Gellan hydrogel as a diagnostic and cleaning tool for paper artworks: a case study

Wet cleaning of ancient papers is one of the most delicate and important steps in a conservation treatment. It allows the improvement of the optical qualities of a graphic work, the removal of pollution, and the partial dissolution of organic substances resulting from cellulose degradation. Nevertheless, washing by immersion - the common treatment- usually involves a substantial impact on the original morphological structure of the paper and could be dangerous for water sensitive inks and pigments. Moreover, it is also very important that the time of the cleaning process is optimized in order to remove all pollution and degradation products and to minimize invasive treatments. In this contest, a new wet cleaning technique based on the use of a rigid hydrogel of Gellan gum has been recently developed [1]. This gel is able to gradually release the water contained within their polymer network, [2] also to absorb the water-soluble degradation products present on paper. This compound is rigid and therefore its application and removal are fairly simple not leaving residues on the paper surface after treatment. Moreover, it could be easily combined with selective electrochemical biosensors, suitable to monitor the cleaning process. By the combination of this biocompatible hydrogel and electrochemical sensors, we obtained a new tool for diagnostic and cleaning use. In this way, it is possible to know when the cleanup process will be completed, avoiding lengthy and sometimes unnecessary cleaning material applications [3]. Here we report the results obtained by applying the proposed system to the “Breviarium Romanum ad usum Fratum Minorum”, a breviary of 18th century, highlighting the advantage and the potentiality of this new tool with respect to the traditional old paper cleaning methodologies. To this end, several invasive and not invasive techniques, such as, fluorescence microscopy, SEM, FTIR-ATR, HPLC have been used.