I have been collecting U.S. stamps since I was a kid. Early on I had to scratch and save to buy stamps or I traded with the other kids for what I needed. As the years passed I had several opportunities to purchase some good size collections. I kept what I needed and sold the rest. Within the last few years I am seeing more and more collections being made available through estates and estate sales and I have purchased a few of them. These are collections that people took a lifetime to assemble and now they are being passed on through their heirs. Unfortunately, many of these collections that should be in mint condition are far from it.
The issue is that many times the mint stamps in the collection are stuck together. This can happen no matter how they are packaged. Even unopened stamp kits from the post office are susceptible. This is usually caused from storing them in a high humidity environment such as an attic, basement or a non air conditioned house. Once mint stamps are stuck together, the collector value decreases. There are ways to separate them, but the results vary and they will never revert back to their original mint condition. The good news is that no matter when a U.S. stamp was minted it can always be used for postage.
The best way to store mint stamps is to put each in a mount that is specifically made for stamps. After that store them in a dry environment. In a later post I will discuss several ways to separate stamps that are stuck together.