The Sainsbury Wing is looking different. The walls are almost black and there are backlit photographs of vibrant explosions and placards with neon lettering. Is this the right place? Have I accidently come to the Science Museum? For an art show, there are a lot of mineral samples in cabinets and apothecary’s mounds of colourful powders. This is not South Kensington, but for its summer show, the National Gallery has turned to science or, more accurately, chemistry. Making Colour, which runs until 7 September, is about just that, and in a collaboration between curators and the gallery’s science department, who have been given a rare pass out of their labs and into the exhibition space, the gallery’s paintings are being taken back to their elements. If the curators had to dust off their GCSE chemistry while putting together this display, so will you, with rocks and minerals (remember, they are different) and old friends from the periodic table, cropping up throughout the exhibition.
The show has been arranged anti-clockwise around the colour wheel, from blue to purple. A bonus room at the end looks at gold and silver which, with no place on the spectrum of white light, are not strictly colours; but try telling that to an International Gothic or Renaissance painter. It was Isaac Newton who devised the first colour wheel in the 1660s, although his circle was not that colourful, and so it is a later version by Moses Harris which the National Gallery has used to demonstrate the concept. But well before the wheel was developed and theorised, artists were intuitively following its principles. The adage goes, “blue and green should never be seen without a colour in between”, and perhaps there is some scientific truth behind this. The colours are next to each other on the circle, and when painted alongside in a picture, the effect is muted. Put blue next to its opposite number on the wheel, however, and the result is intense. Annibale Carracci, himself an early theoriser on colour, recognised this, and Saint Peter with his blue and yellow robes in Christ appearing to Saint Peter on the Appian Way (1601-2), has reaped the rewards. By the nineteenth century, intuition was backed up by scientific theory, and Chevreul’s 1839 Principles of Harmony and Contrast of Colours, which was the first book to record the enhancing effects of opposite colours, is seen in action in Van Gogh’s Two Crabs (1889) or Renoir’s The Skiff (1875).
Today’s artists have an easy ride when it comes to getting hold of paint. In the late fourteenth century, when Giovanni da Milano was painting his The Virgin (1365), the blue deemed appropriate for Mary’s robes – which as a primary colour could not be mixed from other shades – was produced using extracted pigment from the rock Lapis lazuli. But the rock was available only from a source in Northern Afghanistan; the process of extraction, which involved grinding, mixing, kneading and siphoning, was laborious; and the route to Italy, long. It is no surprise, therefore, that the pigment was more expensive than gold. And although the earlier painters had no choice, with cheaper alternatives becoming available only later, Lapis lazuli was the Rolls Royce of blues: Milano’s Virgin’s dress does not look 635 years old, and Sassoferrato’s praying Virgin (The Virgin in Prayer (1640-50)) is resplendent in her deep blue gown. Several pictures along, no wonder Albrecht Altdorfer’s Virgin, wearing mere azurite, looks so unhappy (Christ Taking Leave of his Mother (1520)).
The Milano robe has been painted with an egg-tempera based mix which creates a matte effect; Sassoferrato’s robe, on the other hand, has a translucent quality, which comes from mixing the pigment with oil. The same contrasts are seen when artists worked with green paints, which could be made glossy or dull, according to the mix. Hans Memling’s Virgin (Virgin and Child (c.1475)), whose flesh-tones are built up using an oil and verdigris green composition, exudes a healthy glow; Ghirlandaio’s Mary (The Virgin and Child with Saint John (1490-1500)), with her egg tempura foundation, has gone for the powder-puff matte look.
She does seem a bit sea sick, however, and over time the green undertones of her flesh have surfaced. These greens were originally added to define her features and help her with her bone structure, but as the paint surface has worn away, she has been left looking peaky. Paint stability may have been of less concern to artists while they were working – it takes time for things to deteriorate – but is of great interest to today’s conservators. Lapis lazuli pigments are as blue now as they were when first extracted from rocks hundreds of years ago. Smalt, a blue created from cobalt glass and used during the sixteenth and seventeenth centuries as a cheaper and more readily available alternative to Lapis lazuli, has done less well over time. In The Marquise de Seignelay and Two of her Sons (1691), Pierre Mignard shows Louis XIV’s wife, posing as the mythological figure Thetis, dressed in a vibrant Lapis lazuli blue cloak. The smalt which Mignard used to paint the sky, however, seems to have affected the weather, which is now looking overcast and threatening. The smalt paint has discoloured over the years, most likely because of a reaction between the cobalt glass and the oil base of the paint, dulling its effect and making a blue sky turn grey. It is an unwelcome chemical reaction which has also caused so much foliage, presumably luscious green during the fifteenth and sixteenth centuries, to turn brown. Antonio del Pollaiuolo did not intend his laurel trees to look rotten when he painted Apollo and Daphne (1470-80); but the pine resin and oil of the green paint have reacted with the copper-based verdigris pigment resulting in the brown hue.
Technical developments as well as chance discoveries – the Prussian Blue scarf of Gainsborough’s Mrs Siddons (1785) was the accidental creation of a German paint maker in 1718 – changed the paints which were available to artists. But there is also a continuity in materials. Masaccio in the early fifteenth century and Degas in the late nineteenth century both used vermilion based red paints, and the yellows favoured by the della Robbia dynasty for their terracotta creations in the 1500s contained the same basic ingredients as the yellow of Gainsborough’s daughter as she chases her butterfly (The Painter’s Daughters chasing a Butterfly (1756)).
Vermilion comes from the mineral cinnabar, but depending on the red desired, various types of pigment were available: in his La Coiffure (c.1896), Degas uses red lead, Indian red, vermilion or red lake, according to the level of intensity that he required. Masaccio used a similar technique, and dresses Saint Jerome in bright cardinal-red vermilion, while Saint John sports the more moderate red lake. Red lake itself is derived from a dye rather than a mineral, rock or chemical element, and in a line up worthy of Hogwarts potions lab, there are various sources of the pigment on display, including kermes, stick lac, cochineal and madder. Creepy names and weird substances, but it is the orange created from the arsenic containing mineral realgar, used by Rachel Ruysch for her vase in Flowers in a Vase (1685), which is most alarming. And if you are beginning to think that the names of these pigment sources are as exotic and catchy as the colours themselves, this is not always the case: the colour of Gainsborough’s daughter’s dress is known as “lead-tin yellow type one”, a name that is unlikely to appear on Farrow & Ball’s paint chart any time soon.
At the end of the exhibition, the curators have brought in another collaborator, a neuroscientist from Newcastle University and have together produced an interactive experiment, examining human perceptions of colour and the effect of lighting on these perceptions. There is not always time for the film offerings at the ends of exhibitions, but this is one to watch. In the cinema, each viewer is given an “ask the audience” style clicker to record reactions to various experiments about how the eye and the brain respond to colour, including a mind-boggling moment when the brain is tricked into thinking a black and white picture is in fact colour. It is fun and interesting and at the end of the exhibition’s run, the scientists will collect the data and, we assume, write something clever. But watch out, you will need to be quick off the mark with those clickers – the kids will be fine at this – with one journalist, who shall remain unnamed, finding the experience quite beyond her capabilities.
The National Gallery needed to make this exhibition, based around its own collection, a good’un, with the criticism of this year’s Strange Beauty and last summer’s Vermeer and Music, still ringing in its ears. Because if it is not top-notch, and if it does not provide something high above what could be got from a regular visit to the gallery, exhibitions which charge visitors to see paintings which they might otherwise see for nothing, come in for a bashing. But there is no danger of that in this tightly organised and visually spectacular exhibition, which manages to bring art to the scientists and science to the artists.