Want a solid black that's really black?
Avoid Muddy Blacks When Printing Process
Rich black refers to underprinting a screen of cyan, magenta and/or yellow below process black to make black appear richer and more opaque. Not only does it make large areas of solid black look great, it can make black type that overprints a four-color image much more legible. Rich black is an example of a production technique that invites the eye to take a second look at your printed material. It can make your printed piece stand out and draw the reader into the page.
It's Easy to Add Rich Black to Your Documents
Four color printing uses cyan, magenta, yellow and black (CMYK) inks to reproduce color images. In order to make a wide range of colors with tints, process inks are transparent. In fact, process black ink is significantly less opaque than a spot-color black for this reason.
The transparency of process black ink can cause some common printing problems including, the mottling or streaking of large solid black areas on a page, or a situation where black type, when overprinting an image or pattern, allows the underlying element to show faintly through, as if it were ghosted or screened back.
The good news: There is an easy way to prevent this problem. Instead of using just black ink in these scenarios, create a color that combines black with one or more of the other process colors. This technique, known as rich black, will increase the density (darkness) of the black area, making it appear fuller and richer.
In your page layout application, create a new color. Call it "rich black". Make sure you define it as a process color build or you will create an extra plate. "rich black" is somewhat subjective; if you use equal amounts of CMY under the black, you will not achieve a good gray balanced black. We recommend 50-40-30-100 or 50-40-35-100 (CMYK). This may especially be the case with the digital press or large solid areas on the other presses, though the size of the black area is somewhat subjective. For example, body copy does not typically require it. You also don't need to worry about "shrinking back" the CMY colors: We take care of that when we apply trapping.
An even easier method is to simply ask us to apply rich black for you (if needed). There may be a nominal fee for doing so. We try to raise a flag when rich black would be preferable, though it is difficult to catch if you supply print-ready PDFs. Please let us know if this is a concern and we'd be happy to take a look.