Outdoor clothing that protects you against rain can be essential when hiking in wet weather, so it is essential that hikers understand how waterproof jackets work in order to select one suitable to their individual needs.

While PFASs remain widely prevalent in outerwear production, significant strides are being taken to identify alternatives. This year The North Face introduced high-end shells with fabric free of PFASs; Helly Hansen introduced Lifa Infinity Pro as part of their range this fall.

Waterproof Membranes

Waterproof and breathable fabrics utilize diffusion to stop air (wind) and rain from penetrating their outer layers while still permitting sweat moisture vapor produced during your sweat to escape through its pores. It takes an impressively thin material to achieve this task successfully.

History has seen various membrane technologies employed for waterproof and breathable outdoor apparel. Victorian Mackintosh used rubber between fabric layers; for 40 years afterward it was unrivaled only by Gabardine (tightly woven cotton thread proofed with wax). Gabardine eventually gave way to Grendel and finally Ventile as climbers successfully scale Everest and both Poles today.

For optimal breathable and waterproof shell layers, the ideal materials consist of durable face fabric with a membrane bonded directly onto it or combined with insulation and drop liners. In some instances a DWR coating is also applied to prolong its life and ensure that water repellency remains effective.

Water-Repellent Coatings

Waterproof jackets feature a membrane that prevents rain or snow from penetrating the fabric, and features microscopic pores too small for water droplets but large enough for sweat vapor molecules to pass through. As such, waterproof jackets offer both rainproof and snowproof capabilities while still offering comfortable ventilation and breathability.

Durable Water Repellent (DWR) treatments are increasingly common on technical outdoor clothing and gear, such as tents and bags. DWR makes fabrics more resistant to water penetration by causing droplets of moisture to bead up and roll off their surfaces more readily.

Nikwax provides an easy and long-lasting aftercare product known as DWR Reactivator that doesn’t rely on fluorine – perfect for protecting the environment while prolonging product lifecycle and performance in outdoor settings. Reapply it periodically on clothes or equipment with water repellent properties such as jackets or bags to revitalize their water repellency properties to extend lifespan and provide optimal outdoor performance.

Non-Breathable Coatings

Modern waterproof-breathable fabrics help us stay dry by blocking precipitation while still allowing perspiration vapors to escape, helping keep clothing and body layers dry while providing comfortable exertion levels in various climates.

Many reputable outdoor brands use proprietary waterproof-breathable materials in their apparel – Gore-Tex and EVent are two examples.

Waterproof ratings measure the ability of jackets to withstand rain, while breathability testing uses an approach known as accelerated moisture transfer. REI Co-op employs a standard of 3 psi waterproof factor; some brands may claim higher ratings that don’t correspond with real world performance:

As a general rule, all fully waterproof jackets feature water-repellent treatments like DWR. This coating prevents water soaking into the outer face fabric from wetting out (wetting out), which could reduce breathability and make you cold. Fabrics may be reproofed using spray-on treatments like Nikwax TX Direct but it is best to let it dry completely between applications of Nikwax.

PFASs

Per- and Polyfluoroalkyl Substances (PFASs) are synthetic chemicals used in many industrial and consumer products, from nonstick cookware and firefighting foam to waterproof rain jackets. Unfortunately, however, PFAS are difficult to break down in the environment and may accumulate over time, negatively affecting ecosystems as well as humans.

Gore-Tex, Icebreaker and prAna have all made major commitments to eliminating PFAS from their products starting with 2019; while Gore-Tex made significant progress toward eliminating long-chain PFAS usage and replacing it with safer alternatives in its membranes.

Other brands have pledged to phase out PFAS altogether by 2025; however, many do not yet have suitable replacement materials ready. When shopping for textiles free from harmful substances such as PFASs, seek gear certified OEKO-TEX. Kari Traa, founded by an Olympic mogul skier, uses responsibly sourced down and a Gore-Tex Membrane free from these hazardous compounds in its Beta Lightweight Jacket.