Why clothes pill, and why some pills stay

1 October 2026 8 min readApolyth

A pill is not dirt. It is mostly the garment's own fibre, pulled loose, tangled into a knot and still tied on, sometimes with lint caught up in it. Whether it falls away or stays depends largely on how strong the fibres holding it are.

How a pill forms

In 1959 Daniel Gintis and Edward Mead filmed fabrics being abraded and watched it happen. The rubbing caught exposed lengths of fibre and pulled them into loops, which opened into fuzz. Once the fuzz was dense enough, a pill formed quickly: the fibres twisted and tangled, drawing in their neighbours. As the rubbing went on, the pills wore away. How badly a fabric pills, they concluded, depends on three rates: how fast fuzz forms, how fast it tangles, and how fast pills wear off. A 2021 paper reviewing earlier studies describes the same process in four steps: fuzz formation, entanglement, growth and wear-off.

Each stage answers to something different. In Gintis and Mead's work, friction between fibres, and their stiffness, mattered for how readily fuzz formed. Tangling tracked fineness, cross-sectional shape and stiffness. Wear-off "was determined by abrasion resistance and tenacity", tenacity being the fibre's strength.

Why polyester tends to keep its pills

A pill stays as long as the fibres anchoring it hold. A 1987 patent assigned to Celanese states the explanation as it then stood: pills "may be more or less permanently attached to the fabric's surface by one or a few synthetic polymeric fibers extending out of the fabric which will resist breakage as surface abrasion continues." The theory, it adds, is "supported by the general lack of the retention of undesirable fuzz balls on the surface of a fabric consisting solely of cotton fibers". A 1981 Celanese patent names the trade: polyester's strength and abrasion resistance "are desirable from the point of view of good durability in wear, but they prevent a rapid tearing off, breaking or rubbing off of the nodules".

Blends show the mechanism clearly. A 2020 study of polyester-cotton cloth found that the cotton fibres in the surface fuzz break and are wrapped by polyester fibres to form pills. The 2021 paper's review reports that fabrics of 100 per cent cotton pilled less than cotton-polyester blends, though they also resisted abrasion least.

The industry's answer was to make polyester weaker. The 1987 patent describes a fibre with a strength "closer to that of natural fibers such as cotton". A 1999 patent assigned to Akzo Nobel describes the established version of the idea, polyester made weak enough "that the fiber ends and pills which have emerged break off rapidly as in the case of natural fibers", and its cost: a loss of about 40 per cent of the fibre's strength, which leaves it "very susceptible to damage" in later processing. The same patent calls pilling a problem "not even fully solved today".

What makes a cloth pill more

The 1981 patent also lists what a textile manufacturer can do: use long staple fibre, a coarse yarn, pronounced crimp, high twist, doubled yarns instead of single ones, short floats in weaving, and "a tight weave or close loops". Staple means fibre in short lengths, as cotton grows, rather than one continuous filament. A float is a length of yarn that passes over several crossing yarns before it is woven in.

The 2021 paper's review of earlier work agrees on much of this. With higher twist, fibres slip less and less hairiness floats on the surface, so the tendency to pill falls. One study it cites found woven fabrics pilled less than knitted ones; other studies it cites found that weaves with shorter floats pilled less than those with long. Fabrics from carded yarn, spun from fibre brushed into line but not combed, did worse than fabrics from combed yarn; combing, Cotton Incorporated notes, is the step that removes short fibre. Singeing, which burns the surface fuzz off, cropping, which shears it, and heat setting all significantly reduce the tendency to pill. Gintis and Mead found that heat-setting polyester stiffened it, which reduced fuzzing.

How pilling is tested

There are several machines for making a fabric pill in the laboratory. ISO 12945 has a pilling box that rotates with the specimens inside (Part 1), a modified Martindale tester that rubs fabric against fabric in a looping pattern (Part 2) and a random tumble tester (Part 3), with Part 4 setting out the visual assessment. ASTM has its own methods: random tumble (D3512), in which specimens tumble in a cork-lined chamber; Martindale (D4970); a brush tester (D3511), meant mainly for upholstery and other heavy fabrics because it is "highly abrasive"; and an elastomeric, or rubbery, pad (D3514).

Grading is by eye. Tested specimens are compared with standards, real fabrics or photographs, and rated "on an arbitrary scale ranging from 5 (no pilling) to 1 (very severe pilling)". ASTM advises against grading by counting pills alone, because size, contrast and fuzz matter too, and counting takes too long.

The standards are frank about their limits. D3512 is not recommended for acceptance testing because "the between-laboratory precision is poor". For D4970, "interlaboratory data are not available". Both state that pilling in actual wear "varies more with general conditions of use and individual wearers than in replicate fabric specimens subjected to controlled laboratory tests".

The machines also disagree with each other. A 2002 comparison of the Martindale, the pilling box and the pilling drum found each sensitive to different fabric properties, with the Martindale generally giving worse grades, and recommended using at least two testers. A 1989 study found random-tumble ratings rose with a fabric's abrasion resistance and tenacity, while elastomeric-pad ratings fell. A grade of 4 is a 4 on a particular machine.

What can be done at home

Pills come from rubbing, and a washing machine rubs. In a 2013 study of a cotton plain weave, washes of 90 minutes left worse pilling grades than washes of 30, and hotter washes were generally worse than cooler ones. The authors' summary is that cloth washed long, hot and often pills more. Twenty repeated washes gave mixed results, which they put down partly to loose surface fibre washing away and partly to how subjective grading is.

Turning a garment inside out before washing is common advice, and it follows from the mechanism, since it moves the rubbing to the inside face. No controlled study of it turned up in the research for this piece.

Composition says whether pills are likely to leave on their own. On all-cotton cloth they tend to break away as their anchors wear. Where polyester is in the yarn, they tend to be held, unless the polyester is a low-pill type. Held pills have to be cut or teased off. A 2014 patent for a de-pilling tool sums up the alternatives it set out to improve on: an electric fabric shaver cuts only the pills that fit through the holes in its guard; volcanic stones and coarse sand combs work by gentle abrasion; and a brush used carelessly can damage the cloth.

Sources

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