Overview
ISO 3379:2015 - "Leather - Determination of distension and strength of surface (Ball burst method)" specifies a standardized laboratory test to measure how the grain or finished wearing surface of flexible leather distends and fails when deformed by a hemispherical plunger. The method is widely used to assess surface strength, distension (extension) and the lastability of leathers, particularly for footwear uppers.
Key keyword targets: ISO 3379, leather testing, ball burst method, distension, surface strength, lastability, footwear leather.
Key topics and technical requirements
- Test principle: A circular leather specimen is clamped around a central aperture and a hemispherical steel ball on a plunger is forced against the reverse side, progressively distending the wearing surface until first crack/damage and/or burst occur. Distension (plunger travel) and force are recorded.
- Specimen and sampling: Condition samples per ISO 2419; sample locations per ISO 2418. At least three test pieces are cut (one per hide/skin if multiple hides are in the batch) using a suitable press knife.
- Apparatus essentials:
- Clamp with a central aperture: 25.0 mm ± 0.5 mm diameter.
- Hemispherical plunger: nominal 6.25 mm ± 0.05 mm diameter.
- Plunger travel speed: 0.20 mm/s ± 0.05 mm/s (no rotation).
- Measurement accuracy: distension ±0.05 mm, force ±10 N.
- Procedure highlights: Record distension and force at first surface cracking (to 0.1 mm and 10 N resolution). If specimen does not crack before bursting, report burst values. Tests should be continuous (avoid pauses >15 s) to prevent stress relaxation artefacts.
- Special cases: Patent leather may show film cracking distinct from grain cracking; visual signs and momentary force drops help identify grain failure.
- Test report requirements: Must reference ISO 3379 and include sample ID, thickness, mean distension and force at crack (and burst if required), conditioning atmosphere, and any deviations.
Applications and users
- Typical applications:
- Evaluating lastability and suitability of leather for footwear uppers.
- Quality control of finished leather surfaces and coatings.
- R&D for tanning, finishing, and protective films.
- Supplier verification and material specification compliance.
- Typical users:
- Tanneries and leather finishers
- Footwear manufacturers and designers
- Independent testing laboratories and QA departments
- Material scientists and product specification writers
Related standards
- ISO 2418 - Sampling location for leather tests
- ISO 2419 - Sample preparation and conditioning
- ISO 2589 - Thickness measurement for leather
Using ISO 3379 helps ensure consistent, comparable measurement of leather surface performance - crucial for product durability claims, supplier acceptance, and footwear design decisions.