Dear Donia,
What is the best way to preserve "onion skin" paper?
Q. Dear Donia,
What is the best way to preserve "onion skin" paper? It was written on with pencil, and I'd like to preserve it. Also, what is the best way to preserve letters, written on both sides of the page?
A. Dear Forest,
Different onion skin papers have different characteristics (find a good definition of onion skin at http://cool.conservation-us.org/don/dt/dt2375.html). The papers and inks (or other media) used for letters, one- or two-sided, have even more variety. Buffered paper enclosures are probably best for your two items, but only a conservator can give you an absolute answer. We can give you good general advice for paper preservation. Here are the essentials:
Storage materials
Use acid free or buffered boxes, folders, envelopes, sleeves, backings, and mats to prevent edge damage, creases, and tears. Acid free (also known as unbuffered or neutral, has a pH 6-7). Buffered paper has a pH 7-9.5. These types of materials are also free of sulfur, acids, peroxides, and other reactive materials. Don’t use buffered storage materials with blueprints—blue pigments in watercolors may also react.
If you use plastic, do not use PVC. Use uncoated polyester, cellulose triacetate, polyethylene or polypropylene. Don’t use polyester to store items that have unfixed pastels, charcoal, soft pencil, other loosely attached media, or visible flaking. Polyester can lift media and loose pieces. Look for storage materials marked PAT (passed a photographic activity test). Assume your pencil item risks losing material and use paper enclosures.
Find a stable storage space
Store paper items in a clean storage area where you can keep temperature and relative humidity (RH) moderate and stable: temperatures above 72°F, relative humidity above 50%. Large or fast changes in temperature or RH increase the rate of damage in paper and media. An air-conditioned room or closet is best.
Don’t expose paper to fumes, plywood, cleaning supplies, or cardboard. Avoid attics and basements, and provide good air circulation. Good housekeeping helps protect your treasures. Check regularly for signs of rodents, silverfish, “book lice,” and other pests; eliminate them if found.
Protect from light. All light, especially the ultraviolet (UV) part of the spectrum, causes fading and other damage. Store and display items away from natural and artificial light. Inks, watercolors, and newsprint are particularly vulnerable. Display framed items on interior walls away from sunlight, and keep indoor lighting exposure to a minimum. UV filtered glazing for frames or film for windows and fluorescent lights can slow, but not prevent, fading and other damage.
Handle with care
Store paper items by size, flat in boxes or on edge in folders (largest on bottom to smallest on top). For added protection, insert sheets of neutral tissue between items. Never use rubber bands, paper clips, or glues (for example, pressure-sensitive adhesive tape or rubber cement) on valued items.
Handle gently, Wash and dry hands often, and use two hands or a support under large or flimsy items to prevent bending. If an item is hard to unfold or unroll, or you have other questions, talk to a conservator.
For more information, see www.imls.gov/collections/index.htm. You can find one list of suppliers at www.nhhistory.org/archival_products_suppliers.html.
Simple Definitions/Glossary: http://ucblibraries.colorado.edu/preservation/Manual/terms.htm
The American Institute for Conservation can help you find a conservator in your area for an authoritative answer for your specific item (see www.conservation-us.org/index.cfm?fuseaction=Page.viewPage&pageId=495&parentID=472 for additional information).