Unveiling the maniz. cod. 99: A microscopic and spectroscopic investigation of its writing inks

The Orthographia Pratica de Varias Letras is a unique 17th-century Portuguese codex, notable for its exceptional significance in the history of Latin calligraphy during the Modern period. Unfortunately, it faces complex conservation challenges due to the presence of iron gall ink (IGI). This work aimed to thoroughly characterise the inks and their impact on the manuscript using an integrated analytical approach. Extensive micro-XRF analysis revealed two distinct groups of IGIs based on their transition metal content. Zn-rich IGIs were found in half of the manuscript, suggesting the use of Zn-bearing green vitriol. In contrast, a more refined form of green vitriol was identified in the IGIs on the other half, suggesting that different types of vitriol were used. Variations in the binder-to-vitriol ratios were proposed, indicating distinct IGI formulations throughout the codex. The poor condition observed in some folios was primarily associated with greater ink coverage per surface area and lower binder content. FIB-SEM and PIXE analysis provided insights into the behaviour of Fe within the cellulose structure, including penetration and lateral migration. The IGI chromophore was further investigated by Mössbauer and XPS, which confirmed an Fe(III)-polyphenol mono-complex with a catecholate binding mode and Fe(III) in an octahedral arrangement.