Throughout the proceeding sections, the relevance of chemical composition has been noted on a few occasions, and will also be referred throughout the remainder of the thesis. Therefore, a seemingly glaring omission from this thesis is the application of non-destructive chemical analysis. The question may arise: ―if so important, why not include it in this research?‖ Unfortunately, time restrictions, limited access to facilities, and the researcher‘s personal lack of experience in this field, prompted the exclusion of chemical analysis. However, since chemical analysis can form part of future endeavours (as stipulated on the final chapter‘s recommendations for future research), a brief synopsis of its value is included below.
2.4.1 Possibilities for Future Research
Future research into microstructure, chemical composition and corrosion materials can be conducted using a range of techniques. Options include X-ray Diffraction, Inductively Coupled Plasma-Mass Spectrometry, Scanning Electron Microscopy, Electronic Microprobe Analysis, Fourier Transform Infrared Spectroscopy, X-Ray Fluorescence Spectroscopy, and Optical Metallography, as well as Polarised-Light Microscopy. Examples of the applications of these works within the realms of cultural heritage diagnostics are provided in Chapter 3. While Section 2.4.1 summarises the application and value of chemical analysis in the broader sense, Section 8.3.2 will provide detailed recommendations based upon the conclusions drawn from this thesis.
2.4.2 The Application and Value of Chemical Analysis
The analytical study of metals within the field of archaeology is performed within the scope of archaeometallurgy. During the 20th century, researchers set out to identify the possible
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geological origins of archaeological metals, relying primarily on trace element analysis. However, without the addition of lead isotope analyses, which was only introduced during the 1960s, reliable provenance studies were hard to come by prior to this point (Ben-Yosef 2018, 208). Following its introduction, isotope analyses have focused on determining precise amounts of trace elements and lead isotopes (Siano et al. 2009, 672), which is considerably helpful when quantifying the lead isotope compositions of ancient bronzes, for example. Along with the main elements of bronze (copper and tin), various concentrations and distributions of trace elements (i.e. iron, cobalt, nickel, arsenic, zinc, lead, antimony, selenium, tellurium, gold, bismuth) provide metal alloys with unique elemental profiles. Decades of research has revealed much about ancient metal sources, divulging insights into acquisition strategies (such as mining), local and international trade, manufacturing technologies, ancient social structures and even cultural synchronizations between different cultures (such as Egypt and the Levant) (Ben-Yosef 2018, 209).
One of the most successful approaches to authentication is the chemical analysis of alloy composition and corrosion. The latter, as a product of natural chemical reactions, can be analysed to shed more light on the original alloy from which it developed. This is because ―the morphology of the [corrosion] surfaces and the elemental composition of the corrosion products depend strongly on the chemical composition of the alloys‖ (Constantinides et al. 2002, 100). Trace element analyses have therefore proved useful in the authentication of copper alloy artefacts.
This knowledge is of great value, as data on the quantitative elemental composition of artefacts can aid in the allocation of relative dates, as alloy compositions and metallurgical additives were often period-specific, thereby serving as chronological markers (Fortes et al. 2005, 136; Robbiola & Portier 2006, 2). The identification of elemental composition not only allows us to better understand the physical and chemical processes that occurred throughout the artefact‘s lifetime, but can also aid researchers in identifying production time and region. This is because compositional variations within artefacts are directly linked to the raw materials from which they are made (Scott 1994, 4), with raw material acquisition (mining and trade) and utilisation changing across the Metal Ages (Fortes et al. 2005, 136).
The physio-chemical and trace element compositions of both raw materials and manufactured objects, along with the thermal conditions of production (identified through microstructural
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techniques, such as ND), can illuminate multiple factors of ancient production. It can help identify the possible origins of raw materials, provide insights on manufacturing techniques and production conditions, as well as identify local and international trade routes. The latter point is made possible through the application of raw material source data, the observance of specialised localised (geographical) production techniques, as well as archaeological object provenance – all while considering the greater socio-cultural context and history of the originating culture.
It is therefore important that we identify the elemental composition of artefacts in order to place them within more accurate culturo-chronological contexts. To do so, a multi- disciplinary approach to chemistry and archaeometallurgy is required (Alberghina et al. 2011: 129), which in itself encourages researchers to employ multiple techniques to obtain complementary data. However, even though elemental analysis can provide us with a wealth of information, Schorsch and Frantz (1998, 23) remind us that chemical analysis is by no means the ―be all and end all‖ of authentication research:
We are frequently asked to what degree the materials used to make a particular object provide information about its origins. During the fifty years [by this stage, seventy] extensive efforts by many researchers have been made to answer this question with respect to both major-element and trace-element composition of a wide variety of works of art. Despite the successes achieved in certain areas, there are no immediate answers for many types of archaeological objects, and especially for those made of metal.