Postage stamp gum – a very sticky subject

By Janet Klug

When Roland Hill wrote the description of his prepaid postage adhesive, the postage stamp, he prescribed that it would be "covered at the back with a glutinous wash."

Today that glutinous wash is known as gum: the sticky stuff that affixes the stamp to the envelope.

You would think that its purpose would be purely practical, but for some stamp collectors gum has aesthetic value.

Some collectors are interested only in mint, never-hinged stamps with full gum, just as a stamp came from the post office. They are willing to pay premium prices for stamps with unsullied gum.

The regumming of classic stamps, a deceptive practice that collectors must be wary of, is common, because many collectors will pay a big premium for classic stamps with so-called full original gum.

Heavily hinged stamps are damaged goods and sell at a discount. The economic reward for converting a heavily hinged stamp into a pristine, mint, never-hinged stamp offers powerful temptation to those who practice to deceive.

If you are a collector who insists on full, original, undisturbed gum for your mint stamps, then you should learn some of the warning signs of regumming so that you don't get stuck.

Spotting regummed stamps can be easy or difficult, depending on how well it was done.

The first step is to know the characteristics of the gum. Is the original gum clear, creamy, shiny, tinted or dull? Is it mottled or ridged? Are there supposed to be gum breakers (vertical or horizontal impressions used in some stamps to keep them from curling)?

Knowing the characteristics of the original gum will help you spot regummed stamps.

If you are paying a substantial premium for never-hinged, full original gum, don't buy the stamp until it has been certified as such by a reputable expertizing service.

Pools of excess gum around the perforation holes are a tell-tale sign of regumming. Use a good magnifier to check for this characteristic.

The tips of the perforations might also be stiff from gum that has been applied after the stamp was separated from its neighbors. Normally, the torn edges of perforations are slightly feathered. Stiff and gummy perforations are a warning sign.

Gum condition can be described in many ways. A mint, never hinged stamp is one that has full, undisturbed, original gum with no hinge mark.

Mint, never-hinged gum is shown in Figure 1 on the back of a modern United States definitive stamp.

A stamp that is lightly hinged will show a slight mark where a stamp hinge was once attached, but the gum should not be greatly disturbed and there should be no pieces of the hinge still clinging to the stamp.

A stamp that still has pieces of a stamp hinge adhering to its back is described as having hinge remnants.

"Heavily hinged" is a description that can describe a multitude of stamp sins.

It can indicate a stamp that has been hinged badly or hinged more than once.

It also might indicate a large area of missing gum with multiple hinge remnants.

The back of a heavily hinged stamp of Burma is shown in Figure 2.

Low-quality hinges often turn brown as they age. This can also cause the stamps to discolor. The stamp shown in Figure 2 shows this browning as well as a heavy gum crease and toning spots well away from the hinge.

The crease probably resulted from careless handling. Toning is discoloration that can occur because of humidity or exposure to acidic paper.

Even if gum condition is not a major concern, you must be careful with heavily hinged stamps.

Hinge remnants can be used to mask a thin. The New Zealand stamp shown in Figure 3 has a thin that was not apparent until the hinge was removed. This is a damaged stamp, over and above any considerations of gum condition.

Poor-quality hinges probably contributed as much to the development and use of stamp mounts as did the desire for mint, never-hinged stamps.

Mounts can bring their own set of problems, though. Mounts should be empty when being cut to the proper size. Leaving the stamp in the mount while cutting invites cutting the stamp by mistake.

Use the correct size mount, and do not use excessive moisture to affix the mount to the album page. Excess moisture will leach under the divided back of the mount and cause a gum disturbance on the stamp.

A mount will adhere just fine with a light lick at its top center. Keep the moisture well away from the mount's edges.

Gum is important to many stamp collectors. But, in truth, the long-range health and preservation of stamps would be better without gum.

Depending upon how gum is formulated, it can crack, curl, discolor, eat into the paper, attract vermin, stick to an album page and cause other havoc in a collection.

An extreme example is the gum used on the German Ostropa souvenir sheet, Scott B68, and on the Hindenburg airmail stamps, Scott C57-58.

Because the gum used on these stamps contained sulfuric acid, which destroys paper, unused examples of these stamps are collected, as noted in the Scott catalog, with the gum removed.

The back of a block of four stamps of Tonga, plus attached selvage, shown in Figure 4, has damage caused by gum.

This type of damage is called tropicalization. It occurs when inferior gum is used in the manufacture of stamps, and the stamps are later subjected to less than ideal conditions, such as high heat and humidity.

Note that the damage makes the watermark on these stamps much more prominent.

Gum can also become glazed, brittle or cracked.

Cracked gum can cause noticeable damage to the stamp itself. The cracked gum on the back of the Italian revenue stamp shown in Figure 5 will eventually split the stamp in two unless the gum is washed from the stamp.

Short of soaking the gum from your stamps, the next best thing you can do is protect them by proper storage in albums or stock books and by not subjecting them to high humidity, sunlight or swings in temperature.

Water-activated gum, the standard until the mid-1990s, has the great advantage for collectors of being water-soluble.

In the late-1960s, Tonga, Sierra Leone and a few other countries introduced self-adhesive stamps. These stamps are peeled from backing paper and affixed without moistening the adhesive.

The gum on the first self-adhesive stamps was insoluble. Once adhered to the envelope, the stamp could not be separated from the paper.

Soaking in water would not remove the stamp. Lighter fluid would not budge it. Once applied, these stamps were really stuck, so used examples of them are collected on piece or on cover.

The first United States self-adhesive stamp, issued in 1974, the 10¢ Dove Weather Vane stamp, Scott 1552, is difficult to collect mint or used because the adhesive is difficult to remove and it causes mottling of the stamp paper. How much worse will these stamps look 100 years from now?

In the 1980s, Australia, the United States and many other countries produced gum formulations that made self-adhesive stamps affordable from a production standpoint, recyleable and more or less soakable for stamp collectors.

Many collectors who prefer their stamps in mint, never-hinged condition consider self-adhesives to be the bane of stamp collecting.

Mint self-adhesive stamps, such as the strip of Vanuatu stamps shown in Figure 6, must stay on their backing paper to remain as issued by the post office. The double paper causes album bulge, as self-adhesive stamps become the norm for new stamp issues.

How will self-adhesive gum fare over the years? In the 1960s, I mounted some Tongan self-adhesive stamps and stored them in a reasonably good environment. Some of the gum has migrated around the die cutting of the stamp on to the mount, permanently bonding stamp and mount.

I hope that the more recent self-adhesives are not time bombs ticking away in our albums.

For collector's, gum's original purpose as a functional element of stamp use has been overshadowed as they pursuit post-office-fresh examples.

Gum presents preservation challenges and can add to or deduct from the value of a stamp. You see, gum really is a sticky subject.

Thanks to Doris Shultz for suggesting this article.