What happens if you photocopy something you’re not supposed to photocopy? If it is a finely engraved document—money, a traveler’s check, a stock certificate—the copy comes out smudged or faded. If it is a simpler document—a money order, a supermarket coupon, a gift certificate—and if you use a good color copier, the copy is often a convincing counterfeit.
The VOID pop-up is a secret gimmick to foil the latter type of counterfeiters. It works simply enough: When a document containing the device is photocopied, the word “VOID” appears on the copy. At best the VOID is faint and fuzzy, like the Shroud of Turin. But users of the pop-up feel it must take a lot more guts to try to pass a counterfeit with the VOID than without it.
The VOID pop-up was invented by the American Bank Note Company but not patented. It has been adopted by other document printers. It is not regarded as effective a security device as currency-quality engraving. The time and expense of engraving make it suitable only for the most important documents, however. The VOID pop-up has been used mostly for medium-security documents, including, according to American Bank Note, Chase Manhattan Bank money orders and Kentucky Fried Chicken gift certificates.
The VOID pop-up uses a screen—a background of dots so fine they appear as an even gray or pastel shade. From a normal viewing distance, the only distinguishing feature of a screen is how dark a gray it is (assuming black dots on a white background; the same argument applies for other ink colors). In turn, the shade of gray depends only on the percentage of the total area that is covered by the dots.
Two different screens can look the same. One screen might have larger dots, a different arrangement of dots, or a different shape from another. But as long as the percentage of black area to white area is the same, and as long as the individual dots are too small to be seen individually, both screens look the same shade of gray.
Two such different but seemingly identical screens can make a VOID pop up. One screen is used to print the letters VOID across the document. The other screen forms a background to the letters. Both screens have exactly the same density, so the original document seems to have an even gray or pastel background.
A Xerox machine sees things differently from the eye. One of the screens is chosen so that the configuration of its dots will bleed together on the copy. This screen comes out darker or of a different quality than the other, and the VOID is visible.
The system isn’t foolproof. Copiers vary, so the VOID is conspicuous with some machines, scarcely noticeable with others. Occasionally a ghostly VOID is visible on the original, to the consternation of innocent consumers who aren’t intended to know about the pop-up at all. There is a screen attachment for some makes of copiers that defeats the pop-up and allows clean copies.
There are still other ways to prevent illicit photocopying. Prospects/New Book News, a New York-based weekly newsletter that summarizes the plots of upcoming novels for motion-picture producers, is printed on red paper. Red shows up nearly black on most black-and-white copiers. (As subscriptions are five hundred dollars a year, producers are sorely tempted to make Xerox copies for associates.) Of course, Prospects can be copied on a color copier, and on those black-and-white machines that have red filters.
At the other end of the spectrum, a light, swimming-pool-bottom blue does not reproduce on most copiers. Turquoise felt-tip pens are used to make marginal notes on magazine boards. The notes are invisible in the photographically printed magazines. In 1971 Computerworld, a trade publication, postulated the following use of light-blue print:
The Diners Club, whose accounting system has been attacked by people trying to keep their accounts straight, has apparently found one way of keeping the complaint level down—particularly those types of complaints that are copied to various federal and state authorities, Better Business Bureaus, Ralph Nader, etc. It won’t, of course stop the complaints altogether, but it will certainly reduce their effectiveness in many cases.
What Diners Club did was redesign the forms, printing much of the vital data in non-reproducing blue. As a result, after it has been put into the copying machine, the output simply is almost incomprehensible, and certainly much less persuasive to other people who may want to read it.
According to Diners Club, the color choice was a coincidence—the Diners Club logo is blue.