As the taste for organic food increases ever faster, organic blue jeans could be the next item on green shoppers鈥� lists. Organic cotton is already being grown, but the new development comes thanks to a research group鈥檚 efforts to make indigo dye the medieval way.
Philip John, from the UK鈥檚 University of Reading, is co-ordinating a project called 鈥淪pindigo鈥� to recreate an all-natural process for making the dark blue dye, using a plant called woad and special bacteria.
John, with the University of Bristol, international partners, and 拢2.3 million in funding from the European Union, hopes to have organic jeans on the market by 2004. Despite the extra expense, John believes there will be a clothing company out there who might like to carry the new 鈥渆co鈥� label.
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Indigo is currently made from aniline, formaldehyde and hydrogen cyanide, all of which come from drilled oil. The artificial synthesis may not cause significant environmental problems, but Kerry Gilbert from the University of Bristol points out that people are becoming more aware of their long-term impact on the planet. 鈥淚t鈥檚 just a way of evolving the technology to make it from a natural, renewable source,鈥� she says.
Bacteria hunt
In the medieval process that they hope to imitate, the woad plant Isatis tinctoria is crushed up and dried. Bacteria in the air start to break down the plant cells and help to release the molecule which makes the dye.
These compounds are dissolved in water to remove their sugar components, and then allowed to recombine into small blue flakes. At this point the dye is in small insoluble chunks, so something needs to be added to let the dye dissolve and soak into fabric.
Medieval people used a broth of bran, wood ash, and stale urine to do this. But that kicked up quite a stink. 鈥淚t smelled like decaying meat,鈥� says Gilbert.
So the Reading team went looking for the bacteria that was responsible. A few years ago, they found spores of Olostridium isatidis in archaeological samples of the wooden vats that indigo was brewed in. On revival, these bacteria proved to do the trick.
The Bristol group has also been cultivating the indigo plant by traditional breeding, trying to make the ideal variety for growing in England.