In the article “RGB or CMYK, which and when?” we described the main differences between the two color models, briefly dwelling on some characteristics of the four-color black. Today we will further explore the topics by clarifying the difference between rich black and plain black.
Process color printing
Process color printing (CMYK) is a printing model that uses 4 basic ink colors: Cyan, Magenta, and Yellow are the three primary colors of subtractive synthesis, while black (Key Color) is an addition made for technical reasons. In principle, we should be able to get black by combining the three primary colors at 100%, but the print result is a very dark gray instead, not even close to an absolute black. Black ink was thus added to achieve a complete full-color printing.
By balancing each pigment, in a percentage ranging from 0 to 100, it is possible to create all the other colors of the CMYK color space.
However, it’s important to know that some inkjet printers work only in tri-color (CMY) and therefore get their black by mixing the three primary colors at 100% each. An example is the HP® Photosmart printer.
Black in print
As mentioned above, the sum of C, M, and Y, at 100%, should generate black, but the result is actually a shade of deep brown known as composite black. Similarly, the black made only of K = 100% does not correspond to the rich black to which we are visually accustomed, which is “enriched” by the addition of a percentage of the other 3 colors.
Plain black made of C = 0, M = 0, Y = 0, K = 100. You should always use this black for texts, threads, and small elements, preferably with overprint enabled. Overprinting is necessary to avoid the appearance of unsightly white holes on the edges of the various graphic elements in the event of printing sheet misalignment. We do not recommend using rich black for these elements because, with misregistration, this could cause a bothersome visual splitting because of the misalignment of the various colors.
Using plain black for solid backgrounds or for big graphical elements, however, is not appropriate unless you intentionally want to achieve a “faded black“. This happens because the paper absorbs part of the applied ink, which in turn looks faded and not saturated enough. The paper you use also plays a huge role, but the resulting color is usually a very dark gray, not always uniform. For these bigger elements, an “enriched” black is advisable.
To get a full and deep black it is necessary to combine the 4 CMYK colors in percentages. Depending on the color scheme, it is possible to achieve warm, cold or neutral blacks. There is no set combination of ink colors to get rich black; the colors can be balanced according to the desired final effect.
The most common and widely used rich black is made of: C = 63, M = 52, Y = 51, K = 100. This color owes its popularity to Adobe Photoshop® software, which is why it is also known as Photoshop® black. These are in fact the percentages you get when automatically converting RGB black (R = 0, G = 0, B = 0) to CMYK using the Photoshop® factory settings.
Cool black is generally achieved by setting C = 60, M = 0, Y = 0, K = 100; while a warmer variant can be created by using the following percentages: C = 0, M = 60, Y = 30, K = 100.
Neutral black, on the other hand, has variable percentages that are generally chosen based on the printing technology used. For boxes made with Packly, we recommend using the following color percentages to get a deep and uniform black: C = 40, M = 30, Y = 0, K = 100.
Whatever your color choice, the different percentages that make up black print, when added together, must not exceed 300% of ink coverage. Greater coverage could compromise the quality of the final product.
In the article “Packaging and graphic design: tricks of the trade” we explain: “The different inks are placed on the print sheet, overlapped, according to a specific arrangement of color dots (regulated by specific patterns). The percentages for any color will define the dimension of various points.
The ink placed should then dry off. In this step, we will run across into the first issue: creating colors (especially the dark ones) whose CMYK amount exceeds 300% may result in different print problems, both while spreading the color and drying it off. The print support, in fact, soaked in pigments may tear off, get dirty, etc. … “
The only exception is the “registration black” which is always composed of C = 100, M = 100, Y = 100, K = 100, and, therefore, from 400% coverage of the inks. This color is used only for register signs such as marks. and should never be used for other graphic elements.
Video display vs. press
An often underestimated issue is that all these blacks look similar on almost all monitors, except for the professional devices calibrated for the correct color display. On common monitors, in fact, they are represented as absolute black (R = 0, G = 0, B = 0), while if applied on the various printing materials they preserve their specific characteristics. In the table below we intentionally stressed the chromatic difference between the various colors only for explicative purposes: the colors displayed on the screen do not reflect the actual final print result.
During the design of projects intended for print, you must remember to set the document’s color model as CMYK and pay particular attention to the color percentages to avoid the printing problems listed above. If you do not know which color result is best suited to your needs, you can always opt for a print test of different blacks and compare them.
To start, download our handy table to always have the most used color percentages at your fingertips!
The blacks displayed do not reflect the actual final print result.