Has Your Stamp Been Regummed? – The Philatelic Foundation
To make the removal job easier, the stamp is put into a very damp environment where the gum on the stamp is actually liquefied, that is, made completely liquid or melted, just as it was when first applied. Hinge remnants can then be lifted right off the stamp without damaging it. By taking a fine brush and redistributing the remaining gum, the traces of previous hinging can be hidden from all but the most expert eye. The gum here is most certainly original – nothing has been added – but the state of the gum is most definitely changed from its original condition.
Gum skips are quite natural and exist on most of the older U.S. stamps. These stamps are often
filled in or erased when original gum is redistributed. It becomes important to know typical gum for any particular issue of stamps.
Most of the stamps that the collector will encounter will not be regummed. But some will be, and the collector should know enough to protect himself. There is often little difference between a stamp with redistributed original gum and one that has been regummed. This is not unusual as the basic processes differ very little. A stamp having hinge remnants removed may have additional gum added to the liquefied original gum. If the job is done well, it may be extremely difficult to tell, even for an expert. Fortunately, most are not so difficult.