ENEA has developed a diagnostic protocol for non-invasive evaluation of the state of conservation of ancient books and the effectiveness of cleaning treatments adopted by restorers to prevent or slow down aging and deterioration.

"Our method involves two non-destructive and non-invasive techniques - Raman spectrometry and optical microscopy - which, without pre-treating the samples, allow to obtain information on the morphological and compositional characteristics of paper, one of the most widespread and fragile materials of historical and documentary interest ", explained Sabina Botti, researcher at the ENEA Micro and Nanostructures for Photonics Laboratory, first author of the study published in the journal Molecules and conducted together with Francesca Bonfigli and Luca Mezi and Francesco Flora of the Plasma Applications and Interdisciplinary Experiments Laboratory at the ENEA Frascati Research Center.

"in order to slow down paper decay and restore the quality of ancient books - pointed out Sabina Botti - several cleaning treatments have been developed removing external contaminants and oxidation and decomposition products of the paper. But over time, not all of them retain the unique characteristics of an ancient asset." "To assess the "health" of paper before and after treatment - said the ENEA researcher - we used Raman spectroscopy^[1], a very effective analysis technique that uses 'light' to study the chemical composition of materials. It proved to be a suitable tool to determine the type of degradation and evaluate the effectiveness of cleaning treatments."

In particular, ENEA researchers used this diagnostic protocol to study the effect of different green cleaning processes, which are based on the application of non-aggressive and non-toxic chemical substances (hydrogels), or on direct irradiation treatments without pre-treating the samples, using radiation in the extreme ultraviolet (EUV) spectral range and combined hydrogel-UV radiation treatments.

"Among the different treatments analysed, we found that hydrogel has a good cleaning action: once applied to the paper, it captures and removes any degradation products and contaminants, like starch, gum arabic, animal glues and gelatin. The EUV irradiation, in addition to a cleaning action also of fungal species, induces an increase of the crystallinity index of the paper, i.e. a consolidation of the irradiated paper sample and a greater resistance to oxidation and aging", explained Sabina Botti.

Cellulose is the major constituent of paper and is a stable material, but over time it undergoes natural degradation which depends on various intrinsic factors (raw materials, production methods, possible presence of added substances), as well as the materials used (inks, pigments, binders) and storage conditions (presence of pathogenic organisms, air pollutants, exposure to incompatible light, temperature and humidity).