Blue jeans wouldn't be blue without one key ingredient: the indigo dyestuff. But what is Indigo? Well, Indigo is often referred to as a “living colour,” and the fact that indigo dyed jeans fade over time is the single most unique feature that differentiates denim from all other fabrics. But what is the reason for this – why do we continue to make and wear garments that purposely lose color?

The technical reason for indigo dyed denim's ability to fade is fairly simple. Unlike most other dyestuffs, the indigo dye doesn't penetrate to the core of the yarn. When the denim is worn and gets abraded, the indigo color slowly rubs off, and the white core gradually becomes visible. That´s when you´ll suddenly have a pair of wildly different coloured jeans on your hands.

For thousands of years, natural indigo was extracted from plants. The dyestuff is expensive to produce and the dyeing process is difficult to control. In 1897, a synthesized and much less costly version of indigo dyestuff was put into production. But the formula for synthesized indigo wasn't conceived overnight. Its origins trace back to 1865 when the German chemist and Nobel Prize winner, Adolf von Baeyer, began working on the formula. According to Wikipedia, 17,000 tons of synthetic indigo were produced worldwide in 2002. To put that into perspective, one pair of blue jeans requires 3–12 grams of indigo to become blue.