Jess McKenzie on sat 17 oct 09
This is my open apology to Vince, whom I probably offended
with that last sassy question on flocculation, etc.
If that's the case, I'm deeply sorry. For it was Vince who
graciously responded--before we joined the List--to our
questions about pottery and our request for instructions on
how to join Clayart.
Thus, we don't bite the hand that feeds--offense was certainly
not our intention.
With years of experience in laboratory science and no ceramics
background, I was surprised to see lots of familiar terms used
on Clayart. I assumed these terms meant the same to you folks
as they do to me. Some of them, certainly those used by Ron
Roy and John Hesselberth, were obviously the same. Their fine
book, "Mastering Cone 6 Glazes," was an eye-opener, btw.
But some terms used on the List, like "flocculation" and "de-
flocculation," seemed unclear. Different folks used the terms
in different ways, some in the context of physical chemistry--
which was comforting to me--but others used the terms in
"fuzzier" ways.
Then a few people mentioned the need for defining terms. That
encouraged me to send in msgs about the subject. I tried to
be subtle, hoping to provoke a real discussion on the subject.
Too subtle, I guess. No one responded to those msgs, not
directly anyway. People on one side tried to snow those on
the other side, and *those* folks just seemed to bow their
backs, refusing to respond in any understandable way.
Now, from the "other" side, we have Vince's answer (below). I
am satisfied, and I don't intend to pursue the subject
further. From now on, like Sofia, I will "lurk," reading
carefully all the msgs related to making pots, but I'll avoid
the polemics. I've no time for anything else. In three
years, I'll be 80. I'm old and in a hurry, determined to
learn to throw before that birthday.
Sorry, Vince.
~jess
Vince Pitelka
wrote:
This will be my last post on this subject. When we add a
little
vinegar to a thixotropic claybody, it becomes plastic and
workable.
If we add Epsom salts when mixing a claybody that contains a
soda
spar, it takes longer before the spar releases enough soluble
alkali
to cause the claybody to become thixotropic. When we add
vinegar to a
claybody, it makes the clay "stickier" and more structurally
stable,
as if the particles are attracting one another and thus
increasing
contact friction. Adding vinegar or Epsom salts seems to have
an
effect very similar to what happens when you add a flocculant
to a
slip. When we add a soluble alkali to a workable claybody, it
becomes
unworkable and thixotropic, as if the particles are repelling
one
another and thus the water layers between particles are
maximized and
the friction that provides structural stability is reduced.
Adding an
alkali to a claybody seems to have an effect very similar to
what
happens when you add a deflocculant to a slip. For over a
decade we
have been referring to these processes in clay as flocculation
and
deflocculation, for the simple reason that the behavior is
virtually
identical to what happens with a true water suspension. That
still
works fine for me. Marian, you are correct that I support the
correct
use of ceramic terminology, and when someone proves to me that
the
terms flocculation and deflocculation are not applicable to
these
phenomena in claybodies, and offers me a set of more accurate
terms, I
will be glad to "correct" my usage. Until then, I see no
reason why we
should not continue to use the terms "flocculation" and
"deflocculation" in regard to claybodies when we all
understand
clearly what we are talking about in the usage of these terms.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Lee Love on sat 17 oct 09
Easy way to remember: flocculation =3D3D flock, to bunch up like a flock =
of=3D
sheep
deflocculation =3D3D deflock, to disperse the flock, make the sheep scatter=
.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97tha=
t is, "T=3D
he
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
marci and rex on mon 19 oct 09
At 07:34 AM 10/19/2009, Luke Nealey wrote:
>their is somewhat of an anti-science bias in what gets posted(what is sent=
,
>not that science is ever excludued by mel) and especially what gets
>discussed.
I wonder if that could be because there are a lot
of uneducated shlubbs like me who learned what they know by
the seat of their pants and by just jumping in and seeing what
happens.. I know Im not the only one out there who has
not taken clay ( or art ) in college... or even high school,
for that matter and I will shamelessly admit that
I slept through Chemistry and physics class and wouldnt know a
trivalent cation if it said Hello and offered to buy me lunch !
I try to hang in on these discussions ( while trying
to keep my brains from leaking out of my ears) but they
may as well be in Japanese.
If its the shlubbs like me that do most of
the asking for help, that could explain why there seems to be
an anti-science bias.
But keep it coming, guys. Im hoping it'll sink it someday . :O)
marci
www.ppio.com
Luke Nealey on mon 19 oct 09
Jess wrote:
> Different folks used the terms
> in different ways, some in the context of physical chemistry--
> which was comforting to me--but others used the terms in
> "fuzzier" ways.
>
> Then a few people mentioned the need for defining terms. That
> encouraged me to send in msgs about the subject. I tried to
> be subtle, hoping to provoke a real discussion on the subject.
> Too subtle, I guess. No one responded to those msgs, not
> directly anyway.
Jess:
As a rare poster and person of scienctific training and experience I have
found over the years I have read clayart on pretty much a daily basis that
their is somewhat of an anti-science bias in what gets posted(what is sent,
not that science is ever excludued by mel) and especially what gets
discussed. I remeber a discussion of what is actually happening in a wood
fired kiln. I sent a link to a great, albeit 70 page article, from the
Forest Products lab. Zero response. It seemed to me that the folks on the
list would rather wave hands and speculate than discuss data.
I love clayart and would never have been able to do the few things a am abl=
e
to do in the pottery piece of my life without it. There are great steady
data-based, scientific article/experimenters oriented folks on this list
like Ivor and John H. Don't stop contributing or participating, it is what
it is and rarely does anyone seem to get their feelings hurt too badly.
And sometimes Mel writes nice things about those of us that aren't full out
potters but may occasionally have something relevant to say.
Regards
Luke Nealey
Rankin County MS
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