ADVANCED MATERIALS & PROCESSES | JANUARY/FEBRUARY 2025 22 This article summarizes the more common analytical techniques for studying ancient metal artifacts, illustrated by case histories from the authors’ experience. An overview is provided in Table 1. There are two main classifications: noninvasive and invasive techniques. This distinction is of prime importance because some ARCHAEOMETALLURGICAL MATERIALS CHARACTERIZATION Combinations of descriptive and analytical techniques with case studies provide essential information about ancient metallic objects. Omid Oudbashi,* University of Gothenburg, Sweden Russell Wanhill,* Emmeloord, the Netherlands *Member of ASM International is required, then invasive analysis methods are needed. The scientific techniques are mainly complementary, but there is overlap (synergy) that can result in improved assessments. Composition and metallography analyses provide much information. Although fracto- graphy can be useful it is rarely done, and an example is given[1]. EGYPTIAN SILVER VASE A vase was investigated by visual inspection, x-ray radiography, compositional analysis (SEM + EDS), SEM metallography, and fractography. Non- invasive images (Fig. 1) allowed stylistic identification of an Egyptian provenance (Ptolemaic period, 300–200 BC), revealed brittle cracks, and an extensive old restoration that likely used gutta-percha, a rubber-like material. Detailed investigation of (very) small samples showed that the vase was a 97 wt% silver alloy, rendered fragile by a combination of retained coldwork, long-term age embrittlement, and stress corrosion cracking (SCC)[2]. The fragility dictated against improved restoration except for surface cleaning and applying an anti-tarnish coating. BRONZE AGE VESSEL Figure 2 shows a typical vessel from a Bronze Age cemetery in southwestern Iran, dated to the third millennium BC[3]. The vessel is fragmented, heritage objects may be too rare or valuable for invasive sampling, or there may be ethical objections to certain types of examination. Considerable information may be obtained without taking samples. However, most information is descriptive rather than quantitative (surface chemical analysis). If detailed knowledge TABLE 1 — SUMMARY OF ANALYSIS TECHNIQUES AND PURPOSES Noninvasive techniques Purpose Visual inspection Identification, provenance, corrosion appearance Macrophotography and stereo binocular microscopy Condition: damage, corrosion, missing pieces, any previous restorations, surface details X-ray radiography Hidden damage, e.g., cracks, missing pieces Surface chemical phase analysis: various techniques, e.g., XRF, SEM + EDS/WDS, micro-Raman, micro-XRD Corrosion products, including patinas, alloy surface and fracture surface compositions Invasive techniques Purpose Chemical composition analysis Identification of alloy/metal and corrosion Optical and SEM metallography Manufacturing details, corrosion layers Phase analysis (XRD, Raman) Corrosion products and layers Fractography, mainly SEM Cracks, also in detached pieces
RkJQdWJsaXNoZXIy MTYyMzk3NQ==