What makes some clothing materials “warm when wet” (like wool) but others not (cotton)?


What makes some clothing materials “warm when wet” (like wool) but others not (cotton)?

In: Chemistry

Going from memory of what I learned in Boy Scouts in the 1970s, wool fibers are hollow and naturally insulating because of the dead air space inside. Plus, they don’t absorb water like cotton, the water just sits on the surface and can easily evaporate. Water inside the cotton fibers takes forever to evaporate and conducts heat away from your body while it’s in there.
Here’s an experiment: find a wool sweater and a cotton sweatshirt of similar size and weight. Weigh them dry and then wet. The cotton garment will gain massively more weight by proportion, and is heavier even after you’ve wrung it out.

In the case of wool and cotton it is the individual strands that make the difference.

Wool is rather none porous (it’s just hair) and ends up coating itself with natural oils (from your skin, or if raw, the sheep’s) that help repeal water. It is a very curly/crinkly material and this creates many pockets of air that warm up and act as insulation.

Cotton is a porous plant fiber (absorbs oils and water into it internal structure) that is significantly straighter. The straightness of the fiber helps create a smoother fabric that lays against the skin rather than poking into it (not itchy, yea!) but is less effective at creating air pockets for insulation.

I don’t know about the fiber part of this question.

I do know that wetsuits work by trapping a small amout of cold water near your skin which your body heats up. Keeping you warmish.

Whisking fibers is probably the answer your looking for.