The Dos and Don'ts of Foil Stamping

After the initial "Wow!," people often respond to an effective use of foil stamping with a fascinated "How'd they do that?" Graphic arts professionals like you and me know there isn't always a simple answer. Foil stamping poses unique challenges for designers, printers and finishers and requires coordination and communication among them to achieve a successful product, to get that "Wow!"

Because foil stamping involves so many variables, from inconsistencies in the manufacture of the foil itself to the order in which embossing, stamping and coating occur, it would be impossible for me to address all the possible pitfalls here. So, in this month's column, I'm going to lay some dos and don'ts on you. As a general principle, though, you should check with your finisher about particular jobs.

The Dos and Don'ts:

Play a consultative role with your customer. Keep in mind that a slight adjustment of a design may mean one run through the press rather than two. Your customer will appreciate the savings in time and money and will see you as a valuable resource.
Communicate with your finisher to make sure that the shade and type of foil (metallics, pigments, etc.) you want will work with the chosen stock and coverage area.
Check the opacity of the foil. Many pigment and pearl translucent foils can change appearance on colored stocks.
To prevent dulling, use care when specing foils to be stamped on dry, textured stocks. Dry stocks diffuse reflected light.
It's almost impossible to stamp over ultraviolet (UV) coatings, lacquers and specific film laminations. So, you should probably foil stamp before doing any of these.
Designs containing both large solid areas and fine intricate areas may require two foil stamping passes. To determine if both can be done in a single pass, saving time and money, consider the following:
The type of foil stamping equipment. A cylinder press is generally the best choice, as it can stamp the solid designs using less pressure and thus there's less chance for fill-in on the intricate areas. Other considerations include whether the press offers different heating zones, the direction the foil runs in relation to the direction the sheet runs and the capability of running more than one foil web.
The type of foil. Even if the press can run two foil webs, a single web may have to be used if the designs are too close together. So, if you're using only one foil, it should be one with a moderate release and medium-to-heavy coverage capabilities.
Stock. Getting away with a single pass on a porous, dry or textured stock is difficult. Such stocks require greater pressure to achieve coverage for the large solid, making it nearly impossible to keep the fine areas clean. Using a quality coated paper, by contrast, makes it easier.
Foil-stamped letterhead designs to be used in laser printers should be tested before running a job. The heat of the laser printer may be too high for certain combinations of foils and coatings.
As a rule of thumb, when foil stamping areas of intricate detail, make sure that the space between the lines in the design is no less than half the thickness of the stock. Also, coated or smooth stocks work best.
Avoid wet-trapping, which can occur if a sheet is varnished before the ink is dry. Wet-trapping can result in "gassing," or air entrapment, after the foil is applied.
Inks should have a low wax content, if you're going to be foil stamping over them. Rubber-based inks can be used but require the use of specially formulated foils.
Don't use silicone anti-offset powder. Sheets contaminated with silicone cannot be foil stamped. Make sure silicone spray isn't used on the folder, gluer or diecutting equipment, either. (When coatings are applied over anti-offset powder, the sheet will feel like fine sandpaper.)
Lastly, when specing a foil, weigh the relative importance of the following characteristics: Scuff resistance, stamping speed, amount of fine line or type design vs. solid coverage area design, resistance to fading and to chemicals such as solvents, light fastness (resistance to fading from exposure to light), resistance to water and humidity, consistency of quality from batch to batch, price and availability.
That's a lot to consider· and yet I've just scratched the foil-stamped surface. And speaking of scratching the surface, in an upcoming column I'll be revealing what's behind foil-stamped scratch-offs.