Dyeing Defects | Common Knit Dyeing Faults And Their Way Of Remedies

Knit Dyeing

The knit fabric dyeing process is different from the yarn dyeing or woven fabric dyeing process. However, during knit dyeing; some dyeing faults can be occurred due to the wrong operating system. But it can be overcome by applying some techniques.

Knit Dyeing Faults and Their Way of Remedies:

The following are the common knit fabric dyeing faults and their way of remedies. They are-

  • Crack, Rope, and Crease Marks
  • Fabric Distortion and Increase in Width
  • Pilling
  • Running Problem
  • Uneven Dyeing
  • Shade variation (Batch to Batch)
  • Dye Spot
  • Patchy Dyeing
  • Specky Dyeing
  • Roll to Roll Variation or Meter to Meter Variation
  • Crease Mark
  • Softener Mark

Crack, Rope, and Crease Marks

Causes:
  1. Poor opening of the fabric rope.
  2. Shock cooling of synthetic material.
  3. Incorrect process procedure.
  4. Higher fabric speed.
Remedies:
  1. Pre-Heat setting.
  2. Lower rate rising and cooling the temperature.
  3. Reducing the m/c load.
  4. Higher liquor ratio.
  5. Running at slightly higher nozzle pressure.

Fabric Distortion and Increase in Width

Causes:
  1. Too high material speed.
  2. Low liquor ratio.
Remedies:
  1. By decreasing both nozzle pressure & winch speed.
  2. By using a high liquor ratio.

Pilling

Causes:
  1. Too high mechanical stress on the surface of the fabric.
  2. Excess speed during processing.
  3. Excess foam formation in the dye bath.
Remedies:
  1. By using a suitable chemical lubricant.
  2. Using an antifoaming agent.
  3. By turn reversing the Fabric before dyeing.

Running Problem

A. Ballooning:
Causes:

Seam joining with too densely sewn.

Remedies:

By cutting a vertical slit of 10-15 cm in length for escaping the air.

B. Intensive Foaming
Causes:

Pumping a mixture of air and water.

Remedies:

By using an antifoaming agent.

Uneven Dyeing

Causes:
  1. Uneven pretreatment (uneven scouring, bleaching & mercerizing).
  2. Uneven heat-setting in the case of synthetic fibers.
  3. Quick addition of dyes and chemicals.
  4. Lack of control of dyeing machine.
Remedies:
  1. By ensuring even pretreatment.
  2. Ensuring even heat-setting in the case of synthetic fibers.
  3. By slow addition of dyes and chemicals.
  4. Proper controlling of dyeing machine.

Shade Variation (Batch to Batch)

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-

  1. Use standard dyes and chemicals.
  2. Maintain the same liquor ratio.
  3. Follow the standard pretreatment procedure.
  4. Maintain the same dyeing cycle.
  5. An identical dyeing procedure should be followed for the same depth of the shade.
  6. Make sure that the operators add the right bulk chemicals at the same time and temperature in the process.
  7. The Ph, hardness, and sodium carbonate content of supply water should check daily.

Dye Spot

Causes:
  • Improper mixing of dyestuff in the solution, in the right amount of water, at the temperature.
Remedies:
  • We should pass the dissolved dyestuff through a fine stainless steel mesh strainer when adding it to the chemical tank so that the large un-dissolved particles are removed.

Patchy Dyeing

Causes:
  1. Uneven heat in the machine.
  2. Improper impregnation of dye liquor due to the low wetting property of the fabric.
  3. Dye migration during intermediate dyeing.
Remedies:
  1. By proper pretreatment.
  2. By adding an extra wetting agent.
  3. Heat should be the same throughout the dye liquor.

Specky Dyeing

Causes:
  1. Excessive foam in the dye bath.
  2. Fall of water droplets on fabric surface before or after dyeing.
  3. Insufficient after treatment.
Remedies:
  1. By using an antifoaming agent.
  2. Sufficient after treatment.
  3. By using a good wetting agent in the dye bath.

Roll to Roll Variation or Meter to Meter Variation

Causes:
  1. Poor migration property of dyes.
  2. Improper dyes solubility.
  3. The hardness of the water.
  4. Faulty m/c speed, etc
Remedies:
  1. Use standard dyes and chemicals.
  2. Proper m/c speed.
  3. Use of soft water.

Crease Mark

Causes:
  1. Firstly, the poor opening of the fabric rope.
  2. Secondly, shock cooling of synthetic material.
  3. Thirdly, if pump pressure & reel speed is not equal
  4. Due to high-speed m/c running.
Remedies:
  1. Firstly, maintaining proper reel speed & pump speed.
  2. Secondly, lower rate rising and cooling the temperature.
  3. Thirdly, reducing the m/c load.
  4. Lastly, higher liquor ratio.

Dye Spot:

Causes:
  1. Firstly, improper Dissolving of dye particles in the bath.
  2. Also, Improper Dissolving of caustic soda particles in the bath.
 Remedies:
  1. At first, by proper dissolving of dyes & chemicals.
  2. Bypassing the dissolved dyestuff through a fine stainless steel mesh strainer, so that the large un-dissolved particles are removed.

Softener Mark

Causes:
  1. Firstly, improper mixing of the Softener.
  2. Improper running time of the fabric during application of softener.
  3. Entanglement of the fabric during application of softener.
Remedies:
  1. Firstly, maintaining proper reel speed & pump speed.
  2. Proper Mixing of the softener before addition.
  3. Prevent the entanglement of the fabric during the application of softener.

So, we should be careful about the knit dyeing faults as well as yarn dyeing faults.

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