Exploring Printing and Prepress

Hey all! I've decided to take my blog posts a different direction and in addition to just blathering on about what I am currently working on, I'm going to use this space to further explore the technical world of design, printing and Web. In these posts I hope to offer written explanations and terms as well as provide visuals and links to more information. 

Here is my first post in my "Tech Journal" on my explorations into printing and prepress. Enjoy!

When a color project is being printed it is most often done using a four step process where four colors -- Cyan, Magenta, Yellow and Black -- are printed on top of each other in different percentages to create the final desired colors. These are called CMYK Separations.

With these four colors being put on at different times by different plates, the plates can often become out of alignment and not exactly in register. This printing out of register can often lead to white gaps between colored objects because of knocking out. 

Knocking out refers to removing the ink from underneath an object or type to keep the color of that object or type as true as it can be. 

To avoid these white gaps one of two choices needs to be made -- to stick with the knockout and use trapping or to skip the knockout all together and go with overprinting.  

Trapping -- or color trapping -- is when adjacent colors are intentionally set to overprint along their common borders. This overlap is called a trap. The placement of the trap -- whether on the inside of the object or the outside -- depends on the color of the object and the color of the background. 

In the case where the background is dark and the object is light, the the trap is placed on the outside of the object and spreads onto the darker colored background. This really just means that the overlaying object is made larger than the knockout under it. 

When the background is light and object is dark, the trap is placed inside the object and chokes the darker colored object. This means that the knockout underneath the object is made smaller.

The other option to avoid white gaps caused by being out of registration is overprinting. Overprinting is when one color is printed directly on top of another color. This can lead to issues because -- since the ink used in printing is transparent -- the color of the ink overprinted is blended with the color that it is printed over creating new or undesired colors. This is why overprinting is often reserved for black text and body copy.