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Revisiting Marieke Hendriksen’s Indigo or no indigo?

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Today we revisit a post written in pre-Covid-19 times, when borders were open, planes were flying and we used to travel the world. In this post from 2018, Marieke Hendriksen recounts how her holiday in Laos offered opportunities to learn more about indigo and the local dyeing processes. Elaine Leong

Marieke Hendriksen

Fermenting indigo at Ock Pop Tock, Laos. January 2018.

When you say indigo, the first thing many people will think of is blue – jeans blue. (Or if you’re me, you’ll think first of a seventeenth-century recipe to make decorative blue prunes from wax with indigo. Occupational deformation.) But historically, indigo has been used in many more ways, and to make more dye colours than just blue, as I recently discovered. Today, most jeans are died using a synthetic blue dye, but indigo dyes, made from some of the over 750 species of the genus Indigofera as well as from some other plants, have been used to dye textiles for at least 6,000 years, while other subspecies of Indigofera were traditionally used as analgesics with anti-inflammatory properties.

The term ‘indigo’ according to the OED started to occur from the sixteenth century onwards in various European languages to denote blue dyes from India (or east Asia more generally), but can now also refer more generally to dyes, violet-blue light, or blue hues. It might be argued that the term only really applies to dyes created from Indigofera subspecies, while it could also be said that indigo is any dye created from plants through the decomposition of the glucoside indican, which exists not merely in the indigo-plant, but in woad and various other plants too.

Wash the freshly picked leaves…

While on holiday in Luang Prabang, Laos, I took a weaving and dying workshop with Ock Pop Tock, an organization that was established to preserve the traditional Laotian craft of making hand-loomed textiles. There, I discovered that there is more indigo besides Indigofera, and that one indigo plant can give many more dyes than just blue. They also have a wonderful informative website on natural dyes. At Ock Pop Tock, the plant species used to create indigo dyes is Persicaria tinctoria, or long leaf Japanese indigo, a plant indigenous not to Japan but to China, Vietnam, and Laos. Depending on how the leaves are treated, it can be used to create blue, green, black, and mauve.

…give them a good pounding to create a dye.

Using the fresh leaves creates a green dye, fermenting them for at least five days and adding limestone as a mordant gives a blue dye. Traditionally, the Lao believed that the dye was female, and that it fermented because it attracted a male spirit. To coax the spirit, the pots containing the dye would be dressed in a skirt, and a knife placed on top of the lid to ward off evil spirits that could ruin the dye. The fermentation is actually a naturally occurring oxidation process, with atmospheric oxygen as the oxidant. Regular stirring ensures the process continues. The longer the indigo mixture is left to ferment, the darker it turns. If this mixture is boiled, it turns black. Alternatively, a rare indigenous plant, mak bow or bow vine, can be added to the blue dye to create mauve.

The end result: a beautiful scarf

As part of the half-day workshop, I got to dye a silk scarf with a dye of my choice. I love green hues and wanted to make a dye from start to finish, so I chose to dye my scarf ‘indigo’ green. This was, apart from some pretty intense pounding of leaves, surprisingly easy. I got to pick fresh Persicaria tinctoria leaves in the beautiful garden, washed them, and mashed them vigorously in a mortar for about five minutes. Then I transferred the mashed leaves into a tub, added some cold water and then the raw silk scarf. After kneading the dye into the fabric for a couple of minutes, I could rinse my scarf and hang it to dry. The end result is a beautiful soft green scarf, that is not just a souvenir, but a tangible reminder of the traditional Laotian knowledge about natural dyes preserved and shared at Ock Pop Tock.

Early Modern, Experimentation, Ingredients, Plants and Herbs, Posts

Indigo or no indigo?

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Marieke Hendriksen

Fermenting indigo at Ock Pop Tock, Laos. January 2018.

When you say indigo, the first thing many people will think of is blue – jeans blue. (Or if you’re me, you’ll think first of a seventeenth-century recipe to make decorative blue prunes from wax with indigo. Occupational deformation.) But historically, indigo has been used in many more ways, and to make more dye colours than just blue, as I recently discovered. Today, most jeans are died using a synthetic blue dye, but indigo dyes, made from some of the over 750 species of the genus Indigofera as well as from some other plants, have been used to dye textiles for at least 6,000 years, while other subspecies of Indigofera were traditionally used as analgesics with anti-inflammatory properties.

The term ‘indigo’ according to the OED started to occur from the sixteenth century onwards in various European languages to denote blue dyes from India (or east Asia more generally), but can now also refer more generally to dyes, violet-blue light, or blue hues. It might be argued that the term only really applies to dyes created from Indigofera subspecies, while it could also be said that indigo is any dye created from plants through the decomposition of the glucoside indican, which exists not merely in the indigo-plant, but in woad and various other plants too.

Wash the freshly picked leaves…

While on holiday in Luang Prabang, Laos, I took a weaving and dying workshop with Ock Pop Tock, an organization that was established to preserve the traditional Laotian craft of making hand-loomed textiles. There, I discovered that there is more indigo besides Indigofera, and that one indigo plant can give many more dyes than just blue. They also have a wonderful informative website on natural dyes. At Ock Pop Tock, the plant species used to create indigo dyes is Persicaria tinctoria, or long leaf Japanese indigo, a plant indigenous not to Japan but to China, Vietnam, and Laos. Depending on how the leaves are treated, it can be used to create blue, green, black, and mauve.

…give them a good pounding to create a dye.

Using the fresh leaves creates a green dye, fermenting them for at least five days and adding limestone as a mordant gives a blue dye. Traditionally, the Lao believed that the dye was female, and that it fermented because it attracted a male spirit. To coax the spirit, the pots containing the dye would be dressed in a skirt, and a knife placed on top of the lid to ward off evil spirits that could ruin the dye. The fermentation is actually a naturally occurring oxidation process, with atmospheric oxygen as the oxidant. Regular stirring ensures the process continues. The longer the indigo mixture is left to ferment, the darker it turns. If this mixture is boiled, it turns black. Alternatively, a rare indigenous plant, mak bow or bow vine, can be added to the blue dye to create mauve.

The end result: a beautiful scarf

As part of the half-day workshop, I got to dye a silk scarf with a dye of my choice. I love green hues and wanted to make a dye from start to finish, so I chose to dye my scarf ‘indigo’ green. This was, apart from some pretty intense pounding of leaves, surprisingly easy. I got to pick fresh Persicaria tinctoria leaves in the beautiful garden, washed them, and mashed them vigorously in a mortar for about five minutes. Then I transferred the mashed leaves into a tub, added some cold water and then the raw silk scarf. After kneading the dye into the fabric for a couple of minutes, I could rinse my scarf and hang it to dry. The end result is a beautiful soft green scarf, that is not just a souvenir, but a tangible reminder of the traditional Laotian knowledge about natural dyes preserved and shared at Ock Pop Tock.

18th Century, Bodies, Education, Libraries, Archives & Museums, Series: Charms, Series: Race

A forgotten chapter in natural history: the taxidermy of man

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By Marieke Hendriksen

Having written a book on eighteenth-century anatomical collections, I know a thing or two about historical techniques for preserving (parts of) the human body. As I am interested in natural history collections more generally, I also did some research on the preservation of animal bodies, and even took a taxidermy course myself. However, recently I realised that the preservation of human and animal bodies were historically even closer connected than I had imagined. Yet ideas about which parts of the human body could and should be preserved, and how, diverged greatly, particularly when it comes to skin, or taxidermy. Taxidermy, from the Greek τάξις (taxis) and  δέρμα (derma – I am adding those for people who may not read Greek script), literally means ‘the arranging of skin’.

Fragment of an engraving of the anatomical theatre of Leiden University, early 17th century, showing visitors who appear to discuss a human skin. Contemporary engraving by Willem Swanenburgh; drawing by Jan van ‘t Woudt (Johannes Woudanus).

There are a few known cases of attempts to preserve human skins in their entirety before 1800 – for example, there was a human skin in the Leiden anatomical theatre in the seventeenth century – but that wasn’t stuffed, and such attempts appear to have been altogether unsuccessful. If human skin was preserved, it was mostly small pieces, which were used to study things like skin colour and structure, tattoos, or pathologies. By the end of the eighteenth century, the preservation of an entire human skin in a lifelike pose was of little interest to anatomists. Normal internal anatomy would be studied through dissection and the creation of preparations and skeletons, and pathologies of the skin could be preserved by making preparations of small sections of skin. As healthy skin can be studied perfectly easily in live subjects, there was little reason to pursue the taxidermy of man. This is reflected in anatomical handbooks like Thomas Pole’s 1790 Anatomical Instructor (reprinted in 1813), which gave detailed directions for numerous methods to preserve parts of the human and animal body, including entire heads and foetuses, but did not say anything about how to preserve only skin. On the contrary, Pole advised to remove the cuticle from a head that was to be preserved,  as this would give ‘a brightness to the complexion’.[1]

Jeremy Bentham’s ‘preserved’ head is not on display, but stored in an environmentally controlled safe. Copyright: UCL.

However, with the growing popularity of taxidermy – the mounting of animal skins in lifelike poses – and the rise of physical anthropology in the early nineteenth century, there were a number of experiments with human taxidermy, the most famous of which was probably Jeremy Bentham’s unsuccessful attempt to have his body made into an ‘auto-icon’ after this death. Then there was ‘el negro’ or ‘the negro of Banyoles’, whose faith was described by Dutch author Frank Westerman in his 2004 book El Negro en ik (‘El negro and I’). The remains of this young African San man were stuffed by two taxidermists, the French Verreaux brothers, in the 1830s, and remained on display in a local Museum in Banyoles, Spain, until 1997. Eventually his remains were send for burial in Botswana in 2000. Jules Pierre (1807-1837) and Jean Baptiste Édouard (1810-1868) Verreaux created taxidermy specimens of exotic animals for their father’s Parisian shop in natural historical objects, Maison Verreaux, and, as ‘el negro’ shows, used human bones for his models.

The head of the figure in ‘Arab Courier attacked by lions’ sits detached from the rest of the diorama during restoration work. Copyright: Nate Smallwood | Tribune – Review

For a long time, ‘el negro’ was the only known case of nineteenth-century human taxidermy. However, a recent discovery suggests that the Verreaux brothers used human remains more frequently. In 2016, a human skull was discovered in a mannequin that was part of an ensemble made by the Verreaux studio. Formerly known as “Arab Courier Attacked by Lions”, it was restored and returned to display at the Carnegie Museum of Natural History in Pittsburgh under the title “Lion Attacking a Dromedary”. Although apparently no attempt was made to use human skin in the Pittsburgh diorama, these cases show that there was little reticence when it came to using human materials for taxidermy displays in the nineteenth century, particularly when the human in question was considered ‘exotic’. This is supported by the fact that a popular contemporary taxidermy manual, aimed specifically at museums and travelers, opened with a paragraph on the impossibility of applying taxidermy to man successfully. The book, written by the naturalist Sarah Bowdich (née Wallis, later Lee, 1791-1856) saw six editions – the first in 1820, the last in 1843.

After listing the necessary tools and giving a number of recipes for the cleansing and preservation fluids used in taxidermy, Bowdich opened the section on ‘the preparation of mammalia’ with a somewhat disappointed-sounding statement:

1. Of man 

All the efforts of man to restore the skin of his fellow creature to its natural form and beauty, have hitherto been fruitless: the trials which have been made have only produced mis-shapen, hideous objects, and so unlike nature, that they have never found a place in our collections.

Bowdich went on to discuss the life-like wet preparations made by Amsterdam anatomist Frederik Ruysch (1638  – 1731) as ‘without doubt (…) very useful to science’, before switching to a description of a more successful practice – the preservation of skeletons. Given the tragic history of ‘el negro’ and many other violently obtained human remains in museum collections, it is a cold comfort that the naturalists of the nineteenth century failed at the taxidermy of their ‘fellow creature’.

[1] Pole, Thomas. The Anatomical Instructor ; or an Illustration of the Modern and Most Approved Methods of Preparing and Preserving the Different Parts of the Human Body and of Quadrupeds by Injection, Corrosion, Maceration, Distention, Articulation, Modelling, &C. London: Couchman & Fry, 1790: p.84.

18th Century, Medical Practitioners, Series: French Studies, Series: Minerals

What’s in a name: Plaster of Paris

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By Marieke Hendriksen

One of the problems we face as historians studying and reconstructing recipes is that the names describing ingredients, tools, and materials change over time, and that the meaning of terms itself changes over time. This is even the case with relatively recent recipes and materials that are in theory unchanged as I recently discovered. As part of my research for the ARTECHNE project, I recently looked at instructions for making anatomical casts from plaster from 1791.

Painted plaster cast of a large fibroma of the jaw, 1830s. Courtesy Surgeons' Hall Museums, RCSEd.
Painted plaster cast of a large fibroma of the jaw, 1830s. Courtesy Surgeons’ Hall Museums, RCSEd.

The creation of anatomical casts and models using plaster of Paris became increasingly popular towards the end of the eighteenth century, fuelled by the omnipresence of plaster in the visual arts and interior decoration, and the increasing importance of pathology and later physiognomy within the study of medicine. The latter meant that medical men were looking for durable three-dimensional ways to preserve diseased bodies and body parts that could not be preserved otherwise (e.g. in a preparation), either because decay could not be stopped or because the patient was still alive.

Johan Zoffany, The Portraits of the Academicians of the Royal Academy, 1771-72
Johan Zoffany, The Portraits of the Academicians of
the Royal Academy, 1771-72. Note the plaster models of antique statues around the room.

In his 1790 book The Anatomical Instructor, physician Thomas Pole (1753-1829) not only gave advice on how to make anatomical preparations and drawing, but also included over fifty pages on how to create, colour, repair and maintain plaster casts and models. Pole started the chapter on modelling with outlining the relevance of the quality of the plaster of Paris, or calcined alabaster, that was to be used. He explained that

Illustration of how to make a cast of a diseased bone from Pole's 1790 'Anatomical Instructor'
Illustration of how to make a mould of a diseased bone from Pole’s 1790 ‘Anatomical Instructor’

“…that of a middling price is used for making of moulds; the finer sort is for casts, to be poured first into the mould, when properly prepared; after it has formed a layer of about half an inch, more or less, according to circumstances, then the coarser sort is to be used to fill up the mould, or to give it sufficient thickness.”[1]

But exactly what were the various qualities of plaster for sale in London in the 1790s made of? The term ‘calcined alabaster’ tells us little, as alabaster was and is a collective noun that designates both various kinds of light-coloured, translucent and soft stone used mainly for carving decorative artefacts (often the minerals gypsum or calcite – the former much softer than the latter), and a specific compact and fine-grained variety of gypsum. In the decades after Pole’s publication, the French chemist Antoine François de Fourcroy (1755 –1809) would distinguish nine kinds of calcareous sulfate, one of which was sulfate of lime or common gypsum. In an 1810 ‘dictionary of the arts’ Fourcroy’s sulfate of lime or common gypsum was described as follows:

“Sulphat of lime, or common gypsum, or plaster-stone. This substance is white, more or less inclining to grey, interspersed with small brilliant crystals, easily cut with a knife. it is found disposed in Paris. We shall hereafter find, that it is not pure selenite, but owes its most valuable property, as plaster, to the admixture of another kind of earth. (…) Calcareous sulphat is likewise found dissolved in waters, as in the well-waters of Paris; it is never pure, but always combined with some other earthy salt, with base lime or magnesia. This salt has no apparent degree of taste. It decrepitates if a sudden heat be applied to it; it is then of an opaque white, in which state it is called fine plaster, or plaster of Paris: by this calcination it loses about twenty in one hundred.”[2]

Entrance to the Montmartre gypsum quarry. Probably early 19th century, artist unknown.
Entrance to the Montmartre gypsum quarry. Probably early 19th century, artist unknown.

As this fragment suggests, plaster of Paris indeed derives its name from a large and very pure gypsum deposit at the Montmartre and Menilmontant hills in Paris – there were plaster quarries at this site at least as early as the year 500. This led “calcined gypsum” (roasted gypsum or gypsum plaster) to be commonly known as “plaster of Paris”, even after the exhausted quarries were converted into Montmartre cemetery and the Buttes de Chaumot gardens respectively in the mid-nineteenth century. Although not all plaster came from Paris at the time Pole was writing, there is a fair chance that much high-quality plaster was indeed plaster from Paris.

Today, gypsum plaster, or plaster of Paris, no longer comes from Paris, but is still produced by heating powdered gypsum to about 150 °C. When mixed with water, this forms a paste that will harden within minutes, producing an exothermic reaction, which means it warms up. You can easily buy ‘plaster of Paris’ from artist’s supplies shops and online retailers, but none of these mention the exact chemical composition. Yet before I (or anyone else) can try my hand at reconstructing Pole’s instructions I will need to find out whether the best, finest plaster of Paris still contains a percentage of lime or magnesia, what the ‘coarser varieties’ that Pole described contained, and whether these are still available.

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 648718), and was supported by the Wellcome Trust (grant number 203403/Z/16/Z).

[1] Pole, Thomas. The Anatomical Instructor ; or an Illustration of the Modern and Most Approved Methods of Preparing and Preserving the Different Parts of the Human Body and of Quadrupeds by Injection, Corrosion, Maceration, Distention, Articulation, Modelling, &C. London: Couchman & Fry, 1790: p. 202-3.

[2] Wilkes, John. Encyclopaedia Londinensis, Or, Universal Dictionary of Arts. Vol. 4. London: J. Adlard, 1810: p. 230.