Slab Tips & Tricks
In the studio I often get asked about how to keep flat pieces from warping, like the chessboards. Anyone that has worked with clay understands the frustration of getting your piece perfect while wet, only to find that perfectly formed piece warped while drying or firing.
Clay has memory. In the same way a child has experiences that form their behaviors later in life, the motion and manipulation that the clay experiences while wet, can affect the shape of the clay when drying and firing (yes, I like to pretend the clay is alive!). When throwing on the wheel, the movement and distribution of the clay is kept relatively consistent (though there is plenty of opportunity during later stages to mess this up), but when working in slab, much more care must be taken when handling the clay.
Below are some tips and tricks I used to sustain optimum flatness!
STRETCH CLAY EVENLY IN ALL DIRECTIONS
After wedging your clay, you'll need to flatten it out before working it with a slab roller. I use a technique of throwing the clay on the wedging table at a 45 degree angle, almost like an underhand toss. The clay will stick slightly to the plaster board and will stretch from the force of your toss. Be sure to turn the clay as you do this. You can also use a rolling pin, but again, rotate the clay every roll. This will ensure that the clay shrinks evenly. If you only flattened in one direction and then cut out a square, you will end up with more of a rectangle.
GO SLOW, KEEP ROTATING
It might take more time, but move the slab roller down incrementally so that you pass the clay through at least 5 more times. Between rolls, flip the clay to keep it from sticking to the canvas and be sure to continue to rotate! If you need your slab to be a certain size or shape, it might take a couple of tries to figure out what shape and weight you need to start out with to end with the right size.
KEEP IT FLAT
When the right thickness, do everything possible to keep the slab as flat as possible. I use two drywall boards to help me flip the clay off the canvas without bending it. To get the clay onto the bottom board, I hold the board even with the edge of the table and quickly slide the canvas from table to board. I then lay newspaper over the clay and top with the 2nd board. Put one hand on the top of your slab sandwich and one hand on the bottom. Flip the whole thing and set down on a table. Remove the board, peel off the canvas slowly, and now you're ready to start working!