Historical Preservation Tips

Originally written to a specific individual rather than as an information document.

Below is a list some basic steps you can take to help preserve old documents. It must be noted that having an item scanned is an excellent step, as it provides a working copy to use for whatever is needed and minimizes use of the original.

1. First and foremost, try to maintain a stable environment for the maps. You want to keep the humidity around the 50-60% range, but no higher as high humidity (especially with heat) encourages mold growth. Humidity that is too low is not good either; it stresses the fibers and can make the paper brittle. Temperature also should be around the same number range. For your purposes, the exact numbers are not as important as trying to avoid rapid, wide swings of temperature and humidity.

2. Keep the maps out of the light as much as possible. I understand you may want to display them, that's fine, but if you frame them use ultraviolet light filtering plastic or glass, and only display them for finite lengths of time, never permanently. All light, visible and invisible (primarily UV,) causes permanent, irreversible damage. So when they are not on display, store them in a dark place.

3. Store the maps flat, and dont put too many on top of each other. Ideally, store them in acid free folders, maybe three or 4 to a folder (depending on their size and weight), and interleave them (put between them) acid free paper or tissue. This prevents acid and ink from migrating from one map to another. It is acceptable to put them in mylar (polyethelene) sleeves, but keep a couple of things in mind. First, make sure the plastic you put them in is mylar, not some other plastic like PVC, etc., as they will harm them. Second, do not encase the maps - use the mylar as a sleeve, open at two or three ends. Mylar has a lot of static electricity that will hold the flaps together. Normally you dont want to seal a map inside mylar sleeve as it creates a microclimate that you cant control, prevents air circulation, and seals the acids in the paper inside with the map and accelerates damage. Finally, since mylar does have static electricity, care must be taken when you put them inside mylar sleeves.

4. Handle carefully. If in a mylar sleeve, you dont have to worry about your hands. If not, be sure your hands are really clean, and free from lotions, etc., and jewelry that can snag. There are two schools on gloves; some insist on it (to keep skin oils off the paper) but if the maps are fragile, you can damage it wearing ill fitting cotton gloves, so some just use bare hands but wash them very frequently. An alternative is latex or other material medical gloves, but be sure they are not heavily powdered. Lastly, when moving a big map, put it on a piece of cardboard so as not to stress the paper when it sags or bends.

5. Then, the basic stuff - keep them away from food, drink, and smoking, etc. Make sure your work area is large enough to accommodate and support the document. Watch out for ties, necklaces, etc, that might snag. Basically, avoid actions that might stress sections or folds in the paper. If you move an especially large item, scout the route and remove any obstacles and make sure to can get around corners, etc., and know where you are going to put it when you get there. Of course, get help if you need it.

6. If the map is important, and you really want to repair / preserve it, you will have to employ the services of a paper conservator. 7. I sometimes get questions from people about preserving newspapers  such as those with headlines from significant events, or clippings, etc. Unfortunately, newspaper is about as disposable an item as there ever was. It is simply not meant to last. Even in the best environment, the high acid content of paper will make it brittle and discolored within a couple of years or less, and if you attempt to display it in any way it will deteriorate even more quickly. The best thing to do with newspaper is to make a good copy, either digital, or on quality acid free paper, depending on what your needs are.

I hope this information is helpful. Please let me know if you have any more questions.

Eric Reinert
Curator
Office of History
Headquarters
U.S. Army Corps of Engineers