Mold release for clay?

I'm going to make some simple slumping molds by forming clay slabs over convenient shapes. Anything I've read says that clay will stick to non-porous surfaces, and that a barrier (typically fabric) should be used. Is there anything which will act as a release agent? I'm trying to avoid wrinkles over curved surfaces and weave prints in the clay if possible.

* pam. plastic wrap.
the thing about clay is it's going to shrink when drying, so you can't leave it on the mold. furthermore, once dry, it's very easily sanded before bisquing it. don't breath the dust.

* Use a fine weave muslin or stretch fabric.
When the clay is leather hard (damp but dry enough to hold it's shape) you can scrape away any texture using flexible rubber, steel or plastic tools. You can buy these where you buy your clay. They're called "ribs".
Also you're going to have to apply a kiln wash to the mold to keep the glass from sticking to the mold. That kiln wash, applied in several layers, will further obscure the fabric texture. When the kiln wash is dry you can buff it with a soft cloth leaving a very smooth surface.

* OK, I wondered about Pam, especially since I've already got a can dedicated to shop use (for fibreglass molding).
I didn't know about sanding greenware. That will help.
Maybe the fabric weave won't be so much of an issue. Off to experiment...

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