Why wool felts

Wool fibres are covered in microscopic scales. When wool is exposed to a combination of heat, moisture and mechanical agitation, those scales lock together and the fabric shrinks and matts — a process called felting. It is largely irreversible, which is why a wool jumper accidentally run through a hot cotton programme can come out several sizes smaller.

Skeins of brightly dyed wool
Dyed wool. The scaled surface of the fibre is what makes wool prone to felting.

Reducing the risk

  • Use the dedicated wool or hand-wash programme, which keeps temperature low and the drum movement slow.
  • Choose a mild detergent formulated for wool rather than a standard heavy-duty powder.
  • Avoid sudden temperature changes between washing and rinsing.
  • Do not wring or tumble dry; press water out gently and dry flat.

Hand-washing silk

Silk is a fine, smooth protein fibre with a natural lustre. It is comparatively weak when wet and sensitive to high heat, so many silk items carry a hand-wash or professional-cleaning symbol.

  1. Use lukewarm water and a small amount of mild detergent suited to delicates.
  2. Move the item gently through the water rather than rubbing or scrubbing.
  3. Rinse thoroughly in clean lukewarm water.
  4. Roll the item in a towel to absorb moisture, then dry away from direct heat and strong sunlight.

Ironing note: Silk is usually pressed on a low setting, ideally while slightly damp and with the iron on the reverse side or through a cloth to protect the surface sheen.

Storage between seasons

Both fibres are vulnerable to clothes moths, whose larvae feed on protein fibres. Clean items before storing them, since residues attract pests, and keep them in a dry, ventilated place. Folding knitwear rather than hanging it prevents stretching at the shoulders.

The general properties of these fibres are described in the public references on wool and silk. For sturdier everyday fabrics, see the guide on cotton and linen care, and for longer-term protection read storing household textiles.