# OVERPRINTING:
Firstly after reading this tutorial you should also read the Trapping tutorial as they are closely related.
By default when you print overlapping colors (e.g. blue text over a yellow background) the top color (blue) knocks out or leaves a white gap in the yellow area/object underneath otherwise the two inks would combine changing the blue text to green. This white gap can cause ghosting (a unsightly white gap around the edge of the top object (see diagram A below).
Selecting an object or stroke to overprint effectively adds the colour values of the overprinted object to the layers below (e.g. blue text becomes green in diagram B). You can use overprinting to prevent knockout and Ghosting. A common use for overprinting is where black text is placed on top of an image or background colour, for other examples see "#WHERE TO USE OVERPRINTING" at the top of the next coloumn. In most other cases TRAPPING is probably the better option see the Trapping tutorial for more information.

# GHOSTING:
A unsightly white gap around the edge of the top object (see diagram A below) is created when two different overlapping colours are not trapped or overprinted. This gap is created by either the paper stretching on the printing press or miss registration. You may think that this means that your printer is not doing his job correctly, not so - it is almost impossible to perfectly align all colours given the movement and distortion that is inherit in a paper medium. Therefore printers use trapping and overprint to compensate.

# RELATED TOPICS:
See also the Trapping Tutorial

# WHY USE IT:
Use overprinting to prevent knock out (see diagram C below). If you don't the printed job will have ghosting and this will detract from your design and the overall job. (See diagram A below)

# WHERE TO USE OVERPRINTING
• Use overprinting when you have black text over a picture or coloured background.
• Use overprinting when the artwork does not share common ink colours see the (trapping tutorial - diagram B).
• Use overprinting when you want to create custom ink mixes when using two spot colours or instead of using the multiply effect as per diagram B.

# HERE'S HOW:
We recommend you use the overprint feature in such programs as Illustrator and Indesign to manually set your overprinting.

Diagram B below shows some blue text set to overprint on top of a yellow block of colour.

You will notice that overprinting the text causes the Cyan to mix with the yellow causing it to go green (eliminating any white gap) normally trapping would be used in this instance, so that the text didn't change colour, we have chosen to overprint the fill here for demonstration purposes (see the trapping tutorial for more details on how to eliminate ghosting with artwork that does not share common ink colours).

# ILLUSTRATOR:
1) Click Window > Attributes (to open the attributes pallet)
2) Select the text or object with the selection tool
3) With the text or object selected check the overprint fill box in the attributes pallet if your object has a stroke don't forget to set that to overprint also.
4) To view the effect of the overprint prior to printing, click View > Overprint preview.

# INDESIGN:
See Illustrator instructions above it is exactly the same.