The use of gellan gels in conservation of historic paper objects sensitive to water: research and practice

Abstract

Within the broad range of historic objects on paper substrates exists a large group of objects generally described as water-sensitive. In the vast majority of cases, it is caused by the character of the medium layers: painting, writing, drawing or even graphic, which exhibit the tendency to become soluble in an aqueous environment. This property is a serious impediment to performing safe aqueous conservation processes that are oftentimes necessary to clean, stabilize and strengthen the original structure.

Widely described in literature, as well as self-performed preliminary research concerning the properties of gellan gels allowed to point them out as a promising method, also in respect of historic objects with problematic medium layers. Analyses carried out on historic samples have shown that the gels caused significantly less bleeding of sensitive medium layers in comparison to traditionally used aqueous baths, although in many cases the bleeding was still substantial. In further research, the model of action was broadened by introducing medium layer consolidation/securing, carried out prior to the application of the gels. The tested substances commonly used for this purpose exhibited varying usefulness, largely depending on the specifics of particular medium layers. This suggests it is necessary to continue the research and to individually choose the methodology of treatment in accordance with the requirements of objects.

The analysis of the results and the gathered experience allowed to create and apply the model of using gellan gel sheets in the conservation of a series of 19^th century graphic prints and gouache projects. In both cases the particularly sensitive medium layers were first consolidated/secured and the application of gels itself was modified with additional processes, depending on the needs, including the use of enzymes and chemical gels.