The role of atmospheric water in paper stabilization processes–determining the optimal relative humidity

From the perspective of deacidification and stabilization of paper as an information carrier, it is crucial to understand its interactions with water, including the transport of substances into and out of its structure, with consequences such as the swelling and shrinking of cellulose. Interactions of paper and water are significantly influenced by the paper’s structure, its composition, and the manufacturing process itself. The article focuses on studying changes in the water-paper interaction (liquid water and water contained in the moist air) on four model samples subjected to accelerated aging. The experiment is set up to simulate possible interactions occurring in the preservation/conservation processes of paper information carriers. The most significant result is the finding that an RH of 75% represents the ideal value of relative humidity for the treatment of paper information carriers, sufficient to ensure transport processes in the paper structure and at the same time not leading to excessive swelling or irreversible degradation of the paper yet. This point represents RH of the environment, where bound freezing water changes to free capillary water (second point from the isotherm). It is independent of paper composition and is not affected by aging.