Updated 18 Febr. 2010
Wallpaper baseboard – Two-layer board, grammage 120-200 g/m2, used to make wallpaper.
Washer room – Pulp mill department where pulp is washed free of cooking chemicals.
Wash-up – To clean ink and fountain solutions from rollers, fountains, screens, and other press components.
Waste – Unusable paper or paper damage during normal make-ready, printing or binding operations, as compared to spoilage.
Waste (Hazardous) – A waste with properties that make it dangerous or potentially harmful to human health or the environment. The universe of hazardous wastes is large and diverse. Hazardous wastes can be liquids, solids, contained gases, or sludges. They can be the by-products of manufacturing processes or simply discarded commercial products, like cleaning fluids or pesticides. Non-hazardous waste includes all solid waste that does not meet the definition of hazardous waste. (http://www.epa.gov/osw/laws-reg.htm).
Waste Management – The collection, transport, processing, recycling or disposal of waste materials. The term usually relates to materials produced by human activity, and is generally undertaken to reduce their effect on health, aesthetics or amenity. Waste management is also carried out to reduce the materials” effect on the environment and to recover resources from them. Waste management can involve solid, liquid or gaseous substances, with different methods and fields of expertise for each. (http://en.wikipedia.org/wiki/Waste_management)
Waste-to-Energy – The practice of incinerating waste products to generate steam, heat, or electricity.
Waste paper – All paper after it has been used; cf. recovered paper
Water Based (inks/coatings) – See “Aqueous” (inks/coatings).
Water Break – The appearance of a discontinuous film of water on a surface signifying non-uniform wetting and usually associated with surface contamination.
Water vapour transmission rate – usually measured at 100% relative humidity, expressed in grams/100 square inches/24 hours, (or grams/square meter/24 Hrs.)
Watermark – The impression of a design, pattern or symbol in a sheet while it is being formed on the paper machine wire. It appears in the finished sheet as either a lighter or darker area than the rest of the paper. A shaded watermark (aka intaglio watermark) is produced by a dandy roll located at or near the suction box on the paper machine. The desired design is pressed into the wire covering the surface of the dandy roll similar to an intaglio engraving. As the wet pulp moves along the web, the dandy roll presses down and creates an accumulation of fibres, thus the watermark is seen as being darker than the rest of the sheet. A wire mark is accomplished by impressing a dandy roll with a raised surface pattern into the moving paper web in a similar manner to the shaded mark. This creates an area with less fibre, making it lighter and more translucent.
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.
Waxing – The application of paraffin to printed board or carton blanks as a preservative coating resulting in a high-gloss or impregnated finish.
Wear-In (Seat) – Break in a rotating doctor blade by applying pressure against cylinder without printing to wear in the blade.
Web – (1) The continuous sheet of fibres and water that is formed into a sheet of paper as the water is removed. (2) Continuous sheet of paper on a paper machine in roll form. (3) A roll of any substrate that passes continuously through a printing press or converting or finishing equipment. (4) A continuous sheet of boxboard or other flexible material coming from the machine which produces it. It may be slit and rewound into rolls or cut into sheets. Also refers to belt or blanket on which boxboard is conveyed through papermaking machines. Roll stock is used on some printing and converting equipment.
Web Break – Split of the paper as it travels through a web press, causing operators to rethread the press.
Web flexo – A roll-fed, relief-printing process while offset is a sheet-fed, surface printing process.
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 glazing – Imparting a gloss to the paper web; calendering.
Web Growth – see Web Gain
Web Guide – Device that keeps the web travelling straight or true through the press.
Web Offset – A printing lithographic process that prints on paper from a continuous roll and delivers onto another roll or as folded signatures.
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 Tension – The amount of pull applied in the direction of travel of a web by the action of pulling the web through the press.
Weld Spout – See Spout Pouch
Wet end – First part of the paper machine up to the drying section
Wet lamination – This type of lamination offers a cost effective alternative to a dry lamination and is used when the product does not require the strongest bond strength. The bonding liquid used by our manufacturers is PE resin.
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 Printing – Printing one process colour over the other while it’s still wet.
Wet Strength – The firmness of a paper or board after it has been saturated with water for a specified time, as determined by its wet tear resistance, wet tensile strength or wet bursting strength. In short: Mechanical strength of paper when wet.
Wet Strength Board – (1) A specially treated board, usually kraft, that is resistant to moisture. Wet strength board is often used for beverage carriers, frozen foods, or in applications where the board will be exposed to excessive amounts of moisture, condensation, etc. (see Carrier Board) (2) Once wet, ordinary papers lose most of their original dry-strength properties. Wet strength board is chemically treated to resist tearing, disintegration and rupture when saturated with water. MeadWestvaco’s Carrier Kote maintains as much as 90% of its dry strength following immersion in water.
Wet tensile strength – Ability of wet paper to resist tension in the plane of its surface.
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 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.
White lined chipboard – A multi-ply construction made predominantly from selected waste paper with a bleached chemical pulp liner. European designation: GD or GT (coated recycled board).
Whiteness – A colour measurement which corresponds to the whiteness perception of the human eye.
Whiteness and brightness – These are aesthetic qualities, defining the look of the paper and its likely perception in the hands of the end user, as well as impacting on print quality and visual contrast.
Whitepoint – On a monitor, the combination of all three Red, Green, and Blue phosphors at full intensity – as measured by its colour temperature in ŸK. Necessary as a reference point in calibration and characterization.
Wicking – A too rapid absorption of ink into a substrate causing excessive strike-through, smudged detail, and fuzzy lines.
Wide mouth – Containers with a large finish opening or those that have a large finish size in proportion to their capacity.
Wide Mouth PlasTop hot fill closure – Trademark of Rexam – Lined tamper-evident closure ideal for hot fill products.
Wide-Web Flexographic Press – A flexographic press capable of printing substrates greater than 18 inches in width.
Widget technology –
Winder – Machine for cutting the paper web longitudinally into narrower webs, which are then wound to reels; also slitter- winder.
Winder Wrinkles – A paper defect caused by a hard spot on the winder reel.
Winding – 1) Operation whereby a web of paper or board is wound into one or more reels. 2) The process of transferring paper from the master machine roll to rolls suitable for use on a press. Also called rewinding.
Window – 1) A die- cut opening in a carton blank which provides visibility of contents, usually covered with a transparent film. Sometimes referred to as an aperture. 2) A clear, usually rectangular or square, open panel in litho negative for stripping halftone negatives into position with tape.
Window stripe – A see-through vertical stripe on a moulded bottle; used primarily to monitor the level of the contents.
Wiping Angle – Also called the set angle, the angle the doctor blade is set from the centre line of the cylinder, before pressure is applied.
Wire – Flat belt of metal or plastic mesh on which the paper or board web is dewatered.
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.
Wood bank – An arrangement whereby companies exchange wood raw material to minimize transport costs.
Woodcontaining – Paper containing a certain proportion of mechanical pulp.
Wood fibre – Wood cells; the main raw material for papermaking.
Woodfree Paper – Made with chemical pulp only. Paper usually classified as calendered or super-calandered.
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.
Wraparound corrugated case –
Wratten Gelatine Filter – A thin, coloured plastic that is optically pure and is used to separate colours in photographic systems. The Wratten filter number specifies the filter colour.
Wrong Reading – An image that is backwards when compared to the original. Also called flopped and reverse reading.
WVTR – see: Water vapour transmission rate.