Before the widespread use of self-adhesive stamps, an afternoon of soaking stamps off their paper was a pleasant, relaxing experience because the glue on the back of the stamps was water-soluble. Now, with lick-and-stick stamps all but gone, that stamp soaking session can turn into an exercise in frustration. Because the Postal Service uses multiple printers and does not include the adhesive in its specs, knowing which self-adhesive stamps soak off easily and which won't come off the paper without being ruined is a crap shoot.
Remove stamps from envelopes, leaving a 1/2-inch to 1-inch border of paper around the stamp.
Sort stamps by gum type. Water-soluble stamps are likely to be from 2000 or earlier, and the perforations on the sides are rounded indentations. Self-adhesive stamps' "perforations" vary in shape.
Sort out any stamps on envelope paper colours other than white. Red paper can bleed into the water and turn all the stamps in the pan pinkish; stamps on cardboard can take a long time to soak off, if corrugated; and stamps that came on envelopes filled with recycled newsprint in the inside should also be done separately. They're a mess.
Fill a shallow pan, such as a pie plate, grill pan or 9-by-13-inch pan, with warm water for water-soluble stamps and hot water for self-adhesives. Boiling water will fade them, however.
Place a single layer of one type of stamp in the pan.
Stir the stamps in the water. Use the stamp tongs to pick up lick-and-stick stamps that have floated free, and move them to a paper towel, face down. Some stamps may need to have their paper gently lifted off. Self-adhesive stamps may not come off the paper at all, no matter how long they sit there. Some may come off the paper but retain their glue. Don't fuss with them until at least five minutes have passed. If you have to tug at the paper, the front will likely crack.
Blot the freed stamps with a piece of paper towel.
Move the stamps, face up, to a glossy drying book page. Work back to front in the book. When a page is full, prevent stamps from curling by lowering the next page on top.
Close the drying book, and place a heavy book on top of it until tomorrow, when your stamps will be crisp, flat and ready to archive in an album or storage envelope.
If self-adhesive stamps do not come off in very hot water after, say, 10 minutes, you're better off just drying them, trimming around them neatly and mounting them in your album. Even if they do come off after that long, they may curl and the ink may crack. After 10 minutes your water will likely be getting cold anyway. If you have several of one self-adhesive issue, soak a damaged or low-quality "tester" to see how long it takes to come off the paper and whether it comes off without damage. Soak self-adhesives in deep pans so that the water doesn't turn cold quickly. Sort stamps also by denomination and look them up (see Resources) before soaking to see if it's worth your while.
For many self-adhesive stamps, it's just less of a headache to neatly trim them off the envelope and mount them that way, especially if their colours are dark or gold. Any crinkles or flaws will be prominent--and ugly. Don't bother soaking off self-adhesives from Brazil or Italy, and machine-printed stamp labels from countries such as Spain and France just don't come off the paper. Stamps mounted on glossy paper or bubble envelopes will take longer to soak.