."Beyond Typical Foil Stamping: Holograms, Magnetic Stripes, and Scratch-Offs"
[Column #66, 6/00]
Foil stamping is an amazing process that can do much more than spruce up an annual report. This article will touch on a few of its many applications.
Ever look at a hologram and wonder how on earth such a thing is made? Believe it or not, it’s a fancy type of foil stamping that has been known to triple sales for myriad businesses. Those silvery three-dimensional images can be found on anything from cereal boxes, Happy Meal toys, special promotional items, driver’s licenses, credit cards, bus passes, and rebate coupons. Beyond their eye-catching glimmer, holograms are used to increase security because they are nearly impossible to counterfeit.
Creating holograms is a foil-stamping process using laser and light-sensitive material chemically similar to a photographic emulsion. Initially, the hologram records a pattern of infinitesimal lines (called an “interference pattern”) made by the interaction of two beams of laser light. After processing, the hologram is illuminated at the same angle as one of the beams (the “reference beam” ) used during the original exposure. The hologram recreates the second beam to redirect and form a three-dimensional image. Unlike photography or painting, a hologram is completely dimensional—adding size, shape, texture, and relative position to an object that feels mysteriously flat to the touch. Ironically, all that dimension is created with focused light.
There are two basic types of hologram—“reflection” and “transmission.” Reflection holograms are lit from the front, reflecting light back to you. Transmission holograms are lit from behind and bend light as it passes through the hologram to your eyes. In this article, I will discuss transmission holograms.
Foil-stamped holograms begin with a metal holographic plate etched by extremely narrow laser beams or with a glass master coated with a silvery spray to create the first shim, referred to as the metal master. (It is a mirror image of the original master.) The metal master is then placed in a nickel electroplating bath. Shims made in this first generation are known as “grandmothers” and each grandmother shim contains only one hologram. “Combining” is the process of taking holograms from the grandmothers to create multiple holograms on a shim. The more holograms on a shim, the more efficient and cost-effective the production process becomes. During combining, registration marks are added; the marks are later read by holographic stamping and die-cutting equipment.
The combined plate is then electroplated to grow the “mother” shim, a mirror image of the hologram referred to as the stamping shim. Special embossing equipment is used to emboss the holographic image onto rolls of film (usually polyester) coated to receive microembossing which is usually 1/1,000,000" deep. Silver is often the color choice for holograms because it doesn’t hide the rainbow effect of embossed holography. When security is critical, however, transparent or tinted translucent colors are generally used.
Finally, the film is combined with a hot-stamping foil or pressure-sensitive (sticky-back) material, which can be die-cut to make stickers or stamped onto packaging, trading cards, security documents, and so on.
It seems these mysterious magnetic stripes have taken over our lives and can provide nearly any business with huge amounts of confidential information with the mere swipe of a card. I’m referring to those stripes on the back of your driver’s license, credit and debit cards, theater tickets, merchandise tags, bus passes—even your library card. Just how the information is encoded on these tapes is the domain of physicists, computer scientists, engineers, and data security specialists! Our job, as a foil stamper, is to apply the magnetic stripes to a variety of surfaces.
The magnetic portion of the tape is essentially the same as that you would find in a cassette or videotape and, during the application process, doesn’t yet contain any information. During a thin-film lamination process, the tape is combined with release and adhesive coats.
Clever, unscrupulous people sometimes attempt to undo the hard work of the foil stamper and data security specialist. Hackers have been known to remove a magnetic stripe from one card and place it on another providing instant credit card theft. Fortunately, there are still even more clever people who can thwart their efforts: One way is to mold a credit card out of plastic that has had nickel particles stirred in with it. The magnetic stripe is affixed, and the card is run through a machine that senses the location of the nickel particles on the card and computes a cryptographic “checksum” of their positions. The checksum function is secret and is used as a decryption key. The remaining information on the magnetic stripe is encrypted in such a way that the nickel-particle checksum of the plastic card is used as the decrypting key for the data on the magnetic stripe. Amazing stuff!
Although some science obviously goes into making both holographic and magnetic stripe foils, any full-service, experienced finishing house should be able to order the appropriate foils and ensure they are applied properly.
With most foils, our goal is to make them un-scratch-off-able. The goal in a scratch-off job is to make them only durable enough to conceal what lies beneath them but will yield to the customer who wants to scratch them off. For high volume projects such as state lottery tickets, the scratch-off surface is usually applied in a screen-printing process. But for shorter runs, a foil-stamped scratch-off is the most economical way to go.
The key to foil stamping scratch-offs is the use of soft metal, like lead, rather than the typical harder metals used in decorative foils. A relatively heavy or dark stock is usually necessary to ensure that people can’t hold the piece up to the light and read the print hidden by the foil. However, there are a variety of color choices (such as silver and gold in bright or matte finish) including zebra foil that is made up of wavy silver and black lines that prevent readability. Believe it or not, the advantage of using the oft-maligned lead as a metal choice is to prevent would-be scratchers from using x-ray machines to read the print beneath the surface. When the jackpot is in the millions, some people will try anything!