1 ) Uneven shade:
The reason for uneven shade are :
i.
Faulty liquor movement
ii.
Faulty fabric movement during naphtholation
iii.
Improper naphtholation
iv.
Improper hydroextraction
2 ) Naphthol Migration:
The naphthol in fabric goes to base solution of the bath and
reacts with base there other than in the fabric. This is called naphthol
migration. This occurs due to:
i.
Improper selection of naphthol
ii.
More moisture in fabric
3 ) Slow coupling reaction:
The reasons for slow coupling reaction are:
i.
Improper selection of base to mix with naphthol
ii.
Wrong range of pH in bath, i.e. more
acidity.
4 ) Affinity of base towards cellulose:
Azoic base should have affinity towards naphthol. But
sometime it shows affinity towards cellulose. This hampers deing.
5 ) Blinding effect:
In case of rayon dyeing a blinding effect may occur, due to
i.
Presence of alkali during naphtholation
ii.
Improper value of pH
iii.
Presence of alkali in coupling bath.
This blinding effect may be presented by using alkali binding
agent (e.g. alum)
6 ) Pigment on fibre surface:
The reason for this are:
i.
Unfixed dye on fibre surface
ii.
Improper washing after dyeing
This can be prevented by:-
i.
Using binding agent for alkali
ii.
Curing process.