There are two types of black ink used in printing: standard black and rich black.
The standard black doesn't produce a really deep black color. If used in larger surfaces, they look a bit grayish. Professional designers mix another printing inks with the black ink to get what is called rich or deep black. We recommend a mixture of C=60 M=40 Y=40 K=100 (240% ink Coverage).
We avoid using Photoshop's black value (C=75 M=68 Y=67 K=90) since it goes above the maximum ink coverage of 240% resulting in a muddy looking black when printed.
When to use them
Standard black should be used for text and small areas to avoid overlapping colors. Rich black should be used for larger areas to get a darker black color.
If you have a heavy, dark, solid black bleed on 3 or 4 sides, please try to keep that design on the front side of the card and reduce the mix to 20/10/10/100 so there is less ink on the card. These cards may tend to show a slight cracking on the cut edge. Cracking of the edges of a business card sometimes occurs when the card contains high values of ink, as in dark colors. If both sides have heavy coverage, we suggest a protective coating such as Silk Lamination or Super Plush Lamination.