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The gellan hydrogel is used as a cleaning agent for paper artworks. The purposes of this work were to give the gellan hydrogel both a microbial resistance and a cytocidal action against the biodeteriogens using hydrolates. Broth microdilution assays were performed to identify the fungicidal action of 16 hydrolatesvs3 fungal strains. The study concerned the Minimal Fungicidal Concentration and pH, colour, and ultra-structural variations on all paper samples, by placing them in contact with GELYD (GELlan + hYDrolat). Thein vitrotests showed that eight out of 16 hydrolates strongly inhibited fungal growth, but only two of them (Monarda fistulosa,Citrus aurantiumsubspamara) showedin situfungicidal action. Data indicate a new and interesting eco-innovative use of hydrolates, since GELYD is able not only to clean paper artworks, but also to kill the fungal cells present on paper that are potentially harmful for paper and operators. [ABSTRACT FROM AUTHOR]

Hypothesis Due to their highly retentive properties, innovative recently developed, semi-interpenetrated hydrogels made up of poly(vinyl pyrrolidone) (PVP) chains embedded in a poly(2-hydroxyethyl methacrylate) (p(HEMA)) network should be efficiently used as cleaning material for fragile and degraded paper artworks. In restoration practice, indeed the wet cleaning of these artworks is usually performed by immersion of paper in water, a procedure which may lead to several drawbacks, including paper fibers swelling and dissolution of water-soluble original components. Experiments This class of gels were yet presented in literature, but their interactions with paper materials and ability to be spiked with active enzymes (as cleaning agents), have not been analyzed. To establish the suitability of these hydrogels as paper cleaning materials, first, a rheological and microstructural characterization of the gels was performed. Moreover, diffusion of macromolecules inside gels was studied using fluorescence microscopy, to check if these innovative hydrogels can be used as carriers for hydrolytic enzymes. Indeed, pastes and glues are usually found in old paper artworks, and their removal is a very delicate operation that requires a selective action, which is granted by specific hydrolytic enzymes. At the same time, spectroscopic analyses on paper samples under investigation before and after cleaning treatment has been performed, thus assessing the capabilty of these gels as cleaning materials. Findings With the aim of demonstrating the versatility of these hydrogels, several case studies, i.e., the removal of grime and water-soluble cellulose degradation byproducts, the removal of animal glue and the removal of starch paste from real samples, are presented. Results obtained with these gels have been compared to those obtained by using another gel used for paper artworks cleaning, i.e., Gellan gel. [ABSTRACT FROM AUTHOR]

• PVA based chemical hydrogels are characterized and proposed for cleaning paper. • Characterization of modern and ancient paper before and after the cleaning was performed. • The cleaning abilities of the gels have been tested on ancient and modern paper. • Hydrogels cleaning ability depends more than their structure than on paper type. Wet cleaning of paper artworks by using hydrogels is a recently proposed process in the cultural heritage field. In this contest, on one side, research has focused on more effective and tuned cleaning hydrogels; on the other, the cleaning performances of the proposed hydrogels have been studied on ancient paper and very little on modern paper. This lack of information is not negligible, since the two kinds of paper differ strongly in composition. The difference, in turn could affect the performance of cleaning gels. In this article, new chemical hydrogels were synthetized using an oxidized polyvinyl alcohol (PVA) bearing an aldehyde group at each chain end, as cross-linking agent, i.e. telechelic PVA. PVA hydrogels have been characterized as candidates for paper cleaning applications. The possibility of tuning the mechanical and retentive properties, simply by changing the ratio of two polymer concentrations, their stability and transparency, indeed, render them, potentially suitable in cultural heritage field. The cleaning capability of two hydrogels, with different PVA/telechelic PVA ratios, has been assessed both on ancient paper, than a modern one and the results have been compared. The efficacy of these hydrogels has been demonstrated characterizing the samples before and after the cleaning process by means of a multidisciplinary approach involving spectroscopic and chromatographic tests. [ABSTRACT FROM AUTHOR]

• PVA based chemical hydrogels can be formulated with controlled architectures. • Characterization of the hydrogels shows their compatibility with paper artworks. • The hydrogels show different paper cleaning abilities depending on their structure. Hydrogel-based cleaning of paper artworks is an increasingly widespread process in the cultural heritage field. However, the search for tuned (compatible, highly retentive and not perishable) hydrogels is a challenging open question. In this paper, a complete characterization of chemical hydrogels based on polyvinyl alcohol (PVA) crosslinked with telechelic PVA and their remarkable performances as gels for cleaning paper artworks are reported. The rheological properties, porosity, water content of these gels were determined and analyzed as a function of the components concentration during synthesis. Due mechanical and retentive properties, the reported gels are optimum candidates for paper cleaning applications. The efficacy of these PVA-based gels has been demonstrated applying them on the surface of the sheets of several paper artworks, and characterizing the samples before and after the cleaning process by means of a multidisciplinary approach involving spectroscopic and chromatographic tests. [ABSTRACT FROM AUTHOR]