Mineral Clays for Cleaning Tidelines on Paper-Based Artworks

Abstract Clay minerals possess several properties such as ion exchange capability, alkaline pH, adsorptive, swelling, and plastic behaviour, most of which are governed by their interactions with water. They have the capacity to interact with soluble molecules, which is particularly interesting for art conservation treatments. For all these reasons clays deserve to be considered for green and sustainable paper conservation interventions. In this work two phyllosilicates with different properties, namely montmorillonite and sepiolite, were investigated for the removal of tidelines on artificially aged paper samples. Water exchange, cleaning efficiency, and pH were evaluated comparing the clays to gellan gum, a benchmark cleaning hydrogel. A pouch made with regenerated cellulose was used to avoid direct contact of the minerals with the paper. The water sorption capacity of the clays combined with the specific permeability of the cellulosic membrane allowed for a homogeneous and easy to control cleaning. The formation of new tidelines, an inherent risk to any local conservation treatment of paper, was avoided. As an example, sepiolite was used for the local cleaning of a paper-based artwork’s multiple tidelines.