indigo vat in India

A Drop in the Indigo Bucket

Fifth in a series about how our Indian fabrics are made.

dark blue natural indigo dyed jamdani cotton fabric

Indigo! The most beautiful of blues! With the recent arrival of our indigo block prints, we wanted to take a look at this magical dyestuff. It’s a huge topic, so this is just a short introduction to whet your curiosity — a mere drop in the indigo bucket, if you will (although usually it’s a vat!) — and show you how some of our fabrics are made.

People have always wanted color in their lives and colorful things to wear. The history of fabric dyes is fascinating because of the great lengths to which humans have gone to possess beautiful colors. In some parts of the world indigo was the first known dyestuff, which is especially amazing because it’s not at all easy to get the color out of the plant.

Indigofera tinctoria by Kurt Stüber [1] -

The plant, Indigofera tinctoria, probably originally came from the Indian subcontinent, hence the name. (Indika was the Ancient Greek word for India, their source for blue dye. In Hindi, indigo is called neel, which means blue.) It’s a leafy shrub which gardeners will recognize as belonging to the pea family. Other plants around the world, such as woad in Europe, also contain indigo but in much smaller quantities, and are less useful for modern dyers. (Attributions for images above and below at end of page.)

cake of indigo Photo by Evan Izer (Palladian)

To obtain the dye, indigo leaves are first fermented in water. A chemical base such as lime is added and the mixture is aerated. A sediment precipitates from this solution, is solidified into beautiful blue cakes like the one above, then sold to dyers.

indigo vat with purple scum on top

But indigo is not water soluble, so the dyer must grind the cake into powder and ferment it again. In a carefully prepared vat with an even temperature (often partly buried in the ground, like the one shown here), a base such as ammonia is added to the indigo along with something sweet, like dates or molasses. This causes various chemical reactions to take place. When purplish scum covers the vat and the dye liquid has a funky green color and a rather unpleasant smell, it’s ready for dyeing! Above, an indigo vat at rest, showing the purple scum or "flower" on the surface; below, the greenish liquid dye beneath is visible when the vat is stirred.

indigo vat with green liquid ready for dyeing

The cloth is submerged in this liquid. Then comes the magic moment: when fabric is lifted from the indigo vat, it’s a strange yellow-green color. But in a moment the indigo reacts with oxygen in the air and turns blue before your very eyes! It's amazing to see. Cloth and yarn can be dipped repeatedly in the dye vat in order to deepen the color. After dyeing, the now-blue fabric is stretched out in a field to dry (below).

Considering the obscure chemical changes and crazy color transformations, it’s understandable why indigo dyers were often regarded as magicians in the past, and why their vats were considered living things that had to be fed and humored. (With care, a vat can be used for many years.) Textile historians believe that indigo has been used for dyeing in India for at least four thousand years despite it being such a complicated and labor-intensive process.

indigo-dyed fabric drying in a field

Working with indigo is like cooking — it turns out a little bit differently every time. Each dye-bath has its own character due to the many chemical reactions involved, as well as differences in water chemistry and in the indigo itself. Unlike other dyes, indigo does not penetrate the fibers that are dyed in it. Instead, it is a coating on the cloth and may gradually rub off. The changes in color and texture over the lifespan of the cloth are part of the enduring appeal of indigo-dyed fabrics like denim; the evolution of the fabric echoes the lives we live in our clothes. In a poetic sense, this seems to make time itself visible.

indigo-dyed shibori fabric

We often associate indigo blue with textile techniques from specific cultures. Two traditional uses for indigo, shibori and block printing, both involve resist-dyeing but in different ways. A resist makes some part of the cloth impermeable so the indigo will not be absorbed when the cloth is added to the dye vat. For shibori and other tie-dye techniques, fabric is folded, tied, or clamped so very tightly that the dye cannot penetrate those areas. For example, to make the design shown above, the fabric was elaborately folded and clamped between blocks of wood. Only the edges of the fabric extending beyond the blocks could absorb the indigo, leaving the rest of the fabric undyed. The pattern is revealed when the fabric is unfolded.

For block prints, a resist substance such as mud acts as a barrier to prevent the absorption of dye. Before the fabric is dipped into the indigo vat this resist is printed onto the fabric to protect the part of the design that is not to be dyed. When the resist substance is washed away after dyeing, the resist-printed areas are visible as white against blue. Printers and dyers can work together to build up layers of color and pattern by repeating the resist-printing and dyeing processes, resulting in multiple shades of blue, as seen in the fabric pictured below. (Read more in the previous article, A Look at Hand Block Printing.)

indigo block print fabric with two shades of blue

Most modern indigo-dyed clothing, such as denim, is dyed with synthetic indigo. This is a chemical version of the original plant-based dye and is much easier to use. However, natural indigo derived from plants has been gaining in popularity due to renewed interest in historic textile traditions and as an alternative to petrochemical dyes.

light blue natural indigo dyed scarf

We love natural dyes not only because they’re interesting (and beautiful!), but also because they connect us to the great big history of human ingenuity. If you ever have a chance to take an indigo-dyeing workshop, do — it’s fascinating! And even if you aren’t interested in dyeing fabrics yourself, indigo and its importance throughout history in many cultures around the world is a rich subject. Pick up any history of color or dyeing, or even better, Indigo: Egyptian Mummies to Blue Jeans by Jenny Balfour-Paul, to learn more about humanity’s long obsession with blue.

Read the previous article: A Look at Hand Block Printing

Read the first article: A Visit to a Weavers' Village

Shop for indigo block print fabric here.

indigo dye vat

Image sources:

Indigofera tinctoria: Photo by Kurt Stüber [1], CC BY-SA 3.0, via Wikimedia Commons

Indian indigo dye lump: Photo by Evan Izer (Palladian), CC BY-SA 2.5, via Wikimedia Commons 

All other images by Loom & Stars

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