James Freeman on thu 18 feb 10
I received another email from our soil scientist this afternoon. He was at
a meeting yesterday with three soil chemists, and happened to mention my
question about vinegar and flocculation, and also a follow up question I
asked about the effect of vinegar and urine on the plasticity (workability)
of a clay body. In addition to the material I shared previously regarding
flocculation, they provided good information about some other ways that bot=
h
vinegar and urine could contribute to plasticity of the clay body, and I
thought I would share that information too, for anyone who is interested.
Here it is verbatim:
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D
After reading your explanation on workability, you are using the word more
as we would think of plasticity; i.e., the stickiness/cohesiveness of clay.
A couple of additional thoughts to hypothesize about the clay behaviors tha=
t
you describe:
If the potting clay (kaolin, ball clay, fire clay and feldspar/silica) has
protein or organic impurities, lowering the pH with acetic acid should
precipitate out the protein and may thicken the clay.
Lowering the pH with acetic acid may solubilize some of the Al (or Si at
lower pH) and result in aluminum gels that could thicken the clay.
If the potting clay has some expandable clay minerals (such as smectite (fo=
r
example, montmorillonite)) as impurities (where water can enter between
adjacent layers), aging the moist clay could allow a thickening to occur as
the clay swells. This effect would depend especially on how dry the clay
was initially and whether there was any sodium in the system. The drier it
was and the more sodium present, the more likely it would be to swell.
You mentioned bacteria. Many bacteria produce rather extensive
extracellular polysaccrhides (gums or gels) that could be thickening the
clay. In fact, the acetate could be serving as an energy source for the
bacteria. (But if the thickening happens quickly....within a few minutes,
this is not the cause of the thickening. It would take the bacteria severa=
l
hours to a few days to grow.)
Urine would certainly change the ionic strength of the water in the clay,
and the urea in urine might serve as an N source for bacteria (assuming
there are carbonaceous materials in the clay the bacteria can use for
energy).
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D
In order to raise the above hypotheses to the level of theory, one would
have to conduct fairly extensive experimentation. In their words, "One
would need to do some research in pure systems where the numerous variables
mentioned above could be controlled and found important or eliminated."
I know I said before that I was done with this topic, but I didn't want to
keep this information to myself. Personally, I have no intention of peeing
in my clay no matter what the benefits, but I won't judge anyone who wishes
to. I also won't shake their clay covered hand, at least not until I have
seen them wash them at least 10 times! As an aside, I found it quite
refreshing that these highly trained, technically oriented PhD chemists and
scientists were able to explain these concepts to us laymen in very simple
language that we can all understand, without ever resorting to pages of
jargon.
Lastly, please, please, please do not argue with ME about this stuff. Thes=
e
are not my ideas. I am merely the messenger, sharing the ideas of several
real-life soil scientists and soil chemists. Accept it or don't, as you
will. Post competing hypotheses as you will. Now I really am done (unless
they come back to me with more good information!).
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/
May Luk on fri 19 feb 10
Thanks to James and Marian, the thinking potters, who wouldn't let it
go and keep on the argument.
What is the fun if everyday is perfect firing and winning awards.
May
--
http://twitter.com/MayLuk
Lee Love on fri 19 feb 10
On Thu, Feb 18, 2010 at 7:34 PM, James Freeman
wrote:
> In order to raise the above hypotheses to the level of theory, one >would=
=3D
have to conduct fairly extensive experimentation.
I said that in far fewer words. ;^) The oldtimers know that
nothing replaces testing.
--
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 fri 19 feb 10
James, your soil scientists did not mention complexation and ligand
bonding with the acetic acid providing the ligands. Chelation and
other terms and processes are related. These days the whole concept is
so well studied that different branches and names arise for different
organic acids and other substances that make this type of bonding and
linkage possible. Much has been written about this by soil scientists,
physical chemists, organic chemists, environmental scientists, medical
researchers, biologists, geochemists, etc., over the years, especially
in modern texts and publications. Entire chapters of texts are devoted
to organic acids and their reactions, under which vinegar is
classified. Kim Tan has a fairly easy to read soil chemistry text that
covers this. The effects are immediate and the strength imparted to
either a clay body network or a glaze system go far beyond that
accomplished by water bonds alone and spin-off effects are numerous
and varied. In a glaze, flocs are helped to stay in suspension by
complexes formed through ligand-type bonding. The net result is
stronger bonding and cross-linking between clay body plastic and
non-plastic particles and the water in the system; this appears to us
as thickening glazes or increased workability in clay bodies. Ligands
were common topics back when I went to school and this field has
mushroomed as test methods have improved. Basic ligand theory serves
to unify certain scientific branches and contributes to shared
understanding among scientists.
To talk about science it is impossible not to communicate using what
you derisively refer to as jargon. It would be like asking clay
workers never to use the language commonly employed in our field. In
studio pottery and in the ceramic industry a goodly number of
"scientific" terms are used and understood by us all regardless of
educational level. Potters are all smart and inquisitive; I don't know
why you don't give us all more credit. Jargon -- what an odd thing to
get all picky about. Whatever. Sharing and chatting among members has
gone out the window and you seem to have put yourself in charge of
list member "education" -- go for it.
Here is a "primer" (author's word) from one of our modern geochemists:
http://ag.udel.edu/soilchem/Casey03RevGeo.pdf
It hints at the complexity involved and makes me feel grateful and
humble regarding those who do know far more than me and are willing to
teach and share without regard to personalities.
Have fun, I'm off into deep, deep lurk mode. I've got things to learn
on my own and my craft work to improve.
Marian
Neon-Cat
ivor & olive lewis on sat 20 feb 10
Dear James Freeman,
Nothing wrong with the plausibility of the ideas put forward by you
favourite soil scientists. I like to see the black and green moulds that
grow in the dark on my porcelain. Throws like a dream after twelve or so
months if I can prevent it from drying out.
Regards,
Ivor
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