A mysterious black ornamentation on an Early Bronze Age dagger from Schoolbek (Kosel), Schleswig-Holstein, Germany

Early Bronze Age societies of northern Germany and Scandinavia are well-known for skilfully crafted and richly decorated metal objects. In this paper a Nordic bronze dagger from Schoolbek farm, Schleswig-Holstein, Germany, dating from the mid-2nd millennium BC (Period II) is investigated in detail. Besides chased ornaments the object carries a conspicuous decoration pattern of black coloured stripes and rivets on the hilt that contrasts with the dagger's green patina. Chemical and mineralogical analyses as well as examinations with an optical microscope show that the black areas are largely identical in structure and composition with the green corrosion crusts. Therefore, tinning or comparable decoration techniques can be excluded. It appears instead that the stripes are either the result of local artificial patination treatment or, more likely, of the application of a pasty material such as tar, pitch or resin to the bronze surface. Tiny gold residues indicate that gold foils could possibly have been attached this way. This would have provided deviating corrosion conditions than for the undecorated object parts and thus lead to differently coloured areas.