The history of iron in Sweden stretches back to the Bronze Age, with bloomery iron making which mainly took advantage of bog ore deposits.
During the Middle Ages, the need for iron and iron production intensified, with the appearance of mines and blast-furnace technology. The osmond iron of blast furnaces was cheaper than bloomery iron products.
This malleable iron was broken up into smaller pieces called osmonds, hence the origin of the name for this type of iron. These osmonds were a type of bar often in the shape of a spade with a particular weight of about 230 grams. Starting from the 16th century, osmond iron was made from pig iron.
King Gustav Vasa forbade osmond iron, so it was replaced with bar iron. During the 17th century bar iron became increasingly used in iron production, and exports began to increase significantly. The oldest traces of bar iron forging are from 1528.
Transporting and exporting iron
The transport of iron relied on water fairways. Shipping was limited during the winter, as were exports of iron. Gaining control of the iron trade became crucial, and it was probably the major economic resource for medieval Sweden. Stockholm’s importance increased thanks to its strategic location between Lake Mälaren and the Baltic Sea, providing the opportunity to control both exports and trade in iron.
Exports of osmond iron was amounted between 3,000 and 4,000 tonnes each year in the second half of the 16th century. Bar iron became incredibly important, growing from a few hundred tonnes in the mid-1500s to more than 1,000 tonnes later in the 16th century up until the early 17th century. Swedish iron exports consisted mainly of osmond iron until it was banned, after which bar iron began to dominate.
Swedish osmond iron was exported to several different parts of Europe during the late Middle Ages. The biggest importers were the North German ports, with Lübeck–Hamburg being the biggest at the end of the 14th century. Exports to English ports were less extensive but still significant. The Netherlands came to play an increasingly major role as an importer at the end of the 15th century. By the late 16th century, Danzig was the largest importer of Swedish osmond iron. There, it was further processed into bar iron and exported to Western Europe. When bar iron replaced osmond iron in Sweden during the 17th century, exports were mainly directed to the west.