Galley Proof:

Proof of type from any Source, whether metal type or photo type. Also called checker and slip proof.

Gamma:

A measure of contrast in photographic images. A densimetric evaluation of graph paper indicating highlight to shadow contrast in terms of density values, plotted on a graph to establish the maximum and the minimum, the difference between them being the gamma.

Gamma Correction:

Compressing or expanding the ranges of dark or light shades in an image.

Gamut (Color Gamut):

The entire range of perceived color that may be obtained under specified conditions. The total range of colors reproduced by a device. A color is said to be "out of gamut" when its position in one device's color space cannot be directly translated into another device's color space. For example, the total range of colors that can be reproduced with ink on coated paper is greater than that for uncoated newsprint, so the total gamut for uncoated newsprint is said to be smaller than the gamut for coated stock. A typical CMYK gamut is generally smaller than a typical RGB gamut. The range of different colors that can be interpreted by a color model or generated by a specific device.

Gamut Compression/Tonal Range Compression:

The color space coordinates of a color space with a larger gamut are reduced to accommodate the smaller gamut of a destination color space. For example, the gamut of photographic film is compressed for representation in the smaller CMYK gamut used for four-color process printing.

Gamut Mapping:

Converting the coordinates of two or more color spaces into a common color space. Often results in tonal range compression.

Gang:

(1) To halftone or separate more than one image in only one exposure. (2) A grouping of forms arranged to print together with a single impression. Also known as gang printing, gang run, or gang up.

Gas Chromatograph (GC):

An analytical instrument that can determine with great accuracy the presence and composition of volatile materials. It can determine their residual presence in printed materials such as paper, board, foil or film.

Gassing:

The evolution of gases from one or more of the electrodes during electrolysis.

Gate Fold:

A four-page insert to a book that is larger than the existing page dimensions, having a fold at the outer edge that serves as a hinge, allowing two sheets to fold out from the center to the edge. Also known as a foldout.

Gathered:

Signatures assembled next to each other in the proper sequence for binding, as compared to nested. Also called stacked.

GCR (Gray Component Replacement):

  Using black ink to replace cyan, magenta, and yellow inks. The black replaces neutral color values of the three colored inks throughout an image. The amount of black replacement is usually defined as a percentage GCR.

Gear Marks:

A defect in flexographic printing. Usually appears as uniformly spaced, lateral variations in tone exactly correspondng to the distance between gear teeth. Also called "gear steraks."

Gel:

A state or condition in which an ink or vehicle has a jelly-like consistency.

Gelatin:

A hard, colloidal protein, an animal byproduct (mostly from bone). Dissolves in hot water, but is insoluble in alcohol and some other solvents. Used as a coating for carbon tissue and other photographic products. Also spelled gelatine.

Generation:

Each succeeding stage in the reproduction from the original copy.

Ghost Halftone:

Normal halftone whose density has been reduced to produce a very faint image.

Ghosting:

Presence of a faint image of a design, appearing in areas not intended to receive that portion of the image.

Gloss:

The ability of a paper stock to reflect light from its surface. Gloss quality is measured by instruments that evaluate light reflected at specific angles.

Gloss Ink:

An ink that dries with a minimum of penetration into the stock and yields a high luster. For highest gloss in the finished product, paper of the highest resistance to penetration of the vehicle should be used. A combination of lead and cobalt is commonly used as a drier, giving good gloss and drying speed.

Gloss Meter:

An instrument used to measure the specular (mirror) reflectance from a surface at a given angle.

Gradation:

In photographic originals and lithographic reproductions, the range of tones from the brightest highlights to the deepest shadows.

Grade:

General term used to distinguish between or among printing papers, but whose specific meaning depends on context. Grade can refer to the category, class, rating, finish or brand of paper.

Graduated Screen Tint:

Screen tint that changes densities gradually and smoothly, not in distinct steps. Also called degrade, gradient, ramped screen and vignette.

Grain Direction:

1. The alignment of pulp fibers in the direction of web travel during the production of paper. 2. “Grain-long” is the grain direction paralleling the longer dimension of the sheet. “Grain-short” paper has fibers paralleling the short dimension of the sheet. 3. In the production of bound materials, the grain direction of all papers used must run parallel to the backbone to prevent cracking and insure a durable spline.

Grain Long Paper:

Paper whose fibers run parallel to the long dimension of the sheet. Also called long grain paper and narrow web paper.

Grain Short Paper:

Paper whose fibers run parallel to the short dimension of the sheet. Also called short grain paper and wide web paper.

Grammage:

Basis weight of paper in grams per square meter (gsm).

Graphic Arts:

The crafts, industries and professions related to designing and printing on paper and other substrates.

Graphic Design:

Arrangement of type and visual elements along with specifications for paper, ink colors and printing processes that, when combined, convey a visual message.

Graphics:

Visual elements that supplement type to make printed messages more clear or interesting.

Gravimetric Analysis:

A method of analysis consisting of quantitatively separating a desired constituent in the original sample.

Gravure Ink:

These inks must have sufficient body to be retained in the recesses of the intaglio plate but must be pulled from the recesses onto the paper as it passes. Gravure inks must be free of hard particles, which would scratch the engraved cylinder or plate. The consistency of the ink must be such that the doctor blade stays clean for proper printing.

Gravure Printing:

An intaglio process of rotary printing from tiny etched cells in a copper- or zinc- covered roller surface. Often over-chromed for longer wear. Does fine printing, along with halftones and gradation of tone. Uses solvent-type, fast-drying inks and water-based inks. Also known as Rotogravure Printing.

Gravure Process Optimization:

An analysis of the steps in gravure printing in order to develop the best practices for completing the process.

Gravurescope:

A type of microscope designed for inspecting etched or engraved cells on a gravure cylinder. Used to measure depth and width of cells and cell walls.

Gray Balance:

Printed cyan, magenta and yellow halftone dots that accurately, reproduce a neutral gray image.

Gray Component Replacement (GCR):

A technique for removing some or all of the cyan, magenta and yellow from color separations. If properly executed, the reproduction will appear the same or better than one that used conventional color reproduction without GCR.

Grayscale:

The spectrum, or range, of shades of black an image has. Scanners' and terminals' grayscales are determined by the number of gray shades, or steps, they can recognize and reproduce. A scanner that can only see a gray scale of 16 will not produce as accurate an image as one that distinguishes a gray scale of 256.

Gray Value:

The number (usually between 0 and 256) that specifies a particular shade of gray.

Greasing:

The adhesion of ink to the non-printing areas of a lithographic plate. Also known as Scumming.

Grind Edge:

Alternate term for binding edge when referring to perfect bound products.

Grindoff:

Approximately 1/8 inch (3 mm) along the spine that is ground off gathered signatures before perfect binding.

Gripper Edge:

Edge of a sheet held by grippers on a sheetfed press, thus going first through the press. Also called feeding edge and leading edge.

Gripper Margin:

The unprintable, blank edge on which the paper is gripped as it passes through a printing press—usually measures a half-inch or less.

Grippers:

The metal fingers on a printing press that hold the paper as it passes through the press.

Groundwood, Uncoated:

Paper other than newsprint made with large portions of mechanical pulp.

Groundwood Papers:

A general term applied to a variety of papers made with substantial proportions of mechanical wood pulp together with bleached or unbleached chemical wood pulps (generally sulfite), or a combination of these, and used mainly for printing and converting purposes.

Grooving the Cylinder:

Cylinder damage due to foreign material.

GSM:

The unit of measurement for paper weight (grams per square meter).

Gutter:

The two inner margins of the facing pages of a publication.