Warping And Drying Time

[Heidi1]

Hi, I just started to hand build with 2 different types of clay that are easy to work with. (Bennet and Oregon brown grogg) Made a couple of soap dishes and cookie cutter flat ornaments. The soap dishes were okay but the little flat cut outs pretty much all warped. I had them sitting on wood to dry, had them wrapped a few days, another batch just sat on a screen to dry from top and bottom. Most everything I made wobbles now. I was told to stick it in plastic to dry. But I also read to keep letting air get to it from both sides. It all is drying inside our house. What is the best way to dry clay so it does not warp and how long does it take to dry? I just started out and can't seem to get it right😟

[bciskepottery]

Eliminating warping starts with how you roll out your slabs -- slab roller, rolling pin? The key is to not bend the slab. When I use a slab roller, I take a piece of wallboard that serves as my wareboard and place it on top of the rolled out slab, then flip the canvas (I use slab mats)/clay/wallboard over and then remove the canvas. Same for rolling with a rolling pin. Then, you can cut out your pieces and remove the excess around them. Let them dry on the wallboard, covered with plastic to start, them without. No need to pick them up and rearrange them in nice rows. When they are leatherhard, you can pick them up to clean edges, drill holes for ribbons, etc. Avoid handling/picking up the items until they are leatherhard. Handling when pliable gives your clay "memory" that results in warping. Let the dry slowly. You can sprinkle a little cornstarch on your wareboard to reduce the clay from sticking to the surface.

[Joseph Fireborn]

If it is drying in your house there is a good chance it has very low humidity which is causing it to rapidly dry. If I take pots in from the garage to the house they dry 2-3x faster because of the controlled climate. What Bruce said will fix all those problems of controlled climate low humidity.

[glazenerd]

Heidi:

I do not see a problem with the clay you are using: it is grogged: which is better suited for tile. I am not a big fan of wallboard because it draws moisture too rapidly from the clay. However, if you are doing tile/ornaments occasionally; then it is a cheap way to get the job done. However, if you plan on doing tile/ornaments on a regular basis I would recommend brazilian luan: $40 for a 4 x 8 sheet. I bought 10 sheets- 3 years ago, use them on a weekly basis: and have not thrown out any. I did cut them into 2' x 4'  sections to go through my slab roller.  "Assuming" you are slab rolling: keep in mind that the density on the outside edges is different than the density towards the center. So I always stay 2" away from the sides minimum, and 4" away from the ends when cutting my tile. Place your clay in the middle and roll in each direction: not just one direction. This will keep the density of the clay more uniform.

I place my board under the clay when I roll: then I do not have to flip it. I keep a minimum of 1" space between the tiles when I cut, which allows air to pass around all four sides. Allow the clay to dry to a leather hard state: the humidity in your house will affect the drying time. This is the point where you have to "learn" your clay: how fast it reaches a leather hard state. The thing to watch for is the corners; when they begin to slightly curl (barely begin to lift off the board) then it is time to cover them with a second piece and weight them. You can use a kiln shelf, or anything that will put just enough pressure to keep them flat. Let them sit a minimum of 24 and up to 48 hours before you uncover them. Again, you have to learn your clay to determine the length of time they need to remain covered. If you decide to use the brazilain luan: they will release themselves from the board within 10-12 hours once you uncover them pending temp and humidity.

Make a couple of 4 x 4 tiles and run the cycle until you learn your clay. By which I mean, roll them out, watch the ends, cover them, and then uncover them. Once you  roll them out- check them at 12hrs, then 16hrs, 24hrs until you figure out the time the edges begin to lift from the board.. Then cover them, then check them 24 hrs- 28hrs-32 hrs until you learn the time to uncover them. Your biggest issue is "learning" how your clay reacts and dries in "your" house.

Nerd

[Heidi1]

Thank you for all the help and advice!