I'm a volunteer archivist, and I've had to educate myself about plastics. The chloride in Poly-vinyl-chloride (#3) is chlorine. PVC is constantly off-gassing chlorine and it's very corrosive. It's damaging to coins, stamps, baseball cards, family photos, and anything else you store in those clear plastic pocket-pages and page protectors. The manufacturers have realized this and are now making them out of Polypropylene (#5), and they're finally labeling the package with the type of plastic. If it's not labeled, contact the manufacturer and ask what it's made of. Most of what I'm finding in office supply stores these days is #5, but there might still be some #3 for sale in some of the bargain shops. The National Park Service has a great collection of publications called "Conserv-o-grams" that you can access on line, including a good one on archivally stable plastics. For safe storage you want Polypropylene, and if you can't get that, go for Polyethylene (#2 or #4). If I've made any mistakes here, someone please let me know.
I'm a volunteer archivist, and I've had to educate myself about plastics. The chloride in Poly-vinyl-chloride (#3) is chlorine. PVC is constantly off-gassing chlorine and it's very corrosive. It's damaging to coins, stamps, baseball cards, family photos, and anything else you store in those clear plastic pocket-pages and page protectors. The manufacturers have realized this and are now making them out of Polypropylene (#5), and they're finally labeling the package with the type of plastic. If it's not labeled, contact the manufacturer and ask what it's made of. Most of what I'm finding in office supply stores these days is #5, but there might still be some #3 for sale in some of the bargain shops. The National Park Service has a great collection of publications called "Conserv-o-grams" that you can access on line, including a good one on archivally stable plastics. For safe storage you want Polypropylene, and if you can't get that, go for Polyethylene (#2 or #4). If I've made any mistakes here, someone please let me know.