Abstract. Raman spectroscopy has been applied to check if there are detectible
material differences beneath the inscribed and non-inscribed areas of
marble-based written artefacts, which could be further used to visualize lost
or hardly readable text via suitable mapping. As a case study, marble
segments with ∼ 2000-year-old inscribed letters from Asia
Minor (western Turkey) and marble gravestones with 66 ± 14-year-old
inscriptions from the cemetery of Ohlsdorf (Hamburg, Germany) have been
subjected to Raman spectroscopy, as well as to complementary X-ray
diffraction, wavelength-dispersive electron probe microanalysis, and
Fourier-transform infrared spectroscopy, to thoroughly study the effect of
different environmental conditions, grain size, and inscription age on the
nature and penetration depth of marble alteration. The results demonstrate
that environmental conditions rule over the type of dominant weathering
changes, which are carotenoid molecular inclusions produced by lichen and
amorphous carbon for marbles from Hamburg and Asia Minor, respectively. The
alteration is much stronger in medium- and coarse-grained than in
fine-grained marble, but it is suppressed by letter colouring. In the
absence of letter colouring, the weathering-related products in both ancient
and modern engraved marbles are more abundant beneath than away from the
engraved areas, and the penetration depth is larger due to the enhancement of
fissures and micro-cracks around the inscribed areas. We show that the Raman
intensity ratio between the strongest peak of the weathering-related product
(ν(C=C) ∼ 1520 cm−1 for carotenoids or the G peak
∼ 1595 cm−1 for soot-like carbon) and the strongest peak
of marble (CO3 stretching near 1087 cm−1) can serve as a
quantitative marker to indirectly map the lateral distribution of cracks
induced during the inscribing process and hence can potentially be used to
trace lost text on vanished marble inscriptions. This approach can be
applied to other rock types, but further studies are required to identify
the corresponding autochthonous weathering-related products.
Effect of Ionic Liquids on the Physical Properties of the Newly Synthesized Conducting Polymer
