Overview
ISO 3689:1983 - Paper and board - Determination of bursting strength after immersion in water - specifies a laboratory method to measure the wet strength (bursting strength) of paper and board after controlled immersion in water. The procedure is applicable to most types of paper and board when an appropriate immersion time is agreed between the interested parties. Results can vary with re‑testing after time has elapsed.
Key topics and requirements
- Scope: Measures bursting strength after a defined period of immersion to assess wet strength and strength retention.
- Sampling and test pieces: Specimens selected per ISO 186; test piece preparation follows ISO 2758 (paper) or ISO 2759 (board). Ten test pieces are normally used for the wet bursting test; larger numbers may be required for multiple bursting.
- Apparatus and materials:
- Burst tester complying with ISO 2758 or ISO 2759.
- Thermostatically controlled water tank large enough for vertical immersion.
- Use distilled or deionized water for soaking.
- Immersion procedure:
- Test pieces immersed vertically with the long side 25 ± 2 mm below the water surface; corrugated fibreboard must be immersed with flutes vertical to avoid trapped air.
- Typical immersion times cited as examples: 1 h ± 1 min for papers, 2 h ± 2 min and 24 h ± 15 min for boards - actual time must be agreed by parties.
- After immersion, specimens are lightly blotted and tested immediately.
- Testing and orientation: Carry out five replicate tests with the top side uppermost and five with the wire side uppermost.
- Results and reporting:
- Results may be expressed as mean bursting strength (kPa), mean burst index, or bursting strength retention (%).
- Test report must include reference to ISO 3689, type of tester, mean/min/max values, immersion time and temperature, standard deviation, and any optional items or deviations.
Applications
- Quality control and acceptance testing of paper and board used where wet strength matters, such as:
- Packaging for humid or wet environments (liners, cartons, sacks)
- Paperboard used for liquid‑contact products or moist processing
- Corrugated materials where moisture resistance affects performance
- Research & development of wet‑strength additives and treatments.
- Procurement and specification verification between suppliers and buyers.
Who uses this standard
- Paper and board manufacturers
- Converters and packaging engineers
- Quality assurance and materials testing laboratories
- R&D teams developing wet‑strength formulations
- Specifiers and buyers setting acceptance criteria
Related standards
- ISO 2758 - Paper - Determination of bursting strength
- ISO 2759 - Board - Determination of bursting strength
- ISO 186 - Sampling for testing
- ISO 187 - Conditioning of samples
Keywords: ISO 3689:1983, paper and board, bursting strength, wet strength, immersion in water, wet testing, ISO 2758, ISO 2759, ISO 186, ISO 187.
