Artists have experimented with a variety of organic natural materials for use as paint binders and varnishes, and as ingredients for mordants in gildings. Often artists used many layers of paint to produce particular effects. How we see a painting is thus the final result of how this complex, highly heterogeneous, multi-material and a multi-layered structure interacts with light. The chemical characterisation of organic paint materials in works of art is of great interest in terms of conservation. This is because the organic components of the paint layer are particularly subject to degradation. In addition, knowing the organic paint materials allows us to differentiate between the painting techniques that have been used over history. Applying GC/MS analysis to microsamples of paint layers is widely recognised as the best approach for identifying organic materials such as proteins, drying oils, waxes, terpenic resins and polysaccharide gums. This then provides essential information for reconstructing artistic techniques, for assessing the best conditions for long-term preservation, and for planning restoration. This paper summarises the more common approaches adopted in the study of organic paint materials. Our progress in developing GC/MS analytical procedures in the field of the cultural heritage is presented, focusing on problems that arise from the presence of mixtures of many chemically complex and degraded materials, from the interference of inorganic species, from the small size of the samples, and from the risk of contamination. We outline some critical aspects of the analytical strategy, such as the need to optimise specific wet-chemical sample pre-treatments in order to separate the various components, to hydrolyse macromolecular analytes, to clean up inorganic ions, and to derivatise polar molecules for subsequent GC/MS separation and identification. We also discuss how to interpret the chromatographic data so as to be able to identify the materials. This identification is based on the presence of specific biomarkers (chemotaxonomy), on the evaluation of the overall chromatographic profile, or on the quantitative analysis of significant compounds. Selected examples and case studies relating to paintings from various ages and origins are given.
|Autori interni:||COLOMBINI, MARIA PERLA|
|Autori:||M. P. COLOMBINI; A. ANDREOTTI; I. BONADUCE; F. MODUGNO; RIBECHINI E|
|Titolo:||Analytical strategies for characterising organic paint media using GC-MS|
|Anno del prodotto:||2010|
|Appare nelle tipologie:||1.1 Articolo in rivista|