Mural Painting Digital Surveys

The method presented in this paper answers the following question related to the documentation of mural painting conservation: how can information technology be applied in order to achieve ease of symbolizing and updating, better accuracy, flexible presentation, ease of integration and cross-link with other data? Furthermore, another important issue: are all these possible at a low cost? 1. GRAPHIC DOCUMENTATION IN MURAL PAINTING CONSERVATION Often, during the wall painting conservation process, the mural painting conservator acts just like a geographer or, at least as a surveyor. The conservator has to know in detail how the original wall painting was achieved and what kinds of treatments were applied in the past, if any. Also, she/he must determine the current state of conservation as accurate as possible, including all types of deterioration encountered, and, at the same time, make all possible correlation with other information: chemical analyses, humidity measurements, operational tests and so on. All these data must be mapped “on the wall” (e.g. exfoliated regions, humidity maps, salted areas) in order to ensure the best conservation decision and, of course, to facilitate conservation works in the future, over the years. Therefore, “where the restoration of a mural painting is concerned, the purpose of documentation is to provide a detailed report of the results of examination, the methods used and the conservation treatment. This must be prepared as clearly and completely as possible for the benefit of interested specialists.” (Mora et. al., 1984, p.25) Generally, the mural painting documentation includes historical research, preliminary inspection and diagnosis, documentary survey. The latter consists of graphic documentation, photographic and video recording, written report (Cavezzali, 1994). Graphic documentation plays an important role in mural painting documentation because it represents the best way of providing a clear and systematic overview of the mural painting conservation works. It includes metric-dimensional survey of the structure, metric-dimensional survey of the painting, graphic base, thematic diagrams, symbology and glossary (Cavezzali, 1994). It is worth mentioning that, in most cases, geometric accuracy is not a critical problem. Usually, centimetric accuracy is satisfactory. This is because both the deteriorated areas and the conservation treatments are usually localized and reported relatively to the graphic features of the mural painting (graphic basis). The reporting of the deteriorated areas is based on conservator’s examination and interpretation. Of course, this process is subjective and the conservator’s responsibility is high. Hopefully, the future technological progress might offer appropriate sensors which will provide relevant data for assisting the conservator in this type of work. Actually, “nondestructive testing” (e.g. IR and UV based techniques) is a current research topic in the conservation of the works of art. Anyway, the use of the image processing techniques, which are currently used for remotely sensed data interpretation and classification, would be valuable. Nevertheless, there are cases when geometric accuracy is very important. In this context, photogrammetric techniques are required: “The application of this technique (i.e. photogrammetry) to mural paintings will prove to be valuable whenever a highly accurate record is required, for instance, to verify the possible movements in a building, or to determine the precise state to be re-established after the transfer of a painting” (Mora et. al., 1984, p.28)