How Wool Works
Wool hates water, but loves mist. The scales (cuticle) of the wool fiber repels water, but allows vapor to infiltrate thru the spaces between the scales where heat is released by the process of adsorption. Wool can thus absorb 30% of its weight in water without the body feeling wet and uncomfortable because the water is trapped inside the fibers.
The process of internal adsorption is very gradual, and is relatively impervious to liquid water. If you fall in a river and reach dry land within minutes, your wool will be wet on the outside, like your hair, but will not have absorbed any water internally. So it will dry quickly. The behavior of cotton is the opposite. Typical cotton garments will immediately soak up as much water as they can hold, and wet cotton fiber is wet on the inside and the outside, so it pulls immense amounts of heat from your body. Cotton Kills. We do not use cotton thread in WeatherWool garments … most woolens are sewn with cotton thread because it is cheap and convenient, but wool will slowly wick water from wet cotton.
One of the important factors separating WeatherWool from inferior woolen garments is that WeatherWool Fabric is pure wool. Most woolen garments contain significant amounts of cotton. A garment label stating “100% Virgin Wool” means that the wool in the garment has not been recycled, but it does not mean that the fabric is pure wool. WeatherWool Fabric is always pure wool because any other material will degrade performance.
When you touch wool on a cold day, it feels warm because wool is a poor conductor of heat. That is, wool does not absorb heat from your body. There are two reasons for this. First, when you touch wool, you don't touch very much of it. The structure of wool is not flat … it is very curly and kinky and on a microscopic level, its surface is very rough. So when skin comes in contact with woolen fabric, it simply does not touch as much of the wool as other fabrics. Secondly, the cellular, chemical and biophysical structures of woolen fiber are all fine insulators.
In 1858 Coulier was the first to observe that when dry wool was moved to a moist room – when it absorbed water -- it produced heat. This is known as the heat of sorption (usually considered to encompass both adsorption and absorption). Experiments have shown that human subjects can perceive the heat of sorption of water vapor by wool garments in typical winter conditions, particularly if the woolens are thoroughly dried before use. Some claim a kilogram of merino wool can release as much heat over 8 hours as an electric blanket. This is just one of the reasons wool keeps you warm even when it is wet. So woolens are the rare exception to the clothing rule - they generate heat.
Why We Get Cold!
Most clothing is insulation; it does not provide heat. But the hunman body is an engine that emits lots of heat and moisture. Wool has evolved as a great medium for survival and comfort in a wide range of conditions.
Our skin radiates heat into the air. That warming air, which is lighter than cold air, rises up and away from the body. This convection increases with wind. Even in mild temperatures hypothermia can set in.
Heat loss is also exacerbated by metals and water, which conduct heat quickly. Perspiration greatly quickens our loss of heat. Wet skin loses heat up to 25X faster than dry skin. In the cold, avoid getting sweaty or wearing jewelry. Sit on a fallen tree rather than a stone or cold ground. And rest your feet on a large branch or thick moss if possible.
Heat is also lost when cold air is inhaled. Your nasal passages heat the air going into your lungs. Breathe through your nose, not your mouth.
The body prioritizes where to maintain essential heat. Blood flow to arms and legs is reduced in order to maintain heat around vital organs and the head. The head receives about 25% of human blood flow. A head without a hat funnels body heat away. If your feet are cold -- put on a hat!
Dress in Layers
Start with a base layer next to the skin. Base layers are designed to wick moisture away from skin. Cool and cold-weather base layers will also insulate and capture the heat contained in moisture released from the body.
Mid-layer adds extra insulation of air. In cold weather with low activity level, a thick layer is needed.
Top layers help insulate, regulate heat and moisture loss, and provide overall protection from elements. Outer layers also must handle abrasion, resist flame, odors, stains, dirt and electric-arc, and be absolutely silent. The ideal outer layer will also feel luxurious, provide concealment in nature and be admired in social settings. We recommend a storm shield for extreme wind and rain conditions.