Secrets from the X-ray lab
You may be surprised to hear that the British Museum has a cutting-edge X-ray imaging laboratory located four floors underneath the Museum. Using both traditional and innovative methods and equipment, scientists – including me – are able to answer questions that help with the interpretation and understanding of objects in the collection, including:
- How old is it?
- Where does it come from?
- What is it made of?
- How was it made?
Here are six such objects with secrets that X-ray technology has helped reveal.
One of the star objects of the Albukhary Foundation Gallery of the Islamic world is this ewer (large jug) from Herat, modern-day Afghanistan, with beautiful birds surrounding the collar. With X-ray CT scanning (shown on the left above), we were able to determine how the birds were made. The X-rays can be very high in energy and are therefore very helpful for looking through metal objects such as this.
By rotating the ewer while taking images, we can see the inside from all angles, allowing us to make a full 3D picture (which you can find out more about in this Twitter thread). Since the ewer is 40cm tall, I scanned it in two halves, top and bottom, then stitched the two halves together to give the result in the first image.
In the X-ray image above, we can see the silver inlaid design (it appears brighter because silver is denser than brass and so absorbs more X-rays) and various solder attachments. But what about the birds’ heads?
To answer this question, we can go through the 3D picture of the ewer slice-by-slice – click to play the video above. On the right-hand side here, you can see that the bird head on the collar is a white outline, continuous with the body of the vessel (the handle is completely solid).
The birds’ heads, thought to be parakeets or pheasants, were made by hammering outwards from the inside of the vessel and were not made separately and stuck on, as originally thought! It is clear that incredible artistry and skill was needed to make this ewer.
In the ancient Near East, clay tablets were inscribed with text called cuneiform, as well as clay envelopes to hold letters or important documents. With X-ray CT imaging, we were able to virtually strip back the clay envelope surrounding this cuneiform tablet, allowing us to read text that hasn’t been seen in over 4,000 years – without damaging the object!
With X-ray CT imaging, we were able to virtually strip back the clay envelope surrounding this Cuneiform tablet, allowing us to read text that hasn’t been seen in over 4000 years – without damaging the artefact @britishmuseum @JonTaylor_BM pic.twitter.com/FkJTNiQCwa— Dr Dan O’Flynn (@danoflynn) December 21, 2017
The X-ray scans revealed the following text, translated by curator Jonathan Taylor:
2,427kg wool, as rations for the men of (the village) Gaka, under the supervision of the chief minister, via (Mr) Shesh-Utumu, from (Mr) Aradmu, governor of (the city) Girsu, have been withdrawn.
(Sealed with) the seal of (Mr) Babati.
Year Shu-Sin became king
By itself this information may seem insignificant, but it gives a valuable insight into the economic life of ancient Mesopotamia.
At the British Museum, we normally use X-ray imaging to look inside 3D objects, but it can also be effective on some more 2D objects including paintings and textiles. This Tibetan thangka depicts a Tantric teacher, or Mahasiddha (‘Great Accomplished One’) called Saraha, and was discussed in our blog about its conservation treatment here.
Conservation of the thangka was carried out in the Museum by conservators Alice Derham and Teresa Heady, and colour scientist Joanne Dyer to see if we could learn anything about the painting process.
Joanne identified paints containing gold, lead, mercury, iron and copper on the thangka. X-rays are good at detecting these heavy elements on carbon-based backgrounds – such as cotton or paper – so we hoped to be able to see them in an X-ray image.
The X-ray image below shows details of the Mahasiddha Saraha. A reworking of the gold lines radiating from the Mahasiddaha Saraha can be seen, as well as brushstrokes from the application of red paint.
In 2019, the Museum worked with Border Force to identify and return a number of heads of Buddhist sculptures from Afghanistan that were damaged by the Taliban and illegally trafficked to the UK (read more here).
CT scans revealed how the heads were made and scientific analysis showed that the red and yellow pigments found on the sculptures were made from common iron-rich ores.
An X-ray CT scan of the heads revealed a two-layered construction. Firstly, a coarse clay was used to roughly model the shape of the head. Afterwards, the face, hair and headdress were overlaid with a finer and more compact material which was then painted. The rediscovery of the sculptures was a good opportunity to conduct this work and we are very grateful to the National Museum of Afghanistan for permitting us to do so.
Bronze age axe mould
This copper alloy mould came to the X-ray lab through the Portable Antiquities Scheme, which registers finds of treasure in the UK. This fascinating object is a 3,000+ year old Bronze Age mould for making palstave axes from southern England. The X-rays revealed the extent of the partially visible cracks in the two halves, and corrosion (seen as small dark circles on the images).
3D models of the palstave axes made using moulds like this are available to view on Sketchfab here.
This marble sculpture shows an athlete stooping, about to throw a discus. It is one of several Roman copies made from a lost bronze original made in the 5th century BC.
X-ray images have revealed the multiple restorations conducted before the statue came to the Museum. The statue is famed for having a head that does not belong to the original body. The head is very close in age and style, and uses marble that is exceptionally well matched to the torso, but it has been attached at the wrong angle! Complete statues from the time reveal the head to be turned to look towards the discus, rather than the floor.
The images below show some of the other, less visible, restorations.
We hoped you enjoyed this brief introduction to X-ray imaging at the Museum. You can read more about scientific research in our blog celebrating 100 years of science at the Museum here.