Efficacy of Various Drying Methods

Hilary A. Kaplan and Kathleen A. Ludwig
Document Conservation Laboratory
National Archives and Records Administration


In our efforts to be prepared for water emergencies, the Document Conservation Laboratory at the United States National Archives and Records Administration (NARA) periodically augments and re-evaluates its emergency preparedness, response, and recovery plans. To date, most emergencies have been small and opportunities to observe and evaluate drying methods from available vendor services have been limited. This project was designed to provide a closer look at drying recommendations offered in the literature and compare these approaches to what would approximate real life circumstances. A deliberate decision was made at the outset of this project to avoid identifying the vendors used in this study to allow for complete objectivity in assessing the results. All participating vendors were aware of our study, but we do not know whether this knowledge had any influence on how our materials were handled. Conservation staff at NARA strives to keep current with available resources on recovery. Most recovery guides convey the bottom line, recommending one drying method over another based on a specific type of material and degree of wetness. Archives holdings represent a wide variety of formats and media that are often contained in one box. If an emergency affects a moderate to large quantity of holdings, sorting and culling disparate materials from wet records is not practical or even possible. Databases that identify record formats in a given location and pinpoint available space for re-locating materials from damaged areas promise to greatly assist in future recovery efforts. Knowing more about the quantity and composition of affected records will help to set priorities and minimize potential damage during response and recovery.

When materials get wet

Protective efforts to avoid water in direct contact with archives materials are imperative when we consider the potential damage that may otherwise occur. When exposed to water, papers and books absorb moisture. Hygroscopic materials like papers, boards, and skins increase both in size and weight. Because books are composite structures, their components--boards, cloth or leather, sewing, adhesives, and text paper may expand or contract at different rates. This differential expansion can cause damage to the structure of a book. Upon drying, leather and parchment shrink if not restrained. Wet parchment leaves can adhere if dried in contact with one another. Water can also cause metal fasteners to corrode. Corrosion from iron and copper weakens paper and often results in physical damage. Exposure to moisture can prompt image media to become soluble. The dissolution of media may transfer or bleed to adjacent sheets, move horizontally or vertically within the sheet, or completely obliterate information. Water may make components of paper soluble, such as dyes, sizings, fillers, surface coatings, and degradation products of aged papers. Formerly wet sheets may show characteristic dark tide lines formed by impurities in the water or dissolved degradation byproducts that have moved within a sheet. Mold is always a potential consequence of water damage when the drying process is delayed beyond a two-day period. The elevated moisture content of organic materials, such as the papers, leathers, parchments, and cloths found in libraries and archives, provides a conducive environment for mold to flourish.