Black is not one colour in print
On screen, black is black. In a print file it can be at least four different things, and choosing the wrong one is one of the most common reasons an online print order comes back looking different from the proof. Text that looks grey and washed out, a background that shows faint banding, a page that took an extra day because the file failed preflight: all three usually trace back to how black was defined in the file.
This guide covers the four kinds of black you will meet, when to use each, and how to set them up in the software most people order print from. It applies to anything printed in CMYK, which means almost everything you can order online: flyers, brochures, booklets, business cards, posters.
The four blacks
100K (plain black)
Cyan 0, magenta 0, yellow 0, black 100. This is the black you get when you type black text in InDesign or Illustrator with default settings. It prints as a single ink, which makes it sharp and forgiving: if the press registration is a fraction off, nothing shows, because there is only one plate involved. On a digital press the same logic applies to the four toners.
Its weakness is density. Printed 100K on its own is a dark charcoal rather than a deep black, and next to a photo or a rich colour it can look slightly flat. That does not matter for body text. It matters a great deal for a large black background.
Rich black
Black with other inks underneath it. A common recipe is C60 M40 Y40 K100; a slightly cooler one is C70 M50 Y30 K100. The extra ink makes the black visibly deeper and more even across a large area. Use it for solid backgrounds, big display type, and anything larger than about a fingernail where black needs to look genuinely black.
The catch is coverage. Total ink coverage (the sum of the four percentages) should usually stay under about 300 percent on coated stock and lower on uncoated. C60 M40 Y40 K100 comes to 240, which is safe. C100 M100 Y100 K100 comes to 400, which will smear, take forever to dry and may be rejected at preflight.
Registration black
C100 M100 Y100 K100. It exists for one purpose: crop marks and registration marks that need to appear on every plate. It should never be used for anything inside the trim area. If you see registration black in a swatch panel, leave it alone.
RGB black
R0 G0 B0, or any black created in a document that is still in RGB mode. When this is converted to CMYK at the printer, it usually becomes a four-colour mix that is not quite what anyone intended, often around C75 M68 Y67 K90. It prints, but small text set in it can look soft, and the result varies from one converter to the next. Convert your document to CMYK before you set up blacks, or at least check what the black became after conversion. Our guide on exporting a print-ready PDF walks through that step.
Which black where
| Element | Recommended black | Reason |
|---|---|---|
| Body text, captions, small type | 100K | Sharp edges, no registration risk |
| Headlines above roughly 24 pt | Either; rich black if next to dark imagery | Large type shows density differences |
| Solid background panels | Rich black | 100K looks grey over a large area |
| Thin rules and borders | 100K | Multi-ink lines can show colour fringing |
| Black in photos | Whatever the image profile produced | Do not edit; the profile handles it |
| Crop marks | Registration | Must appear on every plate |
Overprint and knockout
When black sits on top of another colour, the file has to decide whether the black knocks out the colour beneath it (leaving a white hole that the black then fills) or overprints (the black is printed on top of the colour). For 100K text on a coloured background, overprint is what you want. It means a tiny registration shift produces no white halo around each letter.
Most layout software overprints 100K text by default, but only if the swatch is actually 100K. A black that is C1 M0 Y0 K100 because someone nudged a slider is treated as a colour, will knock out, and can show hairline white gaps around small type. Keep text black at exact zeros.
Rich black should generally knock out, not overprint, because overprinting a four-ink black on a coloured background pushes total coverage past the safe limit.
Setting it up in common software
- InDesign and Illustrator: the default [Black] swatch is 100K. Create a separate swatch named "Rich Black" with your chosen recipe and apply it deliberately. Turn on Overprint Preview (View menu) to see what will actually happen on press.
- Photoshop: images stay as they are. For flat black areas built in Photoshop, check the Info panel readings on the black and adjust with a Curves or Selective Color layer if it is not what you want.
- Affinity Publisher and Designer: the same pattern as InDesign. Note that Affinity's default black in a new CMYK document may be a four-colour black; check the swatch values.
- Canva, Word, PowerPoint: these work in RGB and offer no control over black. Expect a converted four-colour black. It is acceptable for flyers and posters; for small body text in a booklet, the result will be a little softer than a 100K black. If the job matters, ask the print shop to convert text to 100K at preflight, which most can do.
Checking the file before you upload
Open the exported PDF in Acrobat and use Output Preview (Print Production tools). Hover over your blacks and read the CMYK values. Turn on the Total Area Coverage warning at 300 percent and look for highlighted areas. Switch separations on and off: your body text should disappear when you hide the K plate and stay invisible on the other three. If it shows on cyan, the text is not 100K.
If you do not have Acrobat, the free preflight in most online print upload systems will flag ink coverage over the limit, and a quick test is to zoom to 800 percent on some body text: a four-colour black shows faint coloured fringing at the letter edges, a 100K black does not.
Printing with correct blacks through our service
Every file uploaded for our digital printing service goes through a preflight that reports total ink coverage and flags RGB content before the job is confirmed. If your body text has come through as a four-colour black from an office application, we can convert it to 100K on request; if a rich black exceeds safe coverage for the stock you chose, we tell you before it prints rather than after.
For jobs where the black matters, such as a black-background brochure or a book with dense text, ordering a single printed sample is the surest way to see what you will get. Our colour printing page lists the stocks and their coverage limits, and if you are unsure which black your file contains, send it over and we will check it before you place the order.
