Dyeing Faults
670
0
Dyeing Faults
1 . Batch to batch variation :
Causes:
- Use of different dye lots, brands and chemicals
- Not maintaining same liquor ratio
- Improper dosing time of dyes and chemicals
- Batch to batch weight variation of dyes and chemicals
- Uneven pre-treatment
Remedies:
- Use same dye lots, brands and chemicals
- Maintain same liquor ratio among machines
- standard pre-treatment method
- Follow identical dyeing procedures for the same depth of shade
- Regularly check bath pH, water hardness, water – supply and purity of chemicals
2 . Roll to roll / meter to meter variation/ running shade :
Causes:
-
- Poor solubility and migration properties of dyes
- Improper machine speed/ reel speed/ pump speed
- Water hardness
Remedies:
- Correct dye selection, using appropriate method for dissolving and using right
- Techniques for migration.
- Check machine speed during maintenance.
3 . Uneven dyeing :
Causes:
- Improper color dosing
- Improper soda and chemical dosing
- Improper method of migration
- Uneven pre-treatment
- Uneven heat setting (synthetic fibers)
- Water hardness
- Incorrect pH adjustment
Remedies:
- Careful color dosing
- Careful soda and other chemical dosing
- Follow proper dye migration method
- Ensure uniform absorbency and whiteness
- Identify water hardness and use sequestrant
- Always measure pH of all processes
4 . Dye spots/ colored spots :
Causes :
- Dye deposition on the machine
- Improper dissolving of dyes
- Improper dissolving of alkali
Remedies :
- Clean the machine properly with machine cleaner
- Proper dissolving of dyes and chemicals
- 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:
- Faulty injection of alkali
- Improper mixing and addition of color
- Water hardness
- Uneven heating in machine
- Entanglement of fabric.
- Due to improper salt addition.
- Dye migration during intermediate dyeing.
- Uneven heat in the machine, etc.
Remedies:
- Correct dosing of dyes and chemicals
- Consistent heating in the machine
- Check water hardness and add sequestrant
- By ensuring proper pre-treatment.
6 . Crease marks :
Causes:
- Improper lubricating of heavy GSM fabrics
- Poor opening of fabric rope in machine
- Shock cooling of PES containing fabrics
- Unequal pump/nozzle pressure and reel speed
- High running speed of machine
- Very high loading capacity, above that issued
Remedies:
- Maintaining proper reel speed and pump pressure
- Lower cooling rate
- Reduce machine loading
7 . Softener spots/ Chemical spots :
Fig:Softener spots/ Chemical spots
Causes:
- Due to excess foaming during softening
- Excess softener dosage
- Improper softener dosing
- Large emulsion size of softener
Remedies:
- Use no more than 2% o.w.f softener in machine
- Proper softener dosing
- Proper choice/ selection of softener
- Use good quality anti-foaming agent if required
8 . Soda spot & white spot :
Causes:
- Improper dosing of alkali
- High alkalinity of bath
- High water hardness
Remedies:
- Proper and careful dosing of alkali
- Check bath alkalinity
- Measure water hardness and use good choice and quantity of sequestrant
9 . Hole :
Causes:
- Improper mixing of caustic pellets during pre-treatment.
Remedies:
- Properly dissolve caustic soda to avoid holes.
10 . Pilling:
Causes:
- Due to friction of fabric against parts
- Improper enzyme treatment
- Poor yarn quality
Remedies:
- Lubricate fabric
- Air turning when required
- Increase enzyme dosage
- Increase passage of fabric through singeing machine
- Use low-pilling yarns to make fabric
11 . Lycra out :
Causes:
- High processing temperature (PES dyeing)
- Excessive chemical use
- Long processing times
Remedies:
- Control over temperature
- Lower chemical use and processing times
Samples of different types of dyeing faults of knit fabrics:
- Dirty spot
- Chemical spot
- Black conta
- Yellow spot
- Iron spot
- Color spot
(670)