What Is Pilling and What Causes It? A Manufacturer’s Guide to Testing and Prevention

Pilling is the single most common quality complaint in knitwear, and it’s also one of the most misunderstood — both by customers who assume it means a garment is cheaply made, and by brands who don’t realize pilling resistance is something a manufacturer can actually test and control before a yarn ever reaches bulk production. As a knitwear manufacturer that builds pilling testing directly into yarn sourcing, MySweaterFactory (MSF) breaks down what pilling actually is, why it happens, and how a responsible sourcing process controls it before it becomes a customer complaint.

Why Pilling Is a Sourcing Question, Not Just a Customer Complaint

Brands often treat pilling as an inevitable customer-service issue to manage after the fact — a returns policy, a care-label disclaimer, a customer service script. That’s backward. Pilling resistance is a measurable, testable property of a specific yarn and construction, which means it’s a decision a brand and its manufacturer make together well before bulk production, not a surprise discovered after a collection has already shipped.

Treating pilling this way changes the entire conversation with a manufacturer — instead of asking “why did this pill,” a brand can ask “what pilling rating did we test this yarn to, and is that rating appropriate for how this garment will actually be worn.” That’s a fundamentally more productive question, and one only possible if testing happened before, not after, bulk production.

What Pilling Actually Is

Pilling, sometimes called bobbling, is the formation of small balls of fiber on a garment’s surface. These form when loose fibers work their way to the surface of the fabric and become tangled together through friction during normal wear.

Does Pilling Mean Poor Quality?

Not automatically — this is one of the most persistent misconceptions in knitwear, and it’s worth correcting directly in customer-facing communication rather than letting customers assume the worst. Pilling depends on a genuine combination of factors: fiber type, staple length (how long the individual fibers are), how the yarn was spun, and how and where the finished garment is actually worn.

Even luxury cashmere and premium Merino wool can pill, particularly when a garment is new — in fact, some of the softest, most luxurious fibers are actually more prone to early-wear pilling than coarser, more tightly spun alternatives. This is exactly why a brand shouldn’t treat pilling on a premium product as evidence of a sourcing mistake without first checking the specific test data behind that yarn.

This distinction is worth building directly into customer-facing care materials, too. A brand that proactively explains why even premium fibers can pill — rather than staying silent and hoping the topic never comes up — tends to face fewer complaints framed as quality failures, since customers who understand the mechanism in advance are far less likely to read early pilling as a defect.

Why Knitwear Pills: The Friction Mechanism

Pilling is a direct result of everyday friction. A knit garment rubs against a handbag strap, a desk edge, a seatbelt, or simply the wearer’s own arm movement, and every instance of that friction has the potential to work loose fibers to the surface. This is exactly why pilling shows up first, and most visibly, in specific high-friction zones — under the arms, along the sides of the body, and at the cuffs — rather than appearing evenly across an entire garment.

Understanding this mechanism matters for design decisions too. A garment intended for frequent use with a bag or backpack, for instance, might benefit from a slightly more pill-resistant yarn blend specifically at the shoulder and side panels, even if the rest of the garment uses a softer, more premium fiber.

Industry-Standard Pilling Testing: The Grading Scale

Responsible yarn sourcing relies on independent, standardized pilling resistance testing rather than a subjective hand-feel assessment. The most widely used approach grades a fabric sample on a scale from 1 to 5 after controlled abrasion testing.

A responsible sourcing process sets a minimum acceptable rating before committing to a yarn for production — commonly a 3 to 4 rating threshold for everyday knitwear — rather than discovering a yarn’s real-world pilling behavior only after a collection has already reached customers.

What to Test Before Committing to a Yarn

Independent Laboratory Testing

Every candidate yarn should be tested by an independent third-party laboratory before a factory commits to producing it at scale, rather than relying solely on a supplier’s own claims about a yarn’s durability.

Yarn Construction and Supplier Track Record

Beyond a single lab test, favoring yarn constructions and suppliers with a proven track record across multiple seasons reduces the risk of an isolated bad batch slipping through testing. Semi-worsted spinning techniques, for example, are known within the industry to generally wear better over time than more loosely spun alternatives, which is worth factoring into yarn selection even before lab results come back.

Balancing Softness Against Durability

Because the softest fibers are often more prone to early pilling, brands need to make a deliberate, informed trade-off between hand-feel and pilling resistance for each specific product — a decision best made with real test data in hand rather than assumed based on a fiber’s general reputation.

Care Instructions That Protect Against Premature Pilling

Even a well-tested, pill-resistant yarn can pill prematurely if a garment is cared for incorrectly — which means care labeling is genuinely part of a brand’s quality control strategy, not just a legal formality.

Washing and Drying

Gentle hand washing in lukewarm water with a mild wool wash, rather than harsh detergents, protects natural fibers significantly. Natural fibers like wool also don’t need washing after every single wear — airing a garment overnight is often enough to freshen it, and washing less frequently directly reduces the friction and agitation that accelerates pilling.

Drying and Storage

Wet knitwear should never be hung, since the weight of retained water can stretch a garment out of shape — laying flat to dry after gently squeezing out excess water protects both fit and fiber integrity. Folding rather than hanging in storage similarly prevents shoulder stretching over time.

Recommending an Aftercare Tool

Brands can add genuine value to the customer experience by recommending a quality electric fabric shaver as part of garment care guidance — a simple tool that gently removes surface pills without damaging the underlying knit, and one of the most effective ways to extend a garment’s visible lifespan between wears.

Building Pilling Resistance Into Your Sourcing Process

A little pilling on a well-loved, frequently worn sweater doesn’t mean a garment has failed — but a brand’s sourcing process should still be built to minimize it as much as reasonably possible, since customer-perceived quality depends heavily on how a garment looks after repeated wear, not just how it looks new.

At MSF, we build independent pilling resistance testing directly into our yarn sourcing process, setting a clear minimum rating threshold before any yarn is approved for bulk production. If you’re developing a collection and want a sourcing partner that treats pilling resistance as a testable specification rather than a hope, our team can walk through yarn testing and selection for a men’s knitwear or women’s collection program. Learn more about our quality control process on the About Us page, or get in touch to discuss your next collection.

References

• Wikipedia — Pilling (Textile)