How to Wash Wool

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The three rules: Cold water. Minimal agitation. Lay flat to dry — never hang.

Wool is the most common fabric to ruin in the wash. Understanding why wool felts makes the rules obvious — and makes it much harder to accidentally destroy a jumper.

Why Wool Felts — and Why It's Permanent

Wool fibre has a scaly surface — like roof tiles overlapping along the shaft. When wool is exposed to heat and agitation simultaneously, these scales interlock and lock together permanently. This is called felting, and it cannot be reversed. The garment shrinks, thickens, and the texture becomes dense and matted. Once felted, it cannot be un-felted.

The two triggers are heat AND agitation together. Cold water alone will not felt wool. Warm water alone causes minimal damage. Combine them and the scales ratchet together irreversibly. This is why wool requires cold water, a gentle cycle or hand washing, and no wringing or rough handling.

How to Hand Wash Wool

1
Fill a basin with cold water
Use cold or lukewarm water — no warmer than 30°C. Do not use hot water under any circumstances.
2
Add wool wash or mild detergent
Use a detergent designed for wool (Woolite, Nikwax Wool Wash, Eucalan) or a very small amount of baby shampoo. Never use standard laundry detergent — it is too alkaline and strips the natural lanolin that keeps wool soft. Never use biological (enzyme) detergent — the protease enzymes digest wool protein.
3
Submerge and gently press
Submerge the garment and gently press it through the water. Do not wring, twist, rub, or agitate. Wool should be moved through water, not worked against itself. Leave to soak for 10 minutes.
4
Rinse in water the same temperature
Temperature shock — sudden change from warm soak to cold rinse — can also trigger felting. Rinse in water as close to the same temperature as your wash water. Gently squeeze out water from the garment without twisting.
5
Press out water — do not wring
Lay the garment flat on a clean dry towel. Roll the towel up around the garment and press firmly — the towel absorbs excess water. Do not wring. Unroll and lift the garment gently.
6
Lay flat to dry
Lay the garment flat on a dry towel or mesh drying rack. Gently reshape it to its original dimensions while still damp. Never hang wool to dry — the wet weight of the garment stretches it out of shape, permanently. Dry away from direct heat and sunlight.

Machine Washing Wool (When It's Safe)

Check the label first

Some wool is labelled 'machine washable' — this means it has been treated (superwash process) to prevent felting. Standard untreated wool should be hand washed or dry cleaned. When in doubt, hand wash.

Use the wool or delicate cycle only

This cycle uses minimal agitation and a slow spin speed. Never use a cotton or synthetic cycle on wool — the agitation speed will felt it.

Cold or 30°C maximum

Even on the wool cycle, use cold or 30°C water. Higher temperatures accelerate felting risk.

Lowest spin speed

High-speed spinning agitates and stresses wool fibres. Use the slowest spin available (400–600 rpm). Some wool cycle programmes automatically set this.

Use a mesh laundry bag

A mesh bag reduces the movement of the garment inside the drum and protects it from snagging on other items.

Lay flat to dry immediately

Take the garment out of the machine immediately after the cycle ends and lay flat to dry. Do not leave it bunched in the drum.

What to Avoid

Hot water

Triggers the scale-interlocking mechanism that causes felting. Even a single hot wash can shrink a wool garment to half its size.

Hanging to dry

Wet wool is heavy and the fibres are relaxed. Hanging causes the garment to stretch — particularly at the shoulders and hem. Once stretched this way, it cannot easily be returned to shape.

The tumble dryer

The combination of heat and agitation inside a dryer is the fastest way to felt wool. Even a few minutes at low heat can cause significant shrinkage. Never tumble dry wool.

Wringing or twisting

Wool fibres are surprisingly fragile when wet. Wringing stresses and breaks the fibres, weakening the fabric. Press water out instead.

Biological (enzyme) detergent

Enzyme detergents contain protease — an enzyme that breaks down proteins. Wool is a protein fibre (keratin). Using bio detergent on wool digests the fibre itself, causing pilling, weakness, and loss of texture.

Rubbing stains

Wool felts under friction — particularly when wet. Blot stains gently instead of rubbing, and let cleaning agents do the work.

By Wool Type

Standard merino wool

Hand wash or gentle wool cycle

Merino is finer than standard wool and slightly more forgiving, but should still be treated with cold water and minimal agitation.

Superwash / machine-washable wool

Wool cycle, 30°C

These fibres have been chemically treated to smooth or remove the scales. Machine washable on the wool cycle. Still lay flat to dry.

Cashmere

Hand wash only

Cashmere is extremely fine and delicate. Hand wash only in cool water with specialist cashmere wash. Lay flat to dry. Avoid the wool cycle.

Lambswool

Hand wash preferred

Very soft but prone to felting. Hand wash. Can use wool cycle on some machines — test on a less visible garment first.

Wool blends (wool + acrylic)

Wool cycle or hand wash

The acrylic content gives some protection against felting. Wool cycle at 30°C is usually safe — check the label.

Chunky or knit wool

Hand wash, reshape carefully

Heavy knit items are most prone to stretching when wet. Lay completely flat on a large towel and reshape while damp.

FAQ

Can you machine wash wool?

Only wool labelled 'machine washable' or 'superwash' can safely go in a machine — use the wool or delicate cycle at 30°C with the slowest spin speed. Standard untreated wool should be hand washed to avoid felting. Cashmere should always be hand washed. When in doubt, hand wash.

Why does wool shrink in the wash?

Wool shrinks because of felting — a process where the microscopic scales on wool fibres interlock and permanently lock together when exposed to heat and agitation. Once felted, the shrinkage cannot be reversed. The combination of hot water and mechanical agitation (spin cycle, rubbing) is the trigger. Cold water alone does not cause felting.

Can you put wool in the dryer?

No. A tumble dryer combines heat and agitation — both triggers for felting — and will shrink most wool garments severely. Always lay wool flat to dry. Even air-only tumble drying can cause some agitation damage. The only exception is machine-washable (superwash) wool, and even then, lay flat drying is recommended to maintain shape.

Can you unshrink wool that has been washed in hot water?

Sometimes — if the felting is not severe. The baby shampoo / hair conditioner method: soak in lukewarm water with a tablespoon of conditioner for 30 minutes. Conditioner relaxes the wool fibres slightly. Then gently stretch the garment to its original shape while wet and lay flat to dry. This works best on mildly shrunk garments; severe felting cannot be reversed.

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