Storage Materials (edited)                                                             Home Up

     by William M. Cole P. E.

See Also:
Mold & Mildew Summary
Understanding Mold
Prevention of Mold
Treatment of Mold

Game collecting today is for both fun and profit. Yet, the item you thought was going to increase in value year after year has suddenly turned yellow after only three months and is now worthless. What happened? What could have been done to prevent the yellowing? This article will discuss what materials are best suited for long term storage and the guidelines for proper preservation.


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 or equivalent material such as Melinex® 516. 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. (Mylar® is a registered trademark of DuPont Teijin films. Their brands of archival quality polyester films are Mylar® type D and Melinex® 516 of which they are exclusive manufacturers).


For years collectors have stored their movie posters, comic books, baseball cards 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 premature aging. Both polyethylene and polypropylene contain solvents and additives in their manufacture to assure clarity and increase the flexibility in the plastic. Polyethylene when uncoated without any solvents is 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 polypropylene is to add a substance called PVDC (Polyvinyl Dichloride which is a relative of PVC) to allow the material to be heat sealed. Therefore, once you add the harmful additive, the sleeve now becomes non archival and should not be used for long term storage.


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 comic collections. 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 impregnated 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 deacidify them before storage. Deacidifying sprays and solutions are now available for home use. By impregnating the paper with an alkaline reserve, you can neutralize existing acids and inhibit oxidation, future acidity and staining due to certain fungi. However it is best left to the professionals to deacidify your 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.

Bill Cole Enterprises, manufacturer of archival materials:
... or visit your local comic & game dealer.

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