In Sweden, as in the rest of Western Europe, the 12th and 13th centuries constituted an important moment in state formation. International commerce grew rapidly, and Sweden became an integral part of Europe. In this development iron played a crucial role. It was of such significance that kings and other authorities strove to gain and preserve their control over iron production.
In this paper I will look into the role in iron production of towns and their blacksmiths, whereas the role of the merchants in bringing the iron out on to the world market is not considered in this study. There were blacksmiths in all towns. They have primarily been seen as makers of local iron products, which is of course quite right. But there is another field of production that has not been discussed so much: their participation in primary forging (in Swedish primärsmide), that is to say, the last refinery stage of the iron bloom, before it could be used for forging tools and other objects.
All this has been studied in a project called Iron and State Formation in Sweden 1150–1350, published in Swedish in 2010 (Berglund 2010). In this project, I have concentrated on the role of towns both as intermediaries in trade and as participants in the iron-making process (Andersson 2010). This study has since been followed up by an archaeometallurgical study of slag from Visby and Lödöse – two important towns in medieval Sweden – undertaken by the Geoarchaeological Laboratory (GAL) of the Swedish National Heritage Board (Grandin et al. 2012).
Urbanisation was not a medieval innovation since it had been going on, in different forms, since prehistoric times. However, in the 13th century towns developed with special royal economic, social and legal privileges in Sweden. A considerable number of them were situated around Lake Mälaren. Nearly all functioned more or less as intermediaries between the mountain ore districts of Bergslagen, north of Mälaren, and the export merchants in Stockholm. However, chartered towns involved in iron processing were also found in other parts of the country, especially in the south.
Iron has been produced in many parts of Sweden since prehistoric times. It was a commodity that was coveted and necessary for progress in many parts of society. To begin with, bog or lake ore and red earth were used in bloomery furnaces. At least from the middle of the 12th century, and perhaps earlier (Segerström et al. 2010, 204–217), a new technique – the blast furnace, which made the extraction of iron from rocks possible – was introduced in the Bergslagen region north of Lake Mälaren (Figure 17.1). As a consequence, iron production increased tremendously, and the requirements for industrial growth were shaped. Bloomery iron-making lost most of its significance during the late Middle Ages, but it still persisted to some extent until the 19th century.