Book and Paper Conservation 2009

Gepubliceerd op 13-07-2009

Abstract

Eliza Jacobi

Local repairs on iron gall ink

This thesis deals with a notorious problem in paper conservation: iron gall ink. For centuries this ink was used for all kinds of documents (government documents, but also drawings). Iron gall ink causes ink corrosion. The ink affects the paper, which in the course of years slowly disintegrates. The reason is the presence of two detrimental substances in iron gall ink: iron(II)ions and acids. These substances may, under the influence of the presence of fluids, migrate from the ink into the surrounding paper. As a result, the area of ink corrosion is considerably increased.

Areas with ink corrosion are brittle. This causes tears to emerge during its handling. In paper conservation tears are repaired with Japanese paper and water or ethanol soluble adhesives. It is the solvents, which cause the migration of the detrimental products from the ink. Here one notices an important dilemma for paper conservators. Using adhesives is necessary, as tears need to be repaired or consolidated in order to prevent further disintegration. At the same time there is the possibility that the adhesives worsen the situation. So far, paper conservators have not reached a consensus over how to solve this problem. The main question of this thesis is therefore: Which adhesive is most suitable for local repairs on iron gall ink, and how should this adhesive be applied?

Detail of a degradation crack in a capital letter 'D'. The crack has sharp brittle edges.
Letter originating from the ICN study collection. Photo: author.

On basis of the results of a questionnaire distributed among paper conservators and an extensive literature survey four adhesives (methylcellulose, Klucel G, Gelatine and wheat starch paste) and two methods (adhesive in gel-form and remoistenable tissue) were chosen, each of which is usable for repairs of iron gall ink. Various experiments were carried out subsequently to show the exact consequences of the use of these adhesives and methods. The normally invisible migration of the detrimental substances from the ink was made visible with indicators (bathophenanthroline for iron(II)ions; methyl red pH indicator for acids; and cobalt chloride for water). These were used to make indicator papers, which were stamped with lines of iron gall ink.

Only the bathophenanthroline indicator paper was found sufficiently reliable for testing the various adhesives and methods. These tests produced some interesting results. In using the remoistenable tissue method all of the four adhesives may be applied in such a way that no migration of iron(II)ions is caused. However, it is argued that gelatine is the most suitable adhesive for this particular repair.

The main conclusion therefore consists of the advice to apply the remoistenable tissue method with a 3% gelatine solution (high Bloom, type B, pH >5.5) for local repairs on iron gall ink. Finally, a quick and effective method was developed by the author to apply the adhesive. This method is demonstrated through a photo documentary.

Eliza Jacobi, elizajacobi@gmail.com