Traditional consolidants commonly used for waterlogged wood conservation often present long-term drawbacks, prompting research into new and reliable alternatives. Reducing reliance on fossil-based chemicals that are harmful to people, the environment, and the climate is a growing trend, and sustainable materials are now being explored as alternative consolidants for conserving waterlogged archaeological wood. Among these bio-based products, sodium alginate, a natural polysaccharide, has shown promising potential. This study aimed to evaluate its effectiveness in stabilising dimensions of severely degraded archaeological elm wood during drying. Various treatments were tested, and dimensional stabilisation (ASE), weight percent gain (WPG), and volumetric shrinkage (Vs) were assessed. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to evaluate alginate penetration and interactions with residual wood components. Results indicated that the effectiveness of sodium alginate depends on the treatment method, with the soaking approach and slow drying providing the highest WPG and the best stabilisation without altering the natural wood colour. Although the best achieved anti-shrink efficiency of 40% is insufficient from the conservation perspective, sodium alginate has proven to be a promising consolidant for the conservation of waterlogged wood. Further studies will focus on enhancing its penetration and interactions with residual wood components.

Lignin is a major constituent of the plant biomass, on top of agricultural waste, and a by-product of the paper industry. At present, most waste lignin is burned for energy recovery, whereas only a limited fraction is exploited in industrial recycling processes. In the context of circular economy strategies and sustainable waste valorisation, lignin can be converted into advanced materials, such as hydrogels. Lignin-based hydrogels can serve as absorbents for heavy metal ions due to the negatively charged oxygens of lignin functional groups. These materials are currently employed as drug delivery systems, in water remediation, and as sensors. In this study, lignin is valorised through its conversion into nanoparticles embedded in a PVA–borax matrix and proposed for an innovative application: the cleaning of metal-contaminated stone artworks. Three lithotypes (Candoglia marble, Carrara marble, and travertine) were artificially contaminated with metal corrosion products and subsequently cleaned using the lignin-based hydrogel. The cleaning performance was evaluated directly on the stone surface by using a non-invasive approach based on portable Fourier Transform Infrared (FTIR) spectroscopy, single-sided Nuclear Magnetic Resonance (NMR) relaxometry and colorimetric analyses. In addition, Attenuated Total Reflectance FTIR (ATR-FTIR) spectroscopy was employed to characterize the corrosion products and the lignin-based hydrogel and elucidate lignin–metal interactions. Preliminary results suggest that the cleaning performance depends on the petrophysical properties of the stone substrate and on the nature of the contaminants. A synergistic contribution of the hydrogel components to the cleaning process was also observed. Graphical Abstract

Waterlogged wooden artifacts are often unstable when exposed to open air, and impregnation with polyethylene glycol (PEG) remains one of the most widely adopted conservation methods to ensure their long-term stability. Despite its widespread use, relatively few studies have focused on the interaction between PEG, water and wood. Motivated by the development and testing of new NMR-based imaging (MRI) protocols for analysing water-PEG-wood systems, NMR diffusion and relaxation experiments were first conducted on PEG-water solutions at increasing concentrations. High-field (9.4T) micro-MRI (µ-MRI) was then employed to examine the penetration and interaction of these solutions within chestnut wood, adapting diffusion models originally developed for medical diagnostics. NMR spectroscopy revealed clear concentration-dependent variations in relaxation and diffusion parameters, indicating a progressive reduction in molecular mobility with increasing PEG content. High-resolution µ-MRI weighted by T ₂ *, T ₂ , T ₁ , and diffusion (quantifying the diffusion coefficient D and the kurtosis parameter K ) allowed non-destructive observation of the wood microstructure and the quantification of relaxation ( T ₂ , T ₁ ) and diffusion ( D , K ) values in the earlywood and latewood regions during treatment. Increasing PEG concentration resulted in decreasing T ₁ and D values, while T ₂ and K exhibited contrasting behaviors associated with changes in local molecular dynamics and microstructural heterogeneity. Notably, the kurtosis parameter proved sensitive to microstructural differences between earlywood and latewood and to the progressive evolution of the system during treatment. Overall, the study suggests the potential of µ-MRI approach to capture the increasing complexity of the water-PEG-wood system, supporting its applicability for non-invasive monitoring of consolidation treatments in small samples of waterlogged archaeological wood.