Shrinkage Test for Ceramic Body: Methods & Analysis

Shrinkage Test for Ceramic Body: Methods & Analysis

The shrinkage test is performed on both clay raw materials and production slip. For incoming raw materials, once the deflocculant demand is determined, the same slip is used to check the shrinkage. This test helps in understanding the plasticity of the clay: the higher the plasticity, the higher the shrinkage.

Types of Shrinkage

Three types of shrinkage are calculated:

• Dried shrinkage

• Fired shrinkage

• Total shrinkage

Test Procedure

To perform the test, a 12 cm bar is cast. After demoulding the bar from the mould, a 10 cm length (L0) is marked on the bar using a Vernier caliper. The bar is allowed to dry in the atmosphere for 6 hours and then kept in a dryer at 110°C for 20 hours. The length between the two marked points is measured (L1). The bar is then fired in a kiln, and the length between the two points is measured again (L2).

Shrinkage Calculation Formulas

Shrinkage is calculated using the following formulas:

• Dried Shrinkage (%) = [(L0 - L1)/L0] × 100

• Fired Shrinkage (%) = [(L1 - L2)/L1] × 100

• Total Shrinkage (%) = Dried Shrinkage (%) + Fired Shrinkage (%)

Importance and Applications

This test is essential for understanding the dimensional stability, plasticity, and overall quality of the clay materials used in production. Additionally, it helps in modeling new products by maintaining the shrinkage in the body for dimension allowance, ensuring that the final products meet the desired specifications and dimensions.