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 14,264 other followers

Categories

Follow @britishmuseum on Twitter

British Museum on Instagram

#August is named after the Roman emperor Augustus. Before 8 BC the Romans called it Sextilis! 
This head once formed part of a statue of the emperor Augustus (ruled 27 BC – AD 14). In 31 BC he defeated Mark Antony and Cleopatra at the battle of Actium and took possession of Egypt, which became a Roman province. The writer Strabo tells us that statues of Augustus were erected in Egyptian towns near the first cataract of the Nile at Aswan and that an invading Kushite army looted many of them in 25 BC.
Although Roman counter-attackers reclaimed many of the statues, they did not reach Meroë, where this head was buried beneath the steps of a native temple dedicated to Victory. It seems likely that the head, having been cut from its statue, was placed there deliberately so as to be permanently below the feet of its Meroitic captors.
The head of Augustus appears larger than life, with perfect proportions based upon Classical Greek notions of ideal human form. His calm distant gaze, emphasised with inset eyes of glass and stone, give him an air of quiet, assured strength. Coins and statues were the main media for propagating the image of the Roman emperor. This statue, like many others throughout the Empire, was made as a continuous reminder of the all-embracing power of Rome and its emperor. English sculptor Henry Moore was born #onthisday in 1898.
Drawing played a major role in Henry Moore's work throughout his career. He used it to generate and develop ideas for sculpture, and to create independent works in their own right.
During the 1930s the range and variety of his drawing expanded considerably, starting with the 'Transformation Drawings' in which he explored the metamorphosis of natural, organic shapes into human forms. At the end of the decade he began to focus on the relationship between internal and external forms, his first sculpture of this nature being 'Helmet' (Tate Collections) of 1939.
This drawing titled ‘Two Women: Drawing for sculpture combining wood and metal’ was based on a pencil study entitled ‘Ideas for Lead Sculpture’. It reflects his awareness of surrealism and psychoanalytical theory as well his abiding interest in ethnographic material and non-European sculpture; the particular reference in this context is to a malangan figure (malangan is a funeral ritual cycle) from New Ireland province in Papua New Guinea, which had attracted his interest in the British Museum. 
Henry Moore, Two Women: Drawing for sculpture combining wood and metal. England, 1939. Here's another fabulous view of the Great Court captured by @whatinasees at our instagramer event #regram #repost
Check out all of the photos at #emptyBM Vincent van Gogh died #onthisday in 1890. Here's a print of his only known etching. It depicts his doctor, Dr Paul Gachet, seated in the garden of his house.
#vanGogh #etching 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.
Follow

Get every new post delivered to your Inbox.

Join 14,264 other followers

%d bloggers like this: