how to keep clay from curling up when its drying?

[PotteryLodge]

I was making some quarter inch flat stoneware clay coasters yesterday and as they were drying the ends started lifting upwards. I would flatten them back out while they were still workable, but this morning when I woke up to check on them a few of the clay coasters are slightly lifted on the edges.

Any thoughts to why this is happening and what to do about it?

[FlamingChalice]

I leave the tiles or coasters between 2 pieces of plaster board over night. When they are leather hard, O put them on drying racks - like for cookies or the plastic mesh for light fixtures.

[PotteryLodge]

Thank you Kat. I will try that next time. : )

[firenfluxhandmade]

clay has memory so if they lifted and you moved them back even if they look flat when they're dry they could lift again when fired.

I put any slablike items between 2 wood bats while drying to keep them flat.

[Former_Member]

I was advised to use even pressure on both sides and really compress the clay well. You would want to flip the clay if you were using a slab roller so that it is compressed the same amount on both sides or burnish both sides. It doesn't seem to be as big of a problem with press molds if you really work the clay in. I have only tried the burnishing so far and it has worked well for me.

[KilnMasterPottery]

Other thing is to make sure you roll them out on both sides and in all directions. You want to make sure the clay is well and evenly compressed on all sides. Dry them covered, slowly and flip them over few times. Any uneven drying or compression can pull them out of shape. And sometimes the warping does not show up till it is out of glaze fire.

[inHIShandsart]

I've had some good results from leftover pieces of sheet rock. Just wrap fragile edges of sheet rock with duct tape.

After you roll out the tiles or whatever, put them on a piece of sheet rock and cover with another piece. The sheetrock keeps them flat while slowly absorbing the moisture.

[GoldhawkPotteryEtc]

I agree with Abbey and others. For small pieces I put between two bats, but make sure they are evenly distributed on the bat. I use drywall that I bought at Home Depot, had them cut it into 4 pieces, took them home and taped duct tape around all of the edges. I use them on my shelves for drying all flat pieces that are rolled out on my slab roller (agreed that a slab roller is great for keeping pieces even in thickness.) Just make sure to roll a few times and turn the clay over. My dad made the slab roller for me - using some instructions from an old Ceramics Monthly magazine. So glad to have it because they can be expensive.