Before delving into the world of waterproof sock technology, it may help to understand the question behind the question - how important are dry feet? For those who like to hike, walk, garden, exercise or work outdoors, dry feet are very important indeed.
The human foot contains an abundance of sweat glands. Many times the produced sweat becomes water vapor and evaporates into the air, creating a cooling effect for the feet. The problem is that most people do not spend their entire days barefoot, so this natural evaporative cooling process is compromised. Socks made from breathable material such as cotton act as a wick, drawing most of the moisture away from the foot. This build-up of moisture has nowhere to go within the confines of most shoes, however, so the result is a damp foot surrounded by a damp sock.
As a person walks, the fabric of the wet sock rubs against the surface of the foot, causing minor abrasions. These abrasions sometimes escalate into the dreaded formations called blisters. Spreading absorbent foot powder into socks and shoes or changing into drier socks may temporarily keep the area dry. But the cumulative effect of too much moisture and not enough evaporation will continue with the use of regular socks. Socks can also crease during wear, causing even more irritation and friction.
A better way to keep feet dry is through the use of waterproof socks. Waterproof socks typically use a three-layer construction to draw away excess moisture from the foot and repel water from the outside environment. The innermost layer of a waterproof sock is generally made from a breathable but absorbent material such as natural wool or a proprietary acrylic blend. The second layer of a waterproof sock is where technology enters the picture. A plastic laminate with extremely small pores is attached to both inner and outer layers. These pores are large enough to allow the relatively small water vapor molecules from sweat seep through to the outside, but tiny enough to prevent the larger molecules of rain and other water from entering. The result is a one-way vapor barrier between the foot and the outside environment.
The outer layer of most waterproof socks is usually a watertight synthetic material such as Spandex or Lycra. This tightly-woven and elastic material repels water but still allows the skin to breathe. A material such as rubber or plastic would also repel water, but not allow the accumulated sweat to escape into the air. Waterproof socks must perform a balancing act in order to draw sweat and other moisture out while allowing for natural evaporation. If the sweat does not go through the laminate membrane at a steady rate, the result could still be a damp foot and a higher risk of blistering. Waterproof socks work best with shoes which allow sweat and moisture to escape naturally, such as athletic shoes and hiking boots.