Antiquities Get an Ally in Battle against Time

Article excerpt

Its enigmatic face has been scarred by the hands of time and men, the sharp features of its former beauty seem to fade with each passing year. Yet this is not just any aging sculpture, but perhaps one of the world's most famous: The sphinx is gradually deteriorating. And like many of the world's ancient monuments, it sits in a nation so burdened by its own poverty that there isn't enough to go around for the populace, let alone for historical icons.

Though pollution, neglect, and looting have taken their toll on the sphinx and the nearby Giza pyramids, in many cases the legacies of the ancient world are dying a slow death by natural causes. In other parts of Egypt, the monuments emit salt and can "sweat" themselves into oblivion. In nearby Jordan, many of the magnificent reliefs from the Nabatean city of Petra are fading away from wind erosion, and some may be imperceptible in 100 years.

Now late-20th-century AD technology has offered a new technique that can help slow the disintegration of what the 20th-century BC left behind. By impregnating or injecting sandstone with silicon solutions, the natural stone is strengthened and chemically protected from further decomposition. Despite such graphic descriptions, conjuring images of giant needles, application is commonly done by spraying monuments with the solution, or, for smaller statues, by dipping them. In the process, pioneered by the Wacker-Chemie company in Munich, Germany, the solution forms an invisible protection against moisture and other elements. In slightly more technical terms, the silicon forms an inorganic, highly weather-resistant cement. Based on a formula of silicic acid ethyl ester, its substance reacts with atmospheric humidity to form silicic acid gel, or natural silica. "This is able to restore cohesive strength to some deteriorated sandstones, when applied in sufficient quantities, and in appropriate conditions," says John Stewart, a conservationist with the British Museum in London who has overseen several preservation projects in Egypt. A boon for Egyptologists For specialists, the silicon process is helping preserve ancient Egyptian facades and engravings that were becoming illegible and imperceptible. Peter Dorman, an Egyptologist with the University of Chicago's Oriental Institute, says the silicon process is now being piloted at Luxor Temple, a structure first finished under the period of King Tutankhamen. "The problem is that the temples are in contact with groundwater. There is visible salt damage," he says. "Salt that occurs in natural stone meets groundwater and destroys the exterior relief and breaks down the material. This {silicon process} tries to arrest the spread of the salts." With that accomplished, his team can move on with their main task of documentation through photography and precise drawings. …