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When it comes to exploring our cultural artefacts, synchrotron light provides a sophisticated investigative tool, complementing the more traditional methods established over the centuries. Diamond's state-of-the-art scanning and imaging beamlines offer scientists non-destructive techniques, helping us understand how to preserve our fragile and precious historical objects.
Humans have been painting on the walls of caves for more than 40,000 years. These decorated caves have been found on every continent except Antarctica. The painted designs include handprints and abstract drawings containing dots and crosshatched lines and the well-known pictures of animals, some of which are now extinct. Studying these images offers insights into our distant ancestors' lives, but the pigments used also provide more concrete clues about the prehistoric landscape.
Researchers from the University of Reading used Diamond's Multimode InfraRed Imaging And Microspectroscopy (MIRIAM) beamline B22 to study 10,000-year-old pigments used in Neolithic wall paintings and designs from two sites1.
The first sample came from Çatalhöyük, a Neolithic proto-city in Turkey. The results showed that the red pigment contained obsidian, a natural glass formed from volcanic lava. Obsidian hadn't been found in pigments at Çatalhöyük before, and its use is unusual. The research team theorised that it was included for its reflective properties, to enhance the design in low light conditions.
The team found that the second sample, from Sheikh-e Abad in northern Iran, contained a mixture of minerals associated with a type of red clay known as terra rossa. Terra rossa is one of the most common types of clay, but it's not currently found at the site, which suffered massive flooding after being abandoned.
In 79AD Mount Vesuvius erupted and destroyed the town of Herculaneum in modern-day Italy. It also erased the local state-of-the-art data storage system - or did it?
The Institut de France is home to a collection of world-famous ancient artefacts, including two complete scrolls and four fragments from Herculaneum. If we could read this "invisible library", it would provide a wealth of information about life in ancient Rome. However, the intense heat of the eruption carbonised the scrolls into compact and highly fragile blocks.
In 2019, researchers carefully transported the scrolls to Diamond's JEEP (Joint Engineering, Environmental, and Processing) I12 beamline for investigation2.
Prof Seales from the University of Kentucky, and his team, used X-ray scans to "digitally unwrap" the scrolls, which are too fragile to be examined conventionally. After decades of effort, Prof Seales thinks this is the best chance yet to reveal the elusive contents of these 2,000-year-old papyri. Their findings will be published in due course.
More modern antiquities can also benefit from synchrotron studies. In medieval times, altarpieces and carved wooden decorations were often gilded with thin gold and silver foils. The artist would have glued these on using egg yolk, drying oil or animal glue, and would normally have protected the gilding with a varnish or resin.
Over time, the silver blackens or disappears altogether. Researchers studied the change to the metal foils in selected fifteenth-century artworks with different glueing agents, organic coatings, and conservation levels.
Using a combination of X-ray and IR microanalysis (in collaboration with ESRF BM16 and Diamond B22), they showed that the silver foil's conservation state is directly related to its exposure to the atmosphere, i.e. if protected by coating or not like in the painting cracks3.
There may have been a village near Oakington in Cambridge since the Stone Age. Archaeologists have discovered a substantial 6th-century Anglo-Saxon cemetery there, 18 of which contained brooches. One large brooch stood out, as it is a complex object, made from copper alloy with gilt and enamel decoration. However, enamel is not usually associated with Anglo-Saxon artefacts from this date.
Dr Duncan Sayer and colleagues from the University of Central Lancashire brought the brooch to Diamond to conduct a detailed study of its composition4. They used microfocus X-ray fluorescence (µXRF) on the I18 beamline to study the slight variations in the chemical composition of the brooch components.
Their results suggest that the brooch was made from recycled materials. The flecks of different material within the enamel are similar to a Roman enamelling method. Previously-used glasses and materials were probably ground together to form a new enamel mixture for this brooch, using a technique unknown amongst the continental Angles or Saxon. Nonetheless, the brooch is undeniably an Anglo-Saxon design. A survey of other Anglo-Saxon brooches from the area also found traces of enamelling, suggesting that this was a much more significant and localised phenomenon than once thought.
Cannonballs were always intended to be a disposable object. When King Henry VIII's warship, the Mary Rose, left Portsmouth in 1545, it carried 1,248 iron cannonballs. The Mary Rose fired on the French fleet from her starboard side, but as she turned, she listed and then rapidly sank, taking the rest of her arsenal to the seabed.
Once unearthed, iron artefacts are at risk from corrosion, a process that may accelerate in the presence of chloride. Over time, scientists have tried various conservation methods, but evaluating which one is best has been tricky.
The Mary Rose cannonballs offered a unique opportunity. They were relatively uniform when created but have been subject to different conservation methods and environmental conditions since they were recovered.
The research team used a combination of methods at Diamond including X-ray powder diffraction, absorption spectroscopy and fluorescence to characterise the effect of the different conservation techniques on the crystalline corrosion products, chloride distribution and speciation5. They used tomography to study where the corrosion products form and how they are distributed, and computed tomography X-ray diffraction (CT-XRD) to map the evolution of corrosion products in selected solutions. Access to Diamond’s long duration experimental facility enabled the team to assess iron and corrosion products’ reaction in solution over time.
Synchrotron X-ray techniques can differentiate iron corrosion products formed during treatments, even years later, giving us an unprecedented insight into the effects of conversation techniques on iron corrosion.
A scientific analysis of historical artworks can tell us a great deal about historical manufacturing practices and artists' techniques. This, in turn, can help with authentication, conservation and restoration.
Researchers from the University of Leicester are developing a non-invasive technique that is highly insensitive to the artefact shape and size, which means no surface preparation or sampling are needed. To understand the potential and limitations of the method in the scientific assessment of paintings, the team worked with Nicholas Eastaugh of the Pigmentum Project to use it to examine a test panel of forty oil-based paints used by artists in the 20th century and containing a variety of inorganic and organic pigments6.
The results show that the Energy-dispersive X-ray Diffraction (EDXRD) technique can extract a range of information about paint samples non-invasively and at high resolution. Ultimately, the aim is to develop the technique so that it can be used to analyse artefacts at their home locations.
Some of the cultural artefacts we now treasure were once little more than trash. Others, however, were built to last. York Minster is the second-largest Gothic cathedral in Northern Europe, built to dominate the city in medieval times. Its builders intended the cathedral to stand for countless ages, but they didn't foresee problems with atmospheric pollution.
The limestone in the structure is under attack from pollutants, including sulfur from acid rain and the particulates released from the combustion of fossil fuels. Under this assault, the exterior stonework blackens and slowly erodes, destroying finer details created by stone cutters in the middle-ages.
Scientists from Cardiff University, the University of Iowa (USA), and Diamond investigated the potential for using hydrophobic surface coatings (derived from Olive Oil) to protect the cathedral walls, using X-ray Absorption Spectroscopy (XAS) measurements on beamline B187.
Their work helped to understand limestone weathering and decay, and guided the development of conservation techniques for York Minster and similar historical buildings.
Rugose corals are important fossil corals that had a skeleton made of the mineral calcite and which were present millions of years ago. A team from Amgueddfa Cymru – National Museum Wales and Golestan University (Iran) brought a rugose coral sample to Diamond to study it using high-resolution tomography. This technique enabled the group to create 3D images of the rare fossil, without having to sample it destructively8.
The clear, detailed images confirmed that the fossil was a 462 million year-old rugose coral, five million years older than previous discoveries of this type.
The results demonstrated that this non-destructive synchrotron technique holds great promise for the "virtual dissecting" of fossils and could be set to transform palaeontological studies in the UK.
Decades ago, a fossilised spider-like creature was found inside a rock that was first discovered in France. Most of the animal’s body was completely encased in dense rock, and so palaeontologists were never able to classify the 305 million year old fossil until now.
A team from the University of Manchester used laboratory CT scanning to reconstruct an image of the creature, but in order to accurately classify it, the group needed to explore its anatomy in more detail. And so the group turned to high resolution synchrotron tomography: a technique that exploits energy waves to scan and determine the internal structure of an object9.
Scientists at Diamond’s Joint Engineering and Environmental Processing beamline (I12) were able to provide the exquisite detail required to allow close examination of the spidery animal’s anatomy. The group discovered a key difference between their fossilised animal and modern spiders: unlike regular spiders, the ancient creature lacked ‘spinnerets’: special organs that allow spiders to weave their webs. The animal has now been classified as an entirely new species outside the order of true spiders.
The surface of many Old Master paintings has been affected by the appearance of whitish lead-rich deposits, which are often difficult to fully characterise, thereby hindering conservation.
Painted in 1663, Rembrandt’s Homer is an incredibly valuable and much-loved painting. Like many Old Masters it has a long and eventful past, which has taken its toll on the painting’s chemistry. The test of time and environmental factors, combined with the painting’s history, caused a barely visible, whitish crust to form on the surface of the painting. This crust indicates that chemical reactions are occurring which could potentially pose as risk for Homer and other old paintings if not kept in stable museum conditions.
A team of conservation scientists from the Mauritshuis in the Hague and the Rijksmuseum in Amsterdam, University of Amsterdam and scientists from Finden Ltd, UCL and Diamond used the synchrotron to examine a paint micro-sample from Rembrandt’s Homer10. A technique called X-ray Diffraction Computed Tomography (XRD-CT) enabled them to investigate and understand the evolving chemistry from the painting surface and beneath.
They were able to show how the lead-containing paint had reacted with atmospheric pollutants including sulphur dioxide, which had formed the white crust disfiguring the painting. Using this information, conservators will now be able to further investigate this degradation process and identify the best treatments.
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