Microns decide
Prickle depends on fibre diameter. Above about thirty microns, fibre ends are stiff enough to trigger nerve endings in the skin.
- Fine merino: under 19 microns. Soft next to skin, thermoregulating, low odour.
- Lambswool: first shearing, uncut tips, so softer at equal diameter.
- Mohair: angora goat. Lustrous, light, very warm, with a characteristic halo.
- Cashmere: goat undercoat, around 15 microns. Warm and light, but delicate.
Pilling
It comes from short fibres migrating out of the yarn under friction. Long, well-twisted, well-spun yarn pills little; cheap cashmere made of short fibres pills from the first wearings.
So it is not a care failure but an indicator of spinning quality — and you can test it by discreetly rubbing a sleeve between two fingers before buying.
A pilling jumper can be shaved with a knitwear stone or a fabric shaver. After two or three passes the short fibres are gone and it stops. A quality garment improves this way; a poor one thins.
The care that matters
Wool soils slowly and airs well. A jumper worn three times does not need washing: twenty-four hours hanging in a cool room is enough.
When it must be washed: cold water, wool detergent, no rubbing, gentle spin, dried flat. What felts wool is not water but the combination of heat, agitation and alkalinity.
our piece on handmade objects sets out the materials that improve with time.