Among all the physico-chemical methods of study of painted art works, the "non-destructive" methods are undoubtedly the most preferable. The success of the "non-destructive" methods provides precious information for utilisation in the authenticity tests, the evaluation of the microstratigraphic profile structure that characterises the construction technology, the localisation of covered signatures or dates, and the hidden interventions whether young or old to the aesthetic value by studing the physico-chemical behaviour under electromagnetic radiations of different wavelengths.