Postage stamp gum
In philately
Philately is the study of stamps and postal history and other related items. Philately involves more than just stamp collecting, which does not necessarily involve the study of stamps. It is possible to be a philatelist without owning any stamps...

, 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. Gum is a matter of high importance in philately.


The use of gum was part of the original proposal by Rowland Hill
Rowland Hill (postal reformer)
Sir Rowland Hill KCB, FRS was an English teacher, inventor and social reformer. He campaigned for a comprehensive reform of the postal system, based on the concept of penny postage and his solution of prepayment, facilitating the safe, speedy and cheap transfer of letters...

, and most stamps have been gummed. Many early stamps were not gummed, however, and some have been unable to be gummed due to shortages, for instance the typewritten Uganda Cowry stamps of 1895. Extreme tropical climates were also a problem for Curaçao and Suriname. Some stamps, intended only for sale to stamp collectors have been issued without gum, for instance the United States Farley's Follies souvenir sheets of 1933. On the first stamps of Great Britain the gum was called cement and was made from a mixture of potato starch
Potato starch
Potato starch is starch extracted from potatoes. The cells of the root tubers of the potato plant contain starch grains . To extract the starch, the potatoes are crushed; the starch grains are released from the destroyed cells...

, wheat starch and acacia gum.

Types and application

Originally, gumming took place after printing and before perforation, usually because the paper had to be damp for printing to work well, but in modern times most stamp printing is done dry on pre-gummed paper. There have been a couple of historical instances where stamps were regummed after being perforated, but these were unusual situations.

On early issues, gum was applied by hand, using a brush or roller, but in 1880 De La Rue
De La Rue
De La Rue plc is a British security printing, papermaking and cash handling systems company headquartered in Basingstoke, Hampshire. It also has a factory on the Team Valley Trading Estate, Gateshead, and other facilities at Loughton, Essex and Bathford, Somerset...

 came up with a machine gumming process using a printing press, and gum is now always applied by machine. The gum is universally spread as uniformly as possible.

The greatest manufacturing problem of the gumming process is its tendency to make the stamps curl, due to the different reaction of paper and gum to varying moisture levels. In the most extreme cases, the stamp will spontaneously roll up into a small tube. Various schemes have been tried, but the problem persists to this day. On Swiss stamps of the 1930s, Courvoisier
Courvoisier is a brand of cognac owned by Beam Inc.. The production is now based in the town of Jarnac in the Charente department of France...

 used a gum-breaking machine that pressed a pattern of small squares into the gum, resulting in so-called grilled gum. Another scheme has been to slice the gum with knives after it has been applied. In some cases the gum solves the problem itself by becoming "crackly" when it dries.

The appearance of the gum varies with the type and method of application, and may range from nearly invisible to dark brown globs. Types of gum used on stamps include:
  • dextrin
    Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch or glycogen. Dextrins are mixtures of polymers of D-glucose units linked by α- or α- glycosidic bonds....

    , produced by heating starch
    Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

  • gum arabic
    Gum arabic
    220px|thumb|right|Acacia gumGum arabic, also known as acacia gum, chaar gund, char goond, or meska, is a natural gum made of hardened sap taken from two species of the acacia tree; Acacia senegal and Acacia seyal...

     or acacia gum, derived from the acacia
    Acacia is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, first described in Africa by the Swedish botanist Carl Linnaeus in 1773. Many non-Australian species tend to be thorny, whereas the majority of Australian acacias are not...

  • glue
    Hoof glue
    Hoof glue is an adhesive made by boiling down the hooves of ungulates. It is a partially hydrolyzed keratin. It is a type of animal glue.- History :...

    , from gelatin
    Gelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...

    , rarely seen on stamps
  • polyvinyl alcohol
    Polyvinyl alcohol
    Polyvinyl alcohol is a water-soluble synthetic polymer .-Properties:...


Some stamps have had gum applied in a pattern resembling a watermark
A watermark is a recognizable image or pattern in paper that appears as various shades of lightness/darkness when viewed by transmitted light , caused by thickness or density variations in the paper...

, presumably as an additional security device. German stamps from 1921 had a pattern of wavy lines while Czech stamps from 1923 had gum showing the initials of the Czech Republic, CSP. These patterns have been called gum devices or gum watermarks.

Self-adhesive stamps

In recent years, the use of self-adhesive stamp
Self-adhesive stamp
A self-adhesive stamp is a postage stamp with a pressure sensitive adhesive that does not require moistening in order to adhere to paper. They are usually issued on a removable backing paper....

s has become widespread. The first use was by Sierra Leone in 1964, and the United States tried it on a 1974 Christmas stamp, although the experiment was judged a failure and not repeated for many years. Traditional gums remain in use, although differentiated by calling them water-activated. All Israeli postage stamps feature a water-activated adhesive that is certified Kosher.


For collectors, gum is mostly a problem. It is rarely of use in differentiating between common and rare stamps, and being on the back of the stamp it is not usually visible. Nevertheless, many collectors of unused stamps want copies that are mint, never hinged which means that the gum must be pristine and intact, and they will pay a premium for these. While not so much of a problem for modern issues, the traditional way of mounting stamps in an album
Stamp album
A stamp album is a book, often loose-leafed , in which a collection of postage stamps may be stored and displayed.- Overview :...

 was with the use of stamp hinge
Stamp hinge
In philately stamp hinges or mounts are small, folded, transparent, rectangular pieces of paper coated with a mild gum. They are used by stamp collectors to affix postage stamps onto the pages of a stamp album.- Use :...

s, and some experts claim that very few unused stamps from the 19th century have not been hinged at some point in their existence. This means that old unused stamps are inevitably under suspicion of having been regummed, and the detection of regummed stamp
Regummed stamp
In philately a regummed stamp is an unused stamp without gum, or without full gum, that has had new gum applied to the back to increase its value....

s is an important part of philatelic expertisation
Philatelic expertisation
Philatelic expertisation is the process whereby an expert is asked to give an opinion whether a philatelic item is genuine and whether it has been repaired or altered in any way....


Stamps printed on the gummed side by mistake have become valuable varieties.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.