Foil Application

January 15, 2008

However it is applied, foil in its many varieties makes a label stand out from the crowd.

Foil Application

However it is applied, foil in its many varieties makes a label stand out from the crowd.

By Jack Kenny

Foil never loses its magic. Foil and other attractive packaging applications have gained such prominence among retail brands today that even products once considered humble are now gleaming from store shelves. Product marketers are making use of foils for reasons of competition, and the consumption of rollfed foils for label and other applications continues to lead the foil markets.

It is easy to find a pressure sensitive wine label that has a foil decoration, sometimes prominent, sometimes employed with subtlety. High end spirits make wide use of foils, though a recent trend among vodkas is for alternative bottle decoration. Foil has been a staple of the beauty packaging industry forever, it seems, and that industry is going quite strong.

Flatbed hot stamping and rotary hot stamping dominated the narrow web landscape until the late 1990s, when growing interest developed in cold foil application. Each remains in use today, and each has comes with its own benefits and challenges.

The oldest form of foil application is through the use of a flatbed press. These are still in production today by such companies as Newfoil and Kensol-Franklin. The quality of the foil stamp is high, as is the customer satisfaction. The press moves the label through intermittently, pausing to stamp the foil by use of a flat die, heat and pressure. The cost of the stamping dies is negligible, which has always been a selling point for these systems.

They are, however, offline machines, and require preprinted labels to be re-registered and run through them for the stamping. The process can add to labor and production time.

Far more popular, though not ubiquitous, is inline rotary hot stamping, which has been a standard for many years.

In recent years, manufacturers of rotary hot stamping units have reported strong numbers for sales of hot stamping units in rotary presses. Others, however, see a strong challenge by cold foil. “Rotary hot stamping is in decline in the flexo market,” says J. Michael Rivera, vice president of sales for Amagic Foils. “Hot stamping foil is half of what it was 10 years ago in the United States,” says Michael Dolan of Nakai International.

The traditional rotary hot foil process is one by which foil is nipped between the substrate and a stamping roll which is heated by oil or electricity,  and which contains the image to be stamped. Oil heated rollers are said to offer more consistent heat, especially when the unit runs at higher speeds. Heat ranges differ based on the foil being applied. The use of heat to stamp foils into substrates also determines the speed at which the press will run. If the speed is too fast the stamping die will exhaust its heat more quickly and the foil transfer could then be incomplete.

Press operators like to work with speed, but if a press is running slowly it’s probably because foil is being applied. An increase in speed could bring the foil to the point where it is not fully transferring, but showing tiny pinholes.

A recent alternative to the solid brass stamping roll, which is costly, is a magnetic stamping die adhered to a magnetic cylinder. Another method, which utilizes solid brass without the cost of a full cylinder, is to use brass rings that mount on a special cylinder. The rings are lightweight and they cost less, but they deliver the full effect of brass rotary stamping. If a print job requires multi-row foiling with small foiling areas, narrow width rings could be the answer.

Flexible stamping

The industry has been turning for several years to the use of flexible cutting dies, which are mounted on magnetic cylinders and are much less costly than solid rotary tools. In the same manner some are turning to flexible stamping dies.

Replacing a worn stamping die is less expensive than buying a new one, as is manufacturer turnover time and press changeover time. The quality of the image produced by the flexible stamping dies is comparable to that produced by the solid die.

Cold foil

Long before the rest of the narrow web industry discovered how to use cold foil, the process was perfected At Driscoll Label in Fairfield, NJ, USA. Bob Biava, the former owner (now retired), developed a proprietary system called Star Brite that he licensed out to several converters around the country.
Toward the end of the 1990s others developed the cold foil application process, which had its rough edges (literally) in the beginning, but which now is widely accepted for certain types of print jobs.

Cold foil has made the application of foil available to anyone with a flexo press, because it is applied on a standard print station. A special UV curable adhesive is transferred by an anilox roll to a plate containing the image, large or small, and transferred again to the substrate. At that point the foil is nipped to the substrate, and a UV lamp cures the adhesive and bonds the foil to the substrate. The foil is then peeled away from the substrate, the unused portion taken up on a waste roller. The foils developed today for cold applications are somewhat transparent, allowing the UV to perform its curing duty without metallic inhibition.

Getting cold foil right means having the proper anilox roll, adhesive, curing system and plate. Because converters use their own equipment in various combinations to apply cold foil, results vary. Some have commented that the edges of patterns and letters are not as  sharp as those produced by the hot foil process. That’s the result of the wrong tension match between the foil and the substrate, experts say. Tension that is too high in one will cause a mismatch that could be visible when the foil roll removes from the substrate.

According to Rivera, end users are turning to cold application of holographic foils, then printing over them. “If you want to print on hot stamp,” he says, “you have to have a stamping die station in the middle of your press. With cold foil you don’t have to be concerned about that.

“A lot of printers are learning that you can print on top of holographic foils. They are putting multiple colors, process colors on top of these substrates, or full floods. Most of them are pretty much using silver. Once you print on silver holographic or silver foil, you can match just about any color you want.”
Cold foil, says Rivera, is a growing market, “much more so than hot stamp, because of the design capabilities. In comparison to hot foil, it’s almost plug and play. The process has really opened up doors to applying foil to labels.”

Flexographers, he adds, are using much more cold foil today than they were five years ago, even among very small printers.

Among frequently asked questions fielded by Rivera is this one: Why can’t I use cold foil on semi-gloss stock? “That’s because it sucks the adhesive in. The answer is to put a sealer on the substrate, or change to a high gloss or better quality.”

Foil quality

Nakai International Corporation, a Japanese company with a global presence, markets foils in the narrow web industry that it claims are manufactured with superior materials. They are also more expensive.

“Our consistency and manufacturing methods are further advanced than most,” says Michael Dolan, technical sales for Nakai. “A lot of our foils have splices in them (about which our customers complain) because every lot of 100' x 25" across is tested for cut and clarity, and if they don’t measure up they don’t leave the plant. We physically remove foil out of the rolls. If the inspectors find foil they don’t like they pull it out.”

Dolan says that Nakai’s release coats are made from a recipe that performs well, “and we are not buying low grade films. Ours are GE Teijin films. For a lot of different reasons, the ingredient list makes our foil more expensive.” That expense, he notes, is two to three times higher than other foils on the market today.

Nakai foils are manufactured in a superclean coating line, which Dolan says will contain no more than one particle of dust per 1,000 square feet. “We also constantly reformulate our products. We have one specialty foil that will adhere to substrates with dyne levels in the 20s, and regular foils that will adhere with dyne levels in the 30s.

Dolan says that Nakai foils run faster than others “because the release coats are better, the consistency is better. What you don’t see when you run consistent foil is that it is better. With inconsistent foil you get defects and the inspection equipment won’t run that fast. They wind up losing parts of images and letters. Ours is clean from one end to the other.”

“CCL had a Nilpeter press that was running hot stamp at 600 feet per minute using Nakai foils. QA Label bought our foil solely because of the speed, and getting zero rejects. We succeed when nothing else works and the converter’s back is against the wall.”