The Science of Softness: What Microns Actually Mean

A micron is one-millionth of a metre, and it is the single measurement that separates cashmere that feels soft in the shop from cashmere that still feels soft five winters later. The difference between a 14-micron fibre and a 19-micron fibre is invisible to the eye and unmistakable to the hand. Here is why that number matters more than any other on a garment label.

A unit too small to see

Human hair typically measures between 50 and 100 microns in diameter. A fine merino wool fibre runs around 18 to 22 microns. Cashmere, by contrast, generally falls between 13 and 19 microns, with the finest, most prized grades — the kind that comes from goats adapted to the harshest winters — sitting at the lower end of that range. OYU's fibre is graded between 13.5 and 15.5 microns, a band narrow enough that it is measured not by eye or touch during sourcing, but by laser diffraction in a laboratory, using equipment that can register differences of a fraction of a micron across a sample of a few hundred fibres.

The number is not a marketing figure; it is a physical property with direct consequences. A finer fibre bends more easily under pressure, which the nerve endings in human skin register as softness. A coarser fibre resists bending and is felt, at a certain threshold, as prickle or itch. The threshold at which most skin begins to register discomfort sits around 18 to 19 microns — which is precisely why cashmere, sitting comfortably below that line, can be worn against bare skin in a way most wool cannot.

Why cold produces fine fibre

Fibre fineness is not a fixed trait of the species; it is a response to environment. Cashmere goats grow their soft undercoat as insulation against extreme cold, and the animals that face the harshest winters — prolonged temperatures of minus 30°C or lower, as is routine in the Gobi and the northern Mongolian steppe — tend to produce the finest, densest down relative to their body size. Goats raised in milder climates, even of the same breed, generally produce coarser fibre. This is part of why Mongolian and Tibetan plateau cashmere has historically commanded a premium: the climate itself is doing work that no amount of selective breeding can fully replicate elsewhere.

There is a second variable that matters almost as much as diameter: fibre length, typically 34 to 36 millimetres in fibre used for OYU's yarns. A fibre that is both fine and reasonably long spins into a stronger, less pilling-prone yarn than one that is fine but short and brittle. Buyers who focus on micron count alone, without checking length, sometimes end up with cashmere that feels wonderful on first touch and sheds after a few wears.

What a lab report actually says

Reputable fibre is tested and graded before it is ever spun, typically expressed as an average micron count with a standard deviation — the second figure indicating how consistent the fibres in a given batch are. A batch averaging 14.5 microns with a tight standard deviation will behave more predictably in spinning, and wear more evenly over years, than a batch with the same average but wider variation, which will contain a meaningful proportion of coarser fibres liable to work their way to the surface as guard hair over time.

Sarangerel, a fibre grader who has worked in Ulaanbaatar's cashmere trade for over fifteen years, describes the work as closer to a wine taster's than most people expect: after enough years, her fingers can estimate micron count within half a point before a sample ever reaches the lab, simply by rolling a lock of fibre between thumb and forefinger. The laboratory confirms what the hand already suspects — but the hand, she says, is what tells you whether a batch is worth testing at all.

Reading past the label

Very few brands publish an actual micron range, in part because doing so invites comparison, and in part because many blend fibre from multiple grades without tracking the composite figure closely. A specific range — not "ultra-fine" or "premium," but a number — is one of the few claims about cashmere that can be independently verified by a textile lab. It is worth asking for, the same way one might ask a wine merchant for a vintage rather than an adjective.

The sweaters graded at 13.5–15.5 microns this season are in the collection →

See also From Steppe to Sweater: A Fibre's Long Journey and Five Ways to Tell Real Cashmere From Fake, at Home.