Overview
ISO 7211-3:1984 specifies a standardized laboratory method for determining the crimp (embuvage) of yarn in woven fabrics. The method measures the difference between the yarn length when straightened under a specified tension and the distance the yarn occupies in the fabric, expressing that difference as a percentage of the in‑fabric length. This procedure is applicable to most woven fabrics and is essential for consistent yarn crimp determination, fabric construction analysis and quality control.
Key topics and requirements
- Principle: Remove threads from a conditioned fabric strip, straighten each yarn by applying a rectifying tension (varied by yarn type and linear density), measure the yarn length under tension (L) and the in‑fabric length (L0). Calculate crimp C = (L − L0) / L0 × 100.
- Apparatus:
- Tensioning device with two clamps (parallel clamping surfaces, adjustable spacing, marks ~2.5 mm from clamp edge).
- Means to apply and vary rectification tension.
- Ruler graduated in the same units and an unpicking needle.
- Specimen preparation:
- Condition samples in a normal textile atmosphere (per ISO 139) for at least 16 hours.
- Cut five rectangular strips (two with long side parallel to warp, three parallel to weft) and extract groups of 10 yarns from the middle of each strip.
- Each strip should contain at least 10 yarns across and a length representing at least 20 times the length held in the clamps.
- Measurement procedure:
- Place yarn ends in clamps, apply specified rectification tension, measure L (length under tension) and L0 (distance between clamp markers equal to strip width).
- Repeat measurements to obtain averages for groups of 10 yarns.
- Rectification tension guidance:
- An annex provides tension formulas expressed as a function of yarn linear density (tex) for common yarn types (cotton, wool, continuous synthetic filaments). Tensions are given in cN (table footnote as printed: “1 cN = 1 gf”).
- Reporting: Test report must include standard reference (ISO 7211/3), conditioning atmosphere, specimen dimensions, applied rectification tension, measured lengths, crimp (%) for each group and any deviations from the method.
Applications and users
- Textile testing laboratories and quality control departments
- Fabric manufacturers and textile technologists analyzing weave geometry
- R&D and academic researchers studying yarn/fabric behavior, dimensional stability and appearance
- Procurement and compliance teams specifying construction parameters for woven fabrics
Related standards
- ISO 139 - Atmospheres for conditioning and testing textiles (referenced for conditioning requirements)
Keywords: ISO 7211-3:1984, textiles, woven fabrics, yarn crimp determination, embuvage, rectification tension, tex, fabric construction, method of analysis.
Open preview (PDF)Textiles — Woven fabrics — Construction — Methods of analysis — Part 3: Determination of crimp of yarn in fabric
