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nceca (clay aging for pamela) - dr. carty's mentions...

updated wed 28 mar 07


pdp1@EARTHLINK.NET on tue 27 mar 07

Hi Dr. Carty,

Thank you for writing to our List.

Discussions are valued, as is the patience or forebearance to have them.

I hope your presence and participation will in fact be at-least that of an
occasional contributor-poster here...if not more.

The broader matter of Clays and their properties, and one's practices and
understandings of practices, are of course of central
interest to many...even if only of incidental or weak interest to others.

Exemplars of meritorious 'Studys', practical insights, reliable practices,
Historical research,
and respect for a
subject, likewise are valued.

Below...amid...some additional amble...

> ----- Original Message -----
> From: "Carty, William M"
> To whom it may concern:
> I gave a presentation at NCECA in Louisville on clay and bodies. (Yes,
> I am the infamous Dr. Carty, although I never refer to myself that way.
> I am "Bill" to my friends and all the artists I interact with.) I also
> made comments on aging clays. I believe on the ClayArt discussion site
> however, my comments have been taken out of context. (I can't tell from
> the discussion if Phil was present, but he seems rather angry -- and I
> checked, I am using the word myth or mythology correctly according to
> Merriam-Webster's Collegiate Dictionary. I can elaborate if necessary.)


No, I was not 'there'...I had other obliges.

No, I was not angry, just lightly bemused, scandalized, and what for me is
mildly curmudgeonly.

No big deal...

...and yes, please, elaborate on the rationalle for the use in this
context, of the term "myth"...or, how it is that some hear-say
purportation about some
supposed Chinamen, is to be elevated to the emotionally charged status of
'Myth', or, hyped to such status, to hype the 'bust' or 'buster' it will be

Bear in mind too, if you will, I felt scandalized at how awefully bad the
quality information seemed to me to be, and still seems to be, and, I was
to what at-the-time, was the hear-say, which has since been substantiated
in your missive below, in which some supposed
( and extrordinarily narrow, abstract, and bearing no relation in any way to
the supposed "Myth" it is then supposed to 'bust', of )
'study' was being mentioned, along with it's conclusion, that 'Aging Clay
does not improve it'.

Yet, fifteen or twenty or more people have already commented on how their
own casual and
incidental methods of making almost no effort or practice at all for their
manner of 'aging' Clay, DOES in fact 'improve' their Clay...let alone
whatever unassayed practices, lost to the shifting Sands of time and
passage, and never preserved in the first place, were done, or may be done
yet, to 'improve' it.

So, how can you stand behind such a statement?

How can you, and why would you, make such a statement in the first place?

Let alone why base it on a
'study' which was no study at all, unless watching something do nothing,
that one has done nothing to, IS
a 'study' of how it does and will do nothing? And which replicated no
practical or
intentional method in any way, anyway?

You say you have "busted a Myth" of Clay being improved by aging.

Only you never undertook TO age any Clay in an intelligent or practical
or deferential manner...nor according to anyone's tradition or practice of
doing so...whatever pathetically little is even imagined to be believed
about anyone's lost and forgotten practices.

There is hardly anything
known ABOUT what practioners used to do, or far less than 'we' know per-se
some partial snippet of hear-say somehow carried on down through decades or
centuries, how they made their ( guarded secrets OF ) Glazes or got them to

But while Glazes of old Pots might be reverse engineered by Scientific Study
and experiement, or guessed at by known modern examples they may
resemble, practices of 'aging' Clay done hundreds or thousands of years
ago, are likely not so 'easy' to examine, nor did these methods necessarily
find preservation in hear-say to be repeated however so centurys later.

When one makes "Wine' one does rather more than JUST to buy a Jar of Grape
Juice, keep it in the Jar, then excalaim how 'Wine' is a "Myth" when it has
done nothing but remain Grapejuice.

Unless one imagines that "that" WAS all one was supposed to 'do'.



There is nore to it.

Were their Glazing practices and ingredients and finess of it an open book
too? Preserved for you to 'bust'? Just like forgotten regional, specific,
actual practices of forgotton
peoples' means of Clay 'aging' practices?

You never used a Natural Clay, you only used some bag of clay from a
which had Chlorine residuals, or is suspected of it at any rate...and was
semi-hard when you you got it, semi-hard when you opened the bag...semi-hard
as it sat, and semi-hard when
the 'study' concluded it was still the 'same' semi-hard inert material you
had started with, or whatever.

You never Took a Natural Clay 'sample', tested it's Throw-ability "as found"
, or by having done to it whatever extempores that may have been needed TO
"Throw" it, 'as' a Test...
and then never did any of the things old impirical practioners did or might
have done
'aged' order to age it intentionally, properly, according TO the
kind of particular Clay it is and the particulars they found would work for
the result being effected positively WITH "that" Clay AS "that" Clay in

You never watered the Clay down into a thin 'Soup', useing Well Water or
Artesian Water, or Cistern Water or
Brackish Water of some kind to make a thin 'Soup' of it, exposed it's
shallow depth and possibly broad surface to the ambient did not
add any ground-fallen rotting Fruits,
rotting Leaves, fine detritis, lots of everyone's did not add
urine, animal
intestines, did not permit or invite wind blown ambience
of 'dusts' or as may be, or anything to include or invite ( yes, by then,
additional if not symphonys of ) Bacterias, Enzymes, Proteans, Anaerobes,
Molds, Yeasts, Nematode husks, Pollens etc...agitate the whole to distribute
things toward some homgenuity of these "added" ingrediants'

... cover it
and let it sit a
two-month or four month or something, a year or so even, and THEN let the
Water evaporate 'down' to approach some order
of Throw-ability...dig some out, mix and blunge or let it dry some more just
as itself on some stones or semi-absorbant flats, wedge "that" and "test" it
"then" if
one were serious about the
'study' or the
experiment, and in earnest TO try and learn or "prove" in practical terms,
honestly, for real, at least SOME possibilities 'positively' of what some of
the old
practioners maybe
did 'do'...or to see what doing something DOES 'do'.

You just dismissed all of it perfunctorily, religated some part of some
mundane 'story' about some supposed Chinamen burying Clay to age it, (
"buried it how? Did what to it first? Buried in in what kind of Soil? What
sort of Soill drainage? What Flora grew on the surface of that Soil? What
Bacteria and Anaerobes in that Soil? - and on
and on and on and on...) ...

....and you take that one aspect of some Cinamen said-to-have 'buried' it,
to a
status of
"Myth!"...and...letting a bag-of-clay sit as a bag of clay, never even
wedging it, which stayed an unwedged bag-of-clay, then you
say you busted the 'Myth'.

..did the Chinamen let a bag-of-clay from a supplier 'sit' just like you
did? For your replication OF "method" to be faithful?


So, I felt might term it...and I commented. summary - redundantly even...

You exclaim appearently, that because YOU feel that you heard some revealing
snippet or quote or hear-say written who knows when, which is supposed to be
at most,
some partial or incomplete element of the supposed or purported practices
of some old Chineese, dealing with one kind of local Clay,
but is likely far, far from the whole OF their practice, but hearing
that some
of them buried their Clay
for a while as maybe merely one aspect of some aging process, ( let alone
whatever fragments of rumor or hear-say remain or do not remain, of any
other people's
practices, with their local Clays, as if their closely guarded practices
WOULD be preserved by
hear-say hundreds or thousands of years later, you decide
there is nothing to it, and you "BUST" the attributed-by-you 'Myth' by not
even doing "that' at all anyway, not even doing anything like what 'they'
were said to do in the one "myth" you elected TO 'bust', but by doing
something totally different which did nothing to effect the Clay in any
way...then you exclaim that the Clay was not effected...and claim to have
'Busted a Myth'.

There are endless thousands of various Clays having differing properties and
propensities and Cones' ranges for being made into something which can be
called "Fired". They will of course differ in their as-dug qualities for
being Thrown.

There are endless differences which their treatment, or potential processing
and aging AFTER processing variously, might make.

It makes no sense to me to take one sample, of a bagged Chlorine residue
permiated Clay, and do nothing with it, and then, to say that no Clay
of any kind, ever, now or in the past, would be "improved" by 'aging', when
the very term 'aging' itself is not in any way used to mean anything at all
BUT to let a specific bagged Clay 'sit' in the bag.

I found this objectionable.

And in my own way, I said so...and I say so still.

If I have misunderstood something here, or misunderstood what you did say
and did do, please, clear this up?

Best wishes,

Las Vegas

> Also, however, I believe it is really important for all of you to
> realize that the talks were not about aging! The question about aging
> came up in the short question and answer period at the end of talk and
> was just briefly addressed. If this is really of interest, and it may
> be, I would be happy to address aging at some future date. David Pier
> talked about things of importance to artists with regards to clay
> bodies. Matt addressed the importance of particle size on workability
> of clay bodies -- and yes, he had a fair number of great electron
> microscope images of clays and feldspars. And I talked about how the
> bodies fire and also touched, briefly, on the importance of mixing from
> observations on slumping. We did not address aging in our talks so you
> will likely be disappointed when the NCECA publication comes out.
> While I am not an artist (nor technically a scientist -- my background
> is ceramic engineering), I have worked with artists for roughly 20 years
> answering, to the best of my ability, questions regarding ceramics.
> Over time, too, my answers have sometimes changed based on observations.
> In all cases, I weigh the question and decide how to best answer the
> question. I have never disputed that artists may be able to feel
> differences that we are unable to measure, but my observations, and
> particularly those regarding aging and clay, have typically been tested
> and evaluated by artists. To all who know me, know that I am hands-on

> and eagerly enter into discussion on the way that things behave --
> particularly clays.
> Artists and industrial types pay a lot of attention to aging. As a
> result of both interactions with industry and with artists, we have
> evaluated aging from an experimental perspective. For this discussion,
> I believe it is necessary to define aging as change in behavior until
> steady-state is achieved. In other words, the clay may change with time
> until it stops changing. We (my research group and the Whiteware
> Research Center) have always been interested in measuring behavior, but
> more importantly, in mechanisms. We are much more interested in WHY
> something happens, rather than WHAT happens. From the perspective of
> why, we can help to understand better how to control the behavior or to
> compensate for changes in behavior. That seems to be something that
> artists find valuable.
> The common misperception (myth?) is that clay "ages" due to bacteria
> growth. I believe this was likely true 75 years ago or longer, but not
> for modern clay. While articles on aging have all but disappeared from
> recent literature (at least for industrial clay discussions), they were
> somewhat common up to the 1940s. I recall several articles specifically
> that grew bacteria in clay during the 1920s. The problem, however, is
> that it was not possible to explain why in some cases the clay would
> become easier to work and sometimes harder. The change in clay
> workability did not seem to be connected to bacteria growth based on the
> discussions in these articles, and frankly, the workability discussions
> were a bit vague. But that is not surprising, however, because the goal
> of article was to address bacteria growth.
> The mythology associated with ancient Chinese potters is that they would
> bury their clay in the ground for their grandchildren to allow the clay
> to age and have the best workability. This may have been true at one
> point, perhaps several hundred years ago, but does not seem to be the
> case any longer. Clay is produced in China much the same way as it is
> produced here in the U.S.: raw materials are mined, ground, mixed with
> water, worked into a plastic mass, then used. The mass production
> system does not really have mechanisms that allow for clay to be stored
> for months, let alone years, before use. I believe that is also true of
> artists in the U.S. Clay is purchased for use. Few artists have the
> storage capacity to keep enough clay to last for years of work. Typical
> clay storage is less than one year (based on a limited sampling of
> artists I know that I asked, but it make sense).
> Clay does age, but this aging, based on our observations (and a large
> amount of research and experimentation) is due to raw material
> dissolution and an increase in dissolved salts or ions. In a well mixed
> clay, this process is complete within a day or two at the most. The
> clay does not continue to dissolve with time due to the achievement of a
> sort of equilibrium or steady-state in the water chemistry. Of course,
> if the clay is poorly mixed, this process may take considerably longer,
> but the process is still likely done in less than a week.
> Furthermore, and perhaps most importantly, if the clay is obtained from
> a commercial vendor, and from my experience a vast majority of the clay
> used by artists comes from commercial clay suppliers, it has a limited
> window for aging. Whether the clay is purchased as a raw material from
> a supplier (such as Zemex or Unimin, etc.) or as a mixed body (such as
> from Laguna, or Trinity, etc.) then the clay is not likely be a good
> candidate medium for bacteria growth. There are two reasons, but one is
> sufficient: The clay has been mixed with tap water. Tab water
> typically contains, if nothing else, chlorine -- and chlorine kills
> bacteria. It is as simple as that. I have also been told that
> commercial clays contain an anti-bacterial agent, but have not verified
> this.
> The second reason is a practical one. A box clay, bought from a
> supplier or from a distribution retailer is of indefinite age, but it is
> quite unlikely that the clay will have set, in the box, for less than
> one week when the artist receives it. The clay body cannot be
> reasonably batched, mixed, extruded, boxed, and shipped in less than one
> week. It is likely considerably longer than that for the simple reason
> that these companies produce more than one or two bodies. Twenty bodies
> is more likely the case. It costs money to change the recipe, with mill
> clean-out, changing recipes, etc. The clay suppliers make as much clay
> as the market will bear at one time -- typically at least a few tons of
> clay. This clay then sits in a warehouse waiting to be shipped, or in
> the distributor warehouse waiting to be bought. Therefore, I would be
> surprised if the clay changes at all once in the hands of the potter or
> artist.
> In industry, however, things are different. Clay is produced in-house
> and it can get into the process immediately. Assuming that my argument
> that it takes a day for things to equilibrate (age if you like), this
> clay may appear to be different and changing in the industrial process.
> In these situations, it is possible that the clay will be changing,
> aging if you like, producing a non-uniform behavior with time. This
> problem shows up as increased loss rates for the simple matter that
> machines are unable to compensate for changes in the clay. If the clay
> is allowed to set, in the plastic state, even for only a day, these
> variations or changes are unnoticeable.
> That said, if an artist digs clay from a river bed and used the river
> water to mix the clay, then yes, aging due to bacteria is quite
> possible. Also, if you mix your clay using beer instead of water, that
> may be similarly true. However, again, if mixed using tap water, aging
> due to bacteria growth is quite unlikely. Note also though that not all
> tap water is the same. If an artist moves to a new location, changes in
> the water chemistry can cause changes in the workability and behavior of
> the clay.
> The fact is that aging for artists should not be a great problem.
> Changes that are seen could be due to several things, drying, changes in
> humidity, temperature of the clay, etc. However, I don't believe that
> aging is really an issue.
> Feel free to email me with questions. I will respond as quickly as I
> can.
> Cheers.
> Bill Carty
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