Sweetness fades

Clothes fade. It's a fact of life. This might be a good thing if you like the lived-in look, but generally it's a pain. Harry Anderson and colleagues from Oxford University have now found a simple way to stop colour bleaching out of new clothes.

The key? Sugar-coating.

Anderson specialises in designing 'sheaths' for molecules, made from rings of linked glucose units. He found that threading an azo-dye molecule, which has a rod-like shape, through the ring, he created a dye which could stick to the cellulose in cotton fibres, but was not susceptible to chemical or light-induced bleaching.

The team subjected cloth dyed with the cyclodextrin-azo dye combination, known as a rotaxane, to a variety of harsh treatments. They found that light faded the unprotected dye ten times faster than the rotaxane.

Sodium dithionate bleach faded the dye-only cloth in one hour, but had hardly affected the rotaxane dye after 20 hours.