Colours from Nature
For most of human history, every coloured garment owed its hue to something that had once been alive. Roots, leaves, bark, berries, insects and even shellfish were boiled, crushed or fermented to release their pigments, and the resulting dyes were among the most valuable goods in early trade. A length of deep red cloth could cost more than a labourer earned in several months, largely because the raw materials were scarce and the process of fixing a colour to a fibre was slow and uncertain. Dyers guarded their recipes closely, often passing them down within a single family for generations and refusing to reveal them even to apprentices from outside the household.
The basic chemistry of natural dyeing has changed little over the centuries. Most plant colours will not bond to fibres on their own; they simply wash out after one or two cleanings. To prevent this, dyers first treat the yarn with a mordant, a metallic salt that attaches itself to the fibre and then grips the dye molecules. The most widely used mordant is alum, a mineral compound that keeps colours bright and clear. Iron, by contrast, tends to darken and dull them, which is why a single plant can yield a surprising range of shades: the same bath of onion skins might produce a warm gold on wool treated with alum and a deep olive on wool treated with iron. Wool and silk, which are made of protein, take up natural dyes far more readily than cotton and linen, which are made of cellulose and usually need several extra stages of preparation.
Some colours have always been harder to obtain than others. Yellow was the easiest, since dozens of common plants contain yellow pigments. Blue, on the other hand, came almost entirely from a small group of plants that produce indigo. Indigo is unusual because it does not dissolve in water. The leaves must first be soaked and fermented, and the dye bath kept as free of oxygen as possible; when cloth is lifted out of the bath, it emerges a pale yellow-green and turns blue only as it meets the air. Watching this transformation remains, for many dyers, the most magical moment of the craft. Reds came from the roots of madder or from tiny insects that live on certain cactus plants, and the insects in particular were so highly prized that merchants traded them by weight, much as they traded silver.
This entire system collapsed with remarkable speed in the second half of the nineteenth century. Chemists working with coal tar, a sticky waste product of the gas industry, found that it could be turned into brilliant dyes that were cheap, consistent and easy to apply. Within a few decades synthetic colours had replaced plant dyes in almost every textile mill, and farmers who had grown madder or indigo for centuries discovered that their crops had lost nearly all their value. Today, the overwhelming majority of the world's fabrics are coloured with synthetic dyes, and many people have never worn a garment dyed in any other way.
Their success, however, has come at a cost. Dyeing is now regarded as one of the most polluting stages of clothing manufacture. Enormous quantities of water are needed to rinse fabrics, and in regions where regulation is weak, untreated wastewater containing dyes and heavy metals is released directly into rivers. Residents of some factory districts claim that they can tell which colour is fashionable each season simply by looking at the water flowing past their homes. Concerns of this kind have encouraged a number of designers and shoppers to look again at the methods their ancestors used.
Supporters of plant dyes argue that they offer a genuinely sustainable alternative, but the picture is more complicated than it first appears. Natural dyes are biodegradable, yet the substances used with them are not always harmless: some traditional mordants, such as chrome and copper, are toxic and are now avoided by most responsible dyers. Growing dye plants on a large scale would also occupy farmland that might otherwise produce food. In addition, natural colours are notoriously difficult to reproduce exactly. A fashion company ordering ten thousand shirts expects every one of them to match, whereas the result of a natural dye bath can vary with the season in which the plants were harvested, the minerals in the local water and even the temperature of the workshop.
For these reasons, few experts believe that plant dyes will replace synthetic ones in mass production. Instead, they are carving out a modest but valuable niche. Small studios sell hand-dyed yarns to knitters who appreciate their subtle variations of tone, and some researchers are investigating ways of extracting colour from food waste, such as avocado stones and pomegranate peel, which would avoid the need to grow crops specially for dyeing. Others are experimenting with bacteria that produce pigments directly onto fabric, using a fraction of the water required by conventional methods. Whether or not these experiments succeed commercially, they have revived interest in an ancient craft, and in the question of what our clothes really cost.
