Archaeometallurgy

Making Sense of Analytical Data

After the inital excitement of the arrival of new material in the lab, curiosity had to be curbed and the main task of the day tackled. This task was to process and interpret anayltical data acquired last week during many days work on the SEM. I use many different analytical techniques to investigate the more important archaeometallurgical residues passing through the lab – and the analytical SEM is one of the most useful.

BSEM Roman smelting slag

Backscattered electron image of a tapped Roman iron smelting slag. The field of view is 2.5mm.

 

The backscattered electron images reveal compositional contrasts through their grey scale. In this image the dominant phase, appearing pale grey, is fayalite (an olivine mineral, approximately Fe2SiO4).

Across the centre of the image is a discontinuity, produced by the chilling of the surface of an individual lobe of slag as it flowed from the surface and cooled in the air.

The crystals are large, suggesting the slag cooled slowly, and the lobe margin is not marked by the development of much iron oxide, so this example probably cooled right in the mouth of the furnace.

As well as producing these images, the analytical SEM also permits chemical microanalyses from tiny spots or areas of the sample.

The second backscattered electron image shows a tiny detail of the first image, with the location of microanalyses.

Detail of Roman iron smelting slag

Detail of Roman tapped iron-smelting slag. Field of view is approximately 0.17mm.

 

The instrument provides the chemical analyses, but they then have to be recast as mineral formulae – and that was today’s task. With many hundreds to do that was a substantial task in front of the spreadsheet. Gradually a picture emerges of the overall composition of the slag and of its constituent minerals.In this instance, the slag proved to be typical of residues produced during the smelting of iron ores from the Forest of Dean. That is a useful result in itself, allowing one aspect of the economy of this Roman settlement to be understood. As other samples from the same site are interpreted further details will emerge – permitting reconstruction of the yield and efficiency of the furnace as well as aspects of the technology itself.

Spreadsheet of chemical data

Processing microanalytical data, to convert the microanalyses into mineral formulae.

 

Archaeometallurgical residues provide a very direct link back to a particular occasion in the past, when an artisan did a particular job in a particular way. The waste material provides key evidence for that moment in time. Although studying the waste, rather than the product, might seem perverse, there is often a richer set of evidence about hte nature of the process to be gleaned from the residues than from the artefact. Crucially, the residues also typically remain close to the site of the activity, whereas the products were dispersed after production and may not be able to be linked back to their point of origin.

Careful investigation of such archaeometallurgical residues may allow us to come as close as we ever could do to looking over the shoulder of the Roman smith at his work.

What is in the Post?

One of the delights of specialist post-ex work is that you never know quite what the next delivery from the postman or courier will bring. Today’s delivery was of 15 crates of iron-working residue (almost quarter of a tonne!) from a medieval site in Ireland.

A quick look (its a bit like Christmas…!) shows a beautifully-preserved assemblage of slag and large fragments of tuyères (the ceramic ‘nozzle’ carrying the blast from the bellows into the blacksmith’s hearth).

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Archaeometallurgy in the university – a PhD student’s day

Introduction

My name is Ruth Fillery-Travis, and I am an archaeometallurgist. That is, I use scientific analytical techniques to examine metal objects and the evidence of their production. I’m in a sub-discipline of a sub-discipline, as archaeometallurgy is a part of archaeometry/archaeological science, which is often considered a sub-discipline of archaeology. Luckily enough all the sub-sub-sub stops there, because I’m in the UK – if I were in the US archaeology itself might be considered a sub discipline of anthropology!

It might seem strange to be in such a niche subject area, but it fits my interests perfectly – I wanted to be a physicist right until I started studying it at university! After that I switched to Classical Archaeology, which had zero science and a lot of critical analysis of art, architecture and archaeological objects. Archaeometallurgy allows me to combine those two areas – I get to look at sometimes quite stunningly beautiful classical objects and not just analyse their physical appearance but use scientific techniques to analyse what they were made of and how they were made – like the snake ring adjacent.

Snake head of gold Roman finger ring

I’m currently reading for a PhD at the Institute of Archaeology, University College London. I started in 2009 – before that I worked in local council archaeology as a records assistant on the ‘Sites and Monuments’ or (in more modern terms) ‘Heritage Environment Records’ of Norfolk and then Greater London. Nothing to do with archaeometallurgy – but then that’s a common problem with studying archaeology. If you can get a job in the discipline at all – which is tough – then it often isn’t in the area you originally trained in. But the advantage of that is that you can gain some fantastic experience – certainly my time working on the Greater London records was fascinating.

Between those jobs (more…)

Historical metallurgy

Like many archaeologists, outside of my ‘proper’ archaeological job, I seem to find time to get involved with lots of other archaeological activities as a volunteer. One of my many ‘other’ roles is to be the Chairman of the Historical Metallurgy Society. This is occupying quite a bit of my time, so I thought it was worth saying something about it. I guess in many ways it is quite typical of a lot of national and local specialist societies and groups – entirely run by volunteers who are often the world’s leading experts in their particular fields, and producing information at various levels from high-level peer-reviewed academic journals and monographs to informal datasheets for archaeological fieldworkers.

The manufacture and working of metals is one of the most important human activities. Archaeologists encounter metal artefacts and evidence of metalworking in all periods from the Bronze Age through to the post-medieval. However it is often difficult to identify and make sense of. This is why the Historical Metallurgy Society was established almost 50 years ago. The Historical Metallurgy Society is a dynamic and exciting international forum for exchange of information and research in historical metallurgy. This means all aspects of the history and archaeology of metals and associated materials from prehistory to the present day.

Members’ interests range from processes and production through technology and economics to archaeology and conservation. The Society holds several conferences and meetings each year which showcase the latest research, and explore a wide range of metallugical landscapes and locations. The next meeting is in Cardiff in September.

The Society’s datasheets were launched over 15 years ago, and remain a popular resource for archaeological fieldworkers and managers alike. They can be dowloaded free. The archaeology committee is currently updating and enlarging the scope of the datasheets. The datasheets – and indeed Historical Metallurgy Society members – helped to inform the development of the English Heritage guidelines for Archaeometallurgy, and Science in Historic Industries.

A mini-datasheet on ironworking residues has also been produced – aimed specifically at archaeological fieldworkers.

The Society’s archaeology committee has also recently produced a UK-wide research framework for archaeometallurgy called ‘Metals and Metalworking’. This sets out current knowledge and areas where we need to learn more; it can be downloaded from the Historical Metallurgy Society archaeology committee page.

Joining the Society only costs £20! Details can be found here. Members receive a scholarly journal (Historical Metallurgy) twice a year and a newsletter three or four times a year. The Historical Metallurgy Society has an extensive archive of books and reference material, and can put you in touch with expertise all over the world… the Society also provides small grants for research and travel. Please visit the website – or look at our Facebook page!

 

Chain Bridge Forge – Overview

Chain Bridge Forge: Preserving a 19th Century Blacksmith

It is situated on the east bank of the River Welland about one mile from the town centre, only four metres away from the river itself. The building dates back to the early 1800’s and in 1826 it appeared in White’s Directory and it shows that the Blacksmith was a Francis South. It then appears to have been sold to Edward Fisher who was general town Blacksmith and from his 1850–60 day books it showed his trade also included the servicing the boats that used the port of Spalding. In 1898 the Dodd Family took ownership of the Forge and were recorded as Spalding’s last Harbour Master. Three generations of the Dodd family worked the forge. George Robert Dodd originally from Heckington in Lincolnshire had learnt his trade at Newmarket and presumably it had paid well enough for him to get married and purchase the forge for £280. The Forge had to adapt with the times and in the 1950’s Geoffrey Dodd business almost ended but he turned his hand to making carnival floats for the Spalding Flower parade and this continued for another 30years. In 1989 the building was sold to the local Council and work was done to preserve it structure but sadly was not developed as a museum.

Today we hope to fulfil this vision and The Friends of Chain Bridge Forge has been formed to conserve the artefacts, tell the story of this historic building and build an educational programme which will involve schools and the community. The building is approximately 12.3m long and 6.3m wide. It is subdivided internally into three spaces, the largest of which contains the forge and main work space. The floor is mainly of hard packed earth, with large pieces of stone and slate covering some areas. The building has remained largely unaltered and retains its original contents and is a treasure trove of artefacts and documents which illustrates this wonderful building past and the Blacksmiths that have worked it.

The Forge has recently been awarded £50,000 of Heritage Lottery Funding and therefore the project has commenced. If you would like to follow our progress or would like to contribute then please view our website http://www.chainbridgeforge.co.uk