Overview
ISO 6939:1988 specifies the skein (échevette) method for determining the breaking strength of yarns taken from packages. It applies to spun single and folded yarns of any fibre or fibre mixture made by any spinning system. The method is primarily comparative and intended for routine quality control and rapid assessment of yarn strength - not as a replacement for single-yarn reference methods.
Key topics and technical requirements
- Scope and limitations
- Applicable to spun single and folded yarns; not recommended for filament yarns, glass yarns, highly complex structures (cabled yarns, cords) or yarns too thick to wind in two even layers.
- Test principle
- Break a skein (small wound hank) on a tensile tester and record maximum force; express results as breaking force or tenacity (force per unit linear mass).
- Apparatus and parameters
- Dewinder/winder (typical perimeter 1 m) with transverse motion to wind in no more than two layers.
- Skein rack/holder and tensile testing machine (constant crosshead speed or constant extension).
- Recommended crosshead speed: 300 mm/min ± 10 mm/min, or adjust so mean rupture time is about 20 s ± 3 s.
- Dewinding rotation commonly 100–300 min⁻¹ (often limited to 200 min⁻¹ max); pins 25–32 mm diameter.
- Sampling and preparation
- Conditioning and testing atmospheres per ISO 139.
- Mass-per-unit-length (if required) determined per ISO 2060; related single-yarn test is ISO 2062.
- Guidance on the number of skeins: sample-size formula provided; if variability unknown, default guidance (e.g., 10 skeins for typical cotton/combed wool, 20 for carded wool).
- Result factors
- Skein-strength correlates with single-yarn tenacity but typically yields lower values. Results depend on single-fibre strength, elongation to break, variation in elongation, initial modulus and yarn-to-yarn cohesion.
Applications and users
- Useful for incoming inspection, production monitoring and comparative quality control where rapid, practical strength checks are needed.
- Typical users: textile mills, yarn producers, quality control laboratories, fabric manufacturers, procurement teams and testing service labs that handle spun yarns.
- Valuable when single-yarn testing (ISO 2062) is impractical, costly or slow in industrial settings.
Related standards
- ISO 139 - Standard atmospheres for conditioning and testing.
- ISO 2060 - Determination of linear density by skein method.
- ISO 2062 - Single-yarn breaking force and elongation (reference method).
Keywords: ISO 6939, skein method, breaking strength of yarn, yarn tenacity, textile testing, spun yarn quality control.
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