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 ea ...

, 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 the R ...

magenta Magenta () is a color that is variously defined as pinkish- purplish-red, reddish-purplish-pink or mauvish-crimson. On color wheels of the RGB (additive) and CMY (subtractive) color models, it is located exactly midway between red and blue. I ...

, and

cyan Cyan () is the color between green and blue on the visible spectrum of light. It is evoked by light with a predominant wavelength between 490 and 520 nm, between the wavelengths of green and blue. In the subtractive color system, or CMYK color ...

that would have added to a dark neutral (black) and replacing them with

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

ink only, called a ''Full Black'', during the

color separation Color printing or colour printing is the reproduction of an image or text in color (as opposed to simpler black and white or monochrome printing). Any natural scene or color photograph can be optically and physiologically dissected into three ...

process. Under color removal is used in four-color (or more colors) 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 shadows – which 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: Solves the ink not sticking problem and; :Advantages: Black ink is cheaper. :Possible disadvantages: Black ink by itself in a shadow may not be dark enough, so CMY colors are added (called

under color addition In four-color printing (or more), under color addition (UCA) is a technique for darkening areas of the printed image by adding colored inks. It is meant to achieve the same results as under color removal, but from a different starting position. U ...

or UCA) to make a more accurate reproduction. UCR is generally not recommended for use in printing, due to its tendency to produce dull-looking images and artwork. (The problem of "looking dull" can often be obviated on

coated paper Coated paper (also known as enamel paper, gloss paper, and thin paper) is paper that has been coated by a mixture of materials or a polymer to impart certain qualities to the paper, including weight, surface gloss, smoothness, or reduced ink absor ...

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 an ...

, 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