I was at a scout meeting the other day and someone made the comment that “cotton kills”. The Scoutmaster sitting next to me leaned over and asked, what does that mean?
Having lived in the Pacific Northwest for sixteen years and a member of a snowmobile search and rescue team for six of those, I know the phrase means to not wear cotton between Nov 15th and Apr 15th for any kind of winter backcountry activity. The reason is based on how that fabric handles moisture against your body. In fact, the best description I’ve read about this fact was in the survival book I just finished by Cody Lundin. He says on page 103 of When All Hell Breaks Loose:
Cotton is hydrophilic, meaning it transfers sweat from your skin to the material itself, thus it’s horrible at “wicking” wetness away from skin. In fact, cotton loves moisture and will become damp simply when exposed to humid air. Once wet, it feels cold, looses 90 percent of its insulating properties, is a drag to dry out, and wicks heat from your body twenty-five times faster than when it’s dry. Because of this, wearing cotton clothing in the wintertime is a death wish. Yet, in scorching deserts, it’s my fabric of choice for precisely the same reasons. Cotton also has decent abrasion resistance and blocks out a reasonable amount of 
UV radiation from the sun.
Lundin’s perspective on cotton being the fabric of choice in desert conditions was particularily interesting to me now that I live in Utah. However, I have no doubt about staying warm in winter weather by using the layering system with the following alternatives to cotton. Again, borrowing from the well-written descriptions from Cody:
Polypropylene – a hydrophobic material that “transfers moisture from the skin across the fabric itself to other clothes or the air so it actually dries from the inside out”.
Wool – made from animal hair that is hygroscopic, which means “it readily absorbs moisture but suspends the water vapor within the fiber itself”.
Polyester – another hydrophobic material used in clothing because it is “a good insulator, can absorb a fair amount of water without feeling cold and can be woven into many different thicknesses providing both insulation and wind-stopping abilities.”
Down – its “compressibility, loft, and weight-to-warmth ratio are legendary – when it remains dry. Unfortunately, down is hydrophilic and is worse than cotton in cold, wet environments, losing virtually all of its insulative properties”.
So remember the saying, “Cotton Kills!” …even a Boy Scout if he forgot what was taught in Wilderness Survival and had to spend an unexpected night with the wrong clothes in the wrong conditions (either winter or summer). What seems to be my theme here lately?? You guessed it, BE PREPARED!!
[UPDATE: see also Calipene by Patagonia as another baselayer alternative to cotton]
