Determination Of Wash Fastness Of A Dyed Sample
The resistance to the loss of colour of any dyed or printed material to washing is referred to as its wash fastness. If the dye molecules is not penetrated through the inner structure of fibre polymer system or have not attached to the fibre with strong covalent attractive force then poor wash fastness results.
ISO recommended five test methods for washing fastness measurement. The first three methods are done in same procedure at different temperature. The last two methods are also same in procedural works but differ in time duration.
- SDC recommended multi-fibre fabric
- Grey scale for colour changing
- Grey scale for staining
- Colour matching cabinet
The tested sample is prepared as below:
- A 10 × 4 cm2 dyed sample to be tested is taken.
- Another two pieces of fabric sample which are scoured, bleached but unfinished sample of 5 × 4 cm2 sample is also taken.
- One of the unfinished samples will be of same fibre of the tested sample. Another sample’s fibre type will depend on the type of fibre constitute the tested sample. Here we tested cotton sample and the two other fabric is cotton and multi fibre fabric.
- Now the tested sample is placed between the unfinished samples covering 5 × 4 cm2 area and stitched at the four edges.
Washing solution preparation:
After preparing the sample for washing it is impregnated in the following solution and in following parameters:
|High grade soap solution
Free alkali calculated as Na2CO3 = 0.3%
Free alkali calculated as NaOH = 0.1%)
|Material : liquor||1:50|
The time barrier and temperature of test is as below:
|Test method||Temperature||Time||Steel boll no||Reagents|
|ISO – 1||40º ± 2ºC||30 min||No||Only soap (5 g/lit)|
|ISO – 2||50º ± 2ºC||30 min||No||Only soap (5 g/lit)|
|ISO – 3||60º ± 2ºC||30 min||No||Only soap (5 g/lit)|
- We Rinse the samples twice in cold distilled water.
- Then we Wash these in running cold water for 10 minutes.
- Now we Squeeze the samples and remove the stitching from two long side (5 cm sides) and one short side (4 cm side) leaving another short side stitching.
- Finally we dry these in air at temperature not above 60ºC.
Interpretation of result:
- Change in colour – From uncovered portion of sample change in colour is compared with the untreated dyed sample on contrast basis with the help of grey scale. The grade of contrast in grey scale is the wash fastness of the sample.
- Staining – The staining is measured by staining grey scale. Here the staining of unfinished sample is compared with the original untreated unfinished sample from staining grey scale on the basis of contrast.
|Test method||Color change in shade||Staining in wool|
|ISO – 1||4 to 5||4 to 5|
|ISO – 2||4 to 5||4 to 5|
|ISO – 3||4||4|
Interpretation of Grade:
The wash fastness of the dyed sample in colour change is excellent to good and in staining in wool is also excellent to good.
The sample is tested in ISO method for wash fastness without using machine and high grade solution of soap. The fastness found is excellent to good found for both fading and staining.