The first thing to do with our data was to distil it down into manageable chunks – this means that what looks like a lot at the time (we filled several DVD’s with data!) actually reduces to a few pictures and graphs – but this means we can now start to see the wood for the trees.

Here’s a little taster – but before I start, a small caveat. These are very early results, and the analysis may change as they are prepared to be submitted to scientific journals. This is important, as anything which goes to these journals is subjected to review by other scientists working in the same area, so they have to be right (or at least, our conclusions have to be justified, which is not necessarily the same thing!). So, this is what we think is going on at the moment, but this may change as we work things out.

Remember the blue pigment I showed you a picture of a couple of posts ago? Well, here’s what things look like if we zoom in more closely with better imaging. From left to right, we have a colour optical image of the region we’re looking at, what we see in green light after x-ray irradiation and what we see in infra-red light. (The images are all the same size, about 0.8x0.8 mm)

Colour optical image of rocks
[image © Paul Hatherley]

If we compare the pictures carefully, we see that the green light comes from the clear grains, and the infra-red from the blue (an exception is the grain near the centre, which seems to be giving green light – but look carefully – there looks to be a clear grain attached to it!). Remember, the green is from sand, and the infra-red from Egyptian Blue.

If we now look at how the light emitted changes as we change the x-ray energy, we get an idea of how the different minerals absorb x-rays, which tells us something about how the atoms are arranged. Here’s what we found if we target x-rays which interact strongly with the silicon in sand and Egyptian Blue. The green curve is what we get if we look at the green light (sand) and the red, if we look at the infra-red (Egyptian Blue). 

Graph showing X-ray results
[© copyright Paul Hatherley]

Don’t worry about the scales etc. The important thing is the appearance of the curves. The green curve shows two clear, sharp dips (don’t worry about the deep, broad dip). These show that the silicon atoms are arranged in an orderly, crystalline way. These dips are absent though in the red line (Egyptian blue), showing the silicon is less ordered – in other words, it looks more like a glass, which has no definite structure! This is a very telling result, since some other work indicates crystals of Egyptian Blue are present. Do we have a mixture then? Even more intriguingly, does this result tell us something about how the Egyptian Blue in this specimen was made?

Hmm. Perhaps how Egyptian Blue was made would make a good post – watch this space...

Paul.

About the author

In late 2007, Paul Hatherly joined Physics and Astronomy at The Open University as a key member of the HEFCE-funded Physics Innovations Centre for Excellence in Teaching and Learning (PCETL).

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Now the sadness. The SRS at Daresbury started work in 1981, and I did my first research here on molecular physics as a student four years later. I’ve had many programmes running here over the years on many topics, culminating in this work on Heritage Science. Sadly though, this will be my last time here. The SRS will be shut down for the last time later this year as many science programmes move to the new synchrotron radiation source, DIAMOND, near Oxford. It’s not all about the loss of a superb machine (which, frankly, is showing its age), but about the loss of community. Science is a human activity, and nowhere more so at places like Daresbury. I guess that’s what I, and many others, will miss most. No more chats over coffee, no more visiting other groups to “borrow” tools, tape, string or whatever, and perhaps worst of all, no more visits to the Ring ‘O’ Bells, the pub in Daresbury village!

In the Ring ‘O’ Bells – the Daresbury “watering hole”
[Photo © copyright Paul Hatherly]

Oh yes, Daresbury village – I haven’t told you anything about this yet! Well, to all outward appearances, it’s a normal small English village – a pub, a church, one main street and a handful of houses. Nothing remarkable until you look at the east window in the Church.

Part of the east window in All Saint’s Church, Daresbury
[Photo © copyright Paul Hatherly]

Recognise these characters? They are the Mad Hatter, the Mad March Hare and the Dormouse from Alice in Wonderland. Why here? In the mid nineteenth century, the vicar was one Charles Dodgson whose first son, also Charles, became a respected mathematician at Oxford. This Charles is better known as Lewis Carroll, the author of Alice in Wonderland! So here is Daresbury’s other claim to fame as the birthplace of arguably one of the most influential writers in English! Perhaps some of his ideas have rubbed off here? There frequently seems to be an “Alice in Wonderland” quality to some of the things that go on…

So one chapter is closing. I hope another will start soon, as we take our Heritage Science work to DIAMOND. There, we will be able to look even more closely at our materials, and get down to levels of detail not possible at the SRS. Another important aspect DIAMOND will give us – does all this analysis cause any lasting damage to the artefacts? Not just visible (cracks, melting, change in colour etc) but invisible – except under the microscope of synchrotron radiation.

We’re heading home now, but the hard work has just begun. Over my next few posts, I’ll take you through the distillation and analysis of our results, and hopefully give you a sneaky peek at some of the highlights.

Oh for a good night’s sleep now…  

Paul.

About the author

In late 2007, Paul Hatherly joined Physics and Astronomy at The Open University as a key member of the HEFCE-funded Physics Innovations Centre for Excellence in Teaching and Learning (PCETL).

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Our first target was some of the blue material that I showed you the other day. We identified some target x-ray energies, and looked at what light was emitted when the sample was irradiated. To give you a taster, here’s something hot-off-the-press! X-rays characteristic of silicon gave some very nice results, and have helped us identify the blue as Egyptian Blue (this is known to be a copper silicate).

Blue-painted Roman plaster at Daresbury in false colour. The blue background is an optical microscope image, and the coloured spots show light emitted in the strip of paint which the x-rays hit. To give a sense of scale, the picture is about 4mm across.
[photo © copyright Paul Hatherly]

In the picture, the green spots show where we had bluey-green light emitted by silicon dioxide – common sand! The red spots though correspond to chunks of blue material, and are where light in the far red and just beyond the red end of the spectrum (the “near infra-red”) is emitted. We now know that the blue contains silicon; more hard evidence for Egyptian Blue. This is rather rough and ready data, and over the next few weeks we will see this being refined into something that can be properly published. That’s another story, but for now let’s enjoy a rather pretty picture!

I promised to introduce you to some other people who do their research here. Here’s one of them, with the apparatus he’s using to look at fundamental structures of organic molecules. There is a tradition of international co-operation here, and Andrew Yencha from the University of New York at Albany has been working for many years with George King (Manchester University) and Michelle Siggel-King (Daresbury) on a wide range of topics.

Andrew Yencha from New York – Daresbury is an
internationally recognised facility!
[photo © copyright Paul Hatherly)

Hopefully I can catch up with some more people for my next post.

Things are really getting busy now – the equipment is working more or less smoothly, and we’ve refined our plan in the light of our discoveries, so there’s plenty to get on with in the next few days. I’ll make my next post early next week, and that’ll be the last from Daresbury. Where we go from there will be the next chapter in this story.

Until next time…

Paul.

About the author

In late 2007, Paul Hatherly joined Physics and Astronomy at The Open University as a key member of the HEFCE-funded Physics Innovations Centre for Excellence in Teaching and Learning (PCETL).

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The Roman Wall Plaster Team with a small part of the machine.
Top – Nigel Poolton. Bottom – Maria Gallagher (left) and Nicola Freebody (right).
[Photo © copyright Paul Hatherly]

So, on to the Daresbury machine, the SRS, itself. What's so special about this, and why do we have to drag ourselves away from our homes? Well, the SRS is one of a few machines in the world which exploits the phenomenon of synchrotron radiation. A good analogy to synchrotron radiation might be to think about a car going round a corner at high speed - the tyres squeal! In a synchrotron radiation machine, electrons (negatively charged components of atoms) are accelerated close to the speed of light in a circular vacuum tube, and kept moving in a circular path by strong magnets. Now, when the high speed electrons are forced to turn by the magnets, they “squeal”, but not in sound, but light. This light is synchrotron radiation. Why is this special? Light comes in many forms - optical, from a light bulb, lower energy infra-red, from heat lamps (also used in surveillance) and higher energy ultraviolet, in tanning lamps (and from the Sun!). But light goes further! If you go to lower energy than infra-red, you come to microwaves and radio, and, interestingly for us, if you go to higher energy than ultraviolet, you end up with x-rays and gamma rays. Normally, for each type of light, you would need a different lamp or source. Uniquely, synchrotron radiation has all energies of light in it, which is why people build these machines, and why so many people want to use them for so many purposes.

We now need to connect this advanced light source to our Roman material. What we will be doing is shining x-rays of particular energies on to our Roman paint. The energy from the x-rays will be dumped into the material of the paint, and eventually come out as visible light which we can easily detect. As we change the x-ray energy, we home in on particular types of atom in the paint, and as we look at the colours of light emitted, we learn about how the atoms are arranged in the material. So we don’t just learn about what is present, but how it is combined with other atoms. More than that, the apparatus designed by Nigel Poolton images the material through a microscope, so uniquely we can get all the information we need at different points on the surface - important, as we may have a mix of different paints - especially if the painters were ripping off their customers!

Better get on now, and get everything ready to roll! In my next post, we should have some first results, and I can show you some pictures. I will also introduce you to a few of the other researchers here, and tell you a little of their work.

Bye for now,

Paul.

About the author

In late 2007, Paul Hatherly joined Physics and Astronomy at The Open University as a key member of the HEFCE-funded Physics Innovations Centre for Excellence in Teaching and Learning (PCETL).

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Where is Calleva? On a map of modern day Hampshire, look in the north of the county near Basingstoke. You will find a small village called Silchester, which has a secret. Nearby this quintessentially English village is a vast wall surrounding a series of fields. The wall appears to be very old, and indeed, it is – it dates from the Roman period, and surrounds the remains of Calleva. There’s no town there now – unlike many Roman settlements such as Chester, and indeed London, but this is its great value. Without a history of development, the record of this Roman town is pristine and intact beneath the turf.

We now jump to the late 20^th Century, and to a team of archaeologists from the University of Reading excavating the Calleva site. Amongst their many discoveries, is a vast collection of plaster fragments which were once part of a wall in the Roman citizens’ house we met at the beginning. Interestingly, many of the fragments still have the paint attached and, although the damage is too much to allow any pictures to be reconstructed, the presence of the paint holds its own story. Of special interest, blue and green paints are present. Why are these special? Well, the Romans held these colours in high esteem. Some of the materials used to make these colours were rare or expensive (for example, Egyptian Blue was especially prized), and therefore reflected status – and the Romans loved status! The archaeologists now had a question. Were the citizens of Calleva using the best the Empire could provide, or were they using cheaper local products to “ape” the great imperial centre? Answers here would tell us a lot about the social, economic and political environment of this part of the Roman Empire.

A fragment of blue-painted wall plaster from Calleva, about 1 inch
(2.5 cm) across – the real McCoy or something cheap?
Or is the answer more complex?
[image © copyright Paul Hatherley

But how to answer the archaeologists’ question? With my research interest in Heritage Science, it wasn’t long before I got wind of the problem, and started talking with the archaeologists. I quickly realised that I could use some methods in physical science, which had originally been developed for semiconductor and material science to resolve the issue, so I wrote a request to carry out a series of experiments on the paints. Who to? To the Synchrotron Radiation Source, one of the Science and Technology Facilities Council (STFC) major research laboratories located at Daresbury near, wait for it, Warrington! This was about one year ago now, because my request to use this facility had to be reviewed scientifically and technically, and this takes time. So, on returning from our summer holiday, I found a letter on my desk informing me my request had been granted – but this is not the end of the story. Many other scientists, from physicists and biologists to geologists and materials scientists had also applied, and had their experiments approved, so I had to wait my turn, and my turn is next week!

We are now in the Final Countdown before our experiment, so the last week has been frantic – as team leader (yes, this will be a team effort), it is my job to make sure all paperwork (safety forms, team briefings, booking accommodation – we’re away from home for a week) gets done. Oh yes, and finalising a plan for the week so we make the best use of our time.

So, there’s a partial answer to the question in my first post – A research team from the Open University will be investigating Roman paints on wall plasters at a major UK research facility near Warrington.

I’m going to relax this weekend and charge my batteries. My next post will be from Daresbury early next week where I will tell you some more about this facility and introduce you to the team.

Cheers for now,

Paul.

About the author

In late 2007, Paul Hatherly joined Physics and Astronomy at The Open University as a key member of the HEFCE-funded Physics Innovations Centre for Excellence in Teaching and Learning (PCETL).

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My name is Paul Hatherly, and I’m in Physics and Astronomy at the OU and along with my teaching in many areas of experimental science, I am building a research programme in the fascinating area of Heritage Science. What is this? Well, there’s no single definition, but for our purposes, it’s applying and developing methods in physical science to questions of art, archaeology and conservation. For example, you are probably aware of the idea of carbon dating, where scientists count the small number of (naturally) radioactive carbon atoms in an artefact to determine the age. There are also geophysics techniques which, by revealing sub-surface features, can help archaeologists dig in the right place. But there’s more than that. How can we tell what an artefact is made of? How can we tell how it was made in the first place? Where did the materials come from? Can we do all this without damaging or destroying the artefact? The questions are endless. But finding out about an artefact doesn’t end the story. Conservation and preservation for future generations to enjoy and study is vital, and Heritage Science has an input here too. Can we be sure that a conservation method successful now won’t, over decades, destroy the artefact or, maybe worse, so affect the artefact that studying it is worthless? Heritage Science is already helping in this area in, for example, helping the long-term conservation of the ships the Mary Rose and the Vasa.

Over the next few weeks, I’ll be telling you about some of my work in Heritage Science, and hopefully finding a few answers to the question we started with. In the course of this quest, I’ll be taking you on a journey to some of the most advanced science facilities in the country and meeting the vital people who keep it all running. We will see how a physics technique developed to study nanostructures in semiconductors can be used to try and sort out what Roman painters and decorators were up to in Britain almost 2000 years ago, and perhaps get inside the minds of the artisans and their customers in a way not possible before.

Right now though, I’m approaching the end (or is it the beginning?) of a process started almost a year ago; a process from an original idea, selling that idea in the right quarters, carrying through the idea and ultimately telling the world of our discoveries. I’ll tell you more about this in my next post later this week, and I’ll explain the Warrington connection.

Until then…

Paul.

About the author

In late 2007, Paul Hatherly joined Physics and Astronomy at The Open University as a key member of the HEFCE-funded Physics Innovations Centre for Excellence in Teaching and Learning (PCETL).

Subscribe to Paul Hatherly's posts