In our business, it is a necessity to know basic paper and printing terms. Use the glossary for a quick reference or browse it to refresh your knowledge.
Select from the general listing below:
gap
See cylinder gap.
GATF
Abbreviation for "Graphic Arts Technical Foundation".
gathering
The assembling of sheets of paper or folded signatures in proper sequence. See also <i>collating</i>.
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.
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).
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 "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.
grain direction
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 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 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.
grainy
Rough paper surface or finish, generally due to shrinkage, particularly at the edges of the web coming off the paper machine.
grammage
See basis weight.
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. See also <i>idler rollers</i>.
gravure printing
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
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
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 papers
Term applied to papers containing a substantial proportion of ground-wood or mechanical pulp.
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.
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.
gutter
The inside margin in a bound piece, between the printed area and the binding; also gutter margin.
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