Overview
ISO 2493-2:2020 specifies a laboratory method to determine the resistance to bending of paper and paperboard using a Taber‑type tester. The standard defines the test geometry and procedure to measure the bending moment required to deflect a 38.0 mm wide, vertically clamped specimen by 15° (or 7.5° for boards that permanently deform). Results are reported as a bending moment (mN·m) or in Taber stiffness units (convertible to SI units).
Keywords: ISO 2493-2, Taber‑type tester, bending resistance, paper testing, paperboard stiffness, bending moment, Taber stiffness units
Key topics and technical requirements
- Test specimen: 38.0 mm ± 0.2 mm wide by 70 mm ± 1 mm long; orientation specified for machine direction (MD) and cross direction (CD).
- Test geometry: bending length 50.0 mm ± 0.1 mm; default bending angle 15° (7.5° permitted for thick boards).
- Apparatus: Taber‑type tester with pendulum and clamp, vertical driven disc with driving arms and rollers, fixed annular scale, and calibrated loading weights. Key instrument tolerances are specified (e.g., roller gap ~0.33 mm ± 0.03 mm; pendulum loading distance 100.0 mm ± 0.1 mm).
- Procedure: condition specimens per ISO 187, sample per ISO 186, place specimen in clamp, take readings by deflecting left and right. Obtain at least five valid tests per direction (ten readings: five left + five right) and average them.
- Calibration & preparation: regular instrument calibration following manufacturer instructions; check for worn clamp faces and level the instrument.
- Calculations:
- Report bending resistance as the mean bending moment (mN·m), to three significant figures.
- Conversion from Taber units to SI: multiply Taber stiffness reading by 0.098066 to obtain mN·m.
- Bending resistance index (optional): normalizes bending resistance by grammage^3: index = (bending resistance × 1000) / (grammage^3).
- Scope limits: intended primarily for high‑grammage papers/boards; does not cover the low‑range Taber instrument using a 10 mm bending length.
Applications and users
- Quality control and R&D in paper and paperboard manufacturing
- Packaging and converting industries assessing stiffness and handling performance
- Test laboratories and certification bodies performing standardized mechanical tests
- Product engineers comparing bending behavior across grades and basis weights
Practical benefits include repeatable stiffness measurement, comparability across labs (when conditioning and calibration requirements are met), and a normalized index to account for grammage.
Related standards
Use ISO 2493-2 when you need a standardized, reproducible Taber‑type measurement of bending resistance for paper and board, especially for heavier grades where bending stiffness is a key performance attribute.
