Characterization and Digital Restauration of XIV-XV Centuries Written Parchments by Means of Nondestructive Techniques: Three Case Studies

Abstract

Parchment is the primary writing medium of the majority of documents with cultural importance. Unfortunately, this material suffers of several mechanisms of degradation that affect its chemical-physical structure and the readability of text. Due to the unique and delicate character of these objects, the use of nondestructive techniques is mandatory. In this work, three partially degraded handwritten parchments dating back to the XIV-XV centuries were analyzed by means of X-ray fluorescence spectroscopy, µ-ATR Fourier transform infrared spectroscopy, and reflectance and UV-induced fluorescence spectroscopy. e elemental and molecular results provided the identification of the inks, pigments, and superficial treatments. In particular, all manuscripts have been written with iron gall inks, while the capital letters have been realized with cinnabar and azurite. Furthermore, multispectral UV fluorescence imaging and multispectral VIS-NIR imaging proved to be a good approach for the digital restoration of manuscripts that suffer from the loss of inked areas or from the presence of brown spotting. Indeed, using ultraviolet radiation and collecting the images at different spectral ranges is possible to enhance the readability of the text, while by illuminating with visible light and by collecting the images at longer wavelengths, the hiding effect of brown spots can be attenuated.

Application of Spectroscopic and Hyperspectral Imaging Techniques for Rapid and Nondestructive Investigation of Jewish Ritual Parchment

“…Compared to calcium oxalate that shows only one strong C O stretching vibration around 1,320 cm −1 , copper oxalate exhibits 2 C O stretching vibrations (Nevin et al, 2008), which can be used for identification. As indicated by previous studies (Bicchieri et al, 2013;Pronti et al, 2018), the presence of oxalates can suggest a biological attack due to fungal species that are known to be able to reprecipitate secondary carbonates.…”

“…The presence of gypsum (CaSO 4 •2H 2 O) could also be inferred as indicated by the strong band around 1,080 cm −1 along the sharp band at 596 cm −1 and the peak at 664 cm −1 due to the S-O stretching and bending vibrations of the SO 4 group (Pronti et al, 2018), best seen on the ink area investigated. The O-H stretching and bending vibrations in the 3,550-3,400 cm −1 region and the bands at 1,684 and 1,621 cm −1 of the different water molecules typically found in hydrated Ca sulfates are masked by the collagen contributions.…”

“…These are both areas, which have a darker appearance. The literature reports the use of copper only as constituent of the writing ink, either as impurity or intentional addition in the vitriol (Hahn et al, 2007;Cohen et al, 2015;Pronti et al, 2018). For the analyzed areas, however, no direct correlation could be determined between copper levels and areas with writing, which may be due to the heterogeneity caused by mobility of the copper ions and infiltration into the parchment (Cohen et al, 2015).…”

“…Calcium carbonate (CaCO 3 ) could be present as indicated via the weak, but characteristic, band centered around 874 cm −1 (out of plane O-C-O bend) (Bicchieri et al, 2011). However, as important absorption bands associated with the fundamental vibrations of the carbonate ion in calcite (Pronti et al, 2018) are missing, a clear identification is not straightforward.…”

“…The O-H stretching and bending vibrations in the 3,550-3,400 cm −1 region and the bands at 1,684 and 1,621 cm −1 of the different water molecules typically found in hydrated Ca sulfates are masked by the collagen contributions. The presence of gypsum is not uncommon, powdered gypsum being sometimes used for the removal of excess fat in animal skin processing (Vichi, Eliazyan, and Kazarian 2018), for the acceleration of the drying process and ink absorption increase (Pronti et al, 2018), or, in illuminated manuscripts as a filler, for improving the mechanical properties and paint application (Melo et al, 2016). Some types of silicates could also be present (Derrick 1991) as indicated by the sharp peak around 1,002 cm −1 , the shoulder band around 1,024 cm −1 , and the peak around 530 cm −1 .…”