![Stamp GB 1959 4&half pence tagged Wilding](https://upload.wikimedia.org/wikipedia/commons/d/df/Stamp_GB_1959_4%26half_pence_tagged_Wilding.jpg)
Tagging of
postage stamp
A postage stamp is a small piece of paper issued by a post office, postal administration, or other authorized vendors to customers who pay postage (the cost involved in moving, insuring, or registering mail), who then affix the stamp to the f ...
s means that the stamps are printed on
luminescent
Luminescence is spontaneous emission of light by a substance not resulting from heat; or "cold light".
It is thus a form of cold-body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions or stress on a crystal ...
paper or with luminescent ink to facilitate
automated mail processing. Both
fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
and
phosphorescence
Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluo ...
are used. The same stamp may have been printed with and without these luminescent features, the two varieties are referred to as ''tagged'' and ''untagged'', respectively.
Technology
Letter
Letter, letters, or literature may refer to:
Characters typeface
* Letter (alphabet), a character representing one or more of the sounds used in speech; any of the symbols of an alphabet.
* Letterform, the graphic form of a letter of the alphabe ...
s and
postcard
A postcard or post card is a piece of thick paper or thin cardboard, typically rectangular, intended for writing and mailing without an envelope. Non-rectangular shapes may also be used but are rare. There are novelty exceptions, such as wood ...
s fed into an automated mail processing plant are illuminated with
ultraviolet light
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
. The reaction of the luminescent features of the stamps on this illumination is used to position the mail items such that the stamps can be
cancelled, and that the significant parts of the address such as
postcodes may be read and the mail be sorted accordingly.
The luminescent features of the stamps are generally invisible or barely visible to the human eye in normal illumination. They can, however, be identified under ultraviolet light similar to the way it is done in the postal machinery. In general, fluorescent features can be identified with UV light of a longer wavelength than needed for phosphorescent features (see below).
The luminescent substance ("taggant") can be printed over the whole surface of the stamp, the main design, the margins only, single bands or bars or other patterns, or can be added the paper itself.
The tagging pattern can also be varied to enable sorting of mail according to the service class.
Methods and detection
Fluorescence
Upon absorption of light, fluorescent materials emit light upon of a longer wavelength (lower energy) than the absorbed radiation, but cease to do so once immediately, when the illumination is stopped. The tagging of stamps uses substances that absorb ultraviolet light of wavelengths between 300 nm and 450 nm ("
Black light", UVA, long-wave UV) and emit light in the visible spectrum. Under UV illumination they usually glow a greenish or yellowish colour.
It must not be confused with the "whitening" of paper
which is achieved by adding
optical brightener
Optical brighteners, optical brightening agents (OBAs), fluorescent brightening agents (FBAs), or fluorescent whitening agents (FWAs), are chemical compounds that absorb light in the ultraviolet and violet region (usually 340-370 nm) of the ...
s that usually re-emit light in the blue region of the spectrum, making the paper appear whiter by compensating a perceived deficit in reflected colours of these wavelengths.
Phosphorescence
Phosphorescent materials release the absorbed energy only slowly, so that they exhibit an "afterglow". Materials for stamp tagging absorb ultraviolet light of wavelengths between 180 nm and 300 nm (UVC, short-wave UV) and emit light of a greenish or reddish colour depending on the substances used.
Detection equipment
![Portable black light fluorescent lamp](https://upload.wikimedia.org/wikipedia/commons/e/ec/Portable_black_light_fluorescent_lamp.jpg)
Fluorescent stamps can be detected with a black light
fluorescent tube. Phosphorescent stamps can be detected using a shortwave UV lamp. The effects of both processes can be recorded photographically. Lamps for both ranges of wavelengths as well as combinations of both are available. Care must be taken when using UV lamps, since their light can damage the eyes.
Application in various countries
Canada
The first tagged stamps of Canada were issued in 1962 with vertical phosphorescent bands. In 1972, fluorescent ''general tagging'' was introduced, initially as vertical bars, now normally on all four sides of the stamp.
Germany
Deutsche Bundespost
The Deutsche Bundespost (German federal post office) was a German state-run postal service and telecommunications business founded in 1947. It was initially the second largest federal employer during its time. After staff reductions in the 19 ...
started issuing stamps on fluorescent ''Lumogen'' paper in 1960 in connection with trials for automated mail processing in the Darmstadt area. Fluorescent paper was generally used for stamps of Deutsche Bundespost and
Deutsche Bundespost Berlin
The Deutsche Bundespost Berlin (German Federal Mail of Berlin) was the name used on the stamps of West Berlin. It sounds similar to the name of the Western German postal services Deutsche Bundespost and was ''de facto'' a dependency of it. ''De ju ...
from 1961 on.
Deutsche Post AG
Deutsche Post AG, trading as Deutsche Post DHL Group, is a German multinational package delivery and supply chain management company headquartered in Bonn, Germany. It is one of the world's largest courier companies. The postal division delive ...
continues to use this technology.
Deutsche Post of the GDR
The Deutsche Post (''DP''), also Deutsche Post of the GDR (''German: Deutsche Post der DDR'') was the state-owned postal and telecommunications monopoly of the German Democratic Republic (GDR - East Germany). The DP was placed under the control o ...
did not use luminescent tagging on stamps.
United Kingdom
Luminescent tagging has been added to
postage stamps of the United Kingdom
Postage stamps and postal history of Great Britain surveys postal history from the United Kingdom and the postage stamps issued by that country and its various historical territories until the present day.
The postal history of the United Kingd ...
since the
Wilding issues of 1959 in the shape of vertical bands. Stamps of the current
Machin series have been printed with one or two such "phosphor bands",.
those for second-class mail bear only one such band, those for first-class mail bear two. The positions of the bands may vary, stamps from
booklet
Booklet may refer to:
* A small book or group of pages
* A pamphlet
* A type of tablet computer
* Postage stamp booklet, made up of one or more small panes of postage stamps in a cardboard cover
* Liner notes, writings found in booklets which come ...
s may have shortened, notched, or inset bands that do not extend onto neighbouring
gutters to avoid the use of the latter instead of stamps for franking.
Due to the presence of optical brighteners in many printing papers, phosphorescent materials were chosen for stamp tagging in the UK.
United States
The US Post Office Department started experiments with fluorescent compounds in the early 1960s. An 8¢ air mail stamp issued in 1963 was the first stamp printed for trials with new cancelling machines.
The 5¢ City Delivery issue of 1963 was the first commemorative issue produced with tagging.
Precancelled stamps and service-inscribed stamps are not usually tagged because they need not be routed through the cancelling equipment.
Other uses
Since luminescent ink or luminescent paper are only delivered to specialist printers, tagging also serves as an anti-counterfeiting measure, similar to the practice on
banknote
A banknote—also called a bill (North American English), paper money, or simply a note—is a type of negotiable promissory note, made by a bank or other licensed authority, payable to the bearer on demand.
Banknotes were originally issued ...
s.
Alternatives
When
Deutsche Post of the GDR
The Deutsche Post (''DP''), also Deutsche Post of the GDR (''German: Deutsche Post der DDR'') was the state-owned postal and telecommunications monopoly of the German Democratic Republic (GDR - East Germany). The DP was placed under the control o ...
expanded automated mail processing in the 1980s, they did not use luminescent tagging, but used sideways illumination to identify the shadows of the stamp perforation in order to position mail items in cancelling and sorting machinery. Red light was used for this purpose, giving a good contrast to ordinary writing ink colours and enabling machine reading of postcodes. Some issues of
Postal card
Postal cards are postal stationery with an imprinted stamp or indicium signifying the prepayment of postage. They are sold by postal authorities. On January 26, 1869, Dr. Emanuel Herrmann of Austria described the advantages of a ''Correspo ...
s were printed entirely in orange to facilitate the latter process. However, the colours of the
imprinted stamp
In philately, an imprinted stamp is a stamp printed onto a piece of postal stationery such as a stamped envelope, postal card, letter sheet, letter card, aerogram or wrapper.Carlton, R. Scott. ''The International Encyclopedic Dictionary of ...
s was later changed to those of the usual
definitives of the corresponding value, and simulated perforations were added around the stamp design to help locate the stamp position.
References
Further reading
* Paquette, Gene and Ken Lawrence. ''Luminescent Tagging on United States Stamps: A series of articles reprinted from the United States Specialist''. Katy, TX.: United States Stamp Society, 2007 29p.
External links
*
*
* {{cite web , url = http://www.stamp-shop.com/dummies/see-phosphor.html , author = Robert Murray , title = Phosphor Bands and How to See Them , date = 2015-01-30 , accessdate = 2015-12-04
Philatelic terminology
Luminescence
Postage stamps
Printing