Pilling is two separate failures and only the second one is visible

What a pill actually is

A pill is a tangled ball of fibre attached to the surface of a fabric by a few strands still anchored in the cloth. It is made of the garment's own material. Nothing has been added and nothing has arrived from outside, whatever it looks like when you find one on a new jumper.

Getting there takes two distinct stages. First, fibre ends work their way out of the twisted yarn and stand proud of the surface, which happens wherever the fabric is rubbed. Second, those loose ends are rolled together by further rubbing until they entangle into a compact ball.

The two stages are separable, and that matters, because a fabric can be prone to the first and resistant to the second or the other way around. Understanding which stage a particular garment is failing at explains a great deal about what to do with it.

Stage one is about how the yarn is spun

Short fibres migrate out of a yarn far more readily than long ones, because a short fibre has fewer points of contact holding it and less length gripped by the twist. This is why staple length is one of the most important and least advertised facts about a cloth, and why long-staple cotton and long-fibre wools command a premium.

Twist works the same way. A tightly twisted yarn grips its fibres and holds the ends in; a soft, low-twist yarn feels wonderful in the hand precisely because the fibres are loosely held, and those same loosely held fibres migrate to the surface quickly.

Fabric structure completes the picture. A loose knit with plenty of room for yarns to move rubs against itself more than a dense weave does. This is the honest reason a very soft, lofty, fine-fibre jumper pills more than a hard-wearing one: the qualities that make it feel the way it does are the same qualities that let fibre ends escape.

Stage two is about fibre strength

Once a ball has formed, whether it stays depends on the strength of the few fibres anchoring it. Wool fibres are relatively weak in this specific sense and break under continued rubbing, so wool pills shed themselves in normal wear and a wool garment often goes through a pilling phase and then settles down.

Synthetic fibres, polyester and nylon in particular, are strong and do not break. The anchoring fibres hold, the ball stays, and it goes on collecting more fibre. This is why a small proportion of synthetic in a blend can make a fabric pill worse than either fibre would alone, and why cheap fleece develops a permanently matted surface.

It also explains why removing pills from a synthetic garment is a maintenance task rather than a one-off. The fabric will keep making them for as long as it is worn, because nothing in the mechanism stops.

Where pilling appears is not random

Look at where the pills are and you can read the wear. Under the arms and along the sides is fabric rubbing against fabric with every step. Across the seat and the back of the thighs is contact with a chair. On one shoulder or across one hip is a bag strap. On cuffs it is desks and doorways.

That is worth knowing, because it means the problem is friction in a specific place rather than a flaw distributed through the garment. Changing which shoulder a bag sits on, or seat covers on a rough chair, genuinely changes the outcome.

It also means a garment can be pilled in a few small areas and structurally perfect everywhere else, which is a different situation from one that is worn out. It usually deserves a different response.

Removing them without doing harm

A battery fabric shaver cuts pills off just above the fabric surface and is the least damaging method for knitwear, provided the fabric is laid flat and not stretched over a curve where the blade can catch. A sweater comb or a pumice-type stone works too and gives more control on delicate items, at the cost of time.

Every method removes some fibre, so it is not free — but it removes the fibre that had already left the yarn, so the loss is smaller than it looks. Cutting pills off individually with small scissors is tedious and works well for a handful of large ones.

Prevention is mostly a matter of reducing friction. Wash inside out, on a short gentle cycle, in a mesh bag; skip the dryer, which is a machine for tumbling fabric against fabric; and give a knitted garment a day of rest between wearings so the fibres are not being worked continuously. None of that stops pilling. All of it slows it down, and on a garment you intend to keep for years, slowing it down is the whole game.