Lee Love on tue 16 feb 10
James, you really think Marion is bullying Ron and Vince? Bullying
Vince? LOL
On Tue, Feb 16, 2010 at 4:01 PM, James Freeman
wrote:
> the field, and accept that vinegar can and does act as a flocculant.
Household vinegar is diluted and is a weak household acid (usually
about 5% acidic acid for table vinegar and 18% for pickling vinegar.
Probably most people use table vinegar. That's all I have in my
house.) Our strongest household acid is lime juice.
I suppose the best way to know what pH change is made is to run
the tests on the pH of glaze that has vinegar put in it. Isn't that
what scientifically minded Marion is asking?
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
Neon-Cat on tue 16 feb 10
Dear James, if you read my posts from the last great vinegar debate
you'll see that nothing I wrote contradicts your soil scientist at
all. We are, may I remind you, dealing with vinegar, a very dilute
form of acetic acid in rather limited pH ranges in a solid solution
(the clay body). It is impossible in a clay body to aggregate already
hydrated and solvated kaolinite particles whose charge has already
been satisfied. And why is it most everyone seems to forget the entire
clay body - the quartz, feldspars, organic matter, tempers and grog,
and what-have-you? We wish to knit the entire mass of ingredients into
a clay body we are pleased to use, thus all this uproar over trying to
flocculate individual clay particles is rather a moot point once a
potter has a clay body in the studio.
I just got on-line since I posted and have some catching up to do
(snow, downed tree limbs and part of a fence). Yours is the first post
I've read besides one by Bill M. on Cannon fire. Cannon fire? I'm
intrigued.
Anyway, remember the recent mention of loaded or poorly-worded polls?
You can ask any expert if acetic acid will flocculate and the answer
will be as you got. Sometimes, under limited conditions. It can also,
maybe, deflocculate under some very special conditions. It is how we
as potters put knowledge to work that is at the heart of this search
for truth. Can acetic acid flocculate (in aqueous solution)? Yes, but
again -- sometimes. Can vinegar do what you're saying it will do for
us in a clay body for us clay workers? Slim to no chance and it is
almost never even needed. It can work to our benefit by another method
and that is what I had wanted to share with the list. Nothing more. No
big battles or warfare. It is interesting and will give you something
else to call and ask your experts about. It includes the whole of the
clay body, not just the clay portion and makes a whole heck of a lot
more sense that these poor models some have been following. More to
the point, it leaves a correct legacy of thought that might actually
lead studio potters into expanded concepts, not dead ends. I did give
the list the simple down-and-dirty idea of how they might determine if
their clay body was dispersive or not. I could share some simple test
equipment we could all own for about a hundred US dollars and
suppliers where we could get such testers that would tell someone if
dispersive clay was their problem.
The trouble with your line of reasoning is that it precludes proper
diagnosis of a clay body problem that needs correcting by insisting it
all boils down to flocculated or deflocculated particles in solid
solution. Your short-sighted view also precludes some of the wonder of
how vinegar might be useful to those who use and like it. I never
wrote that it might not improve certain clay bodies for those who want
to try it. Can a clay body be improved by other means ? Yes,
certainly, and without the negative draw-backs some folks encounter
when using vinegar. The historical record for all this hype about
vinegar and clay is largely the making of certain clayarters. People
can, have, and do make serviceable clay bodies they love without
resulting to parlor tricks, some of which involve vinegar.
I will now hopefully learn a little more about how others communicate
in this clayart list of ours as I play catch-up with the other posts.
Perhaps others are not all as close-minded as you, James, so anxious
to "win" a debate or score some point, no matter the truth or the
brakes you put on fruitful discussion that may evolve during
conversation. I am so flattered to have made your "to-be-attacked"
list because I am in good company but it does make me wonder about
your love of our craft and how you will leave the education in this
field for future generations. Keep reading your Wiki science and
putting up an isolated article you can't entirely comprehend -- it
makes no difference to me and changes no real science being pursued.
It does make me sad for our present understanding and for the future
of studio pottery. But potters are inventive and creative and will
always find a way to make pots and many will find they can do so quite
well without vinegar. Simple is good.
School is so much fun -- I learned of a potter (a woman!) here in my
area who actually does pee in her clay. For real. I guess she thinks
it does her clay body good.
(I am quite glad not to be her studio associate, but that's me)
Its mechanism is similar to how vinegar works.
Each to their own and all that jazz...but know why you are doing what
you are doing if you wish to persuade me of something. That is useful
knowledge to share and something to build on.
Marian
Neon-Cat
James Freeman on tue 16 feb 10
This topic came up several months ago when Vince and Ron, and probably many
others observed that vinegar (acetic acid) is a clay flocculant, and Marian
countered that it was not, and asked for a mechanism by which acetic acid
could possibly cause flocculation. This seemed to be a bit of a bullying
tactic, as she knew full well that while Vince and Ron's ideas came as a
result of actual observation of the flocculating effect occuring, neither
had the technical qualifications to explain the actual chemistry.
I offered up a peer reviewed article from a scholarly soil chemistry journa=
=3D
l
dated 1987 in which it was demonstrated that increasing acidity of clay
slops promoted flocculation of the clay particles. Marian dismissed this
scholarly study quite harshly based on it's date of publication (1987
apparently being the dark ages), and stated quite emphatically but without
substantiation that "soil scientists" no longer look at things that way.
Since many on the list and many who have authored respected ceramics texts
have observed the flocculating effects of acids, including acetic acid,
added to clay, I decided that, though I risked incurring Marian's wrath, th=
=3D
e
obvious solution to this problem was to ask an actual, real-life,
credentialed soil scientist. Simple. Actually, I asked the Soil Science
Society of America. They directed my inquiry to a real-life PhD soil
scientist with Iowa State University, who in turn consulted with a real-lif=
=3D
e
PhD soil chemist. What they told me was quite interesting, and does in fac=
=3D
t
support the idea of vinegar acting as a flocculant. Here is part of what
they said:
"Acetic acid is not normally thought of as a flocculant, but that doesn=3D9=
2t
necessarily mean that under appropriate conditions it won=3D92t cause clay
flocculation. There are several variables involved."
So, yes, acetic acid CAN flocculate clay. The fact that acetic acid is not
NORMALLY thought of as a flocculant does NOT mean that it is not one. They
went on to say that there are actually two different ways in which acetic
acid could cause clay to flocculate, depending on the amount added. Here i=
=3D
s
the first way:
"Let=3D92s assume that the clay you are working with is kaolinite. The
isoelectric point of kaolinite is approx. 4.5. So if the pH of the
suspension is lower than this, the clay should have a net positive charge,
and above pH 4.5 the clay should have a net negative charge (this has to do
with charges along the edges of the clay). The quantity of acetic acid
added is one variable =3D96 the more that is added to a constant volume of
suspension, the lower will be the pH. As pH goes down below 4.5, the net
charge on the clay edges become more and more positive. Some of that
positive charge will be =3D93balanced=3D94 by negatively charged acetate an=
ions=3D
. To
the extent that the positive charges are balanced by the acetate anions,
flocculation is more likely. To the extent that the charges are imbalanced =
=3D
=3D96
that is, to the extent that the edges carry lots of positive charge without
compensating negative charge from the acetate anions =3D96 it is more likel=
y
that the suspension will remain dispersed. In general, we=3D92d expect that=
a=3D
t
the lower the pH is below 4.5, the less likely is the suspension to
flocculate =3D96 the more likely it is to be dispersed.
So =3D96 it depends on how much acetic acid is added to the system and how
concentrated the kaolinite suspension is in the first place."
So, additions of acetic acid to the clay can indeed cause flocculation,
though further additions could reverse this effect. I suppose it would be
an easy enough thing for anyone who cared to measure the pH as we add
vinegar to see if we ever get the pH so low as to cause this reversal. To
date, no one on this list has reported witnessing this effect, so I would
assume we don't add that much.
They went on to describe the second mechanism by which acetic acid could
cause clay to flocculate:
"With the addition of much acetic acid, the pH may be lowered to where Al
and/or Si are partially solubilized. The Al or Si hydroxides formed may
indeed cause flocculation of the clays."
They concluded by stating that it was their opinion that the flocculation w=
=3D
e
witness is likely caused by a combination of the two mechanisms described
above, which mechanism predominates depending on the initial conditions of
our clay.
As before, I am only the messenger here, so attacking me changes nothing. =
=3D
I
offered a scholarly article stating that simple general acidity promotes
flocculation, and have now offered the words of a real soil scientist and a
real soil chemist (not a hobbyist or chemistry buff) describing the two
mechanisms by which acetic acid in particular can cause flocculation. Give=
=3D
n
this, I am personally done with this topic. Everyone is free to believe
whatever they wish. For me, I will accept the words of real scientists in
the field, and accept that vinegar can and does act as a flocculant.
All the best.
...James
James Freeman
"All I say is by way of discourse, and nothing by way of advice. I should
not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/clayart/
James Freeman on wed 17 feb 10
Thank you, Marian. You have responded in precisely the manner I
anticipated. You are attempting to obfuscate. You asked a simple question=
:
"Dear Vince,
Why are you so adamant that vinegar is a flocculant? Did you state
this in your book? In the many months and years this has been tossed
around on clayart have you come up with a mechanism for same?"
I have provided you with two, and possibly three mechanisms, all of which
came from PhD chemists, so your question has been answered. You said that
vinegar was not a flocculant. Three soil scientists (at least) have said
that it is. You are now trying to drag in a whole bunch of other stuff
that, while possible interesting or useful, is completely outside of and
irrelevant to the question you asked. A more open-minded and useful
response might have been "OK, so vinegar CAN sometimes be a flocculant, but
it can also be so much more. I suggest we explore some of the other
wonderful things it can do." Unfortunately, you chose the combative route
instead.
You claim that I asked the wrong question, so got the wrong answer, yet you
have no idea what I actually asked. Here is the actual question which I
asked, cut in toto from my original email to the scientists. As you can
see, it is precisely the question you said I should have asked:
"Is vinegar (acetic acid) a flocculant? Perhaps better stated, does the
addition of acetic acid to a clay body or slip promote flocculation?"
I also provided them with a list of precisely what ingredients beside clay
was in the slip or clay body:
"The slips and clay bodies we are interested in are typically a mixture of
kaolin and ball clay, and often a fire clay, with an addition of feldspar
and silica"
I have also been very clear in every post that these are NOT my theories or
models or conclusions, yet you insist on claiming they are mine, then
attacking me. As I stated, I am merely the messenger. By attacking me, yo=
u
do nothing to counter the argument.
I have no doubt whatsoever that vinegar can do any number of absolutely
wonderful things to clay beyond mere flocculation, and I think it is great
that you are trying to figure out what those things are and how they might
work. I have NEVER responded to any such thing, though you keep trying to
make it sound as though I have. I suppose it is a case of attacking the
messenger instead of attacking the message.
I suggest that it is you, not I, who attempts to close the door on debate
through your usual tactic of bombarding anyone with a differing view with
pages of chemistry-speak that you know full well is incomprehensible to mos=
t
of the list, in the hope that your target will simply walk away. While you
may or may not understand the jargon you post, it is clear that you use it
as a club rather than as a form of communication.
Finally, as to everything you wrote beginning with "I will now hopefully
learn a little more about how others communicate
in this clayart list of ours", I suggest you look in a mirror. Know too
that, contrary to your conclusion, I am NOT trying to convince you of
anything, as I know that to be quite impossible.
All the best.
...James
James Freeman
"All I say is by way of discourse, and nothing by way of advice. I should
not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/clayart/
Neon-Cat on fri 19 feb 10
James, clearly vinegar is getting so thread-worn there's no sense in
rehash. I=3D92m bored with it and have moved on. Obfuscation was never my
intent.
All this huff and puff of yours is not about science anyway.
I=3D92m going to trust that those who want to know something will be lead
to find just the correct answers they need here on this list or
elsewhere. Had I only known sooner that I need but dial out.
Meanwhile the giddy, refreshing talk of salads with lemon or vinegar
dressing sound mouth-watering good. Makes me wonder though just what
it is we=3D92re nurturing.
Marian
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