Let's discuss the 5 Proven Ways to Keep Your Rare Trading Cards in Mint Condition.
Most collectors don't lose card value in dramatic accidents. They lose it slowly - a scratch here, a humidity warp there, edge wear from pulling cards in and out of loose sleeves. PSA mentions that even micro-scratches that can't be seen without magnification can reduce the quality of a card from being a Gem Mint 10 to a Near-Mint 7, subsequently reducing its value by 50% or more. This situation can almost always be avoided.
Using a single sleeve doesn't provide complete protection from dust, friction, and moisture. Your card is still likely to be exposed to all three of those issues. Dust spilling from the top could get on your card if it's disturbed. Friction could work on the inside of the sleeve and edge of the card. If it's nudged near some water, a drink, or a melting popsicle or something, you're out of luck on the moisture front. Double sleeving mostly covers all these issues. The card is inserted into a perfect fit inner sleeve with the opening downward. The perfect fit innersleeved card is inserted into the outer sleeve with the opening upward. The offset holes are on opposing sides.
Issues with the perfect fit are that it is "snug". Cards can be inadvertently "dragged" and "lifted" and even bent inwards with the inner sleeve. But, the perfect inner's snugness is its strength as it has the card truly. No real room to move therefore. Dust is blocked way better. Card is blocked from all sides and top except for small openings. Those small openings can be a small point of contention between inner and outer sleeve. They are also slightly off centered which means when liquid is leaning on cards it wouldn't reach most of the opening. Friction on both sides is also contested so they can cancel each other out. Another potential issue is perfect fitting sleeves are hard to get into depending on factory level of precision for the card in question. Best innersleeve material is polypropylene over pvc. The latter leeches whereas the former is chemically neutral.
External covers are available in solid shades, and they're more helpful than you think. The use of color to separate sets, rarities, or deck types means that you won't need to dig through a box or binder in search of a specific card - you already know that the yellow covers are holos, and the black ones cover your standard rares. For collectors who find sleeve providers with extensive color options, this type of technique truly allows large collections to be navigated without handling cards over and over. Any handling event that is not needed is a friction danger. The less you handle your cards, the better you preserve them.
Playing cards can absorb or release moisture from the air. If the humidity level is not right, the cards may become warped. Cards with a foil finish are particularly prone to this warping. Warped cards can cause the "Pringle effect", meaning that the cards will warp along their length.
The humidity range you're aiming for is 45-55%. If the relative humidity drops below 40%, the cards will dry out and become fragile. If the humidity level rises above 60%, you run the risk of warping and in extreme cases, mold. A small digital hygrometer can be purchased for very little and will give you a precise read on the humidity level in your storage area.
For long-term storage, put a couple of silica gel packets in air-tight boxes with your cards. The packets will help soak up excess moisture and keep the micro-environment inside the box stable, even if the humidity level outside the box isn't. Remember to replace the packets every few months.
UV radiation is present in sunlight and fluorescent light. Ink pigments are degraded at the molecular level by UV. The colors do not instantly vanish, but rather shift and become dull over time. A good grader can easily detect this shift.
Side-loading binder pages are preferable to top-loading binder pages. In the former, cards are nestled comfortably with less room for movement during transport or regular handling. In the latter, card pockets are open at the top and cards aren't fully enclosed, making them more likely to shift and move downwards when being carried or flipped. This can cause the edge of the card to repeatedly bump against the bottom of the pocket, resulting in slight wear and tear that can be avoided if the card was properly encapsulated.
Similarly, if you're packing your binder too tight or your binder rings are too close to the pockets, the sides of your cards may be exposed to constant pressure from the rings, causing slight indentations over time. Leave a buffer of a free sheet of paper or two in the front and back of the binder to guard against this.
The oils and salts on your skin can etch into the card surface over time. It's not something you'll necessarily notice day-to-day, but it's painfully apparent when you crack open a graded card and realize it wasn't gem mint material. For expensive cards, avoid touching them at all costs, wash and dry your hands before handling, or use microfiber gloves and touch only the edges of the card.
