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acg

slab warpage

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Hi,

 

A friend and I share a kiln together. She is having problems with warping in the bisque.

 

Clay body - Tacoma Clay Art paper clay

firing - ^06 using the Skutt firing schedule

Thickness - 1/4/ to 1/2 ins.

Tossed and rolled with a rolling pin

Design made on drying board

Dried to soft leather hard then: either a second sheetrock board is put in top or weights put on the 4 corners

At leather hard put in a convection oven. on the oven racks and dried for 12 hr at 170 F

Placement in kiln - larger pieces stacked flat on the top shelves, spanned the kiln shelves these had the most warpage

smaller pieces stacked leaning against the shelf

the smaller pieces stacked flat on the bottom shelf seems to have the least warpage

 

 

These forums are so great. Thanks for all your help

 

acg

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I put my large raku slabs on to sheet rock lined with newsprint paper. I roll them on my slab roller. Slide a board underneath the slab mat, place the newsprint on top of the slab, place sheet rock on top of that, then flip the whole thing tightly sandwich to avoid any disfiguring of the slab.

Once flipped, I remove the board and slab mat, attach hanging nubs, wax the edges , slide the sheet rock and slab into my bakers rack covered with plastic and don't move it til it is dry.I bisque them on edge and fire them on edge as well. See photo from Raku Masters at Dan Finch's.. I think you are handling them too much especially before leather hard.

Marcia

post-1954-135179339538_thumb.jpg

post-1954-135179339538_thumb.jpg

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1 sided tiles? score the back...i carve a grid with a wide trimming tool a bit less than 1/2 the tile thickness...look at the back of a factory tile to see what i mean, little raised squares are all that is left at full thickness

 

slow drying under plastic for 1 week plus, skip the oven (never heard of that).. the slower the better

 

not familiar with that clay body, but that could be a factor...maybe test adding some sand or grog

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