Sulphur and iron compounds have now been found in shipwrecks both in the Baltic and off the west coast of Sweden. The group behind the results, presented in the Journal of Archaeological Science, includes scientists from the University of Gothenburg and Stockholm University.
A few years ago scientists reported large quantities of sulphur and iron compounds in the salvaged 17th century warship Vasa, resulting in the development of sulphuric acid and acidic salt precipitates on the surface of the hull and loose wooden objects.
Similar sulphur compounds have now been discovered also in other shipwrecks both from the Baltic and off the west coast of Sweden, including fellow 17th century warships Kronan, Riksnyckeln and Stora Sofia, the 17th century merchant vessel in Gothenburg known as the Göta wreck, and the Viking ships excavated at Skuldelev in Denmark.
"This is a result of natural biological and chemical processes that occur in low-oxygen water and sediments," explains Yvonne Fors from the University of Gothenburg’s Department of Conservation, one of the scientists behind the study in collaboration with Stockholm University.
Even in low-oxygen-water, bacteria can break down organic material including the wood cells in a vessel’s hull. Sulphates that occur naturally in the water are transformed by bacteria into toxic hydrogen sulphide which reacts with the wood. In the presence of iron ions, sulphur and iron compounds form which readily oxidise into sulphuric acid and acid salt precipitates in a damp museum environment once the vessel has been recovered.
This story is reprinted from material from University of Gothenburg, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.