Damp Box

What it is

The window for trimming a pot is short. Too wet and the wall deforms under the tool; too dry and the clay crumbles instead of cutting. A damp box widens that window from a few hours to several weeks by holding the surrounding air at close to 100% relative humidity.

The simplest damp box is a plastic storage bin with a damp plaster slab in the bottom. The plaster reservoir releases moisture slowly and evenly; the lid keeps it in. Commercial versions add a rack to keep work off the wet slab, and some potters add a hygrometer to watch the internal reading.

Damp boxes are also the correct place to store handles before attaching them, to hold a leather-hard pot while a second stage is added, and to slow the drying of anything large enough to crack. Combined with a good plastic wrap, a damp box effectively pauses the drying clock.

How to use it well

• Recharge the plaster slab weekly by soaking it, then letting it drain before closing the lid.
• Write the date on every pot you store; it is easy to forget how long a piece has been resting.
• If mould appears, a light spray of vinegar on the pot kills spores without affecting the clay.
• A damp box plus a bin bag is the most reliable way to dry a large coil-built form without cracking.

Safety notes

• Stagnant damp boxes grow mould; wipe the interior with dilute vinegar between projects.
• Never seal greenware that is still dripping wet — condensation drips and ruins the surface.

Compatible materials

Clay bodies

• All bodies
• Especially useful for hand-built and large work

Glazes & surface

• Not applicable — storage

Where it sits in the process

Preparing and homogenising clay before forming.

Wedging  Clay & Preparation  Entry tier

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