In philately, gum is the substance applied to the back of a postage 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. Close examination of the Penny Red, left, reveals a 148 in the margin, indicating that it was printed with plate #148. ... This 1974 stamp from Japan depicts a Class 8620 steam locomotive. ... Arabic gum Acacia tree Gum arabic, a natural gum also called gum acacia, is a substance that is taken from two sub-Saharan species of the acacia tree, Acacia senegal and Acacia seyal. ...

The use of gum was part of the original proposal by Rowland Hill, and has been universal from the beginning. There have been a number of stamp types that were issued ungummed, typically due to emergency situations when gum was not available, such as Italy in 1944, Cracow issue of Poland in 1919, Latvia in 1919. Other reasons have included lack of access to gum (the typewritten "Cowries" of 1895 Uganda), extreme tropical climate (1873 Curaçao and Suriname), and intent to sell only to collectors (as with the US "Farley's Follies" souvenir sheets of 1933). The manual gluing-on of postage is such an extreme consumption of time (and "time is money" to businesses with a lot of mail) that these situations are always temporary. This article is about the postal service pioneer. ... 1944 (MCMXLIV) was a leap year starting on Saturday (link will take you to calendar). ... Motto: none Voivodship Lesser Poland Municipal government Rada miasta Kraków Mayor Jacek Majchrowski Area 326,8 km² Population  - city  - urban  - density 757,500 (2004 est. ... 1919 (MCMXIX) was a common year starting on Wednesday (see link for calendar). ... 1919 (MCMXIX) was a common year starting on Wednesday (see link for calendar). ... Cowry or Cowrie (shell) Various species of Cowry from all over the world Cypraea caputserpensis, very common in intertidal rocky areas Cowry shells (also spelled cowrie), are marine snails of the genus Cypraea (family Cypraeidae), found chiefly in tropical regions, especially around the Maldives or the East Indies. ... 1895 was a common year starting on Tuesday (see link for calendar). ... 1873 was a common year starting on Wednesday (see link for calaber). ... Curaçao (pronounced [kurasão]) is an island in the southern part of the Caribbean Sea off the coast of Venezuela. ... Stamp collecting is the collecting of postage stamps and related objects, such as covers (envelopes or packages with stamps on them). ... ... 1933 (MCMXXXIII) was a common year starting on Sunday (link will take you to calendar). ...

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 pregummed paper. There have been a couple of historical instances where stamps were regummed after being perforated, but these were unusual situations. This pair of coil stamps clearly shows the pattern of perforation holes; also, on the left side of the pair, the stamp was torn, while on the right the perforations were cut with scissors or knife. ...

On early issues, gum was applied by hand, using a brush or roller, but in 1880 De La Rue 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, but a 1946 local issue by the town of Finsterwalde in Germany used an economy process where the back of the stamp had a regular pattern of circular bare patches. 1880 was a leap year starting on Thursday (see link for calendar). ... De La Rue is a British commercial printer and papermaker. ... 1946 (MCMXLVI) was a common year starting on Tuesday. ...

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. In Swiss stamps of the 1930s, Courvoisier 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. // Events and trends The 1930s were described as an abrupt shift to more radical lifestyles, as countries were struggling to find a solution to the global depression. ... A Courvoisier bottle Courvoisier is a type of cognac. ...

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:

• dextrine, produced by heating starch
• gum arabic or acacia gum, derived from the acacia plant
• glue, from gelatin, rarely seen on stamps
• polyvinyl alcohol (PVA)

In recent years, the use of self-adhesive stamps has become widespread. The first use was by Sierra Leone in 1964, and the United States tried it on a Christmas stamp of 1974, 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. Dextrins are a group of carbohydrates produced by the hydrolysis of starch. ... Starch is a complex carbohydrate which is insoluble in water. ... Arabic gum Acacia tree Gum arabic, a natural gum also called gum acacia, is a substance that is taken from two sub-Saharan species of the acacia tree, Acacia senegal and Acacia seyal. ... Gum arabic, a natural gum also called gum acacia, is a substance that is taken from two sub-Saharan species of the acacia tree, Acacia senegal and Acacia seyal. ... Species About 1,300; see List of Acacia species Acacia is a genus of shrubs and trees of Gondwanian origin belonging to the subfamily Mimosoideae of the Pea Family Fabaceae, first described from Africa by Linnaeus in 1773. ... Historically, glue only refers to protein colloid adhesives prepared from animal tissues, such as hide glue, bone glue, or fish glue. ... Gelatin (also gelatine) is a translucent brittle solid substance, colorless or slightly yellow, nearly tasteless and odorless, which is created by prolonged boiling of animal skin and connective tissue. ... This article needs to be wikified. ... Self-adhesive stamps were first issued in such tropical climates as Sierra Leone and Tonga in an attempt to avoid the sticking-together tendencies traditional water-activated stamps had in humid conditions. ... For the Nintendo 64 emulator, see 1964 (Emulator). ... Christmas is a holiday observed in much of the world on 25 December (or on 7 January in most Eastern Orthodox Churches). ... 1974 (MCMLXXIV) is a common year starting on Tuesday (click on link for calendar). ...

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" or "post office fresh", 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 was with the use of stamp hinges, 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 mint stamps are inevitably under suspicion of having been regummed, and a subfield of forensic philately is the detection of regummed stamps. A stamp album is a book, often loose-leafed (to allow for expansion), in which a collection of postage stamps may be stored and displayed. ... Stamp hinges are small, folded, rectangular pieces of paper coated with a mild gum, used to hold postage stamps onto the pages of a stamp album. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ...