Friday, May 22, 2020

TESTING OF COLOUR FASTNESS TO RUBBING OR CROCKING



CROCKING OR RUBBING FASTNESS TEST:

Rubbing fastness of the fabric:

" The amount of colour transferred from the surface of dyed or printed textile material to other surface by rubbing is called rubbing fastness of the textile material".

Testing of rubbing fastness of coloured textile material:

In the test of colour fastness to rubbing, the test specimen is rubbed with white crock test cloth under controlled conditions. The amount of colour transferred to the white crock test cloth is assessed by comparing with the grey scale.

Testing conditions:

The each test specimen should be conditioned for atleast 4 hours in the atmosphere of 21 plus or minus 1°C and 65 plus or minus 2 % Relative humidity.

Apparatus used:

1 - Crock meter.

2 - Fabric.

3 - Scissor.

4 - Marking pen.

5 - Crock test cloth.



Testing procedure:

The whole test gets completed in below steps:

Dry rubbing:

1 - The white crock test cloth is mounted on the rubbing finger with the help of a clamp.

2 - The test specimen is fixed on the rubbing device by means of acrylic template such that the long direction of the specimen follows the track of the devices. You can
see the below figure:





3 - when the multi - coloured textile is tested for rubbing fastness, the technician should be careful about the position of the specimen in such a way that all colours of the design are rubbed in the test.

4 - If the area of the colour is large, more test specimen should be prepared and individual colour should be assessed separately.

5 - The covered rubbing finger is lowered onto the test specimen.

6 - The main power supply switch is on position.

7 - 10 turn are set into the timer.

8 - Now the power supply switch of crock meter is pushed on. The rubbing finger starts to move to and fro direction.

9 - The machine gets stopped after ten turns automatically.

10 - The white crock test cloth is removed from finger.

10 - Now this white crock test cloth is evaluated for staining with the help of 1 - 5 grey scale and rating is given.  Increase in rating indicates better rubbing fastness.



Wet rubbing: 

All the procedure remains same as dry rubbing except the wetting of white crock test cloth.

It is wetted with water ( wet pick up 65 plus or minus 5 %.

The staining of the rubbing on cotton white cloth is checked.



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