Overview
EN ISO 1973:2021 (ISO 1973:2021) specifies two standardized methods for determining the linear density (mass per unit length) of textile fibres: the gravimetric method for bundles and the vibroscope method for individual fibres. The standard is intended primarily for fibres that can be kept straight and, for bundles, parallel and readily freed of crimp. It is particularly useful for man-made fibres (and, with less precision, for natural fibres). The document supersedes earlier editions and aligns with related ISO sampling and conditioning standards.
Key topics and technical requirements
- Scope: Applies to bundles of fibres (e.g., 50-fibre bundles) and to individual fibres; not applicable to tapered fibres. The vibroscope method may be unsuitable for hollow or flat (ribbon-like) fibres.
- Gravimetric method: Determines average linear density by cutting specimens of known length and weighing them. Requires a balance with accuracy of at least ±1 %.
- Vibroscope method: Determines linear density of individual fibres from resonance frequency, vibrating length and applied tension. Results can be read on the device display or via a connected computer system.
- Apparatus accuracy (vibroscope): tensioning force within ±0.5 %; resonance frequency reading error ≤ ±0.5 %; vibrating length error ≤ ±1 %.
- Correction factors: A correction for bending stiffness (stiff fibres) is permitted where necessary and agreed between parties.
- Sampling and conditioning: References ISO 1130 (sampling) and ISO 139 (conditioning and testing atmospheres); ISO 6989 is also referenced for certain procedures.
- Procedure and reporting: Includes instructions for specimen preparation, tension application, calculation and expression of results, and test reporting requirements.
Applications and who uses this standard
- Textile testing laboratories for routine fineness and linear density measurement.
- Fibre manufacturers for quality control of staple and filament products.
- Yarn and nonwoven producers to predict processability and downstream performance based on fibre fineness.
- R&D and material characterization teams assessing fibre properties, statistical distribution of individual fibre fineness (vibroscope), or mean bundle fineness (gravimetric).
- Standards bodies and procurement for specifying accepted test methods in contracts and conformity assessments.
Related standards
- ISO 139 - Standard atmospheres for conditioning and testing (climate control)
- ISO 1130 - Sampling of textile fibres for testing
- ISO 6989 - Determination of length and length distribution of staple fibres
- EN ISO 1973:1995 - Superseded by EN ISO 1973:2021
Keywords: EN ISO 1973:2021, linear density, textile fibres, gravimetric method, vibroscope method, fibre fineness, textile testing, ISO 1973:2021.