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Question: What type of plastic stamp mounts, sleeves and holders are considered "safe" for display and storage of old philatelic stamps and stamp collections?

Quick Answer: If you are looking to preserve and increase the value of your rare and old stamps, archival grade PET (Mylar®) polyester based plastic products should be your only choice.



Protect Rare and Old Stamps, Philatelics and Art from the Harmful Effects of Plastic

The topic of plastics involves an understanding of chemistry and physics that most people trust manufacturers and distributors of plastic stamp collecting supplies 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 the material presented below and other pages to view examples of stamp holders and stamp mount products sold by "trusted" manufacturers that over time have failed to live up to their promises made.

CAUTION ... ALERT ! ... read below to understand why many philatelic mounts and holders sold as "inert" and "safe" may not be what they purport to be !

harmful plastic philatelic stamp sleeve Our first example to the right shows lower left portions of a stamp sheet holder sold by a well known manufacturer of philatelic and stamp products. This plastic 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" stamp holders implicate the philatelic 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 by your collection, that continued display and storage of your stamps in plastic based holders 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 and reduce the value of stamps in your collection.

Need more proof? Below is an image of a "Crystal" brand plastic stamp mount product sold in the 1970's. harmful crystal brand plastic holderDo yo see how the adhesive that was used to affix these stamp 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 - if you have paid attention you will know where - the stamp held by holder. This is just another example why all collectors should be skeptical of claims made by manufacturers of stamp collecting supplies. DO NOT assume the plastic products you are using are safe ... verify any claims made before entrusting your top value stamps to an unknown future under plastic.

The next example illustrates actual damage caused to a stamp by a plastic holder. plastic sleeve ink migrationIn 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. You should ignore this and other images only if stamp valuation is not of interest to you. 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 collectible stamps:

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


Which of the above plastics is safe? Although the answer will depend on the vested interest of who is giving it, the point to be remember is: given enough exposure to external influences (VISIBLE light, UV light, temperature, humidity, pollutants...) ALL plastic products WILL eventually degrade.

So how long are you willing to wait before your stamps are damaged by your use of harmful plastic stamp products? In the case of common stamps and collections, their stamp value may not justify our time and expenditure, but what about your philatelic rarities?

Archive grade PET (Mylar®) polyester is considered by those 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 plastic product that is recognized "safe" 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 as they have not yet been areound for long enough to know if they can withstand the ultimate test of time. For example, 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 we have discussed on this page.

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, philatelic history, and stamp value, archive grade PET polyester based plastic products can presently be considered as being your "best" choice.

So, are you ready to implement use of archive grade PET (Mylar®) plastic to store your old stamp collection?


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