Custom Printing: Novel Digital Foiling Options

When it rains, it pours. And when this truism pertains to commercial printing, I’m intrigued. More digital embellishment options mean OEMs (original equipment manufacturers) are focusing on post-press finishing equipment. And this portends an expansion of digital commercial printing in general.

It’s like the transition from the early plastic, copier-like digital presses to the huge, digital laser and inkjet presses built on heavy-metal frames by OEMs that used to only manufacture offset presses.

So I was pleased to read an article about “Sleeking.”

Sleeking is a digital finishing process, or more specifically a digital embellishment process, that uses pressure and heat to bond foil (from a roll) onto heavy-coverage digitally-printed ink laid down by an HP Indigo press. (An HP Indigo is a digital laser custom printing press that uses toner particles suspended in liquid ink.) Sleeking allows you to lay down the foil digitally, then run the substrate back through the Indigo a second time to print either adjacent to the foil or even on the foil.

Here’s Some Context

It used to be the case that a metallic finish had to be applied using a metal die. The process was called hot foil stamping. You would pay maybe $300 to $500 for a die that would yield one static image (the same on all copies). This would add to the manufacturing time as well as the cost and would require subcontracting this portion of the job to a specialist. Then your printer would use the metal die along with heat and pressure to punch out the foil from a roll and adhere it to the substrate. (For instance, you might do this to foil stamp a book title on a hardcover print book cover.)

Or, you could do cold-foil stamping (a more modern process that does not require metal dies). Cold foil stamping involves first printing a UV-curable (hardened by ultraviolet light) adhesive on the substrate using a printing plate. This UV light makes the adhesive tacky. Then, a roll of metallic film is applied to the tacky adhesive. Foil adheres to the sticky image areas, and the scrap form the non-image areas will stay on the liner sheet (the roll). The benefit, for the most part, compared to hot foil stamping, is that a metallic effect is achievable without a metal stamping die. The process also allows for detail, such as screen gradations, small type (down to about 5 pt. type), and thin rules. You can also laminate or otherwise coat cold-foil stamped material. (If you’re interested in the process, you may want to research the Scodix process or Vivid3D, which seem to be very similar to cold foiling.)

The New Process

With “Sleeking,” you first lay down a heavy coating of liquid HP Indigo ink (I mean really heavy: 400 percent, or four clicks on a digital press) on the substrate. (To put this in context, your offset printer might request no more than 280 percent “total area coverage” among the four process inks—cyan, magenta, yellow, and black—for an offset printed job.)

This is the base that will accept the foil (which comes on a roll). In fact, some (powdered) toners can even be used in place of HP digital ink. (Since this is a new process, experts are still testing toners, hot roller pressure, substrates—coated and uncoated—and the actual amount of liquid toner coverage needed prior to adding the foil.)

The foil can be laid down as a spot application or a flood application (the whole sheet). This process is even good for variable data. (For instance, you could lay down 400 percent Indigo digital ink for an invitation, changing the name of the addressee on each printed sheet prior to the Sleeking process.)

Once you have applied the base 400 percent pass of Indigo ink (from a separate layer in your InDesign file), and have allowed the job to dry (some printers like to take six to eight hours for this part of the job to ensure total drying), you can feed the press sheets into the Sleeker and apply the foil from a roll.

Heat and pressure adhere the foil to the (dry) 400 percent coverage of Indigo ink, but the non-image areas do not remove the foil from the donor sheet. (A GMP Foil Laminator performs this step.) This is actually an economical process, since you can rewind the foil roll and use it again (as long as you’re using other parts of the sheet from which no metallic film has been taken for the Sleeking process).

To me this sounds a bit like the cold foiling process.

Sleeking will allow you to apply spot foil or flood the whole sheet. It can be a simple, clear gloss or matte finish or a metallic gold or silver, or it can even be a holographic image of type, a graphic pattern, or variable data.

The third step is like the first. After printing the base 400 percent toner and then Sleeking the job on the GMP Foil Laminator, you can bring the press sheet back to the Indigo digital press for another pass. You can print the rest of the job next to the foil (think “trapping,” in which the foil and remaining ink do not touch), or you can even print the HP Indigo Ink over the foil. This approach yields colorful metallic results that far exceed the original gold and silver foil of the Sleeking process.

Some Considerations

Paper choice is very important for this process, and experts are already busy testing press sheets. Coated paper seems to work better than uncoated (to ensure adequate adhering of the foil to the dry HP Indigo ink). Papers must have been approved for use on an HP Indigo press, whether they are coated or uncoated, to ensure success.

Variables to consider include how much total ink coverage to print prior to Sleeking, and how much heat and pressure to apply. Some printers experimenting with the process use more than one hit of ink (called a click on a digital press) in a particular location. Uncoated paper seems to complicate the process, sometimes causing speckling, but some printers like the fact that the uncoated paper has texture, and they don’t mind the “grittiness.” (I found a good article on the subject that you might want to read, called “So What Is Sleeking?” by Jeff Truan, published on 5/3/18, on www.nobelusuniversity.com.)

If you think this is a multi-run process, you’re right, and this can be a consideration when choosing paper. After all, you’re printing four hits of HP Indigo ink on a press sheet, then adding foil in a Sleeker, then going back to the HP Indigo and printing the whole sheet again. That can be hard on a press sheet. Therefore, it may be wise to use cover stock rather than text stock for the job (perhaps use Sleeking on a poster, business card, book cover, or a self-mailing marketing piece). The process as noted in Jeff Truan’s article can accept up to 18 point board, which should hold up well.

Trapping can also be an issue, according to “So What Is Sleeking?” by Jeff Truan. More specifically, printers who create foiled areas surrounded by white can sometimes see a black halo around the foil, where the preprinting extends slightly beyond the foiling. In these cases, commercial printing vendors experimenting with the process have replaced the 400 percent black underprinting with 400 percent yellow Indigo ink, which seems to solve the problem.

Akin to trapping, register can also be problematic. Aligning foils and inks perfectly when you’re printing a press sheet once on an HP Indigo digital press, then adding foil on a GMP Foil Laminator, and then printing again on the HP Indigo leaves room for error in precise fit (alignment, register). Therefore, it’s wise to keep this in mind and design wisely for the process.

The Takeaway

What can you, as a designer, print buyer, or printer learn from this process (which is actually more than a couple of years old by now)?

1. 1. Anything that catches the eye will be more likely to capture the imagination of the viewer or reader. This is particularly true when you think of all the images we see every day, including all the marketing mail in the mailbox, all the product packaging, and all the signage.

1. 1. Foil stamping used to involve making a metal die, which increased the overall cost of the job as well as the production time needed. If your job press run is less than 1,000 to 2,000 copies, this new foiling process might be right for you. However, for longer runs, making the die the traditional way may still yield a lower cost per unit.

1. 1. Between hot-foil stamping, cold foil stamping (and similar technologies such as Scodix, Vivid3D, and Sleeking), it’s clear that manufacturers are addressing the need for digital finishing options to pair with digital custom printing options (particularly to avoid bottlenecks). All of these developments in digital finishing show that digital printing is being taken very seriously.

1. Sleeking, or Scodix, or Vivid3D, which might be right for your job, has the distinct benefit of allowing you to vary the foil image for each individual product you print.

And this kind of personalization can go a long way in speaking directly to your customers.

This entry was posted on Sunday, February 28th, 2021 at 11:35 pm and is filed under Foiling. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.