Ajaloo ja arheoloogia instituut

In this work we used non-destructive SEM imaging and EDS analysis to characterize the material composition of an Arabic finger ring, which was found in a 9th c. woman's grave at the Viking Age (A.D. 793-1066) trading center of Birka, Sweden. The ring is set with a violet stone inscribed with Arabic Kufic writing, here interpreted as reading "il-la-lah", i.e. "For/to Allah". The stone was previously thought to be an amethyst, but the current results show it to be coloured glass. The ring has been cast in a high-grade silver alloy (94.5/5.5 Ag/Cu) and retains the post-casting marks from the filing done to remove flash and mold lines. Thus, the ring has rarely been worn, and likely passed from the silversmith to the woman buried at Birka with few owners in between. The ring may therefore constitute material evidence for direct interactions between Viking Age Scandinavia and the Islamic world. Being the only ring with an Arabic inscription found at a Scandinavian archaeological site, it is a unique object among Swedish Viking Age material. The technical analysis presented here provides a better understanding of the properties and background of this intriguing piece of jewelry.

TRADITION, INNOVATION AND NETWORKS - METAL WORKING AROUND THE BALTIC SEA FROM THE BRONZE AGE TO THE MIDDLE AGES

From the rock carvings depicting ships in the Scandinavian Bronze Age to the age of the Hanseatic League and its mighty cargo ships, the Baltic Sea has always played an important role as a travel zone, facilitating interregional contacts and dissemination of cultural and technological knowledge. The study of metallurgical practices is indicative of the spread of innovation and the movement of craftsmen, and therefore not only shows the movement of goods but also the transfer of new ideas and the dissemination of people. Prehistoric and medieval production of metals in the Baltic Sea region demonstrates both shared practices and discrete traditions, making it central for our understanding of cultural relations and networks within this area.

This session aims to bring together archaeologists and archaeometallurgists exploring the traditions, continuity, and developments of metal crafts through external influences and innovation from the Bronze Age to the medieval period around the Baltic Sea. The focus will be on the history of technology and traditions of metal production, including aspects of metal working techniques, utilization of tools, and the layout and “chaine operatoire” of workshops. The interdisciplinary nature of the session will encourage discussions between cultural-historical approaches, experimental and archaeometric studies, to enrich our understanding of technological practices and to explore how metals, technologies and traditions were spread and shared within the region.

This paper investigates Estonian tools for non-ferrous metal casting in the form of crucibles, moulds, and casting ladles dating to the Estonian Iron Age (500 BCE–1227 CE), adding elemental analysis and 3D modelling to the traditional typological comparison. In contrast to the neighbouring countries of Russia, Latvia, and Sweden, no comprehensive study has previously been published on this subject for Estonian material. The typological analysis sets Iron Age Estonia in the same metalworking tradition as that of other eastern Baltic countries and Northwestern Russia. However, some classes of casting tools present in Scandinavian and Slavonic areas have so far not been encountered in the Estonian archaeological record. The elemental analysis included qualitative pXRF analysis of 175 artefacts and detailed residue analysis using SEM-EDS of thirteen selected artefacts. This analysis identified for the first time Estonian Iron Age casting tools – crucibles – used for casting gold and silver. Most of the investigated crucibles were used for casting various copper alloys, while the casting ladles and most of the stone moulds were used for casting pewter. Casting of pewter and precious metals only occurred in regional centres such as hill forts and strongholds, while copper alloys were cast in all parts of Estonia. In addition to clarifying fundamental questions about Estonian Iron Age metal casting, this study also lays a foundation for using modern analytical techniques in future investigations of Estonian metalworking traditions.

29 iron rings with diameters between 9 and 15 cm were excavated in 1989 at a Vendel Period settlement site with a longhouse, located at Åselby in Dalecarlia, Sweden. Most of the rings had between one and three smaller rings attached. Rings of this type and size are fairly common at Scandinavian Vendel and Viking Period sites – settlements, cemeteries and cult precincts – but their function remains debated. The rings from Åselby have been interpreted as iron/steel bars, to be used or traded as raw material for e.g. weapons production. Previous metallurgical analysis of one Åselby ring showed it to consist of somewhat uneven but still decent-quality carbon steel. General conclusions should however not be drawn from a single observation.Here, we have sampled six Åselby rings for metallographic examination of the cross-sections. The material quality and carbon content of the sampled rings were found to be very uneven, and relatively large inclusions of unworked slag were common. We conclude that the rings were not bars of raw material. Instead, they may have been amulet rings, intended for ritual use. If so, our results suggest that the material properties of amulet rings may have been less important during rituals –it may have sufficed that the rings had the right shape.

Determining maximum heating temperatures of burnt bones is a long-standing problem in forensic science and archaeology. In this pilot study, controlled experiments were used to heat 14 fleshed and defleshed pig vertebrae (wet bones) and archaeological human vertebrae (dry bones) to temperatures of 400, 600, 800, and 1000°C. Specular component included (SCI) color values were recorded from the bone surfaces with a Konica-Minolta cm-2600d spectrophotometer. These color values were regressed onto heating temperature, using both a traditional linear model and the k-nearest neighbor (k-NN) machine-learning algorithm. Mean absolute errors (MAE) were computed for 1000 rounds of temperature prediction. With the k-NN approach, the median MAE prediction errors were 41.6°C for the entire sample, and 20.9°C for the subsample of wet bones. These results indicate that spectrophotometric color measurements combined with machine learning methods can be a viable tool for estimating bone heating temperature.

The smithy site of Käku, dated to the 14th-17th century CE, contains four different smithies built on top of each other. Finds from the site contain evidence from iron forging, casting and forging of copper alloys, and bone working. Metallographic analysis of iron blooms and bars from the smithy site has proved to be a valuable source of information for understanding the variety of activities performed at the site. The iron processing ranged from primary forging of iron blooms into bars, the manufacture of artefacts like knives, and the recycling of old cutting tools into bars which could be reused to produce new items. As smithies are quite rare sites to be excavated, the information obtained from Käku helps to shed light on the activities performed in the rural smithies and determine the rural smiths' role in the iron processing chain in the Late Medieval and Early Modern period.