ADVANCED MATERIALS & PROCESSES | OCTOBER 2023 18 In recent decades, significant consideration has been given to the development and application of noninvasive microanalytical techniques for the analysis of ancient and historic metals. The goal is to ensure that detailed information can be obtained regarding fabrication technologies and the subsequent alteration of objects without the need for destructive sampling. These techniques can provide a range of information about chemical composition and microstructure, failure analysis, corrosion and deterioration mechanisms, as well as the physical condition of different metals and objects. These methods include multi- elemental bulk analysis, e.g., micro-xray fluorescence spectroscopy (µ-XRF), micro-particle-induced x-ray emission spectroscopy (µ-PIXE), laser induced breakdown spectroscopy (µ-LIBS), and molecular phase analysis, e.g., µ-Raman spectroscopy and micro-x-ray diffraction (µ-XRD). This article presents a case study of the application of noninvasive µ-XRF to identify the alloy composition in a 5000-year-old silver-base object from Iran. CASE STUDY: SMALL SILVER BULL The object of this study, purchased by The Metropolitan Museum of Art in 1966, consists of a kneeling bull clothed in a robe with a stepped linear pattern and holding up a spouted vessel (Accession Number 66.173, Purchase, Joseph Pulitzer Bequest, 1966). The anthropomorphic pose of the bull is consistent with the art of the Proto- Elamite period in Iran (ca. 3000 BCE) to which this object has been attributed. A tour de force of ancient metalworking expertise, the bull is composed of 15 pieces of worked silver joined together with silver solder. Previous invasive chemical analyses of samples were performed by thermal neutron activation (NAA) in order to identify the chemical composition of silver alloys used to produce some of the components as well as some NONINVASIVE µ-XRF ANALYSIS OF ANCIENT SILVER OBJECT This case study details the noninvasive analysis of an ancient silver object from Iran, now in the collection of The Metropolitan Museum of Art. Omid Oudbashi, University of Gothenburg, Sweden Federico Carò and Jean-Francois de Lapérouse, The Metropolitan Museum of Art, New York Kneeling Bull awaits noninvasive examination by µ-XRF equipment. solders that were identified during its restoration[1]. The aim of the present study is to apply noninvasive µ-XRF analysis to characterize the silver alloy compositions and compare the new data with previously obtained results from the NAA technique. QUANTITATIVE µ-XRF ANALYSIS Micro-x-ray fluorescence spectroscopy (µ-XRF) or the EDXRF microanalysis technique is an elemental analysis
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