Why do some fabrics pill and others do not?

Pilling is usually blamed on cheap fabric, and cheapness is only a proxy. The real predictors are fibre length, yarn twist, fabric structure and fibre strength, and you can assess all four in a shop with your hands. That matters because pilling cannot be designed out after purchase — you can shave a garment forever, but a fabric that pills will keep pilling.

Step by step

1. Watch the fibre ends migrate.Spun yarn is made of short fibres, called staple, held together by twist. Every fibre has two ends, and abrasion works those ends out of the yarn until they stand proud of the surface as fuzz.
2. Watch the fuzz entangle.Continued rubbing rolls that standing fuzz into a small dense ball. It is still attached to the fabric by a handful of anchoring fibres that run back into the yarn.
3. Ask how strong the anchor is.This is the decisive step. On wool or cotton the anchor fibres are relatively weak, and the weight and drag of the pill breaks them, so the pill falls off. On polyester, nylon or acrylic the anchors are far too strong to break, so the pill stays and more form around it.
4. Understand why blends are the worst case.Mix a weak fibre with a strong one and the weak fibre migrates out to form the pill while the strong fibre anchors it permanently. A cotton and polyester jumper pills worse than either fibre would alone.
5. Look at staple length.Long-staple fibre has fewer ends per unit of yarn, so there is less to migrate. This is why long-staple cotton and long-fibre wool cost more and pill less, and why very fine short fibres like cashmere pill early.
6. Look at yarn twist and fabric structure.Tight worsted-spun yarn holds its fibres in; soft woollen-spun yarn releases them. A smooth woven face pills less than a loose knit. A brushed or napped finish has been deliberately fuzzed at the factory and will pill.
7. Locate where it happens.Pills form where abrasion is: underarms, the inner sleeve against the body, the seat, rucksack straps, seatbelt lines and anywhere a coat lining rubs a jumper. A jumper that pills only under the arms is being rubbed, not badly made.
8. Treat by cutting, not pulling.A battery fabric shaver cuts the pill off flush. A sweater comb does the same more gently on fine knits. Pulling a pill off by hand takes intact fibre with it and thins the fabric.

Tips

• Wash inside out and in a mesh bag. Most abrasion in the life of a knit happens in the drum, not on the body.
• The pilling on a new cashmere or lambswool jumper in the first month is fibre the yarn was always going to shed. Comb it out and it stops.
• Acrylic is the classic offender: cheap, short, strong fibre in a soft-spun yarn. It fuzzes early and never releases the pills.
• Coat linings are a common hidden cause. A rough or worn lining abrades the jumper underneath it every time you move.
• In a shop, rub the fabric briskly against itself for ten seconds. If fuzz appears immediately, it will pill.

Common mistakes

• Assuming pilling means poor quality wool — Fine luxury fibre pills readily because it is short. Pilling that stops after a few weeks is normal; pilling that never stops indicates a strong synthetic anchor fibre.
• Using a razor blade on a fine knit — It works but it is very easy to catch and cut the fabric itself. A guarded fabric shaver has a screen for exactly that reason.
• Washing knitwear with towels, jeans or anything with a zip — Those items are abrasive, and the drum is where the fuzz gets generated.

Questions people ask