Overview
ISO 2758:2014 specifies a standardized laboratory method for measuring the bursting strength of paper by applying increasing hydraulic pressure to a test piece supported on an elastic diaphragm. The method applies to papers with bursting strengths from 70 kPa to 1 400 kPa and gives procedures for apparatus, calibration, sampling preparation, test execution, result calculation and reporting. This fourth edition (2014) is a minor revision of earlier editions and adds precision data.
Key topics and technical requirements
- Test principle: A circular test piece is clamped over an elastic diaphragm and bulged by hydraulic fluid until rupture; bursting strength is the peak pressure recorded.
- Applicable range: 70–1 400 kPa bursting strength; use ISO 2759 for combined-board components.
- Apparatus essentials:
- Clamping system with concentric, flat, parallel faces; clamping pressure reproducible up to 1 200 kPa (Annex A–C provide dimensions and checking procedures).
- Diaphragm: natural or synthetic rubber 0.86 mm ± 0.06 mm thick; bulge-height and stiffness requirements specified (bulge 9.00 mm ± 0.2 mm at ~30 kPa ± 5 kPa).
- Hydraulic system: motor-driven piston, suitable non-aerated fluid (e.g., glycerol), pumping rate 95 ml/min ± 5 ml/min.
- Pressure-measurement accuracy: ±10 kPa or ±3%, with response ensuring peak-pressure capture within ±3% (see Annex D for calibration).
- Sampling & conditioning: Test pieces must be representative and conditioned per ISO 187; sampling guidance reference ISO 186 and grammage per ISO 536.
- Test routine: Typical valid-test counts-20 tests if single-surface reporting; 10 valid tests per side where separate surface results are required.
- Results & reporting:
- Report mean bursting strength (nearest 1 kPa) and standard deviation.
- Compute burst index = p / g (bursting strength p in kPa divided by grammage g in g/m²) to three significant figures.
- Test report must reference ISO 2758 and include instrument type, conditioning, test location/date and any deviations.
Applications and users
ISO 2758:2014 is used by:
- Paper manufacturers and mill laboratories for quality control and specification compliance.
- Independent testing laboratories and certification bodies verifying burst performance.
- Converters, printers and buyers who specify paper performance for packaging, labels and technical papers.
- R&D teams investigating material strength, formulation changes or process effects.
Practical benefits include consistent, reproducible burst-strength data for product specifications, material selection and quality acceptance.
Related standards
- ISO 2759 - paper and board bursting strength method for boards/components
- ISO 186 - sampling for average quality
- ISO 187 - conditioning and standard atmosphere
- ISO 536 - grammage determination
Keywords: ISO 2758:2014, bursting strength, burst index, paper testing, diaphragm method, clamping system, hydraulic pressure, paper quality control.
