UCA (Under Color Addition):

A technique that increases the saturation and vibrancy of an image by adding cyan, magenta, and yellow inks to areas where a lot of black ink is printing. The result is more vibrancy, but higher total ink coverage.

UCR (Under Color Removal):

Removing excessive densities of cyan, magenta, and yellow in neutral shadow areas to allow for more press controllability without plugging up the shadows.

UGRA Wedge:

Special filmstrip control device that is about 1 inch by 6 inches in size and contains test targets for controlling accurate film exposures on contacts and printing plates. UGRA is a graphic art research association located in Switzerland.

Ultrasonic Cleaning:

Vibrational frequencies slightly higher than those audible; used to agitate immersion cleaning tanks. Microbubble formation in the liquid accelerates dislodgement of soils.

Uncoated Paper:

Paper that has not been coated with clay. Also called offset paper.

Undercolor Removal:

Technique of making color separations such that the amount of cyan, magenta and yellow ink is reduced in midtone and shadow areas while the amount of black is increased. Abbreviated UCR.

Under Correction:

Insufficient color correction made to compensate for the hue errors of process inks. The result is a reproduction that appears to have one or all hues contaminated with the wrong color. The reproduction will print to dark; the colors will appear to warm or dirty. Under correction is the opposite of over correction.

Undercolor Addition:

A technique that is used to add cyan, magenta and yellow printing dots in dark neutral areas in the reproduction.

Under-run

Production of fewer copies than ordered. See over run.

Undertone:

The color of a thin film of an ink on a white background. The appearance of an ink when viewed by light transmitted through the film. The undertone of a transparent ink approximates its printing tone on white paper.

Uniform Color Space:

A 3-dimensional color space in which all pairs of colors that are judged to be equally different are separated by nearly equal distances.

Universal Copyright Convention (UCC)

A system to protect unique work from reproducing without knowledge from the originator. To qualify, one must register their work and publish a (c) indicating registration.

Unsharp Masking:

The process of electronically evaluating an original to determine where image edges appear. By reducing the density on the light side of an edge, the apparent edge contrast and the picture detail in the reproduction are increased through the separation filters of a color.

Up:

Term to indicate multiple copies of one image printed in one impression on a single sheet. "Two up" or "three up" means printing the identical piece twice or three times on each sheet.

USEPA:

The United States Environmental Protection Agency. USEPA is a governmental arm responsible for regulating environmental issues on land, waterways, and air.

UV Coating:

Rapid drying coatings containing monomers, which respond to ultraviolet light exposure.

UV Resistance:

The resistance to the fading of colors under direct sunlight.

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Valence:

A number representing the proportion in which a given atom or radical combines. This number usually represents the number of electrons involved in the shift of an element from one reaction state to another.

Value:

A density or numeric assignment of a color, tone or density made by direct comparison or by use of a densitometer. Color printing values range from 2% minimum controllable dot to 98% maximum controllable dot. Values in color can be pre-selected for density, hue and depth by using a process printing guide. This is ideal for pre-visualizing how a particular color may be reproduced on a printing press.

Variability:

Changing data on one or more impressions of a print job to enable some change in data depending on audience segment.

Varnish:

(1.) A transparent liquid coating that is applied to a printed product to either protect it or make it visually more pleasing. Varnish can be either matte or glossy and is sometimes only applied to certain elements of a page to make them stand out. (2.) The vehicle or "carrier" component of an ink, more commonly used in offset terminology.

Vector:

A generic name for saving picture information. Vector files are saved by recording the positions of the points that define a shape filled with one color. PostScript describes images as vector information, allowing you to translate Postscript into linework. These formats are also called “Resolution Independent” meaning that they can be redrawn at any size and still have clean edges.

Vehicle:

One of the basic components of ink. Vehicles carry the colorant and keep it dispersed throughout the printing process. The vehicle is composed of binder and solvent.

Vellum:

A fairly even uncoated paper finish.

Verso:

The left-hand page opposed to the recto. The verso always carries an even numbered folio. Also refers to the reverse side of the sheet.

Vertical Adjustment:

Raising and lowering mechanism to position blade for size cylinder being used.

Vickers:

A hardness scale representing the degree of deformation of a material when subjected to a specific diamond stylus carrying a given load for a certain length of time.

Viewing Booth

A enclosed area with controlled lighting that is used in graphic arts studios, service bureaus, and printing companies as a stable environment for evaluating proofs and press sheets. Viewing booths are generally illuminated using graphic arts industry-standard D65 lighting, and are surfaced in neutral gray colors.

Vignette:

(1.) A gradation change of only one color that varies only in strength or lightness. (2.) An illustration or image that gradually fades away, blending into the unprinted paper. It is sometimes referred to a graduated background tone.

Viscometer:

An instrument used to measure the viscosity of a liquid.

Viscosity:

A fluid's resistance to flow, varying with temperature, agitation or rate of flow.

Visible Spectrum:

Light that is visible to the human eye and is perceived as different colors. The visible spectrum is the 400- to 700-nanometer portion of the electromagnetic spectrum, which is the entire range of wavelengths from gamma rays to the longest radio waves. Infrared wavelengths are longer, and ultraviolet wavelengths are shorter than the visible spectrum.

Volatile Air Compound (VOC):

An air compound that has the property to readily vaporize at a relatively low temperature.

Volatility:

The ability of a material to readily vaporize at a relatively low temperature.

Volcano:

Printing imperfection resembling the crater of a volcano, generally noticed in heavily inked areas; caused by solvent vapors having burst through and shattering the surface of the ink film.

Volt:

The unit of electromotive force, or difference in potential, which will cause a current of one ampere to flow through a resistance of one ohm.

Voltage Efficiency:

The ratio, usually expressed as a percentage, of the equilibrium reaction potential in a given electrochemical process to the bath voltage.

Voltmeter:

Coulometer. A device used to measure voltages.

Volumetric Analysis:

A method of analysis that depends upon measurement of the volume of standard solution consumed in a titration.

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Washup:

To clean ink and fountain solutions from rollers, fountains, screens, and other press components.

Waste:

Unusable paper or paper damage during normal makeready, printing or binding operations, as compared to spoilage.

Water Break:

The appearance of a discontinuous film of water on a surface signifying non-uniform wetting and usually associated with surface contamination.

Watermark:

Translucent logo in paper created during manufacturing by slight embossing from a dandy roll while paper is still approximately 90 percent water.

Watt:

An energy rate of one joule per second, or the power of an electric current of one ampere with an intensity of one volt.

Wave:

A physical activity that rises and then falls periodically as it travels through a medium.

Wavelength:

Light is made up of electromagnetic waves; wavelength is the crest   (peak)-to-crest distance between two adjacent waves.

Wear-In (Seat):

Break in a rotating doctor blade by applying pressure against cylinder without printing to wear in the blade.

Web:

Material to be printed and/or processed in roll form. Common web materials include paper, film, foil, nonwovens and textiles.

Web Break:

Split of the paper as it travels through a web press, causing operators to rethread the press.

Web Gain/Growth:

The deformation of the paper printed on a web press. The physical deformation occurs as the paper absorbs ink and water and is accelerated with pressure and tension. Factors contributing to web growth include: the type of press, press configuration, paper stock, humidity, ink coverage and the conditions of the blankets. Web width changes also happen with wide-web flexo and gravure. With flexo and gravure presses that have inter-unit hot air dryers, the web width will shrink as it goes through the press because of the moisture loss of the paper due to the hot air drying. Web growth in the web-width direction was called fan out. Fan out rollers or spiral taped rollers help minimize this problem. Some web presses used a Fife system or series of "S" rollers to minimize the problem.

Web Guide:

Device that keeps the web traveling straight or true through the press.

Web Press:

A high-speed press that prints on both sides of continuous rolls (or webs) of paper. Often used for newspapers, magazines and other high-volume jobs.

Web Offset:

A printing lithographic process that prints on paper from a continuous roll and delivers onto another roll or as folded signatures.

Wet Printing:

Printing one process color over the other while it's still wet.

Web Tension:

The amount of pull applied in the direction of travel of a web by the action of pulling the web through the press.

Wetting:

Surrounding minute particles of pigment with resin solutions during ink making.

Wetting Agent:

A substance that reduces the surface tension of a liquid, thereby causing it to spread more readily on a solid surface.

Wet-on-Wet: Finishing

Applying a new coat over an earlier applied coat that has been allowed to flash-off but not to cure.

Wet Trap:

To print ink or varnish over wet ink, as compared to dry trap.

Whiskers:

Hairy edges of shadow areas due to static electricity.

White Light:

Theoretically, light that emits all wavelengths of the visible spectrum at uniform intensity. In reality, most light sources cannot achieve such perfection.

Whitepoint:

On a monitor, the combination of all three Red, Green, and Blue phosphors at full intensity - as measured by its color temperature in ŸK. Necessary as a reference point in calibration and characterization.

Wicking

A too rapid absorption of ink into a susbtrate causing excessive strike-through, smudged detail, and fuzzy lines.

Wide-Web Flexographic Press:

A flexographic press capable of printing substrates greater than 18 inches in width.

Winder Wrinkles:

A paper defect caused by a hard spot on the winder reel.

Winding:

The process of transferring paper from the master machine roll to rolls suitable for use on a press. Also called rewinding.

Window:

A clear, usually rectangular or square, open panel in litho negative for stripping halftone negatives into position with tape.

Wiping Angle:

Also called the set angle, the angle the doctor blade is set from the center line of the cylinder, before pressure is applied.

Wire Edge:

Material coming off the blade edge as the blade seats itself to the printing cylinder for proper wipe. See also - Burr.

Wire Side:

The bottom side of paper as it is formed in a Fourdrinier paper machine, i.e., the side that touches the wire.

With the Grain:

Parallel to the grain direction of the paper being used, as compared to against the grain. See also Grain Direction.

Woodfree Paper:

Made with chemical pulp only. Paper usually classified as calendered or supercalendered.

Wove:

Paper manufactured without visible wire marks, usually a fine textured paper.

Wrap Around:

Electrostatic effect where charged coating particles curve around the part and are deposited onto the rear side of the part.

Wratten Gelatin Filter:

A thin, colored plastic that is optically pure and is used to separate colors in photographic systems. The Wratten filter number specifies the filter color.

Wrong Reading

An image that is backwards when compared to the original. Also called flopped and reverse reading.

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X:

1) One of the three CIE tristimulus values; the red primary. 2) Spectral color-matching functions of the CIE standard observer used for calculating the X tristimulus value. 3) One of the CIE chromaticity coordinates calculated as the fraction of the sum of the three tristimulus values attributable to the X value.

X,Y Diagram:

Chromaticity diagram in which the (x,y) chromaticity coordinates of the CIE XYZ system are used.

Xerography:

A reproductive process that uses a corona-charged surface that conducts light, toner and static forces to burn an image onto paper.

Y:

1) One of the three CIE tristimulus values, equal to the luminous reflectance or transmittance; the green primary. 2) Spectral colormatching function of the CIE standard observer used for calculating Y tristimulus value. 3) One of the CIE chromaticity coordinates calculated as the fraction of the sum of the three tristimulus values, attributable to the Y value.

Yield Point:

The stress at which a material begins to plastically deform. Prior to the yield point, the material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed, some fraction of the deformation will be permanent and non-reversible.

Yellow:

One of the process ink colors for printing. Pure yellow is the “blueless” color; it absorbs all wavelengths of blue from light and reflects all red and green wavelengths.

Young's Modulus of Elasticity:

Describes tensile elasticity, or the tendency of an object to deform along an axis when opposing forces are applied along that axis; it is defined as the ratio of tensile stress to tensile strain. Because all other elastic moduli can be derived from Young's modulus, it is often referred to simply as the elastic modulus. Young's modulus is a mathematical consequence of the Pauli exclusion principle.

Z:

1) One of the three CIE tristimulus values; the blue primary. 2) Spectral color-matching function of the CIE standard observer used for calculating the Z tristimulus value. 3) One of the CIE chromaticity coordinates calculated as the fraction of the sum of the three tristimulus values attributable to the Z primary.

Zahn Cup:

The brand name of an efflux cup used for the measurement of the viscosity of an ink by measuring the time taken for a given quantity of ink to flow through a small hole in the bottom of the cup at a given temperature. Different drain hole sizes and cup sizes are available.