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Crocking is the transfer of colour by rubbing from one coloured textile material to another.
Dark shades are more likely to crock than light shades. Printed fabrics more often crock easily than dyed fabrics because most of the dye on the printed fabric is more on the surface but but not inside the fabric as with the dyed fabric. A wet fabric crock easily compared to dry fabric because the moisture present will assist in removing dye.
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Figure of Crocometre
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Colourfastness to crocking is especially important for fabrics used for apparel and upholstery.
The device used for this test is crock metre.
This test determines whether or not colour may be transferred from the surface of the dyed textile materials to other surface by rubbing.
Two specimens are used for this test, one each for the dry and wet tests.
- Place the test specimen on the base of the crock metre so that it rests flat on the abrasive cloth with its long dimensions in the direction of rubbing.
- Special spiral wire clip will hold the test square in place.
- Now the covered finger of the crokmetre is lowered on to test specimen and is made to slide back and forth 20 times by making ten complete turns of the crank at the rate of one turn per second.
Evaluation method for Transfer of Cloth:
The amount of colour transferred from the specimen under examination can be evaluated by means of AATCC chart for measuring transference of colour.
Classify dry and wet crocking fastness of coloured specimens separately as follows.
Class 5: negligible or no colour transfer.
Class 4,3,2,1 as colour transfer equalent to row 4,3,2,1 on the AATCC chart.
To test the fastness to crocking without using crock metre rub dry and wet samples against a white cloth. If the colour does not rub-off on the white cloth. If the colour does not rub off on the white cloth, the colour is fast to rubbing or crocking.
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