̽��ֱ�� of Cambridge - paint

African fruit ‘brightest’ thing in nature but does not use pigment to create its extraordinary colour

bjb42 — Tue, 11 Sep 2012 09:00:30 +0000

̽��ֱ��‘brightest’ thing in nature, the Pollia condensata fruit, does not get its blue colour from pigment but instead uses structural colour – a method of reflecting light of particular wavelengths- new research reveals. ̽��ֱ��study was published today in the journal PNAS.

Most colours around us are the result of pigments. However, a few examples in nature - including the peacock, the scarab beetle and now the Pollia condensata fruit – use structural colour as well.

Fruits are made of cells, each of which is surrounded by a cell wall containing cellulose. However, the researchers found that in the Pollia condensata fruit the cellulose is laid down in layers, forming a chiral (asymmetrical) structure that is able to interact with light and provide selective reflection of only a specific colour. As a result of this unique structure, it reflects predominately blue light.

̽��ֱ��scientists also discovered that each individual cell generates colour independently, producing a pixelated or pointillist effect (like those in the paintings of Seurat). This colour is produced by the reflection of light of particular wavelengths from layers of cellulose in the cell wall. ̽��ֱ��thickness of the layers determines which wavelength of light is reflected. As a result, some cells have thinner layers and reflect blue; others have thicker layers and reflect green or red.

̽��ֱ��researchers believe that the plants invest in the complicated colouring structure as a mechanism for seed dispersal. Although the Pollia fruit does not provide any nutritional value, birds are attracted to its bright colouring – possibly as a means of decorating their nests or impressing their mates.

Dr Beverley Glover from the ̽��ֱ�� of Cambridge’s Department of Plant Sciences, who jointly led the research, said: “This obscure little plant has hit on a fantastic way of making an irresistible shiny, sparkly, multi-coloured, iridescent signal to every bird in the vicinity, without wasting any of its precious photosynthetic reserves on bird food. Evolution is very smart!”

Because of how it is created, the colour of the Pollia condensata fruit does not fade. ̽��ֱ��researchers found that samples of the fruit in herbarium collections dating back to the 19^th century were as colourful and shiny as ones grown today.

Dr Silvia Vignolini, lead author on the paper from the ̽��ֱ�� of Cambridge’s Department of Physics, said: “By taking inspiration from nature, it is possible to obtain smart multifunctional materials using sustainable routes with abundant and cheap materials like cellulose.

“We believe that using cellulose to create coloured materials can lead to many industrial applications. As an example, edible cellulose-based nanostructures with structural colour can be used as substitutes for toxic dyes and colorants in food. Moreover, the fact that the processes involved in cellulose extraction and manipulation are already used in the paper industry facilitates the use of such materials for industrial applications such as security labelling or cosmetics.”

̽��ֱ��research was supported by the Leverhulme Trust with some funding provided by the Engineering and Physical Sciences Research Council (EPSRC).

Listen to an interview with Beverley Glover on the Naked Scientists about the research.

Unique blue fruit’s colour does not fade even after a century

This obscure little plant has hit on a fantastic way of making an irresistible shiny, sparkly, multi-coloured, iridescent signal to every bird in the vicinity.

Beverley Glover

Silvia Vignolini

Pollia condensata fruit

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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

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Yes

A Class Apart

bjb42 — Wed, 26 May 2010 12:07:53 +0000

Social mobility, recent research tells us, has ground to a halt. Not just that, it has actually slipped backwards since the 1950s with the chasm between classes even wider than ever. There are many ways of measuring social mobility, of course, and one of them is education. Achievement within the education system is seen as one of the critical benchmarks for social mobility.

̽��ֱ��latest figures paint a dispiriting picture. A report by educational charity the Sutton Trust earlier this year argued that the top comprehensives were even more exclusive than the country’s remaining grammar schools with only 9.2% of children at the top 164 comprehensives coming from "income-deprived" homes, even though those schools drew their pupils from areas where about 20% were poor.

Only last month government watchdog the Office for Fair Access called for sweeping reforms because working class pupils now have less chance of getting into the most sought-after universities than 15 years ago. At seven of the Russell Group universities – the UK's 20 leading research institutions – less than 5% of students came from low-participation neighbourhoods.

̽��ֱ��relationship between society and education is an area that has fascinated Diane Reay, Professor of Education at Cambridge ̽��ֱ��’s Faculty of Education, since she was an undergraduate at Newcastle. Why? “Because I was brought up in a working class mining community and inequality of all kinds has been a lifelong concern,” she says.

Reay forged her career in teaching, working in London primary schools for 20 years before taking a PhD and moving into academia (South Bank Polytechnic, King’s College London, London Met, Cambridge – “quite a mix”). She’s made her name as a sociologist, who takes a feminist ethnographic approach – in other words, she embeds herself within her research field to observe, analyse and record the communities she’s studying.

Her priority, she says, is to engage in research with a strong social justice agenda to address inequality in all its guises. ̽��ֱ��projects she has undertaken over the past 10 years are set against backdrops that range from inner city schools to the most selective universities - with the accent on “social class, gender and ethnicity and how they play out in people’s actual lives”. In academic circles her best-known work is a study of home/school relationships and she is acknowledged for her innovative work in analysing social class.

Prompted by a concern about educational inequality, Reay’s latest work revisits economic historian RH Tawney´s conclusion in 1931 that social class is the hereditary curse of the English educational system, constraining a sense of social solidarity and limiting freedom. "Freedom for the pike is death to the minnows" as he famously put in his book Equality.

R H Tawney was a pioneer of adult and workers’ education – though himself educated at Rugby and Oxford. As an activist, he devoted his intellect and energy to putting into practice his passionate belief in social justice. He joined the Workers Education Association (WEA) and travelled up and down the country teaching at trade unions and working men’s institutes, lecturing at Stoke-on-Trent one day and in Rochdale the next. This he described as having two-way benefits. “ ̽��ֱ��friendly smitings of weavers, potters, miners and engineers, have taught me much about the problem of political and economic sciences which cannot easily be learned from books”.

Tawney was convinced that true democracy could be achieved only through the “elimination of all forms of special privilege which favour some groups and depress other.” In his book Equality (1931) he argued that difference between groups (which should be valued) was no reason for not seeking the largest possible measure of equality of opportunity, environment and circumstance.

Reay believes that many of the barriers to equality that Tawney identified almost a hundred years ago continue today – both within and beyond the educational system. Her analysis of the relationship between education and social class in contemporary Britain throws up many interesting questions – and turns some accepted thinking on its head.

A paper in collaboration with other researchers explored the positive decisions of middle class parents to send their children to urban comprehensives as a result of their beliefs in the principle behind non-selective state schools. In the course of in-depth interviews it emerged that many of these parents saw the mixed environment of their local schools as a resource that would benefit their children for “coping in the real world” or “toughen them up”– and that genuine mixing of social groups was only rarely taking place.

In a later project Reay looked at the question of “fitting in or standing out” for working class students at four contrasting universities. Although her sample was not statistically significant, her findings that high-achieving working class students often under-perform and feel disappointed, and that their pathway to top universities is often more a question of “luck and happenstance” than planned design, are particularly pertinent set against recent data. This shows that the percentage of students from the two lowest socio-economic groups gaining places at Cambridge was just 3.7 and at Oxford a mere 2.7 (Higher Education Statistics Agency report).

Social mobility is a problematic phrase bringing assumptions and implications. ̽��ֱ��underlying concept is of movement upwards and downwards. At the bottom of the heap sits the working class with council estates, manual jobs and low aspirations among its youngsters; at the top stand the upper/middle classes with glittering careers, large houses and young people with unassailable self-confidence.

Life just isn’t as simple as that – and real people don’t fit into neat categories. Modern sociology recognises more dimensions and cultural subtleties in the shifting social roles that people move into and out of. As Reay points out, the area of education in most urgent need of reforming is vocational training where Britain lags way behind its European partners.

“ ̽��ֱ��reality is that any current growth in the jobs market is in the service and care sector – and that’s an area that’s been badly neglected,” she says.

Just back from a Nordic Federation Sociology of Education conference in Iceland, Reay speaks warmly about Finland where children don’t start formal school until they are seven years old and there’s “no setting, no streaming and no testing”. It’s a country where teaching is the second most prestigious profession - and its children come top of the Programme for International Student Assessment (PISA) league for literacy and second for numeracy. “Private schools educate only 2% of children in Finland, and those that do exist were set up to provide an alternative kind of education,” says Reay.

Reay is tremendously excited about her next project which is writing a paper for ̽��ֱ��Journal of Educational Policy describing her vision for a socially just education system – “a fantastic opportunity”. On a broader and more pragmatic front, she fears that the new coalition’s proposal to extend choice will further empower already powerful groups in society “although the pupil premium for poorer students may genuinely help to redistribute resources”.

Reay makes no bones about the fact she’d like to see private schools abolished - as did expensively-educated Tawney. “As long as children continue to be educated apart from their peers from different class and ethnic backgrounds, and 'a good education' remains the prerogative of the upper and middle classes, social class will continue to be the curse of the English, and beyond that the British, education system,” she says.

Professor Diane Reay will be speaking at the Hay Festival on June 3^rd, at 5.15pm.

Despite our best efforts, social mobility in the UK does not seem to be improving. Diane Reay, Professor of Education at the ̽��ֱ�� of Cambridge, will be speaking at Hay about the hereditary curse of the English education system and her developing vision for a “socially just” replacement.

As long as children continue to be educated apart from their peers from different class and ethnic backgrounds, and 'a good education' remains the prerogative of the upper and middle classes, social class will continue to be the curse of the English, and beyond that the British, education system

Dr Diane Reay

wsilver from Flickr

Empty swingset

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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

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Yes