Why Mylar D – Melinex 516 is the Only Plastic You Should Use to Protect Your Collections
In my last post I suggested that before making assumptions about the safety of the plastic sleeves, sheets, films, envelopes, holders and storage products you use with your collections, you might want to learn how wrong choices of plastic could negatively affect the condition and value of your collections.
To support this suggestion, look at my next example below: where ink from the stamp on the right can be seen to have been transferred onto the clear plastic sleeve that is has been removed from on the left.
The transfer of ink was caused by interactions between the chemicals the clear plastic was made from and the ink of the stamp.
Can you imagine your reaction if you were the one using the plastic stamp sleeve below and saw the damage, but instead of with the stamp below, with a Jenny Invert or British Guiana 1c magenta philatelic rarity?
You should ignore the warning this stamp sleeve is trying to give you only if maintaining the value of your rare stamps, baseball cards, comics and art is of no 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 plasticizers 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 the PVC (polyvinyl chloride) plastic describe above, four other types of plastic have been and continue to be commonly advertised and sold as mounts, holders, slabs, l-sleeves, and pages for storage and display of collectibles:
- PET – archive grade polyester film (sold as Mylar D and Melinex 516)
- PE – polyethylene
- PP – polypropylene
- PS – polystyrene
Even though all of the types of plastic have been sold by plastic suppliers as being safe for storage and display, the evidence presented by the stamp above clearly illustrates that some of the suppliers of plastic storage products are not telling the truth.
So which of the plastics above is the “safest” and the “best”? Even though your “trusted” stamp supply dealer may be selling and advertising their storage, display, and paper conservation supplies and products as being usable for archival preservation, at this time, there is only one type of plastic that is considered by the United States Library of Congress Preservation Office as being “safe”, which has very stringent requirements for the protective films and and plastic sleeves they use for paper preservation and archival storage of their collections.
If you are serious about paper protection and paper preservation, your protective plastic films and their “[c]omposition must be clear, colorless, (biaxially oriented/stressed/drawn) 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 types of plastic for more info about which plastics are safe and unsafe.
However, remember, even though your plastic or stamp supplier may sell their clear plastic sleeves and envelopes with labels stating them as being mylar sheets, polyester film, mylar film, and/or PET film suitable for archival storage and display, the products should be labeled as being DuPont Mylar D, Melinex 516, or equivalent. With out such labeling, all bets are off as to safety.
So how long are you willing to wait before your rare stamps and their value is reduced by your use of harmful plastic stamp products?
If you are willing to wait, in a future post, I will be providing sources for DuPont Mylar© D, Melinex © 516 or equivalent plastic storage products. Stay tuned!