Overview
ISO 20535:2019 specifies a standardized test method for determining dimensional change of footwear insoles and insocks after cycles of wetting and drying. The method applies regardless of material and defines sampling, conditioning, measurement, immersion, drying and reporting procedures to quantify thickness, length and width changes and to record visual alterations.
Key topics and technical requirements
- Scope: Measurement of dimensional change (thickness, length, width) of insoles and insocks after immersion and drying.
- Sample preparation: Cut two square test pieces of (50 ± 2) mm; condition according to ISO 18454 for ≥24 h. If an insock has differing materials, test each material separately.
- Apparatus & accuracy: Dial micrometer (0.01 mm) with flat 10.0 ± 0.1 mm presser foot applying (50 ± 5) kPa; measuring device accurate to 0.1 mm; oven at (40 ± 2) °C; immersion weights, cutting device, pH-meter and volumetric flask.
- Reagents: Distilled water or artificial perspiration (acid/alkaline) prepared per ISO 105‑E04.
- Test cycle: Fully immerse test piece for 6 h, wipe surface, then dry in oven for 24 h at 40 ± 2 °C.
- Measurement points: Marked grid on the face side (lengthwise X, widthwise Y). Measure AB, CD (width), AC, BD (length) and thickness at specified centre and midpoint locations before and after the cycle.
- Results expression: Calculate percentage change in thickness and in length/width (average of two test pieces); report to nearest 0.1 %. Perform visual examination for delamination, unevenness, colour/print change.
- Reporting: Include ISO 20535 reference, full sample description, liquid used, numeric results, visual observations, sampling and any deviations, and test date.
Applications and users
ISO 20535 is used to:
- Verify dimensional stability of insoles/insocks during product development and quality control.
- Compare materials (leather, foam, textiles, composites) for moisture-related shrinkage or swelling.
- Support compliance documentation for footwear manufacturers, component suppliers, testing laboratories and material R&D teams.
- Inform design decisions where fit and comfort depend on dimensional stability after perspiration or exposure to water.
Keywords: ISO 20535, insoles, insocks, dimensional change, wetting and drying, test method, footwear.
Related standards
- ISO 105‑E04 (artificial perspiration solutions)
- ISO 17709 (sampling location and conditioning reference system)
- ISO 18454 (standard atmospheres for conditioning/testing)
- ISO 19952 (footwear vocabulary)
This standard provides a repeatable, clear procedure for quantifying moisture-induced dimensional changes essential to footwear performance and quality assurance.