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Glossary

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DAMPENERS
The rollers (mechanical devices) that carry the fountain solution from the press fountain to the lithographic plate.

DAMPENING SOLUTION
Also called dampening etch (particularly in reference to fountain solution concentrate). See fountain solution.

DANCER ROLL
Usually, a weighted roll that rides on a web of paper between two fixed points (for example, between an unwinding roll of paper and an impression or coating nip) to take up slack and maintain a uniform web tension.

DANDY ROLL
A hollow wire-covered roll that rides on the paper machine wire and compacts the wet, newly formed web to improve its formation and, if required, to impart a watermark or laid finish to paper. On the paper machine, impresses the still wet web of paper to smooth the formation, reduce foam bubbles, and to impress a pattern if desired; with raised areas on the wire covered dandy roll, can give a watermark or laid pattern; with recessed areas, can also give a watermark like pattern called a "shadow mark"; the raised or recessed patterns on the dandy roll result in a difference in transparency and usually a desired effect, if light is viewed through the sheet.

DEBARKING DRUM
Large rotating cylinder in which pulpwood logs are tumbled against one another to remove the bark.

DECIDUOUS
Leaf bearing trees that shed them with the seasons, like oak and maple; also known as "hardwood." Pulps made from this type of tree give cellulose paper making fibers that are short, thus "short fiber."

DECKLE
A term sometimes used to refer to the wet end width of a paper machine. In paper making, the width of the wet sheet as it comes off the wire.

DECKLE EDGE
The feathery edge which is the result of the natural run-off of wet pulp when making handmade and mould made paper, or the result of sheets being torn when wet. The edge is simulated in machine made papers by cutting them with a stream of water when still wet. The untrimmed, feathered edge of the dried paper from the paper machine. See deckle and feather.

DECKLE STAIN
Paper that has a coloring or tint along the deckle edge.

DEINKING
The removal of lignin from wood. The mechanical or chemical removal of printing inks and other foreign materials from paper, so that the cellulose fibers can be reused or recycled.

DELAMINATE
See plybond.

DELIGNIFICATION
A process in which most of the ink, filler, and other extraneous material is removed from printed and/or unprinted waste paper. The result is pulp which can be used, along with various percentages of virgin pulp in the manufacture of new papers for printing, writing, office, tissue and toweling products.

DELIVERY
The printing press mechanism that handles the paper, after it is printed. Printing presses "deliver" the printed product as flat sheets, folded sheets (signatures), finished products or rewound rolls.

DENSITY
The weight of a sheet of paper as compared to its bulk. For example, a paper that weighs more than another paper but is thinner has a higher density. Compacting the fibers creates a dense paper.

DENSITOMETER
Instrument used to measure the optical density of an image or color; optical density is the intensity of the color or printed image, usually (but not always) referenced to black and/or white.

DESENSITIZE
1) In lithographic printing plates, making the non-image area of the metal plate non-receptive to ink. The main desensitizing material is usually a gum. 2) In carbonless paper, the over-printing of the CF (receiving) surface so as to eliminate its ability to develop an image from the CB surface.

DIE
Engraved copper reverse image used to imprint foil or ink on the cover of a book. This is sometimes referred to as the brass.

DIE CUT
The method of cutting paper into irregular shapes by metallic die to specified dimensions.

DIGESTER
Pressure vessel for chemical treatment of chips and other fibrous materials like straw bagasse rags, etc., under elevated temperature and pressure to separate fibers. The large pressure vessel in which wood is pulped (cooked), to extract the cellulose fibers; can be continuous or batch process digesters.

DIGITAL ON-DEMAND
See Print On-Demand.

DILATANT
The property of some inks and coatings to become less fluid (higher viscosity) when worked (stirred), as a result of separation of the vehicle phase from the suspended materials; this dilatancy phenomenon is not always reversible, once the separation has occurred. Also see thixotropic.

DILITHO
See direct printing.

DIMENSIONAL STABILITY
Paper's ability to maintain size and resistance to dimensional change when exposed to various ambient conditions. Ability to maintain size under conditions of varying moisture or humidity; the property of a sheet of paper which relates to its constancy of dimensions under conditions of different relative humidities.

DIOXIN
A carcinogenic contaminant generated when chlorine is used in bleaching wood pulp.

DIOXIN CONTENT
The percentage of dioxin, which is an undesirable chlorinated contaminant generated when chlorine is used in bleaching wood pulp.

DIRECT PRINTING
Any printing where the ink is transferred directly from the plate to the paper; most lithographic printing is "offset," i.e., a blanket is utilized to transfer the ink from the plate to the paper. Dilitho is the abbreviated term for direct lithography.

DISHED ROLL
See telescoped roll.

DISK REFINING
See refining.

DOCTOR
Usually a blade used on many types of equipment for coating (see blade coating), for metering (removing excess ink from a gravure cylinder or plate), or for keeping the surface of a roll clean.

DOG EAR
See turnover.

DOT GAIN
The gain in size of the printed dot, as a result of the ink, paper, printing pressure, prepress operation, or any combination of these. Since the dots printed are larger than planned, this can be a defect evidenced by darker tones and/or different hues.

DOT
The individual printing element or spot in halftone printing.

DOUBLE COATED
A sheet that has been coated twice on the same side. Sometimes incorrectly confused with a sheet coated on both sides.

DOUBLING
In printing, the appearance of a latent, second or ghost like image of the original on the printed piece, or the appearance of a "slur" or blurring of the image. Doubling can be the result of "creep," or even a mechanical feeding problem on the press, where the image has moved its position on the blanket (resulting in a misregister from unit to unit). If the cause of the doubling is due to "creep," the latent image will generally disappear as the latent ink image is removed from the repositioned blanket. Variability (come and go) of the latent doubling image is usually due to a mechanical press or feeding problem. Paper distortions can also cause doubling.

DPI - (dots per inch)
In printing the number of dots that fit horizontally and vertically into a one inch measure. Generally, the more dots per inch, the more detail is captured, and the sharper the image.

DRAG MARK
See coating streak.

DRAWDOWN
The application (by a blade or a bar) of a thin film of coating or ink to a piece of paper; it is used as a test method for coating or ink characteristics (such as shade, color strength, coating strength, or other simulation testing).

DRAW
1) In guillotine trimming of paper, the displacement of the cut sheet in a clamped stack by the thickness of the knife; can result in inaccurately cut paper. 2) The tension on a paper web between sections of a piece of equipment, such as a paper machine, coater, or printing press.

DRY END
The part of a paper machine where sheet moisture is removed by evaporation. Consists of several dryer sections or air dryers, depending on the machine's type and size.

DRYERS
In a paper-facility, the portion of the paper machine where the wet web is dried on large, heated rollers. Can be infrared or hot-air assisted. 1) The pieces of equipment used to dry the paper during manufacture or coating, or during printing (large, steam heated rotary cylinders, hot air dryers, or direct radiant heat impingement). 2) Various materials added to ink to promote or speed (catalyze) ink drying by oxidation/ polymerization; also spelled driers.

DRILLING
Piercing of stacks of paper in a precise manner; loose leaf notebook paper is an example of drilled paper, using a hollow point drill.

DRY BACK
The term applied when the density and/or gloss of the wet, freshly printed ink film decreases after drying, to a greater extent than was anticipated. It is generally related to an overly absorbent paper surface, or a poor ink-paper choice and match.

DRY END
That part of the paper machine where the paper is dried; the last sections of the machine.

DRY OFFSET
See letterpress printing; refers to the use of a letterpress plate or cylinder on an offset press, i.e., transfers the ink from the plate to the paper on an intermediate blanket cylinder. Also called letterset.

DRY TRAPPING
See trapping.

DRYING OF INKS
Printing inks dry in a number of different ways, and often in a combination of these: absorption, oxidation, polymerization, evaporation, precipitation, solidification (such as cooling of a hot, melted material) and radiation curing. All of these are mechanisms for turning a fluid, mobile ink into a relatively immobile image.

DRYING OILS
Oils which posses the property of hardening to a tough film by oxidation and polymerization (like linseed oil).

DULL COATED
Same as dull finish. Paper is said to be dull coated when it registers a gloss test reading of less than 55 percent. Characteristically, dull coated or finished paper has a smooth surface and is low in gloss. Generally, it is categorized as falling between an uncoated sheet and a regular coated (semi-dull) paper.

DULL FINISH
A finish with a low gloss. With respect to coated box paper, a finish with a glare test less than 55 percent. See gloss; any finish lacking gloss and/or luster; generally refers to an intermediate gloss of coated papers or to printed ink films.

DUMMY
A preliminary layout or presentation to show the style, form, size or shape of a printing job.

DUNNAGE BAG
A bag manufactured of heavy polyethylene coated kraft paper (or entirely of rubber), used to hold rail car contents in place during transit. The bag is inflated with air as the rail car is loaded then deflated during unloading.

DUOTONE
A halftone illustration printed in two colors from a single color original to increase contrast or image.

DUPLEX
1) Texture that may be produced by a multi-ply machine, using two different stocks or by lining a board with two kinds of stock: it may also be obtained by pasting (laminating) together two papers or boards of different texture. 2) General term that refers to multi-ply paper and paperboard and bags made of two sheets of paper.

DUPLEX COATED BRISTOL
Used for advertising, postcards and folders, this paper is characterized by a solid center coated with a bright or deep color on one side and a harmonizing shade or white on the reverse. The center base is generally manufactured from softwood and hardwood chemical pulp and is approximately 10 points in thickness.

DUPLICATING PAPERS
A general term applied to a vast group of papers used in any type of copying or duplicating process. Each paper is uniquely designed for its specific function. Sometimes called copier paper.

DUPLICATOR
Earlier the term referred to "spirit duplicators," but has now come to mean (generally small) sheet-fed lithographic presses that more often than not are for relatively short runs (up to 10,000).

DURABILITY
The degree of which a paper retains its original qualities under normal continued use. This is not to be confused with permanence. See permanence.

DUST
Loose particles of fibers, filler, or coating materials appearing on the edges of a skid, lift, or roll of paper; this dust can interfere with the quality of the printing, particularly if on the sheet or web surface.


 
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