Gellan gum hybrid hydrogels for the cleaning of paper artworks contaminated with Aspergillus versicolor

he degradation of archive materials is related to irreversible phenomena induced by light, temperature, humidity, air pollution, micro-organisms, and use. Among biological factors, fungi can induce harmful effects in paper artworks. Further forms of damage (e.g. artwork swelling, fibre lifting and sheet delamination) can be caused by water immersion, which is one of the most commonly used methods for cleaning paper. To avoid damage it is necessary to control the amount and absorption rate of water by paper. Recently, gellan gum hydrogels have been proposed as effective tools to allow contaminant removal from paper supports, owing to the controlled water release and adhesive properties of gellan gum. In this study hybrid hydrogels were fabricated by doping gellan gum either with calcium compounds (calcium sulphate, hydroxide, chloride, and acetate) or titanium dioxide nanoparticles in order to evaluate their ability in cleaning different types of paper samples affected by spots originating from Aspergillus versicolor. The best decolourization results were obtained by calcium acetate/gellan gum hydrogels and titanium dioxide nanoparticle/gellan gum hydrogels, while no synergistic effect was found in paper samples treated with calcium acetate/titanium dioxide/gellan gum hydrogels. Hybrid hydrogels were tested on a case-study book.