Well, it’s been a few weeks since my last post to this blog, and perhaps you’d thought I’d disappeared. Far from it! On getting home, I managed to get my good night’s sleep, but then it was time to play catch-up with all the work (some boring, some interesting) that didn’t get done whilst at Daresbury, and apply for time at the DIAMOND light source. I have also been taking a preliminary look at our results, and wow! It looks like we can draw some interesting conclusions.

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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Mixed feelings at the end of this run. The pressure of working on facilities like this is immense. The facility runs 24 hours a day, 7 days a week, and costs thousands of pounds a day per experiment. You therefore have to squeeze as much out as you can in the short time available. Imagine the relief then when it’s all over and you can get back to a normal life.

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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The run is well under way now. We’re well under way, and we have the first batch of data under our belts. There were, as always, a few early teething troubles and glitches on the first day – sticky motors and loose wires – but nothing ingenuity and gaffer tape couldn’t fix!

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).

Subscribe to Paul Hatherly's posts