. If I am
pugging clay of good plastic consistency in my homemade Harry Davis pugmill,
the mill eats it up with no plunger, and the same is true of our Bluebird
mill. But I often pug stiff clay dipped in water, and it is often necessary
to use the plunger to get it going in the barrel. Also, I often pug a mix
of soft and hard clay, and again the plunger is often needed to get this
clay intermixing so that it will move through the mill on its own.
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/
Gavin Stairs on tue 5 feb 02
Dear Ivor and Vince,
May I interject a note of fluid dynamics into this discusssion?
The role of friction in the pug mill is both to impede and to permit the
proper action. In fluid dynamics, we recognize that all true fluids are
stationary at the walls of a vessel, even when the fluid is in motion in
the centre of the vessel. The same is true at the surface of the blades or
flights of a pug mill, as well as at the sides of the barrel. This gives
rise to shear in the body of the clay, as clay moves at different
velocities throughout the mill. This is what mixes the clay.
The clay tries to resist this shear. In a true fluid, this resistance is
called viscosity. Clay is more complicated than a true fluid. It has some
ability to support a shear load without deforming plastically, like a
solid. The degree to which the clay can do this varies with the shear
deformation, and with other factors, such as vibration or heat. To use ten
dollar words, it behaves like a thixotropic gel. So, under a shear load,
some clays will separate into a solid like gel phase, and a relatively thin
liquid, shear phase. When this happens in the pug mill, we may say that
the clay is sticking to the barrel and auger, and it tends to stall in the
mill. In nature, this can lead to a landslide.
So, if the pug mill contained a true fluid, we would see the auger push the
fluid along, not by its friction with the blades, but in spite of it, but
it would resist the tendency to simply spin in the barrel because of the
friction at the walls, augmented in some cases by the scalloping. In a
true axial flow turbine, the auger is the rotor, with blades shaped to give
a momentum impulse to the fluid, while the barrel is the stator, with
geometry designed to counter the rotational impulse, converting it to an
axial impulse. So the fluid moves along instead of around.
In the case of a pug mill with clay, the basic impulses are the same, but
the motion is complicated by the tendency of the clay to separate into
different flow phases.
The gaps in the pug mill are designed to avoid an excessive shear zone at
the narrowest gap, which would lead to excessive wear in that region, and
would exacerbate the tendency of the clay to separate into liquid and solid
phases: liquid at the gap, solid in the centre of the auger. That
behaviour leads to a stalled pug. A pug mill will stall if the back
pressure is too great (clogged screens, to small an exit cone, too
restrictive an extrusion nozzle), or if the water content is too great. It
may also stall if the clay is not well mixed, as the watery clay may end up
in this zone, with the hard stuff going round and round in the auger. The
whole geometry of the mill is a set of compromises between the desired
shear and the undesirable tendency of the clay to break up into solid and
liquid phases.
I hope this helps rather than hinders the discussion.
Gavin
Gavin Stairs
Stairs Small Systems
525 Canterbury Road
London, Ontario
Canada N6G 2N5
telephone: (519) 434-8555.
email: stairs@stairs.on.ca
Attention!
On February 30, 2001 we moved to the above address from our
old address:
1A - 921 College Street
Toronto, Ontario, Canada M6H 1A1
phone: (416)530-0419 stairs@stairs.on.ca
Gene and Dolita Dohrman on thu 28 aug 03
Bailey has come out with a pug mill - single auger - which is being sold =
at a special price through the month of September. I am very tempted =
even though it will blow my budget for the new studio. At 53, I want to =
do everything that will prolong my ability to throw pots and I =
understand a pug mill will save an immense amount of wedging. It was =
stated than a single auger will cause a spiral in the clay - this, of =
course, was the selling point of their twin auger pug mill which I =
really cannot afford. Do any of you have opinions on this? I am trying =
to make smart choices and not go over board on the equipment. =20
Dolita
dohrman@insightbb.com
Gene and Dolita Dohrman
1811 Edenside Avenue
Louisville, Ky 40204
Phone 502-749-1513
Craig Dunn Clark on thu 28 aug 03
Gene, I used a single auger Venco deairing pugmill for a number of years. Ir
worked very well. I was not aware of any spiral in the clay.
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: "Gene and Dolita Dohrman"
To:
Sent: Thursday, August 28, 2003 10:10 AM
Subject: Pug Mill Question
Bailey has come out with a pug mill - single auger - which is being sold at
a special price through the month of September. I am very tempted even
though it will blow my budget for the new studio. At 53, I want to do
everything that will prolong my ability to throw pots and I understand a pug
mill will save an immense amount of wedging. It was stated than a single
auger will cause a spiral in the clay - this, of course, was the selling
point of their twin auger pug mill which I really cannot afford. Do any of
you have opinions on this? I am trying to make smart choices and not go
over board on the equipment.
Dolita
dohrman@insightbb.com
Gene and Dolita Dohrman
1811 Edenside Avenue
Louisville, Ky 40204
Phone 502-749-1513
____________________________________________________________________________
__
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 thu 28 aug 03
Dolita,
Effective deairing is particularly helpful in minimizing the spiral you
refer to. I believe the mill is deairing, so that is a plus.
All pugmills that only pug are inefficient clay mixers. Poor mixing is
the real culprit in causing S-cracks.
You can run clay through the mill multiple times to get it better mixed.
Also, some clay bodies are more problematic regarding mixing. Porcelains
and fine, high-bentonite bodies need to be mixed very well. Differences in
moisture content through the clay can cause cracking in drying ware thrown
from such clay. In my experience, it is best to take the pug of clay and
slam wedge or spiral knead it just before use. That warm up, for you and
the clay, is not a bad thing to do in any case.
Hope you new studio turns out well!
Dave Finkelnburg
----- Original Message -----
From: "Gene and Dolita Dohrman"
Bailey has come out with a pug mill - single auger - which is being sold at
a special price through the month of September. I am very tempted even
though it will blow my budget for the new studio. At 53, I want to do
everything that will prolong my ability to throw pots and I understand a pug
mill will save an immense amount of wedging. It was stated than a single
auger will cause a spiral in the clay - this, of course, was the selling
point of their twin auger pug mill which I really cannot afford. Do any of
you have opinions on this? I am trying to make smart choices and not go
over board on the equipment.
Hank Murrow on thu 28 aug 03
On Thursday, August 28, 2003, at 08:10 AM, Gene and Dolita Dohrman
wrote:
> Bailey has come out with a pug mill - single auger - which is being
> sold at a special price through the month of September. I am very
> tempted even though it will blow my budget for the new studio. At 53,
> I want to do everything that will prolong my ability to throw pots and
> I understand a pug mill will save an immense amount of wedging. It
> was stated than a single auger will cause a spiral in the clay - this,
> of course, was the selling point of their twin auger pug mill which I
> really cannot afford. Do any of you have opinions on this? I am
> trying to make smart choices and not go over board on the equipment.
Dear Dolita;
Any single auger pug mill will put some torque into the pugged clay,
and necessitate some finishing wedging. The double auger design is
meant to minimize this, and will reduce the need for wedging. That
said, the Bailey, while only pugging a 2.5" column of clay, has a very
nice feed design and quality parts. I might have gone for the Bailey,
except that Pat of Bend, OR offered me a deal on a brand new Venco,
which I will modify to 'copy' the Bailey feed design.
That said; the most cost effective and simple way to quality clay would
be to mix your clay in a blunger to malted milk consistency, sieve it
with a 'Harry Davis" vibrating sieve, and dry it out to wedging
consistency in poly-canvas bags. I am setting up again to do this after
a lapse of ten years, while the pug mill will help me recycle scraps.
The best clay is clay which has been thoroughly wetted.
Hope this helps you, Hank in Eugene
Dave Lyons on fri 19 jun 09
Hello Everyone,
I've been pugging along reclaiming my buckets of scraps with my recently
acquired Walker. I'm well pleased with it and I'm being very careful. By
the way for those who responded, thanks for all the safety tips. I'm down
to some really thin scraps and I'd like to thicken them up a little. I've
got some EPK or OM4 that I can choose from to add to the slurry. I fire
mostly cone 6 in stoneware. Most of my scrap consists of B Mix, Goldart, o=
r
Redart. Does it matter if I use the EPK or the OM 4 in regards to
plasticity and workability?
Dave Lyons
Lee Love on sat 20 jun 09
On Fri, Jun 19, 2009 at 11:44 PM, Dave Lyons wrote:
> mostly cone 6 in stoneware. =3DA0Most of my scrap consists of B Mix, Gold=
ar=3D
t, or
> Redart. =3DA0Does it matter if I use the EPK or the OM 4 in regards to
> plasticity and workability?
> Dave Lyons
Dave, can you buy some dry B mix from your clay provider? Firing at
cone 6, you might change the quality of your clay just adding these
clays. I often buy dry clays for slip from Continental Clay. I
use their white lowfire as a slip on and in their red lowfire body.
I use their Super White for high fire hakame. It is also an excellent
flashing slip in soda. If you match up shrinkages, you can't go
wrong.
Tim Frederich dropped off some of his new fireclays and also
natural grogs of varying mesh. I threw the fireclay straight up,
with only multiple sized grog added, and water and it was very
short. Cracking at the lip if I wasn't careful. But the texture
after trimming was awesome. It will be "too refractory" as far as
industry is concerned, but I have been looking for something that is
something like Mogusa. Mogusa is still absorbent after firing to
cone 13 twice. The tea masters liked it, because it had a bisque
like softness after glaze firing that reminded them of raku.
I will fire some test tea bowls, which will tell me what I need to
add to get the effect I want. But this is for high temp and for a
particular result.
--=3D20
--
Lee Love, Minneapolis
"The tea ceremony bowl is the ceramic equivalent of a sonnet: a
small-scale, seemingly constricted form that challenges the artist to
go beyond mere technical virtuosity and find an approach that both
satisfies and transcends the conventions." -- Rob Sliberman
full essay: http://togeika.multiply.com/journal/item/273/
Sherron & Jim Bowen on sat 20 jun 09
"The tea masters liked it, because it had a bisque like softness after glaz=
e
firing that reminded them of raku."
Was that because the whisking made a more pleasing sound?
JB
----- Original Message -----
From: "Lee Love"
To:
Sent: Saturday, June 20, 2009 7:26 AM
Subject: Re: Pug mill question
John Rodgers on sat 20 jun 09
Dave,
I can't address your question specifically,
but;
I use both B-mix pugged clay and B-mix slip clay. The latter I buy
pre-mixed, dry, in 50 lb bags. While the composition of the slip-type
B-mix is slightly different from that of the pugged B-mix, I have never
found it a problem in using the dry B-mix slip clay to stiffen up the
clay going through the pugmill if it's too wet. The two are so close in
composition that the small quantities added to dry out the pugged clay
doesn't have any noticeable effect on throwing once the clay is processed.
I suggest that you keep a bag of the slip B-mix on hand just for that
use - even if you are not into slip casting.
BTW, I have a Walker mill myself.
Regards,
John Rodgers
Chelsea, AL
Dave Lyons wrote:
> Hello Everyone,
> I've been pugging along reclaiming my buckets of scraps with my recently
> acquired Walker. I'm well pleased with it and I'm being very careful. B=
y
> the way for those who responded, thanks for all the safety tips. I'm dow=
n
> to some really thin scraps and I'd like to thicken them up a little. I'v=
e
> got some EPK or OM4 that I can choose from to add to the slurry. I fire
> mostly cone 6 in stoneware. Most of my scrap consists of B Mix, Goldart,=
or
> Redart. Does it matter if I use the EPK or the OM 4 in regards to
> plasticity and workability?
> Dave Lyons
>
>
>
| |
|
