Choosing Safe Plastics

Encapsulating a sheet of stamps in polyester film for exhibition
Encapsulating a sheet of stamps in polyester film for exhibition

The word “archival” has become one of those terms used to sell products and make consumers feel safe. But with no regulations to control or define what constitutes an archival product, consumers must educate themselves.

If you are interested in using a plastic enclosure for housing or mounting your collection, ask the company or sales representatives about the chemical properties of their products. Look for plastic that is polyester, polyethylene or polypropylene. If you do not receive concise answers, move on to a different company.

Philatelic catalogs often reference ‘safe vinyl’ when referring to their enclosures, implying that it will not react with your collections. Often listed as polyvinyl chloride or PVC, vinyl is neither safe nor stable and is highly reactive. This reaction will, over time, cause permanent damage to the material in the enclosure.

When looking for quality enclosures for photographs or film, see if the material has passed the Photographic Activity Test or is marked “PAT Passed”. This standard is developed by the Image Permanence Institute. Products must pass a series of rigorous testing to ensure their long term stability and preservation standards.

Enclosures for philatelic or paper collections should be made from an inert, clear plastic made of Polyester Film, Polyethylene or Polypropylene. “Inert” means chemically stable which indicates it will not react with other materials.

Polyester film includes Melinex ®, formerly known as Mylar. To store or display philatelic material, use a film with a thickness of 3 to 4 mil. These same materials are used by the museum for exhibitions and storage of the collections because it is transparent and therefore works well in albums and other types of displays.

Polyethylene is a softer, clear plastic, but not as clear as the polyester film. It is not as structurally sound as polyester or polypropylene, so it’s recommended to never fully seal up objects in this type of plastic.

Polypropylene is similar to polyester film in clarity. It is also used as sleeves for storing photographs, papers and philatelic material. The museum often uses polypropylene page protectors for album pages when rehousing a collection.

Philatelists are one of the largest collecting groups worldwide and numerous companies are in the business of supplying them with products for the display and storage of their prized collections. Spend the time to research different companies (not just those specializing in philatelic supplies) and to review their catalogs to become an informed consumer.

Before selecting a plastic enclosure, ask for some samples or order a small quantity. Experiment. Find the product that will work best with your personal collecting needs. Once you have found a reliable source for display and storage products, the rewards will be well worth your time and effort.

For More Information: Conserve O Gram: “Safe Plastics And Fabrics For Exhibit And Storage”