The mosaics, cause of their nature, are subject to various kind of deterioration. Therefore, for a long period their preservation coincided with the detachment from the support and their placement in suitable museum environments. Currently the ambition of the restoration is the conservation in situ, whether it concerns floors or wall coverings, and a correct diagnosis of the causes of decay is very important.

The study of the mosaics is aimed to different classes of materials: first of all, it is fundamental the characterization of bedding mortars and the corroboration of their state of conservation.

This can be done reading stratigraphic cross and thin sections using techniques such as ionic chromatography for the determination of soluble salts and FT-IR spectrometry for the recognition of organic substances. In addition, these tests provide historical information on executive techniques, and are also useful for the development of the mortar needed for the restoration, which should be as similar as possible to the original.

Then there is the tesserae classification, which may be made of marble or other stones in the case of mosaic floors, and generally of glass for mosaic walls. In the first case, the techniques used go from the macroscopic recognition of marbles, where possible, to the diffraction and the evaluation of isotopes and trace elements for the exact identification of the geological species. Instead, on the glass mosaic can carry out a SEM-EDS, analysis, which allows to judge the conservation status and to identify the type of glass.