A stabilizer-free non-polar dispersion for the deacidification of contemporary art on paper

The preservation of cellulose-based works of art is threatened by the presence of acidity within the substrates, native, i.e., due to the papermaking process, or developed upon aging. The depolymerization of cellulose catalyzed by acidic compounds leads to a decrease in the mechanical properties of the artworks. Many strategies for hampering the acid-catalyzed degradation of cellulosic substrates have been developed in the past; unfortunately, few of them can be safely used on contemporary artworks, drawings or archival materials. In this paper, a new method for the pH control of paper, potentially compatible with most of ballpoint pen drawings and manuscripts, and also safely usable on folded or creased paper, is proposed. A deacidifying dispersion of calcium hydroxide in cyclohexane has been prepared starting from alkaline nanoparticles obtained via a solvothermal reaction. The most interesting feature of this formulation is that a stabilizer is not required for the preparation of a stable dispersion, differently from other commercial non-polar products. Cyclohexane is a colorless, non-polar, and volatile liquid that allows fast and simple applications by spraying. In order to evaluate the efficacy of this Ca(OH)2 nanoparticles dispersion in cyclohexane, mockups were prepared on acidic paper using a ballpoint pen. The protective action arising from the applied treatment was evaluated upon artificial aging, measuring cellulose viscosimetric polymerization degree (DPv), cellulose pyrolysis temperature, samples pH, and colorimetric coordinates. The interesting results obtained on mockups led to the application of this new formulation on a series of creased, perforated and burnt drawings from a private collection.