Mercerised Cotton.
In 1844 the English calico printer, John Mercer, observed that cotton went through some fundamental changes when treated with concentrated caustic soda. The fibres become straighter, stronger and take on a sheen or lustre. This process ("mercerising" as we say in the trade) improves the strength, abrasion resistance and moisture aborbency of cotton, and allows us to dye it brighter colours. Socks made from mercerised cotton absorb sweat and wear much better than socks made from cheap untreated cotton.