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Fig. 6 Diffraction patterns of the binding medium from different wall paintings, along with these of the external crust formations (JM illite montmorillonite, Cc calcite, Q quartz, G gypsum and HM hydromagnesite)

Figure 6 Diffraction patterns of the binding medium from different wall paintings, along with these of the external crust formations (JM illite montmorillonite, Cc calcite, Q quartz, G gypsum and HM hydromagnesite)

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The initial samples were studied under the stereo- microscope in order to describe their surface structure and colour impression. Furthermore, the polished sections were examined under the polarising microscope. This examina-
The initial samples were studied under the stereo- microscope in order to describe their surface structure and colour impression. Furthermore, the polished sections were examined under the polarising microscope. This examina-
layers were analysed by Fourier-transformed infrared spec- troscopy (FTIR). The FTIR analysis was performed in a Bruker, Equinox 55/S spectrometer. Transmittance spectra were collected in the region of 4,000 to 400 cm’, with 4 cm | resolution. The samples were mixed with KBr and scanned 40 times, in order to reduce the signal to noise ratio. tion was mainly focussed on the stratigraphy and thickness of paint layers and preparatory layers. Another aspect was the microstructure of plaster and paint layers, in terms of characteristics such as coherence, inclusions, porosity or size of pigments.
layers were analysed by Fourier-transformed infrared spec- troscopy (FTIR). The FTIR analysis was performed in a Bruker, Equinox 55/S spectrometer. Transmittance spectra were collected in the region of 4,000 to 400 cm’, with 4 cm | resolution. The samples were mixed with KBr and scanned 40 times, in order to reduce the signal to noise ratio. tion was mainly focussed on the stratigraphy and thickness of paint layers and preparatory layers. Another aspect was the microstructure of plaster and paint layers, in terms of characteristics such as coherence, inclusions, porosity or size of pigments.
Ochre The majority of the collected samples presented colours in a spectrum from yellowish brown to orange red.
Ochre The majority of the collected samples presented colours in a spectrum from yellowish brown to orange red.
Table 2. Summary of the analytical results: The groups in the last column correspond to the plaster types described in the text
Table 2. Summary of the analytical results: The groups in the last column correspond to the plaster types described in the text
Fig. 3 SEM micrograph in back-scattered mode of a cinnabar layer in Sample CH02_S2
Fig. 3 SEM micrograph in back-scattered mode of a cinnabar layer in Sample CH02_S2
Blue pigments The FTIR analysis of the blue sample from the Church Aghios Philippos (Fig. 5: CH10_S2) presented a spectrum of low degree of resolution for blue chromo- phores. However, this is something already emerged in FTIR analysis of blue pigments [14]. The evaluation of the spectrum revealed the presence of four peaks at 924, ,030, 1,085 and 1,153 cm !, which are indicative for the presence of lapis lazuli [15]. Moreover, the presence of a weak peak at 540 cm ', which increases its intensity in the first derivative plot, is also characteristic for the stretching vibration of the S-S bond and therefore the presence of ultramarine [14, 16]. The ability of FTIR to identify sulphate compounds is of great importance for wall paintings surveys and highlights the complimentary character of IR with other portable spectroscopic techniques, such as LIBS and EDXRF, since they appear limitations for the identifica- tion of sulphur and light elements in air atmosphere.
Blue pigments The FTIR analysis of the blue sample from the Church Aghios Philippos (Fig. 5: CH10_S2) presented a spectrum of low degree of resolution for blue chromo- phores. However, this is something already emerged in FTIR analysis of blue pigments [14]. The evaluation of the spectrum revealed the presence of four peaks at 924, ,030, 1,085 and 1,153 cm !, which are indicative for the presence of lapis lazuli [15]. Moreover, the presence of a weak peak at 540 cm ', which increases its intensity in the first derivative plot, is also characteristic for the stretching vibration of the S-S bond and therefore the presence of ultramarine [14, 16]. The ability of FTIR to identify sulphate compounds is of great importance for wall paintings surveys and highlights the complimentary character of IR with other portable spectroscopic techniques, such as LIBS and EDXRF, since they appear limitations for the identifica- tion of sulphur and light elements in air atmosphere.
Fig. 5 Representative infrared spectra of different inorganic pigment samples from the wall paintings of Mani
Fig. 5 Representative infrared spectra of different inorganic pigment samples from the wall paintings of Mani
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EngineeringAnalytical and Bioanalytical ChemistryCarbon BlackInfrared SpectrometrySelective Sampling
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