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Glossary

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GAP
See cylinder gap.

GAMPI
A bast fiber from the gampi tree used in Japanese papermaking to yield a smooth, strong sheet.

GATF
Abbreviation for "Graphic Arts Technical Foundation".

GATHERING
Collecting printed signatures in proper book order. The assembling of sheets of paper or folded signatures in proper sequence. See collating.

GCR
Abbreviation for "gray component replacement"; also see "ucr". Three color process can produce gray tonal values, but slight hue shifts can occur (such as can result from dot gain and or non-equal trapping). Adding black (four-color process) for better black prints is common. Gray component replacement is the additional work done in color separation to reduce the amounts of yellow, magenta, and cyan and to replace them with black ink. This can make better/more consistent grays in the printed image (and usually at lower single ink cost).

GEAR STREAKS
In printing, parallel streaks appearing across the printed sheet, at an interval harmonic with the gear teeth of a press cylinder.

GENERAL PURPOSE BOND
Forms paper, which is translucent to ultraviolet light but opaque enough to provide legible printed forms.

GHOSTING
Ghost images are unwanted images (often faint) that appear in the printed piece. Mechanical ghosting is usually traceable to conditions on the printing press and/or layout of the form. Chemical ghosting (gloss ghosting, dull ghosting, trapping ghosting, fuming, etc.) is usually delayed from the printing operation, and evidenced later. Chemical ghosting is usually the result of the vapor transfer of an image, usually weak, from the freshly printed sheet to the back of another sheet (across, from surface to surface).

GLASSINE
A smooth, dense, semi-transparent paper that has been supercalendered to produce a glazed and polished surface on both sides. Used as envelope windows and in protective packaging for foods, candy, tobacco products, chemicals and metallic items.

GLAZING/BLANKET GLAZING
A glazed appearance or condition on the offset blanket that is the result of excess gum being deposited in the nonimage areas; is most likely caused by either excess evaporation of the fountain vehicle (alcohol and water), leaving behind the gum, or as a result of the gum being insoluble or kicked out of the fountain solution.

GLOSS
The attribute of paper which causes it to be shiny and lustrous. The "shininess" ("glare") reflected from a surface; in paper measurement, it is the specular reflection of light, incident and reflected at a 15 degree angle from a surface, as compared to a polished plate of black glass; papers can range in finish from matte to satin or dull to glossy.

GRADE
A class or level of quality of a paper which is ranked or distinguished from other paper on the basis of its end-use, appearance, quality, raw material or a combination of the above.

GRAIN
Directional alignment of fibers in a sheet of paper.

GRAINY
Rough paper surface or finish, generally due to shrinkage, particularly at the edges of the web coming off the paper machine.

GRAIN DIRECTION
The direction in which paper fibers are predominantly aligned. Grain is parallel to the direction of the flow on the paper machine. *NOTE - Grain direction should always run parallel to the spine of a book to prevent buckling and to enhance its pageability.

The direction of orientation/ alignment of cellulose fibers in a sheet or web of paper, resulting from the flow of fibers in a water suspension, during the paper making process; the direction of paper parallel to its forward movement on the paper machine; also called "machine direction", with the orientation perpendicular or at right angles being called "cross direction".

GRAIN LONG
A sheet with grain parallel to its longest dimension.
Example: 25" X 38" (Note the underscoring to denote the grain dimension). A sheet of paper where the grain direction is in the long dimension, an 8 1/2" x 11, sheet of paper is grain long, if the grain direction is parallel to the 11" dimension.

GRAIN SHORT
A sheet with grain parallel to its shortest dimension.
Example: 38" X 25" (Note the underscoring to denote the grain dimension). A sheet of paper where the grain direction is in the short dimension; an 11 " x 8 1 / 2" sheet of paper is grain short, if the grain direction is parallel to the 8 1/2" dimension.

GRAMMAGE
This term denotes the weight of paper or board; the measurement used is the weight of a single sheet of one square meter, expressed as gram per square meter (g/m). See basis weight.

GRAMS PER SQUARE METER
The gram weight of a hypothetical square meter of a particular type of paper, a good comparative measure because it does not vary with sheet size.

GRAPHIC ARTS
In common usage, this includes all components and segments of the printing industry, as well as other industries or media which utilize graphic images.

GRATER ROLLS
Rollers on a printing press that guide and support the web; used most often on a web that has just had wet ink applied, to prevent tracking; the rollers generally have a rough or textured surface to minimize the possibility of tracking and/or smearing of the freshly printed ink film, and to aid in gripping and guiding the web of paper; also, see "idler rollers".

GRAVURE PRINTING
An intaglio or recessed printing process. The recessed areas are like wells that form the image as paper passes through.
A form of recessed printing, as is engraving. The printing method where the very fluid ink is applied to the plate or plate cylinder, and is actually carried in small microscopic cells, recessed into the plate; used for long run printing applications, due to plate or cylinder costs, but long plate life; since run on rotary presses, called rotogravure. Engraved printing is based on the same principle, using larger recessed areas (as opposed to microscopic cells) and more viscous inks.

GRIPPER MARGIN/EDGE
The lead edge going through a sheet fed press. The edge that contacts the press grippers. Sheet-fed presses require a plain unprinted (and unprintable) margin on tile leading edge of the sheet where the grippers that pull the paper thru the press holds onto it; usually 1/2 inch or less.

GROUNDWOOD
Papers made from mechanical pulp produced by grinding bark free logs against revolving stones or discs. Newsprint is an example of groundwood. Wood derived pulp, obtained by mechanical means, and containing all the tree's lignin type materials; carefully cleaned and debarked logs were originally pressed against the face of a rapidly revolving grindstone. The abrasive action tore the fibers from their setting in the wood. Groundwood is one type of mechanical pulp, but the term is often used synonymously with mechanical pulp.

GROUNDWOOD FREE
Containing no mechanical wood pulps.

GROUNDWOOD PAPER
Paper that is made from a furnish containing a large percentage of groundwood pulp. Term applied to papers containing a substantial proportion of ground- wood or mechanical pulp.

GROUNDWOOD PULP
Slurry produced by mechanically abrading fibers from barked logs through forced contact with the surface of a revolving grindstone. This is used to make newsprint and other publication papers.

GUIDE EDGE
The edge of a sheet at right angles to the gripper edge, that travels along a guide to position the sheet on the table and thru the sheet-fed printing press. The guide edge is the means of control of edge to edge register of the images.

GUIDE ROLL
A roll or roller used on a running web of paper, and can be "cocked" to compensate for side to side draw difference variations.

GUILDING
The application of a gold or silver metallic material to one or all three sides of a trimmed book.

GUILLOTINE
A machine equipped with a long heavy removable knife for trimming paper with a downward slicing action. In the United States, it is called a trimmer or ream cutter.

GUM
A water soluble resinous material (generally naturally harvested gum arabic, but can be a substitute synthetic materials derived from cellulose), used to treat the lithographic printing plate and make the non-image areas of the plate more wettable and receptive to the dampening solution. Also, the dampening solution usually contains a gum to replenish that worn away from the plate during printing.

GUMMED PAPER
All papers that include an adhesive on one side of the sheet. Could be a remoistening, thermo-adhesive or pressure sensitive.

GURLEY DENSOMETER
A test for porosity that measures a standard volume of air permeability through paper under specified pressure. The test is read in seconds.

GURLEY SPEC (23 GURLEY)
Gurley Porosity Test measures the air resistance of paper under specified pressure. The air resistance is measured in seconds. This specification for return mail card is set by the U.S. Postal Service and involves basis weight and caliper (BW = 75lb. and Caliper = 7 pt. Minimum). Insertion equipment manufacturers have determined that a Gurley Porosity reading of 23 seconds is needed to successfully feed return mail cards into magazines.

GUTTER
The inside margin in a bound piece, between the printed area and the binding; also gutter margin.

GYPSUM
A filler for paper with good retention for color and brightness. Unlike other fillers, it does not reduce the efficiency of internal sizing.


 
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