Mysterious film preserves Raigad Fort for years: ASI

PUNE: ASI scientists have in their latest discovery revealed the long-hidden secret behind the preservation of Maharashtra's iconic Raigad Fort - a mysterious patina.

Patina is a thin layer or film that usually forms on the surface of such stone structures due to age, and growth of micro vegetation on them. Scientists are of the view that the patina has helped the historical structure stand tall for centuries.

Senior Archaeological Survey of India (ASI) scientist Rajendra Yadav told TOI, "For years, the origin of the oxalate films covering stone surfaces across the Mediterranean basin, and beyond, has been a subject of debate. But our latest analysis reveals how the calcium oxalate patina on Raigad Fort's basalt stone walls has been silently protecting the monument for centuries. It's like the fort has its own secret protector, hidden in plain sight."

Formed through the work of micro-organisms, he said, the patina has been shielding the underlying stone from the harsh tests of time, humidity and weather. The findings of the analysis were recently published in the MDPI International Journal of Heritage. Former ASI scientist Manager Singh, who was also part of the analysis, said, "The calcium oxalate patina acts as a natural shield, safeguarding the underlying surfaces of the basalt stone from the ravages of atmospheric degradation, including pollution. The e researchers added that mechanical cleaning or chemical treatments that monuments are subjected to these days should be rethought, especially if they involve removal of this coating.

Senior ASI scientist Rajendra Yadav said removal of the patina could expose the underlying stone to new environmental challenges, leading to rapid deterioration.


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