Clay & Shrinkage

Drying Time Predictor

Estimate how long a ceramic piece will take to dry based on wall thickness, humidity, and airflow.

Reviewed by ClayCalc Editorial · Updated

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Results

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Enter your measurements above and click Calculate.

How Drying Time Is Calculated

Drying time is calculated using a base rate of 2.5 hours per millimeter of wall thickness at standard conditions (50% RH, still air, stoneware). This base rate is then multiplied by four adjustment factors:

  • Humidity factor: Every 10% above 50% RH slows drying proportionally. At 80% RH, drying takes approximately 40% longer.
  • Airflow factor: Forced air (fan) cuts drying time by more than half. A completely enclosed space increases drying time by 30%.
  • Clay type: Porcelain (fine particles, high plasticity) takes 50% longer than earthenware at identical conditions.
  • Covered with plastic: Slows drying by 2.5× — critical for preventing differential drying in thick pieces.

The result is given as a range (±40%) to account for the high variability in real studio conditions.

Method & review note

About this calculation

Uses measured dimensions or weights and a stated arithmetic model. Clay and forming method vary, so production decisions should use test pieces from the actual body and firing.

Reference: Digitalfire — Drying Shrinkage. See the editorial methodology for testing, precision and corrections.

Input handling: Values are sent to the ClayCalc server for this request and are not written to the application database.

Read the Clay Shrinkage Test

Frequently Asked Questions

Why does porcelain take longer to dry than earthenware? expand_more
Porcelain has very fine, closely packed particles that hold water strongly and release it slowly. Earthenware has more open particle structure and dries faster, but is also more prone to cracking from differential drying.
What is the safest drying method? expand_more
Cover fresh work loosely with plastic for the first 24–48 hours, then uncover progressively. This slows initial drying and equalizes moisture throughout the piece, dramatically reducing crack risk.
Can I use a dehumidifier to speed up drying? expand_more
Yes, but carefully. Reduce humidity gradually rather than drastically. Sudden drops in humidity dry the outside faster than the inside, creating dangerous stress differentials that cause cracking.