Stripping becomes necessary when uneven dyeing occurs. By stripping azo groups (-N=N-) brom the dye is removed.
I) Partial stripping methods:
Partial stripping is obtained by treating the dyed fabric with dilute acetic acid or formic acid. The commanded conc. is betn 5 to 10 parts glacial aid or 2.5 –10 parts of formic acid per 1000 parts of water
Recipe: Glacial acetic acid = 5 – 10 parts
Water --> 1000 parts
OR
Formic acid --> 2.5 to 10 parts
Water --> 1000 parts
Temp --> 70-100oC
Time --> Until the desired shade is obtained.
Process- The goods are entered and temp is raise to 70-100oC and the treatment is continued until the shade has been reduced to the desired amount thoroughly washing is then necessary to remove the products of hydrolysis.
II) Full stripping:
For complete stripping, the goods are firstly treated with Na2S2O4 Sodium hydrosulfite at boil. Then treatment is done at room temperature for 30 min.
