How thick should a clay slab be?

Short answer: roll 4–5 mm for cups and boxes, 5–6 mm for bowls and plates, and 6–8 mm for large pieces and platters. Tall vases work at 6–7 mm with internal reinforcement.

Too thin and a slab warps or breaks; too thick and the piece becomes heavy and dries poorly. Thickness also changes the calculation of your template. Here is how to choose it well.

Slab thickness by piece

How to roll an even slab

Place two guide sticks of the thickness you want on either side of the clay, and let the rolling pin rest on them: the slab can’t get thinner than the sticks. Roll from the centre outwards, then lift the slab, turn it over and roll in the other direction, so it doesn’t stick and the clay is compressed evenly. Check the thickness at the edges and in the middle before you cut.

Why thickness changes the template

A 5 mm slab does not roll like a sheet of paper. For a cylinder, the cut length is calculated along the neutral axis, the middle of the thickness, rather than the outside diameter. On a box, every corner consumes one or two thicknesses.

How the tool handles it

On cylinders, cones and angles, the tool adjusts the radii and the developed perimeter to the slab thickness you enter, so the edges meet where they should. You give it your finished dimensions and your thickness; it does the rest.

Create a template that includes your slab thickness

FAQ

How thick should clay be for a mug?

4–5 mm: thick enough to hold its shape and take a handle, thin enough to stay light in the hand.

What happens if a slab is too thin or too thick?

Too thin, it warps or breaks while you assemble and fire it. Too thick, the piece is heavy and dries poorly, which raises the risk of cracks.

Read next: print a ceramic cup template · make a slab-built ceramic bowl