Decontamination of archival cultural heritage materials with gamma radiation: a non-destructive investigation of paper and parchment documents from Montecassino Abbey (Cassino, Italy)

The conservation of Cultural Heritage (CH) materials, particularly archival documents and manuscripts, faces ongoing challenges due to biological deterioration caused by mold, bacteria, and insects. Traditional conservation and restoration methods are often invasive, time-consuming, and may involve the use of hazardous chemicals. In this context, ionizing radiation emerged as an effective, non-invasive alternative for the stabilization of fragile historical materials. This study presents the results of an experimental treatment using gamma irradiation applied to selected parchment fragments and paper documents from the historic collection of the Archive of Montecassino Abbey (Italy). The treatment aimed to assess the compatibility of gamma radiation for the conservation of both paper and parchment-based heritage objects. Pre- and post-irradiation analyses were conducted by coupling microbiological analyses with Raman, Attenuated Total Reflectance Fourier Transform Infrared (FTIR/ATR), UV–Vis spectroscopies and colorimetric measurements. The results confirm that gamma irradiation at the applied doses does not cause any significant structural or chromatic alterations to the treated materials, while ensuring a substantial decrease in fungal and bacterial microbial load. These findings support the suitability of gamma irradiation as a non-invasive and efficient approach for the decontamination of delicate CH objects, such as parchment and paper documents.