Dyeing with Fresh Indigo Leaves

On some days it’s hard to believe how recently we traveled freely worldwide, meeting new people and experiencing new places. Three years ago I attended the natural dye symposium in Madagascar, where I first met Hisako Sumi who started me on my current journey of making and maintaining indigo fermentation vats. As I was harvesting Persicaria tinctoria leaves in the garden, I was reminded of the fresh leaf indigo dyeing that we saw being done in Madagascar. 

Many of us are growing indigo in our gardens right now and have likely had the pleasure of experimenting with fresh leaf indigo dyeing on silk.  It’s like magic to see the lovely turquoise color emerge from the cold leaf bath.

The indigo that grows in Madagascar is Indigofera erecta. It is a perennial in that climate and the leaves are harvested from the bushes as needed. The leaves were used to dye the raffia fibers directly. There was no vat or reduction. 

Yet, the dyers took this “cold” process one step further. The ambient temperature dyebath produced a lovely clear turquoise blue color on the raffia. When heat was applied, the color deepened and shifted.

This approach of heat application was new to me. When I inquired about it, both Hisako and Dominique Cardon indicated that they were both familiar with this phenomenon. Hisako sent me an image from a scientific report done by Dr. Kazuya Sasaki that documented the range of color that could be obtained from fresh leaf woad by increasing the temperature. Once armed with that information I was able to reproduce that range of color, nearly exactly, on silk and and on multi-fiber test strips, though the results were not precisely the same as those we saw in Madagascar. 

Indigo vat dyeing compared to fresh woad leaf dyeing of various fibers, at different temperatures.

I have always understood that the process of fresh leaf dyeing with indigo is primarily used on silk – a protein. Yet, the dyeing we witnessed in Madagascar was done on raffia. Why did this process work so well on raffia- a cellulose fiber? I posed the question to my colleague, Joy Boutrup. “Raffia is almost pure lignin” she said. Lignin is an organic polymer and has a strong affinity for dye. 

This week I repeated the tests with Polygonum tinctorium on silk broadcloth and raffia. I used a greater quantity of leaves this time – a blender full of leaves for a few small samples vs. less than 100 g. I puréed the leaves this time rather than chop them up. The “coldest” blue is a deeper shade but otherwise the results are very similar. I freely admit that I don’t understand, chemically, why the colors change with the temperature:

  • Are there other dyes attaching?
  • Has the indigo been transformed by the temperature? 

Maybe someone else can enlighten.

I have always suspected that the lightfastness of the fresh leaf indigo dye is not to the same level as the color obtained from a well reduced indigo vat. I will do lightfast tests on this range of color and report back in a later blog. 

Three years ago, the trip to Madagascar taught me about an approach to dyeing that I had never seen before –  truly one of the gems of travel. We may not be free to move around for now,  BUT other opportunities continue to present themselves on the web. One of the most exciting upcoming events is this year’s Textile Society of America Symposium: Hidden Stories: Human Lives.

Originally planned to be held in Boston this fall, Hidden Stories: Human Lives will now be live and completely online October 15-17. This biennial event brings together scholars, curators, and artists from all over the world who will present their original research in the form of organized panels and talks. Fee structures for the symposium have been completely re-vamped in order to make this event accessible to all – no matter where in the world you might be. Registration has just opened and you can see the full program here. In addition, You can also read about the keynote and plenary speakers. Hope to see you there!

Lightfastness of Dyes – an Historical Perspective

A dear friend recently put a small booklet into my hands: Fast Dyeing and Dyes by James Morton.  It is the bound proceedings of a lecture that Morton delivered to the Royal Society of Arts in London, 1929. 

Morton’s father, Alexander Morton, founded the weaving company of Alexander Morton & Co, in England in the late 19th century.  The son, James was trained as a chemist and specialized in the use of permanent lightfast dyes for cellulose textiles. In the narrative, James recounts work that he  accomplished in 1903 to develop a palette of lightfast dyes for textiles. It was an interesting time in the development and use of textile dyes.  Up until the second half of the 19th century, natural plant and insect dyes were the source of all textile colors, but by the early 20th century chemical dyes were quickly replacing the natural dyes in industry. 

Morton’s company specialized in producing woven furnishing fabrics for curtains, carpets, upholstery and tapestries.  He spoke of observing one of the company’s tapestries in a store window display. After only a week’s time, the colors had faded dramatically. This led him to question the dyes they were using. He commandeered his family greenhouse (which had previously contained tomato plants) to set up a series of lightfastness tests. He tested fabrics from his own company as well as those from others. The results he described as “staggering”. Even deep shades of color applied to expensive fabrics became almost white after only a week’s time. He made detailed notes and documented each sample. 

After making these careful observations, his goal became one of identifying a few colors (produced by chemistry) that could be relied upon and that performed well. Morton believed that even a limited range of colors that would remain on the textile over time was far preferable to a large palette of color that would degrade quickly. The company trademark Soundour was born – a combination of the word “sun” and the Scottish word “dour” meaning stubborn or hard to move. He identified the Alizarines as “good friends” which kept their shades. This was a class of chemical dye, based on the synthetic manufacturing of alizarin, the primary red colorant in madder root.  In 1869 it was the first natural dye to be produced synthetically. Colors derived from minerals were acceptable as sources for light browns.  Indigo was deemed unsatisfactory for longevity on cellulose but Indanthrene vat dyes, new to the market, served as a good source of yellows, blues and greys. (These are the same vat dyes that I previously used in my own work.)

All the chosen chemical dyes were tested thoroughly, both in the greenhouse and on rooftops in India, where the sun was hot and intense and the humidity was high. The result was a carefully chosen palette of color that could be advertised as reliable and be priced accordingly – significantly higher priced than other fabrics on the market. The goal was to have colors that would last as long as the textile itself.

What strikes me about this story is the recognition of lightfastness being of value at a time when there was such excitement about the ability to easily produce almost any color through the use of the new “chemical” dyes. Morton changed the industry’s awareness of and approach to the use of synthetic dye color.  Interestingly, he stated that “Some manufacturers questioned the wisdom of raising the standards so high…”

I can’t help but see a parallel to today’s re-discovery and excitement about natural colors. That excitement often causes a “blind spot” when it comes to objectively looking at the longevity of some dyes. If the experience of making color is the singular goal then it doesn’t matter so much how long the color will ultimately last, but if there is a customer with an expectation that the color will last as long as the textile, then colorfastness is a different and critical matter. 

Professional natural dyers have made decisions over the centuries to provide customers with the best quality colors possible. The Dyer’s Handbook: Memoirs of an 18th -century Master Colourist, by Dominique Cardon makes the following statement about testing for “false” colors: “It is not enough for the dyer to have acquired knowledge on the drugs that are necessary to him and on their properties, and to have managed to employ them with success. He must also distinguish the fast colors from the false ones…”

All dyes fade – that’s a fact. And all textiles will deteriorate. My colleague, Joy Boutrup, says that acceptable fading of a dye results in a lighter version of the original hue while the integrity of the original color is maintained: a lighter indigo blue, a softer madder red etc. – not an “ugly beige color” that has no relationship to the original. And the ultimate goal is that the color last as long as the textile.

My own current study of “fast” and” fugitive” dyes on wool yarn: Indigo over-dyed with cochineal vs. logwood. Original colors (left) and after 3 weeks of direct sun exposure (right)
“Fast” and” fugitive” dyes: Cochineal vs. Brazilwood. Original colors (left) and after 3 weeks of direct sun exposure (right)