> The wicking needs directionality to be useful, it seems: What makes the moisture move in the desired direction, I assume you're thinking of some sort sort of

> The wicking needs directionality to be useful, it seems: What makes the moisture move in the desired direction, I assume you're thinking of some sort sort of chemical gradient. I can't comment on petro-chemical fibers but in the case of wool you have two key structures. 1. Wool has Cuticles on the surface (much like human hair) which act as shingles against large droplets (like rain). 2. Wool has a fiber Cortex which in the case of wool will adsorb liquid that penetrates past the cuticles (such as the vapour generated while sweating). Cortex adsorption is an important part of why wool in particular is special as a natural fabric. The water molecules create a chemical bond with the outter surface of the cortex of the fiber, meaning moisture is sandwiched under the outter cuticle, on the outter surface of the cortex of the fiber. This is the main reason why wet wool does not 'feel' wet against your skin. No heat exchange occurs with the water in the wool via direct conduction (you sort of aren't really touching the water it is sort of trapped in a kernel). When you 'feel' cold with a wet cotton shirt it is because the water molecules on the shirt are getting heated up by your skin heat (mostly) via direct conduction. In wool this water content is effective air gapped away from you.