The colour blue is one of the rarest colours in nature. For thousands of years, it was also one of the most difficult colours to recreate. Cloth dyed with blue pigment was rare and valuable, and the people that dyed it were considered magic.
In times past the word 'indigo' referred to a blue dye or pigment which was extracted from the green leaves of indigo-bearing plants, or to textiles dyed with this pigment. Making and using indigo was a complicated and precise process which was difficult to learn. Then, in the mid-19th century, the colour blue was synthesised chemically for the first time. Suddenly, a dye-colour which took weeks to make and years of practice to master could be created in a matter of hours. Blue textiles, once so costly, became cheap. Natural indigo and indigo cloth, once a source of income for many people in indigo-producing countries, disappeared almost overnight. And the word 'indigo' lost its magical, alchemical significance and came to be associated simply with the colour blue.
The art of vegetable, or natural, indigo dyeing disappeared, and with it disappeared the true and luminescent blue shades obtained from this method. Our eyes became accustomed to the flat blues of the chemist's laboratory. People began to believe that there was no difference between the chemical blue and the blues produced by vegetable indigo, because they no longer had anything to compare. But there is a difference, a very big difference.
The blue shades produced by the ancient methods of dyeing are unmatchable by any other dyeing process, and have a close affinity with the iridescent blues produced by nature, the blue of the sky, of a butterfly's wing, of a bird's plumage. They are not just blue colours, they are blue medicine, healing and soothing. They are light- and colour-fast and can last for hundreds, even thousands, of years. They reflect the colours of nature because they are entirely natural. They contain the energy of the living organisms that made them. They are magic.
Indigo dyeing originated separately in different parts of the world at different timesand in different ways. There are over 800 species of indigo-bearing plants found throughout the world, and of these, almost 600 can be found in Africa. Indigo therefore has a very old and unique history on the African continent. The dyeing traditions in West Africa date back many thousands of years and are intricately intertwined with many cultural and religious traditions in this region. Two of the African species of indigo-bearing plants, Indigofera arrecta and Lonchocarpus cyanescens, which are indigenous to West Africa in particular, contain the highest amount of indigo pigment and produce the most saturated blues of any indigo-bearing plant in the world.
To produce indigo dye from the green indigo leaves is a long and exacting process. The indigo in the leaves is inaccessible as a pigment or as a dyestuff; it will not dissolve in water and is not particularly concentrated. To access the colour, the indigo must be made water-soluble. The technique that I use utilises the whole leaves and is an ancient method indigenous to West Africa – a similar method is still used in Japan. Other cultures, such as India, have traditionally extracted the indigo pigment from the plant by using a simplified fermentation process initially. The indigo pigment is then pressed into cakes, and when it is activated as a dye, it is easier to control the quantities and the process, because the organic component, the leaves, have already been used and discarded. Powdered indigo is easier to transport and can be used far more easily on an industrial scale. But the colours produced have a different quality. In a fermented vat, the plant matter remains in the vat the whole time, and the vat is alive. The intense, saturated colours of a fermented vat are a result of the synergistic interactions between the plant matter, the bacteria, and the environment in the vat; every aspect of the vat contributes to and affects the colour.
For a West African fermented indigo vat, first the fresh young leaves are collected, crushed and dried, and placed in a large clean vat. pH neutral and chemical-free water is added and the crushed leaves are left to macerate. After a while, bacteria start to grow in the mixture, and the leaves begin to ferment.
The bacteria are fed a mixture of flour and something sweet like honey or date syrup to encourage them to grow. When the fermentation process is well underway and the bacteria are healthy, an alkaline liquid, made from mixing water with wood-ash and straining it off, is added to the dye-vat. This alkaline liquid reduces the insoluble solid indigo pigment in the fermenting leaves into a water-soluble form. The liquid in the vat changes its colour, becoming a brackish yellow. At this stage the indigo is referred to as indoxyl or white indigo. The whole process takes between seven and ten days depending on many environmental factors, and throughout this time, the vat must be watched carefully to ensure that the bacteria are well-nourished and that the temperature and the pH level remain at consistently the right levels. When the vat is ready, the surface of the liquid will show an iridescent purplish-blue foam.
The textile to be dyed is immersed into the dye-vat, but it doesn't change colour yet. It is only when the textile is removed from the liquid and exposed to the air that the soluble white indigo oxidises back into its solid blue indigo state, colouring the textile. This happens in a matter of seconds - as oxygen hits the textile it changes from a yellowish colour to green, then turquoise and finally blue. The indigo forms a direct chemical bond with the textile fibres, rendering the dye light- and colour-fast. The colour can be deepened by repeated immersions in the dye-bath, but because each immersion uses up the bacteria in the vat, after a number of immersions, the vat must be left for the bacteria to regenerate. The vat can be kept alive for many months if it is carefully nurtured, but over time, the bacteria colonies weaken, and the blues obtained become lighter and lighter, but also more and more luminous. Dark indigo can be achieved best by multiple dips in a young vat, but real light icy blues are far more difficult and depend on an old, well-maintained vat.
The process of making and working with real indigo is time-consuming and no stage can be skipped or shortened. Understanding how to build a vat and produce consistent and deep colours has taken me many years, and I am still learning.