Piotr Targowski

One of the finest fifteenth-century portraits of the Burgundian Duke Philip the Good resides in the Musée des Beaux-Arts in Dijon. This small yet exceptionally crafted panel holds significance for both historians and art historians alike. Surprisingly, prior to this study, the context, the dating and the authorship of the piece remained obscure, and the widely circulated hypothesis of it being “a copy of a lost portrait by Rogier van der Weyden” has never been corroborated by convincing arguments. Clarifying the context, dating and authorship of the painting were the primary objectives of the investigations discussed in the article. Therefore, this painting underwent a multidisciplinary investigation spanning both the positive and human sciences. Macro-XRF scans were conducted alongside hyperspectral reflectance scans, multispectral imaging in the visible and infrared range, and optical coherence tomography. These analyses were complemented by an art historical study. As a result, a precise delineation between authentic and retouched sections was achieved. This article does not merely present the various perspectives separately but constructs a coherent narrative based on all these foundations. This holistic multidisciplinary research methodology produced a clear account, albeit with some scope for future inquiry. The involvement of the painter Pieter Cristus was conclusively demonstrated. This painter, whether himself personally, an assistant in the workshop or a contemporary follower, is attributed to the genesis of this work, which is presumed to be not the original portrait but a contemporaneous copy, possibly commissioned by the Burgundian Duke himself. While we no longer remain in the dark and have lifted some veils, this study also paves the way for further investigation into this panel and the numerous other portraits of Philip the Good.

Vincent van Gogh’s painting Congregation Leaving the Reformed Church in Nuenen from the collection of the Van Gogh Museum in Amsterdam was executed in 1884 and partially repainted by the artist in 1885. The painting was restored in 1961, however, the details of this treatment were not documented. After being stolen from the museum in 2002 and finally recovered in 2016, the Church was subjected to an extensive technical examination campaign which started in 2017. The aims were to: characterise the stratigraphy of both initial and later paint layers (including identification of the painting materials used by Van Gogh), evaluate the condition of the painting and assess the feasibility of the desired restoration treatment. Portable X-ray fluorescence spectrometry (XRF) was performed to non-invasively identify elements related to pigments in the paint layers of the two painting campaigns. To further identify constituent materials and comprehend the painting’s complex stratigraphy, a single paint sample was collected and embedded in resin for analysis by means of Optical Microscopy, Scanning Electron Microscopy with Energy Dispersive X-ray spectrometry (SEM-EDS) and Fourier Transform Infrared spectrometry - Attenuated Total Reflectance (FTIR-ATR). Additional non-invasive measurements were performed in a MOLAB campaign in 2018 by two complementary and portable analytical techniques: Optical Coherence Tomography (OCT) and reflection FTIR spectroscopy were used to gain further insight into the painting’s stratigraphy and identify surface layers across various regions of the painting. The presence of an original varnish under the paint from 1885 (and therefore likely applied by Van Gogh himself) was revealed by OCT. It was characterised as being protein based by FTIR-ATR and reflection FTIR spectroscopy. Based on the knowledge on the artist’s varnishing practice, it could be concluded that this most likely concerns an egg white varnish for the first time found in an early work by Van Gogh. The upper varnish layer, however, was identified as an alkyd resin applied during the aforementioned 1961 treatment. The combined use of FTIR and OCT enabled non-invasive in situ assessment of solvent cleaning procedures aimed at the selective removal of the 1961 restoration varnish with the preservation of Van Gogh’s original varnish. Specifically, OCT and FTIR analyses were carried out before, during and after each cleaning test to carefully assess the condition of the painted surface and that of the original varnish. The results of the cleaning tests aided in fine-tuning the procedure of varnish removal during the restoration process.

Titanium dioxide (TiO₂) is used as a UV light absorber to protect wood matter from photodegradation. In this paper, interactions between wood and TiO₂ coating are studied, and the efficiency of the coating is evaluated. For the experiments, two wood species were chosen: beech (Fagus sylvatica) and pine (Pinus sylvestris). Molecular and physical modifications in coated and uncoated wood exposed to UV radiation were investigated with Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and transmission electron microscopy (TEM). UV-VIS spectroscopy was used to describe the absorption of UV light by the TiO₂ planar particles chosen for the experiment. It was demonstrated that TiO₂ coating protects wood against photodegradation to a limited extent. TEM micrographs showed fissures in the wood matter around clusters of TiO₂ particles in beech wood.