Color before chemistry
Until the middle of the 1800s, every dye came from nature. Blue came from woad and later indigo, red from madder roots or from insects such as cochineal, and yellows from plants like weld. Purple was the hardest. The ancient purple of the Mediterranean, often called Tyrian purple, came from sea snails and was extremely costly, and many later purples were weaker and faded.
Natural dyeing was also a craft of long preparation. Many dyes needed mordants, metal salts that helped the color bind to the fiber, and the results varied with water, season and the skill of the dyer. As machines made cloth faster and cheaper, the supply of reliable colors became a limiting factor.
The accident of 1856
The story usually starts with William Henry Perkin, an English student at the Royal College of Chemistry in London. In 1856, when he was about 18, he was working at home during a holiday on a problem set by his teacher, August Wilhelm Hofmann: whether quinine, the anti-malaria drug, might be made artificially. Quinine was valuable and came from tree bark, so the goal made sense. The chemistry of the time, however, was not yet advanced enough to make it.
In one experiment Perkin oxidized aniline, a chemical derived from coal tar. Instead of quinine, he got a dark sludge. While cleaning the flask with alcohol, he noticed that it dissolved to a purple solution, and he found that it would dye silk. He had made the first commercially successful synthetic dye, which he patented in 1856. The color was soon called mauve, after the French word for the mallow flower.
Perkin was young and not an experienced businessman, but with his father and brother he built a factory at Greenford, near London, to make the dye in quantity. That involved solving real manufacturing problems, because aniline had never been produced at large scale. Mauve became fashionable in the early 1860s, to the point that the period is sometimes called the “mauve decade,” though that phrase is also used loosely.
Coal tar becomes a source of color
Coal tar was a messy by-product of making coal gas for lighting and, later, coke fuel for the iron industry. Chemists found that it contained a wealth of compounds, such as benzene and aniline, that could be turned into new substances. Other researchers quickly followed Perkin’s lead:
- Magenta (fuchsine), a vivid red-purple, appeared in 1859.
- Alizarin, the main coloring matter in madder, was synthesized in 1868 by Carl Graebe and Carl Liebermann in Germany, and Perkin found a similar route at nearly the same time. Because it could be made cheaply, it badly hurt the madder-growing trade.
- Synthetic indigo came later. Adolf von Baeyer worked out its structure and a route to make it in the 1870s and 1880s, and a commercially competitive process was developed by German companies in the 1890s. Natural indigo farming, which had been a major colonial crop, declined sharply as a result.
The details differ in sources, and credit for particular steps is sometimes disputed, but the overall direction is clear: chemistry replaced agriculture as the source of most dyes.
A new kind of industry
Germany became especially strong in this field, with companies that employed many trained chemists and ran organized research laboratories. That model, in which scientists work in an industrial setting to produce new compounds, was an important development in industrial chemistry. Firms that began by making dyes later expanded into medicines, photographic chemicals, explosives and plastics, though the exact paths varied by company.
Dye chemistry also fed other fields. Chemical stains made it easier to see cells and microbes under the microscope, and such staining played a role in the research behind germ theory and in later medical diagnosis. Some of the same chemical ideas contributed to early drug development.
Costs and trade-offs
Synthetic dyes brought brighter, cheaper and more consistent color, and ordinary people could wear shades once reserved for the wealthy. They also created problems. Early dyes sometimes contained toxic substances, such as arsenic compounds used in their manufacture. Dye plants produced waste that polluted rivers, and dye-house workers were exposed to chemicals that were later linked to health risks. Modern regulation covers many of these issues, though wastewater from textile dyeing remains an environmental concern in some regions.
The shift also hit traditional growers and dyers, who saw demand collapse within a generation. Today some craftspeople and small producers use natural dyes again for their look and heritage, but the large majority of cloth is colored with synthetic dyes.