Human beings have an insatiable appetite for colour, but the everyday gaudiness of our world is modern. We can dress as showily as birds (including crows – 70 to 90 per cent of clothes are dyed black) because we have found ways to stain pale yarns in strong colours. During the last 150 years the whole spectrum has come to be cheaply available, as it has become possible to synthesise dyes which previously had to be extracted from plants and animals.
Dyes are tricky. Unlike paint – pigment carried in suspension in a medium which sticks it to a surface – dyes must adhere to the substrate molecule by molecule. Some do it directly; other dye/fabric combinations need an intermediary – a mordant – in which to dissolve the dye to make it bite. Consider what used to have to be done in order to dye with indigo (the process has certain things in common with brewing). Leaves from one of the plant species which contain indican, the precursor of the dye, are steeped in a vat. Lime (or urine, or wood ash water – something to keep the contents alkaline) is added. Fermentation turns indican into indoxyl. Cloth can be dyed directly in the fermentation vat, in which case the indoxyl is oxidised to become indigo when the steeped cloth is exposed to the air, and the liquid which looks greenish yellow in the vat turns blue.
If the dye is to be stored, however, it must be processed further. The fermented liquid is run into another vat and aerated by stirring. Before machinery took over, large-scale indigo producers had slaves or coerced labourers march up and down in the tank of caustic, evil smelling oxidising indigo. It was a horrid job. At the right moment (knowing when required skill) stirring was stopped and the indigo which had been precipitated was harvested as a paste from the bottom of the vat. This, dried and prepared as balls or cakes, was the exportable product.
To use it, the dyer ground up the ball of dye and dissolved it in a vat of alkali. This reduced the indigo to leuco-indigo. The solution did its magic as before. The cloth when taken from the vat of greenish dye turned blue on exposure to the air.
In Indigo, Jenny Balfour-Paul glosses these processes scientifically. The first surprise is that indigo, the dye of dyes, is in some ways more like a pigment. It needs no mordant, even on non-absorbent fabrics like cotton. Tiny particles, not individual molecules, adhere to the fibres, which is why it rubs, giving stonewashed jeans their pale, worn look. In some parts of the Arab world, rub-off onto the skin is thought to be good for the complexion.
Balfour-Paul has grown indigo and sought out dyers in Europe, Africa and Asia. Her pictures show the materials, from live plants to vats and balls of dried indigo, and the processes of dipping, decorating (often by tie-dyeing, keeping parts of the fabric undyed with resists or knots) and glazing with mallets and rollers. She shows how the indigo spectrum runs from pale blue to near-black (although it is really broader than that – an Indian dye book describes colours from ‘regal purple’ to ‘light canary’, all made in Gujarat from indigo combinations).
The only way really to understand a craft is to do it, or at least see it done. The pictures in Indigo do all a book can to describe the processes of craft dyeing. They are regionally disparate but essentially timeless. The indigo trade, on the other hand, has a history. In medieval Europe, woad merchants (the colouring matter is chemically identical with indigo) were obviously rich: you only have to look at their fine houses in the old parts of Toulouse. Indigo was not as valuable as shellfish purple (about ten thousand creatures had to be killed to obtain a gramme of that dye; even today ‘the people of Oaxaca in Mexico will taste purple-dyed fabric to see if they are being palmed off with an indigo and red fake’) but as trade developed in the 17th century, indigo was up there with pepper and cloves in volume and value. Stronger in colour, and cheaper, imported tropical indigo eventually destroyed the European woad industry – just as the Indian indigo trade was to be ruined by synthetic indigo in the 19th and 20th centuries. Woad manufacture was only revived when supply was cut off in France during the Napoleonic wars; and, similarly, the unavailability of German synthetic indigo during the First World War brought passing prosperity to Indian growers.
Indigo was an ideal plantation crop. The Dutch in the East Indies, the English in India and the Spanish, Portuguese, French and English in Africa, Central America and the Caribbean developed global patterns of trade which exploited labour in much nastier ways than the sport-shoe or garment industries do today. There were technological improvements – for example, mechanical methods of aeration – but a crop which impoverished peasant labourers by using land they could have devoted to food production and which, in any case, brought them small profit provoked powerful resentments. Gandhi’s first act of peaceful civil disobedience in India took place in 1917, when he went to northern Bihar, the scene of rioting fifty years earlier, to investigate abuses on the indigo plantations.
Organic chemistry would, as it turned out, change indigo production so radically that the anxieties of growers and the anger of workers would become irrelevant. In 1897, forty years after William Perkin stumbled on the first synthetic aniline dye – mauve – researchers at BASF finally synthesised indigo. The work had taken years and cost eighteen million gold marks – more than the capital value of the company.
Experiments in organic chemistry are not so very different in their methods from traditional dye-making. Both involve the careful management of processes like digestion, distillation and precipitation in an environment in which temperature, pressure and acidity are both moderate and well controlled. What is different is the kind of thinking involved. Balfour-Paul is very good at giving an idea of how dyers think; Simon Garfield is not so successful with his organic chemists.
Mauve is about William Perkin, and about what followed from his discovery. As it is possible, at a pinch, to trace the achievements of all the chemical industries which once used coal and now use oil as a raw material back to the work he did as an 18-year-old student, he can be thought of as standing more or less at the beginning of the pharmaceutical and plastics industries. As dyes bond selectively with all sorts of organic substances, not just with fibres in textiles, they are wonderful tools for microbiology, differentially staining specific parts of cells, distinguishing one kind of bacterium from another or tagging genetic material. It is not surprising that the industrial chemists who made fortunes for dye-makers went on to make even greater ones in pharmaceuticals – Hoechst and Bayer began as dye makers – and it is possible to credit Perkin with a distant contribution to modern cell biology.
This broad stream of organic chemistry is what eulogists in mauve bow ties pointed to at the celebrations to mark the 50th anniversary of Perkin’s discovery – Garfield gives a great deal of space to the junketing which went on. Perkin’s life must have been a difficult one to write: a modest, amiable man who made his great breakthrough when he was 18, sold up before he was forty and settled down to an uneventful life of useful work in chemistry and the support of local charities.
It has been said that science owes more to the steam engine than the steam engine does to science; by the time Perkin was at work things had changed. The chemical industry could never have been built by practical men using ingenuity and common sense alone. In that sense Perkin’s story is different from those of the often self-educated inventors who Samuel Smiles celebrated in the Lives of the Engineers. But Smiles would have understood and appreciated Perkin’s tenacity and competence, his skill as a chemical engineer and his abilities as a businessman, the determination with which he transformed a piece of laboratory science into an industrial process. There were brief but real struggles: to raise money for a factory (in the end his father chipped in with his life savings), to find a place to build it (a widow in Harrow sold them a plot on condition they did not built a public house to compete with the one she ran), to find markets (the dye industry could be conservative), to get hold of raw materials, to defend patents and design plants – any of these could have been used as an excuse for giving up.
Perkin showed he could make a business work. What he – and British business – did not have was what it took to build a large-scale chemical industry on the German model. One reason Perkin retired so early was that he could not match his Continental competitors. It was not just that projects like synthesising indigo needed investment on a very large scale; as important was the need for whole teams of scientists, not just a few bright individuals. An educated workforce of that size was not available in 19th-century Britain. Perkin himself was a product of the Royal College of Chemistry, an early attempt to give British industry scientific muscle and breed British chemists. It was founded in 1845, the result of a private subscription set up by Sir James Clark (the Queen’s physician), Michael Faraday and the Prince Consort. Its first director, recruited from Germany, was August Wilhelm von Hofmann. Perkin became a student there in 1853. Hofmann was already investigating coal-tar derivatives, aniline in particular. He had also speculated that it might be possible to synthesise quinine. That was the task Perkin set himself in the 1856 Easter holidays. His home laboratory was primitive but he was methodical and curious. Investigating one of the residues resulting from his failed attempt to synthesise quinine, he found it had an intense purple colour. Others might have regarded it as a mere curiosity – it was not the first coloured residue to turn up in chemical experiments with coal tar. Perkin saw commercial potential. Hofmann was ambivalent: he was losing one of his most promising pupils, and losing him not to industrial chemistry but to entrepreneurship.
Indigo is a staple which has coloured the clothes of whole populations and generations; mauve was a fashion colour. When Perkin discovered his dye it was a novelty – there were shades like it, but none which dyed so much so well. Queen Victoria wore mauve to her daughter’s wedding; Eugénie, Empress of France, took a liking to it. Punch made jokes about it. The fashion passed as fashions will; it was the discovery that naturally occurring organic substances could be synthesised – and new ones invented – which mattered. Garfield dips into some of these stories: quinine, for example, and coumarin, the first scent Perkin synthesised. The field is very wide, and he wanders over it without much sense of direction. There are asides on what a modern colour consultant to the fashion industry does, on the economic effects of malaria and on modern revivals of woad production. They are interesting enough subjects which doubtless deserve their own space, but they do not make up for a lack of what might have held a book about Perkin together – a sense of what it is like to do chemistry and how chemists think.
I can see that the task is difficult. Chemistry has not produced its equivalent of Gould or Feynman to make popular science of it (or, if it has, I have failed to find them). The only writer I know who makes chemistry intellectually exciting for the lay reader is Primo Levi, but, although he writes wonderfully about learning chemistry and the routine work of industrial analysis, he has no reason to describe the history of chemical innovation.
Garfield tries analogies – he drops in a recipe for Nesselrode pudding, for example. One gets the point – doing organic chemistry is a bit like cooking – but it was an odd recipe to pick on, chosen, it would seem, because Proust mentions it. The instructions suggest that it is not a recipe (like that for mayonnaise) which requires delicate control of materials, temperatures and methods if disaster (curdling, say) is to be avoided.
When philosophers try to separate the accidents of the physical world from its essences the first thing they discard is colour. We know it is unstable from one viewer to the next (the colour blind, as well as the birds and the bees prove that). It is easy to see colour as a commentary on a thing rather than as part of it.
That is, perhaps, why dyes have mattered so much. They give information without affecting shape. The colours of their jerseys distinguish members of opposing teams. The gender of birds and the status of academics are signalled by the colour of their plumage. Dyes allow the liveries of servants, the uniforms of armies, the bishop’s purple socks, the cardinal’s scarlet hat and the politician’s tie to announce affiliations. Colour is not a precise language – it is black for mourning in some societies and white in others – but there are enough associations (warm reds, ice greens) for it to have a poetry of association.
Black dyes have always been in demand. They are as close as you can get to no colour at all. The lawyer’s gown, the dark business suit and the fashion editor’s little black dress are ways of keeping mum; nothing makes the power that dyed cloth has to tell tales so clear as the need many feel to say nothing colourful at all.