Ion beam analysis of silver leaves in gilt leather wall coverings

Abstract

An analytical methodology involving Particle Induced X-ray Emission (PIXE) and Rutherford Backscattering Spectroscopy (RBS) was implemented to respectively characterize the composition and the thickness of silver leaves on gilt leather decors. These objects, ancestors of our wallpapers, are nowadays still difficult to date and their provenance is generally determined from stylistic studies. The initial aim of this study was to identify markers that could be correlated with the object provenance to help distinguishing the different gilt leathers workshops in Europe. The analytical methodology was validated on modern samples and applied to a corpus of 58 ancient gilt leathers from four countries. This study provided an assessment of the sensitivity of the ion beam techniques used, and highlighted the complexity of such analyses on thin silver leaves due to the different factors affecting them, and the composite nature of the object. Thus, the thicknesses calculated from the RBS analyses presented a great variability that seems to be related to the leaf characteristics, the manufacturing process and/or the life of the decor. Nevertheless, observations suggest that silver leaves coming from the Netherlands are thicker than the ones from Spain, Italy or France. Concerning the elemental composition, the results discarded previous hypotheses and the focus was made on gold and mercury trace elements, thus it was shown that leaves in Italian decors seem to have generally a low content of these two elements. Despite the large number of decor analyzed, the corpus should be expanded over to confirm the hypotheses raised by this research. Nevertheless the results gained from this work bring new light on the factors affecting thin metal leaves in general, which will be beneficial to all fields dealing with their analysis.

Angle-Dependent XRF Analyses: Pros and Cons of a Novel Technique in the Field of Cultural Heritage

“…Different methods can be employed to analyze layered samples, where IBAs (ion beam analyses) offer the best results. These techniques, coupled with induced X-ray emission (PIXE), characterize the layers composing the sample, evaluating the energy distribution of the backscattered particles, which depends on the nature of the elements composing the layers and the layers' thickness [19][20][21][22][23]. Additionally, as the volume of interaction of the particle depends on the particle energy, a variation of this energy (differential PIXE) allows for discrimination of the composition at different depths of the sample [24][25][26][27].…”

AR-XRF measurements and data treatment for the evaluation of gilding samples of cultural heritage

“…RBS allows the characterization of the layered structure of a sample by evaluating the energy distribution of backscattered particles, which depends on the mass of the hit nucleus, on the scattering angle and on the thickness of each layer. [24][25][26][27][28] Besides RBS, since the volume of interaction of incident particles is limited to the surface of the sample and is related to their energy, irradiation at different energies (the so-called "differential PIXE" 29 ) can be applied to discriminate among the different contributions of layers in the sample. The drawback of these techniques is the need to access a particle accelerator, which is not straightforward for many laboratories.…”