# TRAPPING:
Trapping is a method of overlapping or adjoining two objects of different colours. When colors printed from separate plates overlap or adjoin one another (e.g. a cyan object overlaps a yellow object). It can cause small unsightly gaps between the two in the printed job (press misregistration).
To compensate for potential gaps between colours in artwork, print shops use a technique called trapping to create a small area of overlap (called a trap) between two adjoining colors.

You will need to use trapping especially when you have two objects adjoining that DON'T share any colour in common. For example if you have a 70% cyan object overlapping a 100% yellow object, these two colours have no natural overlap, thus when the job is separated into 4 plates (cyan, magenta, yellow and black) and printed there only has to be a minute amount of paper stretch or miss registration and a small white gap will appear between the two objects (see diagram A below).

Whereas if they shared a common colour this would not be needed e.g. if the yellow object was instead green (Say 100% yellow and 50% cyan) the cyan plate would carry from one object to the next. (see diagram B below)

# RELATED TOPICS:
See also the Overprinting Tutorial

# OVERPRINT:
Selecting an object or stroke to overprint effectively adds the colour values of the overprinted object to the layers below.

See Diagram B in the Overprinting tutorial.

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

Diagram C below shows some blue text with a cyan stroke (we recommend .3 of a point) over a yellow block of colour, the stroke on this text is set to overprint.

You will notice that overprinting the stroke causes the Cyan to mix with the yellow creating a thin green line (the overlap needed to prevent a white gap). This is greatly exaggerated here for effect but in practice a .3pt rule is barely visible in the finished job.

# ILLUSTRATOR:
1) Click Window > Attributes (to open the attributes pallet)
2) Select the text or object with the selection tool
3) Apply a .3 pt stroke (the same colour as the fill)
4) With the text or object selected check the overprint stroke box in the attributes pallet.
5) Click View > Overprint preview to see the overprint effect on screen.

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