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In recent jobs, I have skewed away from pre-mixed rich black formulas in favour of making a black that fits dominant colours in the publication. For example, in a publication with a dominant full magenta colour scheme, I used a pure magenta rich black (C0 M100 Y0 K100) and the results came out great.

In a current job, I have a dominant green that is C50 M0 Y100 K15. To create a fitting rich black for this identity, my first impulse was to add half the cyan and Yellow values to the existing 100% black. That yields C25 M0 Y50 K100. Is that too light?

My question is: how much ink, in percentages, should I add to the 100% to at least have a satisfying rich black? How 'wet' should a good rich black be?

Edit: I understand all that is said in What kind of black should I use when designing for CMYK print? and I'm applying most of it. None of the answers to that question specify how much ink a rich black should have at minimum to be a rich black; to avoid the pale, translucent black of 100K.

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There is no answer to your question as such: everything above C0M0Y0K100 is darker than process black. However, consider that 100% ink means that your printer fills the entire raster, while 25 fills only a quarter of a raster.

This means that the lower the value of your other colors the more uneven it is, so it might be perceived as grainy. So while M100 K100 is extremely even, C25 M0 Y50 K100 might appear more uneven. How grainy people perceive it is hard to say, since it depends on the medium, print resultion, raster type and distance to viewer. Most likely this is not really an issue.

However if you go for dark BLACK with a hint of undertone, then I would fully saturate the primary color and add black. Then bring it down to a 200-300% coverage range.

But then I have the option to make test prints (and sadly, the duty to clean the machine if I just get the color all over the place). So I would print a few swatches.

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Ok, I think this question is quite difficult to answer because there could potentially be many variables at play. I'm just going to concentrate on the practicalities of printing the job, so you don't upset your printer with your novel choices of mixes for rich black.

I assume, it's four colour process offset lithography.

It might depend on the press and the amount of coverage required, even the stock it's being printed on, or whether it's being UV coated, etc, etc. I worked in offset litho for many years. Sometimes the printers would nearly have a fit when they realised a certain colour mix was virtually unprintable, or would give them significant problems during the run.

For example in small offset lithographry, some smaller presses don't have quite the roller power for large areas of solid ink coverage - combine that with the actual system whether it's a full colour press, or perhaps two-colour being printed in full colour but in two passes, and therefore the possible contamination of colours in the second pass, from blanket to plate, and back into the ink.

Another possibility is that if there is too much total ink it could cause problems with drying (again depending on the stock), or even offsetting on the backs of sheets etc.

There are so many practical reasons I think I would want to ask my printer about this before just assuming that they can print it.

My advice - talk to your printer first, don't upset him!

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    I'm aware of the danger of colours being too 'wet', so I'm not planning on making any black more wet than ~250%. But do I understand your answer correctly if I interpret that small presses might not even be able to make any single ink in 100% look smooth? – Vincent Feb 27 '18 at 15:11
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    @Vincent - yes definitely don't go above that value, and yes, some small offset presses perhaps might struggle, but I'd say it's the size of the area of coverage which would probably be of more concern. Small areas not so bad. Presses such as a Heidelberg GTO or larger should be better than smaller presses. – Billy Kerr Feb 27 '18 at 16:09
  • I've used a TOK and a GTO 2. The TOK was a lot more forgiving with large black areas than the GTO. – Simon Richter Feb 28 '18 at 9:56
  • @SimonRichter Strangely/coincidentally, I used to operate a Heidelberg TOK too. That brings back memories! – Billy Kerr Feb 28 '18 at 10:52
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200%-300% Never over 400% sweet spot is ~220-250%

Generally you base the % coverage of inks off several factors.

  • Your 4-color proof
  • Paper weight being used <---Most important
  • Paper color (Cyan vs Yellow) <---Most important
  • Press limitations

Once you take all those factors into account you can make your black and run some test prints.

I don't think I have adjusted blacks ever to match the art outside of pre-press. In all my experience it's the paper color and its absorption ability that matters the most. If you build a green-tinted black but your paper is yellow it's going to look bad.

Usually a 40-40-40-100 works just fine, otherwise I go for a deeper 60-60-60-100.


However

I don't really understand why you are going about it this way, I don't see much gain from trying to create a black that mirrors it's content. The point of black is to create divides and visually break-up a piece. This is actually a bad idea that could mess-up an entire run.

If a black is enriched for no reason on small characters or graphics, the result might not look as sharp as when using a pure pure because of the misregistration. When press operators calibrate the job at the beginning of the print run, they need to adjust the 4 CMYK plates together and very precisely. That's not an easy adjustment; sometimes they don't really care if it's a low quality print place and sometimes it's their old machines that cannot keep that adjustment for the whole print run. All print shop are not equals, the human factor and investment in good machinery can have a huge impact on the print quality.

Yes I get that sometimes you need to tweak it but I don't think this should be a "standard practice" you should implement.

To create a fitting rich black for this identity, my first impulse was to add half the cyan and Yellow values to the existing 100% black. That yields C25 M0 Y50 K100. Is that too light?

That sounds about right generally you want to be within 5% of the original coverage. Here you are 6.8% so not bad but again depends on all of the other factors.


Bottom line

Check with your press operator, know your paper and know your art.

  • To answer your question about why I am doing this, please refer to this image. I love how these turned out with their custom rich blacks. – Vincent Feb 28 '18 at 12:52

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