The short answer
Cold water, a detergent made for wool, no agitation and no wringing. Dry it flat, not on a hanger.
- Use the wool cycle or hand wash, at 30C or below.
- Use a wool-specific detergent. Ordinary detergent is alkaline and contains enzymes that digest protein, and wool is a protein.
- Do not wring it. Press the water out, or roll it in a towel and press.
- Dry flat, reshaped by hand. A wet jumper on a hanger stretches under its own weight and never recovers.
What will ruin it
Shrinkage in wool is felting, and it is not reversible. The scales on the fibre interlock under heat and agitation and they do not come apart again. There is no repair, only prevention.
Why it works
A wool fibre is covered in microscopic overlapping scales. Warmth and movement make them ratchet together, which is exactly how felt is manufactured on purpose.
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