Modelling the lifetime of colour photographs in archival collections

Colour photographs are among the most vulnerable materials in archival collections, making the development of tools for assessment of their lifetime in storage of particular interest. However, for this to be possible it is necessary to have a holistic understanding of what affects the lifetime of an object. Based on the existing knowledge of the effect of environmental conditions and material properties on lifetime of prints, this work focuses on the determination of end-of-lifetime using a value-based psychophysical approach. This research, carried out using a series of stakeholder workshops, showed that while assessor background does not significantly affect the end-of-lifetime determination, the nature of the images does. Isochrones, curves linking points of equal lifetime at paired environmental conditions, are defined. Based on these, a practical photographic lifetime calculator is presented, integrating dose-response functions with end-of-lifetime considerations. This tool, based on stock modelling principles, allows collection managers to input material stability data about the chromogenic prints in their collection and then investigate the effect of environmental scenarios on the collection. A case study of a collection at The National Archives, UK is also presented.