When the term weatherproof is used to describe something, it indicates that the object is resistant to environmental elements, either by natural design or due to its surface being treated. In the case of weatherproof clothing, the latter applies. Generally, the element of most concern is water, since its passage through the garment can make one physically uncomfortable and inhibit mobility. This is why most outerwear designed for outdoor activity, such as ski clothes and jackets, is enhanced to be waterproof.
In order to keep out water, the garment’s material, which may be natural or synthetic, must be sealed. This barrier may be applied during the manufacturing process, or after the point of purchase. For example, coating the finished garment with a specially formulated spray can make it waterproof. However, this treatment is not permanent and must be repeated periodically. To make weatherproof clothing that is permanently resistant to moisture, the fabric surface must be infused with a laminate, such as polyurethane or polyvinyl chloride.
Not all types of weatherproof clothing are the same, however. In fact, there are degrees of weatherproofing that depend on the treatment and even fabric structure. For instance, weatherproof garments deemed “breathable” are made of material that can withstand hydrostatic pressures greater than 9.8 kilopascals (kPa) without letting water in. At the same time, the material “breathes” to permit internal water vapor to escape, meaning that it wicks sweat to the surface where it can evaporate.
Some types of weatherproof clothing are directional textiles. That is, they are made of breathable fabrics that also direct water and moisture away from the body without the need for lamination. In fact, these specially designed fabrics spread water more efficiently to the surface without allowing it to pool. This is advantageous since even breathable weatherproof clothing can loose its ability to resist moisture under very cold, wet conditions.
One of the best-known brands of weatherproof outerwear is GORE-TEX®. The secret to the success of this line of outdoor gear lies in the construction of its fabric, which was originally designed to make tents. The material consists of a thin layer of expanded fluoropolymer that is coated with a layer of nylon or polyester-bonded urethane. The result is a porous but dense fabric with a matrix of approximately 9 billion pores per square inch (1.4 billion per square centimeter). Since each pore is roughly 20,000 times smaller than a single drop of water, the material wicks sweat but does not allow water to penetrate.