Portable X-ray fluorescence and its applications to the investigation of ancient metal artefacts

X-ray fluorescence (XRF) analysis has long been used to investigate ancient metal artefacts. The long-lasting success of this technique is due to its intrinsic non-destructivity, which makes it attractive for cultural heritage applications, often requiring strict respect of the artefact physical integrity. Portable devices prove particularly effective because they can be used in situ, with no need to move the investigated object to the laboratory. This paper shortly discusses the requirements that a portable device has to fulfil for use on ancient metals. A measurement of the alloy composition, which is at the same time accurate and non-destructive, may be difficult or even impossible to carry out, due to the presence of corrosion products, whose removal is seldom permitted. Here, emphasis is given to methods that, though respectful of the artefact integrity, are capable to make the most of XRF potentialities. The discussion of significant case studies shows that, in many cases, only differences matter and accuracy is not a major requirement. In practice, one can perform relative instead of absolute measurements, more simply and with fewer restrictions.