ISO 7211-5:2020

Overview - ISO 7211-5:2020 (Textiles, linear density of yarn removed from fabric)

ISO 7211-5:2020 specifies standardized laboratory methods to determine the linear density (tex) of yarns removed from woven fabrics. The standard applies to yarns of nominally uniform linear density and describes how to extract threads, measure their straightened length, determine mass, and calculate linear density either in conditioned state (Method A) or oven-dry plus agreed moisture regain (Method B). It covers both testing with and without prior removal of non‑fibrous matter.

Key topics and technical requirements

• Test specimens and sampling
  • Condition fabric per ISO 139; cut rectangular strips ~50 cm long containing ≥50 yarn lengths; use multiple strips (warp and weft sampling from different packages).
  • Remove first 10 threads from each strip and measure straightened lengths, then remove at least 40 more threads.
• Apparatus and environment
  • Balance accurate to 0.1% of the smallest mass.
  • Apparatus for measuring straightened length (see ISO 7211-3).
  • Ventilated drying oven for Method B; use standard conditioning/testing atmospheres per ISO 139.
• Methods
  • Method A: condition specimens to equilibrium with the standard atmosphere and weigh (recommended where volatile losses are a concern).
  • Method B: oven-dry to constant mass and recalculate to the required moisture content using the agreed moisture regain (note: 105 °C is referenced as a heating condition to be considered).
  • Optionally remove non‑fibrous matter per ISO 1833-1 before measurement (removal can affect thread length - allow reconditioning if removed before separation).
• Calculations
  • Linear density (tex) = (mass (g) × 10^3) / total length (m).
  • For Method B, convert oven-dry tex to conditioned tex using the agreed moisture regain.
• Reporting
  • Report method used (A or B), atmosphere, whether non‑fibrous matter was removed and how, agreed moisture regain, linear density for warp and weft, date, and any deviations.

Applications and users

ISO 7211-5 is used by:

• Textile testing laboratories and quality control teams for yarn and fabric verification
• Textile manufacturers and converters for production monitoring and specification compliance
• R&D and product development for fabric construction analysis and material comparisons
• Certification bodies and procurement teams requiring standardized textile data

Practical benefits include consistent tex values for yarns extracted from fabrics (accounting for crimp and fabric effects), reliable input to fabric construction analysis, and harmonized reporting for acceptance testing.

Related standards

• ISO 7211 series (methods for analysis of woven fabrics construction)
• ISO 7211-3 (determination of yarn crimp and apparatus)
• ISO 139 (standard atmospheres for conditioning/testing)
• ISO 1833-1 (removal/analysis of non‑fibrous matter)

Keywords: ISO 7211-5:2020, textiles standard, linear density, tex, yarn removed from fabric, Method A, Method B, conditioning, oven-dry, agreed moisture regain.