Relying on surrogates to stand in for complex, real-world book collections, this study compared five drying and two sterilization techniques to determine the long-term affects of these recovery options on the permanence of handmade and machine-made book papers.
Mechanical testing revealed that air drying, vacuum freeze drying, vacuum packing, and drying in a Vacme press with Zorbix had essentially no deleterious affect on handmade and machine-made book papers. Thermal drying, however, was shown to reduce paper’s mechanical strength
by 15 percent. Similarly, sterilization with ethylene oxide caused no mechanical damage to moldy, water-damaged book paper while gamma radiation weakened comparable book paper by 25 percent. These findings indicate that thermal drying and gamma irradiation should be avoided
when drying or sterilizing water-damaged books of permanent retention value.
Visual observation revealed that handmade papers dry with less distortion than machine-made papers treated by the same method. Books dried and pressed simultaneously (vacuum packed, Vacme press dried with Zorbix, and thermal dried under weight) produce flatter results than books dried without constraint. Thermal drying is therefore deceptive, producing visually flat books that are molecularly damaged. Air dried books can be rendered reasonably flat if they are pressed overnight followed by further air drying the next day. Vacuum freeze drying produced the least flat books in this study but the technique can be modified so that books are pressed during sublimation.
Cost factors for drying can vary considerably depending upon the availability and price of labor, or the initial outlay required for equipment such as a vacuum packing machine. Of the non-damaging techniques tested, air drying and drying with a Vacme press proved the least expensive, while vacuum freeze drying remains the most cost effective approach to drying large numbers of books. Multiple approaches can also be applied to the same recovery so it is reasonable to consider Vacme press drying, careful air drying, and vacuum packing books of enduring cultural significance while less valuable parts of the collection were vacuum freeze dried. As mentioned above, vacuum freeze dried can be modified to press books during sublimation when drying books of permanent retention value. Lastly, freezing wet books remains essential for delaying mold formation and thereby improving the quality of the recovery by allowing the books to be dried in manageable batches.
It is hoped this study’s findings help clarify for disaster responders the implications for permanence of specifying one drying or sterilization technique over another when treating water-damaged books.