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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.
Mylar
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.
In summary, we recommend the following guidelines for the
maximum protection of your collectibles: Deacidify the paper;
store in Mylar sleeves with acid-free boards and cartons; and
keep the collection cool, dry and dark. Periodic inspections and
pH and humidity tests are also recommended. By following these
simple guidelines, you can be assured of a collection that not
only will increase in value, but will also last for many years
to come.
About the author:
William M Cole - Posters
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