British Museum blog

A closer look at what the Chiseldon cauldrons are made of

High magnification image of one of the cauldrons

Quanyu Wang, scientist, British Museum

I am a scientist specialising in metalworking technology, particularly in relation to non-precious metals such as iron and copper-alloys. The scientific examination and analysis of the Chiseldon Iron-Age cauldrons is a key aspect of the investigative process as a whole and is crucial in supporting our understanding of them.

For the Chiseldon cauldrons I have been examining the microstructure of the metal under very high magnification in order to see its composition, deduce how it was worked and explore manufacturing techniques. Some of the questions I will be trying to answer include: ‘How were the cauldrons made?’, ‘Were different components from an individual vessel made in the same workshop?’, ‘Were the same parts, such as the iron handles for different vessels, made from the same metal stocks’ and, perhaps the most important question of all; ‘Were the cauldrons made especially for burial or collected together for a particular occasion?’

Taking a sample from one of the cauldrons

Taking a sample from one of the cauldrons

Finding appropriate samples to test can be extremely difficult as the metal, particularly the iron, is extremely corroded and very fragile. The sampling process is made additionally complicated by attempting to sample a potential area that is as discrete as possible to make sure that we do not endanger the structural integrity of the artefact but will yield the best results. This is not a decision that is taken lightly and sample positions are chosen in consultation with curators and conservators. In order to reveal the structure of the metal the samples are mounted in resin, their cross-section polished, and then examined using metallographic microscopy up to x1000 magnification and a scanning electron microscope equipped with energy dispersive X-ray spectrometry (SEM-EDX) that allows us to examine them up to 300,000 times its actual size.

We have been able to deduce that the iron handles from both the cauldrons studied so far were probably formed by repeatedly hammering an iron bar while it was rotated. Additionally, iron used for the same parts of different cauldrons showed differences in microstructure and slag (impurity) inclusions, and was therefore from different stocks of metal, suggesting that these cauldrons were probably collected together rather than being made at the same time specifically for burial.

A high magnification scanning electron microscope (SEM) image of a copper alloy sample from one of the cauldrons. Darker horizontal lines were caused by many cycles of working and heating

A high magnification scanning electron microscope (SEM) image of a copper alloy sample from one of the cauldrons. Darker horizontal lines were caused by many cycles of working and heating

The copper-alloy is likely to have been subjected to many cycles of working and annealing (heating) to reduce the sheet metal to its final thickness (and shape). Significantly, there are differences in the content of sulphide within the copper alloy from one of the cauldrons, which suggest that the metal of the bowl and that of the band were probably refined to different levels or were from different sources.

Some of the results we have achieved so far are intriguing and much more revealing than expected given the condition of the material. Further analysis of the remaining cauldrons will not only provide further details of how the metal was processed and how the cauldrons were made but will help us build up a more complete picture of the deposit as a whole.

The Chiseldon cauldrons research project is supported by the Leverhulme Trust

Find out more about this research project

If you would like to leave a comment click on the title

Filed under: Archaeology, Chiseldon cauldrons, Conservation, Research

One Response - Comments are closed.

  1. John Winterburn says:

    Some great images , thanks for posting these.

    Like

Enter your email address to follow this blog and receive notifications of new posts by email.

Join 14,258 other followers

Categories

Follow @britishmuseum on Twitter

British Museum on Instagram

Beatrix Potter was born #onthisday in 1866. Here are some of her flopsy bunnies! 🐰
#BeatrixPotter Made in AD 700, the exquisite Hunterston brooch was found at Hunterston, Ayrshire during the 1830s. It is a highly accomplished casting of silver, richly mounted with gold, silver and amber decoration. It is sumptuously decorated with animals executed in gold wire and granules, called filigree. In the centre of the brooch is a cross flanking a golden ‘Glory’ representing the risen Christ #MedievalMonday
The Hunterston brooch will feature in our forthcoming #Celts exhibition, on loan from @nationalmuseumsscotland. Encounter an African contribution to the global carnival tradition through contemporary artist @zakove’s Moko Jumbie sculptures in the Great Court. These spectacular 7-metre-high male and female figures in striking black and gold costumes are inspired by aspects of African masquerade. #ZakOve
Find out more about our #Africa season this summer with events and displays at www.britishmuseum.org/whats_on/celebrating_africa.aspx The spectacular Sutton Hoo treasure was discovered #onthisday‬ in 1939!
This is a purse lid from the Sutton Hoo ship burial. Wealth, and its public display, was probably used to establish status in early Anglo-Saxon society much as it is today. This purse lid from Sutton Hoo is the richest of its kind yet found.
The lid was made to cover a leather pouch containing gold coins. It hung by three hinged straps from the waist belt, and was fastened by a gold buckle. The lid had totally decayed but was probably made of whalebone – a precious material in early Anglo-Saxon England. Seven gold, garnet cloisonné and millefiori glass plaques were set into it. These are made with a combination of very large garnets and small ones, deliberately used to pick out details of the imagery.
Purse lid. Anglo-Saxon, early 7th century AD. From Mound 1, Sutton Hoo, Suffolk, England.
#SuttonHoo #AngloSaxon The spectacular Sutton Hoo treasure was discovered #onthisday‬ in 1939!
Mrs Edith Pretty, a landowner at Sutton Hoo, Suffolk, asked archaeologist Basil Brown to investigate the largest of many Anglo-Saxon burial mounds on her property. Inside, he made one of the most spectacular archaeological discoveries of all time. Beneath the mound was the imprint of a 27-metre-long ship. At its centre was a ruined burial chamber packed with treasures: Byzantine silverware, sumptuous gold jewellery, a lavish feasting set, and most famously, an ornate iron helmet. The ship buried at Sutton Hoo is the largest Anglo-Saxon ship yet unearthed.
You can see the treasure from Sutton Hoo on display in Room 41.
#SuttonHoo #AngloSaxon The Arch of Constantine in #Rome was completed #onthisday in 315, drawn here by Canaletto.
Follow

Get every new post delivered to your Inbox.

Join 14,258 other followers

%d bloggers like this: