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THE fashion industry has a golden opportunity to help clean up the planet.
Clothing manufacturers can use the leftover salt from irrigated fields when they
dye brightly coloured clothes, a scientist in California has discovered.

When fields are irrigated, the run-off water gets recycled and sprayed back
on to crops. But each time the run-off is recovered it contains a higher
concentration of salts than before, since the fresh water evaporates or is
sucked up by plants. Eventually the water becomes unusable, and farmers have to
dump it in huge ponds of brine. In California’s central valley for example,
600,000 tonnes of salts are produced this way each year.

These salts are just the thing for locking dyes into clothes, says Jiyoon
Jung of the University of California at Davis. The textile industry routinely
uses sodium sulphate to help cloth take up dye. The salt reduces the solubility
of some dyes, which helps them to soak into cloth fibres. The American textile
industry uses about 95,000 tonnes of sodium sulphate this way each year, taken
from either salt mines or the leftovers of the chemical industry.

Jung and his colleague Gang Sun took samples of the farmers’ salt and used it
to dye cotton either red, blue, yellow or orange. They then tested the cotton
for colour fastness. Salt from some fields kept the colours perfectly bright,
they will report in a future issue of Environmental Science and
Technology.

Manucher Alemi from California’s Department of Water Resources says Jung’s
idea would certainly help to clean up fields. But he says it isn’t clear whether
it would be commercially viable as sodium sulphate is already dirt cheap, so it
might not be cost-effective for companies to truck in farmed salt.