Tightly woven fabrics

The first such fabrics consisted of cotton fabrics impregnated with waxes and oils to provide a degree of waterproofness and vapour permeability.

A permeable water-repellent finish based on stearamido derivatives was then applied to the fabric. This fabric has a high vapour permeability in air but, when immersed in water, the fibres swell and block the interstitial voids between the cotton threads.

Some contemporary fabrics are tightly woven from continuous filament micro-fibre yarns. It is claimed that the very small interstices between the fibres and yarns allow vapour to pass through the fabric but prevent access by liquid water.

Hydrophobic fluorocarbon finishes are used to increase the water resistance of the fabrics.