What are the relative advantages and disadvantages of using plastic enclosures to protect photographic materials?

Plastic enclosures have the great advantage of allowing an image to be viewed without removal from the enclosure, greatly reducing the changes of abrading, scratching, or fingerprinting the photograph.

Plastic enclosures seal the object from the atmosphere. Since most chemical deterioration in a photograph is catalyzed by the presence of moisture and sulfides in air, such protection may prolong the life of the image. However, plastic enclosures can trap moisture and cause ferrotyping (sticking, with resulting shiny area) of the image under extreme conditions.

Plastic enclosures of archival quality may be made of polyester, polypropylene, or polyethylene. Polyester is the most inert, dimensionally stable, and rigid of the three. However, It can generate static electricity which attracts dust, and it is very expensive. Polyester enclosures should be either Dupont Mylar D® or ICI Melinex #516®. Polypropylene is almost as rigid as polyester when it is the untreated "oriented" polypropylene used in many sleeve formats, but is softer when it is the surface-treated polypropylene used for ring binder storage pages. Polypropylene enclosures perhaps provide the best balance of safety and affordability, while maintaining excellent presentation benefits. Low Density Polyethylene (LDPE) has a more translucent clarity and was originally used in many ring binder storage pages. LDPE pages are still the first choice of many, but it is the most easily marred, and least rigid of these archival plastics. High-density polyethylene (HDPE) is a very translucent, milky plastic which is naturally slippery and is generally used for the low cost sleeving on rolls provided by large photo processors.

It is our opinion that plastic enclosures made from polyvinylchloride (PVC) should be avoided for archival photographic storage. This plastic, often-referred to as "vinyl" by suppliers, can be chemically unstable and may cause deterioration of a photograph over time. Beware of suppliers that avoid telling you exactly which plastics have been used to produce their "archival" pages and sleeving.