On a recent visit to Peru, I went to a street market and bought a sweater billed as being made of alpaca wool. Whenever I take it off, it crackles with static electricity. I had thought that this could not happen with a natural fibre like wool, but would need an insulating material like a synthetic fibre. I am not so naive as to believe that the sweater is pure alpaca, but what proportion of synthetic fibre would it need to produce the crackles I experience?
• None. Even the purest alpaca, like any other wool or fur, will accumulate electric charge that causes sparking if it is dry enough. Almost all natural fibres will spark if rubbed, although synthetic fibres generally do so more readily. You may observe this inadvertently if you stroke a cat when the humidity is low. The build-up of static can produce sparks that sting its ears or nose and leave you with a scratch or a bite.
Antony David
London, UK
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• Static becomes a problem when there is a lack of moisture in the air. On a damp day, even polyester won’t crackle. In drier conditions, the water-absorbing properties of fibres come into play, and polyester will suffer more than, say, cotton.
Overall, animal hair readily absorbs water. However, the scales on each hair’s surface are non-absorbent and form a mostly waterproof layer. We enjoy this property: on a drizzly day, a wool sweater still feels dry, even as moisture accumulates.
Martin Bide
Department of textiles, fashion merchandising and design, University of Rhode Island, US
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