Overview
EN ISO 13015:2013 (ISO 13015:2013) - published by CEN/ISO - specifies a laboratory method to measure distortion in woven fabrics, specifically the determination of skew and bow where the weft (picks) are intended to be perpendicular to the warp (ends). The standard defines terms, specimen preparation, apparatus, measurement procedures and how to calculate and report results, helping textile manufacturers and test laboratories to quantify and control fabric distortion.
Key topics and technical requirements
- Scope: Measurement of distortion (skew and bow) in woven fabrics with perpendicular weft and warp yarns.
- Definitions:
- Skew: picks are straight but not at right angles to the ends.
- Bow: curvature of warp or weft across the width or length of the fabric.
- Principle: Trace a selected weft yarn across a flat, untensioned specimen and model its course using one or more triangles. Each triangle’s slope = height (a) / base (b); skew is expressed as a percentage of that slope. When multiple triangles are used, the highest skew value is reported.
- Apparatus: set square (right angle), metallic ruler ≥100 cm (or at least fabric width), small metallic ruler (20 cm), graduated in millimetres.
- Specimen and conditioning: full-width specimens not less than 500 mm long, not taken within 1 m of fabric ends. Conditioning and testing in standardized atmosphere per ISO 139; conditioning at least 16 h.
- Preparation methods: marking the visible weft with a thin marker or fraying to expose a complete weft yarn when visibility is poor.
- Measurements:
- Overall skew: single-triangle model measuring the maximal perpendicular distance (a) and useful width (b).
- Local skew: two- or three-triangle models for localized distortion.
- Weft/warp bow: determined per Annex A as greatest perpendicular deviation from a straight line joining ends.
- Reporting: include specimen, conditioning, measurement method, and calculated skew/bow values.
Practical applications and users
- Quality control in textile mills and finishing plants to ensure fabric meets appearance and make-up requirements (stripes, plaids, pattern matching).
- Garment and upholstery manufacturers to prevent fitting and assembly issues caused by distortion.
- Textile testing laboratories, procurement/inspection teams, and R&D groups verifying process changes (weaving, washing, finishing).
- Useful for suppliers and buyers to specify acceptable distortion limits in contracts.
Related standards
- ISO 139 - Standard atmospheres for conditioning and testing (normative reference used by EN ISO 13015:2013).
- Other textile test standards may be used in conjunction for comprehensive fabric characterization (refer to national laboratory bibliographies).
Keywords: EN ISO 13015:2013, ISO 13015, woven fabrics, fabric distortion measurement, skew and bow, weft, warp, textile testing, CEN.