## 4 Results
### Micro Destructive Investigations
#### 4.2.4 PLM and ESEM-EDS Investigations  
The main stratigraphic features related to plaster, primer and paint layer (organised by hue) were investigated by PLM and ESEM-EDS. A detailed synthesis of data obtained by integrated analyses is discussed below and illustrated in Table 3. PLM observations showed that the supports of the paintings are composed of two layers of plaster with an irregular thickness. The plasters are composed of a lime-based binder with silicate and carbonate aggregates (Figure 9a). The aggregate consists of quartz, feldspars, plagioclase (albite), muscovite, hornblende, ilmenite and opaque minerals. Figure 8: Sample My44: Raman spectra of carbon black. Figure 7: Sample My33: Raman spectra of (**a**) hematite; (**b**) vermiliom; (**c**) quartz (the italic bands are from anatase); (**d**) anatase. As EDXRF analysis has provided the elemental composition of the bulk; the SEM-EDS allowed us to understand the elements' stratigraphic location and the reciprocal relationship between them, such as, for example, that arsenic is rarely associated with sulphur. An ESEM-EDS analysis of plasters (Table 3) detected a high content of Ca and a low amount of Si, Fe, Ti, Al, K, Mg, Na, and traces of Cl, P, S. The presence of calcite, quartz, aluminiosilicates, Fe-oxides and Mn-oxides constituting the aggregate was confirmed by EDS analysis. In most of the samples, a whitish discontinuous primer layer was observed. UV light highlighted a yellowish fluorescence, probably related to organic compounds (Figure 9b). The primer is composed of As-containing compounds and silica/magnesium-based clays (sample MY44; Table 3) to indicate the possibility that As can be contained in magnesium clay [59]. According to the influence of ancient Indian painting tradition [42; 60], the Burmese technique uses clayey plaster [42; 61]. Arsenic is mainly present as oxide (e.g., arsenolite) as suggested by the EDS analysis of the primer, (e.g., sample MY31 and MY33 bis; Figure 9a,b), and the absence of S allowed to refuse the occurrence of orpiment/realgar. The function of such primer could be related to its light-reflecting properties. PLM observations revealed very thin paint layers (Table 3) with an irregular and discontinuous surface. Sometimes the paint layers are detached from the plaster, probably because of the deterioration processes. ESEM-EDS carried out on the samples surface detected in some cases Ca and S related to calcium sulphate that could be related to a modern restoration intervention. In the reddish paint sample (MY33; Table 3), a thin and discontinuous layer with a maximum thickness of 48 \(\upmu\)m contains red coarse-grained and black particles (Figure 9c). ESEM-EDS microanalysis detected Hg, S and As, related to cinnabar/vermillion and As-based compounds. The presence of Si, Mg, Al, K, Fe and Ti may be due both to Fe-based pigments (red ochre) and clayey matrix [50; 51]. Traces of P and Cl may be ascribed respectively to animal glue and chloride compounds. The latter is probably due to past restoration interventions. Optical and ESEM microscope with EDS analyses of the brownish layers (samples MY32 and MY45e; Table 3) showed an irregular dark brown layer containing brownish particles in which Ca, Si, Al, Fe, K, Hg, S, Mg are the main elements detected. Earth pigments and a few cinnabar particles are the main ones responsible for the colour (Figure 9d). In addition, a few As-based particles and Cr-Fe based particles were also found. The blackish samples (MY31 and MY44; Table 3) are characterised by a thin (30 \(\upmu\)m) and uniform black layer with angular carbon black particles and opaque minerals. The EDS analysis detected C and S, confirming a charcoal black origin [62], while Ca, Si, Fe, Mg, Na, K, and Ti are related both to calcite and natural earth pigments [63]. Arsenic was detected in all the different painting hues, seldom linked with sulphur, and related to or regular.