Why does wool felt when washed?

Felting occurs when a mass of wool agitated in water is subjected to some pressure. Each fibre moves preferentially in one direction and contributes to
the entanglement and compaction of the entire structure.

Shrinkage occurs during wet processing and is irreversible, meaning that once shrinkage has occurred, it is impossible to restore the garment's original size.

• The surface of wool fibres has many scales, which explains the significant shrinkage of wool garments during washing. When wool fabric is subjected to mechanical action (agitation, spinning) in the presence of moisture, individual wool fibres begin to move.
• Due to the surface scales, the fibres can only move in one direction. During washing and/or drum drying, under the effect of mechanical agitation, friction, and pressure in the presence of moisture and heat, the scaled edge of one fibre locks into the inter-scale space of another fibre, like a ratchet mechanism.
• The fibres interlock and cannot return to their original position, resulting in irreversible shrinkage of the garment.
• Wool fibres can be made shrink-resistant either by removing or coating the scales, or by limiting the movement of the fibres in a fabric by bonding them together.

How to prevent wool from felting?

I recommend handwashing your untreated pure wool garments.

• Soak your garment in lukewarm water with a little wool detergent. Rinse also in lukewarm water.
• Squeeze, but do not wring, to remove water. Lay the garment flat on a towel.
• Roll up the towel to absorb as much water as possible, then dry your garment flat if possible.

Tip: A pure wool garment does not need to be washed very often. Most of the time, a few hours outdoors are enough to eliminate odours. Long live the natural properties of wool :-)