This is a very good trick! I purchased some mint stamps on eBay some years ago, ones that I particularly wanted and which I found quite hard to get. The stamps were from the early 20th century, ranging from about 1920 to 1930. I paid over $500 for them so I was disappointed to find that, when they arrived, the majority were stuck together, overlapped one on top of the other. However, I was very keen to keep them and I started to look around for ways to "unstick" them. You have to understand that the stamps were never subjected to immersion in water - they had presumably been left in a humid environment and became stuck over time. Since they were mint and I wished to retain them in that condition, I could not soak them. That would have solved the problem at one level, but the stamps would no longer have been classified as true mint copies, because the gum would have been missing. I tried: freezing... which actually worked to a small extent. However, the majority failed to react to this process. They were well and truly stuck. I tried: steaming... but this quickly proved too hazardous. There was a strong risk of "melting" the gum, as it were, and as I tried to pry them apart, it was clear that some damage was being done to the bottom stamp. I tried: heating... by putting them near an electric heater. They never even looked like reacting to this process. Finally, I tried putting them in a humid environment and low and behold it worked. Here is how it is done. Take two large sponges, capable of holding a fair amount of water. The ones I used were each about 6 inches (15 cm) by 3 inches (7.5 cm) and 2 inches (6 cm) thick. Soak them both thoroughly and, once properly wet, wring them out so that there is no actual water left on surface. The sponges should still be very humid. You do not want any water collecting anywhere near the stamps. Then carefully place the stamps (mine were stuck in groups of 8, 9 or 10 (all lined up in a row, so that one part of each stamp overlapped part of the next stamp) gum side down on top of one sponge and place the other sponge on top (do not apply any pressure). After 15 minutes or so, you should find the gum has become "loose" enough to pry the stamps apart without damaging them. Obviously, you may need to adjust parts of this process (more or less water in the sponges; time left in the humid environment, etc.,) to your own needs. Also, some gums may react differently. However, after months of trying this and that method to get these stamps apart, I found that this method not only worked, but it was very efficient indeed. I was able to save what I considered to be a valuable colection of older mint stamps and now have them on display in an album, which hitherto had been impossible.