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vince's parallel coils

updated fri 22 feb 08

 

Marcia Selsor on wed 20 feb 08


I made some of these 1/4" by extruding them through steel with large
holes 1/4" wide.
I have used them on square slabs fired on end but use them more for
bird bath stems
and large bowls like a basin for bird baths. I reuse them again and
again. I think they
are great. The get big pieces off the shelf, don't distort the shape,
I also use them under heavy capitals and any large 18" -40" segments
for arches.
For long pieces spanning three shelves , these work amazingly well and
better than grog as he says.
This is what I love about clayart. You can always learn something. I
think he first mentioned these about 10 years ago.

Marcia Selsor

On Feb 19, 2008, at 8:15 PM, vpitelka wrote:

> Tom Sawyer wrote:
> "The general question that I would like suggestions on is a problem
> that I
> am
> having firing large slabs. I wish to make a set of slabs about 20 x 25
> inches in size. I've been using paper clay and get them dried
> without much
> warping but when I fire them [lying flat], I get an inordinate
> amount of
> cracking; when fired upright they slump. Does anyone have any
> suggestions."
>
> Tom -
> Most likely they are cracking because of differential shrinkage as
> they heat
> up or cool down. That is always a problem when firing large flat
> things
> right on the kiln shelf. I would suggest firing them on wadding -
> either a
> network of small balls of wadding, or else parallel coils. Either
> will work
> well and will allow the heat and atmosphere to pass beneath the
> piece and
> eliminate the problem of the thick kiln shelf keeping the center of
> the
> piece cold in heating and hot in cooling. Unless you are firing in
> salt or
> soda, just mix any clay 50/50 with flint as a cheap, effective
> wadding. If
> you use coils, don't criss-cross them, because that will create
> closed air
> spaces and defeat the purpose.
>
> The reason for using the 50-50 clay-flint mix is so that you can
> heat the
> kiln as fast as you want to in the glaze firing. The 50% flint
> opens up the
> body so much that steam and volatiles can escape without ever
> building up
> pressure.
>
> Some people advocate firing large clay slabs on a bed of sand or
> grog, and
> while that does insulate the slab from the kiln shelf, it does not
> allow
> heat and atmosphere to pass beneath the slab, and doesn't work as
> well as
> wadding.
> Good luck -
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
>

Marcia Selsor
http://marciaselsor.com

Terrance Lazaroff on wed 20 feb 08


Marcia and Vince
What a great reminder. I remember using coils years ago and somehow I
forgot the value of these great objects. I recently fired a series of
poured paper clay slabs. I was getting about a 1 to 4 ratio of success
firing them on a bed of sand. My next series will be fired on coils.

The longer we are in this art form the more we forget.

Terrance F. Lazaroff,CD
Visit my website at http://www.clayart.ca

Tom Sawyer on thu 21 feb 08


Vince,

Thanks for a great idea; Before I read your reply, I began thinking about
using some porcelain marbles under the slabs but I like the idea of the
coils better.
Tom Sawyer

-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Marcia Selsor
Sent: Wednesday, February 20, 2008 8:10 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Vince's parallel coils

I made some of these 1/4" by extruding them through steel with large
holes 1/4" wide.
I have used them on square slabs fired on end but use them more for
bird bath stems
and large bowls like a basin for bird baths. I reuse them again and
again. I think they
are great. The get big pieces off the shelf, don't distort the shape,
I also use them under heavy capitals and any large 18" -40" segments
for arches.
For long pieces spanning three shelves , these work amazingly well and
better than grog as he says.
This is what I love about clayart. You can always learn something. I
think he first mentioned these about 10 years ago.

Marcia Selsor

On Feb 19, 2008, at 8:15 PM, vpitelka wrote:

> Tom Sawyer wrote:
> "The general question that I would like suggestions on is a problem
> that I
> am
> having firing large slabs. I wish to make a set of slabs about 20 x 25
> inches in size. I've been using paper clay and get them dried
> without much
> warping but when I fire them [lying flat], I get an inordinate
> amount of
> cracking; when fired upright they slump. Does anyone have any
> suggestions."
>
> Tom -
> Most likely they are cracking because of differential shrinkage as
> they heat
> up or cool down. That is always a problem when firing large flat
> things
> right on the kiln shelf. I would suggest firing them on wadding -
> either a
> network of small balls of wadding, or else parallel coils. Either
> will work
> well and will allow the heat and atmosphere to pass beneath the
> piece and
> eliminate the problem of the thick kiln shelf keeping the center of
> the
> piece cold in heating and hot in cooling. Unless you are firing in
> salt or
> soda, just mix any clay 50/50 with flint as a cheap, effective
> wadding. If
> you use coils, don't criss-cross them, because that will create
> closed air
> spaces and defeat the purpose.
>
> The reason for using the 50-50 clay-flint mix is so that you can
> heat the
> kiln as fast as you want to in the glaze firing. The 50% flint
> opens up the
> body so much that steam and volatiles can escape without ever
> building up
> pressure.
>
> Some people advocate firing large clay slabs on a bed of sand or
> grog, and
> while that does insulate the slab from the kiln shelf, it does not
> allow
> heat and atmosphere to pass beneath the slab, and doesn't work as
> well as
> wadding.
> Good luck -
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
>

Marcia Selsor
http://marciaselsor.com

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