Overview
ISO 15625:2014 - "Silk - Electronic test method for defects and evenness of raw silk" defines standardized procedures for electronically testing raw silk quality using capacitive and optical testers. The method applies to raw silk (skein or cone, soaked or unsoaked) with yarn sizes from 13.3 dtex to 76.7 dtex (12–69 denier). The standard covers sampling, laboratory preparation, apparatus settings, test procedure, defect classification and expression of evenness metrics for consistent quality assessment and reporting.
Keywords: ISO 15625:2014, raw silk testing, capacitive tester, optical tester, evenness, silk defects, silk quality.
Key topics and technical requirements
- Measurement principle:
- Capacitive sensors detect capacitance changes correlated with mass variation (used for defects and evenness).
- Optical sensors detect photometric/shadow changes correlated with cross-sectional area (used for defects and shape detection).
- Defect types defined: slub, thick place, thin place, small imperfection element (SIE) - classified by length and mass or cross-sectional thresholds.
- Evenness indices: CV% calculated for 1 cm, 5 m and 50 m segments; between-skein/cone CV% for lot homogeneity.
- Apparatus and performance: electronic tester (single or multi-spindle) with signal processing capable of classifying defects and producing statistical charts; sensor precision ≤ 5%, minimum yarn advancement 1 mm.
- Sampling & lot formation: typical lot = 600 kg (same nominal size, same reeling apparatus). Sampling: 24 skeins (specified positions) or 12 cones per lot.
- Sample preparation & test settings:
- Winding for skeins: 7.5 km from each of two skeins per bobbin to a total 15 km each; minimum test sample per bobbin/cone ≥ 12.5 km, total lot testing ≥ 150 km.
- Conditioning: follow ISO 139, minimum 12 h.
- Winding speed (preparation): 140–200 m/min ±6 m/min; winding tension 0.5 ±0.1 cN/dtex.
- Test running speed: 600 ±30 m/min (raw silk), 1 000 ±50 m/min (soaked silk); pre-tension 0.20 ±0.05 cN/dtex.
- Documentation: test report must include sample condition (soaked/unsoaked), setting parameters and statistical outputs; annexes provide defect classification, sensor differences and soaked-silk preparation.
Applications and users
- Quality control in silk reeling and processing plants
- Textile testing laboratories and certification bodies
- Raw silk buyers, traders and quality inspectors for acceptance testing
- Machine manufacturers (capacitive/optical testers) for compliance and calibration
Practical benefits: objective defect counting, reproducible evenness measurement, better supplier benchmarking and process control.
Related standards
- ISO 139 - Textiles: standard atmospheres for conditioning and testing
- ISO 2060 - Yarn linear density (skein method)
ISO 15625:2014 helps standardize electronic raw silk testing, improving comparability of defect and evenness data across suppliers and labs.