Perforations are the little holes that surround stamps on traditional sheets with water-activated adhesive.
The earliest postage stamps were issued imperforate, meaning there were no perforations or other means of separation provided on the sheet.
To obtain a single stamp from the sheet, one had to cut it off with scissors.
The first general issue of perforated stamps was the Penny Red from Great Britain issued Jan. 28, 1854.
Many stamps issued today are still separated by perforations.
Self-adhesive stamps, stamps that are separated from one another by die-cutting, grew rapidly in popularity in the United States beginning in 1993. By 1995, they were the stamps of choice for most U.S. mailers.
A number of countries issue otherwise identical stamps in both water-activated and self-adhesive formats, as shown by the two United States 32¢ Flag Over Porch stamps pictured in Figure 1.
At left is the lick-and-stick version from a pane of 100. At right is the peel-and-stick (self-adhesive) version from a pane of 20. Both versions were issued in 1995.
Though the stamps appear similar, it is easy to see the difference between the two types of separation. The perforated stamp at left has fairly rough tips all around that are a little ragged and not always identical in length.
These characteristics are caused by the stamps being separated from one another by hand through perforation holes that are punched or ground into the pane.
The die-cut stamp at right has identical rounded peaks and valleys surrounding the stamp, with perfectly shaped tips at each corner.
These stamps are precut by a machine into these identical shapes.
There are even die-cut self-adhesive stamps that differ from one another by the distance between the die-cut points surrounding the stamp.
To help identify different basic varieties of die-cut stamps, collectors can use a perforation gauge, the same tool used to measure differences in perforated stamps.
As an example, the 1999 Scott Specialized Catalogue of United States Stamps and Covers describes the stamp at right in Figure 1 (Scott 2920) as "Serpentine Die Cut 8.7 on 2, 3 or 4 Adjacent Sides."
That means the collector will find the peaks on the die-cut stamps measure 8.7 on the perforation gauge, using the same method used to identify perforations on traditional lick-and-stick issues.
Information about using the perforation gauge was presented in the Oct. 26 Refresher Course.
Although perforation and die cutting are the two most prevalent methods of separating stamps, many other methods have been used over the years.
Rouletting is a form of stamp separation that is closer to die cutting than perforation, in that paper is not really removed from the sheet, as happens when perforation holes are created.
Instead, small slits are made between each stamp at regular intervals, with even smaller sections of unslit paper remaining. The stamps can be separated from one another by tearing along the slits, through the unslit areas.
Small remnants of the torn unslit paper along the edge of the stamp make it possible to measure this type of separation as well.
Shown in Figure 2 are two versions of the U.S. 29¢ Flower coil stamp. At left is the version with roulette separations (Scott 2525) issued in 1991, while the pair at right from 1992 have perforations between the stamps (Scott 2526).
Notice also that both of these stamps have straight edges along the top and bottom. This is a familiar characteristic of U.S. coil stamps: straight edges on opposing sides of the stamp, either top and bottom, or left and right.
The stamp separation methods described so far were applied by the issuing postal service. Some U.S. stamps were privately perforated in the early part of this century by companies that manufactured stamp vending and affixing machines.
These companies would create coil strips from imperforate sheets obtained from the Post Office Department and apply perforations that would make the stamps work in their machines.
Some European countries have issued stamps with syncopated perforations that include a larger oval-shaped hole among the smaller round holes.
The example shown in Figure 3 is a pair of Great Britain's 36-penny Queen Elizabeth II definitive issued Oct. 26, 1993. The oval hole among the vertical perforations is equal in width to three round perforations on the same stamp.
It has been suggested that the oval perforation makes stamp counterfeiting a little more difficult.
The term syncopated perforation also is used to describe coil stamps from the Netherlands with one or two perforation holes intentionally missing from each side.
In the Standard Handbook of Stamp Collecting, Richard McP. Cabeen writes that these syncopated perforations were created to add strength between coil stamps.
Along with these many intentional perforation and separation varieties, some unintentional varieties have been created as well.
Perforations that are completely missing from stamps that were intended to be perforated are known as perforation errors, and usually sell among collectors for premium prices.
If all the perforations are missing from a pane or sheet, the stamp is fully imperforate and is identified as such in the Scott catalog.
Stamps missing all of the horizontal perforations are known as "imperf horizontal." Figure 4 shows 10 of the U.S. nondenominated (4¢) makeup-rate stamp from 1991 with all horizontal perforations absent.
Obviously, stamps that are "imperf vertical" are missing vertical perforations.
If a single row of perforations are left off a pane of stamps, the resulting error is described as "imperf between."
For example, two such varieties are known for the U.S. 14¢ Sinclair Lewis stamp of 1985 (Scott 1856).
In one case, a single row of vertical perforations was missing from a pane of Lewis stamps, creating horizontal pairs of stamps perforated all around, but with no vertical perforation between them.
Such stamps are described in the Scott catalog as "horiz. pair, imperf between" (Scott 1856c).
In the other case, a missing row of horizontal perforations resulted in vertical pairs perforated all around, but with no horizontal perforation between them: "vert. pair, imperf between" (Scott 1856d).
There are many other unusual perforation varieties known as freaks that usually are less valuable than more scarce perforation errors (but not always).
Perforation shifts may result in perforations running through part of the stamp design, creating a stamp that is substantially off-center. If the shift changes the design of the stamp in some interesting way (by placing a bottom inscription along the top of the stamp, for instance), collector interest in the freak is usually more ardent.
Stamps perforated while stamp paper is partially folded may wind up with wildly angled perforations on part of the sheet. These so-called crazy perfs often cut diagonally through a postage stamp with both the horizontal and vertical perforations.
These and other perforation oddities are avidly sought by collectors of stamp errors and freaks.
Stamp separation obviously extends far beyond the basic perforation into many other areas. Additional information can be found in the Scott stamp catalogs and in Cabeen's Standard Handbook of Stamp Collecting.
Fundamentals of Philately by L.N. Williams provides extensive detail about the varieties of stamp separations around the world.
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