Knit Dyeing | Common Problems in Dyeing and Their Remedies?

Dyeing is the process of adding color to the textile material. Dyeing process of knit fabric is different than others dyeing like fibre dyeing, yarn dyeing etc. During these dyeing observe different types of faults which is called dyeing faults.There are some processes, techniques which can apply to reduce these faults.

Dyeing Faults:
Major dyeing faults which are mentioned below:

1. Uneven Dyeing
2. Batch to Batch Shade variation
3. Crease mark
4. Dye spot
5. Wrinkle mark
6. Roll to roll variation or Meter to Meter variation
7. Dimensional stability (shrinkage)
8. Pilling 

Uneven dyeing:

Causes of faults:

• Correct pH value not maintained.
• Inadequate scouring & bleaching of the grey fabric.
• Water hardness.
• Improper migration.
• Uneven pre treatment.
• Uneven heat setting.
• Improper soda dosing.
• Quick addition of dyes & chemical.

Remedies:

• Maintain the correct pH value.
• Scouring & bleaching fabric properly.
• Maintain water hardness.
• Proper migration.
• Ensuring even pre treatment.
• Ensuring even heat setting.
• Proper soda dosing.
• Proper neutralization.

Batch to Batch Shade Variation:

Batch to batch shade variation is common in exhaust dyeing which is not completely avoidable. Even though, to ensure a consistent batch to batch production of shade the following matters should be controlled carefully-

Causes:

• Fluctuation of Temperature.
• Improper dosing time of dyes & chemicals.
• Batch to batch weight variation of dyes and chemicals.
• Dyes lot variation.
• Improper reel speed, pump speed, liquor ratio.
• Improper pretreatment.

Remedies:

• Use standard dyes and chemicals.
• Maintain the same liquor ratio.
• Follow the standard pretreatment procedure.
• Maintain the same dyeing cycle.
• Identical dyeing procedure should be followed for the same depth of the Shade.
• Make sure that the operators add the right bulk chemicals at the same time and temperature in the process.
• The pH, hardness and sodium carbonate content of supply water should check daily.

Crease Mark:

Causes:

• Poor opening of the fabric rope
• Shock cooling of synthetic material
• If pump pressure & reel speed is not equal
• Due to high speed m/c running

Remedies:  

• Maintaining proper reel sped & pump speed.
• Lower rate rising and cooling the temperature
• Reducing the m/c load
• Higher liquor ratio

Dye Spot:

Causes:

• Improper Dissolving of dye particle in bath.
• Improper Dissolving of caustic soda particle in bath.

Remedies:

• By proper dissolving of dyes & chemicals
• By passing the dissolved dyestuff through a fine stainless steel mesh strainer, so that the large un-dissolved particles are removed.

Wrinkle Mark:

Causes:

• Poor opening of the fabric rope
• Shock cooling of synthetic material
• High temperature entanglement of the fabric

Remedies:

• Maintaining proper reel sped & pump speed.
• Lower rate rising and cooling the temperature
• Higher liquor ratio 

Roll to Roll Variation or Meter to Meter Variation:

Causes:

• Poor migration property of dyes.
• Improper dyes solubility.
• Hardness of water.
• Faulty m/c speed, etc

Remedies:

• Use standard dyes and chemicals.
• Proper m/c speed.
• Use of soft water.

Dimensional stability (shrinkage):

Causes:

• Insufficient relaxation during pretreatment.

• Inadequate setting of material.

• Lengthwise distortion caused bydyeing machine.

Remedies:

• Adapt relaxation and setting to material.

• Adjust dyeing machine to material. 

Pilling:

Causes:

• Too high mechanical stress on the surface of the fab-ric.
• Excess speed during processing.
• Excess foam formation in the dye bath.

Remedies:

• By using of a suitable chemical lubricant.
• By using antifoaming agent.
• By turn reversing the Fabric before dying.