Tic/Tac

When several colors are printed on top of each other, there is a limit to the amount of ink that can be put on paper. This maximum total dot percentage is referred to as either TIC (Total Ink Coverage) or TAC (Total Area Coverage).

When a designer ignores this technical limitation, the ink that gets laid down last won’t attach properly to the previous layers, leading to muddy browns in neutral areas. The ink also won’t dry properly on the press sheets. This can cause set-off where the ink of a still wet sheet rubs off on whatever is stacked on top of it.

Specifications for total ink coverage

Ink coverage is specified as a percentage: using 100% of each process color (cyan, magenta, yellow and black) equals 400% TIC. The actual maximum that is acceptable depends on a number of parameters:

  • the printing process: digital, sheet offset, web offset (heatset or non-heatset),…
  • the paper stock (coated or uncoated,…)
  • the speed at which the press runs
  • how many colors are printed simultaneously (since intermediate drying time is important)

To know the TIC that the printer can handle, it is best to consult with them. The following percentages are industry averages:

  • Sheetfed offset on coated paper (typical commercial printing jobs): 320 to 340%
  • Heatset web offset (such as magazines): 300 to 320%
  • SWOP: 300%
  • Non-heatset web offset on uncoated paper (such as newspapers): 240 to 260%

I haven’t found much information on inkjet devices or copiers but in general these systems seem to be able to handle values between 300 and 350%.

How to avoid exceeding total ink coverage

One error that is frequently made is to use the ‘registration’ color for design objects. Since registration equals 100% of each separation, the total ink coverage is always exceeded when this color is used. Never use ‘Registration’ for design elements.

Incorrect separations settings in Photoshop are also a possible reason why images are ‘too heavy’. The default color settings of Photoshop are optimised for web coated paper.

Another easy way to cause TIC related issues is the inappropriate use of overprint.

How to check total ink coverage

InDesign has a Total Ink Coverage indicator in the Separations Preview window.

There are preflight tools that can check total ink coverage. Keep in mind that some of these applications, such as Enfocus PitStop, only check vector objects and don’t check within images or take overprints into consideration.

Recent versions of Adobe Acrobat Professional have a ‘Total Area Coverage’ setting in the Output Preview settings. You specify a treshold value and any area within the PDF that exceeds this value is highlighted.

Similar functions are offered by several prepress systems, which can check complete press sheets for any TIC related issues.

More information

To discuss TIC, check this thread on the B4print forums.

2 Comments to “Tic/Tac”

  1. Matt Beals, on February 26th, 2008 at 12:27 am Said:

    PitStop Pro most certainly checks ink density in images. You can specify the area of calculation for averaging.

    FlightCheck Pro can report the ink density but it streams each individual pixel with no ability to average.

    But in order to truely calculate the ink density and take into consideration stacking order and over prints you have to have a RIP to perform that function.

  2. Laurens, on February 26th, 2008 at 3:56 am Said:

    You’re right Matt, thanks for the correction. I overlooked the fact that PitStop 7 can indeed check ink densities in images. I have updated the page content.

    Just to be on the safe side, I doublechecked if this release can preflight ink densities in overprints but that still isn’t true. Funnily enough both InDesign and Acrobat 8 Professional warn about a 100% black text in overprint on 100% CMY but PitStop cannot check this. I remember a discussion in the Ghent PDF Workgroup about this in which the required CPU overhead was cited as the main restriction for not doing this type of check.

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