The primary mission of the Paper-Based Treatment section of the Preservation Laboratory is to assess and treat the NPRC's at-risk and intrinsically-valued records. To achieve its goals, the Laboratory employs a variety of strategies in order to repair, protect and retrieve information from damaged documents; to identify and clean mold-damaged records; and to prepare files for microfilming and archival storage.
Although fire and water damage from the 1973 Fire account for the majority of preservation-related efforts; the Laboratory also works to preserve and prevent against other threats common among archival institutions, such as insect damage, environmental hazards and general records deterioration incurred from years of repeated handling. Within the Preservation Laboratory, record preparation and treatment occur within a number of areas, including the Dry and Wet Labs.
The Dry Lab is where most of the NPRC's preservation work begins. Initial holdings maintenance (removing damaging fasteners, flattening creases and placing documents in protective housings) provides for a safer micro-environment for our textual materials. Such actions are also necessary to prepare documents for later, more intensive treatment or reformatting.
To prevent further informational loss or deterioration, holdings maintenance actions focus on:
- Restoring original document and folder order within collections
- Removing fasteners
- Placing fragile sheets into polyester sleeves
- Flagging sheets/leaves for later treatment, such as mending, adhesive removal, etc.
- Housing records in acid-free folders, boxes or custom-made containers
The Wet Lab is where more intensive single-item level conservation takes place. Treatments undertaken here include:
- Surface cleaning
- Mending of tears
- The use of polyester sleeves and document encapsulation
Surface cleaning is one of the first steps in paper conservation. Preservation technicians often use clean, soft brushes to remove loose dirt and debris from stronger, more flexible documents (some burned records are too brittle for surface cleaning). Foamed vinyl erasers, similar to a sponge, are also heavily used to remove dirt, as well as mold and soot on our burned records.
Surface cleaning is an important step, especially if later treatment will involve water, such as in humidification. While it is imporant to remove as much excess debris from the paper as possible, "over-cleaning" a document can lead to damage. However, if a record is slated for humidification, some cleaning is necessary; as once the paper is exposed to moisture, the residual dirt can work its way into the paper's fibers making it difficult or impossible to remove.
Textual documents that have been stored in folded and rolled positions usually have a tendency to resist opening. Sometimes creases in individual pieces of paper can be flattened by using simple tools, such as bone folders (a smooth, thin tool made of bone or Teflon having tapered or pointed ends). However, multiple folded pages stored in the same record file will often resist flattening. So too, some brittle documents can break or crack if opened, and many of the records salvaged from the 1973 Fire were severely distorted in the fire and aftermath. In these cases, humidification is necessary so that Preservation Technicians can safely unroll or unfold the documents.
Humidification is the process in which moisture is introduced into paper. The Preservation Laboratory uses humidity chambers to release water vapors inside an enclosed environment, relaxing the fibers of distorted and dehydrated documents. Once the moisture content of the paper fibers is increased, the documents are then placed between blotter sheets where they dry under pressure. The result is a flattened document suitable for use.
Mending is performed using a special repair tissue. The process involves the application of a thin coat of hand-mixed wheat starch paste and methylcellulose to the surface of light-weight repair tissue. The repair tissue is then applied over the tear on the blank or back side of a paper document, and light weights are placed over the repair to prevent cockling as the mend dries. Once dried, the mend provides greater protection for the document when used. In cases of severely damaged documents, not all tears can be mended. In these instances, Preservation technicians will piece together the document fragments in order to extract any available information.
Polyester Sleeves and Encapsulation:
Polyester sleeves are used to enclose and protect fragile, brittle and/or torn documents, as well as photographic prints and negatives filed among textual records. The Preservation Laboratory often uses sleeves with two adjacent sealed edges (L-sleeves) to maximize safe insertion and removal of fragile records.
Encapsulation is performed using an ultrasonic welder to seal documents between two pieces of polyester. The procedure is reversible, so the document can be removed if needed. Documents are not entirely sealed inside, unless specially treated. Corners are left open so that air can circulate within the polyester sleeve and natural decomposition off-gases can be released. Encapsulation makes documents easier and safer to hold and use.