The application of a non-destructive XRF method to identify different alloys in the bronze statue of the Capitoline Horse

This work reports the results of non-destructive, energy-dispersive XRF analyses carried out on a Greek bronze statue, called the Capitoline Horse, to identify non-original parts on the basis of reciprocal compositional differences. The experimental method consists in mapping the surface of the object with a significant number of measurements (on the order of hundreds) by means of a portable spectrometer. If the net countrates of the detected elements are considered as variables, it is possible to study the clustering of the data points and derive a characteristic ‘fingerprint’ that can be used to distinguish among different alloys. This nondestructive method, which is based on the comparison of qualitative data, does not involve measurement of the alloy composition. Its application to the alloys of the Horse led to the identification of some parts as not belonging to the original casting; such conclusions are in very good agreement with the technical and stylistic analyses of the statue.