AARHUS, DENMARK—According to a statement released by Aarhus University, medieval craftspeople living at the port of Ribe developed their metalworking practices between the eighth and ninth centuries. A team of researchers led by Vana Orfanou examined more than 1,100 crucibles and molds, 24 keys and brooches, and 24 ingots and metal fragments unearthed at two sites in the town of Ribe. Orfanou said that in the eighth century, craftspeople used two or more metals when mixing alloys, but the combinations were not consistent. Leaded brass was commonly used, she added. By the ninth century, high-zinc brass became more common, although leaded alloys were still used for objects such as keys, perhaps because leaded alloys are easier to cast into molds. The ingots did not carry distinctive features, but may have been traded with other Viking settlements. The researchers also detected changes in metalworking tools over time. By the ninth century, a more heat-resistant clay was used for making crucibles. These improvements may have been shared with other Viking settlements, Orfanou explained. To read about a new study of a metal Viking helmet, go to "An Enduring Design."