Common Defects in Polyester Dyeing and How to Fix Them

Polyester is widely used in apparel, sportswear, home textiles, and industrial fabrics because of its durability and versatility. However, polyester dyeing—especially with disperse dyes—can sometimes produce defects if process control is not maintained. These defects affect shade quality, fastness, and overall appearance, leading to reprocessing and higher production costs.

This article explains the most common defects in polyester dyeing, their root causes, and effective solutions to help dye houses improve productivity and minimize re-dyeing.

 

1. Uneven Dyeing (Patchy or Streaky Appearance)

Uneven dyeing is one of the most frequent issues in polyester dyeing.

Causes

• Improper pre-treatment (poor scouring)
• Uneven heat transfer inside the dyeing machine
• Insufficient circulation of dye liquor
• Inconsistent material loading
• Poor leveling agents
• Variations in fabric density, GSM, or yarn quality

Solutions

• Ensure proper scouring using high-quality detergents and dispersing agents
• Maintain uniform dye liquor circulation using a high-flow pump
• Load fabric evenly to avoid entanglement
• Use effective leveling agents to improve migration
• Maintain consistent temperature rise (1–2°C/min)
• Use low-foam auxiliaries for high-temperature dyeing

 

2. Dye Spots and Specks

Small dye spots or specks appear when dye never fully disperses during the dyeing process.

Causes

• Undissolved or poorly dispersed dye particles
• Old, moisture-absorbed dyes
• Low-quality dispersing agents
• Dirty dye tanks, filters, or pipes

Solutions

• Sieve dyes before use and pre-disperse in warm water
• Store dyes in moisture-protected containers
• Use recommended dispersing agents
• Clean machine filters and nozzles regularly
• Increase dispersion temperature to 60–70°C before adding dyes

 

3. Oligomer Deposits (White Powdery Residue on Fabric)

Oligomers are low-molecular-weight polyester particles that migrate out of the fiber during high-temperature dyeing.

Causes

• High-pressure and high-temperature dyeing (130°C)
• Poor circulation causing oligomer redeposition
• Reusing old dye solutions too often
• Inadequate cleaning between batches

Solutions

• Use oligomer-removing agents in scouring or reduction clearing
• Maintain proper flow rate and liquor movement
• Clean machines thoroughly after dark or heavy loads
• Use anti-redeposition agents in the dye bath
• Avoid extended dyeing time beyond the required hold

 

4. Barre (Horizontal or Vertical Stripes)

Barre is a repetitive stripy appearance caused by variations in yarn or fabric structure.

Causes

• Mixed yarn lots
• Tension variations during knitting
• Uneven dye uptake due to GSM differences
• Improper heat-setting before dyeing

Solutions

• Ensure yarn lot uniformity
• Control knitting machine tension
• Use consistent GSM fabric lots
• Heat-set fabric properly before dyeing
• Use leveling agents to reduce shade variation

 

5. Poor Shade Matching

Shade mismatch occurs when the dyed fabric does not match the approved standard.

Causes

• Incorrect dye recipe
• Using different dye lots
• Variations in dyestuff purity
• pH or temperature not maintained
• Machine-to-machine variation

Solutions

• Verify dye lot numbers during recipe creation
• Standardize pH at 4.5–5.5 for disperse dyeing
• Use spectrophotometer results for recipe validation
• Follow consistent heating and cooling profiles
• Calibrate machines regularly

 

6. Crease Marks

Crease marks appear when fabric folds or wrinkles during dyeing.

Causes

• Excessive fabric load
• Low liquor ratio
• Fabric entanglement
• Low fabric movement in jet/soft-flow machines

Solutions

• Reduce load per batch
• Keep liquor ratio at optimum level (1:6 to 1:10)
• Increase circulation speed
• Use crease prevention agents
• Avoid excessive temperature rise during initial stages

 

7. Poor Fastness Properties (Wash, Rubbing, Sublimation)

Polyester requires strong fixation to achieve good fastness.

Causes

• Under-fixation of disperse dye
• Insufficient thermofixation in heat-setting
• Improper temperature/time combination
• Incomplete reduction clearing

Solutions

• Maintain dyeing at 125–130°C for sufficient time
• Correct thermofixation (180–210°C depending on fabric)
• Perform reduction clearing properly using caustic + hydrosulfite
• Avoid overloading machines which prevents full dye penetration

 

8. Gas Fading (Color Change When Exposed to Polluted Air)

Gas fading is common in blue and violet shades.

Causes

• Use of sensitive dyes
• Exposure to high NOx gases (traffic or furnace fumes)
• Poor dye selection

Solutions

• Use gas-fading-resistant disperse dyes
• Improve air circulation and ventilation in storage
• Avoid using sensitive dyes for outdoor applications

 

9. Surface Roughness or Poor Hand Feel

After dyeing, polyester may feel harsh or rough.

Causes

• Incomplete scouring
• Too high temperature causing fiber damage
• Excess oligomer buildup
• Inefficient softening process

Solutions

• Improve scouring using alkaline detergent and sequestering agents
• Avoid excessive temperature or long dyeing time
• Remove oligomer in reduction clearing
• Use silicone softeners during finishing

 

10. Shade Variation Between Lots

Lot-to-lot variation is a common commercial problem.

Causes

• Variations in yarn, GSM, or moisture content
• Slight changes in recipe or auxiliaries
• Machine differences
• Dye lot inconsistency

Solutions

• Maintain strict control of fabric/yarn parameters
• Use automatic chemical dosing systems
• Standardize all recipes
• Match dye lots before production
• Follow a strict dyeing SOP for every batch

 

Conclusion

Polyester dyeing requires precise control of temperature, pH, circulation, and chemical dosing. By understanding the common defects in polyester dyeing and their solutions, dye houses can significantly reduce reprocessing, improve shade consistency, and enhance production efficiency.

When mills follow proper pre-treatment, use high-quality dyes and auxiliaries, and maintain machine conditions, most defects can be avoided altogether. Implementing these solutions ensures better profitability and compliance with global quality requirements.