Vintage baseball cards require special care and storage methods to preserve them in the best condition possible. The key things to focus on are avoiding bends, creases, moisture, and heat exposure which can all damage cards over time.

The best way to store vintage cards is in plastic sheets inserted into cardboard card storage boxes. Look for acid-free and PVC-free sheets and boards. Acidic materials can cause deterioration of the paper and ink over decades. Opt for polypropylene sheets which are very durable and will not damage the cards. 9-pocket pages are ideal for common cards, while higher end cards can be stored individually in plastic sleeves cut to size.

Make sure to use sturdy corrugated cardboard boxes for storage. Do not use flimsy cardboard that can bend and crush under uneven weight distribution. The boxes should fit the pages/sleeves tightly but not so tight that removing cards is difficult. Leave a small amount of slack for expansion/contraction with temperature changes. Boxes stored upright on their ends are less prone to crushing from weight.

control of temperature and humidity is very important long term. Fluctuations can cause warping, sticking and faded colors. A cool, dark and dry location away from direct sunlight, heat sources and leaks/pipes is ideal. Target a consistent 65-70 degrees F and 45-55% relative humidity if possible. Warmer and more humid areas are to be avoided. If temperatures will exceed 80 degrees or drop below 50, additional measures may be needed.

To maintain humidity control, include a humidity indicator card in the box to monitor levels. Do not use silica gel packs as they can leave a powder residue on the cards over decades. For short term fluctuations, some collectors will include wrapped (taped) cotton balls in storage boxes, which can absorb/release small amounts of moisture as needed.

When handling cards, always wash hands thoroughly to remove oils before touching them. Oils from fingers can permeate the paper and cause damage apparent years later. Wear clean cotton gloves if needed for added protection. Admire cards by sliding them out of pockets/sleeves rather than grasping them directly with fingers.

Inspect cards periodically for signs of damage from improper storage conditions – warped/creased edges, sticky surfaces, faded/weakened colors are all signs changes may be needed. Loosen tight plastic if creasing occurs. Also check for signs of mold or insect infestation which requires cleaning/treatment or disposal of infected cards.

For long term preservation, consider having valuable vintage cards stored in climate controlled safety deposit boxes. Banks maintain steady temperature and humidity levels year round. Some collectors also place cards in climate controlled closets or plastic archival storage boxes. Proper materials and monitoring are still required in any long term storage solution.

With the proper protective plastic page/sheet inserts, sturdy storage boxes, environmental control and careful handling, vintage baseball cards can maintain their condition for decades of enjoyment. Taking proactive steps to avoid threats like temperature fluctuations, moisture problems and physical damage helps preserve these treasured collectibles for future generations of fans. Frequent inspection allows for quick response to any emerging preservation issues as well.