Shaping the Slab

The most powerful technique with soft slabs is draping: letting gravity and a mold do the shaping for you.

Draping Into a Mold

A hump mold is something you drape clay over (like an upturned bowl). A slump mold is something you drape clay into (like a bowl right-side up).

• Lightly dust the mold with cornstarch or use a thin layer of newspaper so the clay does not stick.
• Lay the slab gently over or into the mold.
• Smooth it down with your hand or a rib tool, working from the center outward.
• Trim the excess with a needle tool.

Wrapping a Cylinder

You can also wrap a soft slab around a cardboard tube to create a cylinder:

1. Roll the slab around the tube.
2. Score and slip the two edges where they meet.
3. Join them firmly and smooth the seam.
4. Remove the cardboard once the clay firms up slightly (an hour or so).

The Catch

Soft slabs are, well, soft. They can sag, stretch, and distort if you manhandle them.

• Support the slab from underneath when lifting.
• Move quickly: you have a limited window before it becomes too stiff or too dry.
• Fingerprints show up easily, so use a smooth rib to refine the surface.

Pro Tip

If the slab is too soft and floppy to work with, lay it on a dry board for 10 minutes to stiffen it just slightly. You want it flexible but not so soft it tears under its own weight.

Distortion Prevention Checklist

Before final shaping:

• Support the slab from underneath when moving.
• Avoid lifting from a single edge or corner.
• Smooth compression marks early with a rib.
• Trim while supported on mold or board.

Small handling errors at this stage create permanent warps.

Dig Deeper

The hump-and-slump mold technique is widely used in industrial ceramic manufacturing to produce consistent shapes at scale. The cornstarch release agent works because it creates a thin barrier that prevents adhesion between the clay and the mold surface.