The authors analyse an icon of St John the Baptist, not yet restored, dating from the early 19th century. A first analysis is achieved by photographing with infra red and ultraviolet rays. Any varnishes which happen to be destroyed, disappear, damages are revealed, fake colours give important information on the composition of the pigments, the chance overlaying of paint may appear as well as other interference and fluorescent organic and inorganic pigments with resins used for coating surfaces. A small, portable device with a great ability for detection was used for the insitu chemical analysis. This device reveals the composition of pigments and their mixtures. Combining all this information, the art restorer can start his job with a knowledge of the materials originally used.