A number of variations are used in testing the fabric for fastness of colour to washing. These occur because there are differences in the washing procedures for different fibers and there are also variations in the washing procedure for the same fibre.
The important elements to be considered in the washing tests are as follows.
Washing temperature used for washing has a very great affect on colour. The dye is loosened from the fabric by the action of hot solution.
Time taken for washing is also an important aspect. Washing should be done quickly because the longer washing time, the greater the amount of colour that comes out.
The additions to the bath also affect the test results. The alkaline, sodium carbonate, intensifies the washing action, making it more severe on the colour.
Mechanical action to which fabrics are subjected during laundering must be included in the washing test.
The proportion of liquid to the amount of material washed is also important in laundering.
The machine used for testing colour fastness to washing is launder-o- meter.
A test specimen of 10*4 cm should be prepared to test the colour fastness to washing.
The test specimen is prepared by sandwiching dyed sample with white cotton fabric on one slide and silk fabric on other slide.
The test solution need to be prepared by dissolving 5 gms of neutral soap in one liter of distilled water.
The specimen should be placed in a container and the necessary amount of soap solution previously heated to 40+_ 20c should be added, so that the standard liquor to material ratio is maintained.
The samples need to be treated for 30 min at 40 +_2 0c in the launderometre.
After 3 min the specimen is removed from the launderometre and should be rinsed well in cold running tap water for 10 min.
The stitches should be removed on all the 3 sides except one short side and dried in air in temperature not exceeding 600c.
The colour change and colour staining would be evaluated by colour matching spectrometer.
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