Cleaning the temples has an unintended side-effect

Twenty years ago, they began to clean the unsightly lichens from the walls of Angkor Wat. What was thought at the time to be a significant esthetic improvement has brought with it unexpected problems, as this report explains:

The palatial 12th-century Hindu temple, shrouded in the jungles of Cambodia, has played host to a thriving community of cyanobacteria ever since unsightly lichens were cleaned off its walls nearly 20 years ago. The microbes have not been good guests.

These bacteria (Gloeocapsa) not only stain the stone black, but they also increase the water absorbed by the shale in morning monsoon rains and the heat absorbed when the sun comes out. The result, says Thomas Warscheid, a geomicrobiologist based in Germany, is a daily expansion and contraction cycle that cracks the temple’s facade and its internal structure. Warscheid, who has studied the deterioration of Angkor Wat for more than a decade, said in an interview that these pendulum swings have broken away parts of celestial dancer sculptures on the temple walls.

It is getting worse – up to 60 or 70 percent of the temple is black,” he added. Once chalked up to weathering, the damage at Angkor Wat is now seen as the result of a much more complex dynamic: the interaction of microorganisms with the chemical and physical properties of the temple.

In various places around the world, from Easter Island to the Acropolis, microscopic organisms are accelerating the deterioration of monuments and historic landmarks. Scientists and conservators have only recently begun to understand the role that common bacteria and fungi play in destroying cultural sites and how they can be stopped – if at all.

~ by Leonard on July 22, 2008.

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