Unfortunately, "black ink on offset isn't very black," said Peter Crean, senior fellow and color scientist at Xerox.

To make up for the physical shortcomings of black process ink on an offset press, many publishers and designers pump up their dark designs with a special blend.

A rich black uses additional inks as undertones to create a darker, deeper and more robust black than is possible with process black ink. In four-color print jobs, the other inks (cyan, magenta and yellow), can be used to make black blacker.

For example, if a design has an area that is 100 percent black, adding 40 percent cyan will produce a richer black. In desktop publishing applications, this can be done as easily as creating a new color. Many desktop publishers differentiate this darker black from process black by naming it "Rich Black" or "Super Black."

Or if a design has a mix of color and black-and-white images, the photos could be scanned in as RGB and separated as CMYK to automatically produce a multicolor black.

Michael Riordan, professor at the Rochester Institute of Technology School of Print Media, e-mailed, "On a page with color images, a one-color, grayscale image will look comparatively flat. By using a multicolor black, the monochrome images will reproduce with a tonal range that better matches their color companions."

Consultant David Blatner says a clear victor has emerged in the desktop publishing wars. Click here to read more.

"The technical answer to the question of why a one-color black appears 'not so black' when compared to a multicolor black is a matter of density—how much light is absorbed. Where a one-color black may have a measured density of 1.6, a multicolor black may have a density of 2.0 or higher—keeping in mind that density is a logarithmic scale that amounts to a relatively significant shift in black."

Uses

Not all publishers have to concern themselves with getting a rich black.

For example, Riordan wrote that desktop publishers in an RGB-based workflow, such as those using Microsoft Office applications, will typically get a CMYK black when they output to a desktop printer.

Michael Riebesehl, iGen3 project manager at Xerox, said because the iGen digital press prints differently, the blackest black is black.

"The iGen black is excellent as 100 percent black-only black, which is counterintuitive to offset printing or even other tandem drum printing. iGen3 uses a single image carrier for all four colors," he said.

"So, by the nature of the way we build one color on top of another and black going down last on this image build belt, you end up getting a less dense black as you increase color underneath."

But this is the exception to the rule. Riebesehl said their other digital presses, such as a DocuColor 8000, use four drums, and a rich black would put down a denser black.

Caution

While a rich black can improve a design, care must be taken. Used incorrectly, it can create a host of horrors such as fuzzy type, wet pages, wrinkled paper, ghosted images, sticking, rub-off, and most insidiously, paper breakdown where the wet paper just comes apart.

The best way to avoid drenching the paper with ink is to find out the total ink limit for a print job. Because multiple factors such as paper quality, ink and printing method will determine the total ink limit, the best way to find out is to call the printer.

Next Page: Understanding the process helps avoid ugly messes on the press.