Heritages are very valuable for every country as it presents the eminence culture of the country. It reflects the history and uniqueness of the place and monument respectively. The monuments present at these sites are made up of various types of materials mainly constitute of plaster, paper, wood, stone, painting materials etc. Now-a-days these monuments are being degraded at high rate. Factors influencing this degradation process are temperature, humidity, micro-organism, insects etc.
Among all the monuments, Ajanta cave are rock cut Buddhist cave monument representing the highest point of artistic and technical achievement during the Golden Age.
These caves are related with Buddhist religion and were made during the vakatakas period. Moreover these caves are world well known for the wall painting works of art of both the Hinayana and Mahayana beliefs of Buddhism. The complex of cloisters at Ajanta, worked in second century B.C. also, fifth century A.D., shows up excessively one of a kind to us today on the grounds that no other antiquated Indian site has been well preserved in its paintings.
Before 1819, the caves were negligible heritage of our country; it was in 1819 when the cave has been discovered by John Smith (Officer of British battalion) (Garima Bharti, 2013). It was in 195, the Ajanta caves were declared as the monuments of national importance by the Government of India and in 1953 the Archaeological Survey of India taken the charge for the preservation of these paintings. A lot of work has been carried out for determining the deterioration causes and preservation techniques for the Ajanta cave.
Present study reports the factors responsible for deterioration of the Ajanta cave mainly focuses on insects.
Ajanta cave is located at 20°33’12’N & 75°42’01’E, which is about 6 kilometers from Fardapur & 107Km from city of Aurangabad, the western part of the Maharashtra state of India. It is one of the great volcanic formations of the basalt plateau of Deccan trap and also among the largest historical sites in the UNSECO list. The cave contains 30 caves of decorated mural paintings representing the past lives and rebirths of the Buddha, pictorial tales and rock-cut sculptures of Buddhist deities. Out of these 30 caves, 25caves were monasteries (Viharas) while the rest were temples (Chaityas). According to older accounts, the caves are built in two phases, 1st phase around 2nd century BCE while the 2nd phase around 400-650 CE. In this area mainly three seasons are there: the rainy season, the dry season and the hot season. According to Tomoko Uno and Yoshiko Shimazdu (2012) from July to September the monthly rainfall is over 150mm/month (Fig1). The highest temperature is in April with a monthly average temperature of 32 ºC and a daily maximum temperature of over 40 ºC while the lowest temperature is in January with a monthly average temperature of 23 ºC and a daily minimum temperature of 13 ºC (Fig2). In the rainy season the daily average humidity is 80% and 40% in the dry season.
According to the mineral structure of the stone, it was found that in some of the caves, a blue-green powder has formed. Some crystals have been completely converted into powder which has caused the formation of holes. These holes serve as a surface liable for deposition of dust, dirt and hiding places for insects (O.P. Agrawal, 1988).Tomoko Uno and Yoshiko Shimazdu (2012) show special influence on the temperature and humidity of the cave as one of the major cause for the degradation of the paintings. Deterioration of the mural paintings gets accelerated as the humidity changes because bat excreta were present on the ceiling, side walls and also over the paintings which has high moisture absorbency as it undergoes repeated contraction and expansion whenever the humidity changes. This results in the detaching of the paintings. The dry and wet cycle of humidity causes the expansion and contraction of the plaster that ultimately results in the detachment of the plaster from the back walls. Whereas in low humidity conditions, the paintings gets detached from the walls as the paint binder becomes friable. Out of many reason of decay of wall paintings at Ajanta, the dampness plays one of the fundamental reasons of weakening for the painting. The compositions endure better when the stickiness inside the caves is 55-60% and temperature around 25°C. The temperature in the caves stays static around 27-30 °C, yet wide fluctuation in humidity from around 80 % in the stormy season to 40 % in the late spring season have been recorded. This causes flaking of colors, formation of cracks, edges, holes and so forth on the painted mortar. It is seen that in the past muddy water has entered into the caves after the spot was surrendered by Buddhist priests. Façade/Stone blocks presumably fell before the caves and the rain water, which should stream into the ravine of Waghura River, has constantly gone into the caves conveying with it mud and soil. This has made methodical harm practically all the stone cut pillars of the caves.
Most insects do not have specialized detectors for airborne sound, natural airborne sound including ultrasound. They can hear the insect generated sound (Thomas J. Walker, 1996) like male crickets produce an acoustic signal with carrier frequency between 3 and 6 KHz that attracts conspecific females (Moiseff et.al. 1978). So if sound is present, lying in the wavelength of insect generated sound then it will attract insects which get habituated in that place and results in the degradation of caves.
Insect’s especially nocturnal insects can see and gets attracted towards the light sources which emit UV radiation. Presence of different wavelength of UV light can attract variety of insects that can results in the deterioration of the cave for e.g. Plodia interpunctella get attracted towards violet spectrum of light and UV light.
Earlier when the paintings were being studied, coatings of varnish were applied by some scholars, without removing the dirt and soot. This was done for the brightening of the painting, bringing out the details and fixing the flaking paint. But as the time passes the situation becomes worsen. The original color has changed considerably, white appear as yellow, blue as green and so on.
It was noticed that in some caves at Ajanta, there is a layer of white and sometimes brown or black layers over the paintings (Agrawal, 1975; Lal, 1966, 1976). According to Manager Singh & Balasaheb Arbad (2013), out of all the insects, most of the damage to the paintings was caused by silver fish. Silver fishes live to an expansive degree on carbohydrates and are said to most likely condensation certain types of cellulose. They too flourish with little measures of proteins and gum or paste utilized as authoritative in wall paintings. It was eminent that the basal layer of the Ajanta murals and ceiling paintings is composed of mud plaster with some organic matter added such as paddy husks, vegetable fibers, grass and other organic fibrous material which is overlayed with lime, kaolin or gypsum (Agrawal, 1988). The microorganisms attack on these binding materials as it provides nutrition which ultimately leads to the deterioration of the paintings. Hueck-Van der Plas(1968), O.P. Agarwal (1988), said that the fungal development on the plaster would be due to the fact that fungi can live on very small quantities of organic substances contaminating the surface of the substratum. It was also observed that in almost all the caves bat guano was the main source of organic matter which was present on the ceiling, side walls and also over the paintings which may provide more nutrition for the proliferation of microbes (Agrawal 1988). Insects such as silverfish (Lepisma saccharina) and beetles belonging to the family Tenebrionidae was also present in the cave (Agrawal, 1988). According to O.P. Agrawal these beetles are known to attack dried leaves, cowdung etc. Their presence at Ajanta may be explained by the fact that, while eating the organic matter of the murals, they become established in the back of the paintings and eat and thus loosen the plaster. Insects like cockroaches, larvae and pupae of Lepidopterans were also identified. Moreover the bat excreta are rich in organic nutrients which serve as a food source for the microorganism. The microorganisms are being eaten by some smaller insects which are further being eaten by larger insects. Moreover the base of the paintings i.e. vegetable husks, organic materials mixed with the plaster has proven to be a good breeding place for insects (Garima Bharti, 2013). Micro-organisms like fungi attack on these binding material of the painting which penetrate deeply into the substratum and can destroy the structure and even produce the fissuring of the paint layer, peeling, friability and collapse due to the effects of the enzymes they secrete (Agrawal, 1988). Even after the annihilation of the bats from the Ajanta Caves, the distortion and rot of the wall paintings keep on occurring particularly close to the regions where the pee has infiltrated profound into the mud mortar and stone surface. The aggregations of excretory stores have been heavy to the point that, under the damp conditions, a portion of its constituents have relocated over extensive zones of the painting. The dark patches which are wealthy in natural issue give a decent substratum to the smaller scale organic development accordingly exasperating the bio-weakening of the cavern canvases. The slow decomposition of urea, a vital constituent of bat’s pee, makes ideal conditions for creepy crawly action and natural issue operating at a profit stores and goes about as great supplement. Another way, some of the visitors impact the Ajanta murals is by eating eatable inside the cave. It is estimated that ¼ of Ajanta murals has been lost due to insect activity ever since the cave was abandoned by Buddhist-monks in 6th century A.D. Although Archaeological Survey of India keeps strict vigil, the visitor’s were found sometimes making use of cave for their eating. This process gives way to food chain inside the cave which may cause long term impact on the paintings
Indeed, even after the obliteration of the bats from the Ajanta Caves, the twisting and decay of the divider artworks continue happening especially near the locales where the pee has penetrated significant into the mud mortar and stone surface. The totals of excretory stores have been substantial to the point that, under the clammy conditions, a part of its constituents have migrated over broad zones of the artistic creation. The dull patches which are well off in normal issue give a tolerable substratum to the littler scale natural advancement in like manner angering the bio-debilitating of the cave canvases. The moderate deterioration of urea, an essential constituent of bat’s pee, makes perfect conditions for frightening little creature activity and common issue working at a benefit stores and goes about as extraordinary enhancement. Another way, a portion of the guests sway the Ajanta wall paintings is by eating palatable inside the cavern. It is assessed that ¼ of Ajanta paintings has been lost because of bug action as far back as the cavern was deserted by Buddhist-priests in sixth century A.D. Albeit Archeological Survey of India keeps strict vigil, the guest’s were discovered now and then making utilization of cavern for their eating. This procedure offers approach to evolved way of life inside the cavern which may cause long haul sway on the works of art
Many research works has been carried out for the conservation of Ajanta cave. The work till now attended are spraying of insecticides, consolidation of weak and loose plaster, chemical treatment for the removal of superficial accretions, removing old preservative coat followed by applications of new preservative coat, regular cleaning of the caves, use of biopesticides. Usually it is conceivable to dispose of silver fish by making warm and dry conditions, negative to them. Yet, such an activity is absurd in caves and much more so in painted caves. A test led by M.S. Mathur(1968) with 6% by weight D.D.T, splashed in petroleum distillate, controlled silver fishes for four months. Mathur additionally has done a try different thing with carbon disulphide vapors in caves, with accomplishment in the destruction of silver fish. The utilization of sodium fluoride or pyrethrum powder, or a blend of the two as residue was normally suggested for the control of silverfish. M. S. Mathur also succeeded in killing the insects with the use of gamma radiation but it was abandoned at that stage because it was impossible to remove the effects of radiation from the surface, as it was quite dangerous for the operators also. M. Singh (2014) reported that the following solutions were prepared for cleaning the painted surface.
Kaoline was one of the pigments noticed to use at some place in Ajanta painting. But after sometimes it was noticed that the white kaoline was broken and its fall grain by grain from the ceiling paintings of cave no.2 as shown in figure 3.
Chemical treatment and protection of painted present on the principle Buddha and two standing chaperons in the cell of focal corridor of Cave 6 were conveyed out. The evacuation of stains of honey bees wax inserted with ash, greenery and residue on the façade of Cave 9 was taken care of by utilizing specific natural solvents, for example, dissolvable naphtha, carbon tetrachloride and chloroform. The whole facade was then artificially cleaned and preserved. Removal of determined accumulations of gum coats from the works of art on the roof of south passageway in Cave 17 was taken care of by utilizing different natural solvents, for example, morpholine, butyl-lactate,n-butyl amine, cellosolve, etc. The expulsion of whiteness from the artworks in Cave 17 was proceeded. The work was done on the north divider utilizing a mix of different solvents in various extents according to prerequisite of the situation. The work of fileting and settling of lump segments of compositions on the roof in Cave 19 and themain Buddha sanctuary of Cave 6 was done.
Substance treatment and security of painted present on the standard Buddha and two standing escorts in the cell of central passage of Cave 6 were passed on out. The departure of stains of bumble bees wax embedded with fiery remains, greenery and buildup on the façade of Cave 9 was dealt with by using explicit normal solvents, for instance, dissolvable naphtha, carbon tetrachloride and chloroform. The entire exterior was then misleadingly cleaned and protected. Expulsion of decided collections of gum coats from the gems on the top of south way in Cave 17 was dealt with by using diverse regular solvents, for instance, morpholine, butyl-lactate,n-butyl amine, cellosolve, and so on. The ejection of whiteness from the works of art in Cave 17 was continued. The work was done on the north divider using a blend of various solvents in different degrees as indicated by essential of the circumstance. Crafted by fileting and settling of irregularity fragments of pieces on the rooftop in Cave 19 and themain Buddha asylum of Cave 6 was finished.
Figure 4 shows that the clearing activity was done for shallow expulsion of 75-80% of varnish layer leaving 20-25% edge for cleaning by other complex strategy in future.The fundamental motivation behind the treatment was to diminish the thickness of varnish layer to renderthe hidden surface to breath (Singh, M; Arbad, BR, 2012). Also Indian archaeologists have discovered that hemp which played a key role in preserving the ancient Ellora caves. A mixture of hemp, clay and lime plaster is responsible for preserving paintings and intricately carved scenes. This is because it regulates humidity and deters pesky insects, which have attacked the cave. The use of hemp helped the caves and most of the paintings remain intact. But the use of hemp was banned by the government due to its narcotic property. Moreover the chemicals used for the preservation are harmful for the insects as the insects are pollinators. Till now no work has been carried for the preservation of Ajanta cave with the use of sound and light as preserving techniques.Nocturnal insects get attracted toward the light sources which emit UV radiation (Masami Shimoda, Ken-ichiro Honda, 2013). So, Light can be used as an effective conservation technique for the conservation of caves against insects. Light can attract the insects and trapped them without killing them. The trapped insects can be used for the further biodiversity study of insect’s species found at that place. Moreover light does not causes any harm to the caves and the surrounding environment.