Conservation award for Acropolis laser rejuvenation

04 Oct 2012

Custom system developed by scientists at IESL-FORTH in Crete picks up 2012 Keck Award.

The International Institute for Conservation of Historic and Artistic Works (IIC) has chosen a laser restoration project at the Acropolis in Athens, Greece, as the winner of its 2012 Keck Award.

The biennial award, established in 1994 and named after the conservationists Sheldon and Caroline Keck, was handed to a team from the Acropolis Museum and the Crete-based Institute for Electronic Structure and Lasers (IESL) at a ceremony in Vienna, Austria, last month.

IESL scientists developed a dual-wavelength Nd:YAG laser technology that has been used to clean a range of historic sculptures and monuments, starting with the West Frieze of the Parthenon nearly a decade ago.

Since last year, the same technology has been on view at the Acropolis Museum, in a “public laser laboratory”, and used to clean and restore the Caryatids – sculpted female figures that double up as architectural supports in place of traditional columns.

The IIC gave its award to the Greek team for its contribution towards promoting the “public understanding and appreciation of the conservation profession”, and it is estimated that no fewer than two million people have so far had the chance to watch the laser rejuvenation process as it removes grime caused by the accumulation of pollutants on the surface of the figures that has built up over centuries – something that usually only takes place inside a laboratory with restricted access.

By using both the fundamental YAG wavelength and the frequency-tripled 355 nm harmonic, the restorers are able to remove the grime without affecting the color of the patina – something that had been a problem, causing a yellowing effect, in the past when only the 1064 nm output was used.

IESL scientists led by Costas Fotakis then discovered that during conventional laser removal, selective vaporization of the dark encrustations on the marble surface altered the absorption spectrum of the remaining encrustations, causing the yellow discoloration.

For the Caryatids project, museum officials wished to avoid transporting the ancient sculptures, preferring that the restoration took place in situ. As a result, the IESL team built a special platform to support the pieces and surrounded them with protective laser curtains for health and safety requirements.

Fotakis, along with Paraskevi “Vivi” Pouli and Kristalia Melessanaki, also came up with a prototype system that has been used to clean and restore the Caryatids’ porch in the Erechtheion.