Not that long ago, if you wanted special ink treatments for your custom printing work, you had to opt for offset lithography. Digital printing just wasn’t there yet. But this has been changing, affording new options for short-run and variable-data work on digital printing presses.
Here’s a rundown of some of your options and some of the kinds of digital commercial printing equipment you should look for when researching this technology.
Textured Ink: a Tactile Experience
Let’s say you want to print a photo of an iguana in your short-run brochure print job, and you want the reader to get a visceral experience of the reptile’s skin when she or he runs a finger across the printed surface. Now you can achieve this effect with three dimensional inks.
On digital custom printing equipment such as the Kodak NexPress, you can add a clear textured coating over one of the inks (or over a particular area), using the fifth inking unit of the press for a clear ink. Basically, you would use InDesign, Photoshop, or Illustrator to isolate the particular color and then create a separate layer, in much the same way as you would isolate a selection for a varnish. Because the dimensional inks have larger particles than conventional inks, the heat of the fusing unit in the digital press will cause the dimensional ink to expand, providing a raised, textured surface.
Prior to the advent of textured digital inks, you had to use thermography to achieve this effect. First you would offset print the color on a traditional press, and then you would add powder to the still wet ink. The heat of a fusing unit would cause the ink and powder mixture to bubble up, providing a raised ink effect. This was expensive and time consuming.
Textured Ink and Faux Embossing
Using the concept of thick, raised digital inks, it is even possible to do digital embossing without needing to create a metal die for the job. The high-end HP Indigo press will actually allow you to run up to 250 passes of a textured ink to build up a raised surface. This raised surface can then be used as a digital die to emboss the remaining press sheets of your digital print job.
Expanding the Color Gamut
Offset lithography uses four process colors to simulate full-color imagery (cyan, magenta, yellow, and black ink). Since these colors can only create a limited subset of the hues visible to the eye, commercial printing vendors can add additional inks to expand the number of reproducible colors.
Now, digital presses can do this, too. For instance, consider the HP Indigo’s IndiChrome ink system, which can add orange, violet, and green to the CMYK process color inkset, dramatically widening the number of printable hues. In addition, for colors still out of the color gamut, the manufacturer in Israel can create spot color inks for the HP Indigo press.
In addition to process colors, the availability of various black and gray inks and toners has allowed the creation of fine arts photos with incredible depth and nuance. This has opened up the fine arts market to custom printing suppliers with digital equipment.
White Ink as a Color and as a Blocking Device
On the HP Indigo you can also print white ink. You might want to use this ink as an accent in your design, but you might also use it as a blocking device. For instance, if you have a clear plastic substrate (like a static cling) and you want to print a different image on either side, you can print a white ink base between the images. Or, you might choose a metallic substrate and then use white ink to block out the metallic in certain areas of the design.
Special Inks for Security Purposes
From a more functional point of view, here’s a brief selection of security-based effects you can create using a digital press:
- The Xerox iGen4 can give certain parts of a ticket or other document a gloss coating, creating a security watermark that’s difficult to counterfeit.
- Xerox digital presses can also add fluorescent ink markings visible under UV light, ink markings only visible under infrared light, or microscopic printing (as small as 1/100 of an inch) that can be verified under a magnifying glass but that appears only as a jagged pattern to the naked eye.
- The Kodak NexPress can add MICR (magnetic ink character recognition) ink for banking documents and checks.
The security ink functions of digital presses make them ideal for tickets, birth certificates, vouchers, and identification papers. Moreover, the CMYK halftone dots for the individual security features can be printed at different angles to the rest of the text, allowing these security features to be read separately from the main text without needing to add any other inks.
Gloss/Dull Cover Coatings for Aesthetics and Protection
In contrast to security inks, extended color gamuts, and digital embossing, the normal process of coating the cover of a book or poster with a gloss sheen for aesthetics and protection is not dramatic. However, it serves an essential function, and the Kodak NexPress can do this commercial printing job quite well.
Conclusion
All of these effects were once only available in the arena of offset lithography. They were expensive. You needed to to use additional coating units on press, create metal dies, and add additional printing plates. Furthermore, the process only produced multiple copies of one original.
Now, due to the advent of liquid toner-based inks (rather than dry toner) for electrophotography (i.e., laser printing), commercial printing providers can vary the images infinitely, making each page different from the last. Or they can produce an incredibly short press run of 20 copies, or even just one. Or they can build up the thickness of one area of the custom printing job to create embossing dies or textures.
And in most cases the process does not involve an additional click charge for the digital printer, but only a modest additional charge for a variable-data and specialty-imaging software package.
This entry was posted
on Saturday, May 5th, 2012 at 1:07 pm and is filed under Digital Printing, Printing.
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