PULP AND PAPER DICTIONARY
This page contains definitions of the terms, words and phrase commonly used in pulp and papermaking, printing, converting and paper trading.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
LABEL A separate slip or sheet of paper affixed to a surface for identification or description. For fibreboard boxes, includes: Full Label, Mailing or shipping Label, Spot Label and UPC (Universal Product Code) Label.
LABEL PAPER Mostly one-side coated papers which must be printable in 4-colour offset and gravure printing. These papers are usually suitable for varnishing, bronzing and punching and sometimes also feature wet strength and alkali resistance (See "Wet strength and alkali resistant paper") in order to en-sure the removal of the labels e.g. in the bottle rinsing machines of breweries
LAID A finished produced with a dandy roll having closely spaced wires.
LAID LINES A continuous watermark consisting of very close parallel lines, generally associated with spaced lines (chain lines) at right angles to these.
LAMINATED PAPER A paper built up to a desired thickness or a given desired surface by joining together two or more webs or sheets. The papers thus joined may be alike or different; a totally different material, such as foil, may be laminated with paper.
LAMINATED LINERBOARD Two or more plies of linerboard adhered to one another for increased structural stability.
LAMINATING - A process which combines two or more plies of material with a strong bond, usually durable even when wet. For a much weaker bond, one of the ply bonding processes is used. Most premium consumer paper towels sold in the US are made with a process that combines laminating with embossing in a single unit. This is often called double-nip embossing laminating, and has several variations: nested , pin-to-pin , or random registration . Each variation requires two separate embossing operations (double-nip) that run in parallel, an adhesive applicator that places small amounts of glue on the tips of the raised elements of the paper while it is still in contact with one of the embossing rollers, a laminating area between the two embossing rollers (that may be either a closed nip or an open nip) where the plies are brought back together again, and a marrying nip (or shoe) where pressure is applied to make the adhesive bond stronger.
LAMINATOR A machine that adheres multiple plies of paper or fibreboard. May be used to adhere full labels to a facing, or, for enhanced structural properties, multiple facings, corrugating mediums or sheets of combined board.
LAPPING MACHINE A wet machine on which folded wet pulp sheets are produced from screened pulp for storage and/or shipment.
LASER PRINTING Xerographic printing where a modulated laser ray is projected on to a photoconductive cylinder or belt by a rotating mirror. The laser serves to product the electrostatic latent image, which is developed with toners.
LATENCY The curl and spiral of individual pulp fibre created during refining specially in thermomechanical pulping process
LATENCY CHEST A storage chest after the second stage refining in thermo-mechanical pulping process in which pulp is agitated and stored at a specified temperature for a predetermined time to remove latency.
LAYBOY A device at the end of cutter for jogging sheets in to a square pile.
LEACHATE Water that has as a component of dissolved matter accumulated as a result of passing through material. e.g. rain water passing through waste dump.
LEAD DRYER OR BABY DRYER A small diameter dryer just after the press section.
LEAF FIBRES Papermaking fibres coming from the leaves of the plant such as hemp, manila, flax, sisal etc.
LEDGER PAPER A strong paper usually made for accounting and records. It is similar to Bond paper in its erasure and pen writing characteristics.
LETTER FOLD This common fold, used for mailings and brochures, is much like a letter folded by hand for inserting in an envelope. The letter fold produces a self-contained unit, easily handled by automated envelope inserters. For picture of this type and other fold please visit http://www.bradenprint.com/pdf/Folds-IS.pdf
LETTER PRESS A process of printing in which raised images are coated with ink and pressed directly onto a paper or paperboard surface
LICK COATING A light form of mineral coating, achieved by supplying the surface sizing press of the paper making machine with coating material instead of normal surface sizing solution.
LIGHTFASTNESS The speed at which a pigment or coloured paper fades in sunlight. Or how permanent a colour is or how unaffected by light it is.
LIGHT WEIGHT COATING (LWC) Coating applied at 7-10 g/m2 on one or both sides of the paper.
LIGHT WEIGHT PAPER Papers having a grammage (basis weight) normally less than 40 g/m2.
LIGNIN A complex constituent of the wood that cement the cellulose fibres together. Lignin is brown in colour. Lignin is largely responsible for the strength and rigidity of plants, but its presence in paper is believed to contribute to chemical degradation. To a large extent, lignin can be removed during manufacturing.
LIGNOCELLULOSE Refers to plant materials made up primarily of lignin, cellulose, and hemicellulose.
LIKE-SIDED Paper that has the same appearance and characteristics on both sides.
LIME SLUDGE OR SLUDGE Sludge of calcium carbonate (CaCO3) formed during preparation of white liquor in the chemical recovery process.
LINEN FINISH A finished paper that has an overall embossed pattern on the surface resembling the look and feel of linen cloth, and one manufactured with engraved embossing rolls.
LINER A creased fibreboard sheet inserted as a sleeve in a container and covering all side walls. Used to provide extra stacking strength or cushioning. Also used as a short hand for "linerboard" or facing."
LINERBOARD The inner and outer layers of paper that form the wall of a corrugated board.
LINES PER INCH (LPI) The number of lines in an inch, as found on the screens that create halftones and four-color process images (for example, "printed 175-line screen"). The more lines per inch, the more detailed the printed image will be. With the demand for computer-generated imagery, the term "dots per inch" (which refers to the resolution of the output), is replacing the term "lines per inch."
LINT Loosely bonded fibres at the paper surface that attached to the plate or blanket of the printing machine.
LITHO A generic term for any printing process in which the image area and the non-image area exist on the same plate and are separated by a chemical repulsion. Usually oil based offset printing.
LOADING Addition of fillers
LOFT DRYER A heated room in which wet sheet of paper/paperboard are hang on poles. This old method of drying is known as loft drying or pole drying.
LOG A piece of pulpwood length cut from trees to convenient size for storage, transportation and handing.
LOGGING The operation of harvesting trees from woodlands, processing in to barked/unbarked logs or chips.
LONG LOG A whole length pulpwood before cutting to shorter log.
LOOK THROUGH The appearance of the paper when held up to transmitted light. It discloses whether the formation is even and uniform or lumpy and ‘wild’. For book publishing papers, a regular, even look through is desirable, indicating a well made, uniform sheet.
LOOSE WINDING A paper roll winding defect caused by insufficient sheet tension during winding.
LOTIONIZING - A process which improves the perception of the softness of a paper product by the application of an invisible substance onto its surface. The substance is often an oil, a wax, or a silicone. This is most often applied to facial tissue .
LUMEN The center void portion of a cellulose fibre.
LUMP An incomplete separation of fibre bundling or coming together of fibres and other papermaking materials, causing raised, hard and localized spots in the sheet.