Digital Printing Paper User's Guide

As digital marking devices proliferate, so do digital papers. Digital papers are not just cut-sized offset press stock or simple office papers, but specialty papers in their own right. A paper suitable for digital print has the basics of basis weight, shade, thickness, opacity and gloss plus much more.

Digital papers have a tight tolerance on size variation. Precision sheeting is an entry-level criterion for the manufacture of these small-format papers. Additional properties are a function of the type of digital press: Digital papers do not cross the different marking technologies. The paper selected must fit the press. Here are three examples:

Laser or toner-based marking engines are most prolific. Fusing toner to paper places special demands. Papers must have controlled moisture content to withstand the heat of fusion. They also must resist curling throughout the process path.

Inkjet marking engines spray either a water- or solvent-based solution onto the substrate. Papers must be able to absorb the water-based ink without distortion and solvent-based ink without swelling. Custom paper formulations are essential for inkjet devices.

HP Indigo presses use a special ink coupled with fusion technology to color the substrate. Most papers require special coating for proper adhesion.

Some selection help is available through certifications called scripts. RIT certifies papers for both the Indigo and Kodak NexPress to rigid criteria developed in conjunction with the manufacturers. Additionally, the IPA prepress association will critically look at various digital technologies and papers for both printability and color reproduction in 2009.

The aesthetics of digital papers defy classification. The designer is more center stage in the digital process, providing files that go right to press with no intervening steps after preflight. Just as in offset, paper is a key component in the rendering of the imagery as well as contributing to the functionality and tactile feel of the product.

If paper producers provided critical color information about their papers (specifically L*a*b*), graphic artists could soft-proof their designs more effectively. Sadly, this information is not available for digital paper—or for offset stocks, for that matter. Hard-copy proofs are needed for color-critical digital output. Swatchbooks provide the only alternative for preprint look and feel.

Color gamuts of digital devices vary widely and are substrate-dependent. A large gamut does not guarantee a color match. As digital print advances into the classic sheetfed world, color management technology will follow. There are some early signs of this beginning.

Wausau Paper Co. recently launched a comprehensive paper characterization chart relating its brands to ink coverage, a necessary indicator for optimizing paper choice. It is an ambitious step in the right direction and fills a gap in advancing high- quality digital printing. Choosing an optimum digital paper is anything but systematic. When a digital job requires “sheetfed offset quality,” experience is currently the best guide.

ONLINE: go to graphicartsonline.com/paper