When is black a rich black? When do you use it? Lyn Eggleston expains it
Rich black is a mixture of all four of the process colours, particularly extra cyan for a ‘cool’ rich black or extra magenta for a ‘warm’ rich black – or both – as well as 100%K. Different commercial printers usually have their own preference for what is rich black, based on knowledge of their presses, their inks and the paper being used etc. I googled rich black to see whether there was any consensus, and in one discussion I found the following suggestions for the CMYK mix: 40/40/0/100, 60/40/40/100, 65/65/50/100, 40/30/30/100, 25/25/25/100 all in in one thread. In other words, there is no one ratio for rich black. It’s usually a matter of trial and error (expensive process) which is why if it is being commercially printed, you should find out from the printer what he prefers.
Rich blacks are often used in backgrounds which are black, as K on its own is not usually intense enough and may look a bit boring or even washed out (greyish) depending on how much there is and what other colours are around it.
However, other black elements, especially text and thin strokes, should never be a rich black, as when printed, it can be difficult to get the registration of all the inks used absolutely spot-on, so there can be colour ‘halos’ around the text or lines.
Depending on your monitor, pure black on screen can look a little washed out, and presumably those settings you are referring to (which I have never even noticed) allow you to set the monitor display of black as a richer black. I would never choose the option of ‘output all blacks as rich black’ for the reasons described above. However, you could choose to ‘display all blacks as rich black’ if the appearance of 100%K on screen worries you.
To summarise, you could make a swatch called ‘rich black’ in your layout application, and apply it to those elements that you want to look really black. Bear in mind if you are printing this yourself, you will chew through the ink/toner cartridges a lot faster.
Lyn Eggleston is an Australian graphic designer currently working inhouse for a US-based dental supply company. Over the last few years, she has worked in a variety of inhouse design positions, as well as learning valuable skills being the prepess person in a small printshop. Lyn is a frequent contributor to a number of online forums on graphic design and Adobe programs.