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Before we look closely into what rich blacks are and how they
are used effectively in printing, we need to establish one fact;
black printing ink is not totally 100% black. Well, yes, technically
it is, but it could be blacker.
I can hear some of you say, “You can’t have a colour blacker
than black”. Well actually, yes you can, it’s called a rich black.
Try this easy little experiment, it just about highlights exactly
what I mean.
Take a piece of white paper and with a thick black marker pen
draw and colour in a square about 50mm x 50mm. The resulting
image should be a black square - no arguments there.
Now, take a blue or a red marker and draw a thick cross
through the square, even though you have drawn the cross on top
of a solid black image you still should be able to clearly see the
cross where it passes through the black.
Why? Because you’ve just simulated the effects of a rich black.
Because the marker pens are transparent just like printing inks, the
second colour makes the black denser or ‘richer’.
Printing inks act very similar to watercolour paints, lay one
colour on top of another colour (blue and yellow for instance) and
you get green, lay any colour on top or underneath black and you
get a darker or richer black.
How and when to use rich blacks?
There are a couple of situations in printing when using rich blacks
instead of a flat black is highly recommended, so learning the
following techniques is a powerful tool to master.
Remember, printing inks are transparent, with this in mind
take a look at figure 7.7. In this example the black letter ‘S’
and the ‘black panel’ are both made of 100% black and both
overprint (print on top) of the underlying image.
Look closely, you should be able to notice that where
the two black elements overlap the background, the black
is darker or denser due to the underlying colour showing