Adjust ink options for trapping

Adjust ink neutral density values

By adjusting the ink neutral density (ND) values that the selected trapping engine uses, you can determine the precise placement of traps. The default ND values for process inks are based on the neutral density readings of process ink swatches that conform to industry standards in different parts of the world. The language version determines which standard it conforms to. For example, the ND values for the U.S. English and Canadian versions conform to the Specifications for Web Offset Publications (SWOP) solid ink density values published by the Graphic Arts Technical Foundation of North America. You can adjust process ink neutral densities to match printing industry standards in other parts of the world.

The trapping engine derives the ND values for a spot color from its CMYK equivalent. For most spot colors, the ND values of their CMYK equivalents are accurate enough for proper trap creation. Spot inks that aren’t easily simulated using process inks, such as metallic inks and varnishes, may need their ND values adjusted so that the trapping engine can trap them correctly. By typing new values, you can ensure that an ink that is observably darker or lighter is recognized that way by the trapping engine; the appropriate trap placement is then applied automatically.

You can get the appropriate neutral density value for a given ink by asking your commercial printer. The most accurate method of determining an ink’s ND value is by measuring a swatch of the ink with a commercial densitometer. Read the “V” or visual density of the ink (don’t use process filters). If the value differs from the default setting, type the new value in the ND text box.


Changing the neutral density for a spot color affects only how that color will trap. It doesn’t change the appearance of that color in your document.

Follow these guidelines when adjusting ND values:

Metallic and opaque inks

Metallic inks are usually darker than their CMYK equivalents, while opaque inks obscure any ink beneath them. In general, you should set the ND values for both metallic and opaque spot colors much higher than their default values to ensure that these spot colors won’t spread.


Setting an ink to Opaque or Opaque Ignore in the Type menu of the Ink Manager prevents an opaque ink from spreading into other colors, unless another opaque ink has a higher ND value.

Pastel inks

These inks are normally lighter than their process equivalents. You may want to set the ND value for these inks lower than their default values to ensure that they spread into adjacent darker colors.

Other spot inks

Some spot colors, such as turquoise or neon orange, are significantly darker or lighter than their CMYK equivalents. You can determine whether this is the case by comparing printed swatches of the actual spot inks to printed swatches of their CMYK equivalents. You can adjust the spot ink’s ND value higher or lower as necessary.

Customize trapping for specialty inks

Using certain inks involves special trapping considerations. For example, if you are using a varnish on your document, you don’t want the varnish to affect trapping. However, if you’re overprinting certain areas with a completely opaque ink, you don’t need to create traps for items underneath. Ink options are available for these situations. It’s usually best not to change the default settings, unless your prepress service provider recommends changing them.


The speciality inks and varnishes used in the document may have been created by mixing two spot inks or by mixing a spot ink with one or more process inks.

  1. Open the Ink Manager and select an ink that requires special treatment.
  2. For Type, choose one of the following options, and then click OK:


    Use for traditional process inks and most spot inks.


    Use for clear inks to ensure that underlying items trap. Use this option for varnishes and dieline inks.


    Use for heavy, nontransparent inks to prevent trapping of underlying colors but allow for trapping along the ink’s edges. Use this option for metallic inks.

    Opaque Ignore

    Use for heavy, nontransparent inks to prevent trapping of underlying colors and to prevent trapping along the ink’s edges. Use this option for those inks, such as metallics and varnishes, that have undesirable interactions with other inks.

Adjust the trapping sequence

The trapping sequence (also called the trapping order) matches the order in which inks are printed at the press, but it doesn’t match the order in which separations are produced at the output device.

The trapping sequence is particularly important when you’re printing with multiple opaque colors, such as metallic inks. Opaque inks with lower sequence numbers are spread under opaque inks with higher sequence numbers. This process prevents the last applied ink from being spread, and it still creates good traps.


Don’t alter the default trapping sequence without first consulting with your prepress service provider.

  1. Open the Ink Manager. The current trapping sequence is displayed in the Sequence column of the inks list.
  2. Select an ink, type a new value for Trapping Sequence, and then press Tab. The sequence number of the selected ink changes, and the other sequence numbers change accordingly.
  3. Repeat the previous step for as many inks as necessary, and then click OK.
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