How to tell if yarn is wool or acrylic

Without a label, wool and acrylic can look identical on the shelf. They behave very differently on the needles and in the wash, so it's worth knowing before you commit a skein to a sweater. Three tests, from gentlest to most decisive.

1. The feel test (one minute)

Rub a strand between your fingers, then hold it against your inner wrist.

• Wool feels warm almost at once, slightly dry, and has a little grab — strands catch on each other.
• Acrylic feels cool and smooth, sometimes faintly slippery or squeaky, and strands slide past each other.
• Squeeze a handful and let go. Wool springs back slowly. Acrylic springs back fast and can look shiny where it was crushed.

Reliable for pure fibres. Blends are ambiguous — go to test 3.

2. The water test (five minutes)

Wet a short length and squeeze it out.

• Wool soaks up water readily, darkens noticeably, and smells faintly of wet sheep.
• Acrylic barely absorbs, dries fast, and smells of nothing.

A wool strand stretched wet and left to dry will hold the new shape — that's why wool blocks. Acrylic snaps back and won't.

3. The burn test (definitive — do it over a sink or outdoors)

Snip a two-inch length, hold it in tweezers over a ceramic plate, and touch a flame to the end.

• Wool burns slowly, goes out by itself when you take the flame away, smells like burning hair, and leaves a soft crumbly ash you can crush to powder.
• Acrylic melts before it burns, shrinks away from the flame, drips, smells sharp and chemical, and leaves a hard black bead you can't crush.
• A blend gives you both: some crumbly ash and a hard bead, and a mixed smell. Roughly, the more bead, the more acrylic.

Tweezers, a plate, nothing synthetic near your hands. Never test the whole skein.

What about cotton, or "superwash"?

Cotton burns fast, smells like burning paper, and leaves a fine grey ash. It absorbs water even more readily than wool and feels cool without being slippery.

Superwash wool is still wool and passes all three tests as wool — it has been treated so it won't felt. The label is the only reliable way to know if wool is superwash. The workaround: rub a wet snippet with soap for a minute. Untreated wool starts to mat; superwash doesn't.

Why it matters

Acrylic won't block. Untreated wool felts in a hot wash. Superwash wool grows when wet. If you're substituting yarn in a pattern, the fibre changes the result as much as the weight does.

Next: What weight is my yarn? →

Still have the ball band? Save the yarn to your stash with the Yarn Finder. Working from a mystery bag? Start with How to identify yarn without a label.