If the color is jet black only black

Print jet black with CMYK

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Black ≠ black

Black is black, one might believe. In fact, with the color black, many color gradations and color moods can be achieved in printing.

The trick here: The black is not only printed with the printing color black, but also in four colors, i.e. also with the basic colors CMY (see also our color basics article). And depending on the proportions in which these colors are represented in black, the black appears completely different. From greyish, flat and matt to strong and opaque and deep. It is also possible to set color casts with this method.

Black in theory: light and body colors

First some theory in a nutshell: Monitors and many other display devices work with the light colors red, green and blue (RGB). If you add these three light colors in equal parts, the result is the color white. The complete absence of these three colors, in turn, results in the color black. Since you have to add the basic colors to produce a white, we also speak of the additive color mixing.

Light colors are always self-luminous. In other words: These do not need any additional light source to make colors visible. With light colors, larger color spaces can be represented than is possible in print.

Monitors, scanners, televisions, cameras, etc. work with light colors. These light up actively. No further light sources are therefore necessary to make light colors visible.

In printing, on the other hand, we work with so-called "body colors" in the four basic colors CMYK (C = cyan, M = magenta, Y = yellow and K = key, key corresponds to black). The body colors are also called object colors. In contrast to the light colors, these colors are not self-luminous.

Body colors or object colors therefore always require a light source in order to become visible. You can easily try this out in a small experiment: Take any printed matter in your hand and turn off all the lights in your room ...

The K in CMYK stands for Key = key color

The complete absence of body colors gives the color white. Then only the color of the paper can be seen. Because colors are subtracted in this model to produce white, this process is also called subtractive color mixing.

Some printing processes work with more than four basic colors. This enables larger color spaces to be displayed.

In theory, we don't need the color black for printing. Because by mixing the three colored printing inks, it should actually be possible to display a sufficiently dark and high-contrast black. In practice, however, the situation is different, because if we print the three bright process colors cyan, magenta and yellow in equal parts on top of each other, the result is a dirty black that easily migrates to brown. Only when you add the key color black does a really dark, opaque black emerge. So we use the key color black in order to be able to print dark, opaque areas in combination with the process colors. The black also helps to represent neutral gray tones in the print.

A gray built up by chromatic colors tends to have color casts.

Black is not always black, because if you only use the key color for printing, the result is a flat, dark gray. The lack of saturation in black is particularly noticeable in larger areas.

Black in (printing) practice: achromatic black and deep black

If you only use the key color, i.e. black, then we are talking about an achromatic black. That is also logical, because the bright colors cyan, magenta and yellow are not represented. The black is therefore achromatic and is printed with a color application of a maximum of 100 percent.

If you add the bright colors, we're talking about one Jet black or from one colorful black. So you also use the colorful process colors cyan, magenta and yellow to create a dark, opaque black in the print.

The respective proportions of the individual colors play an important role. The mixing ratio determines how the black looks after printing. The higher color application with deep black also results in a higher color density, which in turn leads to a richer color tone.

We call a black that is represented by the four basic colors CMYK Jet black, colorful black or bold black.

In theory, for a really deep black, you could print all of the colors 100 percent on top of each other. This results in the following color application: C100 + M100 + Y100 + K100 = 400%. However, such a heavy application of paint leads to problems in practice, because the drying of the paint is disturbed by the high paint application. This can lead to the following problems, among others:

  • Lay down: When filing, the paint, which has not yet completely dried through, is transferred to the back of the following sheet. So there is a flaw in the sheet below and soiling in the sheet above.
  • Blocking: When blocking, the printed sheets adhere to one another. The sheets can no longer be separated ("singled out") and cause problems in further processing.

The maximum amount of paint depends, among other things, on the paper and the printing process. In offset printing, a maximum ink application of up to approx. 350% can be achieved. With digital printing we are at approx. 330% and newspaper printing can only cope with approx. 240% color application.

Do not exceed the maximum permissible application of paint for the colored structure

These are maximum values, which in turn depend on the substrate. Open-pored offset papers, for example, can withstand a maximum application of paint of approx. 300%, with coated picture printing papers we also recommend a paint application of 300%, in individual cases - and ideally after consulting the printer - up to 330%.

The maximum amount of paint also depends on the drying time. We therefore recommend a paint application of a maximum of 260% for flash jobs.

There are no general recommendations for using the mixing ratios. Every printer makes his own experiences and passes them on accordingly. The following values ​​have established themselves at diedruckerei.de:

  • Our recommendation: C40 M20 Y20 K100
  • Cold jet black: C30 M0 Y0 K100
  • Warm jet black: C0 M50 Y20 K100

If you want to achieve a certain color mood, you can change the proportion of individual colors. More magenta makes the black look a little warmer. If you increase the amount of cyan, the black will be cooler.

The perception of color moods is a subjective perception and also depends on the color of the paper and the lighting conditions. It is therefore not possible to make generally valid statements at this point.

 

If you would like to see other color mixtures on the screen, we recommend our article on CMYK colors.

Open-pored offset papers absorb a lot of ink. An achromatic black looks flat and gray faster here than on picture printing paper.

Positive writings

As Positive fonts one describes dark fonts on a light background, so to speak the "standard text". This will usually always be achromatic, so printed with a pure black. With small elements, the contrast is large enough and the black is perceived as deep black. However, there are other advantages if you structure fonts achromatic:

  • The font is very sharp. This is not always the case with a bright black, since with small elements a precisely fitting overprint of all colors in offset printing cannot be guaranteed. This is known as “register inaccuracy” - the fonts appear washed out. An effect that is very annoying and exhausting, especially when reading longer texts.
  • The ink and printing plate consumption is reduced. That protects the environment
  • and saves printing costs, as fewer printing plates are required (but usually does not apply to collective printing).

For large fonts that are often used for banners or as decorative elements in printed matter, we recommend deep black made up of the colors CMYK. In the case of large areas, an achromatic black would appear flat and low in contrast.

In digital printing, inaccuracies in the color structure are less of a problem than in offset printing.

Negative fonts

If fonts are displayed negatively and framed by a black area, this area should be made up of colors. However, this assumes that the negative font is not too small. Otherwise it can become illegible. This effect always depends on the font style and the paper. Coated papers allow smaller negative fonts than open-pored papers. In general terms, a negative font should not be smaller than 6 pt.

Lines are the same as fonts. The smaller the area, the sooner you should build up the black achromatic.

Jet black for graphics

It gets tricky with graphics like logos and illustrations. Here, too, no general statement can be made. The decision between a deep black built up in CMYK and an achromatic black depends on the following factors:

  • Printing process
  • Size of the black elements in the graphic
  • Size of the graphic
  • Paper / print substrate
  • Drying time

In digital printing, register inaccuracies are less of a problem. Therefore, even small graphics can be created in digital printing with a deep black.

In offset printing, we advise against using deep black for small graphics. The larger the black area, the more suitable a deep black is. With large areas and short drying times in offset printing (conventional drying), deep black can still lead to problems.

Conclusion: print jet black with CMYK

Black is not always black. Once the individual requirements for your print job have been defined, you can make a decision regarding the black build-up. In this way you can achieve the technically feasible black, influence the color mood and prevent problems in the printing process.

  • Use jet black for ...
  • large black areas
  • great fonts
  • great graphics
  • the black for negative fonts (white text on a black background)
  • Do not use jet black for ...
  • small graphics in offset printing
  • normal running texts (black text on a white background) and fine lines
  • Print layouts that are prone to register inaccuracies (this applies particularly to offset printing)

Regardless of whether you use a colored or achromatic black, you want to guarantee a high level of color accuracy and reproducibility of your colors. This is where color management comes into play. You can find out what this is all about in our article on color management.

Credits:
Text tutorial and graphics by print producer Marko Hanecke.