Parchments and coloring materials in two IXth century manuscripts: On-site non-invasive multi-techniques investigation

One among the most famous ancient parchments in the Islamic world, dating back to the IXth century, along with another contemporary one have been investigated by means of a completely non-invasive multi-techniques analysis combining all of elemental XRF and structural/molecular Raman, ATR-FTIR and FOR spectroscopies besides pHs and colorimetric measurements. The materials initially used in the preparation of the writing supports were identified; in addition to calcite at different extents, the parchments seem to be condensed tannins-pretreated. Furthermore, the exploration of amide I and II vibrational bands and sub-bands illustrated collagen gelatinization and molecular helix disorders phenomena. Parchments and inks degradation products, gypsum and calcium oxalates, have been also identified. In both manuscripts the writing black inks have been characterized as iron gall type. The corrosive effect of these black inks appears deeply damaging the acidic parchment supports. In this case, the high frequency side of the infrared spectrum disappears completely, illustrating thus irreversible parchment degradations. Gum Arabic, when added sufficiently in the black ink recipe, seems preventing the corrosive damaging effect induced by Fe2+ ions spreading from the black ink into the parchment body. Besides, all coloring materials have been identified; gold in gilded scriptures and natural pigments for vocalizations and basic decorations: cinnabar for reds, lapis-lazuli for blue and orpiment/realgar/pararealgar arsenic sulfides for yellow/orange shades. The anthraquinone-based kermesic acid extracted from Kermes female insects had been used for dark pink decorations, while the copper-based pigment verdigris had been synthetized to achieve green motifs. These results enrich the knowledge of ancient writing supports and materials, and highlight technologies and practices developed by middle-ages craftsmen. [Display omitted] •Middle-ages parchments have been explored on site by means of elemental/structural techniques: XRF, SSERS, ATR-FTIR and FORS.•ATR-FTIR analyses, supported by pHs measurements, permitted the identification of degradation products and the description of the conservation states.•Black inks have been characterized as iron-gall inks; gum Arabic, added as binder in the ink recipe, seems overcoming their corrosive effects.•All coloring materials have been identified and characterized: Gold was used in gilded scriptures while natural inorganic pigments an