printing Printing is a process for mass reproducing text and images using a master form or template. The earliest non-paper products involving printing include cylinder seals and objects such as the Cyrus Cylinder and the Cylinders of Nabonidus. The ...

, under color removal (UCR) is a process of eliminating overlapping

yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In t ...

magenta Magenta () is a purple-red color. On color wheels of the RGB color model, RGB (additive) and subtractive color, CMY (subtractive) color models, it is located precisely midway between blue and red. It is one of the four colors of ink used in colo ...

, and

cyan Cyan () is the color between blue and green on the visible spectrum of light. It is evoked by light with a predominant wavelength between 500 and 520 nm, between the wavelengths of green and blue. In the subtractive color system, or CMYK c ...

that would have added to a dark neutral (black) and leaving the

black Black is a color that results from the absence or complete absorption of visible light. It is an achromatic color, without chroma, like white and grey. It is often used symbolically or figuratively to represent darkness.Eva Heller, ''P ...

ink only, called a ''full black'', during the color separation process. Under color removal is used in '' process color'' printing. Black ink used to add details and darkness in shadowed areas is called a ''skeletal black''. With current ink technology, the total CMYK ink in the shadows refuses to stick after it reaches the dark shadows (usually above a 250% total CMYK coverage), and begins to peel off. To prevent this, printers developed UCR, in which neutral shadowswhich would have normally been produced by overprinting the four inks ''cyan'', ''magenta'', ''yellow'' and ''black'' on top of each other (high ink coverage)are replaced with the single layer of ''black''. UCR removes the color inks ''under'' the black, resulting in a single layer of ink which sticks to the sheet better, and saves on the consumption of ink. There is no universal rule for UCR. The amount required will depend on the printing press, paper, and ink in use. Advantages are that it solves the ink-not-sticking problem and that using black ink is less expensive than using several colors. A disadvantage is that black ink by itself in a shadow may not be dark enough. In this case CMY colors may be added for more accurate reproduction, this process being '' under color addition'' (''UCA''). UCR is generally not recommended for use in printing due to its tendency to produce dull-looking images and artwork. (This problem can often be obviated on coated paper by use of an aqueous coating or UV coating applied on the press or as post-press. A press-applied coating can also eliminate the ink-sticking problem.) The main exception to this rule is that where working in

newsprint Newsprint is a low-cost, non-archival paper consisting mainly of wood pulp and most commonly used to print newspapers and other publications and advertising material. Invented in 1844 by Charles Fenerty of Nova Scotia, Canada, it usually has ...

, UCR is the best way to avoid the associated ink limit and registration issues. UCR is also recommended for some specific paper stocks, depending on the coloration and texture of the paper.

See also