Frosted Feet — Sock Materials and Warmth | frostedfeet.com
Merino, cotton, bamboo and synthetics compared by moisture uptake, drying speed and warmth.
The table below puts the common sock fibres side by side using the numbers that matter for warmth: how much moisture each holds by weight, how fast it dries, and whether it keeps insulating once damp. Merino wool fibre is generally under 24 microns in diameter, with superfine merino running 15–18.5 microns, and staples commonly 65–100 mm long, which makes yarn smoother against skin.
Cotton absorbs about 7% of its weight in moisture and dries slowly, chilling feet in cold weather. Polyester holds under 1% of its weight in moisture and dries several times faster than cotton. Wool keeps insulating when damp because the fibre traps air even after absorbing moisture.
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Bamboo and other regenerated cellulose fibres behave more like cotton than like wool: they take up moisture readily and dry slowly compared with polyester. They can feel soft and cool in warm conditions but are a poor first choice for cold, wet use unless blended with wool or a quick-drying synthetic.
Nylon or polyamide at 10–25% in the heel and toe roughly doubles abrasion life without changing warmth much. Elastane at 2–5% keeps the cuff up without tight bands. A 200–400 gsm terry-loop sole adds cushioning and insulation for winter walking.
Read the table by column, not by fibre name. A sock with 20% wool and 80% polyester behaves mostly like polyester; a sock with 70% merino and a 300 gsm terry sole behaves mostly like wool. The blend percentages, not the headline fibre, decide how the sock performs.
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