1.1 ,This test method covers an index method that enables the evaluation of fluid loss properties of a clay mineral film deposited on a filter paper from a 6 ,% solids slurry of clay mineral at 100-psi (kPa) pressure as a measure of its usefulness for permeability or hydraulic conductivity reduction in geosynthetic clay liners (GCL). This test method is not applicable for clays with polymers.