Maria Perla Colombini
Knowing the chemical composition of a painting allows us to define not only the original materials (pigments, binders, paints) used by the artist but also to highlight the materials added in restorations or products induced by time and pollution.
In particular, the chemical characterization of organic binders is an important aspect for the reconstruction of the pictorial technique, but this investigation is made problematic by the fact that organic materials are particularly subject to degradation processes and are present in very low quantities, compared to the inorganic material.
At the current state of the art, techniques based on chromatography and mass spectrometry (SIFT-MS, EGA-MS, Py-GC / MS, GC-MS, HPLC-MS) are the analytical techniques that have the greatest potential in the recognition of macromolecules in pictorial micro-samples. In fact, natural and synthetic organic substances are complex mixtures of numerous chemical species that must be separated and identified in order to obtain a characteristic molecular profile, which provides significant information on the type of material used and on degradation products.
The knowledge at the molecular level allows, therefore, to choose an appropriate restoration approach in order to selectively remove the non-wanted materials without interacting with the original binders. Moreover, this knowledge also provides information for the authentication of ancient and contemporary paintings: a problem that has reached great proportions in recent decades.
This communication focuses on the application of micro-invasive techniques mainly based on analytical pyrolysis and chromatography / mass spectrometry that allow the characterization of macromolecules in a painting, showing how this knowledge can be useful to integrate historical information, and in the attribution of a painting to an artist. Some significant cases are discussed both for ancient and modern/contemporary art.
