mea rhee on sun 30 oct 05

Elizabeth Hunt on sun 30 oct 05

> on one of them did I find that there was a circumferential crack half
> way across the sloping cut surface.

Hi Mea,

I don't have the physics explanations. Way over my head...Ivor would be much
better in that department, but I also took Joyce Michaud's workshop and have
been implementing her techniques. The problem you had might have been with
the "sloping cut surface." When you "undercut," you aren't actually cutting
any clay away, but rather, compressing the clay inward into and across the
bottom. Sometimes I do this with just a finger, sometimes with a 45 degree
angle tool held flush with the bottom of the pot and gradually turned
inward, making a 45 degree-ish undercut without actually removing any clay
that would mess up the structure of the nicely aligned clay particles. After
making the outside undercut, make an undercut in the inside wall where it
meets the floor. Also, like Ivor was saying, clay wants to move in the
direction of the highest point. So when you recenter your rim, compress it
at an angle so that the inside edge of the rim is higher than the outside
edge and this will help the clay move upward and not outward. Hope this
makes sense!:)

Elizabeth Hunt

steve graber on sun 30 oct 05

mea rhee, if i understand you right, i throw taller the same way - but i never heard it called "undercut the buttress". for me it's a finger notch at the wheel head. this gives me a good place to capture the clay for the next lift. and i don't have to cut my index finger nail very often. drag your finger on the wheel head before every lift.

while in pottery it's called a "lift", to me it makes more sense to think of it as the begining of an extrusion. the clay is squeezed between the outside & inside fingers. beginers often leave a blob of clay at the wheel head & wonder why they can't throw taller. get that clay at the wheel head base into the cylinder & you'll throw taller.

i use a finger notch most every lift to get height. on 10 to 20 pounds i use my whole hand (the karate chop type of palm) to get that lift going. after every pull i do a tight collaring to get the diameter of the cylinder back smaller again. i get up to my arm pit this way. if i had longer arms i think i could throw taller still...

see ya

steve



mea rhee wrote:
Ivor Lewis wrote:

<<
You said in a recent post>

buttress. There's a long physics-based explanation for this, but the
short explanation is the clay wants to move towards the buttress, as in
down and out. >>

I would dearly like to read the physics based explanation.

I tried this some years ago with some 30 inch wine jars, as much as
anything to trim the pot because I knew I would not be able to invert it
and stand it on its neck to trim the base. Went through the kiln in a
cone 8 plus salt glaze firing. Not until I came to test the spigot tap
on one of them did I find that there was a circumferential crack half
way across the sloping cut surface.

As I said, I would appreciate the information if you would be willing to
provide it..

Best regards,

Ivor Lewis.
Redhill,
South Australia.>>>



Dear Ivor,

I wish I could explain it further, I honestly do not have the words.
When I was taught this technique, it came with a lengthy explanation
that made sense at the time, but I have long since forgotten. Now I
understand it with my hands better than my brain.

Anyhow, when I undercut a buttress, I do this very early in the
throwing process, only to help me produce the tallest cylinder
possible. Once I've reached a good height, I begin shaping and I don't
undercut anymore. It sounds like you were undercutting to finish your
form, not to start. I think we might be discussing two separate
techniques.

Again, I wish I could be more helpful. Perhaps the entire clayart group
could shed more light.

Happy potting!

Mea

_______________
mea rhee
good elephant pottery
www.goodelephant.com

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