Unit-5

Colour Fastness of Dyed & Printed Materials

D.Praveen Nagarajan

Grey Scale

• Grey Scale is a tool used to appraise the colour fastness of dyed and printed material to different agencies.

• Grey scale is a small rectangular plate like tool with standard fading patterns of different degrees of fading.

• There are two separate grey scales one for measuring change in colour of the coloured material and other one for measuring degree of staining on adjacent white fabrics stitched to the dyed fabric during fastness testing.

• For both criteria, the ratings will range from 1 to 5 with an increment of 0.5.

• For light fastness the above grey scales are not used for final rating.

• A different technique is used and the rating varies form 1 to 8.

Colour fastness to washing

• AimTo determine the colour fastness of textile material of any

composition to the action of soap solution or soap and soda ash combination.

PrincipleA specimen of textile in contact with pieces of specified

adjacent fabrics is mechanically agitated in soap solution or soap & soda ash solution, rinsed and dried.

The change in colour of the specimen and the staining of the adjacent fabrics are assessed with the help of standard grey scale.

• Indian Standards Institution (ISI) and ISO have prescribed five different test methods to test the wash fastness.

• Each one differs from other in terms of increasing severity of treatment.

Apparatus required

• 1) Launder ‘O’ meter• 2) Grey Scale

ProcedureTwo adjacent fabrics, each measuring 10x4cm one piece made of the same kind of

fibre as that of the textile to be tested the second made of the fibre as indicated below.First piece Second PieceCotton WoolWool CottonSilk CottonLinen Cotton or viscoseViscose WoolAcetate ViscosePolyamide Wool or viscosePolyester Wool or cottonAcrylic Wool or cotton

Reagents required1) Soap solution – 5 gpl2) Soap and soda ash solution containing 5 gpl

soap and 2 gpl soda ash

Preparation of test samplePlace a specimen of 10 cm x 4cm between two

adjacent fabrics as prescribed above and sew along all 4 sides to form a composite specimen.

Prepare atleast 3 such specimens.

ProcedurePlace the composite specimen in one of the

containers of Launder-o-meter and add the soap or soap and soda, solution as per the test number chosen.

Conditions of treatment for all 5 test methods have been tabulated.

Conditions for ISO wash fastness test methodsIn all the methods material : liquor = 1:50

Sl.No Wash fastness test method

Chemicals to be added

Stainless steel balls to be added

Temp Time

1 ISO Test 1IS : 687 -1979

Soap – 5 gpl Nil 40 +/-2’C 30 min

2 ISO Test 2IS : 3361 -1979

Soap – 5 gpl Nil 50 +/-2’C 45 min

3 ISO Test 3IS : 764 -1979

Soap – 5 gplSoda ash – 2 gpl

Nil 60 +/-2’C 30 min

4 ISO Test 4IS : 765 -1979

Soap – 5 gplSoda ash – 2 gpl

10 95 +/-2’C 30 min

5 ISO Test 5IS : 3417 -1979

Soap – 5 gplSoda ash – 2 gpl

10 95 +/-2’C 4 hours

After treating the test specimen under any one of the above test methods for the prescribed time, rinse the specimen twice in cold water and then in cold running water for 10 minutes.

Remove the stitching and dry at a temperature of 60’C.

Evaluate the change of colour of the treated test specimen and degree staining of the two adjacent fabrics with the help of grey scales.

Repeat the test with remaining specimens.

ReportThe report shall includea) Type of the materialb) The numerical rating for change in colour of the test piece

ranges from 1 to 5.1 – indicating very poor fastness and 5 indicating excellent

fastness properties.c) The numerical rating for staining of the two adjacent

fabrics ranges from 1 to 5.5 – indicating no staining of adjacent fabric and 1 indicating

complete staining of adjacent fabric.

Colour Fastness of Textile of Rubbing

AimTo determine the colour fastness of textile

materials to rubbing off and staining other materials in both dry and wet conditions.

SampleTwo pieces each of 14x5 cm one in warp

direction and other in weft direction are selected and kept for dry rubbing.

Similarly, another set of two specimens are selected for wet rubbing

Apparatusa) Crock meterb) Grey scalec) Undyed cloth pieces each 5x5 cm size

bleached cotton fabric.

Procedure1. Dry RubbingTake a test specimen and fix it to the rubbing device.Fix a piece of the dry undyed fabric over the end of the finger

of the rubbing device and rub it to and fro in a straight line along a track 10 cm long on the test piece 10 times in 10 seconds with a downward force of 900 g on the finger.

Repeat the above test for the other specimens.Evaluate the degree of staining of the undyed fabric with the

help of grey scales and assign rating.

ii) Wet RubbingTake a test specimen and fix it to the rubbing device. Soak a piece of undyed fabric in distilled water and squeeze it by passing

through two rubber rolls so that it contains its own weight of water.Fix the wet undyed fabric on the finger of the rubbing device and rub it in

a straight line along a track of 10 cm long on the dry test specimen 10 times in 10 seconds with a force of 900 g on the finger.

Then dry the undyed fabric at room temperature.Repeat the test for the other specimen also.Evaluate the degree of staining on undyed fabric using grey scale and

assign rating.

ReportThe report shall include,a) The numerical rating for staining of the undyed fabric used in

dry rubbing.b) The numerical rating for stainning of the undyed fabric used in

wet rubbing.The above rating ranges from 1 to 5. 1 represent very poor rubbing fastness leading to maximum

staining and 5 represents excellent rubbing fastness with no staining reported.

In general, the wet rubbing fastness is reported to be poor for any dyeing, compared to dry rubbing.