Pigment Dyeing – Problems and their Probable Causes
Pigment dyeing is an electrical process whereby the goods to be dyed are given an electrical charge opposite that of the pigment. When the pigment is added to the bath, the opposite electrical charges attract each other , Here garment is beeing charged with Cations which helps to attract the Pigment. As it surface reaction only, hence there are lot of challenges of repeatability of the shade. Even in the same batch garment to garment shade variation is common problem.
Pigment Dyeing – Problems and their probable causes
▪ Uneven/Patchy Dyeing – Probable causes of uneven dyeing could be:
1) Poorly pre-treated garments.
2) Garments are not allowed to wet-out sufficiently before pretreatment
3) Very low liquor ratio during dyeing.
4) High rate of rising of dye bath temperature.
5) Water hardness is high .
6) Bath temperature is higher than room temperature at the beginning of dyeing.
7) Acetic acid added earlier than the dyes exhaustion in dye bath. Generally, dye should be 70-80% exhausted and then acetic acid should be added .
▪ Poor Dye yield – Poor dye yield could be because of:
1) Improper pretreatment.
2) Improper holding time during dyeing cycle.
3) Very high liquor ratio.
4) Low agitation during dyeing.
▪ Dye Spots – Possible Causes are:
1) Acetic acid added early in the dye bath.
2) Dye not properly diluted or stirred before adding to the dye bath.
3) Dye not properly flitered before adding to the dye bath.
5) Dyes have low compatibility with the chemicals
6) Garment not rinsed properly after pretreatment.
