How not to store coins
One main objective of coin storage is the prevention of coin-to-coin contact. Another issue is the preservation of luster. Air is one of the enemies of luster. Air oxidizes the surface of the coins, causing them to appear dull. A brilliant freshly minted Lincoln cent that is allowed to sit on a table will be noticeably duller within a few months. To keep coins away from air, many people put coins in paper envelopes. This is even worse. The sulfur content in the paper will dull the coins rapidly.
Avoiding PVC coin holdersMany coins are sold in 2x2 plastic flips. These flips protect the coins from hitting other coins and they keep the coins out of the air. A major problem is that many of these holders are made of PVC (polyvinyl chloride) plastic, commonly referred to as vinyl. PVC plastic releases hazardous chemicals. The characteristic smell of a new car or new shower curtains is actually hazardous bi-products released from the vinyl. The breathing of these bi-products has been linked to cancer. The PVC flips are also hazardous to the luster of the coin. A coin in a PVC flip undergoes a slower death than one in a paper envelope. However, the PVC flips do damage coins. If a coin in a PVC flip is stored in a hot environment, the damage will occur faster. Coins can be safely stored in non-PVC flips, which look nearly identical and are made of a harder plastic. Coin holders made of mylar are fine.
My favorite coin albyums are the type where the coins are covered with a hard plastic strip. When sliding the strip across the pages, it is important to avoid scratching the surfaces of the coins. Among my favorite brands are the Dansco Albums. Coin folders are also popular. Unfortunately, the coins frequently fall out when opened. The folder type albums leave the front of each coin exposed. The back of each coin presses against a paper backing, which could cause sulfur damage to the coin.