Conservation treatment - Dramatic changes
Elmer Eusman (1997)
The field of conservation has undergone dramatic changes in the last several decades. [Editors note: Now in 2011, more than a decade later, we can say that views on conservation have probably changed even more. We choose to present this original text here to illustrate this development.] At the beginning of this century, when many museums began to establish restoration studios, treatment was generally devoted to aesthetic concerns. The aim of restoration (versus conservation, a more accurate term for current practice) was to return the work to its "original" appearance, often without regard for the long-term preservation of materials, the integrity of authentic components, or benign effects of aging and wear. Conservators today are also concerned with aesthetic appearance, but it is only one criterion of many when examining and treating cultural materials.
Today, conservators of paper materials are expected to have a strong background in chemistry as well as history (particularly art history) in order to interpret, predict and arrest the destruction of paper and applied media. Treatment and preventive methods are combined to improve the aesthetic appearance and the chemical and physical condition of art and archival materials. Repair of individual works is combined with collections care procedures such as maintaining proper storage and display environments (air quality, humidity, temperature and light). All materials age and deteriorate over time - it is the paper conservator's task to prolong the life of materials which define our collective heritage to future generations.
Iron gall ink corrosion poses a serious challenge for the paper conservator. The preservation and treatment of collections with iron gall ink is complicated by several factors: Hundreds of recipes were used to make iron gall ink. Despite the consistent use of four primary ingredients (water, galls, vitriol, and gum), the ratio in which they were used and the contaminants contained in each could differ greatly. Vitriol in particular could contain many other metals in addition to iron. The long-term effect of various additives and impurities contained in historic inks is still largely unknown.
Only recently have researchers been able to shed some light onto the complex chemical reactions responsible for color formation in the ink. However, the majority of research so far has focused primarily on the chemical breakdown of iron gall ink and the underlying paper. Research through the examination of dozens of historic recipes and inks, has shown that an excess of vitriol (iron sulfate) had been used in many prepared inks (H. Neevel, 1995). Excess iron sulfate creates a high concentration of iron (II) ions in the paper support. These free ions accelerate the oxidative breakdown of paper. The high acidity of most iron gall inks is caused by the presence of sulfate groups in vitriol or by additives such as wine, vinegar or hydrochloric acid. Acids hydrolyze the glucose molecules of paper, eventually causing the physical degradation of cellulose. Both of these degradation mechanisms - oxidation and hydrolysis - interact and increase the reaction rate of the other.
Ideally, a complete and effective treatment of iron gall ink corrosion must work on three fronts. Treatment should arrest current and future acid hydrolysis by removing water-soluble acid groups from the paper and introducing an alkaline buffer. Treatment should also block or retard oxidative degradation accelerated by the presence of excess iron. Finally, treatment should strengthen the physical condition of the ink and its underlying support.
Aqueous treatment combined with an alkaline buffer and iron(II) complexing agent will minimize oxidation and hydrolysis reactions. However, the use of water to treat objects with unstable inks has some serious disadvantages. Water itself is a necessary component for acid hydrolysis. In addition, a large proportion of ink and paper degradation products are water-soluble, and treatment with water may significantly alter the color of the ink and the overall tonal balance of the object. Furthermore, degradation products of ink corrosion may be deposited far beyond the ink line and throughout the paper when using water during treatment.
Mass treatment of archive collections prohibit the use of an aqueous technique because objects like bound volumes need to be treated as a whole. Alternatively, deacidification treatments utilizing non-aqueous organic solvents appear to be less effective since penetration of the alkaline product into the paper is limited. Currently no promising results have been achieved with the use of iron complexing agents delivered in a non-aqueous solution to arrest oxidative reactions caused by iron(II) ions. The use of alternative treatments for iron gall ink corrosion is undermined by the lack of cumulative data on the consequences of treating ink and paper materials. In the absence of naturally aged samples, researchers must rely on artificial aging techniques to predict long term effects of treatment. Unfortunately, artificial aging can never accurately simulate the complexities of natural aging processes.
These difficulties have led many conservators to rely solely on preventive conservation techniques when addressing the problems associated with iron gall ink corrosion. However, optimal storage parameters are still being refined. The final challenge for paper conservators is to educate collection keepers about the severity and extent of the problem of iron gall ink corrosion. Collections maintenance procedures are sometimes under utilized since not all objects show immediately visible signs of damage. However, it is only in collaboration with collection keepers and researchers that conservators can hope to find appropriate solutions.