Effects of Plastic on Philatelics, Stamps and items of Art

The topic of plastics involves an understanding of chemistry and physics that most people trust manufacturers and distributors of plastic products to have.

Unfortunately, as evidenced by the harm and damage many of these plastic products continue to inflict on many of our stamp collections, this does not appear to be the case. View below and other pages on this web site to see examples of plastic products sold by "trusted" manufacturers that over time have failed to live up to the promises made.

CAUTION ... ALERT ! ... read below to understand why some philatelic plastic products sold as "inert" and "safe" may not be what they purport to be !

Our first example to the right shows lower left portions of a plastic sheet holder sold by a well known manufacturer of philatelic and stamp products. This product is intended for display and storage of philatelic and stamp items. The top sheet has started to decompose and turn a discolored yellow brown, which is a sign that a chemical breakdown of the plastic has begun. Any paper items held within or by this plastic product will be exposed to its chemical reactions and eventually will be damaged. The bottom sheet is shown before the appearance of any breakdown. These "safe" sheets implicate the products of other manufacturers, who in many cases also purport their plastic products to protect and be "safe" and "inert", even when they are knowingly disclosed to comprise rubber, adhesives, paper, etc.

It is easy to assume that just because no damage is presently evidenced in your collection, that continued display and storage of your stamps in plastic products will cause no such harm. However, given enough exposure to external influences (VISIBLE light, UV light, temperature, humidity, pollutants...) all plastic products will eventually degrade and, thus, cause degradation and damage to your collection.

Need another example? Below is an image of a "Crystal" brand plastic stamp mount product sold in the 1970's. Notice the adhesive that was used to affix these holders to the album pages and that over time it has discolored. Although the clear plastic itself appears to not have changed color (yet), the yellowing of the adhesive is an indication that decomposition of at least part of the product has begun. Given enough time, the chemicals of the adhesive will migrate through the clear plastic of the holder to - you know where - the stamp held by holder. This is just another example why all collectors need be skeptical of claims made by manufacturers of philatelic products. DO NOT assume the plastic products you use are safe ... verify any claims made before entrusting you little pieces of paper to an unknown future under plastic.

The next example illustrates actual damage caused to a stamp by a plastic holder. In the image, ink from the stamp on the right is seen to have been transferred onto the plastic of the holder shown on the left. The transfer was caused by interactions with components of the plastic and the ink of the stamp. Some may argue that the image to the right does not establish causation, nevertheless, the result cannot be ignored. Image from Collings and Schoolley-West, The Care and Preservation of Philatelic Materials, London and State College, The British Library and the American Philatelic Society, 1989, reproduced by permission of the British Library

"To many people, plastics materials all appear the same but their variety is enormous. Many contain plasticizers, which act as molecular lubricants and are incorporated into the plastic's manufacture to increase the flexibility of the plastics in sheet form. These external plasticisers can volatilize and cause the plastic to become brittle or migrate into adjacent material where they can act as solvents for many inks, particularly gravure printing inks, ball-point and felt-tip pens and typewriter inks. Polyvinyl chloride (PVC) plastics have been commonly sold for storage of stamps, postcards, first-day covers, etc and are amongst the worst offenders. In addition to the plasticiser problem, PVC degrades to emit acid gases which can migrate into adjacent materials. Under no circumstances should PVC be used for any long or even short term storage." Page 43 of Collings and Schoolley-West, The Care and Preservation of Philatelic Materials.

In addition to PVC (polyvinyl chloride), four other types of plastic have been and continue to be commonly advertised and sold as mounts, holders, slabs, sleeves, and pages for storage and display of philatelic and stamp items:

• PET - polyethylene terephthalate (marketed as "polyester" or "Mylar®" or Melinex®)
• PE - polyethylene
• PP - polypropylene
• PS - polystyrene

Which of the above types of plastic is safe? Even the answer may depend on the vested interests of those giving it, the point to be remember is that given enough exposure to external influences (VISIBLE light, UV light, temperature, humidity, pollutants...) all plastic products WILL eventually degrade.

How long are you willing to wait before your stamps are damaged by your use of plastic products? In the case of common stamps and collections, their rarity or cost may not justify the time and expenditure needed, but what about philatelic rarities (some of which are shown on this web site)? Is there any amount of time that we can accept? In the case of polystyrene (PS), one person who has worked in the field of plastics states that polystyrene products (PS) are stable enough that they can be used for at least 100 years without worry that they will cause damage. However, keep in mind, the above 100 year estimate was based on accelerated tests made via exposures to changes in temperature. When exposed to the effects of other variables such as light, this estimate needs to be reduced. By how much? ... unfortunately, as indicated by the same expert, there have been few studies made with regard to the issue of effects of plastics on philatelic items.

Archive grade PET (Mylar®) polyester is considered by most in the archival and conservation fields to be the most "safe" plastic.

At this time, archive grade PET "Mylar®" polyester is the only type of protective plastic that is recognized for preservation of collections by The United States Library of Congress Preservation Office, which has very stringent requirements for the "protective films" used for their archival storage. Their "[c]omposition must be clear, colorless, (biaxially oriented/stressed/drawn) polyethylene film such as DuPont Mylar© D, Melinex © 516 or equivalent. The clear and colorless polyester film must not contain any plasticiser, surface coatings, UV inhibitors, or adsorbents and be guaranteed to be non-yellowing with natural aging. As received, the film must not contain any coloring agents. A certification of compliance with the above requirements must accompany the shipment." (The Library of Congress, Specification Number 400-005-1/93). See brief background on other types of plastic for more info.

As mentioned in the paragraph above, to be considered "safe", PET type plastics (as well as other plastics you may be tempted to use) should not contain any UV inhibitors. This requirement places a user of PET plastic in what is perhaps a Catch-22 situation. One of the mechanisms by which PET plastic "is" known to degrade, is by exposure to UV light, in which case, because we all want to from time to time to look at or display our stamps, and to look at our stamps we need light, if the light contains any UV component, even PET plastic can thus be a cause of damage. How can you avoid such damage ... it's simple, avoid/minimize exposure of your stamps to UV light (see Effects of UV light).

Keep in mind, it has been suggested it may be too early to draw any conclusions with regard to protective qualities of archival PET polyester based plastic products because they have not yet been shown to withstand the ultimate test of time. As well, as is discussed on a separate page under the topic of micro-climate, your stamps may be damaged by plastic (even PET) in other ways than discussed above.

Accordingly, consider the information above with the caveat, even archive grade PET polyester plastic products may eventually be found to be harmful sometime in the future.

However, if you choose to use plastic products with philatelic items of particular aesthetics, history, and value, archive grade PET polyester based plastic products should presently be considered as your "best" choice.

Are you now willing to implement use of archive grade PET (Mylar®) plastic with your collection? Your philatelic items and stamps await your answer.

 

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