claybair on sun 28 jul 02
I seem to recall my early spouts turning clockwise.
I haven't had one twist in a while as I use a metal rib on
the outside while using a pencil or dowel inside as I pull up the spout.
My theory (which is mine) is that removing/smoothing the finger rings
eliminates the twisting.
Anne Elk oops... Gayle Bair
Bainbridge Island, WA
http://claybair.com
-----Original Message-----
From: Martin Howard
Sent: Sunday, July 28, 2002 12:04 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Twisting Spouts
I'm throwing and putting together a lot of teapots and trying to understand
the twisting of the spouts.
The books all seem to describe this phenomena as the firing of a spout
increasing the twisting in the same direction as the wheel was moving when
the spout was thrown.
So, looking at the spout with the handle of the pot furthest away from you,
and the wheel moving anti-clockwise as usual in the west, we should assume
that firing will cause the spout to twist a smidgeon further anti-clockwise,
as if it remembers the original wheel motion and wishes to continue that. So
cut the spout a little higher on the left than on the right, as you view the
spout exit end on.
Yet my logic would go that the spout remembers that it was twisted
anti-clockwise and now wants to reverse that direction back a little to what
it was!
I'm sure someone on clayart has actually done tests on this.
So, what is the definitive reason for the phenomena?
And what was the degree of twist?
Some, I am sure, don't bother with this at all, and get away with it! Why?
Martin Howard
Webbs Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
01371 850 423
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
Updated 6th July 2002
Martin Howard on sun 28 jul 02
I'm throwing and putting together a lot of teapots and trying to understand
the twisting of the spouts.
The books all seem to describe this phenomena as the firing of a spout
increasing the twisting in the same direction as the wheel was moving when
the spout was thrown.
So, looking at the spout with the handle of the pot furthest away from you,
and the wheel moving anti-clockwise as usual in the west, we should assume
that firing will cause the spout to twist a smidgeon further anti-clockwise,
as if it remembers the original wheel motion and wishes to continue that. So
cut the spout a little higher on the left than on the right, as you view the
spout exit end on.
Yet my logic would go that the spout remembers that it was twisted
anti-clockwise and now wants to reverse that direction back a little to what
it was!
I'm sure someone on clayart has actually done tests on this.
So, what is the definitive reason for the phenomena?
And what was the degree of twist?
Some, I am sure, don't bother with this at all, and get away with it! Why?
Martin Howard
Webbs Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
01371 850 423
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
Updated 6th July 2002
vince pitelka on sun 28 jul 02
> I'm throwing and putting together a lot of teapots and trying to
understand
> the twisting of the spouts.
> The books all seem to describe this phenomena as the firing of a spout
> increasing the twisting in the same direction as the wheel was moving when
> the spout was thrown.
Martin -
Those books are apparently incorrect. During high firing, the spout twists
further in the direction of the throwing spiral, which is opposite the
direction of wheel rotation, since your hands are holding the clay back as
the wheel turns.
Almost any clay forming method creates a linear grain structure, where the
platelets are aligned in a particular direction. In throwing, the grain
structure spirals up the pot in a direction opposite wheel rotation, but at
a steeper spiral than the finger marks left by throwing. When there is a
linear grain structure, the clay always shrinks more across the grain than
along the grain. So, this shrinkage will still be in the same direction as
the throwing spiral. It is only evident on very narrow thrown forms, such
as teapot spouts and candlesticks. In those cases, it can be impressive.
For an average teapot spout tapering down to one inch outside diameter and
perhaps three inches long, an average amount of shrinkage twist in a high
firing might be about 30-degrees clockwise as you are looking straight at
the tip of the spout, assuming that the wheel was turning counterclockwise.
So an appropriate compensation would be to cut the desired shape on the tip
of the spout approximately 30 degrees off in a counterclockwise direction.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@worldnet.att.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Margaret Barlow on sun 28 jul 02
Hello Martin,
The Potter's Dictionary by Frank and Janet Hammer gives an excellent
explanation of this under Clay - Physics of clay. Michael Cardew also
describes this in Pioneer Pottery.
Imagine yourself throwing. With the wheel going anti-clockwise (counter
clockwise) the clay is actually being pulled in a clockwise direction. The
spiral is up and clockwise.
> The books all seem to describe this phenomena as the firing of a spout
> increasing the twisting in the same direction as the wheel was moving when
> the spout was thrown.
So yes it does increase the twisting but not in the direction the "wheel"
was going but rather in the direction the "clay" was going. That being
clockwise.
When the clay shrinks it continues to follow the direction of the spiral.
As the clay shrinks the greatest shrinkage is in a downward direction ( down
the length of the spout) and as the clay shrinks downwards the spout
continues to rotate. I think of it as a spring or coil and as you compress
the spring the spiral rotates a little more.
> So, looking at the spout with the handle of the pot furthest away from
you,
> and the wheel moving anti-clockwise as usual in the west, we should assume
> that firing will cause the spout to twist a smidgeon further
anti-clockwise,
Not quite as now you know that the spout actually twists a little more
clockwise.
> Yet my logic would go that the spout remembers that it was twisted
> anti-clockwise and now wants to reverse that direction back a little to
what
> it was!
Contrary to what many potters believe the memory of the clay has little if
nothing to do with this phenomenom as it is not a reversal of the spiral but
rather a continuation of the spiral, and that being in a clockwise
direction.
> And what was the degree of twist?
The degree of twist depends on how much the spout spirals upon being throw
and that is dependent on the length of the spout and the speed with which it
was thrown and maybe a couple of other factors that I don't know about.
> Some, I am sure, don't bother with this at all, and get away with it! Why?
I don't know that one but I hope I didn't flog my point to death.
..........Margaret
Martin Howard on mon 29 jul 02
Yes, Liz, I work in earthenware and fire at cones 1-3.
So, having read the detailed help given by Vince and others and the
experiences with twisting spouts, I am leaving mine straight this time, but
putting a little white mark at 12 o'clock on the spout, just to test if
there is any twisting. Only two are cut, others are left uncut.
When throwing the spouts, I use quite a lot of pressure first of all. Then
cone in using the 6 point method (thumbs, index fingers and knuckles of
middle fingers).
Finally, I use a rib to smooth the outside and my little finger inside the
cone.
So, I do not expect a twist, but will report back.
Thanks to all who have contributed to this thread.
Martin Howard
Webbs Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
01371 850 423
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
Updated 6th July 2002
Liz Willoughby on mon 29 jul 02
I wondered if Margaret would reply. She and another potter, Leona,
and Ron Roy were over the other day (they were taking a glaze course
with Ron), and Margaret started talking about the "twist" on teapot
spouts. I always have to go to my Pioneer Pottery every time I
explain this during a workshop. Margaret's answer is right on target.
Just a little more to contribute to this discussion. The type of
clay and the temperature that you fire to is a real contributing
factor to how much the spout will twist. Earthenware twists less or
perhaps not at all. Porcelain fired to cone 11 R will twist a great
deal. The speed of throwing I find is also a factor, and how much
you have overworked your clay. COMPRESSING the clay with a bamboo
skewer on the inside and a rib on the outside does cut down on the
twist. Seems that compressing those clay particles really helps.
Just as an illustration. The porcelain that I use has some ball clay
in it. Once I tried a true English porcelain without any ball clay.
I trimmed the spout the way I usually do, spout facing me, left side
trimmed so the angle is at 5 0'clock. The teapots were trimmed this
way, and when I took them out of the kiln, the spouts were almost
sticking straight up! Almost funny.
You work in earthenware don't you Martin? You shouldn't have much of
a twist with those spouts.
Liz,
Margaret's partial reply to Martin:
>
>The degree of twist depends on how much the spout spirals upon being throw
>and that is dependent on the length of the spout and the speed with which it
>was thrown and maybe a couple of other factors that I don't know about.
>
> > Some, I am sure, don't bother with this at all, and get away with it! Why?
>
>I don't know that one but I hope I didn't flog my point to death.
>
>..........Margaret
Liz Willoughby
RR 1
2903 Shelter Valley Rd.
Grafton, On.
Canada
K0K 2G0
e-mail lizwill@phc.igs.net
Jonathan Kirkendall on tue 30 jul 02
I noticed considerably less twisting from my spouts (so much so that I've
quit worrying about it altogether) when 1) I finally learned to work the
spouts as little as possible, 2) make my next-to-last move compressing down
from the tip of the spout down towards the wheelhead, and 3) finish by
compressing against a rib for the final shape.
Jonathan in DC
80 degrees F at 7:00 am!!!! (that's hot for us!)
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