Glossary Of Terms

The SGIA Glossary of Terms serves as an excellent industry terminology resource. It is the language by which we all communicate, without it universal understanding would be impossible. Language and our ideas about how it is interpreted change rapidly. SGIA is aware of this and continues its effort to keep our constituents well informed about changes to the increasingly complex industry terminology. The definitions are for general reference only. Usage may vary between companies, individuals, or national and country customs. The information presented is as accurate as the authors and editors can ascertain and SGIA assumes no responsibility for the use of information presented herein.


  • Aberration
    (1) A disturbance in color that interfere with clarity, typically one of the faults found in interpolated colors; (2) Errors in a photographic lens which prevent the lens from producing a single focus of all intensities of the light rays reflected from the subject, resulting in poor image definition at the film plane.
  • Abherent
    A substance that prevents adhesion of a material, either to itself or to other materials; a release agent, such as silicone or wax.
  • A-board
    A double-faced sign with each face mounted on a frame so that the two, with tops lined together and bottom held in separated position with a brace, form an "A" when viewed from the side.
  • Abrasion resistance (rub fastness)
    The inherent ability of a surface to inhibit deterioration or destruction by friction, also referred to as rub resistance.
  • Abrasiveness
    The tendency of a material or coating to abrade or wear away a surface or an edge.
  • Abscissa axis
    The x coordinate.
  • Absolute humidity
    The actual weight of water vapor contained in a unit weight of air, expressed in grams per cubic meter.
  • Absolute register
    High degree of exact size conformity of all image elements with the original or with position on the substrate.
  • Absolute viscosity
    A characteristic of one-component liquids which have a constant ratio of shear stress over shear rate (constant viscosity).
  • Absolute white
    In theory a material that perfectly reflects all light energy at every visible wavelength; in practice a solid white with known spectral data that is used as the "reference white" for all measurements of absolute reflectance. (When calibrating a spectrophotometer, often a white ceramic plaque is measured and used as the absolute white reference).
  • Absorbance
    An index of the light absorbed by a medium compared to the light transmitted through it; numerically, it is the logarithm of the ratio of incident spectral irradiance to the transmitted spectral irradiance, a unit-less number. (Absorbance implies monochromatic radiation, although it is sometimes used as an average applied over a specified wavelength range).
  • Absorbency
    That property of a porous material such as paper that causes it to take up liquids or vapors (e.g., moisture) with which it is in contact, allowing penetration into its bulk.
  • Accelerate
    To hasten the natural progress of an event or a series of events such as the addition of a faster drying solvent or increasing the temperature or volume of air to dry the printed surface.
  • Accelerated aging/weathering
    Laboratory test methodology that simulates long term environmental effects, but at the same time intensify and accelerate the destructive action of natural weathering in an attempt to produce changes in the material similar to those observed after continuous outdoor exposure. (Test involves exposure to artificially produced components of natural weather, light, heat, cold, water vapor, and rain which are controlled and repeated in a given cycle).
  • Accelerator
    (1) A substance added, or method used, to hasten the natural progress or process of an event or series of events, such as ink drying; (2) Material that when mixed with a catalyzed resin, will speed up the chemical reaction between the catalyst and resin, either in polymerizing of resin or vulcanization of rubber; also referred to as a promoter.
  • Acceptable Quality Level (AQL)
    The maximum number of defects per one hundred units that can be considered to be satisfactory as a process average.
  • Acceptance sampling
    The evaluation of a definite lot of material or printed product to determine its acceptability within quality standards.
  • Accessory
    Supplementary part or equipment, something nonessential but useful.
  • Accordion fold
    A series of parallel folds where each fold opens in the opposite direction from the previous fold like the bellows of an accordion.
  • Accurate
    Without error, precise, exactness to a specific degree or size, true to given dimensions.
  • Acetal (acetal plastic) (POM)
    A highly crystalline thermoplastic resin polymerized from formaldehyde that is formed from combining aldehydes and alcohol; generic name of polyoxymethylene.
  • Acetate
    (1) A plastic synthesized from acetic acid that exhibits rigidity, dimensional stability, and ink receptivity; made from cellulose acetate or its derivatives such as the clear plastic covering placed over artwork; (2) A family of solvents, also known as esters.
  • Acetate butyrate
    An extruded thermoplastic that can be decorated and heat-formed.
  • Acetic acid
    An organic acid used in testing acid resistance of a material; photographic, the active ingredient in stop bath or fixing baths.
  • Acetone
    Colorless, highly flammable chemical compound (CH3)2CO used as an organic solvent, an ingredient in many lacquer thinner compounds and adhering liquids; used to remove lacquer adhered knife-cut stencils and lacquer type blockout from screen fabrics.