Project Objectives
To enhance the way that conservation science supports the conservation of wall paintings, the Getty Conservation Institute has partnered with a number of scientific laboratories to create the Organic Materials in Wall Paintings (OMWP) project. Advanced methods of investigation available today have demonstrated that organic materials were used in wall paintings far more frequently than was thought in the past. Therefore their identification becomes an essential part of all conservation projects to attempt to minimize the risk of damage and to improve methods of intervention.

	Lorinda Wong (GCI associate project specialist) using multispectral imaging to study the seventeenth century wall paintings cycle by Andrea Pozzo at the Mission of Mondovì. Photo: F. Piqué.

The goal of the project is to develop a set of guidelines to facilitate the study of organic materials in wall paintings. The project has two parts: first, to evaluate various investigation techniques and to develop a series of guidelines for organic materials identification; and second, to apply these guidelines to wall painting conservation case studies in order to illustrate the guidelines and their practical benefits.

This goal will be achieved through the following components:

• background bibliographic research (completed);
• evaluation of investigation techniques in the identification of wall paintings using wall paintings replica samples of known composition (ongoing);
• development of a methodology/approach to investigations, ranging from noninvasive imaging techniques to invasive methods (ongoing); and
• application of the methodology to wall paintings case studies (ongoing).

Project Overview
Historically, wall paintings have been made with a variety of supports, types of plaster, and painting materials (pigments and binders). The knowledge of the types of materials used in wall paintings and of their behavior is fundamental to ensuring appropriate conservation and maintenance procedures. While identifying inorganic components in wall paintings today is a relatively straightforward process, doing the same for organic materials remains a challenge.

	Conservation Scientist Giancarlo Lanterna (Opificio delle Pietre Dure - OPD) and Conservator Mark Gittins (Head of Lippi conservation team, Conservazione Beni Culturali) examining and evaluating results of invasive investigations on site. The OPD, one of the OMWP partners, has been responsible for the diagnostic investigation for this project, which included the characterization of the synthetic resins used during previous conservation interventions. Photo: F. Piqué.

When dealing with wall paintings, organic materials are typically added in smaller quantities than the inorganic materials (pigments and mortar). Organic materials are less stable and deteriorate faster than the inorganic components, and because of this, often only traces remain in centuries-old murals, making these organic components difficult to identify. In addition, the contamination by materials used in previous restoration interventions, such as the application of egg-based fixatives, makes the identification of the original organic components much more difficult. Finally, wall paintings are typically very heterogeneous and cover large surfaces (up to several hundred square meters).

For all these reasons, it is challenging to identify organic materials in wall paintings, thus making it necessary to use and combine information from several types of investigations. First, noninvasive investigations (that do not require sampling) provide topographical information on the distribution of organic materials on the surface; and second, invasive investigations (carried out on samples removed from the mural) provide much more specific information on the carefully selected area sampled.

Over the past fifteen years, the GCI has developed an expertise using invasive techniques such as infrared spectroscopy and gas chromatography and mass spectroscopy for the identification of organic materials in easel and panel paintings. Based on this expertise, the GCI has developed the project in partnership with several other scientific institutions with expertise in noninvasive and invasive technologies. For wall paintings, noninvasive technologies must be portable; in the past few years, more portable methods have become available. To that end, the OMWP project has attempted to evaluate available portable techniques for organic materials identification.

The starting point for the development of a methodology has been a set of wall painting samples of known composition that were used in the OMWP project to evaluate the potential and capacity of each analytical technique in identifying organic materials in wall paintings.

The identification of organic materials in wall paintings is an important step in any conservation program for three main reasons:

• art historical: support and advance the study of mural painting techniques and the understanding of artistic intent;
• diagnostic: contribute to the knowledge required for the understanding of deterioration processes; and
• preservation: provide the basic knowledge to develop a compatible conservation intervention (particularly cleaning and consolidation) and long-term maintenance programs.

The application of the methodology in case studies (a component of this project) will help illustrate the methodological approach. It will be used to highlight the implications that the presence of organic materials has in wall painting conservation and how this information can be used by conservators.

Last updated: April, 2006