Three colours: Red

This is the first of three essays on colours that were to be included in the catalogue for an exhibition at the Musé d'Orsay in Paris this year, which has been cancelled. So I'm putting them here for your delectation. Each essay focuses on the pigments developed and used through time for one of the primary colours.

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One hundred thousand years ago, the last Ice Age covered much of northern Europe with glaciers several kilometres thick. Small groups of Homo sapiens coexisted with other, now extinct human ancestors: Neanderthals and Denisovans. Life was nasty, brutish and short. Yet in a cave in what is today South Africa, humans found the time and inclination to mix red paint.

Their tools have been found in Blombos Cave on the Southern Cape coast: grindstones and hammer-stones for crushing the pigment, and abalone shells for mixing the powder with animal fat and urine to make a paint that would be used to decorate bodies, animal skins and perhaps cave walls. The red colour was made from ochre, a natural, soft, iron-rich mineral chemically similar to rust.


A piece of engraved ochre from Blombos cave in South Africa.

The evolution of complex ways of thinking and socializing seems only to have happened fifty thousand years later – and yet even at the dawn of human culture it seems that the urge to adorn our surroundings and ourselves with colour was deeply felt. It was done in the colours of nature: black charcoal, white chalk and ground bone, and the brownish-red of ochre. It’s no wonder that a word for “red” seems to be one of the earliest colour words to appear in languages across the globe, after those for black and white. The cave paintings made 15-35 millennia ago in Chauvet, Lascaux and Altamira attest to the genuine artistry that early humans achieved.

Red ochre is still on the artist’s palette today: a “dirty” red, some might say, but an honest, humble one, and cheap too. It’s iron that gives the mineral this hue. Like many metals when chemically combined with other elements, it absorbs light within a characteristic band of the visible spectrum, soaking up the blues and greens but reflecting the reds. That red is purer in the colour of blood, where an iron atom sits at the heart of the protein haemoglobin and ferries oxygen around our bodies. The bloody hue is reflected in the technical name for ochre-like minerals: haematite, literally “blood-stone”, which is iron oxide.

During the Industrial Revolution, chemists perfected a method for making iron oxide artificially, so that the red colour could be more precisely controlled. It was an offshoot of the manufacture of sulphuric acid, an important ingredient for textile bleaching. This red substance was sold to artists as “Mars red”, an echo of the old alchemical term for iron compounds. The planet Mars was long associated with redness. It has that hue even to the naked eye, for its surface is covered with iron oxide minerals.

But the classic red pigments of the artists don’t rely on iron minerals, the hue of which is not the glorious red of a sunset, or indeed of blood, but of the earth. For many centuries, the primary red of the palette came from the compounds of two other metals: lead and mercury.

Lead is something of a chameleon metal. By combining the raw metal with various other substances – vinegar, carbon dioxide, air – alchemists and artisans knew since the time of the ancient Egyptians how to obtain white, yellow and red materials. Red lead was the finest of these colours, made by heating “white lead” in air. It was known too in ancient China from at least the fifth century BCE. Roman and Greek painters used it, although the Roman writer Pliny in the first century AD was wary of artists who used bright colours like this too lavishly – the sober artist, he insisted, deployed a more muted palette, with reds of ochre.

To Pliny, any bright red was called minium, and red lead was a slightly second-rate version: minium secundarium. But by the Middle Ages minium had become more or less synonymous with red lead, which was used extensively in manuscript illumination. That art came to be described by the Latin verb miniare, “to paint in minium”, from which we get the term “miniature”: nothing to do, then, with the Latin minimus, “smallest”. The association today with a diminutive scale comes simply from the constraints of fitting a miniature on the page.


A miniature painted in red lead from c.1300.

Pliny’s best minium was a different red pigment, called cinnabar. This was a natural mineral: chemically, mercury sulphide. It was mined in the ancient world, partly for use as a red colorant but also because the liquid metal mercury could easily be extracted from it by heating. Mercury was thought to have almost miraculous properties: ancient Chinese alchemists in particular used it in medicines.

By the Middle Ages, alchemists and craftspeople knew how to make mercury sulphide artificially by combining liquid mercury and yellow, pungent sulphur (available naturally in mineral form) in a sealed vessel and heating them. This process, which was described in a craftsman’s manual of around 1122 by the German monk Theophilus, can give a finer quality of red pigment. It was a procedure of great interest to alchemists too, as the Arabic scholars of the eighth and ninth centuries had claimed that mercury and sulphur were the basic ingredients of all metals – so that combining them might be a route to making gold. Theophilus, however, had no such esoteric arts in mind; he just wanted a good red paint.

“Artificial cinnabar” became known by the name vermilion. The etymology is curious, and shows the confusing and treacherous flux of colour terms in an age when the hue of a substance seemed more significant than vague, pre-scientific notions of what its chemical identity was. It stems from the Latin vermiculum (“little worm”), since a bright red was once extracted from a species of crushed insect: not a paint pigment but a translucent dye of scarlet colour, arising from an organic (carbon-based) substance that the insects produce. Such dyes were also known as kermes, the etymological root of “crimson”. Because the insects that made it could be found on Mediterranean trees as clusters encrusted in a resin and resembling berries, the dyes might also be called granum, meaning grain. From this comes the term “ingrained”, implying a cloth dyed in grain: the dye was tenacious and did not wash out easily.


Vermilion is used abundantly in Masaccio’s Saints Jerome and John the Baptist (c.1428-9), in the National Gallery, London.

Vermilion is by no means the only close link between the reds of textile dyes and the reds of paint pigments. The former are translucent and dissolve in water, and are generally organic substances extracted from animals or plants – such as cochineal, an extract of New World beetles that became popular with cloth dyers in the sixteenth century. But paint pigments must be opaque and long-lasting, whereas dyes tended to fade as they were washed out or as sunlight broke down the delicate organic molecules.

Red dyes were associated with majesty, opulence, status and importance: they were the colours used for cardinals’ robes in the Middle Ages and Renaissance. Painters needed fine reds to render on board and canvas these dignitaries whose portraits they were increasingly commissioned to paint. Red lead and vermilion served well enough in the Middle Ages, but the increased demand for verisimilitude in the Renaissance highlighted the difference between the orange hue of the pigments and the crimson of the dyes.

One way to capture the quasi-purple magnificence of those dyes was to fix the colorant molecules onto solid, colourless particles that could be dried and mixed with oils like a regular pigment. This process involved some challenging chemistry, but even the ancient Egyptians knew how to do it. The basic idea is to precipitate a fine-grained white solid within a solution of the dye: the dye sticks to the particles, which dry to make a dark red powder. In the Middle Ages this process used the mineral alum, which can be converted to insoluble white aluminium hydroxide. The pigment made this way was called a lake, after the word (lac or lack) for a red resin exuded by insects indigenous to India and southeast Asia.

One of the best red lakes of the late Middle Ages and the Renaissance was made from the dye extracted from the root of the madder plant. As lake manufacture was perfected, artists such as Titan and Tintoretto began to use these pigments mixed with oils, giving a slightly translucent paint that they would apply in many layers for a deep wine-red tint or would wash over a blue to make purple. In this as in much else we can see the constant exchange in materials and knowhow between dyers and pigment-makers.


There is abundant, rich red lake in Titian’s Portrait of the Vendramin Family (1543-7).

A popular source of a luxurious, blood-red lakes in the late Middle Ages was the dye called cochineal, harvested in eastern Europe from a species of beetle that encrusted the perennial knawel plant with a resinous crust. The colour comes from organic compounds made by the insects themselves, which are killed, dried and crushed. According to one estimate, about 70,000 insects were needed to make one pound of this so-called carmine lake. The plant was harvested around midsummer, and if the crop failed, the price of carmine soared. After the discovery of the New World, however, cochineal for dyes and pigments gained a more reliable (if scarcely cheaper) source as an import from the Spanish colonies in the Americas.

The existence of strong red pigments was vital to the evolution of the palette. According to the art historian Daniel Thompson, the invention of a method to make synthetic vermilion transformed the nature of medieval art:
“No other scientific invention has had so great and lasting an effect upon painting practice as the invention of this colour… Given abundant vermilion, the standard of intensity in the painter’s palette automatically rises. Equally brilliant blues and greens and yellows were required to go with it… If the Middle Ages had not had this brilliant red, they could hardly have developed the standards of colouring which they upheld; and there would have been less use for the inventions of the other brilliant colours which came on the scene in and after the twelfth century.” (D. V. Thompson, The Materials and Techniques of Medieval Painting, p.106. Dover, New York, 1956.)

Aside from the creation of red lakes, rather little about the painter’s reds changed from the Middle Ages until modern times. The Impressionists in the late nineteenth century made avid use of the new yellows, oranges, greens, purples and blues that advances in chemistry had given them, yet their reds were not really any different to those of Raphael and Titian.

It wasn’t until the early twentieth century that a vibrant and reliable new red entered the repertoire. The discovery of the metal cadmium in 1817 immediately produced new yellow and orange pigments, but a deep red was made from this element only around the 1890s. The yellow and orange are both cadmium sulphide; but to get a red, some of the sulphur in this compound is replaced by the related element selenium. It wasn’t until 1910 that cadmium red became widely available as a commercial colour, and its production became more economical when the chemicals company Bayer modified the method in 1919.

Cadmium red is a rich, warm colour – it is arguably the painter’s favourite red, except for the price. That was certainly true for Henri Matisse, for who red held a special valence - as his interiors in La Desserte (aka The Red Room, 1908), Red Studio (1911) and Large Red Interior (1948) attest. Of the second of these, art critic John Russell said “It is a crucial moment in the history of painting: colour is on top, and making the most of it.”


Matisse’s The Red Studio (1911) is painted in cadmium red.

Colour is on top. That was that way in went in the twentieth century, from the strident chromatic statements of the Fauves (Matisse at their head) to the stark primaries of Ellsworth Kelly and the hypnotic maroon colour fields of Mark Rothko (whose experiments with new reds made from synthetic and fugitive dyes did not end well). Colour went from being the artist’s medium to being the subject. In that shifting of the agenda, red led the way.