The marbles of the Acropolis, the symbol of the city of Athens, apart from other causes of deterioration have heavily suffered recently from the onset of atmospheric pollution hanging over the Greek capital. The text that follows is based on the report of the Professor of the National Technical University Th. Skoulikidis made during the International Conference on Environmental Pollution, held in Thessaloniki between 21 and 25 September 1981. Emphasis has been given by the editor to the part concerning the effects of atmospheric pollution on limestone and especially on marble. There are six main kinds of limestone and marble deterioration caused by atmospheric pollution and its attack: 1. Water freezing and expanding in the fissures thus causing the stone to cracking. 2. Erosion caused by suspended particles. 3. Biodeterioration. 4. Marble cracking produced by the corrosion of steel clamps and junctions introduced either during construction or, mainly, restoration. 5. Attack by acids contained in the atmosphere that, combined with rain-water, result in dissolution of the stone. 6. Attack by SO2 that, in absence of rain water, creates a gypsum formation (sulfation) on the stone surface.
The study of the latest case, that of sulfation, proved that the sulfated film on the marble surface contained 80-97% gypsum, while the thickness of gypsum film measured by a new method, the “pin probe method” – that of Prof. Skoulikidis’ group- was found 1-15 mm. The comparison of ancient statues in their present situation to old photographs or modules made ten to sixty years ago, led to the conclusion that the severe deterioration started twenty to twenty-five years ago, a period that coincides with the intense industrialization of the area of Athens and, consequently, with the increase of pollution. Moreover, it was observed for the first time that the sculpture details have been preserved, as if printed, on the thin gypsum film.