CHENNAI: Ambling along sun-soaked sand amid memories of youth crashing in like waves off the Mahabalipuram coast, P Rajendran, moving past 60, takes a stroll down memory lane, recalling his childhood days when the trove of sculptures and carvings on the walls of the Shore Temple were still well defined and marked by vivid contours. “This temple at the edge of the sea is our heritage. We should preserve it from further decay at any cost,” he says.
As the sun peaks mid-day, peeking over the horizon at the complex of shrines laden with history from the reign of Pallava king Narasimhavarman II, a sense of dread takes over Rajendran. Two months into retirement from the post of the principal of the government college of architecture and sculpture, Mahabalipuram, Rajendran frequents the temple overlooking the Bay of Bengal, caressing the sculptures made of native granite stones.
“The corrosion of the granite has been severe over the past 40 years or so,” says Rajendran, greeting one of the caretakers with a wave of hand. He points to the carving of an ancient man surmounted by a sculptured lion, which, over time, succumbed to disfigurement caused by the phenomenon of alveolarisation or honeycomb weathering. “We should preserve it from further decay at any cost,” he repeats.
Prevailing winds from the coast hovered over, scouring the edifices and gusting up to even 40 k/ph. Something it hoisted from the coast evoked dread.
Something was amiss… something abysmal…
… falling through the cracks.
Calling forth immediate attention.
Damaged heritage
According to a recent study in the Heritage journal by MDPI, sculptures on the side of the seventh-century granite monument, exposed directly to the sea, have been “obliterated beyond recognition.”
The deterioration of the architectural heritage has been accelerated by the four-fold interplay of salt weathering, marine aerosol, alveolarisation, and sandblasting occurring over time, indicates the study that was conducted between 1990 and 1997 by manager Rajdeo Singh, the then deputy superintending chemist of the Archeological Survey of India (ASI). Some of the damage endured are irrevocable.
“Salt spray picked up by winds from the coast moves in the direction of the temple, depositing salt into cracks in the granite stone,” says Singh, who retired from the ASI as the superintending archeological chemist in 2015. “The accumulated salt gradually evaporates and crystallises, disintegrating the sculpture and weakening the structure,” he adds.
Over seven years, Singh conducted extensive research to determine the deterioration mechanism induced by salt weathering on the Shore Temple. Deteriorated and pristine stone samples were analysed using X-ray fluorescence spectroscopy (XRF), atomic absorption spectrometer, conductivity meter, SEM-EDX, DTA-TGA, petrological analysis, and FTIR for the study.
“Salt weathering is a phenomenon commonly observed in coastal environments, causing deterioration to historical architecture, archeological structures, and objects,” explains Singh, now 69, whose study revealed patterns of “colour alteration, loss of cohesion, disaggregation, and detachment of the surface layer” of the Shore Temple.
A ‘sea’ change
Meanwhile, high tides in the Bay of Bengal, slowly, fiercely, gulped up the shoreline along the northern portion of the temple. As per a study in 2013, the Mahabalipuram coast had undergone erosion of up to 177 metres in the past 41 years from the year of the study. Rise in sea level, strong wave action, and high winds were observed due to the changing shoreline.
Since the Shore Temple was constructed in granitic stones of different compositions and textures, the rate of deterioration varied depending on the stone layers. Alveolarisation was observed on the three sides of the walls of the main gopuram.
The hot, humid, and salty conditions at Mahabalipuram are conservation perils to the temple, the study in MDPI finds.
To reduce the velocity of the wind blowing from the sea, casuarina trees were raised from the eastern corridor to the north to slacken high winds. Nature crossed swords with nature. “The tree cover protects the monument from the phenomenon of sandblasting,” says Singh. However, he cautions that the sculptures are still exposed to the adverse effects of salt weathering since salt particles, under their microscopic composition, “could easily make their way towards the temple complex.”
The ASI has been applying paper-pulp coating on the monument to remove accumulated salt. Cellulose-based poultices were found to have been able to remove about 70% of salts in the humid environment of Mahabalipuram. “Complete removal is rather difficult despite repeated applications.”
“All these years the temple was sheltered from the elements under the protection of plaster coating,” says Singh, whose study traced the presence of non-hydraulic air lime plaster on the interior walls of the temple. “The only viable solution is to replaster the monument using non-hydraulic lime,” he stresses.
The solution
If the assumption holds good, lime plaster, dating back to the late 7th century, peeled off over time due to direct exposure to the sun and geomorphic processes. The traces, presumed to be from the Pallava era, were of 2-3 mm thickness. “The method of protecting monuments and structures with lime plaster has been in vogue for centuries,” says conservation architect Benny Kuriakose.
Granite is among the four types of stone that withstand salt stains. Nevertheless, particles of salt wafted into cracks formed over the years. “The Pallavas may have chosen granite foreseeing the possible impact of geomorphic processes.”
As per a study published in Nature Climate Change in 2019, the phenomenon of global terrestrial stilling was observed over the last three decades, particularly in the 1980s, whereby global wind speed reduced exponentially. However, the study suggests that a reversal in the global slowdown of winds was encountered since 2010, indicating that the global average wind speed increased nearly six percent — from 7.0 to 7.4 mph — between 2010 and 2019 (less than a decade).
It might be good news for renewable energy production, but as far as the heritage buffs are concerned, the global increase in wind speed may have contributed to the accelerated disintegration of the sculptures and structures over the past decade. Salt-bearing wind buffets the seaside temple from all sides. The direction of the wind is mainly south-to-west during the rainy season, while it strikes from the north in summer. “This has implications in the material decay process,” observes Singh.
According to an official of the ASI, Chennai circle, who sought anonymity, replastering the monument would tamper with the original design conceived by the Pallavas. “Chemical treatment is used in the restoration process. ASI is taking all the measures possible to protect the monument from the vagaries of nature,” says the official.
Protecting the monument is an onerous task particularly due to its proximity to the sea. Every two years, paper-pulp coating is applied on the surface of the monument. “It was last done in January,” adds the official. “We may not be in a position to undo the damage done,” regrets Rajendran. “We try to dominate nature, something that is beyond our control, resulting in detrimental effects,” he winds up, taking the long road that turns to the main street.