Why Cards Warp, Fade or Stick, and How to Stop It

Most card damage in storage comes from three things: humidity, heat and light. Cards are paper, and the Library of Congress tells collectors to keep paper cool, fairly dry (about 35% relative humidity), stable, and out of light (Library of Congress). The grading company AGS gives a card-specific target of 68–72°F and 40–55% humidity (AGS). Here's how to spot each problem and fix the cause.

Problem, cause and fix

What you see	Likely cause	What to do
Cards curl or bow (warping)	Humidity and heat, especially cards in binders in hot rooms (AGS)	Move them to a climate-controlled room. Store upright in a box or in toploaders. Don't leave binders in a hot room.
Colors or autographs fading	Light. LOC says paper should get minimal light and no direct or intense light (LOC).	Keep boxes closed and away from windows. Display cards away from direct sun.
Sleeve sticking to the card, or shiny patches	Plastic can trap moisture. Archivists call the sticking and shiny marks ferrotyping. It's worse with high humidity and some softer plastics (NEDCC).	Lower the humidity. Use plain polypropylene, polyester or polyethylene sleeves, not vinyl.
Old binder pages yellowing, cards smelling of plastic	PVC (vinyl). NEDCC calls it chemically unstable and unacceptable for archival storage (NEDCC).	Move cards out of old vinyl pages. Look for pages labeled PVC-free.
Water spots, mildew, musty smell	Basement, garage or attic storage, where LOC warns of leaks and extremes (LOC)	Move cards to a main-floor closet. Keep boxes off the floor and away from radiators and vents.

A simple storage setup that works

Pick the room. A closet in the main living area, not the attic, garage or basement (LOC).
Buy a cheap hygrometer and check it in summer and winter. Aim for the 35–55% range the sources above recommend.
Use the right plastics. Penny sleeve, then toploader or one-touch for anything valuable. See penny sleeves vs toploaders vs one-touch.
Box or binder? Boxes are better for bulk and long-term storage; binders for display. See binder vs box.
Store boxes upright and don't stack heavy things on them.

Graded slabs are sealed plastic, but they still don't like heat or sun. Keep them in a slab box, upright, in the same kind of room. Long-term basics: how to store cards long term. Shipping cards? See the card shipping guide.

Sources (checked Oct 30, 2026): Library of Congress: care, handling and storage of works on paper, NEDCC: storage enclosures for photographic materials, AGS: how to store cards so they don't warp. The 35% figure is the Library of Congress guidance for paper; the 40–55% range is from AGS.

Shop cards from Mackey's Finest Collectibles, a Kokomo-area Indiana seller on eBay →
Owner's store: Mackey's Finest is owned by this site's owner, so we benefit from sales there.

Info may be outdated. Verify with the source.

Disclosure: some links may be affiliate links. We may earn a commission at no extra cost to you.