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The Heidelberg website glossary explains, in alphabetical order, a multitude of terms relevant to printing, as well as some terms used in Heidelberg's product catalogue.

Simply click on the letter of your choice to access the information you need.

Gamma value (gradation): The gradient or angle of slope of the straight section of a blackening curve, calculated according to the tangent formed by the angle of the curve in relation to the straight line. The gamma curve describes the relationship between the tone values in an image file at input and the tonal response of the output device (monitor). The greater the gamma value, the steeper the curve. In color management the gamma value indicates how the exposure range is produced in density values (the density range).
Gamut: The range of colors that can be produced by a color system; tonal value and color range that can be produced or reproduced by a system or process depending on the color space and colorants used. See also "color space".
GATF (Graphic Arts Technical Foundation): A technical association based in Sewickley, Pennsylvania and active in the printing industry. In 1999 the organization merged with the Printing Industries of America (PIA) and now has some 14,000 members in 60 different countries.
Gatherer-stitcher (gang-stitcher): A device for stitching printed products and creating magazines, brochures, etc. from printed and folded sheets. The print sheets and jacket are collated in the correct order, aligned and then stitched using wire staples. Finally, the volume is cut on three sides. This separates the sheet folds that do not lie on the spine edge, and thus the booklet takes on its familiar shape.
Gaussian blur: A tool used to give images, graphics and photos a “blurred” or “softened” look. It is often used in the design of background graphics, which seem to be “cushioned” into the background.
GCA (Graphic Communications Association): Former name of the International Digital Enterprise Alliance (IDE Alliance).
GCR (gray component replacement, achromatic color removal): The process by which gray tones are proportionally removed from the exact amounts of cyan, magenta and yellow that make up gray and replaced by the corresponding quantity of black ink. This is primarily performed for neutral color tones and in the gray components of unsaturated colors. The process allows for ink reduction and reduces the effects of color shifts.
Ghosting: An error that can occur in such indirect printing processes as offset when screen dots have double or multiple contours. It can be observed in single-color printing, but more often in multi-color printing. Faulty printing of this type increases the screen tonal value and leads to dot gain. This slight shift in the position of the printing elements is caused by register fluctuations during printing, which may themselves be caused by the paper or the press.
GIF (Graphics Interchange Format): A storage format for images and graphics involving lossy compression and that allows 256 colors to be displayed from any pallet. The data format was introduced by the Compuserve online service in 1987, which makes it one of the oldest of its kind. GIF remains one of the most widely-used formats for online publication, and also allows for image animations.
Gigabyte: A unit of measurement abbreviated as “G” or “GB” that approximately corresponds to one billion bytes. It is used to quantify memory or disk capacity.
Glassine: A highly greaseproof, but not wet-resistant paper grade made of finely ground pulp. It is highly supercalendered and therefore relatively transparent.
Glyph: A symbol carved in stone; in typography a letter with more than one variant in an alphabet, such as “s” in German as well as Greek.
Goffering: A process for shaping the surface of paper into a pattern, usually with fine grooves.
Gradation: See "gamma value".
Grain direction: The direction in which the pulp fibers of a sheet of paper are aligned as a result of the papermaking process.
Grain long, grain short: Terms used to indicate whether the paper web should travel through the paper machine lengthwise or widthwise, which in turn is generally indicated by marking whether the width or length of the paper should correspond with the machine's reel width. The fibers (and thus the grain) lie parallel to the edge not indicated.
Grammage: The standard international unit of measurement for paper weight, expressed in grams per square meter, or gsm. Grammages range from 7 to approx. 225 g/m2 for paper, and approx. 150 to 600 gsm for board. The system differs in the U.S., where the term "basis weight" is used, which is the weight in pounds of a ream (500 sheets) in the standard size for a grade of paper.
Gravure printing: A printing process used in high-output rotary presses, in which the printing elements take the form of small cells on the surface of the gravure form cylinder. The print image is generally transferred onto the cylinder by means of electromechanical engraving using a diamond stylus. During the course of the printing process, the printing cylinder is entirely coated in ink. A doctor blade then removes the excess ink from the surface and the only ink remaining is the ink in the cells. A rubber roller then presses the paper web against the printing cylinder and the ink remaining in the cells is applied to the paper.
Gravure printing paper: An especially soft, absorbent grade of paper, such as handmade papers from Japan with silky fibers especially suited to capture the nuances of hand-pressed copperplate prints.
Gray board: Flat substrate made of mostly uniform fiber layers over 225 g/m2 and colored gray.
Grid cells (screen cells): The combination of recorder elements (RELs) into a visual (halftone) dot. The physical size of the grid cell remains constant, and a computer program then defines the filling of the cell with picture elements or a pixel pattern in accordance with the color or gray value to be reproduced.
Griffo, Francesco (1450-1518): The Venetian die cutter known as the inventor of italic type. In February 1496, the letterpress printer Aldus Manutius published an essay by the Italian scholar Pietro Bembo. The italic type "Bembo", which was developed by Griffo from an official papal font, quickly gained in popularity and would later play an influential role in font design.
Gripper: The mechanical clamps used to transport the sheets in a sheetfed press. Grippers seize the individual sheets and feed them into the printing unit. The printing unit’s rollers are equipped with additional grippers, which fix the sheets in place for various stages of the print process. The printed sheets are output in a similar way at the end of the printing process.
Gripper fold: The protruding part of a folded signature, which can easily be gripped for production with inserts. The width of the gripper fold is in most cases approximately 8 millimeters, but must be accurately specified in accordance with postpress processes.
Gripper margin: The unprintable area of the page where the printing press grippers come in contact with the paper.
Grotesque face: Refers to fonts, the letters of which have a constant weight and are free of serifs. Examples of sans-serif fonts of this kind are Futura, Helvetica, Arial, Optima, Univers, Franklin Gothic and Frutiger. Grotesque faces are generally regarded as functional and modern, and are generally used for aesthetic reasons. From the point of view of legibility, they are less suitable for running text than serif typefaces.
Guilloches: Derived from the French guilloche (graver), term used for fine, interwoven geometric patterns of lines often printed on banknotes, certificates, etc., to make forgery more difficult. Guilloches are also often used as screen lines for illustrations, and works of art made of metal are not seldom decorated with guilloches engraved either by hand or machine.
Guillotine: Generic term for cutters designed for cutting sheets, stacks or blocks of paper in different shapes. A term mostly used in papermaking factories to describe the difference between this type of cutter and reel slitters.
Gutenberg (1397-1468): Born Johann Gensfleisch, son of Mainz patrician Friele Gensfleisch zur Laden, inventor of “printing with moving letters” or letterpress printing in either Mainz or Strasbourg. His invention was based on cast type, a corresponding manual casting instrument, a suitable metal alloy and a printing press. Gutenberg’s invention, which is today considered the trigger for one of the greatest revolutions in human history, spread throughout the world within a matter of years.

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