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Dyeing Faults

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Dyeing Faults

1 . Batch to batch variation :

Causes: 

  1. Use of different dye lots, brands and chemicals
  2. Not maintaining same liquor ratio
  3. Improper dosing time of dyes and chemicals
  4. Batch to batch weight variation of dyes and chemicals
  5. Uneven pre-treatment

Remedies: 

  1. Use same dye lots, brands and chemicals
  2. Maintain same liquor ratio among machines
  3. standard pre-treatment method
  4. Follow identical dyeing procedures for the same depth of shade
  5. Regularly check bath pH, water hardness, water – supply and purity of chemicals

2 . Roll to roll / meter to meter variation/ running shade :

Causes: 

    1. Poor solubility and migration properties of dyes
    2. Improper machine speed/ reel speed/ pump speed
    3. Water hardness

Remedies: 

  1. Correct dye selection, using appropriate method for dissolving and using right
  2. Techniques for migration.
  3. Check machine speed during maintenance.

3 . Uneven dyeing :

Causes:  

  1. Improper color dosing
  2. Improper soda and chemical dosing
  3. Improper method of migration
  4. Uneven pre-treatment
  5. Uneven heat setting (synthetic fibers)
  6. Water hardness
  7. Incorrect pH adjustment

Remedies: 

  1. Careful color dosing
  2. Careful soda and other chemical dosing
  3. Follow proper dye migration method
  4. Ensure uniform absorbency and whiteness
  5. Identify water hardness and use sequestrant
  6. Always measure pH of all processes

4 . Dye spots/ colored spots :

Causes : 

  1. Dye deposition on the machine
  2. Improper dissolving of dyes
  3. Improper dissolving of alkali

Remedies :  

  1. Clean the machine properly with machine cleaner
  2. Proper dissolving of dyes and chemicals
  3. Passing dissolved dyes through a mesh strainer (screen printing mesh fabric), so that large un-dissolved aggregates are filtered and made smaller.

5 . Patchy dyeing :

Causes: 

  1. Faulty injection of alkali
  2. Improper mixing and addition of color
  3. Water hardness
  4. Uneven heating in machine
  5. Entanglement of fabric.
  6. Due to improper salt addition.
  7. Dye migration during intermediate dyeing.
  8. Uneven heat in the machine, etc.

Remedies:   

  1. Correct dosing of dyes and chemicals
  2. Consistent heating in the machine
  3. Check water hardness and add sequestrant
  4. By ensuring proper pre-treatment.

6 . Crease marks :

Causes: 

  1. Improper lubricating of heavy GSM fabrics
  2. Poor opening of fabric rope in machine
  3. Shock cooling of PES containing fabrics
  4. Unequal pump/nozzle pressure and reel speed
  5. High running speed of machine
  6. Very high loading capacity, above that issued

Remedies: 

  1. Maintaining proper reel speed and pump pressure
  2. Lower cooling rate
  3. Reduce machine loading

7 . Softener spots/ Chemical spots :

Fig:Softener spots/ Chemical spots

Causes: 

  1. Due to excess foaming during softening
  2. Excess softener dosage
  3. Improper softener dosing
  4. Large emulsion size of softener

Remedies: 

  1. Use no more than 2% o.w.f softener in machine
  2. Proper softener dosing
  3. Proper choice/ selection of softener
  4. Use good quality anti-foaming agent if required

8 . Soda spot & white spot :

Causes: 

  1. Improper dosing of alkali
  2. High alkalinity of bath
  3. High water hardness

 Remedies:   

  1. Proper and careful dosing of alkali
  2. Check bath alkalinity
  3. Measure water hardness and use good choice and quantity of sequestrant

9 . Hole :

Causes: 

  1. Improper mixing of caustic pellets during pre-treatment.

Remedies: 

  1. Properly dissolve caustic soda to avoid holes.                                                                                                                

10 . Pilling:

Causes: 

  1. Due to friction of fabric against parts
  2. Improper enzyme treatment
  3. Poor yarn quality

Remedies: 

  1. Lubricate fabric
  2. Air turning when required
  3. Increase enzyme dosage
  4. Increase passage of fabric through singeing machine
  5. Use low-pilling yarns to make fabric

11 . Lycra out :

Causes: 

  1. High processing temperature (PES dyeing)
  2. Excessive chemical use
  3. Long processing times

Remedies:

  1. Control over temperature
  2. Lower chemical use and processing times  

Samples of different types of dyeing faults of knit fabrics:

  1. Dirty spot
  2. Chemical spot
  3. Black conta
  4. Yellow spot
  5. Iron spot
  6. Color spot

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