Chemical archaeology to study our heritage?

Tuesday, 21 April 2015

What materials are the most frequently employed for creating artworks? What were the pigments and pictorial techniques employed by painting masters? Is it possible to analyse human evolution and the history of technology from artworks’ studies? Could you detect art forgeries? These are just some of the questions that you could answer thanks to the scientific study of artworks. 

Some recent publications from the University of Navarra and other Spanish and European Institutions deal with these interesting topics . In one of these investigations, the materials and technological knowledge used in the manufacture and application of Roman and Arabic mortars and stuccoes from buildings recovered from an archaeological excavation in the Real Alcazar of Seville were discussed. In this investigation, it is shown that the Arabs arranged their mortars and stuccoes in a noticeably different way from that of the Romans. Although in all cases lime, which was used as the binder, was combined with aggregates based on river sand from the depression of Guadalquivir, the binder-to-aggregate ratio and the particle-size distribution of the aggregates exposed clear differences between fragments coming from both cultures. After their analyses, we concluded that a decline in knowledge about lime technology over time occurred (Archaeometry 56, 4 (2014): 541-561).  
On the other hand, some knowledge of human evolution could be achieved by studying prehistoric rock art, as it was recently demonstrated in a study performed on black prehistoric drawings in the cave of Rouffignac (France) dated 13,000 years ago (Talanta 129 (2014): 459-464). Paintings represent horses, ibexes, mammoths, bisons and rhinoceros. Two manganese oxides, pyrolusite (MnO2) and romanechite (Ba2Mn5O10), were employed by the ancient artists. The nature and microstructure of manganese oxides can provide information about the provenance of the supplying sites, giving clues about some prehistoric human aspects. The experiments were performed by using a portable system coupling X-ray diffraction and X-ray fluorescence in the same apparatus. This equipment allowed a non-invasive analysis of the artworks, providing a complete characterization of the work.

The same apparatus was also employed in the analysis of a royal 15th century illuminated parchment, in which King Henry IV of Castile (1425-1474) conferred nobility on Gil Fernandez and Alonso Covo. Thanks to the study of this artwork, now preserved at the Archive of the Royal Chancellery of Granada, the reconstruction of its documentary archaeology was possible and this served as an initial point in the comparative study with similar works. Some of the materials employed in the decoration were gold and silver, vermilion and minium (red colour), azurite (blue), malachite (green) and lead tin oxide (yellow). For the parchment text, iron-based ink was employed (Journal of Archaeological Science 45 (2014): 52-58).      
In the last years, studies regarding cultural heritage have increased and many scientists are devoted to this research field. With a better Knowledge of the past, perhaps we can improve our future…

Adrian Duran
School of Sciences

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