Archaeological Survey of India (ASI) has been instrumental for this sacred cause. Different branches of ASI having technical expertise in different disciplines, work together in perfect coordination to accomplish this stupendous task. Science Branch of Archaeological of Survey of India is one of the oldest branches of ASI and was established in 1917 with an objective to share the responsibility of preserving monuments of the country in a scientific manner utilizing the best available traditional and modern methods of conservation. The main objective of providing scientific treatment to monument is to improve the aesthetic appeal of the monument, Remove all deleterious accretions and deposits, Neutralize harmful residues and prepare the surface for final preservative treatments.
There are different natural and manmade factors which are generally considered responsible for different conservation problems and cause damage to the building materials of a monument. Geological and mineralogical defects which develop during the genesis of rocks may be responsible for different conservation problems and consequent damage to the monuments. This is due to inherent weakness of the building materials.
There are certain biological factors such as Growth of Moss, Lichen, Algae, Fungi and higher plants on a monument. They not only impart a ugly look to the monument but also cause physical and chemical damaged to the building material. Bat’s and bird’s droppings/excreta cause damage particularly to fine stone works and paintings. Deposit of Bat’s excreta on stone structures in Ajanta Caves caused chemical damages to the structures.
Suspended Particulate Matter (SPM) and other chemically active pollutant species along with dust results in disfiguring of the monument. Similarly variation in climatic conditions, moisture and intense solar radiation are also responsible for the decay of specific building materials.
Conservation problems are different for different geographical areas. For example the monuments at high altitude like monasteries of Leh and Ladakh face a different type of conservation problems which are generally related to specific clay based (adobe) structures and variable climatic conditions. Similarly the monuments of coastal areas face the problem of salt efflorescence. Crystallization of soluble salts in the matrix of stone, plaster, mortar etc. is a major cause of damage to the monument. This disrupts the pore structures of the stone and slowly damages the core of the building material which is difficult to be repaired. Burning of oil lamps and ingredients used for offering puja in the temples also causes damage to the monuments.
Further acts of human vandalism also invite many conservation problems. Ancient Monuments and Archaeological Sites and Remains Act – 2010 provides for the preservation of ancient and historical monuments, archeological sites, and remains of national importance and also provides penalty against acts of human vandalism.
Science Branch of Archaeological Survey of India study the physical and chemical characteristics of building materials or the substrate (stone, rock mortar, plaster etc.). After proper diagnosis of conservation problems, an appropriate methodology is developed by experienced archaeological chemists using suitable chemicals, solvents and materials.
In order to conserve and preserve the monuments different conservation measures are planned and executed in a systematic manner to achieve best possible results. General cleaning of monuments, mud pack cleaning, removal of calcareous deposits and accretions, bio-cide treatment, consolidation and water repellent treatment, are some of them. Very dilute mixture of ammonia solution and a non ionic detergent is used for the easy removal of accretions and biological growth with mild brushing. Bleaching powder slurry in aqueous medium is used to remove micro-vegetation from lime plastered surface. Mud Pack Cleaning is used for the cleaning of plain and decorated marble surface in order to remove such accretions which generally do not respond to normal cleaning process. The pack is prepared using Bentonite clay to which some chemicals in a fixed ratio are added to improve the working of the pack which is based on the principle of adsorption. This method is being used successfully for the conservation of Taj Mahal and other marble structures.
Besides calcareous deposits, the deposits of carbon black/soot, stains of oil, red ocher, paints etc. also need cleaning for which suitable formulations are prepared and used as per requirements. Biocide treatment helps to retard or check the recurrence of micro-vegetation growth on the monuments. After cleaning 2-3% aqueous solution/suspension of Sodium Penta Chloro Phenate is being used for this purpose. The efficacy of this treatment is further improved with water repellent treatment which is given to the monument just after this treatment on the dried surface. The Science branch laboratory of Archaeological of Survey of India at Dehradun works in collaboration with specialized scientific institutions so that appropriate bio-cide may be evaluated and selected for specific problems related to bio-deterioration of monuments.
The Taj Mahal, Kutab Minar, Caves of Ajanta, Meenakshi Temple, Rock shelters at Bhimbhetika, temples of Khajraho, Badal gate at Chanderi, Great Stupa of Sanchi, Jahaz mahal of Mandu, and many other heritage buildings reflects our impressive composite culture. Besides providing scientific treatment to the monuments of historical and social importance, there is a need to imbibe good conservation practices for protection of our heritage.