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).
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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.
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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.
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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.