The European Synchrotron Radiation Facility (ESRF) has recently commissioned the new Extremely Brilliant Source (EBS). The gain in brightness as well as the continuous development of beamline instruments boosts the beamline performances, in particular in terms of accelerated data acquisition. This has motivated the development of new access modes as an alternative to standard proposals for access to beamtime, in particular via the “block allocation group” (BAG) mode. Here, we present the recently implemented “historical materials BAG”: a community proposal giving to 10 European institutes the opportunity for guaranteed beamtime at two X-ray powder diffraction (XRPD) beamlines—ID13, for 2D high lateral resolution XRPD mapping, and ID22 for high angular resolution XRPD bulk analyses—with a particular focus on applications to cultural heritage. The capabilities offered by these instruments, the specific hardware and software developments to facilitate and speed-up data acquisition and data processing are detailed, and the first results from this new access are illustrated with recent applications to pigments, paintings, ceramics and wood.

In this paper, the chromatic alteration of various types of paints, present on mural painting fragments derived from the vaults of The Upper Basilica of Saint Francis of Assisi in Italy (12th–13th century), is studied using synchrotron radiation. Six painted mural fragments, several square centimeters in size, were available for analysis, originating from the ceiling paintings attributed to Cimabue and Giotto; they correspond to originally white, blue/green, and brown/yellow/orange areas showing discoloration. As well as collecting macroscopic X-ray fluorescence and diffraction maps from the entire fragments in the laboratory and at the SOLEIL synchrotron, corresponding paint cross-sections were also analyzed using microscopic X-ray fluorescence and powder diffraction mapping at the PETRA-III synchrotron. Numerous secondary products were observed on the painted surfaces, such as (a) copper tri-hydroxychloride in green/blue areas; (b) corderoite and calomel in vermillion red/cinnabar-rich paints; (c) plattnerite and/or scrutinyite assumed to be oxidation products of (hydro)cerussite (2PbCO₃·Pb(OH)₂) in the white areas, and (d) the calcium oxalates whewellite and weddellite. An extensive presence of chlorinated metal salts points to the central role of chlorine-containing compounds during the degradation of the 800-year-old paint, leading to, among other things, the formation of the rare mineral cumengeite (21PbCl₂·20Cu(OH)₂·6H₂O).

Emerald green, a copper acetoarsenite pigment, enriched the 19th-century and 20th-century artists’ palettes and caused darkening and fragilities in paintings. The accepted alteration mechanism involves the oxidation of triarsenite ions [(As ₃ O ₆ ) ³⁻ ] to arsenates (AsO ₄ ³⁻ ), although questions about the promoting factors and the origin of the oxidized arsenic remain unanswered. This study investigates the primary environmental parameters inducing alteration in the oil binder and elucidates the associated degradation pathways through a multiscale analytical approach, including noninvasive spectroscopic techniques and synchrotron radiation–based x-ray methods. By combining results from a historical oil painting by James Ensor (1860 to 1949) and artificially aged paint mock-ups, we identified ultraviolet A–visible light and humidity (relative humidity ≥ 95%) as key driving factors, inducing a dual degradation pathway: Light promotes surface-stratified arsenic oxidation (As ³⁺ → As ⁵⁺ ) resulting in amorphous As ⁵⁺ -rich compounds, whereas a dark, high moisture environment favors arsenolite (As ₂ O ₃ ) crystallization. In addition, a noninvasive analytical strategy is proposed for monitoring the conservation state of emerald green paints in historical artworks.

Climate-change-driven increases in wildfire and fire incidents make fire-borne soot an escalating risk for tangible cultural heritage. Water-sensitive, porous gypsum plaster presents one of the most difficult surfaces to clean after flame-generated soot contamination because conventional methods can under-clean, abrade the surface, or drive soot into the pore network. Here we develop an atmospheric-pressure atomic oxygen (AO) cleaning technology and dose-controlled treatment framework for targeted, non-contact removal of soot from gypsum plaster. AO was generated by a non-equilibrium 13.56 MHz helium plasma source and delivered remotely as a chemically ablating effluent, enabling selective oxidation without direct plasma-surface contact. Compared with representative cleaning methods, AO removed carbonaceous contamination by preferential oxidation to volatile products. Under optimized low-power, high-flux conditions, AO achieved near-complete visual recovery with minimal substrate impact and preserved submicron topography. The results provide a reproducible, solvent-free framework for cleaning highly sensitive heritage surfaces.

The recent conservation and restoration phases of The Ghent Altarpiece have astonished scholars and the public alike by revealing the exceptional original brushwork of Jan and Hubert van Eyck. Yet some of the polyptych’s most intricate and enigmatic features remain under investigation: the applied brocades that form the richly decorated cloths of honour behind the Deity, the Virgin, and John the Baptist. To imitate the lustre and texture of luxurious silk and gold-threaded fabrics, the Van Eycks employed a highly sophisticated gilded tinrelief technique. These brocades, now heavily overpainted due to early degradation, present substantial challenges for conservation while offering a rare opportunity to study one of the few surviving prime examples of this demanding method. An extensive multimodal analytical campaign was undertaken to (a) identify remaining original metalrelief areas within surfaces repeatedly impacted by past interventions, (b) characterise the materials and layer stratigraphy, (c) document the current state of conservation, and (d) elucidate ongoing degradation mechanisms. Non-invasive analyses on the panels included upright and stereo microscopeaided visual examination, Macroscopic Xray Fluorescence (MAXRF) imaging, and Macroscopic Xray Powder Diffraction (MAXRPD). Complementary microanalyses on sampled material involved Field Emission Gun Scanning Electron Microscopy with EnergyDispersive Xray Spectroscopy (FEGSEMEDS), Fourier Transform Infrared Spectroscopy (μFTIR), MicroRaman Spectroscopy (μRS), Optical Photothermal Infrared Spectroscopy (OPTIR), and Synchrotron Radiation-based micro Xray Powder Diffraction (μSRXRPD). This study has directly informed ongoing treatment decisions and significantly advanced insight into the Van Eycks’ innovative metalrelief technique—one of the earliest and most refined examples in European painting.