Gum

Stamps are a product of four factors-paper, printing, perfs and gum. The first three get alot of press. Gum, however, is usually only written about if it is present or if it has been fraudulently reapplied. Stamp gums were originally derived from gum Arabic, a extract of the Acacia tree. These trees are tapped like Maple trees are for their syrup, and the resulting gum has a variety of commercial applications including glue, as an important additive to inks (thus involving gum Arabic in two phases of stamp production) and even foods. In the early days of stamp production, gum was brushed onto the stamp paper with large brushes by hand, usually after the stamps were printed. The hand applied quality of the gum led to varying thickness on the back of the paper. These variations in the gum made the stamp paper expand and contract over time at differing rates due to humidity and temperature, and led the gum to crack and to damage the stamp paper that it was adhering to. Further, gum Arabic is an organic compound and is prone to bacteria and spoilage. These qualities are what make “original gum” on the pre 1890 issues so scarce. Collectors in this earliest period were advised to wash off the gum as being the only way to insure that their mint stamps would remain undamaged. The pervasiveness of air conditioning after WW II, and the advent of modern gums evenly applied by machine made gum more stable and led to the NH phenomenon that is the current collecting standard for modern stamps. But NH is largely a choice that technology has allowed as collectors in the older period really were doing the best by their stamps by washing off the adhesive. It is interesting to speculate what effect the latest technological advance- self stick adhesives- will do for gum collecting. These stamps are saved with an adhesive backing and so the term NH for them is an anachronism. As younger collectors (who only know self adhesives) mature, it will be interesting to see if they pay the same attention (and premiums) for NH that is paid today.