March 1999



Documents that have been rolled or folded for long periods of time (such as old and brittle "loose" records) resist opening and are likely to be damaged if forced open. Such documents may also be brittle, depending on the paper's age (especially if it was manufactured after about 1885), quality, and the conditions under which the documents were stored. Introducing moisture through humidification, followed by careful flattening, allows documents to return to a flat state safely. Humidification also reduces creases and fold lines that distort the image during microfilming. Great care, however, must be taken in handling fragile documents. Humidification should be closely monitored, so that excessive moisture is not introduced and the growth of mold or mildew is prevented. Coated (slick, magazine type) paper, photostats, photographs, and documents with water-sensitive ink (red and green) should not be humidified. Moisture causes coated papers to stick together, the emulsion (image) layer of photographs to soften, and colored inks to run.

If document exteriors have surface dirt on them, they may be gently brushed before humidifying to prevent dirt from setting in the paper. Do not attempt to open brittle documents for further cleaning. For more information, see "Surface Cleaning Documents and Book Pages," a handout from the ADAH Government Records Division. If possible, strings, rubber bands, paper clips, and other fasteners should be removed before humidifying documents. Should this effort threaten to cause damage, remove the fasteners following humidification and flattening. (See "Removal of Fasteners from Documents," another ADAH handout.)

Finding the best humidification method depends on the documents' fragility and how tightly they are rolled or folded. Of the two methods described below, the second is less likely to damage documents or encourage mildew. However, the first method should be used if documents are tightly rolled or folded.

1. Humidification Chambers. One type of humidification chamber is useful for humidifying large documents, such as architectural drawings or maps. To construct one, use two plastic trash cans-one of 30 gallons and one of 20 gallons. Cut several holes in the sides of the small can-near the top-to allow moist air to circulate. Pour about 2" of water into the large can; then place the small can inside it. This arrangement, with the holes high and the water level low, prevents water from seeping into the small can and wetting the documents. The water should be tepid., as using warm water may cause condensation and damage the documents. Place a tight-fitting lid on the large can to keep moisture inside the chamber. If the documents are too long to permit the lid to close, cover the container with a large piece of plastic sheeting and tie it to create a "tent," thus enclosing the documents and allowing humidification. The small (inner) can should be left open.

A different kind of humidification chamber-suitable for loose records and similar small documents-can be made from a rectangular plastic storage box, such as those available in discount stores. The box should be approximately 3' long x 2' wide x 2' deep and have a tight-fitting plastic lid. Preferably, it should also be transparent, so that documents inside may be observed. Pour approximately 2" of water into the box; then set plastic vegetable cartons, a wire screen, or some similar device inside so that it rests high enough (against the sides or on the bottom of the box) to keep documents well above the water, but low enough to permit sealing the lid. Several folded documents may be placed "on end" inside, leaving enough space between for moist air to circulate and for the documents to expand as they begin to flatten.

2. Flattening. After documents are removed from the humidification chamber, they should be flattened. Place them between two sheets of acid-free blotting paper or thin cardboard, then between two large pieces of wood (approximately 3/4" thick) or a sheet of plexiglass 1/16" thick. Place weights on top, and allow the documents to dry and flatten overnight. If the blotting paper or cardboard absorbs moisture from the documents, it should be replaced the next morning. The procedure will take from one to two days

3. Humidification "Sandwich." To create a "sandwich" that will both humidify and flatten documents, place a sheet of blotting paper or thin cardboard on a flat surface (such as glass, plexiglass, or wood); then hold one side of a second piece of blotting paper under a faucet and run water on it. Lay the second piece on the first piece, wet side up. Place a third, dry piece of blotting paper or cardboard on the stack, followed by a sheet of silicone release paper, the document(s) to be humidified, and a second sheet of silicone release paper. Make a second blotting paper/cardboard stack-exactly like the first one-for the sandwich's "top," so that the documents are in the middle. Place a weight (wood, glass, plexiglass, or lead) on top of the sandwich. If the documents are not dry and flat after 48 hours, repeat the process.

4. Monitoring Humidification. Monitor the humidifying process often to prevent documents from becoming too moist. It is best to begin humidifying early in the morning and to check periodically throughout the day. Never leave documents in the chamber or sandwich over a weekend. Remove the documents when they can be unrolled or unfolded without causing damage. Do not allow them to become wet, damp, or soggy. Documents that are sufficiently humidified should feel pliable and show little resistance to opening. Rolled documents will generally start to unroll during humidification. This process can be assisted by gently opening the documents in stages.

5. Supplies and Suppliers:

Trash cans/storage boxes, plastic Hardware or discount stores

Plastic sheeting (Visqueen) Hardware stores

Thin cardboard Art supply stores

Blotting paper Archival or library supply companies

Silicone release paper Archival or library supply companies

6. Sources of Additional Assistance. For lists of archival product suppliers, or for more information on this and other records conservation issues, contact: Linda Overman, ADAH Conservation Officer, at:

ADAH Government Records Division

P.O. Box 300100, Montgomery, AL 36130-0100

Telephone: (334)242-4452; fax: (334)240-3433


ADAH web site:

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