People are enchanted by maps. They love them! I agree, maps are fabulous. They are functional, aesthetic, didactic. Some of you might have them at home, so here are a few tips for protecting their health and well-being:
1) Be wary of folding . One fold of an oversized map is acceptable, but when a cross-fold is introduced, it creates a point of great vulnerability where the two folds meet. You’ve probably seen this. Exposed paper fibers and a hole at the meeting place.
2) Rolling is acceptable with caution. It is advisable to roll the map around an interleaving acid-free paper which is larger than the map. The outside paper will protect the map from dust and dirt and will also protect the outer edges.
3) If your map is framed, determine if the matting is acidic or if the map is directly against the glass. Both are bad situations. The acid from the mat will migrate to your map and cause deterioration of the paper that it is printed on. If the map is directly against the glass, with a little humidity, the surface could adhere to the glass and cause what we in the business call, “a loss of information.” Here is my suggestion: Call up your local frame shop, ask if they have a pen to determine acidity levels, and if they would test it for you. (Or buy an pH test pen yourself- they are cost under $10.) Have a new mat put in if it was acidic. If pressed to the glass, the ideal would be to take it to a conservator, but you could cautiously try to detach the map from the glass, stopping immediately if it is adhering anywhere. Ultimately, spacers would need to be put in.
In the ultimate preservation situation, such as we have here in Special Collections, rare maps (many of which are non-acidic since since they were printed on cotton rag paper, pre-1850s or so) are encapsulated in a 3 or 4 mil polyester sleeve, put in a large acid-free map folder, and then filed in a flat steel cabinet. Our cabinets are kept locked so that in case of an earthquake the drawers don’t open and cause spillage. You might get a kick out of searching some archival product suppliers for these materials.
A final tip, keep your map out of the sun. Watercolors on rare maps could be fugitive. Also, keep your house at a steady temperature (ideally 60-65, but acceptable at 65-70) and make sure that it is kept in a low humidity area (aka not in the bathroom or a moist basement).
Let me know if you have comments or questions.