Trapping by overprinting


    For more precise control of trapping and for trapping complex objects, you can create the effect of a trap by stroking an object and setting the stroke to overprint.

To create a spread or choke by overprinting:

  1. Select the topmost object of the two objects that must trap into each other.
  2. In the Stroke box in the toolbox or the Color palette, do one of the following:
    • Create a spread by entering the same color values for the Stroke as appear in the Fill box. You can change the stroke's color values by selecting the stroke and then adjusting its color values in the Color palette. This method enlarges the object by stroking its boundaries with the same color as the object's fill.
    Illustration of Object stroked with fill color with these callouts: A. Overprinted stroke creates spread trap B. Fill creates knockout C. Area of trap D. Area of knockout
    Object stroked with fill color A. Overprinted stroke creates spread trap B. Fill creates knockout C. Area of trap D. Area of knockout
    • Create a choke by entering the same color values for the Stroke as appear in the lighter background (again, using the Color palette); the Stroke and Fill values will differ. This method reduces the darker object by stroking its boundaries with the lighter background color.
  3. Choose Window > Stroke.
  4. Illustration of Object stroked with background color with these callouts: A. Overprinted stroke creates choke trap B. Fill creates knockout C. Area of trap D. Area of knockout
    Object stroked with background color A. Overprinted stroke creates choke trap B. Fill creates knockout C. Area of trap D. Area of knockout
  5. In the Weight text box, enter a stroke width of between 0.01 and 1000 points. Check with your print shop to determine what value to use
  6. For example, a stroke weight of 0.6 point creates a trap of 0.3 point. A stroke weight of 2.0 points creates a trap of 1.0 point.

  7. Choose Window > Attributes.
  8. Select Overprint Stroke.

To trap a line:

  1. Select the line to be trapped.
  2. In the Stroke box in the toolbox or the Color palette, assign the stroke a color of white.
  3. In the Stroke palette, select the desired line weight.
  4. Copy the line, and choose Edit > Paste in Front. The copy is used to create a trap.
  5. In the Stroke box in the toolbox or the Color palette, stroke the copy with the desired color.
  6. In the Stroke palette, choose a line weight that is wider than the bottom line.
  7. Choose Window > Attributes.
  8. Select Overprint Stroke for the top line.
  9. Illustration of Copy of stroke used for spread trap with these callouts: A. Overprinted top stroke creates spread trap B. Bottom stroke creates knockout C. Area of knockout D. Area of trap
    Copy of stroke used for spread trap A. Overprinted top stroke creates spread trap B. Bottom stroke creates knockout C. Area of knockout D. Area of trap

To trap a portion of an object:

  1. Draw a line along the edge or edges that you want to trap. If the object is complex, use the Direct Selection tool Direct Selection tool to select the edges to be trapped, copy them, and choose Edit > Paste in Front to paste the copy directly on top of the original.
  2. Drop shadow with a trap (left) is based on the line drawn where the object and its drop shadow meet (right).
    Drop shadow with a trap (left) is based on the line drawn where the object and its drop shadow meet (right).
  3. In the Stroke box in the toolbox or the Color palette, select a color value for the Stroke to create either a spread or a choke.
  4. If you are uncertain about what type of trap is appropriate, see About traps.

  5. Choose Window > Attributes.
  6. Select Overprint Stroke.