"How'd They Do That?"
[Column #13, 1/96]
It's amazing what you can do with hot and foil stamping.
National Geographic's best-selling issue had one on its cover. Shoppers snapped up three times more boxes of Kellogg's Ghostbusters when it had one on the box. Miller Breweries used one in a Halloween promotion and sales were 180% of the previous year's. What is it? It's a hologram, one of those silvery three-dimensional images. Holograms are also on driver's licenses, credit cards, bus passes and discount and rebate coupons now, not to increase sales but to increase security, as holograms are all but impossible to counterfeit.
How do they make and affix these holograms? It involves foil-stamping, which is the local angle for this story. Holograms are made using a laser and a light-sensitive material chemically similar to a photographic emulsion. A 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 re-creates the second beam to redirect and form a three-dimensional image. Unlike photography or painting, holography can render a subject with complete dimensional fidelity. A hologram can create everything your eyes see, size, shape, texture, and relative position. However, if you try to touch a holographic image, all you'll find is focused light.
There are two basic types of holograms, "reflection" and "transmission." Reflection holograms are lit from the front, reflecting light back to you. Transmission holograms are lit from the rear and bend light as it passes through the hologram to your eyes. The ones we're talking about here are of the latter variety.
Foil-stamped holograms begin with a metal holographic plate etched by extremely narrow laser beams or with a glass master coated with a silver spray to create the first shim, known as the metal master. It's a mirror image of the original master. The metal master is placed in a nickel electroplating bath. Shims made in this first generation are known as "grandmothers." Each grandmother shim has only one hologram. "Combining" is the process of taking holograms from the grandmothers to get multiple holograms on a shim. The more holograms on a shim, the more efficient and cost-effective the production process. During combining, registration marks are added; the marks are later read by holographic stamping and die-cutting equipment.
The combined plate is electroplated to grow the "mother" shim, a mirror image of the hologram. When the mother shim is put through the electroplating process, the result is the stamping shim. Using special embossing equipment, the holographic image is embossed onto rolls of film (usually polyester) coated to receive microembossing. This microembossing is usually 1/1,000,000" deep. Silver is generally the color of choice for holograms because it doesn't hide the rainbow effect of embossed holography. For higher security, though, transparent or tinted translucent colors are generally used.
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, etc.
Although there's obviously a lot of science that goes into making holographic foils, any full-service, experienced finishing house can order the foil you need and ensure that it's applied properly.
You find them on the back of your driver's license, credit cards and even monthly bus passes, theater tickets and merchandise tags. They're magnetic stripes encoded with information about you or a product or how much money you have left on the card. How they get information onto the tape is the domain of physicists, computer scientists, engineers, and data security specialists. How they get the magnetic stripe onto the card or ticket, though, is the business of the foil stamper. The magnetic portion of the tape is essentially the same as that you find in a cassette, videotape, etc. In a thin-film lamination process, it's combined with release and adhesive coats. When applied, the magnetic tape doesn't yet have any information on it.
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 put it on another (an instant increase in available credit). There are still cleverer people to thwart them: 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.
As with holographic foils, although magnetic stripes may seem exotic, a full-service finisher can get you the right magnetic stripe foil and apply it correctly.
With most foils the goal is to make them un-scratch-off-able. With foil-stamped scratch offs, the goal is to make them only durable enough that they conceal what lies beneath them but will yield to the customer who wants to scratch them off. For state lottery "scratchers" and other very high count jobs, the scratch-off surface is generally applied in a screen-printing process. But for shorter run lengths, a foil-stamped scratch-off surface is the economical way to go.
So, how do they make the foil scratch-off-able? The key is using a soft metal, like lead, rather than the harder metals used in decorative foils. One interesting thing a finisher has to keep in mind is that, to ensure that people can't hold the piece up to the light and read the print hidden by the foil, a relatively heavy or dark stock should be used for printing. Again, back to those clever, unscrupulous people, the advantage to using the oft-maligned lead as the metal is that it prevents someone from using x-rays to read the print beneath the surface without having to scratch it off. (When the jackpot is up to $30,000,000 or so, people will try anything.)