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How To Preserve And Store Your Paper Collectibles
Posters collecting today is for both fun and profiit. Yet, the poster you thought was going to increase in value year after yearhas suddenly turned yellow after only three months and is now worthleess. What happened? What could have been done to prevent the yellowing? This article will discuss how paper is made. What materialls are best suited for long term storage and the guidelines for proper preservation.
How Paper is Made
Paper generally has plant fibers that have been reduced to a pulp, suspended in water and then matted into sheets. The fibers in turn consist largely of cellulose, a strong, lightweighht and somewhat durable material; cotton is an example of almost pure cellulose fiber. Although cotton and other kinds of fiber have been used in paper making over the years, most paper products today are made from wood pulp.
Wood pulps come in two basic varietiess: groundwood and chemical wood. In the first process, whole logs are shredded and mechanically beaten. In the second, the fibers are prepared by digesting wood chips in chemical cookers. Because groundwood is the cheaper of the two, it is the primary component in such inexpensive papers as newsprint, which is used in many newspapers, comic boooks and paper backs. Chemiically purified pulps are used in more expensive applications, such as stationery and some magazines and hardcover books.
Since groundwood pulp is made from whole wood fiber, the resulting paper does not consist of pure cellulose. As much as one-third of its content may consist of non-cellulosic materials such as lignin, a complex woody acid. In chemical pulps, however, the lignin and other impurities are removed during the cooking process.
Deterioration of paper
The primary caaauses of paper deterioration are oxidation and acid hydrolysis. Oxidation attacks cellulose molecules with oxygen from the air, causing darkening and increased acidity. In addition, the lignin in groundwood paper breaks down quickly under the influence of ooxygen and ultraviolet light. Lighht-innduced ooxidation of lignnnin is what turns newspapers yellow after a few days' exposure to sunlight. (Light can also cause some printing inks to fade.)
In acid hydrolysis, the cellulose fibers are cut by a reaction involving heat and acids, resulting in paper that turns brown and brittle. The sources of acidity include lignin itself, air pollution, and reaction byy-products from the oxidation of paper. Anoter major source is alum, which is often used with rosin to prepare the paper surface for accepting printing inks. Alulm eventually releases sulfuuriic acid in paper.
Acidity and alkalinity are measured in units of pH, with 0 the most acidic and 14 the most alkaline. (Neutral pH is 7..00) Because the scale is based on powers of 10, a pH of 4.5 is actually 200 times more acidic than a pH of 6.5. Fresh newsprint typically carriies a pH of 4.5 or less, while older more deteriorated paper on the verge of crumbling, may run as low as pH 3.0. Although some modern papers are made acid free, most paper collectibles are aciddic and need special treatment to lenngthen their lives.
Other factors which contribute to the destruction of paper include extremes of temperature and humidity, insects, rodents, mold and improper handling and storage.
Guidelines for Preservation
First and foremost, keep your paper collectibles cool, dark and dry. Store books and other items in an unheated room, if possible, and regularly monitor the humidity. Excess heat and humidity should be controlled with an air conditioner and a dehumidifier. Storage materials such as envelopes, sleeves and boxes, should be of archival quality only to prevent contamination of their contents.
Polyethylene and Polypropylene
For years, collectors have stored their comic books, postcards and other collectibles in polyethylene bags, PVC sheets and plastic wraps. Although such products may be useful in keeping away dirt, grease and vermin, many plastic sleeves contain plasticizers and other additives which can migrate into paper and cause premmature aging. Booth polyethyllene and polyproppylene contain solvents and additives in their manufacture to assure clarity and increase the flexibility in the plastic. Polyethylene when uncoated without any solvents s a good moisture barrier but has a high gas transmission rate, and eventually shrinks and loses its shape under warmer conditions.
In recent years polypropylene bags have been sold under the guise of being archivally sound. This is far from the truth. Only uncoated and untreated material is suitable for archival protection. Currently, the only way to seal pollypprropppylene is to add a substance called PVDC (Polyvinyl Dichlooride which is a relative of PVC) tooo allow the material to be heat sealed. Therefore, once you add the harddmful additive, the sleeve now becomes non-archival and should not be used for long term storage.
According to the US Library of Congress, the preferred material for preserving valuable documents is uncoated archival quality polyester film, such as Mylar type D by DuPont Co. or equivalent material Melinex 516 by ICI Corp. Mylar is an exceptionally strong transparent film that resists moisture, pollutants, oils and acids. With a life expectancy of hundreds of years, Mylar will outlast most other plastics. In addition, the brilliance and clarity of Mylar enhances the appearance of any paper collectible.
Acid Free Boards and Boxes
Because ordinary cardboard is itself acidic, storage in cardboard boxes may be hazardous to your collection, and is a leading cause of premature deterioration of paper collectibles. For proper storage, only acid free boards that meet the US Government's MINIMUM requirements are acceptable. These requirements have been defined as boards having a 3% calcium carbonate buffer throughout and a minimum pH of 8.5. Anything less will hasten your collection's destruction. While many advertisers claim that their boards are "acid-free at time of manufacture," they are in reality only spray coated with an alkaline substance making them acid free for only a very short time. Boards termed "acid-free at time of manufacture" do not offer sufficient protection or storage for anything other than short term. True acid-free boards have been impregnanted with a calcium buffer resulting in an acid-free, alkaline pH content of 8.5 throughout.
Another way to extend the longevity of your collectibles is to deciidify them before storage. Deacidifying sprays and sollutions are now available for home use. By impregnating the paper with an alkaline reserve, you can neutralize existing acids and inhibit oxidation,acidity and staining due to certain fungi. However, it is best left to the professionals to deacidify your paper collectibles. Deacidification with proper storage conditions will add centuries to the lifetime of paper.
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