Damage function for historic paper. part III: Isochrones and demography of collections

Background: In the context of evidence-based management of historic collections, a damage function combines aspects of material degradation, use, and consideration of material attributes that are important for satisfactory extraction of benefits from user interaction with heritage. In libraries and archives, it has been shown that users (readers and visitors) are mainly concerned with loss of textual information, which could lead to degradation being described as unacceptable, at which an object might become unfit for use and therefore damaged. The contribution explores the development of the damage function for historic paper based on data available in the literature. Results: We have modelled the dose-response function taking into account 121 paper degradation experiments with known T, RH of the environment, and pH of paper. The function is based on the Arrhenius equation and published water absorption isotherm functions for paper. New isoperm plots have been calculated and isochrones have been developed. These are plots linking points of equal expected 'lifetime', i.e. time until an object is expected to reach the state of threshold fitness-for-use. We also modelled demographic curves for a well-characterised research collection of historic papers, exploring the loss of fitness for use with time. Conclusions: The new tools enable us to evaluate scenarios of management of the storage environment as well as levels of access, for different types of library and archival paper. In addition, the costs and benefits of conservation interventions can be evaluated. The limitations of the function are the context of use (dark storage and reading), exclusive focus on the properties of an average paper type, and de-prioritised effect of pollutants; however, the latter can be considered separately. This work also demonstrates that transparent and publically accountable collection management decisions can be informed, and challenged by, effective interaction with a variety of stakeholders including the lay public.