The determination of colour fastness of vinyl coated fabrics against rubbing in both dry and wet conditions is carried out by means of a crock meter. In this test a rectangular test specimen is clamped over a glass plate, which is then given a reciprocating motion in a horizontal plane, while a white cotton abradant fabric mounted over an abrading peg of the specified shape rubs against it under a specified load. The degree of colour transferred from the test specimen to the abradant fabric determines its colour fastness.
This equipment can also be used for the determination of adhesion of prints on vinyl coated fabrics and unsupported flexible PVC sheetings. The rubbing off of the printed pattern gives a measure of the print adhesion of the material.