Iron-galls inks: preparation, structure and characterisation

The formation of dark complexes due to the interaction between polyphenols and iron has been empirically exploited since the XII century for the production of the so-called iron-gall inks (IGI), which have been widely used for the production of manuscripts both in Europe and Middle East. Being part of the cultural heritage, these manuscripts are currently objects of interests which have to be carefully preserved. In this paper the current knowledge on IGI is reviewed focusing on the variety of ingredients used for their preparation, the available models describing the formation of the polyphenols-iron complexes, and their degradation patterns. Additionally, the range of instrumental techniques nowadays available for their characterisation is critically discussed highlighting for every technique the most important features for the study of IGI.