Postage stamp gum
In philately, gum is the substance applied to the back of a stamp to enable it to adhere to a letter or other mailed item.
The term is generic, and applies both to traditional types such as gum arabic and to synthetic modern formulations.
The appearance of the gum varies with the type and method of application, and may range from nearly invisible to dark brown globs.
[5] Due to shortages of material, such as in the situation following World War II in Germany, stamps may be gummed in an economy fashion.
[7] The first use was by Sierra Leone in 1964,[8] and the United States tried it later on a 1974 Christmas stamp; this was judged a failure and was not reintroduced until 1989 when it gradually became widespread.
The authors added the warning that "postage stamps are often handled very carelessly when issued over the counter, and yet the purchaser will usually lick them without hesitation.
The present work shows how readily bacteria can adhere to the surface of gummed paper which has been slightly moistened; and the finger is a suitable source both of moisture and of bacterial contamination.
"[10] A 1996 episode of the popular sitcom Seinfeld featured a character (Susan Ross) who was poisoned after licking the flap of too many gummed envelopes.
The episode has been linked anecdotally to an increase in worries about the health risks of licking gummed paper and it has been speculated that it may have contributed to the growing popularity of self-adhesive stamps, at least in the United States.
[citation needed] Stamps printed on the gummed side by mistake are sought after by collectors with an interest in uncommon varieties.
[citation needed] Care must be taken during production that stamp gum, in particular if prepared from natural materials, does not contain an excess of acid.
Notable cases are the Ostropa commemorative sheet issued in Germany in 1935, and the German Zeppelin airmail stamps of 1936.
[citation needed] The thick gum on some older stamps, namely on issues of Austria-Hungary, tends to break due to changes in air humidity and temperature.
