Video - The secrets of... indigo! #5

WHY TALK ABOUT INDIGO?

The only way to have a 100% natural blue dye is indigo.

It is a dye that holds well on natural fibers like cotton but also animal fibers like wool, which is quite unique for a vegetable dye.

So yes, the dye lightens a little over the years, but it remains a beautiful blue, unlike other vegetable dyes. This is demonstrated in particular by the blue parts of the Bayeux tapestry.

What I especially appreciate is the ability of indigo to mix with other dyes, you get a truly diverse color spectrum. So much so that it will become an essential dye in medieval dye shops, particularly to have more durable colors over time.

The process of extracting it is quite unique and using it is almost like alchemy. It is not within the reach of just anyone, which has contributed to creating its legend.

Because in nature there are no blue plants. To obtain indigo, you need indican or isetan b. Depending on the type of plant, the color may be invisible.

It is therefore necessary to extract the pigment from the plant. However, it is not soluble, which is very annoying for a dye. Finally, to give it its particular blue color, it must be brought into contact with oxygen.

THE DISCOVERY OF INDIGO

How it all began ?

We still don't have clear answers! There probably never will be.

A priori, several civilizations would have discovered it somewhat separately, not necessarily at the same time.

What's surprising is that it's a color where you need some manipulation to use it as a dye, so it's quite remarkable to see that everyone was able to discover it in their own way.

Perhaps indigo leaves that were soaked in urine or touched by an ash-filled liquid could “accidentally” color the leaves blue.

What is even more curious is that we find indigo in certain legends, like in South-West Asia or Liberia for example. For these civilizations, we find stories that tell of the process of transforming a plant into a blue hue.

Imagine the revelation, at a time when there weren't many other natural colors besides red, ocher, black and brown.

It is therefore a practical color for arts and textiles. In fact, plants grow almost everywhere on the globe.

INDIGO AND ANTIQUITY

The word indigo comes from the Greek word indikon, which became indicum in Latin to designate a substance coming from India, which suggests that the Gallo-Romans imported this substance from antiquity.

We have even found traces of indigo used 3000 years BC, notably in Egypt where certain mummies were dyed with indigo.

At the time, it was a color that was a sign of wealth because it was difficult to obtain but above all it held up well over time.

This time, we are not talking about plants but about crustaceans. This indigo was extracted from a small shell, the spiny Murex or the dye Murex. Knowing that it was necessary to kill 10,000 shells to extract one gram of indigo!

Tyrian purple was also made with this shell, but as it was expensive it was a color reserved for the elite.

According to Pliny the Elder, the dye was extracted by crushing the shells, leaving everything to putrefy for three days in salty, alkaline water. Then he boiled everything for ten days. You can imagine the smell!

If indigo has been used for a long time in Europe and Asia, this is also the case for Central and South America, and those as early as 700 BC.

So a fun little detail, they mastered the red dye well thanks to the cochineal, an insect . On the other hand, indigo was a rarer shade, more complicated to obtain and therefore more mysterious, it was reserved only for symbols of power and religion.

This is how indigo acquired such symbolism over the centuries, quite simply because it was the color to color the gods.

On the African side, there is also a culture of indigo but we did not really know when it appeared, in particular because of a climate not conducive to the conservation of textiles, until an interesting archaeological discovery.

In the 60s and 70s, an expedition took place in the Dogon country in Mali and there we found fabrics with indigo from the 11th century which proves that the natives of that time already had an advanced level in the design of this tincture.

INDIGO IN THE MIDDLE AGES

On the European side, in the 16th century, with the development of trade routes to India, indigo from the indigo tree was a luxury good. Bringing products from India, such as pepper or other spices, was reserved for prestigious uses.

Indigo from the indigo tree was highly sought after because it gave a deeper blue than dyers' pastel. Previously, pastel was the only way to obtain a blue dye, also called waide or woad . It was cultivated almost everywhere in Europe, in France, Italy, Germany and even England.

A priori at the beginning it was cultivated for medicinal virtues, in particular for its antiseptic use.

In France, Languedoc was the region most famous for the cultivation of this plant, which largely contributed to making it a rich region.

The merchants of this plant had great fortune, due to their large properties, notably their fields, but also because they were personally involved in the marketing of the dye. They were called pasteliers.

THE ARRIVAL OF INDIGO FROM INDIA

The arrival of the indigo tree from India was a huge blow to the woad trade. It was then that the price of pastel completely collapsed after two golden generations , especially with the development of European colonies in India.

Unfortunately, given the heavy workload to produce indigo, they exploit slaves from Africa. Without this totally exploited and inexpensive labor force, the history of indigo would surely have been very different.

It got to such a point that when indigo prices were at their peak, indigo could be exchanged with a slave, for equal weight, it was total madness.

To satisfy Europe's demand for blue, many slaves paid with their lives.

NATURAL INDIGO

Indigo comes from several plants and even several animals.

Plant-wise, the best known is the indigo tree but you have others! The indigo tree is from the Indigofera family, which includes nearly 800 species, including 600 in Africa.

It is a small shrub with pink leaves, which are absolutely not blue. The specificity of this plant is its ability to grow in many places.

The other type of plant that produces indigo is woad, which is a small plant that produces yellow flowers and again absolutely not blue. It is a cruciferous plant, just like radishes, mustard or cabbage.

So you understand, there are a multitude of plants that allow the emergence of indigo dye. Now let's see these plants across the continents:

• In Japan and China, it is another herbaceous plant called Persicaria tinctoria , dyer's knotweed (or indigo persicaria). The leaves aren't blue either!
• In South Asia there is another plant: Strobilanthes cusia or Assam indigo
• In Africa it uses Philenoptera cyanescens , also called Yoruba Indigo +
• In India and Burma we talk about Wrightia tinctoria or dyer's laurel

THE PRODUCTION OF THE DYE

Once we have the leaves which are very green and not at all blue, how do we extract the indigo and dye our jeans?

You are not the only ones to ask yourself this question, and its extraction has generated a lot of curiosity throughout the story.

WHAT’S THE CHEMISTRY BEHIND IT?

To put it simply, when we soak the leaves in water, the indican transforms into indoxyl, and when we shake this liquid vigorously to bring in oxygen, the indoxyl transforms into indigo, if I summarize very very very roughly.

For a very long time, we didn't really know how this chemical reaction happened; it was completely unknown.

For pastel it is different again, because it is not the same precursor. Instead of indican, there is isetan B, a more fragile molecule that can be left to macerate in lukewarm water, as with tropical plants.

In practice, you have three methods, be careful, we start with a fifth level chemistry course.

1. FROM FRESH LEAVES

The first, the one used in traditional societies, simply put fresh leaves in a pot, with urine or water with ashes to initiate fermentation, in order to reduce the oxygen content. It is the decomposition of the leaves which will lead to the production of colorless indoxyl.

We then remove the leaves to leave only the liquid which I remind you is always colorless.

Afterwards we put the clothes or the fibers to be dyed in, we take them out and on contact with oxygen it turns blue!

The problem with this technique is that it is not very concentrated in indigo. So you really have to soak them several times and for hours to get a blue garment. In addition, you have to be near the place where indigo is grown to have fresh leaves.

2. FROM DRIED LEAVES

The leaves are dried so that they can be transported and stored more easily.

This is the traditional method in Japan and East Africa. But the problem is that even if the leaf is dried, it can still mold and it is not very suitable for a trip between two continents, which brings us to the third method of extraction, jealously guarded by the Indians who had discovered it since Antiquity, maceration.

3. FROM MACERATION

In fact, from these leaves, they had managed to make a sort of blue mud, and by drying it, it made pieces of indigo which then had to be reduced to powder. It was a lot of work, but it allowed for much easier transportation of indigo between countries, and it became a very important economic activity for India.

CONCRETELY, HOW DOES THIS HAPPEN ?

The leaves are put in a tank of water for 12 hours, then the liquid is transferred to another tank. Afterwards, this liquid is vigorously stirred to bring in oxygen and the indigo will fall to the bottom of the tank in the form of mud.

Once obtained, it was dried in order to reduce it into powder or block. For transport, some peoples kept the wet mud in jars or waterproof buckets as in Asia.

If you are curious, you can see all the stages of this traditional extraction in this Indigo, blue journey of a textile creator by Catherine Legrand (editions of La Martinière)

Honestly these two books are remarkable, the work done is monstrous.