Blown Out Defect in Ceramics: Causes & Analysis

Blown Out Defect in Ceramics: Causes & Analysis

Overview

Blown out is a defect observed in ceramics products, characterized by the presence of a blowout hole in the body. In some cases, this defect also leaves black discolouration on the glaze surface. The primary cause of this issue is contamination burn off in the body, particularly due to organic materials or small foreign particles.

Causes

One major contributor to this defect is the presence of broken plaster pieces or lumps of organic material in the clay body. When these materials burn off during firing, they can create voids or pinholes in the product.

In some cases, the burning of organic contaminants leaves behind carbon residues, which result in black marks on the glaze surface.

Prevention Methods

• Sieving runoff slip and scrap slip to ensure that unwanted particles, including broken plaster pieces, are removed before the slip is reused in the casting process

• Proper air blowing and cleaning of moulds to help eliminate plaster remnants or other contaminants that may mix with the body during casting

• Properly handling scrap materials

• Maintaining clean moulds

Implementing these preventive practices can significantly reduce the occurrence of this defect.