Insights into mixed carbon–iron gall ink and its degradation

Authors: Miriam Alberico, Brunella Cipolletta, Manuela Rossi, Silvia Pizzimenti, Alessandro Grieco, Gennaro Tortino, Maria Francesca Sannino, Antonino Pollio, Adele Ferretti, Ilaria Degano, Leila Birolo, Andrea Carpentieri, Alessandro Vergara^*

Title: Insights into mixed carbon–iron gall ink and its degradation in eighteenth century manuscripts

Journal: Microchemical Journal 227 (2026) 118752

Status: open access: https://doi.org/10.1016/j.microc.2026.118752

The Journal has an impact factor of 5.2, and it is a stably Q1 in the subject category “Analytical Chemistry”

The UNINA study of mixed ink recipes is of broad interest because, during the millennial transition from carbon-based to iron-gall inks, mixed carbon–iron-gall inks may have represented a prolonged transitional phase. Understanding the impact and interplay of chemical, thermal, and microbiological agents on tangible archival heritage enhances our ability to preserve historical documents over time.

Here, we propose a multi-analytical approach combining optical and electron microscopy, vibrational spectroscopy, and high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). In addition, microorganisms were isolated and characterized from selected samples.

Our case study, based on the Vanvitellian letters and conducted in collaboration with the Royal Palace of Caserta, demonstrates the significant degradation of iron-gall components, which is difficult to detect in the presence of carbon black without the sensitivity of HPLC-MS/MS. These findings highlight the analytical challenges associated with the investigation of mixed carbon–iron-gall inks.

Accordingly, we propose and validate a protocol in which Raman spectroscopy is first used as a rapid pre-screening tool to detect the presence of carbon black. When carbon black is identified, the protocol recommends subsequent analysis by sufficiently sensitive HPLC-MS/MS to indirectly detect oxidation products of gallic acid, thereby providing a definitive identification of the ink formulation that would otherwise remain inconclusive.

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