# Research on the Organic Binders in Archaeological Wall Paintings
## 4 Exploring Research Results
### Invasive Techniques
As for the organic binders, the investigations carried out with chromatographic techniques, have shown differences between the wall paintings of the domus and the Temple. Protein-based binders have been found in _domus_ (possibly egg and animal glue), whereas in the temple, the use of drying vegetable oil is proposed [84]. [PERSON] et al. (2007) have carried out a study on the wall paintings in the Protaton Church (1295) on Mount Athos, Greece. The purpose of this work was to understand whether these paintings were made according to the traditional technique of the traditionally defined \"Byzantine affresco\", with lime water as the only binder. Instead, they demonstrated, using gas chromatography/mass spectrometry, that these mural paintings were realized using both _affresco_ and a _secco_ technique. For the a _secco_ technique had been used egg together with a modest quantity of animal glue [85]. Multidisciplinary research was conducted on the first cycle of paintings of the church of Santa Maria delle Cerrate, an italo-greek monastery, most likely built in the 12 th century. Microscopic, spectrophotometric and chromatographic techniques were used. The pigments were identified, and it was seen that they were applied both _affresco_ and with egg-based tempera [86]. A study was carried out during the restoration of the medieval wall paintings of the Dome of the Baptistery of Parma, which for the type of degradation presented particular lifts of the pictorial film. By GC/MS, milk has been identified as the binder of pigments [38]. In a study of the wall paintings of the Cathedral of Cremona, innovative guidelines and a flow chart were provided for the identification of binding materials of a protein character [87]. Reference proteinaceous binding media of the kinds historically used in painting (specially prepared for this study) and samples collected from the wall paintings of Cremona Cathedral were analyzed by GC-MS. The data have been processed by several multivariate chemometric techniques, such as cluster analysis, principal component analysis, factor analysis and SIMCA technique in order to classify the binding media of the ancient works of art on the basis of the proteinaceous material used. The description of ancient samples was possible by the joint use of SIMCA technique and factor analysis [88]. An overview of application of chemometrics for the description of cultural heritage has been provided [89]. The principal component analysis of painted plasters acid soluble components and aggregate granulometric distributions and multivariate characterization of the mass spectral and of the amino acid 'fingerprints' of proteinaceous binding media in mural paintings of the Cupola of Florence Cathedral points out the differences in both plasters and binders used by [PERSON] from those used by [PERSON], evidencing the peculiarities in the painting technique adopted by each artist [90]. [PERSON] et al. (2007) examined various Chinese art artifacts, using Py-GC-MS technique. Among the various materials identified Tung oil, also called \"Chinese wood oil\" has been identified as binding medium of wall ancient Chinese palace architecture paintings [91]. A paper by [PERSON] et al. (2016) have studied black residues of supposed binding media in a tomb archaeological site of the [PERSON] dynasty (618-907 AD), which was one of the most prosperous periods in the ancient Chinese history. The study was conducted using FTIR and GC-FID. The results of the analysis indicated that the black residue was indeed the binding medium, consisting of a mixture of animal glue and egg [92]. [PERSON] et al. in a recent article, illustrate the characterization of organic materials used in the gilding decoration of wall paintings in Kizil Grottes, China, using Py-GC-MS technique. They saw that drying oil was used as the mordant for the adhesion of tin foils, while lac resin was employed for gold foils [93].