What causes pilling, and how do you remove it without wrecking the garment?

A pill is a small ball of tangled fibre sitting on the surface of a fabric. It forms when short fibre ends work their way out of the yarn under friction, roll together, and stay attached by fibres still anchored inside. It is a measured property with its own international test standards, graded 1 to 5, and it is not the same thing as a fabric wearing out.

Why do pills form at all?

Three steps, in order.

Fuzzing comes first. Friction lifts fibre ends out of the yarn so they stand away from the surface.

Entanglement comes second. Those loose ends rub against each other and against the fabric and roll into a ball.

Anchoring is the third step and the reason the pill stays. Some fibres in the ball are still held inside the yarn, so the pill is tethered rather than loose. Strong fibres hold the ball on; weak fibres break and the pill falls off on its own, which is why some fabrics pill temporarily and then stop.

That last point explains an apparent paradox. Polyester and nylon pill more persistently than wool of similar construction not because the fibre is worse but because it is stronger, so the tether does not break.

Where does it happen, and why always the same places?

Friction decides it, which is why pills appear in the same places on almost every garment.

Under the arms, where sleeve rubs body. Along the sides, where a bag strap or an arm sits. On the inner thighs. On the seat. On the cuffs. On the back of a sweater where it meets a coat.

If a garment is pilling evenly all over, the cause is usually the wash rather than wear: too much agitation, a crowded drum, or abrasive items such as denim and zips in the same load.

Is pilling a sign of a cheap garment?

Not reliably, and this is where price is a poor guide.

Two construction choices drive it, and neither correlates cleanly with cost. The first is fibre length. Short staple fibres produce yarn with many exposed ends along its length, and every exposed end is a pill waiting to happen. Longer staple cottons such as Pima and Egyptian have fewer ends per unit of yarn and pill less. The numeric cutoffs quoted for staple length vary between sources, but the direction of the effect is consistent.

The second is yarn twist. A tightly spun yarn holds its fibre ends in. A loosely spun yarn of the same fibre lets them out, which is why a soft, airy cashmere can pill more than a crisp worsted wool despite costing far more.

So an expensive garment can pill because it was made soft on purpose. That is a design trade-off rather than a defect, and it is worth knowing before buying something described as brushed, napped or loftily spun. Our explainers on merino wool and modal go into how each fibre behaves.

Which fibres pill, and which do not?

The fibre decides how persistent the pill is rather than whether one forms.

Polyester, nylon and acrylic pill persistently, because the anchoring fibres are strong enough to hold the ball indefinitely. Acrylic is the worst offender in knitwear for exactly this reason.

Wool, cashmere and other animal hairs pill readily and often stop. The fibre is weaker, so the anchors break and the pill falls away, which is why a good wool sweater goes through a pilling phase early in its life and then settles.

Cotton pills least of the common fibres in a tightly spun yarn and noticeably more in a soft, brushed or low-twist one. Linen barely pills, because the fibre is long and the yarn is usually tightly spun.

Blends are the awkward case and the most common one. A natural fibre loosening next to a strong synthetic produces the worst of both: the soft fibre supplies the loose ends and the synthetic supplies the anchor that will not break. A cotton-polyester sweatshirt is the standard example.

How is pilling actually measured?

By standardised abrasion in a machine, then graded against photographs.

The ISO 12945 series is the international set. Part 1 is the pilling box method, originally developed by ICI, which tumbles samples in a lined chamber. Part 2 is the modified Martindale method, published as ISO 12945-2:2020, which rubs samples against each other under light pressure. Part 3 is a random tumble method using an impeller in a lined chamber. Part 4 covers assessment of fabric propensity.

The ASTM equivalents are D4970, the Martindale pressure tester method, which is generally applicable to all fabric types and particularly suitable for wovens, and D3512, the random tumble pilling tester method, which suits knits and looser structures. ASTM notes that D3512 is not recommended for acceptance testing, and should be used with caution if it is, because between-laboratory precision is poor.

Results are graded 1 to 5, where 5 means no change to the surface. When a mill quotes a pilling grade to a buyer, that is the number it means.

Does a high Martindale rub count mean it will not pill?

No, and this is the single most useful thing in this article for anyone buying upholstery.

Abrasion resistance and pilling resistance are different properties measured by different tests. Interior textile guidance makes the point bluntly: a fabric can reach 80,000 Martindale rubs and still pill badly.

A rub count tells you how long the fabric survives before it wears through. A pilling grade tells you how its surface looks along the way. A sofa fabric can be rated for heavy commercial use and still look tired in a year.

If you care about appearance, ask for the pilling grade specifically, and ask which method produced it.

What actually removes pills?

Cutting them off at the base, and the method matters more than the tool.

A fabric shaver or a sweater comb removes the pill and leaves the anchoring fibres cut flush with the surface. Work on a flat, taut surface, with the garment laid out rather than worn or held, and move in short strokes in one direction.

What makes it worse is pulling. Picking a pill off by hand pulls the anchoring fibres out of the yarn, which thins the fabric at that spot and creates more loose ends, so you are seeding the next generation of pills while removing this one.

Scissors work for a single large pill if you cut at the base without tenting the fabric. A disposable razor works and is riskier, because the blade is designed to cut at skin level rather than at fabric level and will take the surface with it on a knit.

And shaving is not a cure. It removes the symptom. The yarn construction that produced the pills is unchanged, so they will come back, which is the honest answer to why a favourite sweater needs doing twice a season for ever.

How do you stop it happening?

Reduce friction, in the wash and in wear.

Turn garments inside out to wash, which moves the abrasion to the inner face. Use a gentle cycle, cool water and a part-loaded drum rather than a crowded one. Keep knits away from denim, zips and hooks in the same load. A mesh bag helps.

Avoid the tumble dryer for anything that pills, because tumbling is literally the mechanism the test standards use to induce pilling. Lay flat to dry instead.

In wear, the things that cause it are mostly unavoidable: bag straps, seat belts, coats over knitwear. Rotating garments rather than wearing the same one every day spreads the friction, which is less of a tip than a description of the arithmetic.

This article explains a measured textile property. For a specific garment, follow the care label on it.