Elizabeth Priddy on thu 28 sep 06
I throw on clay tiles in a plast-bat homemade chuck.
I have never had s-cracks and neither have my students
since I began using them.
They dry the bottoms evenly and you can just leave
them there intil they pop off and are perfect for
trimming.
I have used a dozen clays with the same result and I
do not baby my pots in the slightest. Whatever the
room atmosphere is is what it dries in.
Look to the archives for how to make one, what type of
tile to use, where to find it, and all that.
All of the variables mentioned by people flummoxed by
s cracks have been in play in my studio and yet no s
cracks, including incompetent throwing by beginners.
And still no cracks, must be the tile-bats.
-E
Elizabeth Priddy
Beaufort, NC - USA
http://www.elizabethpriddy.com
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Nancy Braches on thu 28 sep 06
Hi Elizabeth
I searched the archives and read on the clay tiles. Do you have the plaster bat making system I have seen advertised or do you make your plaster bats differently? I have 2 soldner wheels, one being from way back. It was used as a demo model by Paul himself ( a local college had it and recently sold all their soldner wheels and bought new). They have the pins permanently attached (or they are so old and are set in there permanently)...I use bats most of the time and don't take items off the bat until I am ready to trim and/or sign the bottoms so I need to be able to have the bat pin holes in the plaster bats. I know plaster is great for drying but I worry about students (or myself!) hitting it with a tool and winding up with plaster in the clay.
I hate to bring this subject up again, but I did search the archives and found some info but am hoping you can provide a little more.
Thanks in advance
Nancy
Hilltop Pottery
Elizabeth Priddy wrote: I throw on clay tiles in a plast-bat homemade chuck.
I have never had s-cracks and neither have my students
since I began using them.
They dry the bottoms evenly and you can just leave
them there intil they pop off and are perfect for
trimming.
I have used a dozen clays with the same result and I
do not baby my pots in the slightest. Whatever the
room atmosphere is is what it dries in.
Look to the archives for how to make one, what type of
tile to use, where to find it, and all that.
All of the variables mentioned by people flummoxed by
s cracks have been in play in my studio and yet no s
cracks, including incompetent throwing by beginners.
And still no cracks, must be the tile-bats.
-E
Elizabeth Priddy
Beaufort, NC - USA
http://www.elizabethpriddy.com
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Elizabeth Priddy on thu 28 sep 06
No, not plaster bats, "Plast-i-bats"
I use one that is the exact width of the tile I am
throwing on and cut a square hole about 1/8th inch
larger than the tile I am using.
I designed this system about 7 years before I ever saw
one sold, and that one has a flaw, see below.
You can make it for about $5 for a plastibat and about
$20 will buy you a case of absorbant outdoor patio
tile. Italian terra cotta work best for me, but you
can use any that have a surface that is flat, smooth,
absorbant, and unglazed. You could probably make some
and fire to about halfway between mature and bisque.
Mature won't absorb right and bisque won't stick
right.
No plaster involved, and the plastibat simply sits on
the bat pins as usual. You could use a wood form for
this, but I find that the plastic material works great
and no splinters to happen from the lifting action.
Lili's system of making would work fine, but I don't
see the need for the molding, I just make a notch in
the square hole and use a screwdriver to lift up the
tile out of the hole.
I don't actually like the system that is sold in mags
as the insert tiles are plastic as well and then you
don't get the absorbant beneficial action of the clay
tile.
If you are trying to avoid s-cracks with this system,
the plastic one for sale won't help you with that.
See my original post on the reason for that.
If you are looking for a good way to store about a
hundred bats underneath one wheel, the tiles can't be
beat.
And they line up neatly on your ware boards, unlike
round space-hog bats.
No offense to the people making that product, but it
just ain't the same.
E
Elizabeth Priddy
Beaufort, NC - USA
http://www.elizabethpriddy.com
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Stephani Stephenson on thu 28 sep 06
Nancy
cracks can occur when there is undue tension in one area , often as a
result of uneven tension/compression (think of the clay being more
stretched in one area than another or stretched in one area and and
compressed in another )
. This can occur in pressed tiles as well as thrown work .
I had a batch of tiles do this once
identical s-cracks in every tile that I pressed one afternoon. It was a
mystery to me, as I was using same clay, same drying, with no moisture
settling into the
center of the tile. they were cap tiles which were about 6 inches by 8
Inches.
I realized all the tiles with S-cracks were pressed by hand on one
afternoon,
that was the only difference
The only conclusion I came to was (I came to the conclusion later ,but
I physically remember doing this)
I cut plugs that were a bit too small so instead of driving straight
down with my pressing stroke as usual
I pushed outward from the center, literally stretching the clay in the
center of the tile
to make sure I got to the perimeter with enough clay.
I remember doing this with some gusto!
the clay at the center would have been under a good deal more tension
than the clay at the perimeter,
which was compressed against the edge of the plaster press mold.
It would have been under far more lateral tension than normal.
Remember when you learned to throw on the wheel, especially when
throwing plates and wide rimmed forms, you learned to exert even
pressure /tension/compression as you pulled out from the center to
rim? same thing. a differential in that compression or tension can
contribute to either cracking (tension high) or warping (compression
high in relation to area next to it)
I had learned this with regard to wheel work but had forgotten about
it and not realized I could apply it to tile or pressed work. When
I heard dr. Wm Carty from Alfred speak at NCECA in Indianapolis a few
years back, he spoke about this dynamic, and , yes, the light bulb went
on for me. So this is one of the observations I apply . Though I press
rather than throw tile, the concept may still have value for you as you
try to remedy this problem.
I will say that the s crack problem had never occurred before or after
that occasion, but I do believe that my attempts to compensate for
cutting a too small plug
cause me to stretch the clay too much from the center out... who knows
... maybe I had some Beethoven, Midnight Oil or Gypsy Kings on in the
studio and pressed in flamenco fashion that afternoon!
So pay attention to that part of your wheel process and maybe you will
find a clue.
best wishes!
Stephani Stephenson
steph@revivaltileworks.com
http://www.revivaltileworks.com
Mitch Kotula on fri 29 sep 06
Try drying tiles between pieces of wallboard, the white chalky stuff covered with paper on both sides. The wallboard dries the tiles on both sides while maintaining pressure to avoid warping and curling corners. Just don't stack too many tiles and layers of wallboard to avoid smushing the tiles.
Dry slowly.
With plates, platters and wide bottomed bowls, dry very slowly and fire with a special ramp to get you through the quartz conversion at 1067 F, going up and cooling down. I have been putting in a ramp at 1000 F to go 50F/hour rate to 1125 F, then resume the firing schedule. The opposite when cooling down.
With the exception of poorly thrown and not very compressed pieces, the s-crack crisis has passed.
Mitch
Mitch Kotula
Development Plus
PO Box 2076
Hamilton, MT 59840-4076
406-961-5136 (Home)
406-546-6980 (Cell)
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Nancy Braches on fri 29 sep 06
I seem to only get some s cracking when throwing off the hump. I like having my students throw 5+ lbs of clay on the wheel and make as many tiny bowls as they can. Then trim them when they are ready. I feel it makes them feel the clay and instead of throwing 1 3lb bowl they can make 20-30 bowls from one shot of clay on their wheel. Then trim trim trim. I have never had any student say the exercise didn't help them learn to feel the clay and to make a bowl that is pretty inside and out. Compress the bottom slightlybefore wiring off and compress again while trimming. What I see most is the S cracks form when the bottom is a lot thicker than the sides/top.
I am interested in Elizabeth's idea, not for S cracks, but for convenience and space. I have 5 of the bailey wood bats and if my piece is large I leave it on the bat and after a few days it just pops off. Have never had a problem with an S crack on those, but they are big and bulky and HEAVY. After 3 years of using them some of them are now offering splinters to my hands so I am looking to try a method that works for others.
I think S cracks have so many variables it can be hard to say which caused the problem. I tell my students, don't fall in love with that piece until it is out of the glaze firing...there are just too many variables and dropping it in the driveway on your way home counts as one.
Nancy
Hilltop Pottery
Mitch Kotula wrote: Try drying tiles between pieces of wallboard, the white chalky stuff covered with paper on both sides. The wallboard dries the tiles on both sides while maintaining pressure to avoid warping and curling corners. Just don't stack too many tiles and layers of wallboard to avoid smushing the tiles.
Dry slowly.
With plates, platters and wide bottomed bowls, dry very slowly and fire with a special ramp to get you through the quartz conversion at 1067 F, going up and cooling down. I have been putting in a ramp at 1000 F to go 50F/hour rate to 1125 F, then resume the firing schedule. The opposite when cooling down.
With the exception of poorly thrown and not very compressed pieces, the s-crack crisis has passed.
Mitch
Mitch Kotula
Development Plus
PO Box 2076
Hamilton, MT 59840-4076
406-961-5136 (Home)
406-546-6980 (Cell)
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Bonnie Staffel on sat 30 sep 06
Nancy,
I believe that I gave a post regarding the coning (wheel kneading) of the
ball of clay and my method that eliminated S cracks on little pots thrown
off the hump. You can find my posts in the archives. I just found it
259896 06/08/05 22:21 73 clay preparation I hope that it helps your
problem. It did mine.
Bonnie Staffel
http://webpages.charter.net/bstaffel/
http://vasefinder.com/bstaffelgallery1.html
DVD Throwing with Coils and Slabs
DVD Beginning Processes
Charter Member Potters Council
Nancy Braches on sat 30 sep 06
Thanks Bonnie!
I will give it a try as I hate those S cracks on my little bowls, they are great little sellers when I go to the local craft shows (more for advertising mybusiness and classes than for selling) and people can pick them up for 3-5 bucks. Of course I take a few "bigger" pieces as well but in this area people don't look for expensive items as the shows. I call it my day of promoting me :)
I do cone with the sides of my hands, having the center come up first. When throwing regular pieces I do it 3-5 times, cone...press out cone ....so on. I just don't do it with off the hump since I was taught just throw the mess on the wheel and center just a handful at a time. Too cold to throw out there today...haven't got my woodstove hooked back up and brrrrrrrrr 36 last night here and today windy/rainy. In the next couple of days, I'm gonna try your way and I hope it works for me!
Nancy
Hilltop Pottery
Bonnie Staffel wrote: Nancy,
I believe that I gave a post regarding the coning (wheel kneading) of the
ball of clay and my method that eliminated S cracks on little pots thrown
off the hump. You can find my posts in the archives. I just found it
259896 06/08/05 22:21 73 clay preparation I hope that it helps your
problem. It did mine.
Bonnie Staffel
http://webpages.charter.net/bstaffel/
http://vasefinder.com/bstaffelgallery1.html
DVD Throwing with Coils and Slabs
DVD Beginning Processes
Charter Member Potters Council
______________________________________________________________________________
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
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Kathy Stecker on sat 30 sep 06
"Try drying tiles between pieces of wallboard, the white chalky stuff
covered with paper on both sides. The wallboard dries the tiles on both sides
while maintaining pressure to avoid warping and curling corners. Just don't
stack too many tiles and layers of wallboard to avoid smushing the tiles"
You might want to tape the edges of these boards with masking tape or I used
electrical tape to keep that white chalky stuff from getting into your clay:)
Kathy Stecker
Can't wait for the Ron Meyers workshop on Oct 14 and 15 at Crealde in Winter
Park Florida USA-still time to sign up folks
_www.crealde.org_ (http://www.crealde.org) 407 671-1886
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