Vince Pitelka on sun 26 jun 05
Eric -
I think that ultimately the strength of the wet clay wall with any
particular claybody is primarily a matter of moisture content. In
compressing the wall with a rib, especially a metal rib, you can lift off a
great deal of moisture in the form of slurry, and thus restore more
structural integrity to the wall. On the other hand, a pot thrown quickly
with dominant throwing ridges has not had the opportunity to absorb much
moisture, and thus the walls are quite strong. That is why it is important
to learn to throw fast - it is not a matter of production efficiency - it
just means that less water is absorbed and thus you can get the clay to do
what you want it to do.
I frequently use ribs to remove moisture and restore structural integrity.
A good example is on large bottle or jug forms with a broad swelling
shoulder. Before necking in the rim, it is often helpful to remove some
moisture from the upper shoulder with ribs. That reduces the likelihood of
buckling or sagging just below the rim. Another example is in a large
platter with a wide flange rim. After widening the bottom to the width you
desire, the rim is raised with an outward flare, but if you bring the wet
flange down anywhere near horizontal, you risk having it collapse abruptly.
Instead, if you work the clay inside and out with metal ribs, removing
significant amounts of slurry, it restores the structural integrity, and you
can then lay the flange rim as level as you wish.
- 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/
Jo Smith on mon 27 jun 05
Vince,
Do you use two ribs at the same time (one inside and one outside) or rib the
outside then the inside? Sounds like something to try...Jo
>
> I frequently use ribs to remove moisture and restore structural integrity.
> A good example is on large bottle or jug forms with a broad swelling
> shoulder. Before necking in the rim, it is often helpful to remove some
> moisture from the upper shoulder with ribs. That reduces the likelihood
of
> buckling or sagging just below the rim. Another example is in a large
> platter with a wide flange rim. After widening the bottom to the width
you
> desire, the rim is raised with an outward flare, but if you bring the wet
> flange down anywhere near horizontal, you risk having it collapse
abruptly.
> Instead, if you work the clay inside and out with metal ribs, removing
> significant amounts of slurry, it restores the structural integrity, and
you
> can then lay the flange rim as level as you wish.
> - 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/
>
>
Jean Cochran on mon 27 jun 05
Dear Jo,
You didn't ask me this question, but I still thought I'd pass my experience
along to you.
At the very beginning of my learning to throw (I taught myself out of a book
"Charles Count's Pottery Workshop"), I decided to throw with two metal ribs.
The one inside flipped in the clay and cut my finger very deeply. I
developed "yellow-stripe-down-the-back chicken" syndrome and have never
repeated the test.
Jean Wadsworth Cochran
www.foxhollowpottery.com
www.kycraft.ky.gov/craftcgi-bin/index.cgi?busid=186
Vince,
Do you use two ribs at the same time (one inside and one outside) or rib the
outside then the inside? Sounds like something to try...Jo"
Vince Pitelka on mon 27 jun 05
> Do you use two ribs at the same time (one inside and one outside) or rib
> the
> outside then the inside? Sounds like something to try...Jo
Jo -
Angela Fina stretches her porcelain Ikebana forms by using two metal ribs
simultaneously, but I have generally done one side at a time, while
providing gentle pressure to the other side with the flat surfaces of my
fingers. It doesn't take much pressure with the rib to remove a lot of
slurry, so it also doesn't take much pressure with the fingers on the
opposite surface.
- 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/
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