## 1 Introduction
The most commonly used techniques are scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS) [5], X-ray fluorescence (XRF) [6], X-ray powder diffraction (XRPD) [7], infrared spectroscopy (FT-IR) [8; 9], Raman spectroscopy [10; 11; 12], high-performance liquid chromatography (HPLC) [13], gas chromatog  
Figure 1: **(a)** Image of the east wall before restoration; **(b)** detail of the pervasive paint film exfoliation of the area highlighted in **(a)**. raphy coupled with mass spectrometry (GC/MS) [14; 15], pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC-MS) [16]. In the last decade, the literature on the scientific analysis of wall paintings, a non-renewable form cultural heritage, has increased, with particular interest being paid to the study of the origin and mechanisms of deterioration of the pigments and their distribution and chemical composition [17; 18; 19; 20; 21]. The pigments used in the 20 th century have been investigated in easel paintings [22; 23; 24; 25], while their use in wall paintings is less studied [26; 27]. The art movements of the early 20 th century throughout Europe were mainly based on the \"_a fresco_\" technique, focusing on the revival of rural painting, leading to the rediscovery of the traditional wall painting techniques [27; 28]. Many artists, however, also because of the introduction of new synthetic pigments, experimented with different methods such as the \"_a secco_\" or the mixed dry/fresh techniques [27; 29]. In the \"_a fresco_\" method, pigments are applied to the freshly prepared plaster and are bound through the lime carbonation process without using organic binders. Frequently, the final touches of the works are carried out \"_a secco_\", using an additional organic material such as oil, animal glue, casein, or egg. On wall paintings, organic materials are more difficult to identify and are more susceptible to deterioration than inorganic ones [29]. An interesting work by [PERSON] et al. [27] reports on the wall paintings of 1930 in Venice (Aula Magna of the Ca' Foscari University) by [PERSON] (1885-1961), a famous painter of the first half of the 20 th century, and it is focused on his pictorial technique. Most of the painting, in particular, the large monochromatic background, were executed according to the traditional \"_a fresco_\" technique. However, the morphology of the principal figures' stratigraphy suggests the \"_a secco_\" technique, with egg yolk and traces of casein and arabic gum as binder for pigments based on zinc, titanium, chromium, and iron. In a recent study of [PERSON] et al. [30] on wall paintings of the same period as that of [PERSON], made between 1924 and 1926 by famous Italian artist, [PERSON] in the Saint Nicolas de Myre Church at Semsales (Switzerland), the painting technique of the artist was studied. The results reveal that the painter experimented with, in addition to the traditional \"_a fresco_\" technique, the \"_a secco_\" technique on existing plasters, in particular in association with modern pigments (for example zinc white, cobalt blue, synthetic alizarin and ultramarine blue, cadmium-based yellow, and chromium-based green synthetic pigments). In this work, a total of 12 micro-fragments of the painting layers were collected and analyzed by means of micro-Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy, and gas chromatography coupled with mass spectrometry, to identify pigments, mortars, and binding media. We believe that this study will enable the attainment of deeper knowledge, which is a significant requirement for the conservation and restoration of these modern wall paintings.