UCA (UnderColor Addition) In process color printing, used with GCR, UCA is ink added in shadow areas to increase color saturation.

UCR (UnderColor Removal) In process multicolor printing, color separations are reduced in color in neutral areas where all three colors overprint and the black film is increased an equivalent amount in these areas. This improves trapping and can reduce makeready and ink costs.

UGRA test target A measure of image resolution and dot size on plates and in printing. UGRA is the Swiss Association for the Promotion of Research in the Graphic Arts Industry.

Unit In multicolor presses, refers to the combination of inking, plate, and impression operations to print each color. A 4-color press has four printing units each with its own inking, plate, and impression functions.

UNIX A multiuser, multi-tasking operating system that runs on a wide variety of computer systems from personal computers to mainframes. UNIX was written in the C programming language. It is the most common operating system for servers on the Internet.

up In printing, two-up, three-up, etc., refers to imposition of material to be printed on a larger size sheet to take advantage of full press capacity.

Uppercase Capital letters in type.

UV inks Solventless inks that are cured by UV radiation. They are used extensively in screen printing, narrow web letterpress, and flexographic printing.