Never Assume: Always Test
The surface of a pot can look and feel bone dry while the interior or base still holds significant moisture. These tests and habits will keep your kiln loads safe.
The Cheek Test
Hold the pot near your cheek or inner wrist (skin that is sensitive to temperature). If any part of the pot feels cooler than body temperature, moisture is still present. The evaporation of water pulls heat from the clay surface, creating a detectable chill.
The base is the last part to dry. Always test the base specifically.
The Colour Test
Bone dry clay is uniformly light and chalky. Any darker patch (even subtle) indicates retained moisture. Compare the pot to one you know is dry.
Safe Drying Practices
- Never rush drying with artificial heat like a heat gun or placing the pot next to a kiln that is cooling. Rapid uneven drying causes warping and cracking.
- Slow and even is always better: Room-temperature drying in a space with moderate airflow.
- Thick-walled pieces need more time: A teapot body or a heavily trimmed form may need 2–3 weeks of drying even when it feels dry on the outside.
- Pots that have been sitting in a humid studio may re-absorb atmospheric moisture. If in doubt, leave them longer.
The Final Insurance
If you are ever unsure whether a piece is truly bone dry, put it in the kiln but run a very slow early phase (called candling) at a low temperature for several hours before ramping up. This gently drives out any remaining moisture. We cover this fully in the Candling topic.
Risk Triage Rule
If you are uncertain:
- Thin form: extend air-dry and re-test
- Medium form: add longer candling
- Thick form: delay firing and dry longer
Conservative decisions protect the full kiln load.
Explore More
The risk of steam explosions in the kiln is a specific case of thermal shock, where rapid temperature changes cause catastrophic stress in a material. For more on the types of clay bodies and how their porosity affects drying, the Wikipedia article on earthenware covers the characteristics of low-fired clays that are especially sensitive to retained moisture.
