So you have probably have heard the term “Keyline” but you have no idea what it means. Here is a quick definition and use example.
1. Keyline Defined
A Keyline is a dark, single channel color used to separate and protect knockout text during the printing process. Here is an example. In the below image the phase “Malt Beverage” is in a grey color indicating the text reversing out of the image, surrounded by a thick black line. That thick black line is your keyline.
2. The importance of Keylines
Keylines are a vital design element for any job which needs to be printed on a mechanical press. They protect the text from filling in with color and becoming illegible when the press gets out of registration. While this might sound like a function of poor printing, exactly the opposite is true. Press registration compensations are a vital part of every print job. Printing presses are giant machine that can take up entire rooms in a facility. To assume they they will remain in perfect registration during an 8 hour press run is not just wishful thinking, it is outright folly. Below is an image that has been manipulated digitally to simulate bad press registration.
Notice how ragged the letter “L” appears where the colors overlap improperly.
Below is the same image with a keyline added to compensate for the press misalignment. The black keyline has been adjusted so you can still see the layers beneath it.
The keyline, while it does not correct the registration problem, it shields the edges of the text from the unseemly effects of press drift. The lesson to take away it to put a keyline around any text that reverses out of multiple overlapping color channels.