Overview
ISO 13061-15:2025 - "Physical and mechanical properties of wood - Test methods for small clear wood specimens - Part 15: Determination of radial and tangential swelling" specifies a standardized method to determine linear swelling of wood in the radial and tangential directions. The procedure measures dimensional change between the oven-dry state and the fully saturated state, expressed as a percentage. This International Standard is intended for small clear wood specimens used in research, quality control and material characterization.
Key topics and technical requirements
- Principle: Measure dimensions in radial and tangential directions when oven-dry and again after full water saturation; calculate percent swelling as (saturated − oven‑dry) / oven‑dry × 100.
- Specimen preparation
- Rectangular prism cut from air-dry wood.
- Minimum size: at least 20 mm square in radial and tangential directions and at least 5 mm along the grain (larger allowed if only one direction measured).
- Angle of annual rings to tangential faces ≤ 10°.
- Measurement points marked at the center of tangential and radial faces.
- Apparatus and measurement accuracy
- Dimensional measuring instruments accurate to 0.02 mm, with parallel flat ends (5–8 mm diameter) and low clamping deformation.
- Oven: forced convection at (103 ± 2) °C for drying to constant mass.
- Balance accurate to 0.001 g.
- Vessel with distilled water for soaking at (20 ± 2) °C until dimensional stability.
- Procedure
- Dry open‑piled specimens to constant mass (control checks every 8 h) and measure oven‑dry radial/tangential dimensions.
- Soak in distilled water until dimensions stabilize (check every 3 days) and measure saturated dimensions.
- Express individual and mean swelling results to the nearest 0.1%; calculate mean and standard deviation.
- Test report must reference ISO 13061-15:2025 and include sampling details, measurement conditions, results with statistics, test date and testing organization.
Applications and users
ISO 13061-15:2025 is used by:
- Timber testing laboratories and accredited quality-control facilities
- Wood scientists and material researchers studying dimensional stability and hygromechanical behaviour
- Manufacturers of wood products (furniture, flooring, engineered wood) assessing swelling behaviour
- Certification bodies and standards developers requiring reproducible test data for product specifications
Keywords: ISO 13061-15:2025, radial swelling, tangential swelling, wood test methods, small clear wood specimens, linear swelling, oven-dry, saturated condition.
Related standards
- ISO 3129 - Sampling methods and general requirements for testing small clear wood specimens (normative reference)
- ISO 24294 - Timber vocabulary (terms and definitions used in this standard)
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