Molecular Tracing of the Biological Origin of Drying Oils Used in Works of Art

Until recent times, artists have used a variety of binding media obtained from biological materials of animal or plant origin. Seed or nut oils capable to form a protective film when drying were an essential component of paints. Current methods such as gas chromatography coupled with mass spectrometry allow identifying biological origin of a specific drying oil, but chemical composition is a highly variable factor and can change with plant cultivar, soil, season or weather conditions of harvesting increasing the possibility of error. In addition, mixing oil from different biological species can mislead the analyses because it alters the composition of chemical compounds used in species identification. We report the development of a protocol for the identification of the biological source of drying oils used to prepare binding media for paints. Chloroplast DNA sequences were successfully amplified from tiny oil samples, both fresh and from aged pictorial models. Sequencing of the trnL-trnF intergenic spacer allowed to unequivocally identify the plant species from which the drying oils were derived. Our method shows high specificity and sensitivity and can provide new insight for studying ancient artwork by tracing the origin of the drying oils used by the artists.