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16 March 2014

The Colour Green

With St Patrick’s Day upon us it seemed fitting to take a closer look at some green pigments used throughout art and history.

Green earth pigment

Green earth pigment (or Terre Verte, Stone Green, Verdetta, Celadonite) is composed of clay coloured by iron oxide, magnesium, aluminium silicate, or potassium. The clay was crushed, washed and powdered. It was used since the time of the Roman Empire until the end of the Renaissance and was highly popular in medieval painting, especially for underpainting of fleshtones. An example is shown below in The Annunciation (1398-1311) by Duccio di Buoninsegna. Here faces were first painted with the green pigment and then overlaid with pink to give a realistic hue. In this case the pink has faded giving the impression of green skin. Green earth pigment was sourced from regions in the south of France and in Italy around Verona.

 

 Gabriel dawned on light purple and light blue garments standing to the left of Mary facing her straight on. Mary dressed in a luscious and rich ultramarine robe and vermilion dress stands on the right with her body facing the viewer with her face looking toward Gabrial. They are set in simple and articulated architectural surroundings. The architectural setting is made to mimic three dimensionality with crude perspective and bold shadows and highlights. Gabriel is depicted motion, his right leg extended back with his foot just about to lift from the  ground, and his right hand extended out towards Mary, his hand  gesturing the peace sign. Mary appears to pull back, with her left arm covering her chest reaching over her shoulder to gripon to her robe. Her left arm hangs down beside her body holding the bible open with text. Above and in between Gabriel and Mary is a  white  dive with rays of light  representing the Holy Spirit shining towards her.
The Annunciation by Duccio di Buoninsegna: The Archangel Gabriel announces to the Virgin that she will be visited by the Holy Spirit and bear the son of God. Held at the National Gallery

 

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Malachite

Malachite is a copper carbonate hydroxide mineral (copper(II) carbonate), and is green due to the presence of copper. It was used as a mineral pigment in green paints from antiquity until about 1800. It is fairly lightfast and very sensitive to acids meaning its colour can vary.

 

An extreme close  up and zoom of green malachite. It has two vivid textures, one has the appearance of moss which is a dark green, and makes up the majority of the malachite sample.  The  second texture is smooth and  round lighter green bundles, which look like the heads of baby mushrooms. The sample has the appearance of fistfulls of the moss texture being piled ontop and beside of each other, with the small round and smooth bundles placed in between the rough topography of the sample.
Brazilian malachite specimen highlighted by spheroidal rosettes of azurite (source) 


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Artist Pietro Perugino used finely ground malachite in his 1503 painting Nativity to colour the bright green garments of the worshippers. 

 

Four wise men kneel to the left of and behind the baby Jesus who is lying on a purple cloth facing the viewer while Mary kneels to the right of him. Their hands are raised  to their chest in prayer, except for one wiseman farthest to the right who has his hands raised to his chest in motion, as if exclaiming with stunned joy. Directly behind them is an ornate four post gazebo, with a cow lying down and a donkey  standing on the far left side of the painting. The backdrop to the scene is a wide and open pastoral view, with green fields and few trees in the far distance. Rolling hills flank the sides of the background fading out to a light blue illusting great depth and space.
Green pigment malachite is found in Nativity by Pietro Perugino (1448-1523)

 

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Malachite has also been found in the King George III copy of the Gutenberg Bible, held at the British Library using Raman Analysis.

 

Close up of a single sheet with two columns of neat bold text inblack  ink with red ink headings. Ornate embellishments are painted between the columns of  text and surrounding the, like a sideways 8 looping around everything. The embellishment is a floral theme with vines swirling around and flowers stemming off, with colourful birds and a monkey perched throughout the vines. The substrate is a pale beige colour and is in very good condition, with just some engrained dirts visible around the edges.
Gutenberg's (42-line) Bible: Opening of Proverbs. Johann Gutenberg, Johann Fust and Peter Schoeffer. Mainz, 1455 British Library C.9.d.4, f.1. Copyright the British Library Board

 

 

Cobalt green

Cobalt green is a moderately bright and translucent, but highly permanent, green pigment. The compound is formed by heating a mixture of cobalt (II) oxide and zinc oxide and was discovered in 1780 by Swedish chemist Sven Rinman. It can be mixed with other pigments and is also known as Rinman’s Green or Zinc Green.

 

Close up of ground cobalt green pigment, in a loose powder.
Cobalt green (source)

 

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Cobalt green was never very popular due to its high cost and weak tinting power. Researchers at the University of Washington have discovered that cobalt green possesses special magnetic properties and is now being used in the field of spintronics. Spintronic devices are used for computer storage and memory. Cobalt green has found success with spintronic devices as it can be used at room temperature while other materials must be super cooled.

Verdigris

This is a basic copper acetate and is formed when copper is exposed to acetic acid vapours.  The natural patina that forms on copper roofs is often called verdigris, but in non-polluted areas it is in fact malachite (basic copper carbonate).  In polluted areas, though, it is antlerite, a basic copper sulphate.  They are all similar colours so are easily confused, but verdigris in particular causes problems in manuscripts – it goes brown and can burn through the parchment and cause staining on adjacent folios. Verdigris has been used on murals in Pompeii, throughout the Renaissance and on medieval manuscripts including the Lindisfarne Gospels and Book of Kells.

A light aquamarine colour, in powder form, is in a clear glass jar with a black lid, sitting on a black table with white background.
Verdigris (source) 

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Verdigris was found to be unstable and unwilling to mix easily with other pigments. In fact the great Leonardo da Vinci warned against its use in his treatise on painting and was leter replaced by the more stable Chrome Green.

Close-up detail of paint layer. Three spots of an opaque mustard colour paint sit on top of large areas of  a transparent glass-like turquoise colour, which has many small cracks. Many of the cracks look like misshapen rectangles and triangles. Surrounding the turquoise is a line of black, with some areas having a higher sheen, and some areas looking mat, with small areas left abraded, now missing pigment. Above this is an area painted with a chartreuse yellow, also with many small cracks.
Verdigris has been used to decorate the initials on f44v of the Lindisfarne Gospels shown here at 50x magnification (see here for more microscopy images of the Lindisfarne Gospels)

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Viridian

Viridian was patented in 1859 and is a hydrated chromium(III) oxide Cr2O3 pigment described as a dark shade of spring green.

Close up of powdered veridian, apple green in colour. The head of a silver spoon is holding a spoonful of the powder above the pile of veridian.
Viridian (source)

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Viridian was used by Vincent van Gogh in many of his works including Café Terrace at Night, 1888 (Kröller-Müller Museum, Otterlo) and the Night Café (Yale University Art Gallery). Van Gogh to his brother Theo in 1888: "I sought to express with red and green the terrible human passions. The hall is blood red and pale yellow, with a green billiard table in the center, and four lamps of lemon yellow, with rays of orange and green. Everywhere it is a battle and antithesis of the most different reds and greens.” [1]

The Night Café

CC zero Artist Vincent van Gogh (1853-1890) The Night Café, 1888. Oil on canvas currently at Yale University Art Gallery

In many cases a combination of pigments was used to create green colour. Recent analysis of the Sir Gawain and the Green Knight manuscript have shown that indigo (blue) over orpiment (yellow) was used in some areas, while a single mineral green was used in others.

Painting of a man with scruffy blond hair on loose black garb. Both his hands are extending to the left holding a battle axe. The background seems to have quite a bit of pigment loss, showing a yellowish ground coming through where loss of the dark green paint has been abraded or scraped away. There are two large dark green vases on either side of the man, with crude red and white flowers sticking out.
 Sir Gawain and the Green Knight, Cotton Nero Ax folio 129v

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Christina Duffy

Reference: [1] Vincent van Gogh, Corréspondénce general, number 533, cited by John Gage, Practice and Meaning from Antiquity to Abstraction

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