Vince Pitelka on fri 4 jun 04
> the big clay companies now have dozens of stoneware
> bodies. from cone 5-11.
> in fact, i think the next big push should be a cone 1-2 clay
> body for schools. no reason to push kilns and energy to
> cone 6 for the average kid pot. i fired the schools kilns to
> cone 2 for years.
Mel -
I agree with you completely about the cone 1-2 clay bodies. I call that
"low mid-range, and it is a sadly ignored firing range. It is easy on
kilns, and yet you can produce fairly dense, durable wares, with the same
range of color available in low-fire. It just requres developing a range of
glazes and claybodies for that firing range.
But regarding your comment about all the cone 5-11 claybodies, it should be
pointed out that for functional work, there is no such thing as a single
claybody that is appropriate for functional ware throughout such a wide
range. It is reasonable to expect a single claybody to perform in the cone
5-8 range, and another claybody to perform in the cone 8-11 range, but
impossible for one claybody to cover the cone 5-11 range if the intent is
durable, vitrified functional ware. At the lower end of that range, the
fired clay will be porous and weak, and at the upper range it will be
perilously close to warpage and bloating. Anyone who tries to sell such a
claybody for functional wares is delusional.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
mel jacobson on fri 4 jun 04
i think the world of clay is moving rapidly away
from simple terms like, earthenware, stoneware
and porcelain.
there are far too many categories now.
industry is now using the term...`white ware` or `sanitary
ware` to describe toilets, sinks etc. these clay
objects are no longer porcelain...in fact, perhaps never
were. they are white, they hold water, have tight
glazes in most cases.... and, then you add `space age`
clay and super conductivity, and what do you have?
like stoneware, what do you mean?
cone 5-6, cone 10. white, buff, red, brown.
vitrified? how about these new ice clays, where does
one stick them in the category. is it true porcelain? i
do not know. it can be debated. but, then, who cares?
i find it like throwing glass.
and, as jt abernathy has said many times...cone 6 clay
is not cone 10 clay. broad range means it does not work
anyplace correctly.
the big clay companies now have dozens of stoneware
bodies. from cone 5-11.
in fact, i think the next big push should be a cone 1-2 clay
body for schools. no reason to push kilns and energy to
cone 6 for the average kid pot. i fired the schools kilns to
cone 2 for years, but always had poor clay. earthenwares did
not make it, and stoneware was always under fired. but, the
students loved the pots. the re/cycled clay with added redart
was always the best. at least it came closest to vitrified stoneware.
clay is the potters life blood, and always, the most ignored
part of the craft. far too many people just buy it off the
shelf and hope for the best. this is not a slam, it is a fact.
and many do not have any control over their clay, or even have
a clue what it is. ron roy has preached this for years. we just
don't have a clue....and, no one is ready to tell us. secrets.
and, do clay companies hire dedicated professionals at high
salary to make clay? probably not. not a real easy job.
dirty, dusty, hot. i sure would not like the job, all day,
every day.
it is the reason i have pushed potters to buy pug mills. it is
getting more important to have some control over what is
in your clay. a number of fine potters such as wendt,
and a number of oregon potters are doing great work
with natural fluxing high fire whites. great translucency. but,
they are mining their own materials in some cases. it is
hard work, and dedicated work, but, they are getting what
they want. a real signature pot. there are even a couple
of potters in america other than malcolm that make a
decent shino. maybe 200. wait until you see the shino
show in baltimore. knock your socks off. and the show
in new york (2001) was not so shabby either...`american shino`
i believe it was called.
people often ask me why i put blocks of continental clay
stoneware fresh from the bag into my pug mill. well, i
have to re/make it. it has to become `my clay`. i add
stuff. it has be my `signature`. just the way it is.
i can afford factory made clay, i just choose not to use
it as is. in fact, i often pick up scrap clay from dock six pottery
and use it as a re/cycle base. i am going to soak it for
weeks anyway in water, why not use what they throw
away? helps them, helps me.
well, one can debate what is porcelain for months, it does
not matter. each clay body has a `character`. you must
find the one that matches you. or what clay is `yours`.
mel
From:
Minnetonka, Minnesota, U.S.A.
web site: my.pclink.com/~melpots
or try: http://www.pclink.com/melpots
new/ http://www.rid-a-tick.com
Ron Roy on sun 6 jun 04
Vince said -....... It is reasonable to expect a single claybody to perform
in the cone
>5-8 range, and another claybody to perform in the cone 8-11 range, .......
I can't agree with this statement -
Tuckers sells clay for cone 6 and cone 8 - I can assure you that firing the
cone 8 clay at cone 6 will result in leaky pots.
Perhaps some what off subject - firing the Red Art based cone 8 body
(designed for oxidation) at cone 10 reduction would be a disaster.
If we could count on our raw materials being the same each time then perhaps.
The bodies I monitor for Tuckers and Axner are recommended for one single
cone - to be sure they will hold water.
I'm sure they are not all fired at the same cone by everyone but - I would
never recommend a lower cone than that specified. I would recommend that I
adjust the body to melt more.
I see the absorption and shrinkage test data for every batch of clay made
at Tuckers - it is not uncommon to see the absorption numbers change once
in a while - it all depends on the variability the raw materials.
There are still lots of bodies being mixed with only a few clays in them -
these types of bodies are particularly susceptible to swings in
refractoriness.
So - even if the clay maker is testing each body - and raw materials -
there is a time lag. This means clay is often mixed, sold and used before
the test results are know.
If a clay company sells clays that are designed for multiple end
temperatures - should it not be incumbent on that company to report the
absorption and shrinkage at each temperature?
In the end - if a clay is recommended for different end firings then it is
necessary for each batch to be tested before use - if not by the mixer -
then by the potter.
RR
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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