Synchrotron x-ray microtomography

[in inglese]

Case study: Characterisation of porosity in ground layers in canvas paintings

Subproject to synchrotron x-ray microtomography of paint samples

Led by
Ester S. B. Ferreira
Team
Jaap J. Boon, Claire Gervais (Associate Fellows), Nadim C. Scherrer, Karin Wyss
Partner
Paul Scherrer Institut (PSI), Villigen (Federica Marone)
Duration
2008–2011

Project description

Our first explorations of the application of synchrotron x-ray microtomography (SRXTM) to paintings studies in collaboration with TOMCAT beamline at PSI Villigen have shown that this technique, combined with advanced image processing, allows the study of ground layer porosity at submicrometer scale. Pore size, distribution, and connectivity are important properties, because they are related to the absorbency and material storage capability of a ground layer. Getting to know them will tell us much about the artist’s working methods, about the sensitivity of these layers to material introduction and storage (triggered, for example, by conservation treatments) and about how such interactions influence the painting’s long term stability.
For the characterisation of porosity we used material segmentation (based on grey scale value) and application of a clustering algorithm to the tomographic data. Applied to a sample taken from the painting Portrait of Max Leu by Cuno Amiet (1899, tempera on canvas) it revealed different properties at the surface and core of the ground layer: The areas closer to the sample surface and interface with other layers are highly porous with important connectivity and thus prone to material uptake and storage. The middle layer however shows low and non-connected porosity at the resolution level of the x-ray tomography images, so that few direct transport paths through the entire ground layer exist.

1) The sample surface and 2) the distribution of pores (blue), reconstructed from the tomography data

Data processing steps: 1) Filtered x-ray tomography data. 2) Segmented pore data (white). 3) Connected porosity separated in two large unconnected clusters (green and red)

The project was supported by

Swiss Re, Zürich

Publications

Ferreira E. S. B., Boon J. J., van der Horst J., Scherrer N. C., Marone F., Stampanoni M., «3D Synchrotron x-ray microtomography of paint samples», in: Luca Pezzati, Renzo Salimbeni (ed.), O3A: Optics for Arts, Architecture, and Archaeology II, Proceedings of SPIE Europe 2009, Vol. 7391, 73910L • © 2009 SPIE • doi: 10.1117/12.827511

Gervais C., Boon J. J., Marone F., Ferreira E. S. B, «Characterisation of Porosity in a 19th Century Painting Ground by Synchrotron Radiation X-ray Tomography», in: Journal of Applied Physics A • © Springer-Verlag Berlin Heidelberg 2013 • doi: 10.1007/s00339-012-7533-y.