Can you name the colours of the rainbow? Three centuries ago, all-round genius Sir Isaac Newton name checked seven: red, orange, yellow, green, blue, indigo and violet. However, many modern observers have reduced this number to six, believing indigo, our chosen subject and the only tertiary shade in the line-up, should never have been included in the first place. This is because, to the human eye at least, indigo is almost indistinguishable from blue or violet. Search contemporary pop culture – the Gay Pride flag or the cover of Pink Floyd’s Dark Side of the Moon album, for example – and you will likely find it deleted.
Indigo plant - photograph by @rachyrairai
Despite its questionable rainbow qualifications, there’s no denying indigo’s universal appeal. A natural hue, it can be extracted from the leaves of several varieties of plant, but most commonly comes from the genus Indigofera, which is native to the hot and humid tropics. Used in textile dyeing since the third millennium BC, possibly earlier, India was the first major centre for the production and processing of indigo dye in the Old World. From there, it made its way to Ancient Greece and Rome where it was considered a luxury product and used for cosmetics, paints and medicine.
Despite its allure, the lengthy and dangerous nature of land trade routes meant that indigo remained a rare commodity in Europe throughout the Middle Ages, when a similarly blue-hued dye derived from the woad plant (Isatis tinctoria) was used instead. It wasn’t until the late 15th century, when Portuguese explorer Vasco da Gama discovered a sea route to India that the importation and use of indigo rose on the continent significantly. High value, easy to transport and long lasting, it was the perfect trading commodity and often referred to as ‘Blue Gold’.
By the 19th century, natural indigo production was unable to keep pace with the demands of an industrialised textile industry, sparking the quest for a synthetic alternative. After decades of research, German chemist Adolf von Baeyer finally achieved this goal in 1897. Much cheaper to produce, these synthetics continue to dominate today, although natural indigo is happily undergoing something of a revival as artisans rediscover its extensive history, versatility and sustainability.
Words by Rachel Ward
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