Overview
ISO 13061-15:2017 specifies a standardized laboratory method for measuring linear swelling of wood in the radial and tangential directions using small clear specimens. The standard defines specimen preparation, drying and soaking procedures, measurement accuracy, and the calculation and reporting of radial and tangential swelling expressed as a percentage change from oven-dry dimensions to fully saturated dimensions.
Key topics and technical requirements
- Scope: Determination of linear swelling in radial and tangential directions for small clear wood specimens.
- Specimen size and orientation: Rectangular prisms with at least 20 mm in radial and tangential directions and ≥ 5 mm along the grain; growth-ring inclination to radial faces ≤ 10°.
- Conditioning:
- Oven‑dry: Dry to constant mass at (103 ± 2) °C, cool in a desiccator, then measure.
- Fully saturated: Soak in distilled water at (20 ± 2) °C until dimensions stabilize (measure every 3 days).
- Measurement accuracy: Instruments accurate to 0.02 mm; measuring faces 5–8 mm diameter; balance accurate to 0.001 g.
- Acceptance criteria for stability: Change between successive weighings ≤ 0.2% or dimensional change ≤ 0.02 mm for drying; dimensional change ≤ 0.02 mm for saturation.
- Calculation: Linear swelling percentage for each direction:
- Radial: α_r = (l_r2 − l_r1) / l_r1 × 100%
- Tangential: α_t = (l_t2 − l_t1) / l_t1 × 100%
Results expressed to the nearest 0.1%; report mean and standard deviation.
- Reporting: Include reference to ISO 13061-15, sampling per ISO 3129, measurement details, test results, statistics, test date, and testing organization.
Applications and users
ISO 13061-15 is used where accurate quantification of wood dimensional stability is required:
- Wood testing and materials laboratories performing physical and mechanical tests on timber.
- Timber and engineered wood product manufacturers assessing moisture-related dimensional changes for design, quality control, and specification compliance.
- Researchers and material scientists studying hygroscopic behavior, swelling anisotropy (radial vs. tangential), coatings, adhesives, or treatments that affect dimensional stability.
- Standards bodies, certification schemes, and procurement specifications that reference standardized swelling data for construction, furniture, joinery, and wood composites.
Keywords: ISO 13061-15, radial swelling, tangential swelling, wood testing, small clear wood specimens, oven-dry, fibre saturation point, dimensional stability.
Related standards
- ISO 3129 - Sampling and general requirements for small clear wood specimens (referenced for specimen selection).
- ISO 24294 - Timber vocabulary (terms and definitions).
- Other parts of the ISO 13061 series cover complementary physical and mechanical test methods.
Open preview (PDF)Physical and mechanical properties of wood — Test methods for small clear wood specimens — Part 15: Determination of radial and tangential swelling
