vince pitelka on tue 14 may 02
> Ya know I've NEVER had luck with the scoring/slurry thing. Every time I
did
> it, the thing, handle or coil, would crack off. I learned instead just to
> use a light brushing of water and no scoring. (I'm pressing down pretty
> hard, of course,to get good contact.) Works for me, may not work for
others.
If you have never had luck with scoring/slurry, then you were never taught
how to do it properly. You need to clarify what stage of clay you are
joining. If it is fresh wet clay, then a join without scoring or slurry
will work, because the clay platelets intermingle and thus interlock, giving
a strong joint. If the clay has stiffened at all, then it is a complete
miracle if you have been able to get away with this. When you press two
pieces of clay straight together with no slurry or water, you simply create
a fracture plane, a place for the piece to break in drying or firing.
Never score with a needle tool or with any long sharp tool, because the
groves are too deep for the slurry to penetrate, so you are left with a
network of small air bubbles which can cause the parts to pop apart in the
bisque-firing. Score with an old fork, using gentle pressure, or better
yet, use a toothed stainless steel rib. Score all stiffened surfaces. In
other words, if you are joining fresh clay to leather hard, score only the
leather hard surface. If you are joining two leather hard surfaces, score
both. Apply PLENTY of thick slurry, and work the two pieces together firmly
so that all excess slurry is displaced. Remove excess slurry, cover the
piece overnight to let the moisture equalize, and your connection will be as
strong as any other part of the piece.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
vince pitelka on wed 15 may 02
> Actually I WAS taught properly and I HAVE had success with the
score/slurry,
> I was exaggerating a tad. But when you are working as a full time
> professional potter you don't always NEED to slip/slurry everything. You
> learn to attach at the right time. You learn to listen to the clay.
> As I said, it worked for me, it may not work for others. Sometimes you CAN
> break the rules and find success!
> When you work full time as a potter you sometimes need to push the
envelope
> to get things done. You do what works. If your coils fall off you slow
down
> and do it the slow way, if you attach at the right time and your coils
don't
> fall off you go on and produce like hell.
Jeff -
There are plenty of professional potters on this list, myself included, and
your tone is a little patronizing. I've been "listening to the clay" pretty
intently for over thirty years. If you are coiling, and you are smearing
coils of fresh clay together, then of course there is no reason at all to
score and slurry. The secret is to smear them very well as you lower each
coil into place. Too many people simply lay one coil on top of the previous
one, and then smear only on the inside and outside. That will never give
as strong a wall as when the coils are smeared aggressively, in the African
tribal fashion, each coil overlapping the previous one.
There are always exceptions to every "rule" in working clay. As someone
else pointed out, the joining characteristics depend a lot on the particular
claybody. Everyone has to find their own techniques. It has nothing to do
with being a "professional potter." It simply has to do with keeping a
fresh, adventurous attitude, and a willingness to take risks. That's where
most learning tales place.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Longtin, Jeff on wed 15 may 02
Thanks Vince,
Actually I WAS taught properly and I HAVE had success with the score/slurry,
I was exaggerating a tad. But when you are working as a full time
professional potter you don't always NEED to slip/slurry everything. You
learn to attach at the right time. You learn to listen to the clay.
As I said, it worked for me, it may not work for others. Sometimes you CAN
break the rules and find success!
When you work full time as a potter you sometimes need to push the envelope
to get things done. You do what works. If your coils fall off you slow down
and do it the slow way, if you attach at the right time and your coils don't
fall off you go on and produce like hell.
Take care
Jeff Longtin
-----Original Message-----
From: vince pitelka [mailto:vpitelka@DTCCOM.NET]
Sent: Tuesday, May 14, 2002 8:57 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: attaching parts with or without scoring/slurry
> Ya know I've NEVER had luck with the scoring/slurry thing. Every time I
did
> it, the thing, handle or coil, would crack off. I learned instead just to
> use a light brushing of water and no scoring. (I'm pressing down pretty
> hard, of course,to get good contact.) Works for me, may not work for
others.
If you have never had luck with scoring/slurry, then you were never taught
how to do it properly. You need to clarify what stage of clay you are
joining. If it is fresh wet clay, then a join without scoring or slurry
will work, because the clay platelets intermingle and thus interlock, giving
a strong joint. If the clay has stiffened at all, then it is a complete
miracle if you have been able to get away with this. When you press two
pieces of clay straight together with no slurry or water, you simply create
a fracture plane, a place for the piece to break in drying or firing.
Never score with a needle tool or with any long sharp tool, because the
groves are too deep for the slurry to penetrate, so you are left with a
network of small air bubbles which can cause the parts to pop apart in the
bisque-firing. Score with an old fork, using gentle pressure, or better
yet, use a toothed stainless steel rib. Score all stiffened surfaces. In
other words, if you are joining fresh clay to leather hard, score only the
leather hard surface. If you are joining two leather hard surfaces, score
both. Apply PLENTY of thick slurry, and work the two pieces together firmly
so that all excess slurry is displaced. Remove excess slurry, cover the
piece overnight to let the moisture equalize, and your connection will be as
strong as any other part of the piece.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
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william schran on wed 15 may 02
Vince gives some good advise on attaching coils for throwing a foot
ring and attaching clay parts together. I'd like to add some things
I've discovered, some on my own, some from my students.
When attaching handles to cups, pitchers or whatever, I usually pull
my handles prior to trimming the pots and lay them out on my canvas
covered table to stiffen up. Generally find they work best right
after the glossiness (from the water) has gone. They've stiffened
enough to hold a curve, but flexible enough not to crack when bent.
Prior to attaching, I score the surface of the pot and dab a little
water on the scored area, apply slurry, score end of handle, and
press on. By wetting the pot, the water from the slurry is not sucked
into the somewhat dryer clay of the pot. I have never had a handle
crack using this method. Of course I dry the work under plastic
slowly.
From my student - she attached slabs of porcelain together creating
rather large forms. Attachment was made by scoring and using vinegar
(distilled - always wanted a salad for lunch those days), then
pressing slabs together - no slurry - no cracks. Had another student
pick this up but for stoneware and did encounter some cracking
problems. Hmmm...
Bill
Snail Scott on thu 16 may 02
At 12:04 PM 5/15/02 -0400, you wrote:
>...she attached slabs of porcelain...by scoring and using vinegar
>...then pressing slabs together - no slurry...Had another student
>pick this up but for stoneware and did encounter some cracking
>problems. Hmmm...
I've seen this property of porcelain before -
a very forgiving nature for joining leather-
hard forms together, and even nearly dry ones.
Anyone care to speculate on why this is true
of porcelain and not stoneware?
-Snail
Steve Mills on fri 17 may 02
If I may add to Vince's instructions; I join/lute pieces of leather hard
clay with a semi-wet toothbrush, a light scrubbing of both surfaces
creates both a toothed surface AND the slip to join with in one process,
that's how I like my potting; nice and simple!
Steve
Bath
UK
In message , vince pitelka writes
>
>If you have never had luck with scoring/slurry, then you were never taugh=
>t
>how to do it properly. You need to clarify what stage of clay you are
>joining. If it is fresh wet clay, then a join without scoring or slurry
>will work, because the clay platelets intermingle and thus interlock, giv=
>ing
>a strong joint. If the clay has stiffened at all, then it is a complete
>miracle if you have been able to get away with this. When you press two
>pieces of clay straight together with no slurry or water, you simply crea=
>te
>a fracture plane, a place for the piece to break in drying or firing.
>
>Never score with a needle tool or with any long sharp tool, because the
>groves are too deep for the slurry to penetrate, so you are left with a
>network of small air bubbles which can cause the parts to pop apart in th=
>e
>bisque-firing. Score with an old fork, using gentle pressure, or better
>yet, use a toothed stainless steel rib. Score all stiffened surfaces. I=
>n
>other words, if you are joining fresh clay to leather hard, score only th=
>e
>leather hard surface. If you are joining two leather hard surfaces, scor=
>e
>both. Apply PLENTY of thick slurry, and work the two pieces together fir=
>mly
>so that all excess slurry is displaced. Remove excess slurry, cover the
>piece overnight to let the moisture equalize, and your connection will be=
> as
>strong as any other part of the piece.
>Good luck -
>- Vince
>
>Vince Pitelka
>Appalachian Center for Crafts
>Tennessee Technological University
>1560 Craft Center Drive, Smithville TN 37166
>Home - vpitelka@dtccom.net
>615/597-5376
>Work - wpitelka@tntech.edu
>615/597-6801 ext. 111, fax 615/597-6803
>http://www.craftcenter.tntech.edu/
--
Steve Mills
Bath
UK
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