Batt Wash Defect in Ceramics: Causes & Analysis

Batt Wash Defect in Ceramics: Causes & Analysis

Batt wash defect occurs when alumina batt wash residue is found on the surface of the glaze on a ceramic product. This is similar to a clay bits defect but the material causing the problem is alumina batt wash instead of clay.

What is Batt Wash?

Batt wash is a material made from alumina that is applied to the surface of kiln furniture such as shelves and bats. It is used to prevent the ceramic products from sticking to the kiln furniture during the high-temperature firing process. Without batt wash, the melted glaze can bond to the kiln shelf, causing damage to both the product and the kiln furniture.

How Does Batt Wash Become a Defect?

Batt wash defect happens when loose alumina particles from the kiln furniture fall onto the glazed surface of the ceramic product during firing. This can happen because:

• The batt wash on the kiln shelf is old, cracked, or applied in thick uneven layers that can flake off during firing
• The kiln furniture is not cleaned properly before applying fresh batt wash
• The batt wash is not applied correctly or has dried unevenly, making it loose and easy to flake

When these alumina particles land on the glaze surface during firing, they get embedded in the melted glaze. After cooling, they appear as white or rough spots on the surface of the ceramic product.

How to Prevent Batt Wash Defect

• Clean the kiln furniture regularly and remove old batt wash before applying a fresh coat
• Apply batt wash in a thin and even layer to prevent flaking
• Inspect kiln furniture before each firing to check for loose or cracked batt wash
• Replace damaged kiln furniture that has poor surface condition

Impact on Product Quality

Batt wash particles on the glaze surface create rough spots and white patches that affect the appearance of the ceramic product. Products with visible batt wash defects are usually downgraded or rejected in quality inspection.