Investigation of an appropriate methodology for preservation of traditional Sri Lankan mural paintings

Abstract

This research was founded with an objective of finding the most effective method of preservation of traditional Sri Lankan mural paintings. Investigation was separated into three main areas. These are determination of necessary actions in preservation, investigation of preservation mechanisms and investigation of applicability of these methods. Actions needed in preservation were identified by analyzing present condition of paintings. Paintings were classified into several logical groups to facilitate analysis. A criterion for classification was developed considering all possible factors of sorting. Classification of paintings according to the period of production was the most appropriate criterion since this automatically classified paintings on technique, school, climate, pattern of decay, pattern of deterioration and the degree of deterioration. Analysis of condition of paintings disclosed following facts: 1. all paintings are in a rapid rate of decay 2. deterioration is a result of natural decay and accelerated decay due to dilapidation 3. intervention based on synthetic resins prevented fragmentation and loss of material but accelerated the rate of decay This information led to the decision that adequate repair -and prevention of deterioration would be the most needed actions in conserving Sri Lankan paintings. Analyzes of these facts emphasized that there was a definite need to develop a viable method of reduction of the rate of decay of paintings. Development of the most appropriate method needed following background information: principles of traditional technology; social aspects that led to creation, usage and maintenance of paintings and traditional methods of conservation and maintenance. There were few direct and indirect sources to gather this information. These were traditional technical texts, historic records, legend memory and information generated from physical and chemical analyses. Present social conditions that led to survival and destruction of paintings were also analyzed. Technical analyses were based on structure, composition and behavior of Sri Lankan paintings and survival and performance of different types of paintings in different climatic zones. Most appropriate chemical and physical analytical methods were used in the analysis. Constant nature of structure, composition, production process and procedure of painting in paintings belonging to a particular class and analogy among different classes indicated strict adherence of production techniques to rules and regulations of traditional technology. Seven major Sri Lankan painting techniques were identified. Classical, medieval and southern are the dominant techniques among them. The most major difference among these techniques is the structure and composition of ground. Two major techniques were therefore defined based on the usage of the process of carbonation in the ground. The characteristic feature of Sri Lankan painting techniques is the use of biotechnology. A heavy amount of microbiological actions and enzymatic reactions had been used to attain key properties not gained by other means. Use of most stable material is a law of traditional technology. Certain principles of traditional technology that realized appropriate coordination between paintings and environment were identified. A particular traditional painting technique fulfilled the needs of the corresponding painting school and users of paintings produced by that technique. Usage and maintenance also followed definite rules, regulations and guidelines. These were identified by analyzing later modifications to paintings. Special attention was given to understand actions occurring in paintings. These actions were identified as interactions of paintings with the environment. Interactions with environment and response of paintings to these interactions were defined as behavior. Water transmission and thermal movement of paintings were identified as main actions of behavior. These dynamic physical actions bear on most other physical, chemical and microbiological actions. Paintings on masonry and wood support absorb water through support, transmit towards the surface and evaporate on the surface. Paintings on rock support absorb water through the surface and disperse throughout the ground. Porosity of ground and permeability of paint layer are important parameters in both of these absorption types. Most actions occurring in paintings are detrimental to them and called actions of decay. Few favorable actions called actions of preservation were also identified. Various factors become favorable or detrimental in specific ranges and combinations with other factors. Decay is a continuous process associated with every painting. Decay results in a change of material, material properties and structure. These changes bring about deterioration, i.e. formation of defects. The rate of decay accelerates with the formation of defects. Behavior of every painting becomes destructive with the formation of defects. Prevention of decay is the principle action necessary in preserving paintings. This is the key task necessary to preserve deteriorated traditional mural paintings. Prevention of fragmentation and loss of material are other important needs. This investigation was centered on determination of the most effective method of minimizing the rate of decay. Simulated samples of paintings were used in the investigation. Production processes of these simulated samples were determined using information obtained from traditional technical texts and chemical and physical analyses of samples of paintings. It was found that two types of samples could represent all Sri Lankan paintings. These are samples with lime ground and samples with clay ground. 1twas decided to produce samples at four categories of increasing complexity to reduce errors during analysis. Elementary samples simulated the painting ground, basic samples simulated the multilayered structure of paintings and advanced samples simulated complex structure of paintings. Advanced samples had heterogeneous paint layers and complex ground. Representative samples represented the actual paintings. Enzymatic and microbiological actions mentioned in traditional technical texts were used to produce representative samples. This investigation needed methods to measure behavior and the rate of decay. Behavior could be adequately measured using parameters of main actions of behavior. An indirect method based on intensity of defects and difference in hue was used to measure relative rates of decay. Methods of reduction of rate of decay tested were removal of factors of decay, environmental control, repair of defects, induction of equilibrium behavior and few specific actions of preservation. These different methods were successful at various degrees. Removal of some factors of decay reduced the rate of decay at all instances. However, it had a limited amount of success due to the fact that total removal of some factors like water and thermal energy increased decay. Environmental control remarkably reduced the rate of decay. However, this did not guarantee the long-term existence of paintings. Furthermore it was difficult to adopt. Natural actions of preservation takes very long durations and difficult to manage. Maintaining conditions that enhancing these actions was the only external intervention possible. Further analysis of these methods of reduction of rate of decay disclosed the fact that all of these mechanisms were effective when they induce equilibrium. Special attention was therefore given to test possibility of reducing the rate of decay by inducing equilibrium behavior. Existence of a relationship between the degree of equilibrium and the rate of decay was the main hypothesis tested in this research. Relationship of equilibrium behavior and the rate of decay was studied at four levels using four categories of samples. A completely randomized design was used. Relationship between behavior and the rate of decay was tested with elementary, basic and advanced samples. Behavior was changed by altering input physical factors. A distinct relationship was observed. Relationship of degree of equilibrium with the rate of decay was also investigated with these samples. Equilibrium was quantitatively changed by allowing the samples to absorb moisture at different known rates under different known temperatures and relative humidity. A definite correlation existed. These relationships were significant (p<O.S)or highly significant (p<O.1) in each category of all types of samples. Definite relationship existed between the degree of equilibrium in behavior and rate of decay of traditional paintings was established with a high confidence level. It was found that the degree of deviation from the optimal equilibrium is the factor that determined the rate of decay. Further analysis done with representative samples disclosed the fact that each Painting technique has a set of optimal' ranges of -equilibrium. There is an optimal point of equilibrium for each action and optimal range of overall equilibrium in each class of painting. This optimal level could be defined in terms of input parameters. Optimal level of equilibrium for each technique of painting could therefore be determined. Equilibrium reduced the probability of generation of defects. Equilibrium at optimal level reduced the rate of decay too. Analysis of mechanisms of reduction of rate of decay disclosed the fact that all methods of reducing the rate of decay minimize decay by inducing equilibrium. It was therefore emphasized that induction of equilibrium at the optimal level is the most effective method available to reduce the rate of decay of mural paintings. Mechanism of reduction of rate of decay by induction of equilibrium behavior was investigated using simulated samples. Paintings in equilibrium maintained all factors at their moderate rates. These intermediate levels approached optimal levels of most actions. Equilibrium brought about proper coordination between all actions. It did not allow any action to grow beyond the favorable limit. It reduced tear and wear. It tremendously decreased the probability of formation of defects. These factors are important to all paintings. Method of inducing equilibrium behavior at the most optimum level is called stabilization. Possibility of practical induction of stabilization was tested on simulated samples. All possible methods of stabilization were investigated. These are repair of defects, environmental control and application of controlled amounts of input factors. All ancient paintings have defects as a part and parcel of their structure. Adequate repair of these defects is compulsory. Special emphasis is therefore given to test possibility of stabilization by repair of defects. Samples were subjected to destructive intervention to generate defects. Their behavior was measured and compared with normal samples. Repair was done with traditional material and synthetic material. Quality of repair done with synthetic material was better than traditional material. Quality of repair with traditional material was also at an acceptable level. Repair with synthetic material however deviated behavior away from equilibrium. Repair with traditional material was effective in bringing equilibrium closer to the original level. It was therefore decided that repair of defects with traditional material could reduce the rate of decay of traditional mural paintings. Possibility of practical adoption of the method was also investigated in five selected sites. Necessary actual measurements were done; conservation plans were developed. It was found from this study that repair of paintings with traditional material and maintaining their environment within acceptable ranges were adequate for stabilization. Elaborate measurements were not necessary to adopt the stabilization method. It was established that the stabilization method can be adopted as a systematic process of reduction of rate of decay and decreasing the probability of emergence of defects