Overview
ISO 5636-6:2015 specifies the Oken method for determining the air permeance and air resistance of paper and board. The standard defines the test principle, apparatus (water-column and electronic sensor Oken testers), sampling, conditioning, calibration and test procedure, and how to express results. It covers a wide measuring range for medium-range permeance and resistance but is unsuitable for rough-surfaced materials that cannot be securely clamped.
Keywords: ISO 5636-6:2015, Oken method, air permeance, air resistance, paper and board testing, Oken tester.
Key topics and technical requirements
- Test principle: A test piece is clamped under a circular gasket; air flows through a controlled capillary into the space between capillary and specimen. The resulting pressure is measured and converted to air permeance or air resistance.
- Apparatus types:
- Water-column Oken tester: uses a water-column manometer and a constant-pressure chamber maintained at about 4.90 kPa (≈500 mmH2O); includes a capillary (≈0.4 mm inner diameter, ~54 mm length adjusted for calibration) and specific gasket dimensions.
- Electronic sensor Oken tester: replaces the water-column with an electronic pressure sensor, amplifier and digital display.
- Gasket and measurement area: standard gasket geometry and hardness are specified to ensure a reproducible measurement area and prevent leakage.
- Sampling & conditioning: sampling per ISO 186; conditioning per ISO 187; test pieces prepared in the same atmosphere as conditioning.
- Test piece count & sides: at least 10 test pieces (commonly five measurements with each side up); report means for both sides and overall.
- Calibration & leakage checks: zero-pressure verification, capillary adjustment, and leak tests using impermeable sheets are required.
- Result units: air permeance reported as micrometres per pascal second (μm/(Pa·s) or ml/(m·Pa·s)); air resistance as seconds per 100 ml (s/100 ml).
- Annexes: includes measurement principle relations (Oken vs Gurley) and precision data.
Applications and who uses it
- Paper and board manufacturers use ISO 5636-6 for quality control of porosity related to printing, coating, converting and packaging performance.
- Converters and printers assess air flow properties that affect ink transfer, drying and runnability.
- R&D and materials labs characterize new substrates and compare permeance between grades.
- Test houses and certification bodies perform standardized, repeatable assessments for specifications and compliance.
Practical considerations: choose the water-column or electronic Oken tester based on throughput and precision needs; avoid testing highly textured or rough materials that cannot be clamped without leakage.
Related standards
- ISO 5636 series (other methods): Part 3 (Bendtsen), Part 4 (Sheffield), Part 5 (Gurley)
- ISO 186 (sampling), ISO 187 (conditioning), ISO 48 (rubber hardness)
- Annexes in ISO 5636-6: measurement principle and precision data for method comparison and uncertainty assessment
This standard is essential for consistent, repeatable measurement of air permeance and resistance in paper and board using the Oken tester.