How to judge cashmere before it pills, and what "grade A" actually means

Cashmere is sold on feel, and feel can be faked. Softness comes from fibre diameter, but durability comes from fibre length, and the two are not the same thing. A sweater can feel extraordinary in the shop and be pilled beyond wearing by February.

The four numbers that matter

Fibre length. Longer fibres mean fewer ends, and it is the ends that work their way out of the yarn to form pills. Grade A cashmere averages around 36 mm and above. Short fibre cashmere can be under 25 mm and will pill quickly regardless of how soft it is.

Micron count. This is the diameter of the fibre in microns. Below 19 microns is considered fine, below 16.5 is exceptional and rare. Thinner is softer, but thinner fibres are also more fragile, which is why the very finest cashmere needs longer fibres to survive.

Ply. Yarn is spun from multiple strands twisted together. Two-ply cashmere resists distortion far better than single-ply, which is why single-ply garments stretch at the elbows and hem.

Knit density. Gauge tells you how tightly the fabric is knitted. A 12-gauge knit is dense and holds shape; a 7-gauge knit is loose, soft and prone to distortion under its own weight. Loose is not automatically bad, but it must be matched to the intended use.

Five checks you can do in thirty seconds

Hold it to the light. A dense, well-made knit shows little light through the body. If you can read a page through the fabric, expect distortion.

Stretch the ribbing at the cuff and release. Good cashmere springs back to shape. Poor cashmere stays stretched.

Rub the sleeve against the body for ten seconds. You are accelerating what a winter of wear will do. Loose fibre will start to ball up almost immediately.

Look at the seam where the yarn ends. If the ends look furry and frizzy, fibre length is short. Long-fibre cashmere has a smooth, almost slick yarn surface.

Check the fibre content on the label, not the marketing copy. Anything blended with nylon or viscose is not automatically bad; a small percentage of nylon can genuinely improve abrasion resistance in socks. But it should not be sold as pure cashmere.

Where the money actually goes

A cashmere sweater at the low end typically uses short-fibre Chinese or Mongolian cashmere, single-ply yarn, and a loose knit. It will feel soft and pill within weeks.

At the mid to high end, you get longer-grade fibre, two-ply yarn, a tighter gauge and finishing that includes washing and pressing. The sweater weighs more, feels slightly denser and keeps its shape after years.

The highest price tier buys rarity and brand, not durability. There is a real ceiling on how much better cashmere gets, and it is well below the top of the market.

Care, briefly

Wash cashmere by hand in cool water with a pH-neutral soap, or use a machine wool cycle in a mesh bag at low spin. Never wring it. Dry flat, away from direct heat, and reshape while damp.

Store folded, not hung, and use cedar rather than mothballs. Give a sweater a day of rest between wears so the fibres can recover, and it will last twice as long for no cost at all.

What to look for in a listing

A serious knitwear listing states fibre length or grade, micron range, ply, gauge and the mill. That is four numbers and a place name. If none of them appear, the seller either does not know or would rather you did not ask.