Christ Glorified in the Court of Heaven: Central Predella Panel (1423-4) by Fra AngelicoThe National Gallery, London
'Christ Glorified in the Court of Heaven'
This is the central predella panel of an altarpiece (made of five panels) originally on the high altar of San Domenico, Fiesole. The panels were designed and largely executed, probably with workshop assistance, about 1423-4 by Fra Angelico, who was also a friar at San Domenico.
Other than the extensive use of gold, what is so striking about this painting is the range of colours, alternating between various shades of blue, green, pink and red.
The red hue in this painting is made with the red pigment vermilion, which, until modern times, was one of the most important pigments on the artist's palette.
Vermilion, along with two other red-coloured pigments, red lead and red lake, was widely used in Italy at the time that Fra Angelico was working. Artists often set different hues of red against one another, most notably when painting fabrics and drapery.
In an altarpiece by Nardo di Cione (pictured here), red lake was used for the pink cloak, red lead for the orange-red of the carpet and vermilion for the now discoloured but originally scarlet lining of the blue cloak.
Christ Glorified in the Court of Heaven: Central Predella Panel (1423-4) by Fra AngelicoThe National Gallery, London
In Fra Angelico’s painting red lake was also used in the pink draperies, as seen in the robe of the angel in the right foreground. Here, as in the painting by Nardo, these have faded because the red lake pigment is susceptible to light – it would originally have been a deeper colour.
To give a different, more scarlet red, vermilion has been used to depict the drapery of some of the other angels. It is also used for the tiny eye-catching bright red tongue of flame coming out of each angel’s head.
Vermilion was also often mixed with lead white to paint the flesh tones, as seen here throughout the panel. If we look closely, we can see the rosy cheeks of the angels, especially in those of the trumpet players, where a greater proportion of vermilion was used.
Pile of synthetic vermilion pigment (1999)The National Gallery, London
Vermilion - a synthetic pigment
Vermilion was an early synthetic pigment, produced in Europe from at least the 8th century. In Fra Angelico’s time, it was made by the so-called ‘dry’ process - usually by heating metallic mercury with sulphur in a glass jar or pot.
Cinnabar - a natural mineral
There is also a mercury sulphide mineral, called cinnabar, which is chemically the same as the synthetic pigment vermilion. Unlike vermilion, cinnabar is a naturally occuring mineral, however, only the best quality mineral would have been as bright as the synthetic pigment.
Cinnabar was used by the Romans for wall paintings – as shown in this fresco from the Villa Boscoreale, located in an area about a mile north of Pompeii, Italy. It was expensive as it was imported from the large mercury mines at Almadén in Spain.
Saint John the Baptist, Saint John the Evangelist (?) and Saint James (about 1363-5) by Nardo di CioneThe National Gallery, London
Vermilion and cinnabar can sometimes degrade, turning a dark grey colour – as seen here in the lining of the blue cloak in Nardo di Cione's 'Saint John the Baptist, Saint John the Evangelist (?) and Saint James'.
For a long time it has been known that they are unstable pigments. In his book, ‘Natural History’, the Roman scholar and natural philosopher Pliny the Elder (AD 23 – 79) stated that cinnabar was damaged by the action of sunlight.
Adoring Saints: Right Main Tier Panel (1407-9) by Lorenzo MonacoThe National Gallery, London
This degradation, or blackening, of vermilion is particularly visible in the red drapery depicted in the right main tier panel in another early Italian altarpiece from the National Gallery collection - the 'San Benedetto Altarpiece' by Lorenzo Monaco (painted in 1407-9).
The reason why some vermilion-containing areas had darkened, while others had not, was not fully understood until research at the Gallery showed that - together with light - chloride ions, usually from dirt that had settled on the paint surface, were key to the degradation mechanism.
Also, the research found that vermilion was protected from degradation by mixing with lead white or red lead – as in the lighter areas of the drapery in this painting. The shadows are painted in pure vermilion and have discoloured to grey.
Christ Glorified in the Court of Heaven: Central Predella Panel (1423-4) by Fra AngelicoThe National Gallery, London
In Fra Angelico's predella panel, the vermilion-containing paint has mostly remained in good condition because it includes some lead white in the pigment mixture. In general, here it has remained a vibrant red colour.
Combing the Hair ('La Coiffure') (about 1896) by Hilaire-Germain-Edgar DegasThe National Gallery, London
Vermilion remained an essential part of the artists' palette until the 19th century. Here we can see how vermilion is used in 'Combing the Hair ('La Coiffure')', made in about 1896, by the renowned French artist Hilaire-Germain-Edgar Degas.