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ADO-1009 • Adobe Illustrator Overprinting and Choke and Spread

Topic:

Both Corel Draw and Adobe Illustrator are valuable vector programs making easy work of spot color separations but those separations by default are "always" butt registered.

Both programs work on the principle called WYSIWYG (pronounced wizzy wig) and it stands for "what you see is what you get". This means that when two shapes overlap the computer separates only what you can see and butt registers the color along their edges.

A printing press can suffer from slight registration fluctuations leaving gaps or odd over lapping that can cause unwanted effects in a print.

Resolve:

When printers don't want colors to touch they create what is called a "choke" and when they want colors to slightly overlap its called a "spread" all known as "trapping".

Corel Draw allows for auto trapping of "solid spot colors" in its print window, but its not easily controlled. CMYK colors are not handled at all. Adobe Illustrator has no such feature.

Both programs do have a feature called "over print" and it valuable to any screen printer. These features have been in the programs since they first came to market yet many still do not know they exist or how to use them properly.

Both programs have a feature that allow you to "view" the effect of the over print making it much easier to visualize what is happening.

Using the feature called "overprint" and assigning that option to a shape on screen allows the entire shape that is below it to print as a separation. No butt registration it prints full size shapes. Think about that, no more registration issues and special effects such as secondary colors and flash bases all created and printed "at the same time". No more jumping back and forth from the print window to change colors to black to print a flash base. No more making separate files for separate colors, just proper use of a program that is offering you the tools to do it right.

Now, is it super easy and the best thing you have ever used. Nope, not yet but Freehand is working on that for you. Expect new products to handle all your needs.

First, READ all the supplied documentation about these features. Open the Help menus in your program and search "overprint". Learn.

Corel keeps it feature under the Edit Menu while Adobe keeps its feature in the Attributes window located in the Window Menu.

Both allow you to overprint both "fills and stokes" (outlines).

Take two solid shapes that overlap assign over print to the top shape and you will have a secondary color on press. Less screens, more colors.

Take the same two shapes that over lap add a stroke (outline) of the same color to the top shape, assign overprint stroke (outline) not to the fill and you create a "spread". The shapes will not butt register, they will overlap just the width of the stroke (outline).

Learn this basic function and think outside the box a bit to discover many ways to put this old feature to use and improving your prints.


Need to choke (trap) your underbase color?

Create two shapes one directly on top of another both colored with different spot colors. Assign over printing to the top shape to allow the below (unseen) shape to print a separation. Stroke (outline) the bottom (base) shape with a spot color you do not intend to separate and that shape will be choked back making it slightly smaller on the edge than the above shape. You just choked the underbase, removing any press registration issues.

The exact opposite but the same result. You can do exactly the above but do not stroke the bottom shape, stroke the tops shape with the same color as the fill to make it slightly wider than the below shape. That is called a spread. By spreading one shape you have choked the other. Just another way of looking at the same problem.

 

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