How to wash a wool jumper without shrinking: 5 rules

A cosy wool jumper is winter essential number one – until the day it comes out of the washing machine two sizes smaller and as stiff as cardboard. Wool is sensitive to heat, friction and sudden temperature changes. If you know how to wash a wool jumper correctly, though, it will stay soft and keep its shape for years.

Here are five rules for merino, lambswool, cashmere and classic knitwear – whether you call it a jumper, sweater or pullover.

Why wool shrinks

Wool fibres are covered in tiny scales. Warm water, friction and sudden changes between warm and cold make these scales open up and hook into each other. The fibres mat together – this is called felting – and the knit becomes smaller, thicker and stiffer. Once felted, wool can't really be restored.

That's why the three enemies of wool are heat, agitation and temperature shocks.

1. Wash less – air more

Wool has natural properties that repel dirt and odours. In many cases, a jumper doesn't need washing after every wear.

• Air it: Hang the jumper outdoors or near an open window for a few hours, ideally on a cool, dry day.
• Brush it: Remove lint and dust with a soft clothes brush.
• Spot clean: Dab small stains with lukewarm water and a little wool detergent.
• Wash when needed: When it smells even after airing, or has visible stains.

Airing instead of washing also saves water and energy.

2. Wash a wool jumper in the machine – correctly

Most modern washing machines have a wool programme that moves the drum very gently. Check the care label first: if it shows a hand-wash symbol or allows machine washing, you're usually fine with the wool cycle.

1. Turn the jumper inside out.
2. Put it in a laundry bag, especially fine knits and cashmere.
3. Choose the wool or hand-wash programme, cold or up to 30 °C – never higher than the label.
4. Use a wool detergent without enzymes and without bleach.
5. Set a low spin speed, or the one preset by the wool programme.
6. Wash with only a few similar items – don't fill the drum.

EnergieSchweiz notes that low temperatures are enough for most laundry and that there's no need to increase the detergent dose – perfect for wool.

3. Hand wash: gentle and simple

For delicate knits, hand-knitted items and cashmere, hand washing is the safest.

1. Fill a basin with cool to lukewarm water – roughly the temperature of your hand.
2. Dissolve a small amount of wool detergent.
3. Submerge the jumper and gently press it under the water several times. Don't rub or wring.
4. Leave for about 10 minutes.
5. Drain and rinse with water of the same temperature – temperature changes cause felting.
6. Press the water out gently with flat hands against the basin.

4. Dry flat and in shape

Drying is where many jumpers get ruined.

1. Lay the jumper on a large towel and roll the towel up to absorb water. Press lightly – don't twist.
2. Unroll and lay the jumper on a dry towel or a drying rack for knitwear.
3. Gently pull it back into its original shape: sleeves, cuffs, hem.
4. Dry flat at room temperature, away from radiators and direct sunlight.
5. Turn it over after a few hours for even drying.

Never hang a wet wool jumper on a hanger or clothes line – the weight of the water stretches it out of shape.

5. Remove bobbles and store properly

Bobbles (pilling) form where fibres rub, such as under the arms and on the sides.

• Fabric shaver: Removes bobbles quickly – hold the knit taut and don't press.
• Wool comb or pumice stone for knitwear: Gentle alternative for delicate knits.
• Avoid: Scissors and razors, which can cut the yarn.

For storage:

Clothes moths love wool, especially when it's worn and stored unwashed. The City of Zurich's fact sheet on clothes moths explains how their larvae damage woollen textiles – our guide on getting rid of clothes moths covers what to do.

Common mistakes with wool

• Normal programme at 40 °C: The classic cause of shrinking.
• Standard detergent with enzymes: Damages wool fibres over time.
• Wringing out: Stretches and felts the knit.
• Tumble drying: Heat plus movement equals felting.
• Drying on a hanger: The jumper loses its shape.
• Fabric softener: Unnecessary for wool and can leave residue.

For other textiles, see our guide on bed linen washing temperatures.

Priority Clean editorial teamOur cleaning team from Alberswil, Canton of Lucerne, shares hands-on experience from move-out, house, office and window cleaning across Central and Northwestern Switzerland.