Cotton

Cotton fibre is almost pure cellulose, grown by the plant as a hair to carry its seeds on the wind. Each fibre is a collapsed tube with a natural twist along its length, and that twist is why cotton spins into yarn so readily — the fibres lock against one another mechanically in a way that smooth synthetic filaments do not.

It absorbs water rather than repelling it, taking up a quarter of its weight without feeling wet, which is what makes it comfortable next to skin and useless as an outdoor layer in the cold.

Cotton was domesticated independently in the Old World and the New, and was a luxury import into Europe until mechanisation reversed the direction of trade. The spinning jenny, the water frame and the power loom were all built for cotton, and the cotton mill is the original factory — the industrial revolution's first and defining industry.

That industry rested on slave labour in the American South, and the connection is not incidental to it. The cotton gin, which mechanised the separation of fibre from seed, made short-staple cotton profitable across a vast area and expanded slavery rather than reducing the demand for it.

Cotton is the most produced natural fibre in the world and has been losing share to polyester for fifty years, on price and on performance in nearly every measure except comfort.

Its environmental account is dominated by water and pesticide. Cotton is a thirsty crop grown largely in dry places, and the Aral Sea is the standard illustration of what irrigating it at scale can do. Against that, it is a renewable material that biodegrades, which is the argument its defenders make and the one that matters against microplastic shedding from synthetics.