artimater on wed 18 apr 01
My friend Aki uses a chamois on the end of a piece of wood to =
compress while the clay is wet.....Otherwise I think the clay would act =
like a liquid(think bag of popcorn....squish one side down the other =
side comes up).....I do most of my compressing while the pots are =
leatherhard......Usually spit on my finger....Porcelain will actually =
reflow and fill a crack.....Stoneware takes alot of spit to do =
same....Anyway that semi- burnish at leatherhard after trimming makes =
more sense to me than trying to compress them while they are =
wet....yup,yup...Also makes the bottom nice and smooth for your =
table....yup,yup....I also do what I think is useless by compressing =
when wet....yup,yup.....And I use nekkid kiln gods....yup,yup
I like "s" cracks like I do blowing pots up in the bisque,
Rush
"I only indulge when I've seen a snake, so I keep a supply of =
indulgences and snakes handy"
http://www.geocities.com/artimator/index.html
artimator@earthlink.net
Michael McDowell on thu 19 apr 01
This discussion seems to me to be more about semantics, the meanings
arbitrarily assigned to words, than it is about facts. For those of us wi=
th
backgrounds in the hard sciences, the term "compression" has a specific
meaning. Roughly, that meaning would be to pack molecules more tightly
together so that the mass of the material under compression increases. In=
this
sense, I would have to agree with Ivor and those others who have taken th=
e
position that it is not possible to "compress" clay by hand working it.
But another meaning has come to be attached to the word "compress" by a l=
arge
number of potters in the U. S. at least. Here it refers to a particular
pattern of motion with respect to the clay that has been observed over ti=
me,
and by many clay workers, to reduce "S" cracks. Let us just say that the =
word
"compression" has been arbitrarily assigned to "mean" that pattern of mot=
ion.
When such arbitrary assignments of unconventional meanings are made in a =
field
of interest, it is called "jargon". There is also a "story" or a "working
hypothesis" that is often attached as well. This story is that the patter=
n of
motion called "compression" by many, results in a larger proportion of cl=
ay
platelets being oriented with their long axes parallel to the plane of th=
e
surface being worked. If we accept this story, it can serve as an explana=
tion
of how the pattern of movement serves to reduce cracking. This would be t=
he
result of fewer spaces between platelets along that plane.
Should we choose to reject the arbitrary assignment of the word compressi=
on to
this pattern of motion, it does not disprove the observed results. Simila=
rly,
should we disprove the theory of why it works, we are still left with the=
fact
THAT it works to reduce cracking. Now if someone was to disprove to me TH=
AT it
works, this might allow for some change in how I make my pots. THAT would=
be
interesting...
Michael McDowell
Whatcom County, WA USA
mmpots@memes.com
http://www2.memes.com/mmpots
Tom Wirt/Betsy Price on fri 20 apr 01
But Marek...you're missing one point here....If you put throwing water
inside a pot, and the proceed to "compress" the bottom, the water will
disappear into the clay. So...water cannot be compressed, clay cannot
be compressed (it is a solid) and the water goes into, not out of, the
clay. All the evidence I see says that you are doing something rather
than compression (by standard definitions).
2 cents worth,
Tom Wirt
----- Original Message -----
>>Subject: compressing bottoms
Dear Ivor, Mike et al,
>and I don't think it is about semantics -
>- more a matter of empirical learning.
>Clay is formed by compressing it. If you roll a >coil,pinch a thumb
pot, make a slab, throw a pot on a >wheel, pull a handle, you are
using compression to >make the form you want. And it is made stronger
by >compressing it, and the only way I know that this can >be is that
the clay particles come closer together. I >know this is so through my
empirical learning, not >through any scientific explanations -
although I am >sure that they will prove this to be so. The converse
of
Chris Clarke on fri 20 apr 01
I think instead of the word compressing we should all use the word squish=
ing
(since the C word has given so many such a start). I don't think it's
attached to any scientific meaning. That way we could agree that squishin=
g
the bottom of a pot helps to keep away s-cracks, whatever works. : )
chris
Sunny California where the roses are blooming and the butterflies are
migrating past my studio.
chris@ccpots.com
www.ccpots.com
----- Original Message -----
From: Michael McDowell
To:
Sent: Thursday, April 19, 2001 10:42 AM
Subject: Compressing bottoms
> This discussion seems to me to be more about semantics, the meanings
> arbitrarily assigned to words, than it is about facts. For those of us
with
> backgrounds in the hard sciences, the term "compression" has a specific
> meaning. Roughly, that meaning would be to pack molecules more tightly
> together so that the mass of the material under compression increases. =
In
this
> sense, I would have to agree with Ivor and those others who have taken =
the
> position that it is not possible to "compress" clay by hand working it.
>
> But another meaning has come to be attached to the word "compress" by a
large
> number of potters in the U. S. at least. Here it refers to a particular
> pattern of motion with respect to the clay that has been observed over
time,
> and by many clay workers, to reduce "S" cracks. Let us just say that th=
e
word
> "compression" has been arbitrarily assigned to "mean" that pattern of
motion.
> When such arbitrary assignments of unconventional meanings are made in =
a
field
> of interest, it is called "jargon". There is also a "story" or a "worki=
ng
> hypothesis" that is often attached as well. This story is that the patt=
ern
of
> motion called "compression" by many, results in a larger proportion of
clay
> platelets being oriented with their long axes parallel to the plane of =
the
> surface being worked. If we accept this story, it can serve as an
explanation
> of how the pattern of movement serves to reduce cracking. This would be
the
> result of fewer spaces between platelets along that plane.
>
> Should we choose to reject the arbitrary assignment of the word
compression to
> this pattern of motion, it does not disprove the observed results.
Similarly,
> should we disprove the theory of why it works, we are still left with t=
he
fact
> THAT it works to reduce cracking. Now if someone was to disprove to me
THAT it
> works, this might allow for some change in how I make my pots. THAT wou=
ld
be
> interesting...
>
> Michael McDowell
> Whatcom County, WA USA
> mmpots@memes.com
> http://www2.memes.com/mmpots
>
>
_________________________________________________________________________=
___
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
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>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Marek & Pauline Drzazga-Donaldson on fri 20 apr 01
Dear Ivor, Mike et al,
I must agree with Vince here with compression, and I don't think it is =3D
about semantics - didn't they have several hit records out in the early =3D
70's? - more a matter of empirical learning.
Clay is formed by compressing it. If you roll a coil,pinch a thumb pot, =3D
make a slab, throw a pot on a wheel, pull a handle, you are using =3D
compression to make the form you want. And it is made stronger by =3D
compressing it, and the only way I know that this can be is that the =3D
clay particles come closer together. I know this is so through my =3D
empirical learning, not through any scientific explanations - although I =
=3D
am sure that they will prove this to be so. The converse of making a =3D
strong form by compression is to stretch clay and see how weak it is =3D
when you pull it about, just take a piece of clay gripped between your =3D
fingers, dangle it downwards and gently swing it back and forth and =3D
watch it fracture.
happy potting Marek http://www.moley.uk.com
Tom Wirt/Betsy Price on sat 21 apr 01
Hi Marek....
>>>throwing water does not disappear, it is used as a lubricant and
yes it does become incorporated into the clay,
Yes, I think we'er agreeing here. But it goes into the clay. If you
were actually compressing the clay particles, pressing them closer
together, the water would have to come out, increasing the amount of
slurry, not decreasing it.
When one uses a rib, I think this does happen to some extent, but in
using fingers, the water seems to go in.
I just posted another theory to the list....I'll sure be interested in
anyone actually comes up with the truth on all this.
Tom
Marek & Pauline Drzazga-Donaldson on sat 21 apr 01
Dear Tom,=20
throwing water does not disappear, it is used as a lubricant and yes it =
does become incorporated into the clay, also clay may well be a solid =
but it is a malleable solid, and that is the whole point, when you =
compress the clay(when you are throwing on the wheel) it thins out =
(becomes closer) and the shape grows, its strength being derived from =
the clay being compressed (clay particles coming closer together) in =
particular ways. What happens to clay when you are rolling a coil, it =
results in a thinner, longer and stronger coil if is made correctly =
under compression.
Clay is a plastic material and is formed by compression.
Happy potting Marek http://www.moley.uk.com=20
Lee Love on thu 26 apr 01
----- Original Message -----
From: "Russel Fouts"
push down hard into a spinning pot...now that is compression. i never onc=
e saw
an s crack in japan. it is unheard of.
>
> You might also add that these ribs are THICK. I've seen Japanese
> throwers use ribs that look like they were cut from a 2x4.
The other thing they do with tsubo and platters both is punch the clay do=
wn in
the center with their fists. This certainly compresses the clay. I =
think
they do this primarily because their kick wheels have much less momentum =
than
ours and this gives you a head start on the centering and pulling up of t=
he
clay.
I've seen Hamada on film doing the same when throwing on his han=
dwheel
(talk about a low momentum wheel!). When throwing large, he would do th=
is to
the bottom and then add coils to make the shape taller. This is a big =
reason
for the liveliness of his pots. He didn't always try to hide where the =
clay
was joined together.
I've never seen "S" cracks here in Japan. But come to think of it, =
I have
never seen "S" cracks from unfooted pots off of the hump here either. =
It
might be the nature of clay that is not made from refined industrial mate=
rials.
--
Lee Love
Mashiko JAPAN Ikiru@kami.com
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