A new analysis of Lord Elgin’s original casts of the Parthenon marbles, recently published in Antiquity, has revealed details effaced by Victorian vandals - and air pollution - following the classical sculptures’ removal from Greece in the early 19th century.

Dr Emma Payne, a specialist in classics and archaeological conservation based at King’s College London, conducted 3D scans of the plaster casts made by Elgin's workman of parts of the West frieze, which was removed from the monument in 1993 and is now in the Acropolis Museum in Athens.

Payne hoped to answer two key questions: First, how accurate were the 19th-century casts, and second, do the casts “preserve sculptural features that have since been worn away from the originals — do they now represent a form of time capsule, faithfully reflecting the condition of the sculptures in the early 19th century?”

"Elgin’s casts could be important records of the state of the sculptures in the very early 19th century before modern pollution would hasten their deterioration."

Payne compared Elgin's casts to a second set of casts commissioned by the British Museum in 1872, and created under the supervision of Charles Merlin, British consul to Athens. She found that the casts of the West frieze of the Parthenon revealed features that are now lost, including the faces of some of the sculptures, and chisel marks showing they had intentionally been chipped away by Victorian-era vandals. Indeed, Payne's analysis showed that more damage was caused in the intervening seven decades than in the 120 years that followed, meaning that a century of traffic pollution did less harm than Elgin and his compatriots.

"The marble of the Parthenon sculptures displays an orange-brown patina, approximately 100–150 μm thick. The origins of this patina—whether ancient or modern, natural or manmade—have been disputed. It is, however, stable and uniform, preserving the original surface details. This patina is distinct from the thicker, disfiguring pollution crust (from 200 μm to several mm thick) that once covered the sculptures, but has now mostly been removed from the West Frieze by laser cleaning... Such crusts are caused by suspension of atmospheric pollutants in a gypsum matrix, created by the reaction of the marble with sulphur dioxide. The crust, where present, retains the surface details of the original to a certain extent, but is discoloured and highly friable.

"It is noteworthy that the decay of the sculptures appears to have slowed during the twentieth century — precisely when problems with sulphurous emissions and acid rain were at their most acute. In turn, this leads to the conclusion that the apparently greater rate of deterioration during the nineteenth century can be largely attributed to deliberate defacement... rather than the cumulative effects of long-term environmental conditions. The relative lack of change in detail preserved between the Merlin casts and originals suggests that these attacks subsided following Greek independence in the 1830s and with subsequent restoration efforts."

The sculptures held in London, on the other hand, have suffered not only from 19th-century pollution, which persisted until the mid-20th century, they have also undergone irreparable damage caused by 'cleaning methods' employed by British Museum staff in 1838, 1858 and 1937–38.

The last cleaning process commissioned by Lord Duveen, for example, scraped away much of the detailed tone of many carvings and in some places the surface removed may have been as much as one-tenth of an inch (2.5 mm).