In search of color traces in ancient stone materials

Although many ancient civilizations are known to have made use of polychromy on sculptures and in general on stone artifacts, today much of these colors have been lost. For this reason, in the minds of a very large majority, the original stones have remained un-colored until today. In recent years a strong interest focused on the study of the original polychromy on ancient sculptures has emerged1. The small amount of these traces lead to a new approach for their characterization in order to limit sampling and hopefully, avoiding it. The non-invasive approach permits the examination of a very large number of artworks with a virtually limitless number of analytical acquisitions allowing to perform measurements in situ. Already during the measurement process, this approach leads to a fundamental exchange of views among scientists, archaeologist, conservators and museum experts. The application of a protocol based on imaging techniques integrated with data obtained from single spot techniques such as X-Ray fluorescence (XRF) and Fiber Optic Reflectance Spectroscopy (FORS), provides high-quality information. In this paper some examples of analyses conducted in different contexts from museums to archeological sites will be presented. These analyses are included in a wider research project aimed to enlighten the use of colors on the sculptures in ancient time and to better define materials used in the past2,3. In this context particular attention will be devoted to the use of organic materials.