ΠΡΑΚΤΙΚΑ 4ου ΠΑΝΕΛΛΗΝΙΟΥ ΣΥΝΕΔΡΙΟΥ ΨΗΦΙΟΠΟΙΗΣΗΣ ΠΟΛΙΤΙΣΤΙΚΗΣ ΚΛΗΡΟΝΟΜΙΑΣ –EUROMED 2021

4 ο Πανελλήνιο Συνέδριο Ψηφιοποίησης Πολιτιστικής Κληρονομιάς
EUROMED 2021, 30/9 - 3/10/2021
3.2 Methods
For this research, in situ measurements were carried out on the frescoes of Spring, Autumn and Summer, which
are located in the current building N. Gyzis in Palataki Tower, Chaidari, Athens, which was named in honor
of the great painter who lived there for a while and created one of his earlier works in the second half of 19 th
c. (Christopoulou et al, 2021).
The three wall paintings of Spring, Summer and Autumn that have been studied in this work are shown in
figure 1 and 2. From the now damaged winter mural, only measurements are made on the clean plaster in order
to understand the substrate of the wall painting. The analytical techniques used were XRF and Raman
spectroscopies, both portable and non-destructive (Liritzis et al 2020).
For the qualitative determination of chemical elements of the examined color hues, a portable handheld Xray
fluorescence spectrometer was used. Specifically, a Thermo Scientific Niton Xlp XRF Analyzer with a high
performing and solid-state detector was used. The experimental results were extracted based on the correlation
of the two non-destructive, complementary techniques of p XRF and p Raman spectroscopies. Their results
were compared with reference spectrum of pigments of the same period of 19 th c. (Doulgeridis, 2008). For the
data acquisition from it, a built-in software was used and measurements were saved as Unicode ASCII file
format, which is compatible for further analysis with specialized software.
As for the Raman analysis, measurements were performed with the Rock Hound DeltaNu Raman
Spectrometer, which has a near-infrared 785nm laser source, adjusted to 8cm -1 resolution and spectrum range
of 200cm-1 to 2000cm-1. Before measurements, calibration tests were conducted in ideal pigment samples
made for this purpose (Caggiani et al, 2016), to ensure the correct Raman shift measurement and operation.
For further analysis, process and evaluation of measurements for both XRF and Raman techniques the
scientific software SpectraGryph was used (F. Menges, SpectraGryph-Optical Spectroscopy Software, Version
1.2.14, 2020).
All measured Raman spectra, before the main process of pigment identification were subjected to a
preprocessing procedure such as baseline correction, Savitzky-Golay, smoothing and normalization (Ferraro
et al, 2003).
4. RESULTS AND DISCUSSION
The colors selected for analysis from the wall painting of ‘’Four Seasons’’ are the following: Red, White, Blue,
Green, Brown, Brownish red, Brownish yellow and Brownish Orange. From the damaged Winter wall
painting, measurements were made only on clean support layer. Due to the technique used by the artist (fresco)
there is difficulty in the documentation with spectroscopic techniques as the presence of peaks from the
substrate is strong. This is because the pigment granules are trapped during the formation of calcium carbonate
(Malentzidou, 2014).
In figure 2 the sampling points for each color hue are presented with yellow dots. In table 1 the summarized
results of XRF analysis and pigments identified by Raman spectroscopy are also shown (Larsen et al, 2016).
The analysis of three wall paintings with portable XRF reveal elements such as Zinc (Zn) for white, Lead (Pb)
and Iron (Fe) for brown, brownish yellow, brownish red and brownish orange hues, Mercury (Hg) for red and
(Fe)for blue and green. The analysis on support layer in the Winter wall painting reveal the elements of Zinc
(Zn) and Calcium (Ca).
Figures 3 to 7 show representative Raman spectra for different color hue along with reference spectrum (Bell,
Clark and Gibbs 1997; Caggiani, Cosentino and Mangone 2016). Figures 8-10 show representative XRF
spectra for different color hue.
194