# Pulsed Thermography Applied to the Study of Cultural Heritage
## 3 Results
### Characterization of Painted Decoration on Archival and Library Supports
#### 3.3.2 Recovery of Damaged or Buried Features in Paint Decorations  
_Pentimenti_  
In the study of illuminations, as in the case of other kinds of paintings [76], an interesting aspect concerns the analysis of the _pentimenti_, mostly based on the detection of the underdrawing which may appear different from the final form of the illumination [52]. For instance, in the lower scene of the illumination of _folio_ 239 _verso_ belonging to the mid-14 th century manuscript Liber Regulae S. Spiritus De Saxia (_Archivio di Stato di Roma_), a _pentimento_ can be observed (Figure 11). In this case,  
Figure 10: Antiphanory, XV century, _Bibliocea Angelica_ of Rome. (**A**) Photograph of the illuminated letter of _folio_ 142 _recto_; (**B**) thermogram before the restoration showing the detachment of the gold leaf from its substrate, indicated by the arrows; (**C**) thermogram after the restoration [51]. Figure 9: Antiphanory, XV century, _Bibliocea Angelica_ of Rome. (**A**) Photograph of the illuminated letter of _folio_ 117 _verso_, where the arrows indicate the _craquelure_; (**B**) thermogram showing extended detachments from the substrate around some of the observed cracks marked by circles [51]. the thermogram in Figure 11B, obtained with two flash lamps set to 500 W, shows a different position of the head of the monk whose orientation is shown to be different from that in the final painting, where a dense blue paint layer has been then used in order to efficiently cover the change. The optothermal mechanism that allows the IRT to reveal the underdrawing can be explained in the following way. The incident visible light, though scattered when crossing the external painted layer, gets selectively absorbed by the various features, including the preparatory drawing, at the substrate, thus inducing a contrast of the local temperature distribution and therefore of the IR radiation emitted in the 3-5 \(\upmu\)m range [51]. Because of its larger wavelength with respect to the visible, the emitted IR radiation maintains a substantial unscattered component while traveling back through the painted layer to the camera and generates the thermographic image of the underdrawing. Another interesting application of IRT consists in the possibility to investigate the effect of damage on parchment artefacts, which causes the loss of the surface paint layer. Currently, MSI and HSI analysis are routinely employed to study pictorial and graphic features [77] and for the recovery of the original contrast between pigments and supports in damaged parchment manuscripts [78]. In particular, recent studies have demonstrated the potentiality of UVF in enhancing the readability of faded features in manuscripts [79]. Specifically, UVF has been shown to be useful in identifying the retouches and the damaged areas through the study of their characteristic UV luminescence [80]. In this paper, in order to study these kind of features, a XIV century illuminated copy of the Divina Commedia by [PERSON] (\"ms 1102\"of the _Biblioteca Angelica_ of Rome) has been analyzed by IRT. The manuscript contains thirty four illuminations, which appear faded and in some cases partially erased. For instance, in the case of _folio_ 15 _verso_, IRT allows researchers to enhance the contrast of some faded figures (Figure 12). The thermogram (front face heating by two flash lamps set at 500 W) of such an illumination (Figure 12B) shows several elements, such as the head and the wing of the demon highlighted by the dashed circle that have partly lost contrast in the photograph of Figure 12A. This is due to the presence of residuals of the materials used to make the original paint decoration that can induce differences in the local light absorption and emission properties and therefore in the local IR emission with respect to surrounding ones, causing the thermal contrast in the thermogram.