Mary Davis

This paper presents a novel method and terminology to identify and describe textiles from ephemeral traces in
metal corrosion products. Since the 1980s, mineralised textiles (positive and negative casts in Janaway’s ter-
minology) have been an important source of archaeological evidence. A major issue now is the identification of
textiles in metal corrosion products when only faint traces remain. These traces no longer appear like textiles and
are vulnerable to misinterpretation. Confused with metal dendritic structures or the form of corrosion products
themselves, they are often lost through handling or cleaned off through conservation practices. This loss is
cumulatively significant. To remedy this issue, this paper defines and characterises the form and structure of
ephemeral traces of archaeological textiles through examination of metal corrosion products on a Viking Age
hoard from Scotland. It defines a new terminology to supplement Janaway: petal shapes, remnant textile surface,
ghost textile surface. The analysis follows an investigative inquiry from assessment to laboratory analysis using a
Dinolite portable digital microscope, optical light microscopy with Z stacking and scanning electron microscopy
(SEM). The results allow the secure identification of textiles from previously unidentified corrosion features. The
method has wide applicability to corroded archaeological metal objects and has the potential to significantly
increase the identification of textiles associated with metals and transform current understanding of hoards

IntroductionThe black spacer plate necklaces and bracelets of the Early Bronze Age (Figure 1) are among the most technically accomplished prestige items of this period in Britain and Ireland. There has been much debate over the years as to whether these artefacts and other prehistoric black jewellery and dress accessories are the product of specialist jetworkers based around Whitby in North Yorkshire — Britain’s only significant source of jet. As early as 1916, for example, Callander was arguing that the Scottish finds had been made using locally available materials — cannel coal, shale and lignite — rather than Whitby jet. There has also been much confusion over the identification of these various materials. Flirthermore, the conservation of newly discovered jet and jet-like artefacts can be problematical, and the correct identification of raw material is important in determining the best method of treatment.

There have been several references to white material found within the incised decoration on prehistoric ceramics, but no comprehensive study to evaluate this material. This project has used a combination of scanning electron microscopy, X-ray diffraction, ultraviolet fluorescence and
infrared photography to identify the material present, and assess the extent to which it is preserved in Early Bronze Age material from the National Museum of Wales. There are also indications for the use of red and black as deliberate colourants on these pots.
Often prehistoric artefacts, particularly ceramic vessels and sherds, were thoroughly cleaned when excavated, but some still contain visible traces of deliberate colouring on their surfaces and within the incised and stamped decoration. It was felt that an initial study, which noted the extent and type of the colours used, would highlight the occurrence of this phenomenon, and that further investigations here, in other institutions and on newly excavated material could be carried out with a view to noting and retaining relevant evidence.

The Caergwrle bowl is an iconic archaeological object housed at the National Museum of Wales which is believed
to represent a Bronze Age boat. It was manufactured from shale with an applied decoration in tin and gold signifying shields, oars and waves. Since its discovery, its materials of manufacture, technology and archaeological significance have been studied by many specialists.
The incomplete and broken bowl was found in 1823 by a workman near Caergwrle Castle, in north Wales. Records show it was restored at the British Museum between 1912 and 1914; this reconstruction was mainly made from wax, plus various adhesives used to reattach the decoration. Since then, although the restoration has stood the test of time in many respects, there have been increasing problems with its physical stability. In 2007 the bowl underwent re-conservation. Old repairs were removed revealing new evidence of the original construction
techniques and those used in its restoration.

The Abergavenny Hoard is a recently discovered collection of late Saxon and Norman silver coins, the details of which were badly obscured by corrosion products and iron concretions. A Q-switched Nd:YAG laser, using near infrared radiation at 1.064 μm, was employed to clean the hoard
Detail retained on the surface of the coins after laser cleaning included rough out marks and polishing marks from the original die, as well as the legend. From this evidence surface damage appears to have been minimal, and the treatment very successful.

The principle aim of the thesis was to examine the technology of Late Iron Age decorated metal
work at a time of dynamic change from both internal and external factors. The objects chosen for
this study were predominantly from dry land hoards, and superficially had many aspects in common.
The majority of these hoards were deposited in Britain in the mid first century AD (slightly later in
the case of Middlebie in south west Scotland), and located in areas of attested historical conflict with
the invading Roman army.
Predominant amongst the kind of objects in the hoards were those associated with horses and carts
or chariots; an artefact type of social and historical significance to native British Iron Age societies. It
is argued that the manufacture, use and deposition of these objects were important factors in
maintaining relationships between different Iron Age groups in the face of threats from an invading
force.
Chemical analysis of objects from this period is important. The first century AD witnessed both
technological sophistication and conservatism as the Iron Age metalworkers confronted the
introduction, through continental influence and the Roman army, of new materials such as brass,
and the re-introduction of piece moulds and leaded copper alloys. Coloured Roman glass was also
introduced and used in many parts of Britain, but Insular La Tène style metalwork continued to be
decorated using sealing wax red glass (a specific Iron Age technology). On the whole, an innate
conservatism in object styles and materials was maintained, irrespective of acquired knowledge and
the availability of new technologies. In fact, Late Insular La Tène art developed and flourished, as
some indigenous Britons adopted a strong identity through the use of specific objects, technologies
and artistic styles; recognisable throughout large parts of Britain.