A partnership between science and history is providing fresh insight into the evolution of the colourful illuminations adorning historic manuscripts, reports Kathryn Roberts On 25 December, millions of people will celebrate the 2014-year old Christmas story as told in the synoptic gospels of Matthew, Mark, and Luke. That we know this story, and others relating to the life of Jesus of Nazareth, is the legacy of early century monks, who would meticulously copy, and sometimes translate, manuscripts from monasteries around the world. Additionally, they would illustrate their versions with vivid colours, which have not faded with time. Many medieval manuscripts remain as beautiful as they were hundreds of years ago.
And that’s good news for Andy Beeby, professor of chemistry at Durham University, UK. For the past 18 months, he and fellow chemists at Durham, Kate Nicholson and Andrew Duckworth, have been ‘obsessed’ with analysing the pigments used in such manuscripts.
‘In the summer of 2013,’ explains Beeby, ‘an exhibition of objects dating back to 8th century Anglo Saxon England – including the Durham Gospels (c.700 AD), the Lindisfarne Gospels (before c.710 AD), and the Northumbrian Gospels (late 8th century) – came to the university’s Palace Green Library. One of the benefactors approached me and asked if I might be able to shed some light on the materials that were used by the monks. He wanted to know how the monks got their colours and why the colours had remained stable for so long.’
At the time, Beeby was aware that Robin Clark, professor of chemistry at University College London, UK, had already done analyses of, among other books, the Lindisfarne Gospels, using Raman spectroscopy, a non-invasive, non-sampling analytical technique. Clark had confirmed the use of a range of primitive, natural dyes in the manuscript, including indigo (C16H10N2O2) in the blues, orpiment (As2S3) in the yellows, minum or red lead (Pb3O4) in the orange and reds, and vergaut – a mixture of indigo (blue) and orpiment – as one of the greens, the other green being the copper-based pigment verdigris.
Clark also identified the white areas in the manuscript as either plain parchment, ie treated animal skin, or chalk or white lead (2PbCO3.Pb(OH)2), the latter two in the pink and beige areas. And since the gold on the manuscripts did not give the characteristic Raman spectra for common gold imitators, such as orpiment, pararealgar (As4S4), mosaic gold (SnS2) or Naples yellow (Pb3Sb2O8), he concluded that the monks probably used metallic gold.
Beeby and his team agreed to look at the manuscripts from the exhibition, focusing on the ones that had not so far been studied scientifically. ‘At this point,’ says Beeby, ‘I was introduced to Durham historian Richard Gameson, who organised the exhibition and who is an authority in the history of book production and in medieval art. I was quickly made aware of the value of the manuscripts. They are, of course, priceless, you cannot simply move them to a chemistry department. The analytical equipment would have to be moved to them.’
That’s exactly what the chemists did. They moved their large and heavy laboratory spectrometers to the library, though later they built portable instruments that fitted into the boot of Beeby’s car. In the main, they used Raman spectroscopy to identify the pigments, but also optical reflectance spectroscopy. By looking at the optical reflectance spectra, for example, they could distinguish between a copperbased pigment and a non-copper based pigment, and then use Raman to confirm the identity of the pigment. ‘Raman is particularly good for identifying inorganic, symmetrical molecules that are easily polarisable by light,’ says Beeby.
The team confirmed the use of red lead, indigo, orpiment, vergaut but not verdigris in the Durham and Northumbrian gospels. These pigments, except orpiment, would have been available locally. Beeby speculates that the orpiment probably came from Italian volcanic regions since the monks would have made pilgrimages to Rome and so could have traded en route. Very quickly, however, the project took on a new dimension. Beeby explains: ‘We soon started to ask other questions, such as ”How did the technology [of illumination] change during the early centuries?”, and as other libraries in the UK heard of our work, we were invited to analyse their books and the project snowballed.’
Since the summer of 2013, the Durham chemists, known as ‘Team Pigment’, have investigated 40–50 medieval manuscripts owned by libraries across the UK, only some of which relate the gospel stories. ‘We are now committed to doing a systematic study of the pigments used in illuminated manuscripts produced in Britain from around 600 AD to the late 15th century, ie hand produced single books before the introduction of printing,’ says Beeby.
Specifically, they are looking at books which have a known provenance – ie place and date of production – and ideally with a known track record. The latter is important for identifying any outof-date tampering to the manuscripts. Ultimately as they map their data, they will show the way in which new pigments were introduced and reveal the definitive ‘story of the technology of illuminated manuscripts’.
Here Gameson plays a crucial role. He has spent the past 30 years studying medieval manuscripts. ‘There are all sorts of clues that enable historians like myself to make deductions about the place and date of a manuscript – for example, notes left by the scribes as well as their names and date,’ he explains. ‘Even how the parchment was arranged varies according to when and where it was produced.’ He also looks at script styles and is able to date a script according to a particular half century in which was written. From the 12th century onwards many of the scribes would have been ‘urban professionals’, he says, who paid taxes and for which there are records.
But while many of the scribes also left ‘recipe books’, these were more aides memoires than providing any useful information on the composition of the dyes and materials, he says. ‘Raman spectroscopy has provided this detail and allowed us to test our assumptions and the evidence we have gained from the manuscripts.’ Importantly, he says, the scientific data on the palettes adds another dimension to his ability to group and place books and to understand their cultural significance. ‘The dialogue between science and history enriches both,’ he says. M
Meanwhile, Team Pigment has added a new analytical instrument to its mobile toolbox – a multispectral imaging camera. ‘The big advantage of this technology,’ explains Beeby, ‘is that unlike Raman, which identifies pigments in a tiny spot of ca 0.1mm diameter, we can identify several pigments in a much larger area, which speeds up the analysis.’
There is little doubt that the partnership between science and history is providing fresh insight into the evolution of the technology of illuminations. In one of the later manuscripts produced in the 12th century, the Book of Symeon – which describes the founding of the city of Durham after the Norman Conquest – the chemists identified the use of two new pigments: lazurite (Na8 [Al6 Si6 O24]Sn ), a deep blue, and vermilion (HgS), a deep red. The only known sources of lapis lazuli at that time was the Badakhshan mines in Afghanistan, and its use implies the existence of a trade route from Afghanistan, through Europe, to the north east of England, says Beeby.
During the 12th and 13th centuries, book production changed from being the sole domain of the churches to a business run by professional people and one can speculate that these people would have brought new pigments to the process. Certainly by the end of the 15th century, there were several new pigments available – azurite, a blue copper pigment; lead tin yellow as a slightly less toxic alternative to orpiment, and mosaic gold as an alternative to metallic gold.
As Gameson points out, the richest, most expensive colours were most likely to have been used for the most important figures in a given theme. The chemists were able to confirm this in their analysis of pigments in a late 14th century missal; much of the blue used was the relative cheap azurite, but the robes of the Virgin Mary and God were the very expensive lazurite.
There are over tens of 1000s of surviving medieval manuscripts in Britain alone. From the period before 800, there are less than 2000 – but there are around 9000 9th century manuscripts in the world. Ironically, as Gameson points out, our emphasis today is on making information available to the widest number of people in the shortest amount of time. In contrast, medieval monks were less concerned about reaching lots of people but their technology has stood the test of time. ‘I’m quietly confident that the stories told by these monks will be read thousands of years from now, when who knows what will have happened to stories that have been stored digitally.’
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