Insights into the Galloway Hoard

Session

Analysis and Imaging in Heritage Science

Authors

Dr Mary Davis (1), Dr Martin Goldberg (1)

Affiliations

1. National Museums Scotland

Keywords

archaeology, SEM, X-radiography, CT scan

Abstract text

Summary

This paper presents an overview of some work carried out on an early medieval Hoard of exceptional quality and significance. Although predominantly under the aegis of the National Museums Scotland (NMS), a range of available techniques within several partners and affiliated organisations have revealed much ’hidden’ information about the artefacts. Techniques employed have included: X-radiography, CT and micro-CT scanning, microphotography and scanning electron microscopy (SEM).

Introduction

The Galloway hoard was discovered by metal-detectorists in 2014 in Dumfries and Galloway in southwest Scotland. It was buried around 900 CE and contained a variety of items from diverse cultural backgrounds: these included Viking, Hiberno-Norse and Anglo-Saxon artefacts plus some material originating from continental Europe and Asia. The hoard also contained preserved textiles, much of which appeared to be wrapping both individual artefacts and groups of objects. The material was buried in two layers; an initial ‘decoy’ layer consisted of silver bullion (arm rings and ingots), and a silver pectoral cross. These were above a lower layer with more Viking style bullion, but also comprised a number of gold items and a vessel full of a broad range of small objects. It is the vessel and some of the contents that will be discussed in this paper.

The assortment of artefacts in the vessel was very diverse culturally, stylistically and chronologically. There was also a wide variety of materials represented, including glass, rock crystal, stone, silver, gold, copper alloy, niello, ‘dirt’ balls, leather, and textiles made from silk and bast fibres.

Methods

Detailed recording before and during conservation relied on a range of imaging techniques, which also pointed the way to further analyses and study. The vessel was CT scanned by Dr John Reid at Borders General Hospital before it was unpacked for Treasure Trove valuation. All objects were X-rayed using variable parameters to assess both organic and inorganic components of the hoard. Optical microscopy with Z-stacking capability allowed detailed digital recording of areas of technological and material interest; this was coupled with SEM EDS to explore materials more fully. The British Museum, as partners within this project, provided CT scanning of complex objects and ‘bundles’ which allowed examination of surface details obscured by adhering textiles and wrappings, and the data enabled the reconstruction of the vessel (by the Digital Design Studio at the Glasgow School of Art and Steve Dey of thinksee3D) as a three-dimensional model and subsequently printed as an acrylic model for study and display. Micro-CT scanning was tried on some smaller complex items.

Results and Discussion 

The main focus of much of the analyses was on the complex range of both organic and inorganic material contained within the lidded vessel which itself had been wrapped in wool and bast fibre textiles which obscured all surface details.

The vessel was tightly packed with artefacts. During unpacking, a series of X-rays as well as photographs confirmed the position of objects in relation to one another. There is a vast array of information, but several brief case studies will help illustrate the some of the work.

1. Visualising the vessel: after it was emptied CT scans undertaken at the British Museum revealed the intricate and unusual style of decoration used on the vessel surface, which appeared to show its origins were central Asian, unlike similar containers found at this period which are provenanced to continental Europe. The CT scan also allowed an acrylic model of the vessel to be made for interpretation and exhibition; this was a very effective way of displaying the vessel without pressure to remove and potentially destroy the important textile evidence covering the object.
2. Dirt balls: two small unobtrusive objects found within the vessel are of unknown use and origin. Surface SEM EDS showed the presence of gold and bone on the surface; CT scanning at the BM confirmed the gold was present throughout these objects so was not caused by surface contamination
3. Textile wrappings: these were present in various stages of preservation, but microphotography and SEM analyses helped confirm where even the most minute traces of textile were preserved in corrosion products, allowing us to deduce that several of the objects had originally been wrapped in cloth.
4. Different construction of brooches: although superficially these were three ‘pairs’ of brooches, X-rays and SEM EDS have demonstrated different construction techniques such as the means of applying bosses, back plates and decoration showed different manufacturer’s techniques were used.
5. Identifying a ‘touch-stone’ – Surface imaging and SEM EDS analysis of a relatively common dark schist, cut and facetted like a gemstone, and placed in a very elaborate gold setting – demonstrated that it was used for assaying the quality of gold.
6. Construction of gold embroidered braids: micro-CT confirmed that these complex six strand braids were two separate braids ‘sewn’ together with the elaborate use of gold covered silk thread in an unusual form of embroidery.

Conclusion

Although this project has not developed new methodologies within heritage science, microimaging has allowed ground-breaking archaeological insights into a complex group of objects.

Collaboration between institutions, including the British Museum and Glasgow University, has again shown the importance of cross disciplinary work within Heritage Science.

As much information as possible has been recorded and retained both on the original condition of the objects and information revealed during conservation. Detailed imaging throughout the process of discovery and research is retained and can be revisited, which is essential for both documentation and future work.

Scientific imaging of the Galloway material has been used in exhibitions and publications to make the scientific approach to the study of archaeological material both accessible and intriguing. These new discoveries and interpretations of material from the Galloway Hoard are opening up questions on existing archaeological interpretations of the Viking Age and supplying new information for future dialogue.

References

GOLDBERG, M. and DAVIS, M. (2021) The Galloway Hoard Viking-Age Treasure.   Edinburgh: NMS Enterprises Ltd.