Colour Fastness to Rubbing || Fastness Testing to CROCKING (Wet and Dry Rubbing Crockmeter) [বাংলা]

COLOR FASTNESS TO CROCKING TEST (WET AND DRY RUBBING)
“Crocking” is an industry term referring to a transfer of a colorant through rubbing. The crocking test determines the resistance of textile colors to rubbing off and staining other materials. A fabric with poor color fastness could rub colorants off on consumers, furniture, other textiles or miscellaneous items.

Color Fastness to rubbing is a type of textile Color Fastness inspection, and it is generally one of the most common inspection types in the textile trade. It refers to the ability of the color of textiles to resist friction, and that is both dry friction and wet friction.

The test is quite sensitive and for getting consistent result, it is necessary to use
• Standard crock meter
• Cloth,
• Maintain uniform pressure for applying rubbing strokes and number of strokes.

Test template of Color Fastness to rubbing:
The model generally followed to test for Color Fastness to rubbing textiles to fix the specified size textile sample on a friction tester platform with a clamping device. Then, rub it with a dry friction cloth and a wet friction cloth, respectively. In the end, the degree of staining of white cloth is used as the evaluation basis, and it is graded against a set of standard Color Fastness to staining gray scales.

The gray sample card used to determine the fastness rating is divided into five grades; the higher the grade, the better the rubbing fastness. A fabric with poor rubbing fastness could rub off dyes on basically anything, and that is undesirable for end-users.
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Dry friction test:
Put a piece of (50×50) mm rubbing cloth (standard white cotton cloth) on the rubbing head under standard atmosphere (temperature 20℃±2℃, humidity 65%±4%), humidity control for more than 4 hours. Make sure the direction of the friction cloth is consistent with the movement direction of the friction head. Adjust the running speed of the rubbing head to one reciprocating friction cycle per second, ten times, which amounts to a total of 10 cycles of friction. The friction stroke or reciprocating movement on the sample should be (104±3) mm, and the applied direction is vertically downward. This downward force should be (9±0.2) N. After the entire ten cycles are completed, remove the friction cloth, adjust the humidity (over 4 hours), and remove any excess fibers on the friction cloth that may affect the rating.

Wet friction test:
Immerse the weighed piece of friction cloth completely in distilled water, take it out, and reweigh the friction cloth to ensure that the moisture content of the friction cloth reaches 95%-100%. Then apply the same operating method as in the dry friction test.

Textile rub resistance test rating:
After performing the above test process, we need to take the moistened friction cloth to the grading room and place it in the standard light source box, then use the gray sample card to evaluate the staining grade of the friction cloth.
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Comparison of common standards of textile Color Fastness to Rubbing:

ISO 105 X12 and AATCC 8 are the primarily standards for measuring color fastness to crocking. The standards are partly equivalent and largely similar in their test methods.


ISO 105 X12 and AATCC 8

In both the ISO 105 X12 and AATCC 8 test methods, the test samples are rubbed with a dry rubbing cloth and then a wet cloth. Both methods use a machine known as a “crockmeter” to rub the fabric. The crockmeter has a “rubbing finger” which the lab technician rubs across the fabric by turning a mechanical lever. The rubbing fingers vary in size for pile fabrics and other textiles. The rubbing direction can also vary based on the type and design of the fabric. But the crockmeter typically rubs the fabric in the warp and weft directions separately. The direction is particularly important for striped or pattern fabrics for which results can vary. The staining of the rubbing cloth is then assessed using the Grey Scale for Staining. Many textile importers will accept a grade 4 rating for dry rubbing and grade 3 rating for wet. Color fastness to wet rubbing is typically lower than for dry rubbing for most fabrics.

ISO 105 X12 and AATCC 8 vary mostly in the amount of water used to wet the cloth rubbed on the test specimen. The amount of water is calculated as “wet pick up”, or the amount of fluid by percent weight picked up by the fabric. ISO 105 X12 requires the cloth be wetter than that following the AATCC 8 standard.
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Factors affecting Color Fastness to rubbing
• Fabric surface morphology
• Fabric structure
• Reactive dye chemical structure
• Reactive dyeing degree
• The effect of softener