Stabilisation of iron gall ink: aqueous treatment with magnesium phytate

Abstract

Corrosive iron ions and acids in iron gall inks lead to enhanced degradation of paper. Several conservation practices have been used to stabilise endangered documents in the past centuries. The most effective aqueous stabilisation method developed to date is the so called “Calcium phytate” method. In this contribution we demonstrate that a treatment using magnesium phytate is equally effective, while additionally exhibiting several advantages. Due to the higher solubility of magnesium phytate compared to calcium phytate, it is not required to add an aqueous solution of ammonia, which poses several health risks. It is also shown that in order to optimise the efficiency of treatment, the pH of magnesium or calcium phytate solution should be adjusted to 5.8-6.0.