Common Yarn Defects and Their Causes

Introduction

In textile manufacturing, yarn quality is the foundation of every high-quality fabric. The appearance, strength, and overall performance of a fabric largely depend on how uniform and defect-free the yarn is. Even a small defect in yarn can lead to serious problems during weaving, knitting, or dyeing, resulting in poor-quality fabric and production losses.

Therefore, identifying and understanding common yarn defects and their causes is essential for every spinner, textile engineer, and quality controller. By detecting defects early, manufacturers can take corrective actions, improve efficiency, and ensure that the yarn meets the required customer and industry standards.

 

What Are Yarn Defects?

Yarn defects are unwanted irregularities in the yarn structure that affect its appearance, strength, uniformity, or performance during textile processing. These irregularities can occur during various stages such as blow room, carding, drawing, roving, spinning, or winding.

Yarn defects not only reduce production efficiency but also affect the GSM, hand feel, and durability of the final fabric. For example, thick and thin places cause uneven fabric surface, while hairiness affects fabric smoothness and pilling behavior.

 

Classification of Yarn Defects

Yarn defects are generally categorized based on the nature and origin of the problem.

1. Count-related defects

Defects that occur due to irregular yarn fineness or variation in yarn diameter — such as thick and thin places.

2. Structural defects

These affect the internal structure of yarn — like neps, slubs, or twist variation.

3. Appearance-related defects

These impact the visual look of yarn and fabric — such as hairiness or contamination.

4. Process-related defects

Faults that arise due to improper settings or handling during spinning and winding — such as double yarns or snarls.

 

Common Yarn Defects and Their Detailed Causes

Below are the most frequent yarn defects, their technical explanations, causes, and impacts on textile processes.

 

1. Thick and Thin Places

Definition:
Thick and thin places are irregular portions in yarn where the diameter or mass per unit length is either higher (thick) or lower (thin) than normal.

Main Causes:

• Uneven drafting at the drafting zone of the ring frame
• Roller eccentricity or slippage
• Improper setting between drafting rollers
• Variation in fiber length or fineness
• Poor piecing technique during spinning
• Machine vibration or mechanical wear

Effects:

• Uneven fabric surface
• Streaks or barre marks after dyeing
• Frequent yarn breakage during weaving/knitting
• Reduced yarn tenacity

 

2. Neps

Definition:
Neps are small, tightly entangled clusters of fibers that appear as tiny specks or knots in yarn and fabric.

Causes:

• Immature or short cotton fibers
• Excessive mechanical action during carding or drawing
• Poor settings in carding (too close flats or cylinder wire)
• Inadequate cleaning in blow room
• High trash content in raw cotton
• Overworking during combing

Effects:

• White specks on dyed fabric
• Uneven dye penetration
• Rough fabric texture
• Reduced smoothness and comfort

 

3. Slubs

Definition:
Slubs are thick, uneven portions that appear randomly along the yarn due to accumulation of excess fibers.

Causes:

• Improper drafting in draw frame or roving frame
• Low twist in roving yarn
• Damaged rollers or fluted surfaces
• Lapping of fibers on front roller
• Foreign fiber inclusion during spinning

Effects:

• Uneven fabric thickness
• Poor appearance in woven or knitted fabric
• Fabric rejection in quality control

 

4. Snarls

Definition:
Snarls are spiral loops or tangles formed in yarn due to excessive twist or twist liveliness.

Causes:

• Over-twisting during spinning
• Uneven tension between bobbins or cops
• Poor winding tension control
• Low humidity causing electrostatic buildup

Effects:

• Yarn entanglement
• Machine stoppages during warping or knitting
• Uneven texture or puckering in fabric

 

5. Hairiness

Definition:
Hairiness refers to the number of fiber ends or loops that project from the yarn body, giving it a fuzzy appearance.

Causes:

• Long or irregular fiber length distribution
• Low twist level
• High spindle speed
• Poor control in the drafting system
• Lack of humidity in spinning section

Effects:

• Lint accumulation in machines
• Yarn entanglement during weaving
• Pilling in fabric
• Uneven surface appearance

 

6. Twist Variation

Definition:
Twist variation occurs when the amount of twist (turns per inch or per meter) changes irregularly along the yarn length.

Causes:

• Faulty gearing in ring frame
• Uneven traveler weight
• Irregular spindle speed
• Slippage in drive system
• Improper tension during winding

Effects:

• Variation in yarn strength
• Inconsistent dye absorption
• Fabric shade variation and reduced uniformity

 

7. Foreign Matter and Contamination

Definition:
Presence of foreign materials like dust, leaf, colored fibers, or polypropylene contamination inside the yarn.

Causes:

• Poor fiber cleaning in blow room
• Improper mixing of different bales
• Contaminated raw material (especially in manual handling)
• Using recycled waste fibers without cleaning

Effects:

• Spots or stains in fabric after dyeing
• Lower fabric quality and rejections
• Customer dissatisfaction

 

8. Double Yarn or Ply Faults

Definition:
Occurs when two yarns are accidentally twisted together or one ply is missing in multi-ply yarns.

Causes:

• End breakage during doubling not properly detected
• Improper creeling at doubling section
• Variation in ply tension during twisting

Effects:

• Uneven texture in fabric
• Reduced strength or appearance defect
• Irregular dye absorption

 

9. Yarn Unevenness (U% or CV%)

Definition:
Yarn unevenness is the variation in mass per unit length expressed as U% (unevenness percentage) or CV% (coefficient of variation).

Causes:

• Fiber variation in fineness or length
• Poor blending
• Faulty drafting system
• Machine vibration

Effects:

• Streaks in fabric
• Uneven dye uptake
• Poor appearance and mechanical performance

Testing Instrument:

• Uster Evenness Tester (UT5 or UT6)

 

Yarn Defects in Different Spinning Stages

Stage	Possible Defects	Common Causes
Blow Room	Contamination, neps	Improper cleaning, poor opening
Carding	Neps, fiber rupture	Wrong setting of flats, high speed
Drawing	Thick/thin places	Drafting error, roller slippage
Roving	Slubs, twist variation	Low twist, poor roller alignment
Ring Spinning	Hairiness, snarls	Excess twist, improper humidity
Winding	Double yarn, tension faults	Faulty sensors, uneven tension

 

How to Prevent Yarn Defects

To achieve a consistent and defect-free yarn, follow these preventive measures:

1. Maintain proper machine settings:
• Regularly calibrate drafting zones, roller pressure, and twist levels.
2. Use high-quality raw materials:
• Choose fibers with consistent length, fineness, and maturity.
3. Ensure regular machine maintenance:
• Clean drafting rollers, spindles, and creels frequently.
4. Control environmental conditions:
• Maintain optimal humidity (45–60%) to reduce static electricity.
5. Monitor quality continuously:
• Use online Uster Tester, Zweigle Hairiness Tester, or Tenso Rapid for automatic detection of faults.
6. Train operators:
• Skilled operators can quickly detect early signs of machine malfunction or irregular yarn.

 

Impact of Yarn Defects on Fabric

Yarn Defect	Fabric Problem	Result
Thick/Thin Places	Uneven texture	Visible streaks
Neps	Dyeing faults	White specks
Hairiness	Pilling	Rough surface
Slubs	Irregular surface	Fabric rejection
Twist Variation	Uneven strength	Weak spots
Contamination	Visible flaws	Quality complaints

 

Conclusion

Producing defect-free yarn is essential for high-quality textile production. Every stage of spinning — from raw material selection to winding — must be carefully controlled to minimize faults like thick and thin places, neps, slubs, hairiness, and contamination.
By adopting modern testing technologies, regular maintenance schedules, and trained supervision, textile mills can achieve consistent yarn quality and reduce waste, ensuring better productivity and higher customer satisfaction.