Isabella Whitworth

probably more than natural and synthetic dyes, wax, resists, and history


French Connections

I’m back from a trip to the DHA (Dyes in History and Archaeology) Conference in La Rochelle. La Rochelle hosted the ISEND Conference in 2011 and so I was already familiar with the conference venue – a former fishmarket, now the exhibition and conference centre  L’espace Encan.

This is a text-heavy post, so here’s a picture of La Rochelle to keep you going.


La Rochelle

A DHA conference annually attracts a wide variety of delegates from various disciplines. This year there were about 90 of us. Our number included chemists, conservators, artists, historians, researchers working with natural dyes, and students at various academic levels. At a DHA conference you can find yourself sitting next to someone from the British Museum, the Louvre or the Rijksmuseum, or an independent scholar who is simply passionate about parchment. It is a friendly assembly and all are welcome. Even if, as a non-chemist, you sometimes sit boggle-eyed through muscular technical papers full of graphs, analysis and molecular data, there is always something to be learned. I’m told that in early DHA days (this was the 32nd meeting!) there was a heavy bias towards these more scientific analytical papers but that nowadays the balance is more even, with a good mix of historic /scientific presentations. The selection committee who choose proposed papers must have an intensely hard job. Of the 24 or so papers accepted, several intrigued me but as none have yet been published this handful of comments remains general.

Purple Parchments

One paper involved the analysis of  purple-dyed parchments. Very little work has been done to analyse the source of the purple colour in such codices and as far as I understand, there is currently no scientific evidence that shellfish dyes were used on the parchments. Non-invasive methods are normally used in their analysis, essential if precious manuscripts are to be studied without damage, and these methods can make it more difficult to identify dyestuffs. (With a parchment it isn’t so easy to remove a physical sample as it can be from a textile, where a loose fibre may be available).

There was a mention of dyeing parchment with orchil, and my ears twitched. Last year I was asked to dye some parchment samples with orchil – and dye they certainly did. But it was apparent that the temperatures and immersion involved in dyeing with orchil stiffened and damaged the parchment quality. I felt that this method wasn’t viable. Cold-dyeing seemed to yield a more sympathetic result but I have no idea to what extent the parchment quality was affected as I was only sent miniscule pieces of parchment to dye.

In the post-presentation question session it emerged that the term ‘dyeing’ means different things to different people. Some delegates considered ‘dyeing’ could be the layered painting on of dye and not dyeing by immersion, as working dyers think of it. Now, I should say that I tried painting orchil on too, but soon lost the will to live. It would be immensely protracted to paint on sufficient orchil to build up a good colour. That’s not to say it would be impossible, I just didn’t have the time or the resources to continue.

It will be interesting to learn more about this research. Maybe at Glasgow and DHA 33 next year? The dates are October 30th – 31st 2014.

Shearings and Clippings

Magnified images had been studied by the presenters which showed lumpy-looking particles in the red lake used in several medieval paintings. These indicated that they were reclaimed dyes from red-dyed wool, made into lakes for painting. The reclaiming of red lake pigment dyestuffs from clippings of dyed wool revealed that it made good economic sense to extract the dyes and to reuse them as painting materials. The dyeing of red, from whichever dye source, was expensive and thus waste material might be reprocessed. Again, I encountered problems with a mutual understanding. Initially I was confused by the words ‘shearings and clippings’ which were used by the presenters. I associate these words primarily with sheep-shearing!  In the paper the words referred to waste dyed cloth after cutting woven material – or yarn.

The finding of these ‘reclaimed reds’ isn’t in itself new. A 1996 paper by Jo Kirby and Raymond White goes into great detail (find it here) and also lists a  number of paintings in which red lake pigment dyestuffs have been found. Have a look. You may be amazed.


A couple of years ago, at DHA in Lisbon, I presented a paper about the trade in dye lichens from Angola through Lisbon. I have yet to publish this, for several complicated reasons. But I had an interesting conversation with another delegate which led me to sending a very small quantity of dye lichen and a recipe to the University of Évora. I heard no more, and forgot all about it. At La Rochelle my Portuguese colleague and  her team presented a paper in which they had measured and tracked the breakdown of the depsides and depsidones (the dye precursors) in the orchil preparation process until purple chromophores formed. Chromophores are the part of the molecule responsible for colour. The chemistry was patiently explained to me in a coffee break and I now understand rather more about the process that before – although I wouldn’t like to take an exam just yet. DHA is great for this kind of contact and co-operation.

DHA=GFZ: A Gremlin Free Zone

If you read the previous post you will now that I was co-presenting a paper at DHA 32  and I wrote about the snaggly-toothed IT gremlins that lurk for unprepared presenters. I am pleased to report that my eminent co-author, Zvi Koren, had done an admirable job on gremlin-bashing (he’s ace at puns too) and everything loaded and presented totally as expected. So did everyone else’s, and we all benefited from calm, unobtrusive technical expertise delivered by Florent Glatard of ARRDH- CRITT Horticole. Our presentation was really well-received but I will not be writing about it until formal publication.

Thanks to DHA 32 organisers Anne de la Sayette and Dominique Cardon

Anne de la Sayette is the Directrice of ARRDHOR – CRITT Horticole, a ‘centre of research, innovation and technology transfer in horticulture’. Dominique Cardon is well known to most natural dyers as author of Natural Dyes: Sources, Tradition, Technology and Science. She is also Emerita Senior Researcher at CNRS, the French national centre of scientific research. CIHAM UMR 5648 CNRS  (an institution, not a mathematical  equation..)  is one of the most important research centres in France for history, literature and archaeology of the Middle Ages. A new book by Dominique is about to be published but I don’t have the details: as soon as I do I will add them to a post.


If you have got this far you deserve a pictorial prize. Using photos from DHA is tricky as I feel I should ask people’s permission before posting their images on a blog, so here is something rather special from the trip home.

I had never been to Carnac in Brittany until last week and I had no idea of the scale and breadth of the entire site. But it seemed most serendipitous to discover, on some stones of the alignments, a quantity of orchil lichen. Naturally, I did not touch it. But here are some images to reward stalwart readers. The orchil lichen is in the left hand image only.


Reasons to be Stressful


I’m halfway between two presentations. The first was for the 6 Guilds of Weavers, Spinners and Dyers at Stratford where I spoke about orchil and how the trade in lichen dyestuff reached global proportions in the late nineteenth century. I thoroughly enjoyed my day at Stratford which included a talk by co-speaker Joan Baxter on the way the East Sutherland landscape influences her tapestries. Her recent collaborative work with dancers Between the Web and the Loom was interesting and she showed some video clips. But I can’t find any images on the internet to provide a link beyond this one (about the dance) and this one (about the tapestry she wove).

The second presentation is for the Dyes in History and Archaeology Conference (DHA) in La Rochelle, France. That’s later this week, is about something else entirely, and it’s going to be rather sensational.

Friday 4th October

11:45          Treasures from a Leeds Dye Chemist: A Century-Old “Tyrian Purple”?

                   Isabella Whitworth, Zvi C. Koren

If you want to know more about the sensational, come to La Rochelle. Otherwise, I’m sorry, you may have to wait a little. To download the whole DHA La Rochelle programme, visit this page and follow the links at the bottom.

For the moment, here is a taster in the form of some images. You will see two men, both chemists. There is a brother and a sister, and the son of a famous father.

Lectures and technology

Those who are of ‘a certain age’ will remember that one of the worst things that could happen when giving a lecture was that you dropped all the slides just prior to going on stage then reloaded them upside down, in the wrong order and back to front.

Technology wasn’t satisfied with such piffling levels of stress. So it created Macs and PCs and system updates; memory sticks and SD cards and PowerPoint and embedding. It now arranges that hosts provide an ancient laptop unable to read anything post 1910;  it organises missing leads, the wrong leads, deflating batteries, clickers that die, videos that won’t load and projectors which will have nothing to do with your laptop.

I have watched entirely respectable speakers show a presentation devoid of images because they haven’t checked their Mac presentation on a PC – or haven’t embedded their photos.

As a result I am obsessive about options. At the 6 Guilds event I took my own Mac laptop, own projector, requisite leads plus a boggling array of memory sticks and SD cards correctly formatted and checked out on a neighbour’s PC. In fact, the options proved unnecessary as the 6 Guilds laptop was up-to-date, the memory stick loaded, and two super-calm techies were in control.

For DHA, all presentations have to be sent in advance of the Conference which is good sense – in theory. You will be informed that something has arrived, but you still don’t know if the presentation shows exactly the way you designed it. So, when you get there, you need to check – and have some options up your sleeve. I didn’t do the DHA PowerPoint: my co-author did, for which I am deeply grateful. It can all be his fault.

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Talking Orchil

Canterbury graveyard, 1960s sketchbook

Lichens in a Canterbury graveyard: from my 1960s sketchbook

In my last post I started to write about orchil, and how I became fascinated by its story through my researches on an eighteenth / nineteenth century Wood & Bedford / Yorkshire Chemicals archive.

To start at the beginning, orchil (pronounced or-kil) comes from lichens. It has been used for millennia to dye wool and silk a purple colour. There is some confusion over ancient recipes for purple. It isn’t always possible to decipher which recipes refer to lichen and which to shellfish dyes. Both dyestuffs produce a remarkably similar colour, were to be found in the same areas (e.g. the Mediterranean coast) and descriptions of lichen are often a little vague. For instance, dyestuff might be referred to as a plant, or a moss, or a seaweed.

There is evidence (Pliny, Theophrastus, Dioscorides) that orchil was used in conjunction with shellfish purple and it’s a ready assumption that this was done  to defraud – which of course it may have been. The processing of orchil would have been significantly cheaper than for shellfish dye. But the combination was also undertaken to produce a legitimately cheaper alternative to pure shellfish-dyed cloth. Nevertheless, orchil and shellfish-dyed cloth seems regarded with disdain because of the great and unique reputation of shellfish purple, and orchil’s tendency to fade.

The beauty of fresh orchil on woollen yarn

The beauty of fresh orchil on woollen yarn

Orchil dye is extremely beautiful in its first, fresh bloom of colour but it normally proceeds to fade fast. It is therefore interesting to read a 2012 paper (link below) in which Casselman and Terada demonstrated that a combination of orchil and shellfish dye may in certain circumstances, stabilise the orchil. They also reported that the  use of orchil as a base dye would to some extent neutralise the intensely unpleasant odour of shellfish-dyed cloth. Those facts cast an entirely different light on the historic combination of orchil and shellfish dye.

It occurs to me that in more recent days, far from being ‘poor man’s purple’, orchil could have been considered a great luxury. If you could afford the rich glories of orchil-dyed silk, and these would be obvious to all by the colour, it might indicate one’s financial indifference to fading and the realities of a soon-spoiled garment.

Dye lichens

Not all lichens will dye, not all dye lichens will make orchil. Orchil-producing lichens (and there are innumerable species) contain precursors of the dye and to make this available the dyestuff must be crushed in ammonia or stale urine and water and then kept well-oxygenated. It undergoes a type of fermentation, and the purple colour develops over several weeks.

Orchil is very sensitive to changes in pH and by adjusting vat strength and acidity, a wide variety of colours can be achieved, ranging from browny reds to reds, pinks and purples.

Crotal / crottles

There are lichens that will dye rusty reds, browns and golds. They are often referred to as ‘crotal’, (a Gaelic word) or crottle, lichen. These require no fermentation and are normally boiled up together with fibre, yarn or cloth. They have been in traditional use in Scotland for centuries and the warm, earthy smell of crotal-dyed yarn is also a moth deterrent. But crotals are not orchils!


Neither orchil nor crotal requires a mordant although some historical recipes recommend an alum mordant for orchil.


The Wood & Bedford Orchil Story

I found a vast number of items in the archive which related to the nineteenth and twentieth century trade in orchil. A couple of them can be seen in the previous post. The records defined several sources of orchil lichen. Around 1830 these included Scandinavia, Sardinia, the Azores, Madeira,  the Canary Islands and Cape Verde. Political changes and colonial interests affected trading in the later 1800s, as did the slave trade and, eventually, its abolition. A picture emerged of a voracious trade that reached an industrial and even global scale by the mid nineteenth century. There is a certain irony in the fact that stocks of what, in effect, is a non-renewable product were saved by the synthesis of mauveine by Perkin in 1856. The demand for lichen then dropped. Nevertheless, Wood & Bedford,  later the Yorkshire Dyeware and Chemical Company, continued to buy and process orchil lichen well into the twentieth century. I understand that the last unused lichen stocks went to Johnsons of Hendon who presumably used lichen to make their indicator papers.

Lichen ethics

You will see that I have learned to make orchil and to dye samples for research purposes but I don’t use it in my studio work. You can read some of my thoughts on lichen use here. I am extremely grateful to all those who taught me about making orchil and how to dye with it.


How do you pronounce lichens? I say it to rhyme with kitchens. Most people and academics (ok, sorry, academics are also people)  say ‘likens’. The OED pronunciation makes it official: you can say it either way:
/ˈlʌɪk(ə)n, ˈlɪtʃ(ə)n/


The Politics of Purple: Dyes from Shellfish and Lichens Karen Diadick Casselman and Takako Terada

Natural Dyes: Sources, Tradition, Technology and Science; Dominique Cardon, Archetype Publications

The Colourful Past: Origins, Chemistry and Identification of Natural Dyestuffs; Judith H. Hofenk de Graaff, Archetype Publications

Lichen Dyes: The New Sourcebook and Craft of the Dyer by Karen Diadick / Leigh Casselman