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• Normally, they are made to be transparent. Even
so-called "opaque" inks may need two passes through the press before
100 percent opacity is achieved.
• They overprint one another while the colors are still
wet. The adhesion of one wet ink to another is called "trap."
• They give a glossy appearance when dry. Darker colors
tend to be glossier than lighter ones. Laying down more ink increases
gloss.
• Paper has more of an effect on ink gloss than does the
ink itself. Uncoated papers absorb ink, making them look dull.
Supercalendered and coated papers cause inks to dry on the surface of
the sheet, heightening their luster.
• Heatset drying also increases ink gloss.
• Ink is thick--as thick as honey. Every time a color is
changed on press, the press has to be washed down with rags and
solvents to remove all traces of the old color. Press washups take time
and cost money. The customer whose job requires the ink change pays for
the washup.
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