Why Does Yarn Pill? What Causes Pilling and How to Manage It

One of the most common requests I hear in the shop is:

“I want a really soft yarn, but I don’t want it to pill.”

The tricky part is that those two things do not always live happily together.

Some of the softest, most luxurious yarns are also more likely to pill. That does not automatically mean the yarn is poor quality. In fact, beautiful fibres such as fine merino, alpaca and cashmere often require more care than firmer, more rustic wool.

I think we need to calm down a little about pilling.

For many knitted garments, pilling is simply part of being worn. You remove the pills, give the garment a little care, and carry on wearing it. I consider depilling part of normal sweater care, especially because I expect my own handknitted sweaters to be workhorses. I wear them often, I garden in some of them, and I am not tiptoeing through life trying to keep my sleeves away from everything.

Here is what actually causes pilling, how much is normal and what you can do about it.

What is pilling?

Pills are the little balls of tangled fibre that appear on the surface of knitted fabric.

As a garment is worn, small fibres begin to work their way out of the yarn. Friction causes these loose fibres to tangle together, forming the bobbles we call pills.

You will usually see them first in places where there is plenty of rubbing:

• Under the arms

• Along the sides of a sweater

• Under the sleeves

• Around cuffs

• Beneath a handbag strap

• Anywhere the garment rubs against a coat, seatbelt or another layer

The amount of pilling depends on the fibre, the way the yarn was spun, the fabric you create and how you wear the finished item.

Does pilling mean the yarn is poor quality?

No. Pilling alone is not a reliable test of yarn quality.

A cheap yarn can pill. An expensive yarn can pill. Natural and synthetic fibres can both pill.

Some very high-quality yarns pill because they are made from beautifully fine, soft fibres. Those fibres bend easily and can gradually work their way out of the yarn as the fabric is worn.

A yarn may be wonderful for a soft scarf or special cardigan but less suited to a hard-working sweater worn under a coat every day. That does not make it a bad yarn. It means we need to match the yarn to the project and to the way we plan to use it.

Why do soft yarns often pill more?

Softness can come from several different qualities.

The fibre may be very fine, which means it bends easily and feels gentle against the skin. The yarn may also include shorter fibres, creating more fibre ends that can eventually work free. It may be lightly spun or deliberately brushed to create a soft halo.

All these qualities can create a gorgeous yarn. They can also make it more vulnerable to friction.

This is why fibres such as fine merino, alpaca and cashmere can pill even when they are excellent quality.

Brushed yarns are another good example. Their fluffy surface is part of their appeal. We cannot ask for a cloud-like halo while also expecting every fibre to remain firmly tucked inside the yarn forever.

What causes yarn to pill?

There is rarely one cause. Several factors usually work together.

1. Fibre length

The individual fibres used to make yarn are known as staples.

Longer fibres are generally more securely held within the yarn because there is more length available to twist into place. Shorter fibres create more loose ends that can gradually move towards the surface.

However, fibre length is only one part of the story. A yarn made from longer fibres can still pill if it is loosely spun, knitted very openly or exposed to constant friction.

2. Fibre fineness

Very fine fibres usually feel softer because they bend more easily against the skin.

That flexibility can also make it easier for them to move within the yarn and work towards the surface. This helps explain why an incredibly soft merino can sometimes require more maintenance than a firmer wool.

3. How the yarn is spun

Worsted-spun and woollen-spun describe methods of preparing and spinning fibre. They do not describe the thickness of the yarn.

In worsted spinning, longer fibres are generally combed and aligned in the same direction. Many of the shorter fibres are removed. This produces a smoother, denser yarn with fewer loose ends on the surface.

Woollen-spun yarns are made from carded fibres that are less closely aligned. Air is trapped within the yarn, producing a lighter, loftier and warmer result. That loft can create more opportunities for fibres to move, although it does not mean every woollen-spun yarn will pill badly.

Outlaw Yarn Rebel Worsted is a good example of why we should avoid making absolute rules. Despite its name, “worsted” refers to its yarn weight. It is actually woollen-spun, but I have found it to be a durable yarn that copes well with regular wear.

4. Twist and plies

A smooth, firmly twisted, multi-ply yarn will usually hold its fibres more securely than a softly spun single-ply yarn.

The direction of the twist may be described as S or Z twist. The letter only tells us the direction in which the yarn was twisted. It does not tell us how firm the twist is or guarantee how well the yarn will wear.

Lana Grossa Cool Wool and Cool Wool Big are both very soft merino yarns, but their smooth, tightly constructed plies give them excellent stitch definition and help make them practical choices for everyday garments.

5. Gauge

Gauge affects how much room the yarn has to move within the fabric.

All other things being equal, a garment knitted at a firmer gauge will generally pill less than the same yarn knitted into a very loose, open fabric. The closer structure gives the individual strands less room to move and rub against each other.

That does not mean you should ignore your pattern and use tiny needles. It simply means that an airy, loosely knitted garment may need more maintenance than a denser one.

Your swatch helps you judge the finished fabric before committing to an entire sweater.

6. Stitch pattern

Pilling is often more noticeable on stocking stitch, also called stockinette stitch, because it creates a smooth, flat surface.

Stocking stitch can also allow more movement than a dense knit-and-purl texture. Rib, moss stitch and some textured patterns create a more compact fabric that can help hold the yarn in place.

This does not make textured knitting pill-proof. It is another factor that can influence the result.

7. Friction

Friction is the big one.

A sweater worn occasionally over a soft shirt has a very different life from one worn gardening, driving, carrying bags and sitting beneath a heavy coat.

I expect my sweaters to work hard. Unsurprisingly, I see the most pilling under the sleeves and where my arms rub against the body.

How you use a garment matters just as much as what it is made from.

Do acrylic and other synthetic fibres prevent pilling?

Adding acrylic does not guarantee that a yarn will not pill.

Synthetic fibres are often strong. In a blended yarn, a weaker fibre can work loose and form a pill while the stronger synthetic fibre keeps that pill firmly attached to the garment.

Natural wool pills can eventually loosen and fall away. Pills held by strong synthetic fibres can sometimes remain attached for longer.

Blends can still be durable and useful, but the presence of acrylic should not be treated as a promise of a pill-free garment.

Is pilling during knitting normal?

A small amount of fluff or halo can be completely normal, particularly with brushed or softly spun yarns.

Significant pills forming before you have finished knitting make me pause. Even yarns that have pilled heavily during wear have not normally formed proper pills while I was knitting them.

If this is happening, check how much friction the yarn is experiencing. It may be rubbing repeatedly through a very tight grip, against a rough yarn bowl, inside a project bag or through a section that has been unravelled and reknitted several times.

The construction of the yarn may also be a factor, so ask your local yarn shop if you are unsure.

Does pilling eventually settle down?

With many natural wool yarns, the heaviest pilling happens during the first season of wear.

The shorter or looser fibres gradually work their way out. Once these have been removed, the garment often settles and needs less frequent attention.

You may depill a heavily worn sweater a couple of times during its first winter and only once a season after that.

Some garments will always need occasional maintenance, particularly if they contain very fine fibres or experience regular friction. That is not necessarily a problem. It is part of owning and wearing knitted clothing.

How to remove pills safely

I use a Gleener fabric shaver for my own knitted garments. We stock two options, and both are designed to remove pills manually without needing electricity.

Place your garment on a clean, flat surface and work gently. Do not push hard or keep scraping the same area once the pills have been removed.

Electric fabric shavers can also work well, although I personally find the Gleener easier to control.

I avoid cutting pills off with scissors whenever possible. It is very easy to catch a stitch or cut into the garment. I might carefully snip off one unusually large pill, but I would not use scissors to depill a whole sweater.

I also avoid pulling pills off with my fingers. Pulling can draw more fibre out of the yarn and encourage another pill to form.

How I care for my woollen sweaters

I do not routinely wash my woollen sweaters.

Wool does not need to be washed after every wear. I rotate my sweaters, air them in a well-ventilated place and spot-clean small marks when necessary.

If one of my gardening sweaters gets a little dusty, I gently brush away the dry dirt with a soft brush. I am careful not to scrub or rough up the surface.

When a sweater genuinely needs washing, I:

1. Depill it before washing.

2. Soak it in lukewarm water with a small amount of wool wash for about 30 minutes.

3. Gently squeeze out the water without wringing or twisting.

4. Roll it in a towel to remove excess moisture.

5. Reshape it and lay it flat to dry.

Always check the care instructions for your particular yarn. Wool, alpaca, cotton and blended yarns do not necessarily need the same treatment.

It is also sensible to clean worn woollen garments before putting them into long-term storage, as body oils and food marks can attract moths.

How to choose yarn that is less likely to pill

No yarn comes with a complete no-pilling guarantee, but you can improve your odds.

Look for:

• A smooth, compact yarn surface

• Firm twist

• Several plies twisted securely together

• Longer-staple fibres

• Good stitch definition

• A yarn suited to the amount of wear the project will receive

Consider the finished project too.

A delicate, softly spun yarn may be wonderful for a shawl or occasional cardigan. A sweater you plan to wear several times a week may be better in a firmer, more structured yarn.

For soft yarns with practical construction, Lana Grossa Cool Wool 5 Ply and Lana Grossa Cool Wool Big are good examples.

For a lofty New Zealand-made yarn that I have found stands up well to regular wear, Outlaw Yarn Rebel Worsted is another excellent option.

If your priority is absolute softness, you may need to accept a little more maintenance. If your priority is a hard-working garment, tell us how you plan to wear it and we can help you choose accordingly.

Pilling is part of wearing knitwear

Handknitted clothes are made to be worn.

A pill under the arm does not erase the hours you spent knitting. It does not automatically mean you chose badly, cared for the garment incorrectly or bought poor-quality yarn.

Sometimes it simply means your sweater has been doing its job.

Remove the pills, air the garment, give it a rest between wears and put it back on. That small amount of maintenance is often the trade-off for wearing something soft, warm and made from beautiful natural fibres.

If you are unsure which yarn will suit your project, come and talk to us at The Wool Shop in Rangiora or contact us online. Tell us what you are making and how you expect to use it. We will help you find the right balance between softness, durability and the amount of care you are happy to give it.