RICERCA ITALIANA     

Novel technologies for assessing the level of deterioration of metals

Università degli Studi di Roma "La Sapienza"

Abstract

The cultural heritage suffer several methods of deterioration and its preservation cannot be based only on the experience of restorers, but must be based on suitable, validated scientific methodologies. In particular, metallic artefacts of archaeological and historic-artistic interest are subject to the interaction with the environment and quite often, when they are excavated if archaeological, or when they are restored if outdoors monuments, they are strongly modified with respect to their original manufacturing in their chemical composition or in their surface micro-structure and even in their bulk. Since the natural environments (atmosphere, water, soil) are complicated systems, changing with time, the interpretation of the full corrosion processes is very complicated and, even if they are well known, they give different results in different artefacts. Due to this situation it is very hard to find out general methodologies for assessing the level of deterioration of artefacts before restoration or their control for a preventive preservation.
The aim of this project is to determine some research methodologies, if possible not destructive, otherwise slightly invasive, for assessing the level of preservation of an artefact. We do not expect to find a single, general method, good for every metallic object. In this project we shall consider only copper alloys and precious metal alloys, that form two large groups of strong interest for the cultural heritage.
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Principal Investigator

Mario Piacentini Università degli Studi di ROMA "La Sapienza"

Research Objectives

The electrochemical and physical processes related to the corrosion and to the deterioration of metal cultural heritages are well known and widely studied. Nevertheless, each object or monument is different from the others, since its conservation state strongly depends on the environment in which it has been buried or exposed to the weather during centuries. In fact, the environmental factors contribute in a decisive way to the processes of corrosion and deterioration of the artifact; they can also act in a different way in different points of the object either because it is made of different metal or because different areas have been exposed in a different way to the action of the external agents. For example, it is not uncommon to find in an excavation objects similar, close to each other but with a very different conservation state. For these reasons, it is very important for the restorers of metal artifacts to know their grade of deterioration. Even if an expert restorer is able to sense it with his “eye”, is more and more fundamental to carry out a diagnosis with well tested scientific methodologies, in order to avoid operations traumatic for the artifact and to successively preserve it in an adequate way for its future conservation.
The first objective of the research is the study of the deterioration processes to which metal objects of archaeological and historic-artistic interest are subject. Due to the great amount of different typologies of metal artifacts >>>

First Results

There are different results that can arise from the proposed research, some concern the instrumental aspects and the development of advanced diagnostic methodologies, others are related to the possibility of monitoring the metal artifacts using standard procedures. Several of the techniques that will be used are at the present already employed for the study of metals, nevertheless all of them require a better optimization that, in some cases, implies significant instrumental changes.
The best aiming of all the techniques is certainly one of the principal expected results. Some instruments should be developed during the project and we hope that they will be significantly innovative for the study and the monitoring of ancient metal objects.
It is a common conviction among the specialists of this field that it is necessary to let the practice of conservation evolve towards investigation procedures that control and/or prevent the deterioration of the artifacts. The systematic study of the monitoring procedures most efficient for the different typologies of artifacts, a work that will occupy a great part of the second year of the project, is one of the most significant aspects of the project, also with respect to the possibility of a development of the metal conservation field toward procedures more modern and effective.
The secondary deliverables of the project are numerous and different. Certainly, the proposed research can contribute to improve the >>>

Timescale

24 months

National and international background

Modern science and technology are very important for a better knowledge of art and of cultural heritage. As an example we recall the use of thermo-luminescence and of radiocarbon dating methods in archaeometry, as well as the use of X-rays for investigating possible hidden layers in an art work. In spite of that, the application of modern science and technology in art conservation and archaeology is rather limited in comparison to the applications in other fields, such as medicine.
Let us consider medicine. Many years ago, an expert physician performed his diagnosis considering the symptoms shown by the patient and on external observations; however nowadays he can use more and more refined analytical techniques, specialised to the disease to be diagnosed: high contrast local radiographs, computer aided tomography, nuclear magnetic resonance, ecographies, etc.
Also the cultural heritage artefacts can be considered "patients" that can suffer several "diseases"; thus, the diagnostics either preceding a restoration operation or for preservation cannot be based only on the eye of the restorers, even if they are very expert, but it must be based on suitable, tested scientific methodologies.
The highly complex and diverse nature of the objects involved creates the need for an interdisciplinary approach, combining the expertise of chemists, physicists and engineers to overcome these obstacles and to expand the scientific and technological >>>