Preservation

Efficacy of Various Drying Methods

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

Methodology

Seven sets made up of two boxes each were carefully packed with expendable materials. Special care was taken to place all items in the same order within the boxes. Six sets were wetted and dried; the seventh set remained as an untreated control.).

To approximate a real-life situation, we attempted to simulate two levels of wetness. All of the boxes were allowed to absorb standing water for a 24-hour period. An additional eight liters of water were poured over half of the box tops to simulate a sprinkler discharge or burst pipe. After 24 hours, water was released from the sink in which the boxes stood, and the records were left to drain for two hours prior to freezing.).

We observed that the boxes absorbed varying amounts of water. The boxes, we concluded, played a decided role in how well their contents became saturated. Papers with a high groundwood content, such as newsprint, were also seen to saturate while adjacent sheets wet up only to the immersion water line. This "sponge-like" property of ground-wood was most visible where water- soluble green felt-tip pen lines were marked in the same locations on three experimental sheets. Pen lines feathered on newsprint papers, but remained unaltered on the non-newsprint samples).

Specific directions from the selected vendors were then followed to prepare the wet records for shipping. All twelve wet boxes were wrapped twice in a layer of 4-mil polyethylene sheeting, each layer sealed with packing tape. The boxes were then placed in manual defrost chest freezers with a .7 cubic meter capacity.

It is critical to communicate with commercial drying facilities about how boxes containing records are to be packed. This will have a large impact on how well materials will survive transit and dry. Wet records can readily damage a cardboard box if precautions are not taken--such as wrapping the interior in plastic. Doing so will preserve label information on the exterior of the box, but means that records will be manipulated if the vendor requests that the plastic be removed to achieve optimal drying. It is, in fact, possible to leave the plastic lining in place by opening the top of the box to expose the records and allow the moisture to sublimate. Not removing the plastic at all, however, prolongs the length of time needed for drying. The care exercised in the packing stage inevitably pays off in the condition of the final product.

While efforts were made to provide similar samples for our study, a number of variables could have contributed to the final results observed. In examining the donated expendable records, it was clear that not all like groupings of records were identical. The number of pages within bound volumes, pamphlets, and folders varied, as did media. The composition and condition of record substrates were also different. Efforts were made to make the sample sets as similar as possible, but they were not identical.

Differential wetting may have occurred as uneven water absorption of the original corrugated cardboard boxes was observed. Boxes varied in board composition and age, though all appeared in good condition and sufficiently supported the records when dry.

All wet boxes were handled in the same manner prior to leaving the Archives, but we do not know the environmental conditions or duration of the overnight transport to the vendor. We also do not know how the boxes were handled once they arrived at the vendor's facility. Had the materials thoroughly thawed? Were the boxes crushed or misshapen during transit? Were boxes immediately placed into a freezer or did they sit for a period of time thawed and wrapped in their plastic? These unknowns may have contributed to item damage prior to the commercial drying process.

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