STABILISATION OF CORROSIVE IRON GALL INKS

Jana Kolar,^a* Matija Strlič,^b Miloš Budnar,^c Jasna Malešič,^a Vid Simon Šelih,^b and Jure Simčič^c

^a National and University Library, Turjaška 1, SI-1000 Ljubljana, Slovenia

^b University of Ljubljana, Aškerčeva 5, SI-1000 Ljubljana, Slovenia

^c Jožef Stefan Institute, p.p.3000, SI-1001 Ljubljana, Slovenia

Abstract

Leonardo Da Vinci, J. S. Bach and Victor Hugo are just a few artists, who executed their works with iron gall ink. It has long been known that iron ions and acids in these inks induce severe damages to historical artefacts. In this contribution we demonstrate that transition metal content of historical iron gall inks varies greatly, with molar ratio of copper to iron as high as 0.7. Due to its superior catalytic activity, it is copper, not iron which contributes most to the extensive oxidative decay of many documents containing copper-rich iron gall inks. An effective stabilisation of ink corrosion is achieved by peroxide decomposer tetrabutylammonium bromide.