Sollerön's particular prosperity during the Viking Age was created by the iron production that took place. The geological conditions meant that iron-rich material was collected in lumps in lakes and bogs. The iron lumps were mined, and, after a series of processes, malleable iron was extracted. The bog and lake iron ore were put into roasting furnaces together with fuel to remove water and organic substances from the ore. The ore was then put into blisters, a brick furnace with a stone slab at the bottom, filled with dry fuel and coal. The ore was smelted under high heat using bellows that supplied air. The bellows were trodden or pumped by hand. Later, the bladders were laid by watercourses and the bellows were driven by hydroelectric power.
The ore could then be forged by skilled craftsmen into weapons, tools and household items. Much of the iron was smelted into iron bars, which were then transported to the centre of the country at the time, i.e., Mälardalen with Birka as its capital.
Iron production still leaves its mark on nature today. The blasts left by-products in the form of slag. Almost all around the shores of Sollerön, smaller slag heaps can be seen where the blasts once stood. Centuries of vegetation hide most of the blasts, and it takes knowledge to find them. Mining in Bergslagen eventually outcompeted bog ore in quality and quantity.
At the folk museum Sollerö Hembygdsgård, the association Hembygdsföreningens Vikingagrupp has recreated a blast.
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