Hilary asks:
Can I use plastic bags to store collectibles?
We often think of plastic bags as being impervious to the elements and long-lasting. This is true to an extent, and the environmental impacts of plastics is a discussion for a different post. However, plastic bags are ubiquitous, and some are great for long-term storage of collectibles.
There are several types of plastic bags available, and while many may look similar to each other, materials and processing methods vary to produce results that behave very differently. For example, polyvinyl chloride (PVC) is a rigid material that’s used in myriad ways, including plumbing pipes, window and door frames, medical devices, shower curtains, flooring, toys, imitation leather, bottles, cable insulation, etc. It can also be used to make photo storage sleeves, but the materials that are added to PVC to make it soft and pliable (called plasticizers) off-gas volatile chemicals over time and cause harm to collection materials. Plasticizers can migrate to other plastic materials nearby, causing them to soften when they otherwise wouldn’t. And as plasticizers migrate out of their original application, the material left behind becomes increasingly brittle.
Because plastic bags are pliable, it can be difficult to know whether any given bag has additives in it. So reach for chemically stable (aka inert) materials, including:
- Archival polyester (PET), also called Mylar and Melinex.
- Polyester films are great for document and photo sleeves, and it also comes in larger sheets or rolls for encapsulating large items like posters and wrapping around items rolled onto tubes.
- Polyethylene (PE). This flexible, inert plastic is mostly transparent and is made into bags of all sizes, with and without zipper locks.
- Polypropylene (PP). Similar qualities to PE.
For the home collector, using the right storage materials is a great step to ensure your items last longer. We’re happy to help you locate suppliers of archival materials to use in your personal heritage projects!
More resources
Choosing Safe Plastics, Smithsonian National Postal Museum
Safe Plastics and Fabrics for Exhibit and Storage, National Park Service Conserve-O-Gram
Understanding Plastics for Preservation, Gaylord Archival
Library and Archives Preservation 