Moreover the presence of sulphur dioxide in the atmosphere led to the formation of a gypsum layer on the marble surface, which up to a certain thickness preserves details of the relief and therefore must be safeguarded [35].
A cross section of a discolored area from Sant'Eligio shows very thin residues of patina on the marble surface and a strong fluorescence inside the stone between marble crystals (Figure 4a and b).
The wet poultice is applied on the marble surface in a layer being 1 1.5 cm in thickness, covered with polyethylene food wrap, and left for 24 h.
The images show the thin residues of the patina on the marble surface - visible illumination (a), and a strong fluorescence inside the stone between calcite crystals - UV illumination (b). Figure 5 San Giacomo Maggiore by Niccolò di Pietro Lamberti ca. 1414.
But after a police officer rammed one protester with his bike, another officer slipped on the marble surface of the square and fell with his bike next to him.
On the contrary, CaLoSiL® treatment is still clearly visible on Carrara Marble surface after exposure and it appears as a discontinuous brownish surface layer in plane polarized light, and as a bright greenish microcrystalline layer in cross polarized light (Figure 6c, d).
Cardboard witches and crêpe-paper bats hung from the ceiling, and candlelit jack-o'-lanterns had been set out on the marble surface of the bar.
Red arrows indicate the surface microcrystalline layer still present on the marble surface.
The SEM analysis of the treated sample revealed a homogeneous crack-free coating on marble, while FT-IR proved that condensation and copolymerization reactions took place on the marble surface.
To compare the position accuracy between line and plane positions, the line poison test was also carried out on the marble surface.
