Sedgeford Archaeology: Metallurgy and more videos!

In the summer of 2014 I had the pleasure to assist Dr Eleanor Blakelock in running week-long seminars in archaeometallurgy and experimental archaeology at the Sedgeford Historical and Archaeological Project (SHARP) in Norfolk. The current excavations are focused on two areas of an Anglo Saxon village, however their “primary objective is the investigation of the entire range of human settlement and land use in the Norfolk parish of Sedgeford”. The excavations have been going on since 1996, and the organisation provides comprehensive teaching in a wide area of archaeological subjects. You can read all about the project here.

The previous year SHARP began a new course in archaeometallurgy. Ellie wanted to expand the course, so I lent a hand with some of the hands-on and experimental work. We built furnaces, made moulds, crucibles, mixed alloys, and cast bronze. We even got some local ore to smelt iron. It was an intensive week and the hottest one I have ever experienced in England.

During the event, Ellie took some videos of us in action. The first one shows us building a pit furnace for casting bronze and a pit for heating the moulds. The video then follows us through the casting process.

One interesting phenomenon of the week was how we became separated from the rest of the SHARP community. We were given our own space that wouldn’t interfere with the the trenches or the campground, and was not archaeologically sensitive. The first two days when we were building furnaces we kept to the same schedule as everyone else. However, once the casting began we couldn’t stop for meals or keep to the schedule that everyone else had. One of our group would go down to the mess tent and bring back food for the rest of us. We were effectively isolated, although the others always knew where we were from the rising smoke. Later when we started showing up with freshly cast bronze jewellery there was a bit of envy and wonder. In the space of a couple days we had gone from being part of the community to the people who were “over there” with special knowledge, and who didn’t conform to the regular schedule or tasks that everyone else did. We kept odd hours, were continually covered in soot, but had become somewhat wizard-like in our knowledge of metalworking (not to mention regularly getting out of kitchen chores!).

On the final evening, everyone joined us for the iron smelt. The week had been intensely hot so we started stoking the bloomery furnace in the late afternoon, after the heat of the day. As the sun set and most folks had finished their supper, they came by to see the furnace in full swing with fire shooting from the top. Of course everyone wanted to take a turn at the bellows. It was a magical evening. Stories were told, and mysteries presented. The people who worked on the furnace and participated in the smelt had a new appreciation for the process of making iron. The archaeologists also had a more rounded knowledge of what a smelting site could have looked like, including the resources needed for smelting iron, and the physical space that people would have inhabited while at work. It was past 1 AM when we finally called it quits for the night and let the furnace cool.

In a way the course was an initiatory experience for the archaeologists who participated in the event. It was hard work, but they learned the secret knowledge of the smiths and have stories and their bronze castings to prove it. They also gained a well-rounded introduction to archaeometallurgy that included both theory and practice.

I have been back to help run the course and plan to be there again this summer. The course will run again this July. If you’re interested in learning more about the course or being part of the excavation please sign up on the SHARP website.

EXARC: 9th Experimental Archaeology Conference, Dublin (IE)

17-18 January 2015

I missed the first day of the conference. Instead I was at my PhD graduation ceremony. It was a wild trip. I graduated with the full regalia of cap and gown, had a quick couple glasses of wine at the archaeology department’s reception, and then we hopped on a fast flight to Dublin for the EAC9 conference at University College, Dublin. The conference was a collaborative effort brought together by EXARC, UCD, and the Irish National Heritage Park. It was a large conference with over 200 delegates, 20 papers, and 31 posters.

The Dublin University campus is huge and spread out, so we had a time trying to find the right building. I arrived just in time to deliver my paper and see the rest of the session. There were some interesting papers and posters given that explored the range of pyrotechnology in archaeology from cremation to glassworking and metalwork. In addition to the usual poster session, individual posters were given a ten minute presentation while being projected in the main hall. These included Jiří Hošek, Ryszard Kaźmierczak, Paweł Kucypera & Maciej Tomaszczyk (Nicolaus Copernicus University) with a presentation on steel carburising in a small shaft furnace, and Yuri Godino & Lorenzo Teppati Losè (University of Florence) presented a poster on their experiments on cupellating galena to produce refined silver.

I was also interested in the presentations on glassworking. There were two very different approaches to the subject with Marta Krzyżanowska & Mateusz Frankiewicz from Poland who spoke about producing Early Medieval lampwork type beads in an open hearth based on excavations in Ribe. Jonathan Thornton from Buffalo, New York spoke about replicating trade bead production based on evidence from Africa using glass frit in a clay mould .

The presentations that discussed metal began with my presentation on inverse segregation and its influence on chemical analysis of objects cast in the Bronze Age. Padraig McGoran of Umha Aois presented a poster on his experiments that included problems and solutions in casting into open one piece moulds.

After that I was off to the university’s experimental grounds to help set up furnaces and get ready for casting. The centre boasts a Mesolithic house, along with metalworking furnaces in varying states of decay. There are separate areas set aside for flint knapping, firing pottery, and active metalworking projects. The members of Umha Aois had already started building a variety of furnaces that included ones heated from below, from the side, and another with a tuyere that had a 90 degree bend that blew the air directly onto charcoal covering a flat, pan-shaped crucible. I worked at a portable ceramic furnace that was brought to the site by Fiona Coffey. It was set up inside Billy Mag Floinn’s newly constructed traveller’s tent. Despite it being wind and waterproof, the flaps ventilated it well and we kept warmer than the others who were set up under a tarp outside.

A memorable birthday! Photo by Tríona Sørensen

At lunch I was presented with a birthday cake. Surprisingly no one had anything bigger to cut it with than a pocket knife. The only solution was to get one of Billy’s bronze swords and carefully slice it. It was a most memorable birthday.

Bronze objects that had been created by the members of Umha Aois were on display, including swords, horns, tools, spears, and stone moulds. We spent the day casting axes, jewellery, tools, and more. There was a constant flood of visitors and regular announcements were made when one of us was ready to pour. For most of the day it was standing room only. The casting events continued all afternoon and into the evening.

Rather than head straight back to Sheffield the next day, I had arranged to see the Bishopsland Hoard and a hammer from the Garden Hill Hoard at the National Museum. I’d hoped that I could see some moulds, and to have some colleagues also examine the objects. Unfortunately emails were crossed and I just got to see the hoard and hammer. However, that was fascinating in itself, and I spent hours measuring, weighing, drawing, and photographing every detail of the artefacts.

Events like this are exhilarating and exhausting. We all learn more every time we meet, and we come away with new ideas as well as newly cast objects to finish up. This week I’ve been filing and polishing some of the bronze fibulae I cast and I still need to get to work on the replica I cast of the hammer from the Lusmagh Hoard. Meanwhile, there are more waxes and moulds to make to get ready for casting again.

Click on the link for more information about the conference EXARC: 9th Experimental Archaeology Conference, Dublin (IE)

and here is a moment by moment twitter feed from the conference

Traces of Empire – Video!

Some months ago Weston Park Museum here in Sheffield approached me about making a film about how metalwork would have been done in Roman Britain. Most of what I do is related to the Bronze Age, but I jumped at the chance to do something new. We set up a time to go take a look at the brooches they would have on display. After photographing them and taking measurements, I made some waxes and then made some moulds. The process is pretty well explained in the video.

I also realised that bag bellows would probably not be the way to go, so I built the bellows that are described in the tutorial on this website.

Alan Sylvester, the filmmaker for Museums Sheffield and Lucy Creighton, (now the acting curator of archaeology) both spent long hours at Heeley City Farm helping me build the furnace and pump the bellows. After a day of filming Alan felt he needed more shots of metal being poured, and so we went back for a second day of filming. This time I had some of the pieces I cast earlier, so we could show a bit of the clean-up.

It was a great experience. Later I gave a talk at Weston Park Museum about making the film and the importance of experimental archaeology. I also brought along the bellows and some of my tools. If you go see the exhibit, there’s a shorter version of the film on a loop near the display.

Casting at Heeley City Farm, Sheffield

What is Experimental Archaeology? It Begins With a Question

My first foray into experimental archaeology came when I was working at the Science Museum of Minnesota, where I was cataloguing the metals collections there. It’s not well-known, but during the Late Archaic Period in the Lake Superior region of North America (Minnesota, Northern Ontario, and Upper Michigan) Native Americans worked with the copper that was easily found there. The culture was aceramic, meaning that they did not make pottery, and so did not have the means to cast or alloy the copper they found. However, they could hammer it, anneal it, and create ornaments such as earrings, finely detailed cut work, along with spears, knives, and arrowheads. It was while I was examining the spears that I started to wonder how they were made. The spears were triangular in cross section and I noticed that they were perfectly smooth on two sides, but on the third side the metal was folded with an almost flowing appearance. This was accentuated by fine corrosion on the surface. Knowing these weren’t cast, the first question I had was how they could have been hammered into a raised shape. The clues were in the surfaces and I reasoned that rather than being poured into a mould, they were hammered in, and the rougher surface was where the metal was packed in and hammered from the top. I carved a block of walnut to create a triangular spearhead and then lit a charcoal fire to anneal the copper. I had a friend standing by with bellows, but they weren’t needed. The charcoal fire aided by a light breeze was hot enough to anneal the copper. The metal was easily hammered into the mould using a hand-held hammerstone. The metal pushed into the mould smoothly along the sides and the top surface was rough from my pushing the edges of the metal from the top edges of the mould and folding them back onto the surface of the spear.

I was not only fascinated by the process of making a spear, but also how I had deduced it from examining the original spears in the museum and puzzling out the details. The whole thing was eventually written up and published in The Minnesota Archaeologist. After the first foray into experimental archaeology, I was hooked. From that time forward, I closely examined tools and metal objects, trying to figure out how they were made, what processes were used, and what tools were needed, how those tools were made, and receding back infinitum.

This is the crux of experimental archaeology that sets it apart from re-enactment or generally doing craftwork: experimental archaeology starts with a question. Experiments can be done in a lab in order to control as many variables as possible. Experiments can also be done in the field, but unlike re-enactment, not every tool and object needs to be a replica of an original. This is especially true when doing experiments in prehistoric crafts, where few of the original tools still exist. When doing experiments, I can use steel tongs and graphite crucibles, as long as they will not affect the parameters of the question. Likewise in some experiments, for instance trying to learn the melting times for different alloys in a charcoal fire, rather than using bellows I will use an electric pump to make sure that each sample was created under the same conditions. Each experiment must be thought out ahead of time and choices made for each step. The important thing is not to be distracted by the possibilities, but to always focus on the question and to create the conditions that will give a meaningful answer, even if it is inconclusive and leads to other experiments. It’s also important to measure, weigh, time, and quantify as much as possible. For example when experimenting with smelting, the ore should be weighed before and after processing. How long it took for the ore to smelt should be timed. The amount of charcoal used should be recorded. The size of bellows and furnace should be noted. Finally the slag, dross, and refined metal should be weighed and recorded in order to find out how much metal was produced from the ore. The slag could be examined to see if there is any metal left, and note if it could be re-smelted. It can be tedious work at times, and a pain to remember to weigh, record, and photograph everything, but the results will be worth the effort, because the information hasn’t been lost. The data from the experiment you did will lead to more experiments, but will also yield useful information for others.