IRT technique applications for the detection of the plasters defects in historic buildings are widely documented by scientific literature. Previous studies demonstrated the advantages of tomographic techniques to obtain quantitative results by IRT. With a quantitative approach, the dynamic measures of IRT, versus time and maximum value of thermal contrast, allows to locate the delamination and calculate its volume inside the thickness of the plaster. Nevertheless, effects are not prominent if compared with the ones caused by the interaction between surface and irradiation. Moreover these effects are lower than the noise due to the approximation of the spectral coefficient value. Authors already showed that the multispectral evaluation of the reflectance coefficients, in the range of visible and near IR, contributes to a proper evaluation of the thermograms shot on surfaces affected by chromatic alterations. In the study case, the evolution of the surface temperature in time allows to quantify the effects of spectral absorption (absorbance) in the thermograms. By comparing the thermograms to the maps of damages and intervention, it has been possible to correlate the materials and its state of conservation to the evolution of the thermal profile corresponding to each analyzed area.