When analysing artefacts, a rather simple notion should be kept in mind in terms of material composition; the larger the object, the more likely it becomes that the object consists out of multiple parts. The converse holds true for smaller objects; the smaller the object, the more likely it is that the object is made from a single component. The complexity of the object also plays a role in the variety of materials and components that are employed. For example, it would be nonsensical to create a small (4 cm x 3 cm) bronze statuette from individual components if the technology exists to cast it as a single unit. On the other hand, it would be pointless to waste a huge amount of metal to cast a larger (30 cm x 40 cm) bronze statue from solid bronze, if individual components, such as the torso, could be filled with cheaper material (such as a clay or wooden core).
3.3.1 Material Type and Conservation
As the name infers, composite artefacts consist of a number of different components, which in most instances differ in material type (i.e. metals, organic elements, fired clay, etc.). These components all react differently to environmental conditions; undergoing individual processes of deterioration and deformation, in different ways and at different rates. Although these processes are highly individualised, the resulting products of deterioration can have adverse effects on the preservation of surrounding materials (Dalewicz-Kitto et al. 2013: 35).
In addition, deteriorating materials may become so fragile over time that their neighbouring components pose a threat to their longevity. For example, textile components may become so fragile over time, that contact with their adjacent rigid or abrasive metal components may cause damage (Breeze 2008, 1). Another example would be the deterioration of organic
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components; in which case the absorption of environmental moisture would pose a direct threat to surrounding metals or alloys.
A further example comes from the research conducted by Tornari et al. (2008) on the holographic inspection of dimensionally responsive artwork materials. In artefacts containing hygroscopic materials – such as wood, bone, adhesives, varnish and lacquer – changes in humidity and temperature may lead to dimensional changes. These dimensional changes create strains that adversely affect mechanical integrities, such as the adhesion strength between constituent layers. Because composite artefacts consist of diverse materials with differential porosity, hygroscopicity and elasticity, the resulting stresses usually appear heterogenic or non-uniform (Tornari et al. 2008, 8402).
3.3.2 Material Type and Non-Destructive Evaluation
Researchers must also be cognisant of the fact that, while examinations are conducted within the framework of NDE, certain materials are vulnerable to radiation exposure. This holds true, not only for organic materials included in the original design of the artefact, but also organic compounds applied during restoration. For example, what may be non-destructive towards the metal alloy, clay core or faience inserts, may not necessarily be non-destructive towards the organic polymer adhesive used in restoration efforts. One specific example of such an instance presented itself in this research, but details will be provided in Chapter 7.
3.3.3 Implications for Interpretation
Certain mechanical and chemical processes cause physical anomalies that can be linked to long term aging and/or the object‘s contemporary exposure to unfavourable environmental conditions, rather than ancient production methods or use-wear. For example, certain processes, such as the flaking of gold leaf, could be interpreted as the result of decaying adhesives (due to rising humidity), rather than the lack of heat treatment during ancient manufacturing. In addition, one should also consider the effects that certain antique restoration efforts had on objects. In the early years of museum conservation and restoration, chemical treatments were often performed without the long-term effects of such treatments being known. At first, these applications might appear beneficial, but over many decades, the treatments themselves begin to fade or flake. This may cause an object to have an outward appearance that may result in an erroneous determination of age.
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3.3.4 Period-and Culture-Specific Variables in Production
Ancient artefacts often contain ―hidden treasures‖ that take the form of previously unknown or unidentified components and materials, which may elucidate information on manufacturing processes, object use and period of origin (Lehmann et al. 2005:68). For example, in the case of ancient metal artefacts, these objects represent unique compositions that were made long before the age of industrial standardisation (Zhang et al. 2009, 80). Through physical characterisation and identification of diagnostic features, we are able to ―reverse engineer‖ certain ancient fabrication processes (Artioli 2007, 899; Rant et al. 2005). In the process, we foster a greater appreciation of ancient technologies and craftsmanship within their respective periods and cultures (Adriaens 2005, 1504).
Within the context of this thesis, the analysis of composite artefacts will allow the researcher to collect and compare data on several different material types within a single object. The kind of diagnostic information that is obtained will depend on the type of material (metal, clay, leather, etc.) under investigation (Adriaens 2005, 1508). For example, in the analysis of metal objects, physical anomalies may divulge information on the type of metal alloy used, as well as the manufacturing techniques (casting, hammering, bending, etc.) that were employed. Complementary information can help us to understand ancient trade and sourcing of raw materials, production methods, technological evolution and even regional skills development. These elements can then be used as diagnostic features in the assessment and subsequent authentication of artefacts.
Although we would like to readily identify period-and culture-specific variables in production by comparing our results with similar objects from same cultures and/time periods, this is not always possible. In fact, diagnostic features identified among similar objects from different cultures, time periods and geographical regions can be used in comparative analyses, as physical anomalies are often related more directly to material properties than cultural influences on production. In simpler terms, we should not limit ourselves to the study of ancient Egyptian bronze statuettes when, for example, we are investigating a specific anomaly (chaplets and casting holes). As similar production techniques were employed in bronze casting throughout much of the Ancient Near East (ANE), we may identify similar anomalies from objects that originate from other cultures. We should therefore look further afield and compare technological similarities across different cultures. In defence of this approach Scott (1991, 74), in his study of Pre-Hispanic gold wire from South America, argues that,
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The use of the same, or similar, technologies for the manufacture of wire in the New World as compared to the Old need not be problematic. The careful observation and manipulation of gold by ancient craftsmen could explain why technological processes are often the same, without postulating the transmission of knowledge by diffusion.
Along similar lines, James‘s (1972, 41) statement on the continuation of production methods and techniques for gold beating, provide additional support for this argument:
Modern gold-beaters have declared that the attitudes adopted by the beaters, and the nature of the anvil and hammer used, suggest that the ancient beating technique was very similar to that used in Europe since at least mediaeval times.
With both statements considered, we must keep the following point in mind during comparative analysis. Similar objects may share similar production materials and methods – and by extension, physical phenomena – even though they were made by ancient cultures that existed worlds apart. The same holds true for objects that exist within the same culture but are separated by decades or even centuries.
In addition, it is not only well-curated, authentic objects that can serve a purpose within comparative analyses. Surprisingly, we can (to a certain extent) consider modern forgeries as period-specific variables in production. Although these objects mimic their ancient counterparts stylistically, the methods employed in their production will differ vastly, thereby serving as chronological markers in their own right. With specific reference to the usefulness of modern forgeries, Schorsch (1988, 41) provides us with basic guidelines for comparative analyses that are not always considered – our consultation of forgery styles, methods and techniques as chronological indicators and authentication markers:
If it can be established that a piece is a forgery, and that almost invariably it is an assemblage of features that must be examined and judged, this recognition may be useful in defining the limits of what one can expect to observe on ancient examples.
In short, the identification of forgeries may be controversial (in that they expose our own limitations in terms of curation), and may urge some traditionalists to denounce the worth of
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forgeries all together, but these objects still hold value – if only in their potential to help identify other forgeries.