Hiding in plain sight: basics of tagged stamps and ultraviolet light

Oct 22, 2007, 8 AM

By Janet Klug

Luminescence, phos-phorescence, fluorescence, ultraviolet lamps — what does any of this have to do with stamp collecting? A lot, actually.

In the late 1950s, many nations were looking for faster, more efficient ways to process ever-increasing quantities of mail. Post-marking and sorting the mail was a tedious, time-consuming task that was mostly done by hand.

Businesses and manu-facturers had begun using bigger, better and faster machines that could do monotonous, repetitive tasks. Why couldn't the world's postal administrations do the same?

Manufacturers such as Pitney Bowes, which already had a thorough knowledge of postal operations because of their metered mail equipment, began developing machines that could find the postage stamps, flip and turn the mail fed into it and then apply postmarks.

The process of finding the stamp was the most difficult, but that difficulty was overcome by applying a nearly invisible substance to stamps so that machinery could detect them.

Postal administrations did not want the use of automatic facing and canceling machines to dictate blanket changes in stamp design, so equipment man-ufacturers sought a coating for the stamps that would be invisible or nearly invisible to the unaided eye.

Science came to the rescue with taggants and some inks that glow when exposed to ultraviolet light. Machinery was developed that would rapidly emit UV light onto all the mail fed into it.

The UV light would find the postage stamps that had taggant applied over the main design, in the margins, or eventually to the paper upon which the stamp was printed.

The machinery would flip the letters so that all the stamps were in the same position and then apply the postmarks in a few blinks of an eye.

Even though collectors cannot usually see the substance, it changed the way mail is handled and the way stamps are printed.

New terminology was added to the stamp collector's lexicon, and new equipment was required for those who wished to see what could not usually be seen and to collect it.

Collecting tagged stamps requires knowing a few basic words: luminescent, fluorescent and phosphorescent.

"Luminescent" refers to a substance that glows when exposed to UV light. If the luminous coating or ink on a stamp continues to glow for a short time when the UV light is switched off, then the coating on the stamp is phosphorescent.

If the stamp ceases to glow when the UV light is switched off, it is called fluorescent.The luminescent coating applied to a stamp is called "tagging" or "taggant." Once a stamp has had taggant applied, it is referred to as being "tagged," and so is a stamp printed on paper coated with taggant prior to printing.

A pane of four Canadian 55¢ Girl and Dove, Peace and Love stamps (Scott 1813) photographed under ultraviolet light is shown in Figure 1. The stamps have tagging added on all four sides around the printed stamp design.

The tagging can be done in blocks, bands, bars, all over the stamp, or in a design or pattern.

A United States 45¢ Universal Postal Union stamp (Scott 3332) photographed under UV light is shown in Figure 2. The star-shaped tagging applied to this issue is very distinctive.

Some postal administra-tions alter the tagging on different denominations of stamps to further enhance the automatic features, such as mail sorting enabled by some mail-han-dling equipment.

Some stamps, for exam-ple the ubiquitous British Queen Elizabeth II Machin definitives, have a multitude of collectible luminescent varieties.

Figure 3 shows three tagging varieties of British 8-penny Queen Elizabeth II Machin stamps (Scott MH64) photographed un-der UV light.

The stamp at left has one band of tagging at left; the stamp in the center has one band of tagging in the center; and the stamp at right has one band of tagging at right.

Although the Scott Standard Postage Stamp Catalogue does not differentiate between the three tagging varieties, specialist collectors certainly do.

Specialist catalogs such as The Complete Deegam Machin Handbook by D.G.A. Myall and The Connoisseur Catalogue of Machin Stamps, edited by James Negus, exist to assist the specialized collector in chasing the seemingly infinite number of varieties of this fascinating definitive series.

Tagging errors, including missing taggant, are known and sought by some collectors.

Shown in Figure 4 is a U.S. 30¢ Columbus at La Rabida stamp (Scott 2626b) photographed under UV light. This stamp is an in-teresting tagging freak.

In addition to the normal tagging around the edges of the stamp design, their is a "0" shaped tagging spot near the center of the design that probably resulted from a bit of lint or other foreign matter that was stuck to the tagging mat (plate) when the tagging was applied.

Most tagging is not visible to humans, but some taggants, such as many of the phosphor bands on the Machin stamps, were mixed with varnish or other media that are partially visible to the unaided eye.

This varnish can become discolored or stained from exposure to the sun or from being soaked too long, making the band starkly visible. What you are seeing in such cases is not really the tagging but the varnish that holds it.

Collectors who wish to find tagging on stamps, as well as collectible varieties and errors in tagging, need to acquire and use a UV lamp.

Exercise maximum care when working with a UV lamp. Never look directly into the light coming from a UV lamp. It will not look very bright or ferocious, but looking into it could burn the corneas of your eyes. This is a painful and potentially serious condition that can cause permanent loss of visual acuity. It helps to wear glasses when using a UV lamp. Keep your hands away from the light too, because exposure to UV light can burn. Wear gloves and sunscreen if you will be working with a UV lamp for extended periods.The best way to check luminescence with a UV lamp is to arrange the stamps you wish to check by setting them out in a work area. The work surface itself should not be luminescent because that will overpower the luminescent properties of the tagged stamps.

Darken the room by turning off all the lights. Switch on the UV lamp. Make your observations quickly, and then switch off the UV lamp and turn on the ordinary lights. Working in short, concentrated spurts is better for your eyes and will help keep the UV lamp in good operating order for a longer period.

UV lamps are read-ily available in longwave, shortwave or combination models. Longwave models will detect fluorescent tagging. Longwave lamps are less expensive and will suffice for most stamp-related activities.

Shortwave lamps burn out more quickly and are considerably more expen-sive, but they are useful for detecting the after-glow of phosphorescent tagging. For U.S. stamps, you will need a shortwave lamp.

You can also use a UV lamp to distinguish certain types of forgeries and re-pairs. A longwave lamp is also useful in trying to determine paper types.

Many shortwave lamps come with filters that will allow them to be used for longwave operation. Combination models go from longwave to shortwave operation with a flick of a switch.

UV lamps are available from scientific supply sources and from philatelic supply dealers. Subscribers to Linn's Stamp News qualify for discounts from the Amos Advantage program. In addition to a full range of stamp collecting supplies, Amos Advantage offers a combination UV lamp for less than $100.

Write to Amos Hobby Publishing, Box 828, Sidney OH 45365-0828, call 800-572-6885 or visit the web site

You can enjoy the stamp hobby without searching for tagging varieties or us-ing a UV lamp, but the study of tagging on stamps is another facet of collect-ing that brings with it the thrill of the hunt.

Maybe, if you are lucky, you will experience the joy of discovering a rarity that was there all along — hiding in plain sight.