Wednesday, May 3, 2017

Dyeing Defects and Their Remedies

In light of this topic, we can say easily that the dyeing faults may occur not only in dyeing stage but also different types of faults are shown in pre-treatment stage, may also lead to accelerate the dyeing defects which are quite unacceptable in view of dyeing defects. Which are quite unacceptable in view of quality aspects.
dyeing faults
Fig: Different dyeing faults
Dyeing Faults, Causes and Their Remedies:
Here we are representing below the common faults or defects, causes of these faults and their remedies by mentioning pre-treatment stage and dyeing stage:

A. Pre-treatment stage:

1. Single marks:

Causes of single marks:
An area in the cotton fabric not properly singed due to crease formation, this area will appear in darker shades after dyeing.

Remedies of single marks:
  • Resingeing,
  • Color stripping and
  • Then re-dyeing.
2. Bad singeing:

Causes of bad singeing:
Non uniform singeing due to blocking of some flame orifices. This will appear as darker areas when dyed or printed.

Remedies of bad singeing:
  • Resingeing after making flame orifices as proper,
  • Color stripping and
  • Then re-dyeing.
3. Draft stains:

Causes of draft stains:
Yellow stains on the white cloth. This is due to wet cloth being left for relatively longer period of time after bleaching and prior to dyeing. If the cloth is dyed, printed or finished, it will have stains of deeper color shades.

Remedies of draft stains: 

Acidifying the cloth, then washing it before dyeing.

4. Rope marks:

Causes of rope marks:
Frequent longitudinal folds in cloth. This due to high pressure during mangling, when scouring of and bleaching is done in rope from.

Remedies of rope marks:
Stentering the cloth before dyeing. In case of severe folds it is advised to mercerize the cloth.

5. Stains:

Causes of Stains:
Oil, stains, grease stains, rust, water spot and ground stains.

Remedies of stains:

  • Suitable clearing agent to be used.
  • Emulsifiers in case of oil and grease stains, oxalic acid, in case of iron rust and use suitable detergent in case of other stains.
6. Weak or tender areas:

Causes of weak or tender areas:
Area of faded color in dyed cloth these are tendered due to chemical degradation during bleaching.

Remedies of weak or tender areas:
Can not be repaired in case of acute tendering. In slight cases the cloth can be made stronger by boiling in caustic soda salt and re-dyed.

B. Dyeing stage:

1. Dye stains:

Causes of dye stains:
Darker spots of the same color due to incomplete dissolution of the dye.

Remedies of dye stains:
In case of a direct dye, trent in a boiling leveling bath. Stripping the color and re-dyeing in case of vat and fast colors. Adding also leveling agents.

2. Dark selvedges:

Causes of dark selvedges:
Darker color near selvedges due to non uniform winding of the cloth while working on jiggers.

Remedies of dark selvedges:
Stripping of color, dyeing & re-dyeing and perfect beaming has to be performed.

3. Dark selvedges and brenzing:

Causes of dark selvedges and brenzing:
This happens with vat and sulfur dyeing due to un proper winding or dyeing in open jiggers which are subjected to a draft of air.

Remedies of dark selvedges and brenzing:
Stripping of color, dyeing & re-dyeing and perfect beaming has to be performed.

4. Dye mottling:

Causes of dye mottling:
Unleveled dyeing due to errors in the dyeing methods or concentrations used.

Remedies of dye mottling:
Stripping or reducing the dye and re-oxidizing it. The color has to be adjusted by shading.

5. Sided dyeing:

Causes of Sided dyeing:
Different color depths on the sides. This is mainly due to unequal pressures on the dye mangle in continuous dyeing.

Remedies of Sided dyeing:
Stripping of the color and re-dyeing after proper action on unequal dye mangle of continuous dyeing.

6. Specky dyeing:

Causes of Specky dyeing:
Surface of the dyed fabric has darker dyed spots. This is due to the use of dye stuff brands of big particle size especially in pigmentation dyeing of vat colors.

Remedies of Specky dyeing:

  • The cloth has to be boiled, color then stripped.
  • Use of vat colors of highly dispersed brands in re-dyeing is recommended.
7. Color migration:

Causes of Color migration:
Difference in color intensity from one side of the fabric to the other. Also difference in shades of one face of the cloth from the other. This is mainly due to un-equal drying of both faces of cloth.

Remedies of Color migration:
Color to be partially stripped and re-dyed.