# Research on the Organic Binders in Archaeological Wall Paintings
## 4 Exploring Research Results
### Invasive Techniques
A study looked at an extensive series of standard compounds, reference pure materials, and reference paint materials prepared at Opificio delle Piretre Dure in Florence (Italian Ministry of the Cultural Heritage) Italy, simulating ancient painting techniques, using GC-MS to determine amino acids and fatty acids, and submitting the results obtained to statistical analysis [61; 62; 63]. An analytical procedure carried out on reference paint materials for the simultaneous characterization of proteinaceous binders, drying oils, natural waves, plant and animal terpenoid resins on the same microsample using GC/MS has been proposed [39]. Another paper takes it into consideration again the reference paint materials prepared at Opificio delle Piretre Dure in Florence, Italy: the fatty acid distribution for lipid binders and the amino acid content for proteinaceous media were determined by GC-MS before and after being artificially aged through exposure to UV light, under defined conditions. The Authors noted that UV aging processes do not significantly affect protein degradation binders, while influencing that of lipid binders to some extent [3]. A mini review on analytical pyrolysis to investigate organic substances on wall paintings has been illustrated. A micro-sample (50-100 \(\mu\)g) is destroyed during the analysis, but the absence of sample preparation makes Py-GC-MS a very attractive technique with a much-reduced analytical time and cost compared to other chromatographic [64]. Research of [PERSON] et al. was carried out on Neolithic wall paintings by Sos Furrighesos necropolis, a very important funerary monument in Sardinia, Italy. The use of GC-MS revealed egg in the samples taken, applied directly to the stone surface of the graves. It was believed that for the first time the use of egg binder in Neolithic mural paintings was found [65]. Another work by [PERSON] et al. examined a Neolithic hypogeum site located in Sardinia, decorated with red and black wall paintings. This is Domus de Janas (Home of the Fairies, or Home of the Witches). Again, the goal of the work was to understand the pictorial technique. The result obtained, analyzing samples from different graves, confirmed the data found in the previous study, namely the use of egg, as a binder to lay out the color [66]. [PERSON] et al. examined Myceneaan wall paintings in the \"Palace of Nestor\" in Pylos (Western Messenia, Greece), dated from the Late Bronze Age (ca. 1200 BC), for the purpose to establish the first comprehensive analytical documentation for the study of the painting techniques practiced during the Late Bronze Age. The samples studied using GC-MS and Py-GC-MS showed egg, animal glue and plant gums. The authors believe that, for the first time, tempera technique has been identified for such an early period in the history of ancient Greek mural painting [67]. A study has been carried out on the polychromy of some fragmented architectural reliefs from the Palace of Apries in Memphis, Egypt (26 th Dynasty, ca. 589-568 BCE The samples taken were studied using FTIR to identify the class of organic substances and GC-MS. Polysaccharides have been found, identified as plant gums, used as binding media, in some samples. Other fragments showed animal glue presumably mixed with egg. Another interesting information concerning the presence of synthetic wax (applied during ancient conservation treatments) and as bees wax, on the surface of the paintings [68]. A paper of [PERSON] et al. shows the analysis of a wide range of raw plant gums, watercolors, and naturally aged reference painting specimens with the aim to optimize the analytical procedure, but also to collect data for constructing a data set, which is useful for binder identification when a chemometric method such as principal component analysis (PCA) is applied. The analytical methodology was applied to the study of wall paintings (4 th-3 rd centuries B.C) of Macedonia [69].