AIC's 46th Annual Meeting

Image Permanence Institute (IPI) has been studying the chemical and mechanical stability of collection materials for thirty years. One area of focus has been on the rate of moisture equilibration of library and archive materials. That research has led us to understand that it may take weeks or even months for an entire bound volume to equilibrate to a change in ambient relative humidity. However, experiential evidence demonstrates that the outer layer, or “skin,” of a book can react quickly to certain environmental changes leading to potential mechanical deformation. Studying the mechanical behavior of books is particularly challenging as they are three-dimensional, complex, composite objects made of diverse materials and constructed in a variety of ways. IPI is currently using a photogrammetry technique called Digital Image Correlation (DIC) to further our understanding of the mechanical behavior of common library and archive materials as well as the “skin” of bound volumes. Individual materials such as paper, book cloth, leather, and parchment were tested as well as bound volumes that range in date from early 18th century to late 20th century. Book samples are bound with a variety of materials and have varying structures, including tight back, hollow back, and perfect bindings in full, half, and quarter leather, cloth, and paper as well as full vellum bindings. DIC is a relatively new imaging technology that allows for the study of dimensional changes in two-dimensional and three-dimensional objects. A random dot pattern is applied to the test material and imaged in stereo. Software analyzes the images and measures dimensional displacement within the material producing 2-D and 3-D strain models. Of particular interest is the correlation between moisture transfer and strain, and the amount of strain experienced in bound volumes with changes in environment. This data will help determine the upper and lower limits of temperature and relative humidity necessary to avoid permanent deformation and will better inform our models for sustainable preservation environmental parameters.