Robert Santerre on wed 16 feb 00
Clayarters,
I'm hoping someone in the group can help me. I'm looking for formulas
for high-fire sculptural clay bodies. I've been making some large
vase/sculptures. These are shaped somewhat like two sails (from a
sailboat) stitched together to make a hollow interior. The two walls
(sails) are quite large, appx. 30 X 40 inches. I roll out large slabs
(about 3/4 inch thick), transfer them to a cardboard form, let them dry
to leatherhard stage, stand them up and place them on a clay slab base
and then seal (slip and score) the edges of the two "sails" together to
make the vessel form.
My problem is cracking of the broad "sail" surfaces during the drying
stage (the cracks are mainly single, long vertical cracks near the
center of the "sails"). I'm getting about 50% survival, but that means
on average every piece has one crack in it. I would like to experiment
with some different clay bodies that hopefully would have less shrinkage
and more resistance to cracking of large curved surfaces during the
drying stage (I dry very slowly - weeks). I'd also like to have a
whiter clay. The clay I'm using now is light pink when bisqued. This
is an "all purpose" body developed for general class use at Herron Art
School (Indiana University-Purdue University):
Goldart 5
Fire clay (AP Green) 1
KY Ball Clay 0.5
fine grog 0.5
Custer feldspar 0.5
silica 0.25
Sorry, the units here are volume units (actually scoopfuls). Not very
sophisticated, but it works and this is a good general-purpose body for
throwing and handbuilding (small sculptures).
Any help in dealing with my problem would be most appreciated -
formulas, literature references, etc.
Bob
rfsanterre@iquest.net
Curt Lacross on thu 17 feb 00
>
>Robert,
Here is a twist. Try 8 parts fireclay, 3 parts 60 mesh grog, and 2 parts
OM4 ball clay.I have had really good luck with this simple body. You
could also go to a concrete dispatcher and get some nylon fibers to add
to your clay. It will solve your cracking problem. The only drawback is
that the clay is difficult to cut.Good luck
Curt
Jeff Campana on thu 17 feb 00
Have you ever tried nylon fiber additions to the clay? This is definitely
availible at several suppliers i know of, and is very effecrive. The small
nylon fibers create a crude fabric-like network, giving the clay a lot of
added strength, and simply burn out upon firing. This also makes the clay
behave like fabric, allowing you to make thinner walls with the same
strenth in wet and drying stages. i think thinner walls would reduce the
occurance of cracking also. The only downside is that the fibers make clay
dificult to cut with wires, and can gum tools up occasionally. If you do
try fiber, i would add volumetrically approx. .05-.1 parts in that recipe
you use
Jeff Campana
Robert Santerre wrote:
> ----------------------------Original message----------------------------
> Clayarters,
>
> I'm hoping someone in the group can help me. I'm looking for formulas
> for high-fire sculptural clay bodies. I've been making some large
> vase/sculptures. These are shaped somewhat like two sails (from a
> sailboat) stitched together to make a hollow interior. The two walls
> (sails) are quite large, appx. 30 X 40 inches. I roll out large slabs
> (about 3/4 inch thick), transfer them to a cardboard form, let them dry
> to leatherhard stage, stand them up and place them on a clay slab base
> and then seal (slip and score) the edges of the two "sails" together to
> make the vessel form.
>
> My problem is cracking of the broad "sail" surfaces during the drying
> stage (the cracks are mainly single, long vertical cracks near the
> center of the "sails"). I'm getting about 50% survival, but that means
> on average every piece has one crack in it. I would like to experiment
> with some different clay bodies that hopefully would have less shrinkage
> and more resistance to cracking of large curved surfaces during the
> drying stage (I dry very slowly - weeks). I'd also like to have a
> whiter clay. The clay I'm using now is light pink when bisqued. This
> is an "all purpose" body developed for general class use at Herron Art
> School (Indiana University-Purdue University):
>
> Goldart 5
> Fire clay (AP Green) 1
> KY Ball Clay 0.5
> fine grog 0.5
> Custer feldspar 0.5
> silica 0.25
>
> Sorry, the units here are volume units (actually scoopfuls). Not very
> sophisticated, but it works and this is a good general-purpose body for
> throwing and handbuilding (small sculptures).
>
> Any help in dealing with my problem would be most appreciated -
> formulas, literature references, etc.
>
> Bob
> rfsanterre@iquest.net
Paul Taylor on thu 17 feb 00
Dear Robert
Paper clay is your only man. It can be assembled wet or bone dry . .
However I would still leave some grog in it.
Paper clay is clay that is mixed with fibers. I have used shredded
paper( from your local spy) add dry to the clay powder and mix. This is good
for thick stuff. But beware it takes some drying out the fibers hold water.
Or better still tear up a card board box slake it then mash it to pulp in
a blender and mix with clay powder. Then you can get it unbelievably thin.
You could use flocking or other fibers .
The beauty of the stuff is its unfired strength. There is still bend in it
when dry.
I do not Know what local clays you have but any stone ware recipe will do
so you should not restrict yourself. How much paper to clay depends on what
you are making. Potters spend their life experimenting. Are you sure you
have the sufficient amount of lose screws? If not stick to marble.
Regards paul T
ps personal replies to tamblin@go.com as well as ANU. People have been
having trouble with the latter.
----------
>From: Robert Santerre
>To: CLAYART@LSV.UKY.EDU
>Subject: Re: stoneware body for sculpture
>Date: Thu, Feb 17, 2000, 12:41 am
>
>----------------------------Original message----------------------------
>Clayarters,
>
>I'm hoping someone in the group can help me. I'm looking for formulas
>for high-fire sculptural clay bodies. I've been making some large
>vase/sculptures. These are shaped somewhat like two sails (from a
>sailboat) stitched together to make a hollow interior. The two walls
>(sails) are quite large, appx. 30 X 40 inches. I roll out large slabs
>(about 3/4 inch thick), transfer them to a cardboard form, let them dry
>to leatherhard stage, stand them up and place them on a clay slab base
>and then seal (slip and score) the edges of the two "sails" together to
>make the vessel form.
>
>My problem is cracking of the broad "sail" surfaces during the drying
>stage (the cracks are mainly single, long vertical cracks near the
>center of the "sails"). I'm getting about 50% survival, but that means
>on average every piece has one crack in it. I would like to experiment
>with some different clay bodies that hopefully would have less shrinkage
>and more resistance to cracking of large curved surfaces during the
>drying stage (I dry very slowly - weeks). I'd also like to have a
>whiter clay. The clay I'm using now is light pink when bisqued. This
>is an "all purpose" body developed for general class use at Herron Art
>School (Indiana University-Purdue University):
>
>Goldart 5
>Fire clay (AP Green) 1
>KY Ball Clay 0.5
>fine grog 0.5
>Custer feldspar 0.5
>silica 0.25
>
>Sorry, the units here are volume units (actually scoopfuls). Not very
>sophisticated, but it works and this is a good general-purpose body for
>throwing and handbuilding (small sculptures).
>
>Any help in dealing with my problem would be most appreciated -
>formulas, literature references, etc.
>
>Bob
>rfsanterre@iquest.net
Elca Branman on fri 18 feb 00
>and then seal (slip and score) the edges of the two "sails" together
>to
>make the vessel form.
>
>My problem is cracking of the broad "sail" surfaces during the drying
>stage (the cracks are mainly single, long vertical cracks near the
>center of the "sails"). I'm getting about 50% survival, but that
>means
>on average every piece has one crack in it. I would like to
Try painting the central section where cracks form with wax resist so as
to retard the drying there and therefore provide less stress .
Same principle as letting the center of plates dry before the sides;the
edge shrinking first will not make stress on the center sections.
shrinkage.
Elca Branman
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NakedClay@aol.com on fri 18 feb 00
Curt,
Is your clay recipe for Cone 6-10?
Milton NakedClay@AOL.COM
=====================
Curt wrote:
Here is a twist. Try 8 parts fireclay, 3 parts 60 mesh grog, and 2 parts
OM4 ball clay.I have had really good luck with this simple body. You
could also go to a concrete dispatcher and get some nylon fibers to add
to your clay. It will solve your cracking problem. The only drawback is
that the clay is difficult to cut.Good luck
Stephen Grimmer on sat 19 feb 00
Robert,
You might try something along the lines of this.
Sculpture Body, Cone 10
12 Hawthorne Bond
10 AP Green Fire Clay
22 Goldart
22 OM #4
6 Coarse Grog
14 Medium Grog
14 G-200 feldspar
2 Bentonite
Increase the ball clay at the expense of the Hawthorne to get the plasticity
you need. Fireclays can sometimes be troublesome; you might want to mix the
fireclays and bentonite with water and screen through 50 mesh. Having two
different fireclays helps minimize the effect of either changing. People
here use variations on this recipe to successfully build and fire very large
sculptures (6' and up).
steve
--
Steve Grimmer
Bowling Green State University
Bowling Green, OH
----------
>From: Robert Santerre
>To: CLAYART@LSV.UKY.EDU
>Subject: Re: stoneware body for sculpture
>Date: Wed, Feb 16, 2000, 6:41 PM
>
> ----------------------------Original message----------------------------
> Clayarters,
>
> I'm hoping someone in the group can help me. I'm looking for formulas
> for high-fire sculptural clay bodies. I've been making some large
> vase/sculptures. These are shaped somewhat like two sails (from a
> sailboat) stitched together to make a hollow interior. The two walls
> (sails) are quite large, appx. 30 X 40 inches. I roll out large slabs
> (about 3/4 inch thick), transfer them to a cardboard form, let them dry
> to leatherhard stage, stand them up and place them on a clay slab base
> and then seal (slip and score) the edges of the two "sails" together to
> make the vessel form.
>
> My problem is cracking of the broad "sail" surfaces during the drying
> stage (the cracks are mainly single, long vertical cracks near the
> center of the "sails"). I'm getting about 50% survival, but that means
> on average every piece has one crack in it. I would like to experiment
> with some different clay bodies that hopefully would have less shrinkage
> and more resistance to cracking of large curved surfaces during the
> drying stage (I dry very slowly - weeks). I'd also like to have a
> whiter clay. The clay I'm using now is light pink when bisqued. This
> is an "all purpose" body developed for general class use at Herron Art
> School (Indiana University-Purdue University):
>
> Goldart 5
> Fire clay (AP Green) 1
> KY Ball Clay 0.5
> fine grog 0.5
> Custer feldspar 0.5
> silica 0.25
>
> Sorry, the units here are volume units (actually scoopfuls). Not very
> sophisticated, but it works and this is a good general-purpose body for
> throwing and handbuilding (small sculptures).
>
> Any help in dealing with my problem would be most appreciated -
> formulas, literature references, etc.
>
> Bob
> rfsanterre@iquest.net
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