The diagnostic research on plastered façades is finalized to evaluate the state of conservation of the coatings and to obtain historical information, for instance regarding the sequence of decorative layers or the type of decoration.

The most common methodology to assess any detachments, hidden inhomogeneities, presence of humidity and other risk factors is the thermovision, , an absolutely non-destructive investigation.

The stratigraphic dowels are other tests to be performed on site: it can be select by scalpel blade the painting finishes over putted, up to the original preparation.

To achieve the characterization of the materials, the most appropriate analyses are the observation of stratigraphic cross sections and thin sections, possibly coupled with the scanning electron microscope with the EIMA software, the X-ray diffraction, the ionic chromatography for soluble salts, the spectrophotometry FT-IR for films and organic residues, the microbiological tests for the detection of microorganisms. Other investigations may be conducted to obtain historical data, such as the colorimetry and the pigments recognition. It is significant that these tests are not only performed before the restoration, but also during interventions to ensure the respect of the artifact and the decorations.