I have frequently been asked how to safely protect old postcards, and still be able to see and enjoy them. I have used clear polypropylene display pages for several years to protect my personal Des Moines collecton of vintage postcards. Polypropylene is a heat-resistant, chemically stable plastic with a superior vapor barrier and crystal clarity! It is completely recyclable and ecologically friendly. Polypropylene is considered an archival safe material by the Library of Congress. Great for short and long term storage of postcards.
If you use other display pages, make sure they are archival, acid-free, and contain no PVC. And whatever you use, remove your postcards from old postcard albums where the pages look like black or green construction paper. The acid in the paper will eventually damage your cards (if they haven't already) and the slots will damage your corners.
BCW Magazine Backing Boards/Envelope Stiffeners are made from a full 24 point solid bleached sulfate, certified Acid Free!
Note from Ron Playle: Although these were made primarily as magazine backing boards, we use them as protection to mail small quantities of postcards! We cut them into two 5-1/2" x 8-1/2" pieces and use them for envelope stiffeners in 6" x 9" brown kraft 28lb envelopes. They can also be cut into three pieces and used in size #10 envelopes.