Objects made from various materials, including porous, calcareous materials, glass, or metal, can be potentially damaged by reactions with anthropogenic pollutants in the exhibition environment. This project specifically addresses the widespread pollutant acetic acid. The formation of corrosion products, primarily acetate salts, can lead to damage and material loss. For many museum objects, a display case provides protection against dirt, vandalism, or theft. Additionally, it is intended to protect the valuable exhibit items from unsuitable climates and reactive compounds. The latter include various anthropogenic pollutants such as acetic and formic acid or sulfur dioxide. While low air exchange rates protect the objects inside the display case from pollutants entering from the surrounding environment, they allow high concentrations of pollutants from sources inherent to the display case, such as the construction materials used or agents from old restorations. Acetic acid causes corrosion through direct reaction with various materials, with the absorption and reaction mechanisms and reaction products differing for the affected material classes.
Passive display cases offer advantages over active cases for reasons of safe and sustainable operation, as well as from an economic perspective. A conditioning compartment in passive display cases allows for both the regulation of relative humidity and the reduction of pollutants by incorporating suitable materials that absorb pollutants faster than the objects due to high reactivity and deposition speed. For aesthetic reasons, small exchange surfaces between the presentation and conditioning compartments are often desired, which, however, negatively impacts substance transport and the establishment of transport equilibrium, consequently affecting the effectiveness of the conditioning agents. Thus, despite apparent protective measures, objects may still be exposed to high pollutant concentrations.
The primary goal of this project is to examine the corrosion processes in relation to the design of the display case, the pollutants absorbed, and the climate and pollutant conditions. Studies on the underlying damage mechanisms for various materials under diverse conditions will first consider the pollutant effect depending on the concentration. To this end, the time-dependent absorption of acetic acid will be examined for different sorbent and exhibit materials to compare deposition speeds and identify possible temporal changes in acetate affinity. The effectiveness of passive display cases will also be evaluated using a novel metric to describe the air exchange between the presentation and conditioning compartments. Such a metric provides added value when comparing different display cases and offers advantages to both producers and users through clearer product specification. Ultimately, the results on the metric and the damage effect and affinity of sorbent materials will be combined to conduct experiments with model display cases. The aim is to determine which structural modifications to the passive display case can contribute to improving conditions in the presentation compartment.
Finally, by examining the dynamic processes (substance transport and pollutant deposition) and their mutual influence, the project aims to make new and important contributions to the protection of objects from anthropogenic pollutants, benefiting all museum institutions and display case manufacturers. Despite the focus on acetic acid, the concepts can be applied to other pollutants, allowing analogous findings to be developed with reduced effort after the project’s completion.