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SGIA

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.

| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | Y

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.

A-stage

An early stage in the reaction of a thermosetting resin where the material is still soluble in certain liquids and fusible, also reference B stage and C stage.

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.

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.

ACGIH

Acceptable acronym for American Conference of Governmental Industrial Hygienists.

achromatic color

A neutral color (white, gray, or black that has no hue).

achromatic color reproduction

Color separation technique whereby the neutral compound is digitally replaced by a corresponding level of black; also refer to gray component replacement.

achromatic lens

A lens corrected for black and white photography; specifically one that brings visual rays to the same focus.

acid

Any substance in an aqueous solution capable of turning litmus indicator red, dissolving certain metals to form salts, reacting with base or alkali to form salt, below 7 pH.

acid dye

Textile printing color containing salts of organic acids and used for applying color to protein fibers such as silk, wool and polyamides.

acid etching

Producing images by using acid and resist materials.

acid fixer (fix) (fixer) (fixing bath)

A chemical solution containing sodium thiosulfate and diluted acetic acid that renders photographic images on film or paper permanent, upon immersion for the prescribed time by removing unexposed silver halides; also refer to hypo.

acid free paper

A paper with no acidity or residual acid producing chemicals.

acid number

A measure of the amount of free acid on a molecule, calculated as the number of milligrams of potassium hydroxide required to neutralize the free acids in one gram.

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