Principle of Testing
A sample of textile in the form of fabric is in contact with a piece of specified adjacent fabrics in mechanically agitated in a soap or soap-soda solution, rinsed and dried. The change in colour of the specimen and the staining of the adjacent fabrics are assessed with a gray scales.
The sample should be a representative sample or one agreed to between the buyer and the seller.
A suitable mechanical washing machine with the following requirements to be used.
- Water bath containing a rotor by means of which contains 500ml capacity is rotated at a speed of 40+ revolutions/ min. The containers may be stainless steel or glass.
- Means of thermostatically controlling the temperature of the water bath so as to maintain the temperature at an accuracy of 40 + 2oC.
The washing fastness of the dyed textiles may be performed under 5 different standard test conditions as shown in the table below.
|Washing Test No.||Second-Adjacent fabric||Soap solution conc.||Soda ash conc.||Tempof test o C||Time of treatment||Steel balls of 6mm dia||M : L ratio||IS Test Number|
|1.||Wool 10x4cm||5 g/l||NIL||40 + 2oC||30 min.||—||1 : 50||IS687:1979|
|5g/l||NIL||50 + 2oC||45 min.||—||1 : 50||IS3361:1979|
|3.||Wool 10x4cm||5 g/l||2 g/l||60 + 2oC||30 min.||—||1 : 50||IS764:1979|
|5 g/l||2 g/l||95 + 2oC||30 min.||10||1 : 50||IS765:1979|
|5.||Viscose 10x4cm||5 g/l||2 g/l||95 + 2oC||4 hrs.||10||1 : 50||IS3417:1979|
Table 3.6 washing fastness recipe
As per the specifications, the test specimens of size 10 x 4 cm is taken. Then two pieces of adjacent fabrics of 10 x 4 cm( as per the given specifications and fabrics type) are taken. Then a composite specimen is prepared by keeping the test specimen in between the two pieces of undyed cloth and stitched around at the four edges as shown in a figure.
Necessary soap soda solution is prepared as per the M :L ratio 1 :50. The specimen is kept in the container of the washing machine with the soap or soap soda solution. The containers are closed and washing is carried for 30 minutes with 40 o C. Remove the composite specimen, rinse it twice in cold water and cold running water for ten minutes.
Remove the stitches along the two long sides and one short side. Open out the composite specimen and dried it in hot air oven at 60 o C or at room temperature.
Evaluation of colour fastness to washing
The composite specimens containing the specimen is evaluated with the gray scale for a. Change in color b. Staining the gray scale consists of 9 pairs of standard grey chips, each pair representing the difference in colours (shade and strength) corresponding to the numerical fastness rating. This rating may be described in qualitative terms as follows.
|4 – 5||Very Good to Excellent|
|3 – 4||Good to very good|
|2 – 3||Fair to Good|
|1 – 2||Poor to fair|
Table 3.7 gray scale rating
Similarly another set of grey scale for staining