Water Absorption Test for Ceramic Fired Products: Methods

Water Absorption Test for Ceramic Fired Products: Methods

Overview

Water absorption is tested for both production slip and clay slip. This test is crucial for understanding the vitrification level in the ceramic body during the firing cycle. In the sanitaryware industry, a water absorption rate of less than 0.5% is typically accepted. This low level of absorption ensures the durability and longevity of sanitaryware products.

Importance of Regular Testing

It is essential to check the water absorption for each batch of slip production to gain a better understanding of the production process. Water absorption results help the production team identify defects based on the readings. For example:

• A sudden decrease in water absorption, combined with warpage in the production, may indicate an issue with the firing process

• A consistent water absorption value coupled with a sudden matte glaze finish may suggest a problem in the kiln's cooling zone

Standards and Variations

Standards for water absorption can vary slightly between countries. For instance, some standards require the use of a vacuum during water immersion, while others do not.

Testing Procedure

For production pieces, samples are collected from multiple locations on the product by breaking it. For slip slurry, broken MOR (Modulus of Rupture) samples or ware page samples can be used.

Step-by-step process:

1. Dry and cool the sample in a desiccator

2. Record the initial weight (W1)

3. Immerse the sample in boiling water for 5 hours

4. Allow it to sit for an additional 12 hours

5. Remove the sample and wipe off surface water with a cloth

6. Record the final weight (W2)

Calculation

Water Absorption (%) = (W2−W1) / W1 × 100