Comic books should be stored properly because printing fades over time, and paper wrinkles and tears easily. The way you take care of your books is important to their longevity if you want to sell them later or just reread them someday. The difference between a comic book in mint condition and one in near-mint condition can be a single stain or crease, so handle your collectibles with care. Aside from physical damage, environmental damage from warm temperatures, bright light, and moisture are threats. Here’s the safest way to store them.
Place a cardboard backing behind a comic and insert them both into a clear cover called a sleeve or a bag. The best covers are Mylar D sleeves. There are also polyethylene and polypropylene sleeves, but change them every few years or so because they aren’t ideal for permanent storage. Always use acid-free cardboard backings. You can find these products individually or in packs of about 100 in any comic book store.
Seal your cover. Most people tape them closed, but when you remove the tape to open them, be sure the tape doesn’t stick to the comic book. If it does, the book could tear as you pull it out.
Place your sealed comics vertically in a long acid-free cardboard box with a lid. They’re the same types of boxes comic book stores put back issues in.
Beware of atmospheric dangers. Direct exposure to bright light, especially flourescent light, is dangerous because of radiation. Light damage isn’t sudden, but it can accelerate comic book deterioration over a long time because the ultraviolet radiation fades ink. Avoid places where fungus and mold grow because moist, warm air aren't good for your collection. Automobile exhaust can turn comic book paper yellow.
Unfortunately, comic books will eventually wear on their own because of how they’re composed. The ink used in their printing has acid that yellows the paper, which is often of lower quality to begin with. Older comics will have yellow, brittle pages with faded ink and color. Your goal is to prolong extreme deterioration for as long as possible, especially if you plan to sell your collection.