Osmundvraket - A key to the history of iron

The cargo consists of at least 20 barrels but significantly more might exist – perhaps up to 40 or 50. Most of them likely contain osmond iron, fist-sized iron lumps weighing about 300 grams. Osmonds are semi-finished products that can be worked into better iron in order to forge tools, for example.

Osmond iron and bar iron were salvaged from the wreck during a research project on iron production carried out by the museum and Jernkontoret, the Swedish steel producers’ association. Osmond iron was a major export commodity from Sweden during the Middle Ages and well into the early 17th century. After that, forged bar iron became more common, since it brought greater profit and was easier to control.

Finds of larger amounts of osmond iron are rare. Although this wreck find is unique in Sweden, a few similar finds exist around the Baltic Sea. One is a wreck outside Greifswald in Germany, dated to the mid-15th century. Another is located outside Gdansk in Poland, dated to the early 15th century.

Dendrochronological samples from two wooden barrels and from the ship’s more massive structures yielded results in the 1540s. An analysis of timber from the planking and interior trim showed that the wood was felled sometime in Finland around 1553. This likely indicates repairs done to the ship. The ship should therefore have sunk in the 1560s.

A find like this, containing osmond iron in its historical context aboard a loaded ship, is intriguing for archaeologists and others who research iron.