🧵 Yarn Testing Methods – Strength, Elongation, and Hairiness

Introduction

Yarn testing is one of the most essential processes in textile manufacturing. Before yarns are used in weaving, knitting, or any other fabric production, they must be tested to determine whether they meet the required standards of strength, elongation, and hairiness. These three parameters are critical in ensuring that the yarn performs well during production and that the final fabric maintains its desired quality, appearance, and durability.

The purpose of yarn testing is to evaluate the physical and mechanical properties of yarns, identify irregularities, and maintain consistent quality between batches. Accurate testing helps textile engineers and quality controllers make informed decisions about process adjustments, machine settings, and product suitability.

1. Yarn Strength Testing

1.1 Definition

Yarn strength is the maximum tensile force that a yarn can endure before it breaks. It shows the yarn’s ability to resist tension during manufacturing and end use. The stronger the yarn, the more durable the resulting fabric will be.

1.2 Importance of Yarn Strength

Yarn strength plays a vital role in:

• Reducing yarn breakage during weaving and knitting
• Enhancing fabric performance and durability
• Ensuring consistent machine efficiency
• Determining suitability for various textile applications (e.g., denim requires stronger yarns than T-shirts)

Yarns with inadequate strength can cause frequent end breaks, machine stoppages, and defective fabrics, which lead to production losses.

 

1.3 Types of Yarn Strength

1. Single Yarn Strength – Measures the breaking strength of one yarn strand.
2. Lea Strength – Measures the strength of a skein (usually 120 yards of yarn) and is mainly used for cotton yarns.
3. Bundle Strength – Determined by testing a group of parallel yarns together.

 

1.4 Testing Methods for Yarn Strength

a) Single Yarn Strength Tester (CRE Type – Constant Rate of Extension)

This is the most common method used worldwide.

Procedure:

1. A specific length of yarn (e.g., 500 mm) is clamped between two jaws.
2. One jaw remains fixed, while the other moves at a constant rate to stretch the yarn.
3. The machine records the maximum force at which the yarn breaks.

Common Instruments:

• Uster Tensorapid
• Instron Tensile Tester
• Zweigle Tensile Tester

Units of Measurement:

• Centinewton (cN)
• Grams-force (gf)
• Pounds-force (lbf)

 

b) Lea Strength Tester

Used mainly for cotton spun yarns, this method measures the force required to break a skein (120 yards). The result is expressed in pounds-force per lea.

Advantages:

• Simple and reliable for coarse cotton yarns.
• Helps compare batch-to-batch strength consistency.

 

1.5 Factors Affecting Yarn Strength

• Fiber type and quality (cotton, polyester, viscose, etc.)
• Spinning method (ring, rotor, air-jet)
• Twist level (too high or too low reduces strength)
• Moisture content
• Yarn evenness and imperfections

 

2. Yarn Elongation Testing

2.1 Definition

Elongation is the extent to which a yarn can stretch before breaking, usually expressed as a percentage of its original length. It represents the yarn’s elasticity and ability to absorb strain during processing and end use.

 

2.2 Importance of Elongation

• Indicates yarn flexibility during weaving or knitting
• Reduces breakage rates during fabric formation
• Affects comfort and stretchability of garments
• Helps determine suitability for different fabric types

For example:

• High elongation yarns are ideal for stretch fabrics and sportswear.
• Low elongation yarns are suitable for stiff fabrics and industrial textiles.

 

2.3 Testing Method

Elongation is usually measured along with strength using a tensile testing machine.

Procedure:

1. The yarn is clamped between two jaws set at a specific distance (gauge length).
2. The machine stretches the yarn until it breaks.
3. The increase in length is measured and expressed as a percentage.

Formula:

Elongation (%)=(L2−L1)L1×100\text{Elongation (\%)} = \frac{(L_2 - L_1)}{L_1} \times 100Elongation (%)=L1​(L2​−L1​)​×100

Where:

• L1L_1L1​ = Original length
• L2L_2L2​ = Length at breaking point

 

2.4 Typical Elongation Values

Fiber Type	Elongation (%)
Cotton	5–8
Wool	25–35
Polyester	10–20
Nylon	20–40
Viscose	12–18

 

2.5 Factors Affecting Elongation

• Fiber structure and type (natural vs. synthetic)
• Moisture content (higher humidity increases elongation for cotton)
• Twist level (moderate twist improves elongation)
• Yarn fineness (finer yarns often have higher elongation)

 

3. Yarn Hairiness Testing

3.1 Definition

Hairiness is the degree to which fiber ends project from the main body of the yarn. It is a surface property that influences both the visual and functional aspects of fabrics.

 

3.2 Importance of Yarn Hairiness

Hairiness can significantly affect:

• Fabric appearance (smooth or fuzzy surface)
• Dye uptake and color consistency
• Pilling tendency
• Fabric handle and touch
• Weaving and knitting efficiency

Excessive hairiness causes entanglement, machine stoppage, and poor-quality fabrics. On the other hand, very low hairiness can make fabrics feel too flat or stiff.

 

3.3 Testing Method – Uster Hairiness Tester

The most widely used instrument for measuring hairiness is the Uster Hairiness Tester.

Principle:

• The yarn passes through an optical or laser sensor.
• The device detects and counts the number and length of fiber ends protruding from the yarn body.
• Results are expressed as a hairiness index (H).

Example:

• H = 3.0 → Moderately hairy yarn
• H = 5.0 or above → High hairiness (poor for weaving)

 

3.4 Factors Affecting Hairiness

• Fiber length (short fibers increase hairiness)
• Spinning system (air-jet yarns are smoother than ring-spun)
• Twist level (higher twist reduces hairiness)
• Finishing and winding tension

 

4. Comparison Table

Property	Testing Method	Main Instrument	Importance	Typical Unit
Strength	Tensile Test (Single Yarn / Lea)	Uster Tensorapid, Lea Tester	Yarn durability	cN, gf
Elongation	Tensile Test	Instron, Uster Tester	Yarn flexibility	%
Hairiness	Optical/Laser Sensor	Uster Hairiness Tester	Surface quality & appearance	Hairiness Index (H)

 

5. Why Yarn Testing Matters in Modern Textile Production

In today’s competitive textile industry, quality control is more critical than ever. Global buyers demand consistent quality, smooth fabric appearance, and durable garments. Yarn testing ensures:

• Uniformity across production batches
• Reduced rejections and customer complaints
• Higher production efficiency
• Improved performance of fabrics and garments

Testing also supports sustainability, as strong, balanced, and smooth yarns produce fewer waste materials and require less energy for reprocessing.

 

Conclusion

Yarn testing for strength, elongation, and hairiness provides essential insights into the performance and quality of yarns before they are used in fabric manufacturing. A strong yarn ensures durability, an elastic yarn provides flexibility, and a smooth yarn guarantees a neat, pilling-free surface.

By applying advanced instruments such as Uster Tensorapid, Instron Tensile Tester, and Uster Hairiness Tester, textile engineers can accurately analyze these parameters and maintain international quality standards. Ultimately, proper yarn testing leads to better fabrics, happier buyers, and greater success for textile manufacturers.