Synchrotron based X-ray microtomography is a novel way to examine paint samples. The three
dimensional distribution of pigment particles, binding media and their deterioration products as well as
other features such as voids, are made visible in their original context through a computing
environment without the need of physical sectioning. This avoids manipulation related artefacts.
Experiments on paint chips (approximately 500 micron wide) were done on the TOMCAT beam line
(TOmographic Microscopy and Coherent rAdiology experimenTs) at the Paul Scherrer Institute in
Villigen, CH, using an x-ray energy of up to 40 keV. The x-ray absorption images are obtained at a
resolution of 350 nm. The 3D dataset was analysed using the commercial 3D imaging software Avizo
5.1. Through this process, virtual sections of the paint sample can be obtained in any orientation.
One of the topics currently under research are the ground layers of paintings by Cuno Amiet (1868-
1961), one of the most important Swiss painters of classical modernism, whose early work is currently
the focus of research at the Swiss Institute for Art Research (SIK-ISEA). This technique gives access
to information such as sample surface morphology, porosity, particle size distribution and even particle
identification. In the case of calcium carbonate grounds for example, features like microfossils present
in natural chalks, can be reconstructed and their species identified, thus potentially providing
information towards the mineral origin. One further elegant feature of this technique is that a target
section can be selected within the 3D data set, before exposing it to obtain chemical data. Virtual
sections can then be compared with cross sections of the same samples made in the traditional way.