In our previous blog Print Blacks Right The First Time we discussed the basics of using a combination of CMYK to create rich black colors when printing. Today we want to take things a bit further and talk about Total Area Coverage
Total Area Coverage
When there are several colors being printed on top of each other, as in when printing a rich black (c60 m40 y40 k100), there is a limit to the amount of ink that can be put on paper. When designers ignore these limitations serious issues are caused on the press; For example, the last ink that’s laid down on the paper won’t attach properly to the previous layer leading to muddy colors in neutral areas and ink that won’t dry properly, then rub off on the sheet that’s placed on top. This limitation is called Total Area Coverage (TAC) or Total Ink Coverage (TIC).
Total Area Coverage is specified as a percentage. You get this percentage by adding up the percentage values used in each color, so using (c100 m100 y100 k100) would give you a Total Area Coverage of 400%. The maximum that a printer will except will depend on several factors:
The printing process: Digital, laser, sheet offset and web offset each have their own limitations.
Paper Stock: Different papers will have their own limitations, this includes coated and uncoated.
Colors: The amount of colors being printed simultaneously will also affect intermediate drying times which will require limitations on TAC.
It’s always best to consult with your printer and discuss their TAC limitations prior to submitting work for print.
Here are the industry standards for Total Area Coverage
Commercial offset Printing: 320 – 340%
Heatset web offset (Magazines): 300 – 320%
Non-Heatset web offset (News papers): 240 – 260%
Inkjet Devices: 300 – 350%
Checking your TAC
To check the total area coverage of your design there are several options within Photoshop, Illustrator and InDesign. Today i’m only going to discuss how to preview TAC on any file using Adobe Acrobat.
Start by exporting your files as a PDF.
Open the PDF using Adobe Acrobat and use the Output Preview option to preview the TAC based on your selected value.
In the example above we have taken the image on the left and used the Output Previewer on the right to highlight all the areas with a TAC higher than 300%. As you can see Adobe Acrobat highlights in green all the areas with a total area coverage of more than 300%. If we refer to our industry standard we can see that this image would work fine if being printed on a magazine but could cause a potential over-inking problem if printed on newspaper.
In this case if we where planing on printing on newspaper we would adjust and reduce the black color percentages to meet the printing standards. If we where planing using commercial offset printing we would adjust and increase the the black color values since we have more ink available to us to create a nicer rich black color.