Branco Weiss Fellow Since
2020
Research Category
Chemistry, physics, art and conservation sciences
Research Location
Institute of Chemical Technology, School of Engineering and Architecture of Fribourg, Switzerland
Background
Radiocarbon (14C) dating can identify when a work of art was created by determining the age of the material used. The drawback of this technique, however, is the need of taking a physical sample, which is very often prohibited on artworks. The support material is usually sampled, but it may not always be the best choice due to possible recycling. In the field of 14C analysis, the ongoing demand for smaller sample size has revolutionized sample requirements, where microgram quantities of carbon are now sufficient for a radiocarbon date and hence hold great promise to support the research of cultural heritage materials.
Within a painting potential candidates for 14C analysis are the organic binder or the pigments. Although a possible shelf-life is to be taken into account, the organic binder can only be used once and cannot be stored for decades, so bypassing the issue of recycled supports. In comparison to pigment anachronism, 14C analysis of the pictorial layer binder offers decisive evidence, regardless of the level of sophistication of the forger, as it targets the only material which accurately reflects the image being assessed. Nonetheless identifying a suitable sampling zone is crucial and requires the combination of additional analytical techniques.
The next step in extending the scope of candidates for 14C analysis within artworks is the possibility of dating the actors responsible for the object’s colour, namely the pigments. Whites, such as lead, titanium or zinc white are per definition inorganic and hence unfit for 14C purposes. Yet, exceptions are carbonates where the possibility of retrieving an age information from lead white revealed itself judicious. Indeed, the 14C signature of the carbonate anion was observed to be a robust archive of the manufacturing process, retaining its identity within the paint matrix and thus a useful proxy for the determining the time of creation of an object. The quest for new candidates for 14C analysis is not evident, as from the support material to the actual pigments, the complexity of the targeted compounds increases, hereby requiring innovative analytical strategies.
Details of Research
Organic pigments and dyes have been used for millennia to bring colour into our daily lives and our cultural heritage legacy retraces this practice. Their analysis has the potential to enrich our technical knowledge of the past but is extremely challenging. Within this project, Dr. Laura Hendriks will explore the potential of using 14C techniques on micrograms of carbon to extract the 14C signature of organic dyes, which are related to both historical textiles as well as art objects. Based on similarities with lipid biomarkers, a chromatographic separation approach is foreseen, followed by hyphenation with state-of-the-art accelerated mass spectrometer. The identification and dating of individual dyes may help in identifying the historical context of an art object or, retrace the trading route of a particular dye back to its geographical source. Ultimately, results of this study will set the foundation to the new applied field in cultural heritage studies.
