Meera Senthilingam: Welcome to the Diamond Light Source podcast. In this edition we look into the field of cultural heritage to see how scientists at Diamond are discovering new ways to keep our history preserved. We’ll be finding out how synchrotron light can be used to discover new ways to conserve historical treasures such as the Mary Rose.
Jen Hiller: What we tend to look at is either where elements are in a material or the structure of the material itself. So it will either have something to do with conservation and the way things are surviving or the way they are being preserved – something like the Mary Rose where they are trying to understand how their conservation treatment is really working.
Meera: Jen Hiller will be discussing the role of cultural heritage at Diamond. Plus, we learn how scientists are trying to solve a mystery in the art world.
Nicholas Eastaugh: It certainly occurs in paintings. It’s an effect where you get, say, a large area of red paint produced with vermillion but it can go from a sort of grey to a black colour and it can be quite patchy but it’s very sort of disfiguring to the appearance of the painting.
Meera: Nicholas Eastaugh will explain how his team are looking into this phenomenon to prevent it ruining major works of art. All this plus the latest news and events from festivals that took place over the summer. I’m Meera Senthilingam and this is the Diamond podcast.
Voiceover: The Diamond Podcast: for more information look us up online at www.diamond.ac.uk/podcast
Meera: Now before we take a look at how Diamond is delving deep into the world of cultural heritage, let’s join Sarah Bucknall from Diamond’s Communications team to find out what Diamond’s been up to over the summer.
Sarah Bucknall: We’ve had a really busy summer actually. At the end of June and early July we were at the World Conference of Science Journalists and the Royal Society Summer Exhibition, and they were both in London. It was the first time the World Conference of Science Journalists came to the UK and Diamond sponsored the official reception through lightsources.org, along with some of our fellow synchrotrons in Europe and one of them in America. And we also did a news briefing at the French Institute in South Kensington and that was with the French synchrotron Soleil and Elettra in Italy. One of our users, Dr Mark Sanderson from Kings College London, spoke about the recent results of his research into anti-bacterial drugs that are used to treat the bacteria that are responsible for things like pneumonia and meningitis and about how the bacteria can sometimes develop a resistance to these drugs.
Meera: And as well as these press briefings you also organised a few trips at the conference didn’t you?
Sarah: Yes, we put on a post conference trip as part of the week’s events, so a number of the science journalist delegates came to Oxfordshire to visit four of its large research facilities. So that was the Joint European Torus, or Jet at Culham, the Central Laser Facility and Isis at the Rutherford Appleton Laboratory and of course Diamond. And also, thanks to the University of Oxford the evening was rounded off with an informal reception at Magdalen College, where the Professor for the Public Understanding of Science Marcus du Sautoy gave a speech about the importance of science communication
Meera: So it sounds like you had a lot of interesting events taking place at the World Conference of Science Journalists, but you mentioned that also that week you were at the Royal Society Summer Exhibition?
Sarah: That’s right, we were involved at two of their stands, we had textile panels from our Design for Life science and art project on display. This was a project that was carried out a couple of years ago that was carried out in collaboration with the Oxford Trust and the Oxfordshire Federation of Women’s Institutes, the WI. The WI ladies met with a number of Diamond scientists to debate science research priorities, and as a result they produced 30 panels of textile art which depict the viruses and diseases that are studied at Diamond. So we had those on display at the exhibition. There was also a stand on particle accelerators that we helped out on which aimed to show the importance of these machines and also how researchers are looking into improving their performance.
Meera: So obviously the Communications team have been very busy out and about at all these events and publicising Diamond’s work, but what was actually happening back here at the fort at Diamond? So how are the new beamlines getting along?
Sarah: The Phase II beamlines are coming on really well. At the end of June the first turf was cut to make way for I13, and that’s an imaging and coherence beamline, and when complete it will stretch 250 metres away from the main synchrotron building and it will be used for coherence and tomography experiments. For example, researchers will be able to create three dimensional images of objects in extremely minute detail, and the first users are expected on this beamline in 2011.
Meera: Now as well as all these events taking place at the beginning of summer at the end of summer, in September you had things going on at the British Science Festival?
Sarah: That’s right, we were there all week and we had a stand to basically talk about Diamond in general and synchrotron research. We were also collecting stitches for the World’s largest diffraction pattern.
Meera: And as well as all this you’ve also got another Inside Diamond day coming up?
Sarah: Yes, our next Inside Diamond Day is on Saturday 3rd October, people are welcome to register and they can do so on our website.
Meera: And as well as the actual Inside Diamond day on the Saturday, you’ve got some educational trips organised for the Friday?
Sarah: That’s right, we’ve got over 200 A-level students visiting the facility, ad they will meet our scientists and engineers as well. We organised this event in response to the many visit enquiries we receive from schools and colleges throughout the UK who want to learn more about synchrotron science and visit a working facility. So as usual it’s busy and exciting here at Diamond and we’ve got lots to look forward to!
Meera: Thanks Sarah. That was Diamond’s Sarah Bucknall who’ll be back with more of the latest news and events from Diamond in the next podcast. Now this month we’re digging deep into the world of archaeology to learn how scientists are helping to preserve our historical treasures. So first, we meet Diamond’s in-house archaeologist Jen Hiller down by the synchrotron to find out just what cultural heritage science involves.
Jen Hiller: Well cultural heritage at Diamond tends to focus on material characterisation or material degradation. So the beamlines that are involved in it now are primarily the non-crystalline diffraction beamline or the X-ray fluorescence or EXAFS beamline, but there will be at least three more that will be involved in cultural heritage projects over time as they come online. What we tend to look at is either where elements are in a material or the structure of the material itself, so it will either have something to do with conservation and the way things are surviving or the way they are being preserved, so something like the Mary Rose where they are trying to understand whether their conservation treatment is really working or something like what we look at here, which is how collagen-based materials like parchment, leather and bone degrade over time and what kind of ways we can conserve them or gather all the information that we can from them as they degrade.
Meera: So first of all you’ve mentioned that it’s possible to look at elements within various samples that need to be looked at, so how is that possible here and how does that help cultural heritage?
Jen: It’s a technique called EXAFS that localises elements by using a tuneable energy or a tuneable wavelength coming out of the monochromator – something you can really only do at a synchrotron source – laboratory based sources are fixed wavelength, so by changing the wavelength they excite different molecules at different times and each element will fluoresce in a different way, which gives an idea of where elements are localised. And the really wonderful thing that we have here is a beamline that runs that technique with micron scale resolution so about a hundred times smaller than a human hair, which makes it easy to look at very localised areas within a structure to try to understand how far things are spreading, or to look at very tiny things, like looking at how far ink penetrates into paper, how a single bit of pigment on the surface of a painting can be affected by its environment and the conservation treatments applied to it.
Meera: So that’s work done at the Microfocus Spectroscopy beamline, but the beamline we’re sitting at now is the non-crystalline diffraction beamline. So what takes place here, is this where you look at structure of materials?
Jen: We do look at structure of materials, and we look at the structure of all kinds of materials, but preferably things that either won’t grow into a crystal because they are already partially ordered, or that you don’t want to have as a crystal because you’d rather look at them in their native state. So this beamline actually covers about 60% physical science and about 40% life science, but a lot of what we do in life science is look at collagen-based materials, and there are archaeological and cultural heritage objects that are basically collagen-based materials and certainly the best example that we’ve had and certainly the most publicised example that we have had here are parchments. Parchment is most of European written heritage, but it’s type 1 collagen, it’s animal skin, so it’s really the same as the type 1 collagen anywhere in the human body and type 1 collagen is present everywhere – in bone, in cornea, in skin. It’s holding all of your bits together really! So that material, for all we understand of the structure of that material, and all the biologists that we have that study that kind of material to understand how to heal it, how to repair it, they can also look at these documents, these very precious documents in some cases – we’ve had fragments of the Dead Sea scrolls, groups have looked at the Magna Carta, to try to understand how that collagen structure is degrading.
The problem with collagen is that as it degrades it turns into gelatine, and gelatine is really the same as when you boil a soup bone for too long and it goes to that horrible jelly sort of sludge – that actually happens to parchment as it changes over time, and if the native collagen structure is lost then conservation treatments can destroy the parchment very quickly, especially if you get it wet, so they are very susceptible to floods, they are very susceptible to humidity, cleaning, you name it, so a lot of people are trying to understand how best to preserve parchments for as long as possible because it’s so much of written heritage. But also to understand how they are manufactured, the very ink that was used to write on them, all of those factors can also affect their preservation so the non-crystalline diffraction beamline right now mainly impacts cultural heritage in that area.
And the really nice thing about bringing something like parchment here is that it’s very fast to take the measurements, the technique is non-destructive and we’re quite gentle. The X-rays are actually, believe it or not, quite gentle to historic parchments so you can take it back out. We also have the advantage of very high spatial resolution so we can look at tiny, tiny fragments of things, so people do bring things here that have been micro-sampled, cut little tiny slivers out, things that would be almost impossible to analyse with any other source because you need a very, very small beam.
Meera: So just how small do these samples get then?
Jen: They can be sometimes only a few mm across, and if it’s something as small as 1mm across then actually we can look at this in cross-section, so we can look at the way the surfaces are differently affected from the middle of the parchment too, 1 mm actually allows us to view it from both sides.
Meera: So these two beamlines, they are the main ones involved in cultural heritage at the moment, what other ones have you got coming up and what, as a result of those, what potential new avenues will there be for cultural heritage research?
Jen: There are at least three. There’s the infrared beamline which is coming online quite soon, and they can look at things like pigmentation, there’s an idea to look at liquid residues in pots. There’s the powder diffraction beamline and that’s actually online now, I don’t know if they are doing any cultural heritage work at present but that looks at more traditional X-ray diffraction, so it can look at composition of materials. And then there’s the tomography beamline which could look at, you know, repairs to larger artefacts, things like almost entire museum bronzes, so there’s at least those three and it’s down to the creativity of the users whether the other ones get exploited as well for cultural heritage.
Meera: Diamond resident archaeologist Jen Hiller, explaining how X-rays can be used to examine minute samples of historical gems such as the Dead Sea scrolls to investigate their structure and to develop new methods of preservation.
Voiceover: Did you know that Diamond is made of over 2,000 tonnes of steel? That’s the same as 300 London buses.
Meera: You’re listening to the Diamond Light Source podcast, and in this edition we’re looking at the role of science in cultural heritage. Now we’ve had an outline of the role synchrotron light can play in our cultural heritage, so now we meet the scientists behind the samples to see what they’ve discovered so far. Coming up, we’ll be learning how masterpieces such as Turner’s paintings are randomly changing and what scientists are doing to find out more about this and stop it. But first we go out to sea, to hear the story of the Mary Rose and how Mark Jones of the Mary Rose Trust is going about keeping this iconic ship in its best condition.
Mark Jones: The Tudor warship Mary Rose was built between 1509 and 1511 in Portsmouth, and she sailed successfully for almost 35 years. And she was the very first purpose-built warship in the Royal Fleet. On a fateful day in 1545 she was about to engage the French invasion fleet, she sunk in about 14 metres of water. And there she lay undisturbed for almost 437 years. She was recovered in 1982.
Meera: Once the ship was recovered what was initially done to preserve it?
Mark: The first thing we did of course was to spray it with seawater. She was then taken into a dry dock and within the dry dock we built a ship hole. Within the ship hole we built an environment in which the ship timbers were sprayed constantly with chilled fresh water to reduce the activity of microbes such as bacteria and funghi. In addition to that we cleaned the surface and in addition we started to wash out iron sort of compounds that had actually penetrated into the wood structure. And these iron compounds came from corroded cast iron guns and also iron fittings such as nails and bolts which held the ship together.
Meera: And now you’re actually probing down and looking into the actual cells of the wood and the timber to find new ways to preserve it even more?
Mark: Well since 1994 she’s undergone a process of preservation involving a water-soluble wax called polyethylene glycol, but apart from that we’re very interested in the detailed chemistry within the wood itself. We’ve used all sorts of techniques to analyse the condition of the wood, Fourier Transform Infrared Spectroscopy (FTIR) to look at changes in the chemistry to the cell, to the material in terms of cellulose, semi-cellulose and lignum. In addition to that we are finding a number of compounds present in the wood such as iron and sulphur compounds.
Meera: So how are you looking down now into the wood cells to now to look at the interactions of the iron and the sulphur in these cells?
Mark: We have been very lucky really to work very closely with government scientists to look at the current preservation treatment of the Mary Rose from two points of view. First of all stabilisation but also to prevent these iron and sulphur compounds forming acids in the timber in the future. To achieve this we’ve got to have a detailed understanding of the chemistry of both these compounds and the interactions between the two, and what we are trying to prevent is the production of sulphuric acid in the timber due to the oxidation of iron sulphur compounds such as iron sulphide which over time will form sulphuric acid.
Meera: And so which beamline at the synchrotron are you using and how is this helping you to visualise the cells and the interactions of the iron and the sulphur?
Mark: Well we’re using station I18 and we have been able to use X-rays to probe the atomic structure of these compounds and the interactions between the two compounds such as iron and sulphur. So we’ve identified the different types of sulphur compounds and we’ve also used the station to identify the locations of these iron and sulphur compounds. We’ve also identified deep in the ship timber organo-sulphur compounds such as cystine, cysteine and thiols. And these are linked into part of the cell wall which we call the middle lamellar. Which is very rich in lignum.
Meera: So having now identified all of these different compounds, what can you do with this information to then help preserve the ship a lot better?
Mark: We are developing ongoing treatments to supplement the polyethylene glycol treatment which the ship is undergoing at the moment to stabilise these iron and sulphur compounds in the wood. We’re trying to wash out as much as we can and anything we don’t get out we’re trying to make them inactive.
Meera: And so what are the actual treatments you’ve come up with?
Mark: One is called calcium phytate which has proved very successful in the removal of iron sulphur compounds from archaeological wood. In addition to that it also acts as an anti-oxidant, which prevents any further reactions to any iron sulphur compounds that remain in the timbers. We think we’ll introduce this particular chemical to the spray system and this will form part of the final treatment for the ship timber. So we’ll have stabilised it using polyethylene glycol, removed substantial amounts of iron compound using calcium phytate, but putting in more calcium phytate in to remove anything else that still remains inside the wood from developing into sulphuric acid.
Meera: So the real problem, is really this sulphuric acid, this is what you want to prevent?
Mark: Yes, which can then destroy the cellular structure of the wood cell wall.
Meera: Coming up with these various treatments to absorb the iron, is there any risk of these having adverse effects on the timber?
Mark: Well that’s a very good question. One of the problems of course when you add a new chemical to the wood is what’s going to happen long-term to this chemical. Apart from finding out a suitable treatment is to look at the long-term effects on the well-being of the ship itself. So in addition to finding these new treatments we need to find the effects of these new treatments over time, whether these can be converted either by bacteria or by oxidation, reduction mechanisms in the wood into harmful chemicals. So we’ve got to make sure that they don’t.
Meera: So how are you going about doing that, are you just putting samples on small bits?
Mark: Yes, we take test samples and we do lots of laboratory experiments, and then we take these samples to Diamond and using these facilities we’ve been able to look at the different chemistries at the cellular level, which is fantastic and which you cannot do in any university laboratory.
Meera: Mark Jones from the Mary Rose Trust explaining how an understanding of the wood in the Mary Rose and its components can help target better treatments for its preservation. Now it’s not only the nautical world that’s being probed by cultural heritage science, but also the art world. For many years a mystery has perplexed artists and art historians the world over, as certain masterpieces have begun changing in appearance. The pieces involved are where the red pigment vermillion has been used. This pigment is extracted from the mineral cinnabar, and to find out more about the use of this colour and why these changes have been happening I met Nicholas Eastaugh from the Pigmentum Project.
Nicholas Eastaugh: Cinnabar is essentially mercury sulphide, the synthetic version that’s know as vermillion. Rather than use a mineral that could be impure, if you take the mercury out of the cinnabar you can then recombine it with sulphur to form vermillion synthetically, and you get this pure bright red material which is very nice to paint with. In essence you’ve got three materials that might be used by artists: there’s the cinnabar mineral itself, and then two forms of a synthetic product, they are all mercury sulphide, they are all red but they have slightly different properties.
Meera: What forms of historical art then have used this vermillion?
Nicholas: Artists use this pigment for all sorts of painting purposes and you can find it in everything, from an easel painting in the National Gallery through a piece of sculpture like the Chinese terracotta warriors to a wall painting that you might find in Pompeii.
Meera: So you have some samples of cinnabar here…
Nicholas: Yes, I have two different samples of the cinnabar mineral here. Both are from quite famous historical sources, one in particular, Spanish cinnabar and another one that’s actually from Italy. We know that these were both used historically by artists as sources.
Meera: Now looking at one, they look very different, one essentially has a darkened coating around it, whilst the other appears to have more ash with it.
Nicholas: Yes, so it’s partly to do with the geological context with these, but also probably with this sample from Spain you’ve got some discolouring of the mercury sulphide itself which is essentially the research that we’re trying to do. Just what is this darkened material and how does it occur? It certainly occurs in paintings, its an effect where you’ve got say a large area of red paint produced with vermillion but it can go from a sort of grey to black colour and it can be quite patchy, but it’s very disfiguring to the appearance of the painting.
Meera: And does this happen in most paintings that vermillion has been used on?
Nicholas: No, it only happens in certain circumstances and it’s these circumstances we’re interested in, just why it happens sometimes but not always.
Meera: And so how have you gone about looking into this?
Nicholas: We can approach these kind of problems in various ways, one can look at the paintings that it’s happened in, what kind of context they come from, is it paintings from a certain place and time, is it an effect perhaps from the atmosphere, both where the paintings were produced or where they have subsequently been displayed, but we’re interested in the chemistry of it.
Meera: What are the thoughts so far on why it does change from red to black?
Nicholas: In fact there are a number of theories that have been put forward. In certain circumstances you could take a bright red piece of cinnabar from the ground and into the light and it would really quite rapidly change into black, and people were suggesting things that it might be like small amounts of mercury forming on the surface, and that in thin layers can appear black. Other theories have been to do with the fact that there’s a very closely related mineral structure meta-cinnabar, so not cinnabar but meta-cinnabar and meta-cinnabar happens to be black. So is it, in this case, that there is a conversion going on, in the crystal structure between the red cinnabar and the black meta-cinnabar. Then there is another possibility, that these are generally quite interesting compounds chemically anyway, that they are related to a group of semi-conductors that happen to be responsive to light in the infrared. It’s possible to modify the semi-conductor properties of mercury sulphide so that it shifts from being a red colour to a black colour.
Meera: So that’s quite a few theories then as to why that could be happening. What have you been looking at so far with the use of synchrotron light to try and figure out which of these theories it is?
Nicholas: Synchrotron radiation allows us to apply a number of different sorts of investigation. Probably a key thing is we can look at very, very small samples, because you have an intense beam of radiation. If we do take samples from objects we don’t need very much, and for a valuable object that’s highly desirable.
Meera: Yes, I can hardly imagine that the owners of these paintings wanting large chunks taken out!
Nicholas: Well they are quite reluctant to say the least. But also there are techniques we can use to look at the chemical structure inside, you can even follow the process of alteration, so if you’ve got a reaction taking place you can monitor it using synchrotron techniques, but we’re interested really in changes to the crystal structure, so like a slight change in position of sulphur with respect to mercury. And then again we’re interested in very small amounts of trace elements that may be present that act as factors that can sort of induce this conversion, particularly things like the presence of chlorine has been suggested in the past as a mechanism that can promote this blackening.
Meera: Which beamline at Diamond do you use for this and how does that help you see the position and location of these elements?
Nicholas: We’ve been using beamline I18, the microfocus X-ray source that allows us to do this detailed elemental mapping samples so we can get down to very high spatial resolution, but we can also run these techniques to allow us to look at the actual crystallography of the cinnabar. Meera: And I guess though that the big question is, what have you managed to find so far?
Nicholas: Ah, that’s the $64,000 question. Out of the various possibilities one of the things we have been looking into especially closely is the presence of chlorine. That’s been found as a potential mechanism in oil paintings in Pompeii, but we’re looking quite seriously now at these semi-conductor properties, it’s a kind of obvious mechanism if one starts to look at those sorts of chemical structures, that its possible to get these kind of shifts from red to black. But we need to do further work at this stage to pursue that. We won’t necessarily find that in all circumstances it’s the same mechanism that is applied, the sheer fact that there are a number of proposed mechanisms for this that strongly suggest that in different circumstances different methods can be operating.
Meera: Nicholas Eastaugh from the Pigmentum Project discussing the possible reasons such as painting by Turner are turning in colour, and like many pieces of art, it’s a work in progress. Now that’s it for this edition of the Diamond podcast, but make sure you join us again in November when we’ll be back with more of the latest news and discoveries from Diamond as well as a look into the Earth Sciences, ranging from earthquakes to meteorites, to discover just what synchrotrons can tell us about the universe on the planetary scale. In the meantime if you have any questions about Diamond, or the research taking place there, the email address is firstname.lastname@example.org. Thank you to Sarah Bucknall, Jen Hiller, Mark Jones and Nicholas Eastaugh. I’m Meera Senthilingam, thank you for listening and see you next time.
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