The rubber is placed on the face behind the vignette, and is moistened to attach the stamp to the object to be forwarded by mail.
Not all stamps have rubber. Of course, they no longer have stamps that have been removed from the envelope after a special bath in water and then those that have been issued from the beginning without. In yarn, new stamps with rubber are distinguished from those with a lattice track.
The tab is a small strip of paper gummed of pergamino that is applied by the collector to the direction of the stamp to make it adhere to a page of the album.
This is a practice that is now deferred as the presence of a tabloid on the stamp causes a depreciation of more than half the value.
For this reason, sometimes, in order to make the trace of the tabloid disappear from the back of the stamp, some people devoid of scruples, carry out the filling of the stamp to sell it at a greater price. This technique consists in laying a new layer of rubber on the back of the stamp.
The simplest method to notice the rigommature is to gently pass a finger along the knives: generally these are harder and stiffer than the dentelli of an unregulated stamp. Another safer technique is to observe in the dark with a Wood lamp the direction of the stamp.
In case of doubt, it is better to get the specimen from a legally recognized philatelic expert.
There are various types of rubber: polished, smooth, matte and codronata. The glossy tires are the ones that are most prone to cracking. Rubber is often of animal origin and therefore subject to the formation of microorganisms such as molds, capable of ruining the stamp.
Many postal administrations have long completed studies aimed at replacing natural rubbers with modern synthetic adhesives suitable for solving the problem of conservation. One of the first measures was to mix a percentage of glycerin to the arabic gum.
In 1962, France promoted a curious experiment and issued a stamp dedicated to the beach of Le Touquet-Paris which had a mint-flavored rubber.