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slumping help

updated mon 31 may 99

 

muddpie on wed 26 may 99

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Ok you firing guru's out there.... I need some help please=21

I am using A.R.T.'s =23125 Speckled Brownstone, hump molding some
medium and larger low bowls, which are made from approx. 1/4=22
thick slabs and using 3 smallish ball-like feet I am impressing
leaves or pine sprigs into the clay and when they reach that
leather hard stage, I glaze the leaf patterns only. I then once
fire these to cone 6 going up at a rate of 220=B0 per hour. My
problem is that they are slumping .... sometimes getting almost
flat on the shelves. If not flat, warped very very badly. Am I
doing something wrong?? going up in temperature too fast? My
picture frames and clocks I have no problem with as they are flat
tile like shapes anyway, and lay flat on the shelves. But I
really kinda wanted the bowls to be .... well.. bowl shaped you
know??=21=21

Any suggestions or comments out there? All help and comments will
be greatly appreciated=21=21

stumped (and slumping) in michigan, where it really has changed
back to fall... burrrrrrr...
JuliE

muddpie on fri 28 may 99

------------------

Ok you firing guru's out there.... I need some help please=21

I am using A.R.T.'s =23125 Speckled Brownstone, hump molding some
medium and larger low bowls, which are made from approx. 1/4=22
thick slabs and using 3 smallish ball-like feet I am impressing
leaves or pine sprigs into the clay and when they reach that
leather hard stage, I glaze the leaf patterns only. I then once
fire these to cone 6 going up at a rate of 220=B0 per hour. My
problem is that they are slumping .... sometimes getting almost
flat on the shelves. If not flat, warped very very badly. Am I
doing something wrong?? going up in temperature too fast? My
picture frames and clocks I have no problem with as they are flat
tile like shapes anyway, and lay flat on the shelves. But I
really kinda wanted the bowls to be .... well.. bowl shaped you
know??=21=21

Any suggestions or comments out there? All help and comments will
be greatly appreciated=21=21

stumped (and slumping) in michigan, where it really has changed
back to fall... burrrrrrr...
JuliE

Andrea & Armand Grez on fri 28 may 99

> My
> problem is that they are slumping .... sometimes getting almost
> flat on the shelves. If not flat, warped very very badly.

JuliE,

I don't have a solution to your problem, but I DO have the same
problem. I have tried making plates on a plaster hump mold; while they
dry fine and without warping, and make it through the bisque fire fine,
they end up nearly flat as a pancake coming out of the ^6 glaze fire.

This has happened with both a white stoneware and a red sculpture, both
have a decent amount of grog.

I'd love to hear what others have to say about prevention or cure.
Mashed potatoes and gravy just doesn't work on these plates!

Regards, Andrea Grez in warm and sunny, hummingbird-filled Richmond

deborah goletz on sun 30 may 99

Julie - do you paddle the slab once it's in place on the hump mold? This
may help re-configure those plate-like clay molecules (rolling out a slab
lines them up flat - you have to compress them into into their new form -
particularly where it curves into the rim). You may find starting out with
a bit thicker slab is helpful too. I find using a wood paddle with a
slight curve in it (think mixing spoon) helpful.
DeBorah