̽��ֱ�� of Cambridge - pigment

'Extreme sleepover #17' – going underground in search of zombies

lw355 — Fri, 04 Mar 2016 08:37:51 +0000

Isla de Mona has been many things: a source of melons and cotton hammocks for conquistadors in the 16th century; a pirate haunt in the 17th and 18th centuries; an industrial island fertilising the fields of the Western world with the fossilised guano of giant fish-eating bats in the 19th; a US air base in the 20th; and now, both a nature reserve and a destination for migrants seeking a better life in the USA.

This tiny island, just seven miles by four, with no permanent settlement, lies in the dangerous Mona Passage between Puerto Rico and the Dominican Republic, and it is the prehistory that brings us here.

̽��ֱ��plateau of limestone and dolomite is riddled with caves filled with signs of human activity. Much of this is pre-Columbian (i.e. before the Spanish arrived in the late 15th century) and consists of painted images, finger-drawn designs and extensive extractive finger scratches, which are sometimes deep within the ‘dark zones’, where no natural light falls.

I am with archaeologists Dr Alice Samson from Cambridge’s McDonald Institute for Archaeological Research and Dr Jago Cooper from the British Museum for their summer fieldwork. As a conservator with specialism in the materials and techniques of painting, I am here to analyse the pigments used to make pre-Columbian markings and with the team look at the layer structures of engravings and painted images.

I’m using an X-ray fluorescence spectrometer to examine the elemental composition of the pictographs, and will later take tiny samples away for further analysis. I want to find out whether the people who made these images used materials that were at hand in the caves, or transported them in from elsewhere.

Mona’s prehistoric peoples appear to have lived on the island from at least 2800 BCE, surviving a century after the arrival of the Spanish at the end of the 15th century. ̽��ֱ��inhabitants at the time of the conquest, commonly referred to as Taínos, brought us the words hurricane, barbeque, hammock, canoe, potato and cannibal.

Caves feature prominently in Taíno mythology and it is likely that many of the anthropogenic images in the caves are zemís (considered by some the origin of the word ‘zombie’). Zemí refers to any object, animal, vegetable or mineral, which was animate and could be called upon to intervene in human affairs. Zemís were found, constructed or painted in 3D and 2D form. Although the presence of human-like figurative designs is common in Caribbean rock-art, Alice and Jago’s work is bringing to light a staggering amount of physical modification to the caves from the pre-Columbian era, particularly the extraction of soft white lime from the walls and ceilings. ̽��ֱ��purpose of this extraction and what the material was used for are not yet known.

Each morning I wake at 5.30am to the sounds of subtropical birds. It’s the only time of day cool enough to go for a run. ̽��ֱ��coastguards and rangers all eat early; for them, life on Mona is a cycle of week-on-week-off at work, with a small aircraft bringing them to and from the Puerto Rican mainland to Mona via a bumpy grass airstrip.

At the camp, there’s a small study centre (happily, with solar-powered Wi-Fi) as well as basic accommodation where the workers live, and where migrants can rest before they are moved from the island. Mona throws together strange combinations of people: border police, rangers, military personnel, scientists, cavers, immigrants and boy scouts.

We set off early in the morning. Some of the caves are nearby, but others involve more effort to carry our equipment, as they are some distance from our camp. Mona’s environment can be inhospitable and it has a fearsome reputation. There is little natural water, except sometimes deep in the caves. It is dry, hot and thorny, and the rocks are sharp. As we walk to the caves, we often disturb one of Mona’s endemic and therefore incredibly rare iguanas. They typically scuttle away from us into a hidden cave mouth.

Our team also includes Masters’ students from the Centro de Estudios Avanzados in Puerto Rico, and we work together analysing, documenting and photographing the evidence in the caves. Colonists, buccaneers, guano-miners and boy scouts have all left their mark, often with dated graffiti. On several days, we join a team of cavers who year on year visit this most cavernous location on earth to map the island’s 200-plus caves. It’s a great opportunity to learn about cave mapping and geology from experts.

If possible, lunch is taken in a cliff-side cave mouth, with a view out over the sea. On occasion, two nosy Red-Footed boobies wheel round and round to get a better look at us. ̽��ֱ��caves themselves are extremely hot, humid and dirty. At the end of the day we walk into the Caribbean sea, fully dressed in our ‘cave clothes’.

Images: Finger drawings and Lucy Wrapson

Credit: Alice Samson/El Corazon del Caribe Research project

Lucy Wrapson reports on her fieldwork analysing the curious cave paintings found on Isla de Mona, in the Caribbean, and their equally enigmatic artists.

Finger-drawn designs and extensive extractive finger scratches are sometimes deep within the ‘dark zones’, where no natural light falls

Lucy Wrapson

Alice Samson/El Corazon del Caribe Research project

Cave painting, Isla de Mona

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Why does the kingfisher have blue feathers?

amb206 — Wed, 12 Aug 2015 08:43:53 +0000

Scroll to the end of the article to listen to the podcast.

Kingfishers are notoriously shy. But one of the best places to spot them in Cambridge is the Botanic Garden where they perch in the swamp cypresses to fish in the lake.

̽��ֱ��brilliantly bright plumage of the kingfisher looks almost exotic in comparison to the more modest hues of many birds native to Britain. In motion, the kingfisher’s contrasting colours – orange, cyan and blue – produce a startling flash of colour.

Colour in nature is a fascinating topic. Understanding why and how plants and animals produce and employ colour requires researchers to collaborate and share their expertise across different disciplines. Dr Silvia Vignolini (Department of Chemistry) has been working with Professors Jeremy Baumberg (Department of Physics) and Beverley Glover (Department of Plant Sciences) to look at the extraordinarily clever ways in which nature makes spectacular colour effects.

Blue is a favourite colour of people around the world. But the production of intense blue presents challenges to nature. Most vertebrates are unable to produce blue pigment. ̽��ֱ��orange of kingfisher plumage is the product of tiny pigment granules but its cyan and blue feathers contain no pigments. These colours are ‘structural’. They are created by the intricate structural arrangement of a transparent material which, depending on its precise make-up and thickness compared to the tiny wavelength of light, produces a range of colours by ‘incident light’ – in other words light shining on the sample.

Structural colours feature in plants too – particularly in fruit and flowers. In research published in 2012, Vignolini and others revealed that an African plant called the Pollia condensata produces a blue fruit, which produces a strikingly shiny blue fruit. ̽��ֱ��researchers discovered that the Pollia fruit reflects back 30% of the light cast on it. Furthermore, its reflective properties stand the test of time in a remarkable way: a Pollia fruit, locked in a seed drawer at Kew Gardens for 100 years, had lost none of its blueness.

̽��ֱ��way in which plants like the Pollia achieve extraordinarily bright and long-lasting colours offers huge scope for material science. Vignolini says: “Cellulose, which is the main material used by this plant to produce colour, can also be manipulated in vitro to obtain a similar optical effect. By controlling the self-assembly process of cellulose, it is therefore possible to produce bio-mimetic colouration without using any toxic pigment.”

Because structural colours can be so intense, their origin in only transparent materials is hard to imagine. Vignolini uses the example of a soap bubble. “If you start from a perfectly transparent water-soap suspension and you blow a soap bubble, you can observe all the colours of the rainbow. These colours cannot be the results of pigmentation, because the liquid is transparent. Instead, the colours result from creating a very thin layer, just a few hundreds of nanometres thick, of the suspension that interacts with light.” she says.

“A plant or animal cell does something similar. Using simple sugars, it creates a multi-layered nano-structure that optimises the reflection of the blue colour. Understanding these incredibly precise processes is the key to be able to copy and mimic these materials.”

In a paper published in 2011, Dr Bodo Wilts (formerly Cambridge, now ̽��ֱ�� of Fribourg) and colleagues focused on the striking plumage of the kingfisher. They found that the cyan and blue barbs of its feathers contain spongy nanostructures with varying dimensions, causing the light to reflect differently and thus produce the observed set of colours. ̽��ֱ��subtle differences within colours are produced by tiny variations in the structure of the barbs.

Kingfisher feathers reflect light in a way that scientists describe as semi-iridescent. ̽��ֱ��feathers of peacocks and birds of paradise are truly iridescent. Iridescence is produced by the ways in which layers of material are perfectly aligned and repeated periodically to achieve a shimmer effect. Semi-iridescence is produced when the layers are not quite perfectly aligned but slightly disrupted, thus causing a smaller span of iridescent colour.

There’s much more to be discovered about colour in nature. “Researchers are beginning to learn more about birds’ vision. This work will help us to grasp how they see colour and how they respond to it. To unlock the secret of how cellulose or keratin make fabulously bright colour will involve continuing collaborations between biologists, physicists and materials scientists, ” says Vignolini.

̽��ֱ��kingfisher is just one of 100 bird species to be seen in the Botanic Garden which provides an important habitat for birds and other wildlife in the heart of Cambridge. Among them is the increasingly rare song thrush. Mistle thrushes, too, can often be seen in winter atop trees full of mistletoe. ̽��ֱ��Garden also has thriving populations of great and blue tits while flocks of long-tailed tits are often heard as they fly from tree to tree to search for food. Summer visitors regularly include a pair of sparrowhawks and flocks of swifts.

Next in the Cambridge Animal Alphabet: L is for a creature that has helped archaeologists learn more about the life of people inhabiting the remote and windswept Isle of Oronsay 6,000 years ago.

Have you missed the series so far? Catch up on Medium here.

Inset images: Kingfisher (Gilberto Pereira); ̽��ֱ��common kingfisher, Alcedo atthis, and its three main feather types: orange feathers at the breast, cyan feathers at the back and blue feathers at the tail (Doekele Stavenga, Jan Tinbergen, Hein Leertouwer, Bodo Wilts); Scanning electron micrographs (SEMs) of sectioned barbs of breast and tail feathers (Doekele Stavenga, Jan Tinbergen, Hein Leertouwer, Bodo Wilts); Close up of a cut vacuole and the surrounding spongy structures (Doekele Stavenga, Jan Tinbergen, Hein Leertouwer, Bodo Wilts).

The Cambridge Animal Alphabet series celebrates Cambridge's connections with animals through literature, art, science and society. Here, K is for Kingfisher. Look out for them among the swamp cypresses at the Botanic Garden, where the secrets behind their cyan and blue feathers are being studied by an extraordinary collaboration of scientists.

Understanding these incredibly precise processes is the key to be able to copy and mimic these materials

Silvia Vignolini

Fitzwilliam Museum

Detail of Kingfisher, woodblock printed in colour, Kitagawa Utamaro

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Licence type:

Attribution

Who colour-coded Christmas?

lw355 — Tue, 18 Oct 2011 11:13:44 +0000

Jolly Father Christmas with his rosy cheeks and scarlet coat, shiny green holly with its bright red berries, glittering red decorations on a lush green Christmas tree – the clichéd colour coding of the Christmas season seems as entrenched as the conventions in the West of wearing black to funerals and white to weddings. But where do the familiar Christmas colours come from and what do they really mean?

On Saturday 22 October, Dr Spike Bucklow from the ̽��ֱ�� of Cambridge’s Hamilton Kerr Institute will be examining artists’ materials to ask who came up with the colours of Christmas at the Festival of Ideas, the UK’s only festival devoted to the arts, humanities and social sciences (www.cam.ac.uk/festivalofideas).

“We associate Christmas with red and green because that’s the way we’ve always done it.” said Dr Bucklow. “But one can trace the roots of this colour coding back through the centuries, to a time when the colours themselves had symbolic meaning, possibly as a way of accentuating a significant division or a boundary.”

Although the Victorians wholeheartedly embraced Christmas and introduced many of the traditions we see today – from cards to crackers and trees to turkeys – Dr Bucklow believes that the Christmas colours were not inspired by the Victorians but rather revived by them, and that their significance draws on a history many centuries older.

His research over the past three years, funded by the Leverhulme Trust, has focused on the art history of medieval rood screens, which date from the 14th to the 16th centuries and were used to separate the nave from the chancel of churches. “Although many were defaced or even destroyed during the Reformation, on some of those that survive are beautiful painted panels depicting saints, as well as local donors, merchants and serfs. They were commissioned by parishioners and represent the biggest investment of corporate art that this country has ever seen,” he said.

Strikingly, the vast majority are painted in red and green. “ ̽��ֱ��panels were painted by newly settled members of the Flemish immigrant population or by itinerant English and continental European artists who worked together,” he explained. “Choosing red and green would have been a question of pigment availability but it would also have represented a tradition based on a consciously chosen symbolic meaning. If you like, these colours would have been part of a common language of panel painting that everyone knew about but didn’t necessarily express.”

Dr Bucklow speculates that this meaning is linked to an emphasising of the different spaces in the Church: at one side of the screen, the nave where the parishioners sat; at the other side, the priest’s holy sanctuary and the altar. He further suggests that the Victorians, who carried out some of the early restoration of the medieval churches, would have noticed the colour coding and might have adopted it to accentuate another boundary – the end of one year and the beginning of another at Christmas.

However, he believes that although the medieval rood screen painters effectively left the biggest body of physical evidence for the existence of colour coding, the use of red and green as symbolic colours goes back even further. “As one example, the red–green colour coding appears in the Mabinogion, a collection of Welsh stories from the 13th century, but almost certainly based on an oral tradition that dates back to the pre-Christian Celts many centuries before. Here, the hero comes to a half-red, half-green tree that marks a boundary.”

Today though, in a world flooded with every hue imaginable, Dr Bucklow believes we no longer consider colour to be particularly meaningful. “ ̽��ֱ��sensation of seeing colour has become devalued and downgraded,” he observed. “Our life experience is impoverished by not acknowledging the possibility of symbolic meaning. By contrast, in the Middle Ages and earlier, colour was integrated into a cultural awareness and even an understanding of life. It touched all members of society and conveyed a deeper message.

“For red and green, our comparatively recent obsession with associating these colours with Christmas masks a profound and long-forgotten other history.”

‘Who colour-coded Christmas?’ will take place on Saturday 22 October at the Faculty of Law 11am – 12noon as part of Cambridge ̽��ֱ��’s Festival of Ideas. Pre-booking is required. Suitable for age 14+.

̽��ֱ��conventional colours of Christmas – red and green – are not, as many might suppose, a legacy of the Victorians. Instead, they hark back to the Middle Ages and perhaps even earlier, according to Cambridge research scientist Dr Spike Bucklow.

For red and green, our comparatively recent obsession with associating these colours with Christmas masks a profound and long-forgotten other history

Dr Spike Bucklow

Gaeten Lee

Santas

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes

Dragonsblood: the alchemy of paint

bjb42 — Tue, 01 Sep 2009 00:00:00 +0000

Dragonsblood – a red pigment prized for the best part of two millennia and discussed by apothecaries, alchemists and painters alike – was said to be the mixed, coagulated blood of dragons and elephants collected from the place where the beasts fought and died together. Actually, it was a tree resin, and a sample of the pigment can be found today in Queens’ College, in a medicine cabinet assembled in 1702 by Giovanni Francesco Vigani, the ̽��ֱ�� of Cambridge’s first Professor of Chemistry. Dragonsblood also features inThe Alchemy of Paint, a book about the colours used by medieval artists. It is a book that attempts to understand medieval artists’ materials as they were perceived by the people who used them. But it was inspired by a very practical modern problem.

Conserving the lost Retable

I work as a scientist in the ̽��ֱ��’s Hamilton Kerr Institute, a department of ̽��ֱ��Fitzwilliam Museum that specialises in the conservation and restoration of paintings. In 1994, the Institute received the Thornham Parva Retable, a 12ft-long altarpiece painted in the 14th century for a Dominican Priory in Thetford, Norfolk, by artists from Norwich. It had survived destruction in Henry Vlll’s dissolution of the monasteries in the 16th century but was lost until 1927, when it was discovered in a stable loft. By this time, the original 1330s paint was almost entirely covered with paint applied in the 1770s, which had to be removed in order to conserve the medieval material.

̽��ֱ��Institute’s treatment of the Retable was the focus of considerable scrutiny because it is the largest, best-preserved and second oldest altarpiece in the UK. A 22-strong committee of academics, funding bodies and parishioners discussed how to proceed. Over the course of two years, during which microscopic paint samples were analysed by electron microscopy, gas chromatography and mass spectrometry, a consensus gradually came together and the conservation work began.

Cultural contexts, recipes and alchemists

̽��ֱ��suggested treatment strategy was accepted, in large part, because it was based on scientific evidence. As a conservation scientist, from these analyses I understood the consequence of the artists’ materials in terms of their physical and chemical properties, their interaction with the environment and their behaviour when undergoing conservation treatment. But I began to wonder about the medieval artists themselves: how would they have explained the materials and methods involved in making an altarpiece? Were they influenced by their Dominican patrons or indeed by the closeness of Cambridge’s intellectual orbit, both well known in the 14th century for their interest in science?

Looking for clues, I consulted artists’ treatises detailing medieval recipes for pigments and paints, such as the manuals written by Theophilus Presbyter, a 12th-century Benedictine monk, and Theodore Turquet de Mayerne, physician to Charles I and friend of the artist van Dyck. But connecting the physical evidence offered by paintings to the artists’ recipes, which often verged on the bizarre and magical, was not always straightforward. ̽��ֱ��legendary origin of dragonsblood is a case in point. Why would artists say that this derived from dragons and elephants fighting to the death when they knew dragonsblood was really a tree resin? Other medieval recipes were just as evocative: a stone from the doorstep of Paradise and a metal won by one-eyed horsemen from ferocious griffins near the North Pole. ̽��ֱ��recipe books certainly didn’t make sense according to the science that I knew. I needed to brush up on the science with which the artists were familiar: alchemy.

Cloak-and-dagger

̽��ֱ��medieval palette owed much to what some have described as ‘cloak-and-dagger science’, conducted by artists employing secret recipes to create the luxurious colours we are familiar with today. This was the era of alchemy, best known for the quest of alchemists to turn base metals into gold and to find the elixir of eternal life, when scientists like the Dominican Albertus Magnus wrote on the subject. Researching their writings provided me with the necessary technical background to begin the challenge of connecting the physical evidence offered by the scientific analysis of paintings and the recipes in artists’ treatises. ̽��ֱ��Alchemy of Paint is the fruit of that challenge.

Colours, it seems, were read differently in the mindset of medieval Europe. Not only in how people responded to them – ‘scarlet’ today describes a colour, but it was originally a type of cloth – but also in how artists considered their materials. Their ideas, fed by the philosophers and scientists of the time, would probably not be too out of place in the ̽��ֱ��’s 1209 syllabus 800 years ago. Today, an awareness of their ideas helps ensure that conservation of art is undertaken with cultural sensitivity and also immeasurably enhances our appreciation of their art.

Walking the dog

Attempting to join up artists’ theory and practice has been a lot of fun. Walking my dog around Cambridgeshire, across fields and over the nearest things to hills that the region has to offer, I saw the sun set and the stars come out, the seasons come and go, and the colours change. I attempted to familiarise myself with what CS Lewis calledThe Discarded Image, the poetic way that the medieval world view synthesised ‘the whole organisation of their theology, science and history into a single, complex, harmonious mental model of the universe’. In the medieval world, everything had meaning, even the pigments they painted with. Guidance from the ‘discarded image’ helped me to consider artists’ materials and methods in ways that modern science could not.

̽��ֱ��Alchemy of Paint was a response to a very practical situation: the desire for a broader and deeper view of the Thornham Parva Retable, as well as the Westminster Retable, treated between 1998 and 2005 at the Institute, and the Macclesfield Psalter acquired by ̽��ֱ��Fitzwilliam Museum in 2005. I was lucky enough to be by the bus-stop, as it were, when three medieval masterpieces came along together. It was an enormous privilege to get to know them and they all informed the thinking behindThe Alchemy of Paint. And I certainly hope that the book will have a practical effect – to encourage students and researchers to engage more profoundly with the products of other cultures.

And the Thornham Parva Retable? It finally returned home in 2003, its treatment hailed as a great success by parishioners, funding bodies and the academic community alike. It even won an award.

For more information, please contact the author Dr Spike Bucklow at the Hamilton Kerr Institute.

Through his exploration of the science of art, the recipes of medieval artists and the writings of alchemists, art conservation scientist Spike Bucklow sets out to disentangle the alchemy of medieval paint.

I began to wonder about the medieval artists themselves: how would they have explained the materials and methods involved in making an altarpiece?

Spike Bucklow

Dean and Chapter, Westminster Abbey

Detail from Westminster Retable

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes