Norwegian iron helped build Iron-Age Europe
Steinar Brandslet / Gemini, NTNU Trondheim - Norwegian University of Science and Technology
Furnaces, often four in a row, with the equally large slag piles indicating that all the furnaces were run as a unit simultaneously. Each furnace ran on a cyclical program, until the slag pit was full. (Illustration: Inkalill)
Arne Espelund isn’t sure exactly when his interest in iron began, but the first time he tried making iron was as a student teacher with an eighth grade in 1977.
It didn’t work.
Making iron is not that easy, and something had gone awry for the eighth graders out in a bog near Trondheim. But they had a great experience and asked lots of questions.
It took a few years, but Espelund finally succeeded with another class at Skogn middle school in Levanger municipality.
“The students were thrilled,” says Espelund, who has long tried to bring this part of Norway’s history to life.
Espelund and his students adopted the iron-making method that Ole Evenstad had described in 1782. But this was by no means the first method devised.
Two older methods using the bloomery technique have been used, but producing good iron by this “direct” method is an advanced process that requires the right temperature and oxygen supply, sometimes involving multiple steps.
An iron bloom weighing 17 kilograms, typical for iron production in inner Trøndelag around the year 200 CE. (Photo: Arne Espelund)
Iron production started about 3500 years ago in Asia Minor. In Norway, people have been producing iron for at least 2300 years.
Espelund is now an NTNU professor emeritus and a mining engineer, but he works in multiple disciplines. Studying iron production through the ages has been one of his main interests, although he is not a trained archaeologist.
Espelund finds that an interdisciplinary approach is essential to gain a holistic understanding of a subject. He does not hesitate to speak out when he disagrees with some of the archaeological work being carried out at a number of institutions, and is not shy about sharing his own assertions about other researchers’ results.
“Archaeology is descriptive,” says Espelund, and he thinks that many archaeologists are content to describe how something looks, but without going into depth on how it worked, and without putting the results into a natural scientific context.
But, he says, the context is important and can be figured out. For example, charcoal remnants used in the production process can be analysed using the C14 method to determine their age.
As a mining engineer, he readily uses chemical analysis to explain how our ancestors produced malleable and cast iron.
Finding slag heaps
Ore for iron production was gathered in marshes in the springtime, and smelting took place in autumn. After the iron was reduced, slag remained. Around 400 places in Trøndelag alone show traces of early iron production.
Places that testify to iron production in Trøndelag: Heglesvollen, Øst-Fjergen, Stordalen, Østrungen, Tovmoen, Storbekkøya, Vårhussetra, Tverråbakken are all sites from the Early Iron Age that have undergone archaeometallurgical study.
The conditions for iron production were ideal in Trøndelag and in Jämtland province in Sweden, with widespread access to both pine trees and ore.
“Today it’s the slag heaps we find first,” says Espelund. Slag didn’t have much value then, and it doesn’t now either, except as fill for road surfaces and as a tourist attraction.
Espelund has studied small pieces of iron slag from large slag heaps in Norway, Sweden, Iceland, Austria and Catalonia, and he has found similarities.
The slag heaps found all around Norway testify to significant production. A farm would use one to two kilos of iron per year until the Middle Ages — not much compared to the 450 kilos of iron we use annually now, but still impressive. Norway is ideal for examining this production.
“No other country has so many well-preserved furnaces from several periods,” Espelund says.
The reason is that Norway is a sparsely populated country, and many of the production sites were situated by marshes far from most people. In Denmark, on the other hand, most sites have been ploughed up and traces of iron production have disappeared.
Large scale production
In 1982, Espelund was part of the research team that discovered the 2000-year-old iron production facility at Heglesvollen in Levanger in Nord-Trøndelag. Here they found four ovens and dug out one of them.
The slag pit of oven C2a at Heglesvollen, Levanger municipality, after emptying. (Photo: Arne Espelund)
The researchers found a total of 96 tonnes of slag, which was spread equally between the four furnaces. This suggests that the furnaces operated simultaneously, but in different stages of the production process.
It is quite common to find four ovens beside each other. For some reason, not yet understood, there is always water in front of the ovens.
“We estimate that teams of about 10 people worked together,” says Espelund. “We are talking about a well-planned production process and an industrial enterprise with periodic, batch operation of all the furnaces.”
Nothing indicates that any religious or other rituals were part of the process, or links it to women or children.
The evidence points to a rational, industrial production of iron, with the focus being on obtaining the best possible metal for tools and weapons through hard work.