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►Catarina Rocha Pires – Surface dirt removal from unvarnished mechanically and solvent-sensitive paintings: a comparative study involving atomic oxygen, soft particle blasting and dry cleaning methods Abstract: The presentation will share initial results of a comparative study on cleaning unvarnished paintings that are sensitive to mechanical and/or solvent-based methods. These delicate surfaces, including water-sensitive and porous oil paints and acrylics, require alternative cleaning techniques to prevent damage. Tested methods include atomic oxygen (AO) cleaning, soft particle blasting, and dry cleaning. AO cleaning, currently in development as part of the Horizon Europe MOXY project, offers a unique non-contact method. It uses reactive atomic oxygen to break down carbon-based contaminants into CO, CO₂, and H₂O vapours. This approach enables effective cleaning without solvents or direct contact with the surface. The experiments included soot and an artificial soil which were applied to both water-sensitive and highly porous paint mock-ups. Assessments were made through visual observation, digital microscopy, SEM-EDX analysis, and colour and gloss measurements. AO cleaning proved highly effective on porous and oil-based surfaces, dry cleaning effectively removed soot from water-sensitive paints, and soft particle blasting showed promise for embedded soiling on acrylics. The work to be presented was developed in close collaboration with three master’s students, from the University of Amsterdam and the Courtauld Institute of Art (London). Bio: Catarina Rocha Pires is a PhD candidate at the University of Amsterdam, part of the Horizon Europe MOXY project, supervised by Prof. Dr. Klaas Jan van den Berg and Dr. Emilie Froment. She holds both a bachelor’s and a master’s degree in Conservation and Restoration from the NOVA School of Science and Technology in Lisbon, Portugal. Before beginning her PhD, Catarina gained practical experience in conservation and restoration and conservation science through internships at the Cultural Heritage Agency of the Netherlands (RCE) in Amsterdam, SRAL The Conservation Institute in Maastricht, and several museums in Lisbon.

► Caroline Bouvier – Tackling analytical limitations to enable routine ToF-SIMS imaging of heritage materials Abstract: Heterogeneous organic-inorganic microstructures in heritage materials can be investigated with mass spectrometry imaging techniques, such as Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Its asset is the simultaneous sub-micrometer mapping of both organic and mineral materials on a micro-sample. Past studies highlighted its potential and limiting factors. The SCIMITAR project combines a well-documented set of reference materials from several partners with the opportunity to dedicate time to exploring the instrument’s capabilities. Example of improvements of the technique’s suitability for heritage research questions include reducing signal distortions observed on insulating samples with cost-effective solutions, enabling optimized analysis of resin-embedded sample. It also consists in fostering data processing by sharing all new marker ions identified during the project in an open access peer reviewed database, to allow for unambiguous identification of given compounds. Bio: Caroline Bouvier obtained her PhD in 2022 at Sorbonne University on the application of ToF-SIMS imaging to heritage samples and the construction of a spectral database of pigments and binders. She then joined the scientific laboratory of the Bibliothèque nationale de France to work on the collaborative project ESPyON focusing on elastomers identification in collections. At the end of 2023, she joined M4i at Maastricht University as a postdoctoral fellow to work on the SCIMITAR project which aims to improve ToF-SIMS imaging’s capabilities for the identification of organic materials, specifically proteins, and to foster its accessibility for heritage research.

► Edith Sandström – The potential of fast mass microscopy (FMM) imaging in cultural heritage research Abstract: Mass spectrometry imaging (MSI) is an analytical technique with increasing application in the field of cultural heritage. Most MSI analyses are conducted in the so-called microprobe mode, where a mass spectrum is collected for each pixel to create a mass image. This puts a practical limit on the spatial resolution used or possible sample area investigated, as doubling either of those parameters results in a quadrupling in analysis time. In contrast to microprobe mode, fast mass microscopy (FMM) is a recently developed microscope mode MSI technique, which decouples pixel size from scan rate, enabling much faster imaging at high spatial resolution. Recent improvements have made it possible to analyse an area equivalent to the unfrosted area of a microscope slide (42.5 × 26 mm2) at 1 µm in just below 4.5 min. In comparison, this same analysis would take almost 128 days of active analysis for microprobe mode MSI techniques. These characteristics of FMM analysis means that the molecular information of entire small objects, such as jewellery pieces or miniatures, could in the future be collected in a fraction of the time compared to other MSI techniques, aiding our global understanding of these objects, and directing further research. Bio: Edith Sandström obtained her PhD in 2023 at the University of Edinburgh, working with National Museums Scotland. Her work focused on the development of less to non-invasive chromatographic and mass spectrometric methods for the analysis of historical dyestuffs. This included the introduction of a small-scale sample preparation workflow for chromatographic investigations, and the building and application of a DESI source for mass spectrometry analysis of historical textiles. Currently, she is a postdoctoral researcher at M4i, Maastricht University, working on developing advanced mass spectrometric imaging techniques, including fast mass microscopy, for application in fields ranging from biomedical to heritage science.

► Francien Bossema – Using in-house 2D X-ray equipment to make 3D CT scans of cultural heritage objects in museums. Abstract: A powerful technique for exposing the interior of museum objects is computed tomography (CT). However, the lack of affordable and versatile CT equipment in museums, combined with the challenge of transporting precious collection objects, currently keeps this technique out of reach for most cultural heritage applications. We propose an approach for creating accurate CT reconstructions using only standard 2D radiography equipment already available in most larger museums. Specifically, we demonstrate that a combination of basic X-ray imaging equipment, a tailored marker-based image acquisition protocol, and sophisticated data-processing algorithms, can achieve 3D imaging of collection objects without the need for a costly CT imaging system. We implemented this approach in the British Museum (London), the J. Paul Getty Museum (Los Angeles), and the Rijksmuseum (Amsterdam). Our work paves the way for broad facilitation and adoption of CT technology across museums worldwide and was recently published in Nature Communications. Bio: Francien Bossema obtained her master’s degree in Mathematics, with an additional specialisation in Science Communication & Society from Leiden University, The Netherlands. In 2024 she obtained her Ph.D. degree at the national research institute for mathematics and computer science (CWI) in Amsterdam, The Netherlands, in collaboration with the Rijksmuseum, Amsterdam, on the topic of ‘Tailoring X-ray tomography techniques for cultural heritage research’. Part of her research was performed at the British Museum (London, UK). During her Ph.D. she published four peer-reviewed first author articles, amongst others in Scientific Reports and Nature Communications. She is currently engaged as postdoctoral fellow at the Rijksmuseum, Amsterdam and as postdoctoral researcher at the Centrum Wiskunde & Informatica. Last summer, she was at the J. Paul Getty Museum in Los Angeles, USA, for a Museum Guest Scholarship. More information, such as a list of publications, presentations, blogs and videos, can be found here: fgbossema.github.io.

► Andrés A. León Baldelli– Cracks in Time: Analysing and Predicting Fractures in Paintings and Cultural Heritage Abstract: Cracks and fractures in paintings and other elements of our cultural heritage are transitional phenomena that significantly impact the stability and longevity of these artworks. These processes, driven by complex interactions of environmental and material factors, raise fundamental theoretical questions and have practical implications for the preservation and understanding of the artistic and historical legacy. I will share some theoretical insights on the modeling and analysis of these irreversible natural phenomena in the context of thin film fracture, introducing an intuitive energetic perspective on the formation and propagation of cracks which emphasises a key intuitive notion of observability for evolutionary processes. Some recently solved numerical problems illustrate the point. How can these tools be integrated with models, high-resolution imagery, and the many in situ observation data and empirical studies? I invite a discussion and collaboration in the modeling and simulation of crack phenomena in artworks, with the goal of developing a robust platform capable of simulating and predicting the formation and progression of cracks, as well as supporting conservation efforts. This platform aims to provide art historians, curators, and conservation specialists with a predictive tool for anticipating and monitoring damage in paintings, further enhancing our fundamental understanding of how matter responds to changing environmental conditions. By presenting these models, approaches, and data sources, I hope to stimulate collaboration within the heritage and conservation community to refine and validate our methodologies. Bio: Andrés León Baldelli is a CNRS researcher at the ∂’Alembert Institute in Paris, specialising in theoretical mechanics and applied mathematics. He holds an MSc from La Sapienza University and a PhD from Sorbonne Université [2]. Current research topics concern evolutionary systems, energy-driven pattern formation, variational methods, and singular perturbations. A recent contribution has focused on a numerical code for simulating fracture processes in brittle structures [3], enabling the study of arbitrarily complex crack patterns in diverse materials and geometries. References [1] Groisman, A and Kaplan, E. “An experimental study of cracking induced by desiccation.” Europhysics Letters, vol. 25, no. 6, 1994, pp. 415-420. [2] León Baldelli, Andrés A. On Fracture of Thin Films: a Variational Approach. PhD thesis, Université Pierre et Marie Curie-Paris VI, 2013. [3] León Baldelli, Andrés A. and Cesana, Pierluigi. Variational Solvers for Irreversible Evolutionary Systems. arXiv preprint arXiv:2404.08356, 2024

Yueer Li – “data-fusing” gamma spectroscopy with neutron tomography for non-invasive elemental analysis of bronze artifacts Abstract: A significant challenge in researching bronze artefacts is determining their elemental composition non-invasively. The most common technique used in museums, XRF, only detects signal from surface due to its limited penetration depth. Unlike X-rays, neutrons can penetrate bulk metals, making neutron-based methods the only possible approach to non-destructively access the interior of metal sculptures. Neutron tomography (NT) exploits this capability to reveal structures and is increasingly popular in bronze research, but the unavoidable gamma radiation induced by neutrons is traditionally seen as a drawback. However, this temporary radiation contains valuable elemental information that can be extracted “for free”. Based on this, I developed a ray-tracing simulation based method that combines gamma spectroscopy (GS) with NT, enabling both geometry and elemental composition of the interior of bronzes to be determined from a single NT experiment. In this presentation I will show the concept behind the data fusion and how it allows to obtain quantitative elemental information from two semi-quantitative experimental techniques. Bio: Yueer Li is a fourth-year PhD candidate in the Neutron & Positron Methods for Materials group (NPM2) of Delft University of Technology (TU Delft) under the supervision of Dr. Lambert van Eijck. She is involved in the NICAS “Beeldvorming” project, which focuses on developing neutron-based approach to look inside cultural heritage objects in a non-invasive manner.

Joen Hermans – Watching oil dry: Comprehensive characterization of drying oil oxidation and polymerization Abstract: Many issues in the conservation of oil paint lead towards a very challenging central question: what is the molecular structure of an aged oil binder? In this context, it is important to understand how factors like paint composition and curing conditions affect the chemistry and network structure of the oil binder, and subsequently the links between the structure and long-term paint stability. In our journey to answer these questions, we employed time-resolved ATR-FTIR spectroscopy and comprehensive data analysis to study the curing behavior of five types of drying oil and the effects of curing temperature as well as the presence of a curing catalyst (PbO). This approach yielded a very detailed insight into the changing chemistry of oils during drying. Analysis of reaction rates suggested that PbO induces a network structure with a more heterogeneous cross-link density, and the ATR-FTIR spectra indicate lower levels of oxidation in those cases. Finally, lower temperatures appear to favor the formation of more carboxylic acid groups in oil mixtures with PbO. Bio: Joen Hermans is Assistant Professor Conservation Science, a joint position between the Conservation & Restoration program and the Van ‘t Hoff Institute for Molecular Sciences, both at the University of Amsterdam. Since 2017, he has held an additional position as researcher at the Conservation & Science department of the Rijksmuseum. He obtained his PhD on metal soap formation in oil paint under supervision of Piet Iedema and Katrien Keune at the University of Amsterdam in 2017. Between 2018-2022, he worked on a NWO/Veni project studying the influence of water on oil paint chemistry.

Siavash Maraghechi – How the Night Watch canvas is doing: Canvas mechanics in multiple length scales. Abstract: The structural integrity of the canvas of the Night Watch is an essential factor regarding the safety of the loads applied to the painting by the new spring-tensioning system and the long-term stability of the canvas in terms of degradation. Careful inspection of the original canvas of the painting indicates a highly degraded and brittle state, leaving the lining canvas applied in 1975 as the main load-bearing part of the canvas system. The mechanical properties (Young’s modulus, strength, and strain at fracture) of the lining canvas of the Night Watch are experimentally assessed at three length scales, i.e., fibre, thread, and canvas. Dedicated methodologies based on in-situ micro-tensile testing are chosen or developed for each scale. By fitting a simple mathematical function to the experimental data, scaling laws are established for Young’s modulus and strength of the lining canvas of the Night Watch. These scaling laws can be used in the future to monitor the degradation extent of the lining canvas, based on a minimum number of non-invasive tests on individual fibres. Moreover, comparing the mechanical properties of the lining canvas with a similar canvas kept in less aggressive conditions at Rijksmuseum in Amsterdam sheds light on the current state of degradation of the lining canvas of the Night Watch. Bio: Siavash Maraghechi is a post-doctoral researcher at Eindhoven University of Technology (TU/e). He obtained his PhD in the mechanical engineering department in TU/e where he focused on microscopy techniques and full field methods for deformation measurements in complex materials. He entered the world of conservation science through a chemo-mechanical study of degradation of paper, where he developed a technique for accurate micro-mechanical testing of cellulose fibres, applicable to other materials such as canvas. Currently he is involved in a project concerning chemo-mechanical degradation of oil paints.