Sunday, 11 January 2015

The Physics of Heritage: looking inside

There is, or so I gather from my colleague Chris Pickvance, a rare item of furniture in Kent: a wooden chest with metal bolts buried under a wooden cover. There is great interest in being able to generate an image the bolts non-destructively (i.e. in situ). In Chris’ own words:  “I have been researching a group of medieval chests c1300. One has an intact long sliding bolt used to secure the lid. Only a handful of these survive in England and they are all concealed under long wooden covers. No one has seen an image of one, though there is a photo of an uncovered bolt in Germany. Hence, it would be path-breaking to be able to see what is hidden away. The bolt is about 3 feet long. Whether 'seen' from front, back or above it would be through the thickness of the wood.”

In the run-up to Christmas I had to admit that I’d drawn a blank in terms of finding equipment and expertise locally that could be used at the site of the artefact and have therefore started to caste the net a little wider. This has included contacting a friend and colleague at the Mary Rose Trust – see below. If you have any good practicable ideas then do please get in touch.

I’m not entirely sure why Chris contacted me initially, but this isn’t the first example of an interesting ‘random’ contact. (He has since pointed out that, in sociology, links such as ours are referred to as ‘weak ties’, and that there is a debate regarding their importance: all I would say in this instance is that I’m glad the ties exist.) For instance, until it was disbanded – sensibly, in my opinion – during a major overhaul I had the great pleasure of being the ‘tame scientist’ on Canterbury Cathedral’s Stained Glass Committee. This particular bit of serendipity came about entirely on the basis of someone bumping into me at work and hesitantly using those all-too-common opening words “I don’t suppose you’d be interested in …”. Whatever its genesis, I ended up having a golden opportunity to learn about what was to me an entirely new form of glass science, technology and art. Not only did I get to see examples of stained glass windows dating back to the Middle Ages with the sort of perspective denied to a tourist – high up in the galleries of the Cathedral building – but even more exciting were my visits to the Glass Workshop (here). At that time, they were expertly led by Sebastian Strobl (who later moved back to Germany to continue his work there). However, my longest, and continuing, contact there is with his talented successor, Léonie Seliger, who has not only opened my eyes to new realms of understanding and appreciation in the context of design, fabrication and conservation but has also shared with me a few of the many unsolved puzzles that cannot help but draw one in. If only I could figure out how to help solve them …  (You’d have seen Léonie in episode one of the recent BBC documentary series on Canterbury Cathedral: it’s currently still on iPlayer, although I suspect for a short while only). We’ve also found ourselves working together in a couple of exciting educational/public engagement projects. In one of these we contributed, in one way or another, to a new book in the growing series of excellent volumes by my friend Martyn Barr: this one’s entitled Paintings in Light (here).
Léonie, Martyn and me at the book's launch.
Another project was with my old friends in the Learning team at the Turner Contemporary gallery (here). As part of a longer project with a group of young people from NE Kent, who were supported through the challenge of making a film on the theme of ‘colour’, we spent several hours with them at the Cathedral (‘topped up’ with a recorded Q&A session a few days later) talking about light, colour and glass. Their short film is available here and there’s a bit of explanatory text here.
Léonie revealing the delights of stained glass using the Cathedral's Glass Workshop light table.
The other ‘historical’ example started way back, perhaps eight years ago or thereabouts, when a chemist colleague of mine, Alan Chadwick, and I were asked to help conservators at the Mary Rose Trust (see here) get to grips with a key problem regarding the preservation of archaeological marine timbers. This was associated with the fact that, buried for centuries under the sewerage-polluted silt of the Solent, the remaining timbers of this favourite warship of Henry VIII became rich in sulfur compounds. Once the ship was raised, these compounds oxidised; either by piercing the cell walls as crystals grew or by forming sulfuric acid and degrading the timber that way, the end result represented a serious problem. My involvement, through students attached to my research team, amounted to understanding this process at an atomistic level – and in particular, revealing the role of iron as a catalyst to some of the reactions (published here  if you want a copy of the full paper, let me know).  The project became more chemistry than physics afterwards, and it was Alan who carried the work forward. An unusually talented early-career postdoctoral researcher in Alan’s team, Ellie Schofield, went on the assume a leading role in the Mary Rose conservation programme (see here and here).
Using the world-class Diamond Light Source, we were able to study in detail both the position and the chemical state of the key elements in this game (sulfur and iron) and to do this with a resolution that enabled us to map all of that onto the cell structure of the timber itself. Here is part of the team in action at the I18 beamline at Diamond, with local beamline scientists, together with examples of timber cores and their original locations.

All of the above represent, in a way, the ‘hobby’ side to what I do. It’s rather nice to be able to engage in such hobbies.

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