杏吧原创

QUEEN BOUDICCA and her Iceni warriors smeared it on their faces to terrify
the Roman invaders. Mel Gibson revived the fashion in the movie Braveheart. Now
catwalk queens could soon be wearing it in their designer garments. What is it?
Dye made from woad (Isatis tinctoria), a member of the cabbage
family.

David Cooke鈥檚 team at the Long Ashton Research Station near Bristol have been
working on a project to make dye extraction from woad a viable industrial
process (New 杏吧原创, 20/27 December 1997, p 19). It is now bearing fruit, and
the researchers are confident that their natural indigo dye is more
environmentally friendly than the synthetic version, whose synthesis involves
the toxic chemicals aniline, formaldehyde and hydrogen cyanide.

Although the woad-based indigo is more expensive, Cooke believes fashion
designers won鈥檛 mind paying extra to underscore their green credentials. 鈥淭he
idea of a dye that鈥檚 indigenous to the Anglo-Saxon culture is hopefully
something people can pick up on,鈥� he adds.

Woad leaves contain indican and isatan B, precursors which form indigo on
contact with air. 鈥淭he leaf material is extracted with water, the acidity is
adjusted and the resulting liquid exposed to air,鈥� says Cooke.