18th Century knowledge on microbial attacks on parchment: Analytical and historical evidence

A 14th Century illuminated codex underwent an extensive restoration in 1739. The intervention was necessary because the volume was “rotten”. Some purple stains are still visible and passed through multiple pages in the thickness of the volume, with a pattern that suggested a resurgence of the infection after the restoration of the manuscript. The unusual appearance of the halos and the light-pink colouring of some of the spots indicated that a topical treatment of some kind could have been carried out. The stains were analysed by non-invasive and micro-invasive methods in order to reveal the chemicals used to disinfect or bleach them and the structural effects of the treatment on the collagen fibres. The chemical compound used to treat the stains of the codex contained sulphur and potassium, it was strongly acidic and in a liquid form. Based on both the results and the knowledge of that time, we hypothesised that in 1739 the restorer was aware of “infectious” nature of the stains and tried to stop the action of microorganisms. The attempt to stop the process would be the testimony of a diffuse knowledge on biodeterioration phenomena, not yet consolidated, but already present.