Why Test for Permeability?
In a foundry test setting, sand permeability is defined as the time required for a controlled air volume to pass through a sand specimen or porous material. Factors that can impact permeability results include grain fineness and distribution, sand type, and moisture. Testing for permeability is critical for a foundry operation because the level of permeability can explain the causes of certain defects that can occur to metal castings. An increase in permeability can lead to penetration-type defects and rougher surface finishes. Despite leading to smoother surface finishes, a decrease in permeability can lead to casting defects such as blows, pinholes, and expansion defects.