Why Silk:
First it is the strongest natural fiber available. Yes spider silk is stronger but you can't acquire enough cloth.
Second is that it has a very high insulative value. Yes even higher than wool on a per weight basis. It also has very good wicking properties.

Also while keeping you warm as a base layer. When used as the outer or single layer it is cool in summer.

Since it is very light weight the scarf or bandana can be much larger for the same weight and packed space it will take up.

http://www.texti.net/intersoie/uses.html
http://ezinearticles.com/?Properties-and-Characteristics-of-Silk&id=488797
http://www.towson.edu/campusrec/AP%20forms/pm%20layering.pdf
_________________________
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