Hydrostatic Head Test Methods and Acceptable Limits
Hydrostatic Head is verified through ISO 811 water penetration. Knowing how the method works avoids rejecting fabric that actually meets the requirement.
Method overview
ISO 811 water penetration defines sample size, conditioning and calculation, so values are comparable only within the same revision. Working figures for Hydrostatic Head normally sit around 1000-10000 mm depending on use in mainstream production. Note ISO 811 water penetration on the tech pack so nobody tests against an older revision.
Result interpretation
Read the value together with construction notes; 1000-10000 mm depending on use is only meaningful for similar fabrics. Record elastane content alongside Hydrostatic Head, because blends shift the measured value. A result outside 1000-10000 mm depending on use usually points to process drift rather than to the fibre itself.
Typical limits
Buyers commonly write 1000-10000 mm depending on use with a stated tolerance, then verify against ISO 811 water penetration. Keeping reference values for Hydrostatic Head lets suppliers quote without extra sampling rounds. Ask for conditioning details together with ISO 811 water penetration, since both affect the reading.
Sources of variation
Conditioning time, operator technique and shade all influence the result. Working figures for Hydrostatic Head normally sit around 1000-10000 mm depending on use in mainstream production. Note ISO 811 water penetration on the tech pack so nobody tests against an older revision.
Documentation
Record the standard revision on every report, because older versions can differ from current practice. Record elastane content alongside Hydrostatic Head, because blends shift the measured value. A result outside 1000-10000 mm depending on use usually points to process drift rather than to the fibre itself.
