Wool shrinks for a specific, mechanical reason, and once you know what it is the rules stop being arbitrary.
Each wool fibre is covered in microscopic overlapping scales, like roof tiles. Heat and moisture make those scales lift. Agitation then causes the lifted scales to interlock with neighbouring fibres, and they cannot slide back. The fabric contracts, permanently. This is felting, and it is not reversible.
Three ingredients are required: heat, moisture, and agitation. Remove any one and wool is safe. That is the whole method.
Hand washing
- Fill a basin with cool water — 20 to 30 °C, comfortable rather than warm. Consistent temperature matters more than the exact figure; a sudden change from warm to cold shocks the fibre.
- Add a wool-specific detergent. Ordinary detergent is alkaline and strips the natural lanolin. Enzyme detergents are worse — enzymes digest protein, and wool is protein.
- Submerge and leave for 10 minutes. Do not stir, wring, or rub. Press it gently under the water a few times, no more.
- Rinse in water of the same temperature until it runs clear. Same temperature is the point people miss.
- Press the water out against the side of the basin. Never wring — that is concentrated agitation.
- Roll in a towel and press to absorb more water.
- Dry flat, in shape, out of direct sun and away from radiators. A wet wool jumper on a hanger stretches under its own weight and does not recover.
Machine washing
A machine wool cycle is genuinely safe on most modern machines, because it is designed around the same principle: it barely agitates. It rocks rather than tumbles, and it spins slowly.
- Use the wool or hand-wash programme, nothing else
- 30 °C maximum, or cooler
- Spin at 400–600 rpm maximum
- Wool detergent only
- Put the garment in a mesh laundry bag to reduce friction against the drum
- Wash wool with wool — a load with jeans in it defeats the point
Check the care label first. A garment marked hand-wash-only with two bars is telling you its construction, not just its fibre, and some knits genuinely will not survive a machine.
Superwash and machine-washable wool
Superwash wool has had the scales chemically removed or coated in polymer, so it cannot felt. It genuinely tolerates machine washing and sometimes tumble drying.
It is not identical to untreated wool: it is slightly less insulating, it can grow rather than shrink when wet, and it takes longer to dry. Still dry it flat.
Drying
Never tumble dry untreated wool. Heat plus tumbling is exactly the combination that felts it, and a jumper that goes into a dryer usually comes out several sizes smaller and permanently dense.
Flat drying, on a mesh rack if you have one so air circulates underneath, reshaped gently to its original dimensions while damp. Wool takes 24 hours or more to dry properly and it should be left alone for all of it.
How often to wash wool at all
Less than you think. Wool is naturally antimicrobial and odour-resistant, and every wash carries risk.
- Air it between wears. Hang it somewhere ventilated overnight and most odour disappears on its own
- Spot clean marks rather than washing the whole garment
- Wash a jumper after five to ten wears, or when it is actually dirty
- Steam — a garment steamer, or hanging it in a bathroom during a shower — refreshes wool and relaxes creases without water contact
Pilling
Pills are short fibres that have worked loose and tangled. They are a sign of friction, not of poor quality — although shorter-staple wool pills more readily.
Remove them with a fabric shaver or a wool comb, working in one direction with the garment laid flat. Do not pull them off by hand; that drags out the fibre and thins the fabric. Pilling reduces markedly after the first few washes as the loose fibres are exhausted.
If it has already shrunk
Felting is not reversible, but mild shrinkage sometimes has some stretch in it:
- Soak in cool water with a generous amount of hair conditioner for 30 minutes. The conditioner lubricates the fibres.
- Press the water out without rinsing thoroughly.
- Lay flat and gently stretch back toward the original shape, working from the centre outward. Pin it in shape on a towel if necessary.
- Let it dry fully in that position.
This recovers a proportion of mild shrinkage. It does nothing for a jumper that has been through a hot cycle and come out felted solid.
Storage
- Fold, never hang. Hangers stretch shoulders permanently
- Wash before storing. Moths are attracted to body oils and food residue, not to clean wool
- Breathable storage — cotton bags or boxes. Sealed plastic traps moisture and causes mildew
- Cedar or lavender rather than mothballs, which leave an odour that is difficult to remove