Expert: Kevin Stohlmeyer - 1/7/2010

Question
I am having a hard time understanding the difference between knockout and overprinting and what they exactly do.  Can you explain the difference between them and what their purpose is?

Answer
Hi Jennifer

Knockout and overprinting are mainly used in professional printed jobs to maintain a color's integrity - not having it mix or interact with another ink.

Say you have an image that consists of a bright yellow and a dark blue. The yellow shows up on top of the blue, like a yellow circle inside a blue square.

If you choose overprinting, when the image prints professionally (offset press), not at home or digitally, the blue square would print first as a solid image and the yellow circle would print on top of it creating a greenish looking circle. Not good.

So, you could choose to knockout the circle. This would create a hole in the rectangle, so when the blue prints first, there is no other ink under the yellow circle allowing it print clean and be bright yellow.


Hope this helps.

Kevin