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tiles become distorted

updated sun 4 apr 10


Calli Mico on thu 1 apr 10

Tile-Making is new to me---doing a special order for a family member, usi=
my cone 10 b-mix clay and my usual glazes.

I made plaster molds and am pressing them--they're about 3.5" square by 3=
thick. All this is going well. The tiles are drying and bisquing flat
enough. BUT....

When fired to maturity with a glaze, they go out of square. Granted, some=
my molds are not super exact. The tiles are shrinking in at the sides (or=

one side more than the other)--distorting. The surface has a carved relie=
design with shallow depth. I have corrected some of the molds, and this h=
helped, but there is still variation from firing to firing----sometimes t=
shrinking is more, sometimes less.

What do you think of this idea? I'm thinking of just firing the cone 10 c=
to cone 6, thinking that if the clay structure isn't "pulled in" so much =
the high heat, then the distortion won't be so bad. 'Course, I'll have to=

mix up some cone 6 glazes for the tiles, and then the glazes probably won=
fit a cone 10 body, and then I'll have to test some more......and, and.


Stephani Stephenson on sat 3 apr 10

Hi Calli,
This may or may not help, but I'll toss it out to you, just in case!

Are you cutting tile 'slabs' directly from the end of the (previously
bagged )clay block?
if you are cutting clay from the bag and directly pressing it into the m=
try cutting the clay from the long rectangular 'side' of the clay block,
rather than the end.
pugged, bagged clay can still have spiral tendencies which can possibly
effect the way a tile
dries. If you cut from the long end of the block, it minimizes this effec=

Are you rolling the cut clay out with a slab roller or rolling pin before=

pressing it? with a highly plastic clay, pay attention to whether you are=

stretching it one way more than another. With the less plastic tile clay=
this is not so much a factor. i am not sure it is a factor in your case, =
just pay attention to it to see if you are introducing any unequal
stretching or compressing actions into the slab.

Finally ,pay attention to your pressing. Are you exerting pressure in a
downward, compressing motion when you press the clay? Or is there a
possibility that you are=3D20
stretching the clay to get it to the edge of the mold.

Unequal areas of compression and tension can lead to either warping or
cracking and=3D20
differential shrinkage as well...
Just mull these things over as you form your tiles. strive for equal
compression, and focus on pressing down rather than out, etc.

Like I say, may not be a factor, but sometimes the little things matter!

good luck with your project.
Stephani Stephenson