Traditional cleaning methods for removing undesired substances from artworks often involve the use of toxic volatile solvents, raising concerns about human health and environmental impact. Over time, various cleaning systems, such as thickeners, rigid, peelable, and nanostructured gels, have been introduced in the conservation sector to minimize solvent use and toxicity. However, these methods are primarily tailored for aqueous solutions or medium-to-high-polar solvents, leaving sustainable organogels for low-polar solvents largely unexplored. This paper explores the application of Low-Molecular-Weight Gelators (LMWGs) in the field of cultural heritage conservation, focusing on their potential to gel low-polar organic solvents. LMWGs, including cholesterol derivatives, fatty acid-derived compounds, anthryl, anthraquinone, amino acid, and saccharide-based organogelators, offer biocompatible and cost-effective options by forming supramolecular gels that immobilize solvents and reduce their release into the environment. This study highlights the need to transition from traditional, often toxic, solvents to greener and more sustainable cleaning systems by emphasizing LMWGs’ biodegradability, biocompatibility, and sustainability. While challenges such as optimizing gel properties and ensuring compatibility with artwork surfaces still need to be addressed, LMWGs hold promise as organogelators in conservation practice. Further research into LMWGs should focus on their optimization for conservation applications by adjusting their rheological properties and physico-chemical stability.

Currently, one of the most important challenges for the conservation of stone artworks is the removal of metal corrosion products on their surfaces. Traditional cleaning methods, which typically involve the application of aqueous solutions containing chelating agents capable of complexing these metal ions, have shown some weaknesses. These weaknesses become apparent when such methods are applied to statues and other vertical surfaces or when aiming to limit the cleaning process to a specific area with controlled application times. Furthermore, the porosity of the stone surface plays a role concerning the cleaning efficiency. To address these issues, chelating agents can be incorporated into gel-like materials. This study is a proof of concept to evaluate the cleaning efficacy of various gel formulations composed of polyvinyl alcohol (PVA), borax (B), and agarose (AG), loaded with two chelators: ethylenediaminetetraacetic acid (EDTA) and potassium sodium tartrate (PST or Rochelle salt). Three types of carbonate stones (travertine, Lecce stone, and Carrara marble) characterized by different porosities were artificially stained with copper sulphates and treated with the different PVA-B-AG formulations. The effectiveness of the treatment was directly monitored on the stones using a multi-technique approach that included scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and non-invasive portable nuclear magnetic resonance (NMR). Additionally, the rheological properties of the gels were investigated, and the Fourier transform infrared attenuated total reflection spectroscopy (FTIR ATR) was used to analyse the chemical structure of the gel before and after treatment, aiming to understand the changes induced by the cleaning process.

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