Introduction to Backpacking Clothing ----
Credit to Rick Curtis, Outdoor Action Program, Princeton University
This list is designed for basic multi-day backpacking trips in temperate forest conditions in the United States. Typical temperature ranges would be 30's - 50+ Fahrenheit during the day with evening temperatures from 10's - 30's Fahrenheit.
Fabrics
The clothing layers should consist of several different types of fabrics. Cotton should be avoided in cold conditions. Cotton absorbs and retains water, and therefore it will not keep you warm if it gets wet. Also it can be difficult to dry.Polypropylene or other hydrophobic synthetic fabrics move the moisture (sweat) away from your body to the outside of the layer, reducing evaporative cooling and keeping you dry and comfortable. Wool or synthetic pile/fleecefabrics don't absorb water so they keep you warm even if they get wet. Pile also dries very quickly. A wool sweater or pile jacket provides warmth on a chilly evening. Nylon or Nylon/Cotton Windshells reduce convective heat loss. For raingear, coated nylon is lightweight and works well. Waterproof-breathable fabrics are also possible but are expensive.
The Layering System
Combinations of these types of fabrics creates a layering system. The purpose of a layering system is to be able to mix and match the layers of insulation to match the weather conditions and your activity level to maintain a comfortable body temperature without excess sweating (which can lead to heat loss). ). Throughout the day you will need to layer up and layer down as conditions and activity levels change. Typically in the morning and evening when it is colder, you will need many layers on.
The inner layer keeps the skin dry and comfortable. The middle layer provides some insulation and protection from the elements. The outer layer provides insulation.
The shell layer protects you from wind and rain. A waterproof rain jacket is essential in case of bad weather. The head layer is to reduce heat loss. The feet layer is actually two layers. You should wear a lightweight synthetic liner sock against your foot which helps pass moisture away from your foot. On top of this you wear a wool/nylon blend hiking sock. People wonder why you should wear two socks. Since wool doesn't absorb water it passes the moisture from your foot outwards, keeping your foot dryer. If your feet stay damp, they get wrinkled and are more prone to blisters. Having two sock layers means that your socks will slide against each other so that the friction from your boots is between the sock layers rather than against your skin (friction against the skin leads to blisters).