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Specialty Graphic Imaging Association
SGIA Glossary

Definition Glossary

Sixth Edition

Language and our ideas about how it is interpreted change rapidly. The Specialty Graphic Imaging Association (SGIA) is aware of this and continues its effort to keep our constituents well informed about changes to the increasingly complex industry terminology. This publication represents the most recent changes.

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Any of a class of chemical compounds derived from hydrocarbon by replacing one or more of the hydrogen atoms with an equal number of hydroxyl radicals; a class of solvents that in addition to the hydrogen and carbon elements, also have oxygen, general formula C2H5OH.


A visual stair stepping of image edges caused by too low of a resolution for the size of the output.


The act of aligning or the condition of being aligned; in typesetting, denotes the exactly even relationship at the top or bottom of letters of a font; can also refer to the setting of lines of type, so that their ends appear even, refer to justify.

aliphatic hydrocarbon

Commonly known as paraffins; a group of petroleum naphtha solvents that are straight chain or open chain hydrocarbons, such as petroleum ether, pentane, hexane, cyclohexane, mineral spirits, Stoddard solvent, kerosene, V M & P, mineral spirits, and lacquer diluents.

aliphatic solvent

A straight-chain solvent derived from petroleum of low KB (Kauri Butanol) value such as mineral spirits and Stoddard solvent.


Any chemical that reacts on contact with an acid; capable of neutralizing acids; pH greater than 7.

alkali removable

Resist ink, which when dry, are removable by application of a caustic compound or alkaline solution.

alkali resistance

The relative ability to resist the action of alkalis.

alkali test

Used to evaluate the resistance of printed labels to alkalis.

alkaline dip

Term used for that step in stripping or removing of an alkali soluble resist when an etched circuit board is dipped and soaked in a high strength (6-10%) solution of a sodium hydroxide, softening the resist which is subsequently removed in a separate water rinse.


A group of synthetic resins formed by condensation of polybasic acids with polyhydric alcohols, modified with drying oils for printing ink manufacture.

alkyd plastic

Thermoset plastic based on resins composed principally of polymeric esters, where the recurring ester groups are an integral part of the main polymer chain, and where the ester groups occur in most cross links that may be present between chains.

all-over printing

The technique of covering the entire front and/or front and back of a garment with a printed image.


A chemical to which an individual may be, or become, abnormally sensitive.


The effect of a surface film contracting during drying to form small, irregular islands of color somewhat resembling the texture of alligator skin, also referred to as orange peel.


(1) The average percent change in resistance per degree of a pure metal resistance device between 0 degrees and 100 degrees Centigrade, which is usually designated by the Greek letter A or a, with units of ohm/ohm/C; (2) The mask channel in a color system.

alpha blending

Ability to specify a fourth color component in addition to RGB, used to specify opacity, from completely transparent to opaque.

alpha channel

An eight-bit grayscale channel found in some graphics applications or the last eight bits in a 32-bit color scan. (The first 24 bits describe the color of objects. Alpha channels permit layering of images. Some uses include masking objects, making them transparent, or adding specific color instructions).

alphabet length

The space required for the letters of the alphabet in a particular type font.

alphabet sheet

Sheet containing fonts of letters that may be removed and relocated to form words and/or lines of copy. (They are either on transparent material having a pressure sensitive adhesive back, or the letters are printed on the back of the sheet and adhered to the new substrate by burnishing).


Consisting of alphabetic and numerical symbols; a device or system that includes letters and numbers.


A change made to an image element, color, or page layout through computer manipulation.


Change in copy or specification made after production has begun.

alternating current (AC)

Electric current that periodically reverses the direction of electron flow.

alternative method

Within the meaning of the Clean Air Act (US), any method of sampling and/or analyzing for an air pollutant, which is not a reference (or equivalent) method, but which has been demonstrated to produce results adequate for the determination of compliance with the Act.


Any of several forms of aluminum oxide used as an abrasive and in marking glass, enamel, and refractories.

alumina hydrate

A white inorganic pigment used as an extender in inks and noted for its transparency.

aluminum bronze

Finely pulverized aluminum in very small flake form suitable for mixing with a varnish type or lacquer type vehicle for use in screen printing metallic effects.

aluminum ink

A printing ink whose principal pigment consists of aluminum, finely pulverized into flaky particles, and when printed gives a silver color appearance; also referred to as silver ink.

aluminum stearate (oxide)

A principal thickening agent used in many screen printing inks and transparent extender bases.


Acceptable abbreviation for amalgam.


Surrounding environmental conditions such as pressure, temperature, or humidity; environment coming into contact with a system or component.

ambient compensation

The design of an instrument such that changes in ambient temperature do not affect the reading.

ambient temperature

Temperature of the immediately surrounding air volume.

American National Standards Institute (ANSI)

A standards setting agency of the United States that approves design and performance of electrical/electronic components (USA), formerly the American Standard Association.