How to make a clay shrinkage test bar

Prepare the bar from the same clay batch and at a moisture level similar to the intended work. Mark two fine durable lines at a known distance, ideally 100 mm, without cutting deeply into the sample.

Procedure

1. Prepare the bar from the same clay batch and at a moisture level similar to the intended work. Mark two fine durable lines at a known distance, ideally 100 mm, without cutting deeply into the sample.
2. Measure it while wet, when fully dry and after each relevant firing. Record temperature, witness cone, kiln position and clay batch.
3. Do not rely on one bar. Repeat the test when the supplier, colour, thickness or firing schedule changes.

What to record in CeramikaTo

• Work or sample code and date.
• Material, batch, cone, schedule and position.
• Observation separated from hypothesis.

Common mistakes

• Changing several variables at once without a control sample.
• Missing batch, cone or kiln-position information.
• Treating an estimate as a guarantee.