When two fabrics rub against each other, there can be a transfer of colour from one to another. This effect is unacceptable and there must be a test to recognise poor colour fastness and the transfer of colour under these conditions. This is Crocking. Assessment is carried out by making a judgment of the colour evident on the reference crocking cloth and Grey Scales.

Crocking is the method employed to accurately assess the quantity of colour transferred from one substrate to another during a controlled and reference test. The Crocking test is carried out using a set number of “rubs”, using a set rub length, during a set time with a set pressure at the point of rub. For added control it is also necessary to use a reference “crocking cloth” as the rubbing adjacent fabric.

Colour fastness rating is the means of evaluating the change in colour of a substrate and/or the transfer of colour from a substrate to an adjacent reference material, multifibre, during a test procedure. The rating is often evaluated by means of the grey scales and will be report as a grade between 1 & 5, with grade 5 being no visible change. Colour fastness rating will assess colour change and colour staining.