The Origin of Colours - A study on the history of pigments

Natural pigments: it all starts with red

To our knowledge, red ochre is the first colour pigment ever used by man. This clay powder, naturally tinged with hematite, is still used as a pigment today. It is the first of many reds discovered over time by cultures around the world. For example, red pig-ments have been obtained from insects for thousands of years, specifically from the large family of cochineal beetles (coccoidea). These types of red are called red lakes. The name comes from the use of gum lac, a resinous component created by the laccifer lacca in India, which is used as a pigment. Unlike their Indian cousins, which manage to survive the process, other cochineal insects have been pressed to create red pig-ments in many parts of the world. In South America it gave rise to carmine red, in Eu-rope the kermes lake was created and flourished until the 17th century. These natural pigments are still used today and are so harmless that they are even found in food as E120. Another natural origin of pigments is found in plants, like with the colour Indi-go, first found in Peru in examples from 6000 BC.  However, paradoxically, most 'nat-ural' pigments have a long history of toxicity.

Probably one of the most common, vermilion red was obtained from cinnabar, a min-eral derived from mercury. The use of vermilion dates back to 5000 BC in China, Spain and Turkey, and it was later also used by the Olmec, Mayan and Roman civilisa-tions. Also of mineral origin, lead red was used in ancient Greece and later by the Ro-mans. Created by burning pieces of white lead, the red pigment, also called minium, was used to decorate books in the Middle Ages and gave its name to the art of minia-ture painting. There is no need to explain the toxicity of pigments derived from lead and mercury. Another example is Orpiment, derived from arsenic, which was used in ancient Egypt as an alternative to yellow ochre.

The history of colour challenges our view of what is natural and what is not. It is inter-esting to see how experimentation has continued for millennia, even in strange ways. The British painter William Turner used a water-based paint called Indian Yellow, made from the urine of cows fed on mangoes. It is also fascinating to see how certain colours, because they were difficult to produce, soon became a display of power. We immediately think of ultramarine blue, made from the grinding of lapis lazuli, and used in Renaissance commissioned paintings as a display of wealth. Another example is Tyrian purple, a colour used by Greek and Roman nobility because of its rarity; the colour purple was extracted by hand from sea snails, with ten thousand snails providing just over one gram of pure dye.

Synthetic pigments: the chemical revolution

Contrary to what one might think, synthetic pigments are not a modern concept. Egyp-tian blue, created using a formula that has now disappeared, is known to have been made as early as 3250 BC. The Chinese have used oxidation to create colours in porce-lain for thousands of years. But it is true that with the creation of Prussian blue, around 1706 by the paint manufacturer Diesbach, the creation of synthetic pigments experienced a new momentum.

Research has sometimes led to hazardous results, such as Scheele's green, a pigment mixed with arsenic, widely used in the 19th century, which is said to have poisoned Napoleon Bonaparte, whose house in exile was decorated with wallpaper of this toxic colour. Paris green, also composed of copper and arsenic, is said to have caused Cézanne's diabetes and Monet's blindness. However, synthetic pigments have often happily replaced "natural" colours. Zinc white is one of them. Before the development of zinc oxide, white lead was commonly used by artists. Sometimes less toxic, always less expensive, synthetic pigments allowed artists to experiment, as with the creation of chrome yellow in the 1820s or French ultramarine by Jean-Baptiste Guimet in 1828. Identical in colour to the lapis lazuli-based ultramarine pigment, this new colour was both much more accessible and easier to use.

However, the real chemical colour revolution came later on, with alizarin, which was the first colour to be fully synthesised. While alzarin was originally extracted from madder wood, two 19th century chemists, Carl Graebe and Carl Liebermann, found a way to reproduce the molecule responsible for its colour. The two chemists worked for a then still small German company, Bayer. With their discovery, they opened the way to the wide range of colours that have become a common thing today.